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1. Bible--Elisha (II Kings 4:34) restored the life of a child demonstrating respiration was necessary for life. "And he put his mouth upon his mouth... and the flesh of the child became warm"

2. Pythagoras-- (580-489 BC) named the four basic elements, earth, fire, water and air.

3. Hippocrates-- (460-370 BC) The father of medicine discovered the "essential humors." All diseases were humoral disorders within the body.

4. Aristotle (384-322 BC)--recorded the first scientific experiment in Respiratory physiology. He placed animals in an airtight chamber where they soon died. He incorrectly assumed their death was due to the inability to cool themselves.

5. Galen (131-201 AD)--hypothesized that "pneuma" was a spirit that penetrated all parts of the body.

6. Leonardo da Vinci (1452-1519)--dissected major anatomical structures of the body. He noted that animals couldn't live in an atmosphere that couldn't support flame. Also fire seemed to consume this atmosphere.

7, Andreas Vesalius (1542)--passed a reed into the trachea of an animal whose thorax had been opened and blew intermittently into the reed. The lungs expanded and the heart recovered its normal pulsation. He also discovered that if the lungs were allowed to collapse, pulsation ceased, and the heart beat in a worm like fashion. He performed the first tracheotomy and witnessed ventricular fibrillation.

8. Servetus (1509-1553)--He discovered that pulmonary blood flow traveled to the lungs to get air and then returned to the heart.

9. William Harvey (1578-1657)--by meticulous dissection proved that the heart acts as a muscular pump propelling blood continually and cyclically to the lungs and tissues. Precursor to CP Bypass.

10. Robert Boyle (1666)--produced an air embolism in animals exposed to low 02 tension and formulated Boyle's law.

11. Joseph Priestly (1774) discovered combustion. He produced 02 by heating mercuric oxide and carbon dioxide by heating lime. He tried breathing 02 and noted that his respiration's were light and easy for some time after. He stated "Who can tell that in time this pure air may become a fashionable luxery.11

12. Antoine Lavoiser (1775-1794)--laid down the fundamental principles of respiration and gas exchange, as we know them today. I.e. that 02 is absorbed from the lungs, C02 and H20 are exhaled and that nitrogen (the inert substance in air) is unchanged.

13. Thomas Beddos (1800)--established the Pneumatic Institute in England. He uses 02 therapeutically in heart disease, asthma and opium poisoning.

14. Rene Laennec (1781-1826)--French physician who invented the stethoscope and is considered the father of chest medicine. He wrote many articles on bronchitis, pneumonia, pleurisy, emphysema, TB and heart diseases.

15. John Dalton (1776-1844)--Founder of the modern atomic theory, he formulated the law of partial pressures.

16. Henry Hill Hickman (1800-1829)--A pioneer in anesthesia, he was interested in decreasing pain during operations. He found he could render animals insensible by having them inhale C02 during operations.

17. Heinrich Gustav Maanus (1802-1870)--the inventor of the blood gas analyzer, by which he found that arterial blood contained more 02 than venous and venous blood contained more C02 than arterial.

18. John S. Haldane (1860-1931)--Respiratory physiologist who discovered that the regulation of breathing is determined by the C02 levels effecting the respiratory centers of the brain. He led an expedition to Pike's Pike to study the effects of low barometric pressure.

19. Lawrence J.Henderson (1878-1942)--His monograph "Blood" first described the physiology/chemistry of blood including the Henderson equation.

20. Sir Joseph Barcroft (1872-1947)_--He lived for five days in a 15% 02 atmosphere to study the effects of diminished 02 tension. He experienced nausea, headaches, visual disturbance, rapid pulse and lassitude.

21. Christian Bohr (1855-1911)--The first to establish the Sigmiodal shape of the Oxyhemoglobin dissociation curve and that C02 drives 02 out of the lungs.

22. Leonard Hill (1916, 1921)--constructed the first 02 tent

23.Alvin Barach (1934)--first used helium therapeutically.

24.Boothby, Lovelace and Bulbulian (1938)--designed the first high concentration 02 mask to prevent decompression sickness for pilots.

Hypoxias and Hypoxemia

1. Hypoxia-inadequate availability of 02 for cellular function.

2. Hyperemia- diminution of the actual 02 content of the blood implies tissue Hypoxia-used interchangeably clinically.

Gas Physics

The three states of matter are solid, liquid and gas.

The state of matter of a substance depends largely upon its kinetic activity (motion of molecules). The degree of motion is most dependent upon the temperature of the molecules.

Concept--The higher the temperature the molecules achieve, the faster they move and the more inclined they are to change states of matter.

Absolute Zero-- developed by Lord Kelvin, this is the temperature at which all molecules have come to a complete rest, and i.e. there is no kinetic activity. Conversion of oC (Centigrade) to oK (Kelvin) oK=oC += 273

Melting Point-The temperature at which the transition occurs from a solid to a liquid state.

Freezing Point-- the same temperature as the melting point but the substance is changing form a liquid to a solid.

Boiling Point-- the temperature at which a liquid changes to a gas at 1 ATM of pressure.

Sublimation substance converts directly from a solid to a gas below the melting point, i.e. the liquid state is bypassed. Example-Solid C02-dry ice

Evaporation substance converts directly form a liquid to a gas below the boiling point, Clinical examples-simple humidifiers.

Concept-The higher a liquid's temperature, the more force is exerted when the molecules hit the liquid's surface, the more likely the molecules are likely to escape, i.e. increased Vapor Pressure.

If the liquid is kept in a closed container, the forces of molecules trying to escape the liquid will reach an equilibrium with H20 vapor pressure, and no more liquid molecules will escape, The solution is saturated.

Critical Temperature-- the temperature ABOVE which gas cannot be converted to a liquid at any applied pressure.

Critical Pressure-- the pressure required to convert a gas back into a liquid at its critical temperature.

Alternative Way to say it-- As the temperature of a substance rises above its boiling point towards its critical temperature, the pressure necessary to change it back to a liquid increases proportionally. When the gas passes its critical temperature, no amount of pressure is sufficient to convert it back to a liquid.

Characteristics of a Ideal Gas

1. The space between molecules is large compared to their diameter, i.e. the distance between molecule is 300x >=their diameter. 2. Gas molecules are in constant and random motion. 3. Molecular collisions are completely elastic in nature; i.e. there is no loss/gain in force.

4. Kinetic Energy is directly proportional to the temperature of the molecules (oK). 5. Molecules do not attract or repel each other, they travel around freely.

Gas Pressure Measurement

Gas Pressure-- the force of gas molecules hitting objects Apparatus used to measure gas pressure-- Mercury and Aneroid Barometer

Mercury Barometer-uses the weight of the column of mercury to equilibrate with the kinetic force of molecules hitting the surface of the mercury reservoir.

Aneroid Barometers-When there is increased gas pressure, the box is force to contract, the spring is pulled down causing the lever to pivot and the indicator moves to a higher value on the pressure scale. The box is a vacuum.

Bourdon Gauge-- is used in clinical measurement of gas pressure. An increased in gas pressure is transmitted up the coiled flattened tube. It tends to straighten (rise), as the surface area on the outer side of the tube is larger than the inside. This causes the gearing mechanism to rotate the indicator to a higher point on the pressure gauge.

Pressure measurements important in Respiratory Care 1.36 cwp (centimeters of water pressure)=l mm Hg Clinical examples-cwp used for ventilators vs. mm Hg used for blood pressure, Tracheal necrosis due to high ETT cuff pressures.

Ex. Problems 20 mm Hg x 1.36 cwp/mm Hg=27.2 cwp

27.2 cwp: - 1.36 cwp/mm Hg=20 mm Hg

The Gas Laws

Boyle's Law (1660)

Concept to Review-- Inversely related vs. directly related

Cross Multiplying

If absolute temnera4fture and mass remain constant, the volume of

Gas varies inversely with the pressure.

PV=K (constant) SO PlVl=p2V2

Clinical Examples-- Tubing Compliance Factors, Gas Conversion factors for cylinders, Body Box

Charles's Law (1778)-

If the pressure and mass remain constant, the volume of the gas varies directly with changes in absolute (Kelvin) temperature. V/T=K or V-1=V2

Tj=T2

To change from oC to oK oC +273=oK To change from OF to OR (Rankine) OF +460= OR

Gay-Lussac's Law (1809)

If the volume and mass remain constant, - the pressure exerted by the gas varies directly the absolute (Kelvin) temperature. P/T=K or P, = P2

T, T2

Universal Gas Law-- Remember with Give Chip a Boat

Or P(C) V (G) P1V1 = P2V2

T1 T2

T (B)

Survival Steps for solving the Gas Law problems 1. Figure out which gas law this problem involves and what the unknown is. 2. Set the problem up using letters only. 3. If this problem involves temperatures, convert Temps to absolute or Rankine scale. 4. Substitute in P's, V's and T's with the correct numbers and use the units too. 5. Multiply the numerator; multiply the denominator and divide. 6. If your answer is a temp, convert back to oC or oF. 7. Examine your answer to see if it's reasonable.

Dalton's Law of Partial Pressures

1. The total pressure of a gaseous mixture is equal to the sum of the partial pressures of the constituent gases. (The whole is equal to the sum of the parts) 2. The partial pressure of each gas in the mixture is the pressure it would exert if it occupied the entire volume alone. 3. The partial pressure exerted by each constituent gas is proportional to its volumetric % of the mixture.

Symbol for Partial Pressure is Pp Clinical examples are Pa02

PA02 PaC02 ' alveolar air equation

760 mm Hg (1 ATM) x .2095= 159 m Hg at sea level

Diffusion-- intermolecular mingling that occurs as a result of molecules randomly bouncing off each other. This produces a homogeneous mixture and occurs due to the ideal gas laws.

Fick's Law-- The rate of diffusion of gases in a gaseous medium is proportional to the gradient of their concentration, i.e. the higher the concentration gradient from one area to another, the faster the gas will diffuse. Clinical examples-- diffusion of C02 through tent canopies

Graham's Law-- The rate of diffusion of a gas is inversely proportional to the square root of its density or gmw.

i. e. The lower the density of the gas, the more diffusable it is. Clinical Exs-- He vs. 02.

Density-- mass/volume or weight/volume

Mass-- the quantity of matter a substance contains.

Weight-- the gravitational pull of the earth on a body

Density units= Gms/cc Is (solid or liquid)

= gms/L (gases)

Moles-- All matter is composed of atoms. A molecule is the smallest particle of a substance that retains all of its properties. 1 gram atomic weight = 1 gram molecular weight = 1 gram formula weight (ionic compounds)= I mole-- any quantity of matter the contains 6.02 X 102' atoms

Henry's Law-- The weight of gas dissolving in a liquid at any given temperature is proportional to the Pp of the gas, i.e. the higher the Pp of a gas, the more it will dissolve. Clinical EXs-02 in blood.

Solubility coefficient measurement of the quantity of gas that will dissolve per ml/mm Hg into a liquid.

SC 02=.023 ml/ml plasma at 370 C, 760 mm Hg

SC C02= .510 ml ...........

The diffusion of a gas into a liquid medium (i.e. the diffusion of gases into the perfused lung) is directly proportional to the solubility coefficient of the gas and inversely proportional to the square root of its density or gmw.

Translation SC of C02 is>= SC of 02

Density of C02 is >= density of 02 Add these two factors together=C02 is 19X more diffusable into as liquid medium than 02 because it SC is so much Greater.

CLINICAL SIGNIFIGANCE--Co2 can always diffuse into the blood at the alveolar-capillary membrane and get out of the lungs, but 02 has a much more difficult time leaving the alveoli to get into the capillaries.

Gas Flow-- Flow is = Volume/time. Units of flow commonly used are L/sec or L/min. Gas flows from an area of high pressure to an area of low pressure due to the gradient.

Bernoulli's Principle-- As gas flow meets a narrowing or restriction, the molecules speed up with increasing forward velocity so that the same number can get through in a given amount of time. As a result the molecules hit the sides of the tube less frequently, therefore there is a drop of lateral pressure. This drop in lateral pressure causing a vacuum or sucking action that can be used to entrain (bring in) additional air or fluid.

Jet-- This devise is commonly found in many types of RC equipment and is a simple application of Bernoulli's principle. We can entrain air in for increased flow used in Venturi Masks or Ventilators, or we can entrain water in as used in nebulizers.

Factors that affect the degrees of fluid or air entrainment by a Jet--1. jet orifice size-- The smaller the orifice, increased forward velocity, decreased lateral pressure, increased air entrained, decreased FI02.

2. the size of the entrainment port--the larger the port size the greater the amount of air can be entrained, decreased FI02.

Venturi Principle--The addition of a tube gradually increasing in diameter (<= 150) in the direction of flow from the jet orifice will restore the lateral pressure of the gas toward prerestriction pressure. This is critical in devises such as ventilators.

Avogadro's Law--Equal volumes of gases at the same pressure

ATM, 760 mm Hg) and temperature (2730K or OOC) contain the same number of molecules=6.02 X 1021 molecules of gas /gmw at STPD

Remember 1 gmw = l Mole = mw of substance x 1 gm

Ex. 02=32 (mw) x 1 gm=32g

Part 2--At STPD (Standard Temperature, Pressure Dry), 1 gmw of a gas occupies 22.4 L

Recall Density = mass/volume. In order to compare different gases we examine their mass at equal volumes or density =gmw/22.4L. Ex. 02 has greater density than He does.

Specific gravity--Comparison of gas densities Ex.

Spec g 02=Density 02/Density Air=1.12 In other words 02 is heavier than Room air, therefore when analyze 02, we always place the sensor as close to the patient as possible.

Viscosity--The thickness of a gas or fluid which is determined by 1. density (increased density, increased viscosity) and 2. frictional resistance (water has decreased frictional resistance vs. blood in the body) 3.temperature (increased temp, decreased viscosity Ex. molasses in winter vs., summer)

Clinical Ex.--Congestive Heart Failure (CHF)-decreased muscular pumping ability in the Left Ventricle (LV) leads to increased viscosity of blood left in the ventricle after systole. This thickened blood is much more difficult for the heart to pump out of the LV resulting in poorer perfusion to the extremities leading to tissue hypoxia. We call this Cardiogenic hypoxia. As the heart has to keep working harder and harder this leads to more CHF.

Poiseuille's Law--The resistance or pressure gradient to fluid flow through a tube is directly proportional to the length, flow and viscosity and inversely proportional to the radius to the fourth power.

P=V'81n/r 4 Simplified P=V'/r 4

Clinical Ex's. 1. If flow decreases (V), pressure decreases as they are directly related. Ex. trauma 2. If r decreases to 1/2 its previous value, pressure will increase to the fourth power or 16X. Asthma and other obstructive airway diseases.

Reynold's Number = Critical Velocity (cm/sec) x Diameter (cm) x Density (gm/cm')/ Viscosity (Poise). If # <=2000 Laminar Flow If #>= Turbulent Flow Laminar Flow requires far less pressure and resistance than turbulent flow does to move gas through the airways. Critical Concept in Obstructive Airway diseases. Airways that are making the transition from laminar to turbulent flow are said to have transitional flow.

Abbreviations

STPD (Standard Temperature, Pressure Dry)--volume of dry gas with water vapor removed, at O'C, 1 ATM or 760 MM Hg)

BTPS (Body Temperature, Pressure Saturated)--Volume of gas with

water vapor present, 370 C, ambient environmental pressure.

Clinical Exs. PFT's conversion factor

ABG's

Absolute Humidity--the maximum content or actual weight of water in the air in a given volume at a specific temperature.

Relative Humidity-- actual amount of water in the air/ the maximal amount of water in the air that could be held at this temperature.

Content/Capacity RH is measured with a hygrometer

See Problems-- CLINICAL SIGNIFIGANCE--Every piece of RC equipment the we use to give the patient humidity we rate according to its RH.

Part II-Gas Therapy, Regulators and Flowmeters

Regulating Agencies--federal, state and local bodies with the right to regulate (i.e. pass laws). These agencies often use standards prepared by recommending bodies. An example would be a local county government that adopts standards for the storage of bulk 02 established by the National Fire Protection Association.

Recommending Agencies--individuals with technical knowledge that recommend standards for equipment or products. For example, the compressed Gas Association made up of equipment, container and valve manufacturers recommends the conditions and ways their products should be used.

Examples of Regulating Bodies

1. The ICC--regulated the construction, transportation and testing of compressed gas cylinders 1948-1970. (ICC= Interstate Commerce Commission). The DOT (Department of Transportation) took over this job in 1970 and continues to do it.

2. The Department of Health and Human Services (HHS)--A division of this that effects our practice is the FDA (Food and Drug Administration). The FDA regulates the purity of medical gases. The Bureau of Medical Devises (est., 1976) sets the standards for medical devises so that they can be safety sold on the market.

3. OSHA (Occupational Safety and Health Administration)--is a division of the Department of Labor, which regulates safety in the workplace. Occupational lung diseases are a major cause of disability in this country.

4. US Pharmacopoeia-- a very long series of books containing all the drugs currently available in this country, their strengths, purity and directions for making them. All nations have this type of body. Every five years in the US , MD's, pharmacists and other scientists meet to revise this work. It is the legal standard for drugs in US (National Food and Drug Act, 1907). In the hospital, we use the PDR (Physicians' Desk Reference) to look up questions about drugs.

Examples of Recommending Bodies

1. Compressed Gas Association (CGA)

2. National Fire Protection Association (NFPA)-sets the standards for the storage of all flammable and oxidizing gases.

3. Z-79 of ANSI (American National Standards Institute)- This committee, the Anesthesia and Ventilatory Standards group reviews and evaluates all anesthesia and respiratory care equipment on the market.

Medical Gases--three categories

1. Laboratory Gases which have limited therapeutic use and are non-flammable (i.e. will not burn). Examples include C02,, He and N2.

2. Therapeutic Gases-all these gases support combustion.(i.e., they will feed a fire once it is going). Examples include Room Air (N2-02), Helox (He-02), Carbogen (C02-02) and 02.

3. Anesthetics-These gases are uses to put the patient to sleep. Cyclopropane ( (cH2) 3) and Ethylene (C2H4) are f flammable while N20 (Nitrous oxide) supports combustion.

Cylinder Markings

1. ICC or DOT

2. 3A or 3AA-type of steel they are made of. 3A is high carbon or medium manganese steel. 3AA is chrome-molybdenum heat-treated steel, a superior quality to 3A. Spun or CR-Mo are abbreviations that mean 3AA.

0C 3. Maximum Working Pressure or Service Pressure--this is the filling pressure that can be exceeded legally by 10% by the manufacturer. It is read in PSIG (pounds per square inch gauge).

4. Cylinder Size and serial number--Cylinders are given a letter designation according to their size. A-E are the smaller cylinders most often used as anesthetic gases or portable 02 supply. They use a yoke regulator named the PISS. F-K are the larger cylinders used as part of the bulk delivery systems of hospitals. They use the ASS with a threaded outlet.

5. Company that owns and/or manufactures the cylinder, inspecting authority--It may be almost impossible to distinguish the manufacturer from the owner or they may be one in the same. Inspectors each have their own brand.

6.the I original safety test (hydrostatic) date and subsequent retests. Every 5-10 years, the DOT requires that each cylinder be tested for leaks, expansion and wall stress. They are inspected internally and cleaned. Some cylinders have "ee' on them meaning elastic expansion. We heat/cool the cylinder to certain temperatures and see how many cc's they expand/contract.

7. the label identifying the contents and the concentration of the medical gas --THIS IS CRITICAL, because many cylinders are color coded. DON'T TRUST THE COLOR AS MANY CYLINDERS ARE REPAINTED!

Always read the label.

Colors 02-green C02-gray He-brown Ethylene-red N20-light blue Cyclopropane-orange N2-yellow or black Mixtures contain all the colors of the gases ex. Co2-02 would be Gray-green or He-02 would be brown- green. Important--The international color for 02 is WHITE.

CYLINDER VALVES-two types

1. Direct Acting-this is a sophisticated needle valve with two washers and Teflon packing to prevent leaks. It is capable of withstanding high pressures (>= 1500 psig) therefore cylinders holding only gases such as 02, He use this valve.

2. Diaphragm--here the stem is separated from the valve seat by a spring and two diaphragms. As the valve seat does not turn, there is no metal scoring therefore no leaks. It is used for low-pressure gases (<= 1500 psig) with a vapor phase such as the flammable anesthetics or C02.

Measuring Cylinder Contents and Estimation Duration of Flow

At room temperature, cylinder pressures for vaporous gases are higher than for liquid gases. The pressure in a vapor gas cylinder represents the force required to squeeze a given volume of gas into the cylinder. The pressure in a liquid gas cylinder is the vapor pressure of the gas over the surface of a given weight of liquid poured into a closed container.

If we look at the regulators that measure pressure in psig in each cylinder, we see that in gas cylinders the volume of gas left in the cylinder is constantly decreasing as is the pressure.

If we look at liquid gas cylinders, we see that for a long time the pressure in the cylinder does not change even as the gas is being used up. This is because the liquid gas is being converted constantly to vapor gas so that the regulator pressure remains the same. Only when the liquid gas is gone does the regulator pressure begin to decrease constantly as it did with the vapor gas.

Clinical importance--02 vs. C02 Remember that whether a gas is a vapor or liquid at room temperature is dependent on its critical temperature and pressure. Beware a fault sense of security with liquid gases.

Commercial gas cylinders have calibrations recorded in the English system (psig), but once the therapeutic gases leave the regulator flow (liters per minute, liters per second) is measured in the metric system. In order to figure out duration of flow for each cylinder, we use a fudge factor.

Fudge factor = cubic ft of gas in a full cylinder x factor to convert ft3 to liters/ pressure of full cylinder in psig

The factors are 3 for an H cylinder and .3 (actually .28) for an E cylinder.

Duration of flow in minutes = Psig x Factor (3 Or .3.)

liters per minute going to the patient

See McPherson and work sheet for practice problems.

Remember, this is a clinical estimate only as long as the patient remains stable. What happens if the patient decides to code!

What to tell the nurse--When the pressure gauge reads 500, call me.

Bulk 02 systems--Any system that has 12,000 ft3 of gas ready for use or 25,000 ft3 of gas in unconnected reserves. A Central Supply or Piped In system means there's an 02 outlet at each patient bedside. Pressure reduction to 50 psig is accomplished at a central station, and then 02 is pumped to each clinical area. This is obviously much easier that changing tanks all the time.

Gaseous Bulk 02 systems--Standard H cylinders tied together by a manifold which converts individual units into 1 continuous supply. The Manifold mechanism has a pressure reducing valve, a check valve to prevent back flow, a flow control and a alarm system to warn of malfunction or depletion. These gaseous bulk 02 systems can be either permanently fixed cylinders or trailer units.

Liquid Bulk 02 Systems--This is the most economical way of transporting and storing 02. Liquid 02 Critical Temp -181.1 OF Boiling point -297.3 OF i.e., liquid 02 must be kept below these temperatures. I ft3 02= 860.6 ft3 gaseous 02 at ambient temperature and pressure. To prevent liquid from converting to gas both supply trucks and hospital stations are designed like large thermos bottles. They are two layers of steel with a vacuum between them. The vacuum prevents the transfer of heat. The two types of liquid Bulk Systems are 1. liquid cylinders connected with a manifold or 2, a fixed station thermos bottle with 130,000-ft3 capacity. Liquid is converted to a gas using a heating unit called a vaporizer.

Review facts we already know about 02--% gas in air,

abbreviations, regulations, physical characteristics etc.

Steps for the Commercial Fractional Distillation of 02

1. Air is dried and filtered of debris via scrubbers then cooled near freezing to remove water vapor.

2. Air is compressed to 200 ATM (increased pressure, increased temperature-Gay Lussac's Law)

3. The compressed gas is cooled to room temperature. The compressed air is then expanded to 5 ATM (decreased pressure, decreased temperature)

4. Liquid Air is obtained--The great drop in pressure (from 200 to 5 ATMs) puts air below critical temperature and all gases turn to liquid.

5. Liquid Air is brought to the distilling column and warmed to boil off the unwanted gases. Air is warmed to just below the boiling point of 02.

ex. Nitrogen boiling pt -1960 C at 1 ATM

Oxygen boiling pt--1830 C

6. The distillation process is repeated until 99% pure 02 is obtained.

7. Pure 02 is then placed in liquid storage or as gas in cylinders for delivery to health care facilities.

The Safety Indexed Connector System s The purpose of these safety systems is to make only correct connections between the cylinders and the delivery systems.

1. The American Standard System--This is for H and K cylinders. The gas channel through their nipple of the regulator is aligned with the channel through the threaded outlet. The two parts are held together with a wrench tightened hexagonal nut. There are four divisions of this system: internal and external threads, right and left handed threads. Every medical gas has a distinct combination of this system.

2. The Pin Index Safety System--(PISS)--This is for small cylinders AA-E which use a yoke connection. This system was

first designed for anesthesia machines where fixed yokes were attached to the internal gas circuitry. This design is to prevent the wrong cylinder of medical gas from being attached to the wrong yoke. There are six positions of pins located on the yoke with the corresponding holes drilled into the valve face of the medical gas, Each gases has 2 pin positions i.e., 02 has the 2,5 position. Be sure to save the rubber washer for this system or leaks will occur.

3. The Diameter Index Safety System--(DISS)--This is a low pressure safety system used for psig<=200. It is most often seen used in flowmeters and regulators after the reducing valve. Each medical gas has its own specific threaded connector (ex Bore I and Shoulder I ) that can not be interchanged with another medical gas.

4.Quick Connects--the connectors for each medical gas have

their own specific shapes (circles, squares, and diagonals) that will only fit into those shapes on the wall. This system is used for wall flowmeters and psig<=50. The goal of all these safety systems is to prevent the therapist/health care provider from administering the wrong medical gas to the patient.

Devises that regulate gas pressure and flow

1. Reducing Valve- devise that reduces pressure from a high value to a lower one. The reducing valves we work with normally change 2200-2400 psig (02) to 50 psig (working pressure). 2. Flowmeter- a devise that adjusts the flow of gas in liters per minute after the pressure has already been reduced. 3. Regulator--a devise with a reducing valve and flowmeter. The reducing valve is decreasing pressure in psig (English system) while the flowmeter reads flow (volume/time) in liters per minute (metric system).

How a reducing valve works--The two forces that interact are spring tension and gas pressure. As gas pressure at the bottom drops, the spring tension becomes the dominant force. It pushes the diaphragm downward opening the poppet valve. When the poppet valve opens, gas flows into the bottom chamber of the reducing valve. Gas continues to flow in until the pressure rise equals the spring tension. The diaphragm will then be straightened out and the poppet valve will close. All reducing valves have a popoff valve also to vent excessive pressure to the atmosphere if debris or other malfunctions cause a pressure buildup.

Types of Regulators

1, Preset to 50 psig--This type is the most common in hospital practice. The poppet valve opens until 50 psig is achieved then closes. -

2. Adjustable--These have a key or threaded hand control on the reducing valve face, which allows adjustment of pressure on the diaphragm (up to 100 psig). These regulators permit a wide range of flow and pressure to be achieved. All Bourdon regulators are adjustable. The Bourdon is actually a low-pressure regulator that has one gauge for pressure and another gauge that converts pressure to flow.

3. Multiple Stage Regulator--accomplishes pressure reduction in two or three stages for precision in flow control. Used in industry not the hospital, The number of stages =the number of popoff valves present.

In Bulk 02 systems a reducing valve is incorporated after the vaporizer to reduce pressure to 50 psig.

Back Pressure and Regulators, Flowmeters

Back pressure occurs when there is a pressure drop across a restriction. When we hook up an 02 devise to a regulator via a flowmeter, back pressure can occur therefore the liter flow going to the patient would drop. Some of the regulators/flowmeters we work with are affected by back pressure and others are not.

Bourdon Gauges and Back Pressure-The Bourdon Gauge is calibrated so that its outlet is open to the atmosphere, therefore every time we hook up an 02 devise we cause back pressure. The Gauge reads this back pressure and indicates flow in liters per minute (lpm) that is HIGHER than what is actually going to the patient. In addition, if we obstruct the outlet of the Bourdon Gauge it reads the back pressure, even though no flow is going to the patient.

Uncompensated Flowmeters and Back pressure--These flowmeters are calibrated in lpm against atmospheric pressure. The gas flow is regulated by a needle valve upstream (proximal) to the ball or float. The ball or float in the Thorpe tube has two forces working against it. Pl, the flow of gas from the wall or cylinder, and P2, gravity pulling on the weight of the ball, float and back pressure. Pl > P2 due to Bernoulli's principle. When an 02 devise is attached, there is an increase in back pressure that pushes down on the ball or float recording less gas flow than the patient is actually receiving.

Compensated Flowmeters and Back pressure--These flowmeters are calibrated against 50 psig, The gas flow is regulated by a needle valve downstream (distal) to the ball or float. PI always =P2. No matter what 02 devise is attached the flowmeter does not respond to back pressure because it is calibrated at 50 psig, therefore flow going to the patient will be accurate.

Summary Chart Response to Back Pressure// Delivers to Patient

Uncompensated Flowmeter reads low normal flow

Compensated Flowmeter reads normal normal flow

Bourdon Gauge reads high low flow

Clinical Information--Even though the Bourdon Gauge is inaccurate, we use it clinically as it can be read in any position, while a flowmeter must be read in the upright position due to gravity. Uncompensated flowmeters may appear in home care or other unlikely places.--Beware

Tests to see if a flowmeter is back pressure compensated

1. Read the label-states it is pressure compensated or calibrated at 50 psig. 2. Watch the Ball or Float--The Ball or Float will jump when plugged into a gas source. It will fall to zero when the pressure in the Thorpe tube =the source pressure. (Thorpe tubes have balls, while Kinetic flowmeters have floats or plungers) 3. Take the flowmeter apart. In a compensated flowmeter the needle valve will be downstream. This option is obviously no practically clinically.

Expanded scale Flowmeters--Clinically we used these for COPD (Chronic Obstructive Pulmonary Disease) or pediatric/neonatal patients. These scales are easier to adjust when a more precise control of low flow rates is needed. The flow ranges are 0-4 lpm, 0-8 lpm, and 0-15 lpm. Review Hypoxic Drive in COPD patients-If we give these patients too much 02, they will stop breathing.

02 Bulk Systems (liquid and Gas)--once pressure is reduced, 02 travels in brass or copper pipes throughout the hospital. The pipes must be protected from corrosion. frost, oil, grease and given adequate ventilation. They must also be insulated if they travel in combustible walls. Riser Valves are between floors and maintained by hospital maintenance. The Zone valve covers distinct areas of the hospital (OR, ER, ICU) and are important for us to know their location as they need to be shut off in case of fire. Their mostly likely spot is next to the nurses' station.

compressors Used in Respiratory Care

1. Piston--As the piston drops, gas is drawn in through the one way intake valve. on the upstroke, the intake valve closes and gas leaves through the outflow valve. Medical Air pumping systems use the piston, but its size is limited due to the noise and vibration. Portable Examples include the Timemeter.

2. Diaphragm--The diaphragm substitutes for the piston. These are used mostly for small portable models such as the Airshields Diapump or the DeVilbiss nebulizer. Some units combine air compressors and suction.

3. Rotary--the rotor acts as a fan pushing the air from one area to the other. Examples Include ventilators such as the MA1.

02 Concentrators in Respiratory Care

1.Permeable Plastic Membranes--These are older models. The

membranes are 1 micron thick, and gases diffuse across them

according to their solubility and pressure gradient, A

diaphragm compressor provides a constant vacuum across the

membrane. 02 moves across faster than N2 as a result 40% 02 is available at 1-10 lpm. Remember that hospital 02 is 100% so a patient going home on this concentrator would have to have their flow increased above hospital level until adequate ABG's(Arterial blood gases) are obtained.

2.Molecular Sieve--a Compressor pumps room air to one of the two sets of sieves. Inorganic Sodium Aluminum Silicate pellets are used to absorb N2 from the air while 02 passes through. The 02 concentration is flow dependent. At 1-4 lpm the concentrator is able to =ABG's obtained on 100% hospital 02. Fortunately, 95 % of our patients need <=4 lpm at home. If place on 10 lpm, the concentrator is giving only 50% 02.

Part III-Humidifiers and Nebulizers

Definitions and Review--Humidity is molecular water in a gaseous state or vapor. 1. Absolute Humidity is defined as the actual H20 content of gas in a volume of gas,* ex. g/m3. H20 is extracted from a known volume of gas and weighted.

2. Relative Humidity is defined as actual H20 vapor content/capacity to hold H20 at any given temperature. If temperature is increased, there is an increased capacity of gas to hold H20 due to greater kinetic motion. There is also an increased Pp and greater ability for molecules to escape into the gaseous phase.

% Relative Humidity =Content/Capacity x 100 or Pp gas/Pp H20 x 100 Normal Body Humidity = 43.8 mg/L or 47 mm Hg (Vapor Pressure).

Rationale for the Use of Humidification in Respiratory Care

1. Simple Humidifiers are designed to provide enough H20 vapor to inspired gas to make it comfortable for the patient,

2. Complex Humidifiers are designed to provide heated gas at 100% RH at body temperature (37o C). This is also known as Body Humidity.

Factors Affecting the Efficiency of Humidifiers

1. Time of contact between the gas and H20--the longer the gas and H20 molecules are in contact the greater the mixing.

2. The Surface area involved in the gas/H20 contact--the greater the surface area of the gas/H20 interface, the more the humidity molecules can push their way into the gas mixture.

3.Temperature-- the greater the temperature, the more humidity molecules can push their way into the gas mixture. Clinical Example--Simple Humidifiers can provide 100% RH at Room Temperature but at body temperature (37o C) they only provide 1/3 of the RH needed.

Simple Humidifiers

1. Passover or Blowby--gas passes over the H20's surface. These are very inefficient due to decreased time and surface area exposure. Clinical Examples are old incubators and the Emerson Post-Op ventilator.

2. Bubble or Diffusers--These are the most common type used in Respiratory Care. Gas is conducted below the H20 surface and broken up into small bubbles via a diffuser. The bubbles float to the H20 surface and break, so at this point the gas and H20 molecules have mixed.

Important Clinical Points--The smaller the bubbles that the diffuser produces, increased surface area produced, increased efficiency of the humidifier. The higher the flowrate used in a bubble, decreased time gas and H20 spend together, decreased efficiency of humidifier.

Clinical Examples--older Non-disposables are Puritan or Ohio Bubblers. Newer disposables include Aquapak 302 (prefilled), Hudson, Bard Parker, OEM.

Clinical Question to consider--Is it better to spend your therapist's time filling Bubblers or should you buy the prefilled types that cost a lot more?

The Bubbler Humidifiers are dramatically affected by the H20 level, decreased H20 level results in decreased output due to decreased surface area.

To accurately evaluate a humidifier a therapist should ask the following questions: 1. Can the unit deliver a high RH and not break down in the clinical environment? 2.At what H20 level does the efficiency of the unit drop? 3.Does the unit leak gas, spill or do other things that drive you and the nurses crazy?

4. How much does it cost for what it gives you?

Heated Humidifiers We know that simple humidifiers provide 100% humidity at room temperature (22o C), but only 1/3 RH at 37o C (body temp). In

in order to provide body humidity ( 100% RH at 37o C), we must turn to complex Heated Humidifiers.

Normally our nose with its turbinates supplies a great deal of humidity so that by the time atmospheric gas reaches the tracheal carina, it is 100% RH at 37o C, no matter what its starting conditions were. Patients who are intubated (endotracheal tube) or trached (tracheotomy tube) have their upper airway bypassed that normally takes care of Humidification. Therefore, therapists must choose appropriate complex humidifiers to replace the upper airway.

All three factors (time, surface area and temperature) are used to increase the H20 carrying ability of the gas. As complex humidifiers heat gas to 37o C (compared to room temp., 22o C) gas cools in the delivery tube as it leaves the humidifier on its way to the patient. This condensation in low spots can block the tube and gas flow to the patient. We call it "rainout.11

Types of Complex Heated Humidifiers

1. Wick Type Humidifiers--a sponge or hydrophilic paper absorbs H20 via capillary action. As gas passes over the wick, the water evaporates and humidity is delivered to the patient.

a)Conchapak Aquatherm I, II, III--A low resistance paper wick was placed inside a metal canister.. Sold with its own gravity feed system and sterile H20--Watch out for one way valve! It has a servo-controlled heater and sensing probe, and can be used as a high flow devise. As with the Bird, the wick is disposable. Sterile H20 is gravity fed in the bottom to wet the wick with a safety overflow on top.

2. Modified Passover Humidifiers--Passover Humidifiers that use heat, increased surface area, time and other devises to increase their efficiency. Example Fischer-Paykel

3. Heat Moisture Exchangers (HME's) or Hygroscopic Moisture Exchangers--used to be called artificial noses. Examples are the Engstrom Edith, Pall, and Humidivent. The patient must have an artificial airway in place. The HME is placed at the patient wye on the ventilator or via adapter directly on the ETT or trach tube. On exhalation it traps saturated gases and 37o C in its hydrophilic filter. on inhalation, the warm saturated gases are released from the paper back to the patient. In order to use these optimally, the patient must be well hydrated. These devises are extremely useful in the chronically ill pediatric population with BPD (Bronchopulmonary Dysplasia) to increase mobility and a normal life style. When working ideally, these HMEs should be able to recover 70-90 % RH from the exhaled gas. Hygroscopic ME add a hydrophilic salt (Na based) to the HME to increase its efficiency.

Aerosol Therapy and Nebulizers

Aerosols are defined as liquid or solid particles suspended in a gas, ex. cigarette smoke, mist. IMPORTANT--Humidity is defined as molecular H20 (the human eye can't see it) while aerosol is defined as particulate H20(the human eye can see it). Particulate H20 is droplets suspended in a gas.

Aerosol is measured in two ways: 1. particle size-This is a major factor in determining how deep into the respiratory tract a molecule will land. The stability of a particle is directly related to its size. and 2.Total volume output in cc/min. The smaller size particles a nebulizer puts out, the lower the total output. This is ok as smaller particles have optimal local effect with minimum systemic side effects. This is critical when administering a drug.

Six Factors that affect Particle De-position

1. Gravity--Stokes Law states that the rate of sedimentation = density x (diameter )2 . Translation-the larger particles are more affected by gravity and will deposit in the respiratory tract sooner. Gases that have a small diameter or low density have a hard time bouncing off and keeping aerosol particles up in a mixture--ex, Helox.

2. Kinetic Activity--Particles >= .1 um deposited by gravity while particles <= .1 um deposited by Brownian Motion. Brownian Motion means that the smaller aerosol particles get, the more they resemble the gas molecules hitting them. A particle that is .1 um. is the most stable, i.e., it is likely to be inhaled/exhaled without depositing in the airway.

3. Particle Inertia--The greater the particle mass, the more likely it is to be deposited in the upper Respiratory tract at a bifurcation in a conducting airway.

4. Physical Nature of the Particle--a) Hygroscopic particles-ex. propylene glycol-absorb H20 so they increase in size and deposit sooner in the Respiratory tract. b) Hypertonic-this solution absorbs H20 and increases particle size. c) Isotonic-stable particle size as same osomolarity as body. d) Hypotonic-lose H20 to tissues, decrease size of particles, and travel further down Respiratory tract than expected.

5. Temperature and Humidity of the Carrier Gas--the higher the temperature of the carrier gas the more aerosol can be carried.

6. Ventilatory Pattern-- a slow deep breath ( a Vt 2x normal) with a breath hold of 15 seconds is ideal but clinically impossible. A slow flow rate prevents premature deposition of the particles due to gravity, inertia and increased kinetic motion. In addition, a deeper breath distributes large volumes of gas more uniformly in the lungs due to recruitment of uninflated alveoli.

Review Particle Size Charts

Nebulizers--General Characteristics

1. Many nebulizers we use clinically use Bernoulli's Jet principle--the decrease in lateral pressure and sucking action not only causes air to be entrained but also causes H20 to be drawn up the capillary tube. The gas and H20 meet, particles are then baffled and the smallest ones go out to the patient.

An atomizer has no baffle so large particles fall into the pharynx and nasal cavity, ex. topical anesthetics used for bronchoscopy or decongestants. Any object in the way of particles that converts large ones into small ones is considered a baffle (ex. balls. sides of the container).

Small Volume or Small reservoir Nebs.

1.These are hand held nebs used to deliver medication-Clinically we call them mini-nebs, rain drop nebs, etc. There are two basic types: a) side stream nebs where the aerosol is produced via jet and then injected into the gas stream. These give a lower total output but smaller particles. b) main stream nebs where the main flow of gas passes through the aerosol and helps create it. These give a higher total output and larger particles, and are more common in clinical practice.

Metered Dose Inhalers (MDI's)--In place of mini-neb or small medication neb Tx's, these medications are often given. They take less of the therapist's time to administer, but require extensive patient education for proper administration. These small canisters of bronchodilator drugs are measured out in "puffs" of medication. Each puff contains a very exact amount of drug. Drs. normally order the MDI as 112 puffs of drug, q4". The drug is propelled into the patient's lungs using fluorocarbons. These chemicals can cause fatal cardiac arrhythmias if used too often in a short period. Tolerance to the normal dose or tachyphlaxis can easily develop in users. The proper administration technique is rarely used (see classroom demonstration), so recently "spacers" were developed to help patients with lack of coordination. The spacers allow the patient to squeeze the drug into the bag or container, and then breathe in at their own rate and depth.

MMAD (Mass Median Aerosol Diameter)--This is a concept used in pulmonary system research articles that tries to accurately describe the size of particles in the clinical environment. Remember the median is the halfway point. This term indicates that in a study, one half the particles are bigger than this number and one half the particles are smaller than it, i.e, it is the average size of the particles in a study.

Large Volume Nebs with Air Entrainment

1. These large volume nebs can hold at least 500 cc of H20. Using the Jet Principle, they are designed to deliver aerosol to the patient for an extended period. For example, these may be used on post-op patients that have just undergone surgery with dry anesthetic gas. The Small volume nebs are used to deliver bronchodilator drugs to patient with airway narrowing, so they last only a short period of time (10 minutes).

The older large volume nebs are non-disposable (ex, Bird, Puritan All Purpose, and Ohio deluxe) and had to be resterilized between patients. The newer large volume nebs are all disposable (ex, Inspiron, Travenol).

2.One of the goals of large volume nebs is to met or exceed the patient's inspiratory flow demands, A sick patient can easily breathe at 2-3x the normal VE The way to meet this demand is through air entrainment.

VE= Vt x f in lpm-examples

Review Chart of Air Entrainment

If the patients V, is not meet, the patient will draw in room air through the mask's exhalation ports resulting in a decrease in F102. The best way to meet the patient's flow demands and VE is by watching to make such there is always leftover mist on inspiration. If not, increase flow.

3.Clinical problem--Consulting the air entrainment chart, we see that at lower F102's there is increased air entrainment, resulting in increased aerosol output (cc/min). But due to the fact that the H20 and gas spend Little time together the aerosol density is decreased (thin mist). Why is this an important concept to understand?

4. In order to increase the moisture carrying capacities of

gas we provide heat via rods, plates, donuts or jelly roll heaters. The immersion rods and plates are hard to sterilize and may be a source of bacterial contamination. They are inefficient as they heat the entire water source. The donut and jelly roll system only heat the aerosol going out to the patient at that instant. Both systems have a metal sleeve incorporated to increase heating. All of these disposable system have air entrainment from 28-100%, however a drawback is that no heated nebulizer system is servo-controlled, therefore you must place a thermometer near the patient.

5. The debate about nebs as a source of bacterial contamination-fact or fiction? We used to think that since nebulizers put out both particulate and molecular H20 that bacteria could climb on the larger particulate H20 and ride into the patient’s respiratory tract. In order to prevent nosocomial infection, we would change our nebs qod (Nosocomial infections are those inquired in the hospital vs., community acquired infections). Newer research has shown that the patient spewing bacteria into the delivery tubes not the nebs may be the real cause, therefore we could change our nebs much more infrequently, and save a lot of money.

Large Volume Type Nebs II

The Centrifugal is a spinning disk that rotates on a hollow shaft, H20 is drawn up the center of the shaft and thrown outward by the centrifugal force through breaker combs. Aerosol is produced. Used in home Care (ex, DeVilbiss, Hankescraft), air entrainment is limited.

Large Volume Type Nebs III

Ultrasonic Nebs use Piezoelectricity as their principle of operation. Electricity passes through a ceramic disc; this changes the disc's shape and causes it to emit a specific length sound wave (1.35 Mc). This sound wave travels from the disc through tap H20 in the coupling chamber. The sound wave hits the bottom of the medication cup (which had saline and medication inside). The sound waves cause a fluid geyser inside. The large particles fall back into solution while the small particles are

picked by the source gas (normally rm. air via blower fan) and taken out to the patient.

The frequency of the sound waves determines the particle size (very stable at 3 um.) while the amplitude control determines the amount of aerosol output. Many models have an indicator to show if the tap H20 level is too low.

Troubleshooting--If it doesn't work 1, clean the ceramic disc off with an alcohol prep pad and clean the blower fan filter; 2. Check to make sure tap water is in the coupling chamber and there is enough; 3. check electrical connections-Watch out for leakage!!!

Clean each US unit at the end of the shift--They are an excellent source of nosocomial infection.(Pseudomonas Aeruginosa)

Bleed In System

If a patient needs between 21-28% (ex. a BPD child or a COPD adult), we set up a bleed in system. We run a nebulizer off rm. air flowmeter or air compressor. In the delivery tube, we cut in an adapter hooked up to an 02 flowmeter. We adjust the 02 flow and analyze the FI02 at the patient. Be sure to tape and mark 02 flowmeter or the nurses will be adjusting it.

Humidity Deficit-This may occur due to inadequate Humidification from systemic dehydration or a poorly working humidifier. The elderly and newborns are especially prone to systemic dehydration due to vomiting and poor nutrition.

In order to figure out the humidity deficit caused by a humidifier, subtract the humidity output from 44 mg/l. In the clinical environment, we look for increased viscosity in patient's secretions.

A. Mucociliary Escalator-Anatomical and Physiological review- The mucosa lining the respiratory tract is uniquely designed to prevent infection from spreading to the lower airways. The epithelium, pseudostratified columnar, is unique in that it contains cilia that beat in a whipping motion. The epithelium all touch the basement membrane, but they do not all reach the lumen. On top of the cilia, there are two layers of MUCUS. The bottom layer is the sol that is secreted by the bronchial glands in the submocosa. It is a thin watery substance. The top layer, the gel, is thick and viscous. It- is secreted by the goblet cells, wine glass shaped cells that are interspersed in the pseudostratified epithelium. Particles of debris that land in the gel are moved toward the back of the pharynx by the forward whipping motion of the cilia. The top of the cilia just touch the gel layer at the top of their upstroke. This prevents organisms and dirt from infecting the lower respiratory tract.

In order for this system to work, drinking and eating enough fluid must properly hydrate the patient. If the mucosal layer becomes inspissated (dried out), the cilia will stop beating, and the patient will be an easy target for infection. Once the mucus is dried out, it is much harder for water to repenetrate it, so the patient can be rehydrated.

Clinical signs of dehydration include loss of turgor of skin, lethargy and weakness, decreased blood pressure and urine output.

If infection does spread into the alveoli, the pulmonary macrophages will ingest the offending organisms up to a point. However, invading organisms easily can overwhelm them. Smoking and Alcohol can compromise both the mucociliary esculator and the macrophages!

B. Clinical Uses of Aerosol Therapy

1. To rehydrate or wet down the respiratory tract postoperatively due to the inhalation of dry gas or from systemic dehydration.

2. to deliver medication to the alveoli to relax the smooth muscle surrounding the bronchioles, thus causing bronchodilation. Used to reverse bronchospasm caused by asthma or the aerosol particles themselves.

3. To decrease mucosal edema and airway irritation in certain disease states such as Croup.

4. to thin out bronchial secretions and stimulate a cough.

C. Clinical Hazards of Aerosol Therapy

1. Bronchospasm can be caused by aerosol particles that we are giving to relieve mucosal edema. What are the clinical signs of bronchospasm? How would you treat it?

2. Bronchodilator drugs given to relieve bronchospasm have their own strong side effects-nausea and vomiting, muscle tremors, tachycardia, nervousness and anxiety are all side effects.

3. Drug reconcentration especially if one is using Ultrasonics is a theoretical hazard. (i.e., the saline is nebulized first, then the drug).

4. to thin out secretions (mucolytic) and stimulate a cough. 5. Infection can be caused by unclean equipment (Nosocomial). The most common organism in the hospital is Pseudomonas Aeruginosa. It is gram + with a sickly sweet smell to the patients secretions. The mucus is normally a light green color. RT equipment should be cleaned at least once a day.

Sputum Inductions--An ultrasonic or mini-neb is used. Isotonic, but more often hypotonic or hypertonic solutions, are used. The three major types of exams done on sputum are:

1. Bacteriological exam-cocci, bacillus or spirochete?--We call this C & S, culture and sensitivity. We examine a sputum smear under the microscope to identify the organisms (culture) and then we determine the antibiotics that are most likely to kill it or at least stop it growing (sensitivity).

2. Gram, stain-really another part of the bacteriological exam--In the lab or ER, we stain first with crystal or gentian violet. The organisms with thick cell walls hang onto this dye even when washed in alcohol afterwards. They are called Gram + organisms. After the violet dye, we wash the slide in isopropyl alcohol and then restain in safranin red. Organisms with a thin cell wall will have it dissolved by the alcohol and pick up the red dye. We call these gram - organisms. The Myobacterium Tuberculosis has its own special stain, carbolfuchian, known as the Acid Fast Bacillus, (AFB) that uniquely stains the cell wall of this large organism.

3. Exfoliative Cytology-This test depends on the fact that cancerous cells fall off their tissue more easily than normal cells. This is the principle of the Pap smear used to detect cervical cancer. We use this same principle to look for cancerous cells (especially bronchogenic) in sputum smears.

D. Insensible Water Loss--This is the amount of water we lose everyday from our body through our lungs and skin, but we are not aware of it.

Daily Intake--The majority of our daily intake of fluid is oral. 2/3's of our intake comes from liquids, 1/3 comes from our food. The body synthesizes 150-200 ml of H20 a day from H2 oxidation. The normal daily intake is 2400 ml/day. In the hospital we measure the I's and O's on patients (Intake/Output ratio). What goes in must be peed out or we end up with edema.

Normal temp Hot Weather Heavy Exercise

Insensible 350 ml 350 350

H20 loss --- skin

due increase

lungs 350 250 650 in VE

Urine 1400 1200 500

sweat 100 1400 5000

Feces 200 200 200

Normal Insensible water loss is 700 ml/day (350 + 350). Changes from the norm occur in hot weather when the atmosphere has already done some of the respiratory systems, work by pre-warming and humidifying the inhaled gases. In heavy exercise, due to an increase in V, more insensible water is lost from the lungs. Urine output is dramatically affected by the body's need to conserve fluid to maintain BP. The output of sweat increases with hot weather and exercise.

We know that the skin protects our body from major water losses and invading infections. In burn victims (especially third degree), the epidermis and dermis has been burned . The epidermis contains cholesterol (fatty substance) that prevents the evaporation of massive amounts of water from our skin. We say the skin is cornified (contains cholesterol, preventing H20 loss). Burn victims may lose 4-5 Liters of fluid a day in insensible loss due to their lack of skin.

Part IV-02 Delivery Systems (Equipment and Techniques)

Classification of 02 devises--l. Fixed Performance or High Flow devises-02 units that supply all the inspired gas needed to meet a patient's VE. The FI02 delivered is not affected by the patient's ventilatory pattern.

2. Variable Performance or Low Flow devises--units that don't supply all the inspired gas needed to meet the patient's VE' Room air is mixed with the 02, therefore depending on the patient's ventilatory pattern, the FI02 is variable.

Definitions and normals-1. Respiratory Rate-the number of breaths per minute-Normal Adult RR= 12-20, Normal Neonate RR= 40-60 Normal Pediatric RR= 20-40.

2. Vt-Tidal Volume-the normal amount of air breathed in or out when a person is resting comfortably. Normal Adult Vt= 400-600 ml, Normal neonate = 25-50 ml, Normal Pediatric = 50-400 ml.

3. VE-Minute Ventilation-the amount of air breathed in or out in one minute. Normal Adult VE <= 10 LPM. No real normals for neonates and Pediatrics-we'll learn to assess WOB (Work of Breathing).

4. Respiration-a. Internal -- the exchange of 02 and C02 at the cellular level and b. External--the exchange of 02 and C02 at the lungs.

5. FI02 (Fractional Inspired Concentration of oxygen)-21-100%.

6.Ventilatory Pattern-the rate, depth and amount of work a patient is putting into breathing. Examples are Cheynes-Stokes, Biots and Kussmauls.

7. Apnea--no breathing--Central vs. obstructive.

8. Deadspace-An area of the lung has Ventilation but no blood flow (perfusion). V/Q ratio =Ventilation/Perfusion Ratio

9. Shunt--An area of the lung has perfusion but no ventilation.

in Deadspace we have a large number/O= infinity. In shunt we have O/large number = 0.

Low Flow Devises

1. Nasal Cannula--The advantages of this devise are ease of application, light weight, economy and disposability. The disadvantages are instability (easily dislodged from a restless patient); low flow rates must be maintained (<= 8 LPM) to prevent sinus headaches; and nasal pathologies (ex, deviated septum, mucosal edema, polyps) will decrease 02 uptake.

Normal FI02=22-50%, Normal flow rate 1/8-8 lpm

2. Nasal Catheter--This devises is passed through one nasal passage with its tip in the oropharynx. There are two placement methods: 1. The distal 1/3 is lubricated with a H20 soluble gel, then the catheter is slid along the nasal passages until the catheter tip is just pass the uvula. We use a tongue depressor to visualize the uvula, we pull back the catheter until it has disappeared, then tape to the nose. 2. Blind Method--measure from the tip of the nose to the ear lobe and place as above.

Clinical Questions to answer-a] Where is the uvula? b] Why do we a use water soluble gel? c) Why do we pull back from the uvula?

Aspiration Pneumonia-When air enters the patient's stomach in large quantities, it becomes distended and the patient vomits. The pH of the vomitus is <= 2, so this acidic ion is aspirated into the trachea which is directly in front of the esophagus. This acid eats away the parenchyma causing further respiratory complications. For this reason, we always try to place catheters by the first method.

Force shouldn't be used to advance the catheter down either nare as mucosal edema will result. Catheters should be changed every eight hours as the body interprets them as foreign bodies and quickly adheres to them.

In order to prevent aspiration pneumonia, deeply comatose patients or an elderly patient with obtunded reflexes such as a post stroke patient should not use a catheter. Today we use them rarely, but all the problems they cause are still with us (ex Nasopharyngeal suctioning, Nasogastric tube placement). Assess for a distended hard epigastrium.

Normal FI02 range 22-50% Normal flow rates 1/8-8 lpm

3. 02 Masks-General Characteristics

a) Masks are used when we need 02 quickly and for a short per4od of time. They are uncomfortable due to pressure necrosis of the skin. They are also hot as they trap the radiating heat from the nose and mouth. The humidity that is trapped breaks down the skin.

b) The mask can become a vomit trap. If you have an unconscious patient and he vomits due to the decreased gag reflex he will a-,pirate the vomit into his lungs causing further respiratory problems, If you must use a mask with this type of patient, an oral airway must be inserted to prevent the flaccid tongue -from obstructing his airway.

Simple Mask-loose fitting disposable unit used very often on ambulances, not so much in the hospital. Room air can be drawn in around the edges of the mask and through the exhalation ports. A low flow of 02 is necessary to flush the Deadspace for C02 removal. The FI02 delivered to the patient depends upon his ventilatory pattern and the amount of room air being drawn in.

Clinical questions--l. Would this be a good devise to use in a patient taking slow swallow breaths? Would it deliver a high or low FI02 in this situation? 2. What about a patient who is tachypneic or in acute respiratory failure? What would the FI02 be in this situation?

4. Partial Rebreather Mask--This can be either a low or high flow depending upon the patient's ventilatory pattern. The purpose of this mask is to conserve 02 by rebreathing some gas from the conducting airways. The conducting airways are all the generations of bronchi and bronchioles that don't participate in gas exchange therefore remain relatively high in FI02. The reservoir holds 100% 02.

on inspiration, the patient draws Os from the bag into the

mask and gets a high FI02. During exhalation, the first 1/3 of the gas comes from the conducting airways (anatomical Deadspace)and goes back into the reservoir bag. The second 2/3's which has participated in gas exchange goes out the mask ports (The pressure in the inflated reservoir bag prevents the last 2/3's of the exhaled gas from coming in). The 02 flow into the bag should be high enough to prevent it from collapsing and to wash out C02. The exhalation ports serve as emergency inlets for room air in case the 02 source gets disconnected.

Normal FI02=up to 60%. Normal flow rates = 6-10 LPM or what keeps the reservoir bag inflated on inspiration.

High Flow Devises--Historically, the first high flow devise was a rebreather mask used in anesthesia. The mask tightly covered the nose and mouth. It had an attached reservoir bag from which the patient inhales. As this is a closed circuit, exhaled C02 is adsorbed through a filter while fresh 02 is added to replace that metabolized by the patient.

1. Non-Rebreather mask-mask with valves and reservoir bag. On inspiration, the valve between the mask and bag opens. 100% source gas flows to the patient, The Mask valves are closed due to the sucking action of the patient. On exhalation, the mask/bad valve is closed so the fresh source gas is not contaminated. Meanwhile the Mask Valves open to allow the patient to exhale C02. We take one mask valve off so in case the 02 source is disconnected, the patient can draw in room air.

The disposable hospital model with one mask valve off really delivers about 70% 02 due to the leaks around the face and the missing valve. Normal flows to start an adult are 6-10 lpm. If a specialty gas must be given (Helox, Carbogen), we try to make a very snug fit and replace the valve, then closer to 100% can be achieved. This type of patient must be monitored constantly by health care practitioners. Humidification systems (i.e. bubble humidifiers) cannot add effective humidity due to the high patient flows, and secondly, they can be dangerous as humidity may make the one way valves stick.

2.Air Entrainment Masks-Venturi Masks-HAFOE(High Air Flow, Oxygen Enriched)--Uses Bernoulli's principle, a jet entrains air just distal to the restriction. The smaller the restriction, increased forward velocity, decreased lateral pressure, more air entrained, decreased F102.

All Venturi masks have as their goal to give an exact FI02 while providing total flow>= the patient's peak inspiratory flow. In addition to the size of the restriction, the FI02 is determined by the size of the entrainment port, lpm to the jet (remember to follow the manufactures, specifications) and the amount of resistance encountered in the system.

Review Total Flow problems, Air Entrainment Ratios.

The back pressure caused by hooking several devises together will cause decreased air entrainment, therefore an increased FI02 to the patient. At F102's <= 40%, no humidity will need to be added to the mask, but at higher F102's, humidity may need to be added due to increased flow. Demonstration humidity collar.

Very important clinical problem--What type of flowmeter, air or 02, should the humidity collar be hooked up to and why?

These masks are uncomfortable and must be removed for eating and drinking. Once an ABG is obtained, we try to switch the patient over to a comparable setting on a Nasal Cannula.

All Pneumatic Large Volume Nebulizers can be considered high flow devises also. Remember when in the high F102's (>= 50%), set up two nebs to provide the patient with adequate flow.

Miscellaneous Devises--These devises are normally used with high flow setups, but don't neatly fall into the category.

1. 02 Blenders--This piece of equipment incorporates a proportioning valve to adjust FI02 and reducing valves to decrease the 50 psig down to a comfortable level for the patient. The Bird, Bennett and Ohio models can give the patient between 90-120 lpm if necessary. These blenders are used with free standing high 'flow set-ups or on ventilators.

2. Face tent--This devise uses large bore tubing and fits snugly on the chin. Good to use in case to facial/nasal trauma. Hooked to a neb for heat, humidity and 02.

3. Tracheostomy collar--used in trach patients with large bore tubing and a neb. Provides heat, humidity and 02 to patient.

4. T piece--used with an ETT especially during weaning. Not recommended for trach patients.

5. Aerosol Mask--used with large bore tubing and nebs, U/Sonics or any setup that gives particulate H20.

Infant/Pediatric Devises

1. Pediatric Hoods-used with both humidifiers and nebs, can provide heat humidity and 02. Hoods cover only the child's head leaving the rest of the body available for nursing care. Blenders can be used to give a precise FI02 (ex, BPD). The gas must be warmed as the infant's temperature sensors are on the face, decreased temperature, increased 02 consumption. Your goal is to maintain a Neutral Thermal Environment (NTE).

2. Croup Tents--These are used in pediatrics to provide a cool temperature within a plastic enclosure. The cool aerosol helps decrease airway edema during Croup and epiglottis. Flows of 12-15 lpm must be used to washout C02. FI02 is impossible to control (either room air or 02). All electrical appliances (nurses call button, electric toys, etc) should be kept out of croup tents due to possible sparks.

3.Incubators--used to produce NTE for premature infants. 02 added via heated neb or humidifier. The newer incubators have double walls to maintain NTE and prevent apnea and bradycardia.

4. Cannulas use a sticky play dough type substance that we mold to the child's cheeks. This dermaplast or Tegederm secures the Cannulas and makes it much more challenging for the kids to remove them. We see simple mask, aerosol masks and Venturi masks used on a limited basis in pediatrics. T-pieces and trach collars are used very commonly.

Devise Flows 02 Concentration

Nasal Cannula 1/8-8 lpm 22-50%

Nasal Catheter 1/8-8 lpm 22-50%

Simple Mask 6-10 lpm 35-55%

Partial RB 6"10 lpm up to 60%

Non RB 6-10 lpm loose fit 70%,

tight fit 100%

High Flow Nasal Cannula--Aquinox

Part V--Non-Invasive Monitoring

Pulse Oximetry-This is a non-invasive way to measure 02 saturation, ie, the patient doesn't have to be stuck for an ABG routinely. However, these machines must be used very cautiously, as they only tell you about the Hb present, not the actual amount of Hb that the patient has. In other words, the patient can have an excellent saturation and Pa02, but still be very anemic.

The machine works the following way: Both red and infrared light absorb Hb and deoxy Hb with different intensities at different wave lengths. We take advantage of this fact by shinning these two types of light through a pulsating arteriolar bed. The different ratios of Hb/Hb02 for red and infrared light can be read out as a saturation. (See Figure10-13, p306, Mosby)

There are two basic types of pulse oximeters: 1. The Functional type that uses this equation: Hb02/ Hb + Hb02 (total Hb). 2. Fractional type: Hb02/Total Hb + dysfunctional Hb.

Examples of dysfunctional Hb include COHb and Meth Hb. COHb comes from fires or leaky mufflers. Co has 210x the affinity for Hb that 02 has.

Meth Hb is when the iron portion of the Hb molecule changes from the ferrous form (Fe++) to the ferric form (Fe...). Meth Hb is unable to transport any 02. Substances that can cause Meth Hb are the nitrates, nitrites, nitrous gases, nitroglycerin and sulfonamides. Sources of these substances are well water, shoe polish, welding materials, powdered milk and red wax crayons. Rx's for COHb is 100% 02 to knock the Co molecule off the Hb, and for Meth Hb, methylene blue in severe cases.

See classroom demonstration of how to use. The advantages of Pulse Ox are no heating or skin prep of the site; no calibration and multiple monitoring sites are available. The disadvantages are that motion artifacts are picked up in moving patients and it does require a pulsating arteriolar bed. Would this instrument work accurately in cardiac arrest, CP bypass surgery? intense vasoconstriction or severe hypovolemia?

2. Transcutaneous monitoring

--Diagram of Hair Pin Capillary Loop Perfusing the skin

Heat Induced Hyperremia-By heating the skin above normal body temperature(37 0C), more blood diffuses through the capillaries thus allowing O2 and CO2 to more readily more to the skin’s surface.

Equipment-Capnograph with calibration gas((calibration for high and low O2 and CO2 levels)

--instrument turned on and sensor allowed to warm up. Once reaches desired temperature( between 42 and 44 0C), calibration done. Sensor membrane changed if necessary (see classroom demonstration). Desired temperature, time in one spot, high and low alarms set.

--double sticky disc applied with electrolyte solution to make better skin contact.

--typical temperature range 42 0c(infant) to 44 0C(adult)

--typical time in one spot 2 hours (premature baby) to four hours(adult) Premies may burn very easily thus put sensor on for short time (1/2 hour to one hour) and check spot)

--the best place to put on a patient is a flat hairless area with a little bit of fat so intercostals spaces, abdomen or thighs are the best spots.

--the capnograph sensor is a dual electrode to measure PaO2 and PaCO2. it incorporates both Clarks electrode (PaO2) and Severinghaus’s electrode (PaCO2)(see Mosby, p.310)

--Make sure it correlates with an ABG.

--Limitations of transcutaneous monitoring—1. Shock (hypoperfused state). 2. Vasoactive drugs (vasocontrictors and vasodilators)-Example Dopamine or Nitro glycerin. 3. Thickness of the patient’s skin (less accurate in adult’s)

3. End Tidal CO2 Monitoring-Capnography

a) Definition-Capnography is recording the changing levels of expired CO2. CO2 and water absorb infrared light, therefore we remove the water via filter. The higher the level of CO2, the more infrared light will be absorbed.

b) Factors that affect the EtCO2

1. cellular production of CO2-varies with the patient's metabolism.

2. Transport of CO2 from the cells to the lungs-varies with the patient's circulation

3. Elimination from the lungs-central/peripheral chemoreceptors

c) Physiology

1. Any disease/event that causes alveolar hypoventilation will increase the EtCO2, Ex. Neurological trauma, drugs, Asthma, Diffusion Defect

2.decreased EtCO2= decreases pulmonary blood flow-Suspect

Emboli!

d) Instrumentation

1. Aspirating devises (Sidestream)-Novametrix-older models

2. Mainstream devises (non-aspirating)-Hewlett Packard, Nellcor-all recent ones are of this type.

e) Math-How to convert % to torr

1. Normal EtCO2 is 5.6% =.056 x 713= 40 mm Hg

f) Normal waveform-Similar to the Single Breath N2 Washout Curve, but the patient doesn't exhale to RV

A-dead space gas B-Deadspace plus alveolar gas C-Alveolar gas D-Peak expired CO2-plateau F-rebreathing-curve does not return to base line

g) ABG Correlation with EtCO2-should be within 3-10 mm Hg. If greater, don't use monitor (see factors under b for explanation).

h) Technique-Chest Squeeze-Watch out for recent feeding, surgical sites, chest tubes, CVP or arterial lines

1. How do you get a Newborn Vital Capacity-Cry

2. Whether on or off the vent-squeeze the chest at the end of inspiration

Apnea monitoring and GERD-see Sleep multimedia program (Pediatrics)

Part VI--Goals of 02 Therapy and Types of Hypoxia- The goals of 02 therapy are 1. to Rx Hypoxia and Hypoxemia, 2. to decrease the Work of Breathing and 3. to decrease Myocardial Work.

Hypoxic Hypoxia-a condition that results from reduced Alveolar 02 tension. Causes are a low ambient 02 tension or Hypoventilation.

Low ambient 02 tension comes from a low concentration of 02 at 1 ATM, i.e. high altitudes. Hypoventilation comes from not enough 02 flowing into the alveoli ',for example, trauma to the respiratory centers, COPD).

Circulatory Hypoxia-a condition resulting from inadequate bloods flow to the tissues or cells. Systemic conditions that can bring this on are Shock or Congestive Heart Failure. Local conditions that can cause this are Arterial/Venous Obstruction (Pulmonary Embolism).

Histotoxic Hypoxia-Foreign substances in the blood prevent 02 perfusion into the body's cells or cellular utilization of 02. An example would be cyanide poisoning that blocks mitochondrial receptor sites (cristae) for 02.

Anemic Hypoxia-a condition of decreased 02 content of the blood due to decreased hemoglobin levels or hemoglobin's inability to transport 02. Examples are anemia or CO inhalation from fires or leaky mufflers.

Four Causes of Hypoxemia-1. V/Q Defect 2. Hypoventilation 3. Diffusion Defects 4. Shunt.

V/Q Defect-due to a mismatch between the two caused by CardioPulmonary Diseases. The result is that 02 doesn't get into the capillaries or to the tissues.

Hypoventilation-diminished ventilation to the alveolus due to pulmonary trauma or neuromuscular disease.

Diffusion Defects-pulmonary fibrosis, granulomas, interstitial or alveolar edema. These prevent the normal transport of 02 from the alveoli to the bloodstream.

Shunting-Arterial/Venous connection with no blood perfusing the alveolus.

Effects of Hypoxia-1. Increased Respiratory rate, increased VT, increased VE. 2. Increased tachycardia and Cardiac Output, Vasodilatation of the Brain vessels, Vasoconstriction of the Pulmonary Vessels.

When we give 02-How does it affect each Hypoxia

1. Hypoxic Hypoxia--responds best to 02 as we immediately increase 02 tension in the alveolus and the blood.

2.Circulatory Hypoxia-responds poorly to 02. No matter how much 02 is in the blood, the blood isn't getting to the tissues.

3.Histotoxic Hypoxia-won't respond at 1 ATM of pressure.--cells unable to utilize the 02 available--Hyperbaric chamber needed.

4.Anemic Hypoxia-you can saturate whatever Hb is available. but it still may not be sufficient to meet the patients needs. Give whole blood or packed RBC's.

Circulatory, Histotoxic and Anemic Hypoxia can all result in Refractory Hypoxemia.

Part VII—Specialty gases

Hyperbaric 02 Therapy--There are two types: 1. A monoplace chamber for one person that delivers 100% 02 at up to 3 ATMs pressure. Similar to a one-man submarine; 2. an expensive multiplace room that holds many people and can dive to many ATMs.

ABG's at 3 atms-Pa02=1800-1900 mm Hg.

A. Physiological Effects of high Pa02--l. new capillary bed formation 2. arteriolar constriction 3. alteration of growth of aerobic and anaerobic organisms.

B. Physiological Effects of increased P.-decreased in the size of the bubbles dissolved in the blood, therefore able to reverse the "Bends" or Decompression Sickness.

C. Harmful Effects of Hyperbaric 02-1. CNS Toxicity--convulsions, sweating, pallor and restlessness. 2. Pulmonary Toxicity--the breathing of 100% 02 under increased atmospheres leads quickly to symptoms-cough, dyspnea, chest tightness. 50% 02 for extended periods of time appears to be safe.

D. Clinical Applications of Hyperbaric 02--l. CO or cyanide poisoning 2. Decompression Sickness or Gas Embolism 3. Skin

grafts, smoke inhalation, thermal burns 4. acute peripheral arterial insufficiency and poor wound healing 5. intestinal obstruction 6. refractory osteomyelitis and radionecrosis of bone and soft tissue.

Helium Therapy--comes from the deep mines in the Southwest, therefore it's expensive and must be conserved. Physiologically, it neither participates nor interferes with any bodily process, as it is inert. It is orderless, tasteless, non-combustible, nonexplosive, poorly soluble.

He has an extremely low density, therefore it is very ineffective at transporting drugs or humidity (similar to anesthetic gases). However, due to its low density, it can easily negotiate airway obstructions(review Graham's Law). The result are that when He is mixed with any other gas, the density of the mixture is low, so it can ventilate the lunges with minimal effort. The commercially available mixtures are 80% He/20% 02 and 70% He/30% 02.

Clinical Uses of He Therapy are in extremely severe Bronchial asthma and COPD. When the patient is very hypoxic and has increased Work of Breathing, Helox mixtures can get 02 to the tissues. Helox is also used commonly in children with severe airway obstruction.

When giving Helox, a tightly fitting Non-Rebreather Mask or an artificial airway must be in place to prevent leaks. As He has a different density than 02, we must use a flowmeter correction factor if we have to use 02 flowmeters to administer Helox.

80/20 mixture--1.8 x reading on 02 flowmeter 70/30 mixture--l.6 x reading on 02 flowmeter

Only adverse side effect of Helox is a high pitched distortion of the human voice. This must be considered in the conscious non-intubated patient.

Carbon Dioxide Therapy or Carbogen--C02 will not support combustion (inert) nor will it maintain life. It is 1.5 times as heavy as air, colorless, orderless.

1. The Physiological Response to C02--A. Respiratory Centers located in the medulla oblongata are stimulated with up to 10%, but depressed by C02 mixtures >= 10%. Review the effects on VE' B. Circulation--direct stimulation of the Cardiovascular centers of the brain--increased BP up to 40 mm Hg (systole), increase HR up to 20 beats per minute, increased ionotropic effects(increase in the force of contraction of heart muscle), constriction of the vascular beds supplied by the sympathetic nervous system(blood is divert from non-essential organs to the brain). If C02 is increased locally, vasodilatation of the blood vessels takes place as in exercising muscle or transcutaneous C02 monitoring.

C. CNS response--In low concentrations, it causes mental depression, while in high concentrations, it causes convulsions and loss of consciousness. We can give Carbogen only to patients with a responsive respiratory center, otherwise fatal hypercapnia will ensue. For example, we would not give this to a patient with COPD due to his respiratory centers decreased response cc., C02 and also the hyperventilation would cause increased WOB.

D. How we use Carbogen Clinically--1. to improve cerebral blood flow in an elderly patient with a massive stroke (CVA)-the results are usually less than spectacular due to arteriosclerosis of the remaining brain vessels. 2. Overcome Hyperventilation and prevent postoperative atelectasis-C02 stimulates hyperventilation therefore better V/Q ratio. Newer techniques are available that are much safer. 3. Singulation (Hiccups)--This condition is caused by the spasmodic contraction of the diaphragm against a closed glottis due to an irritated phrenic nerve. In patients who are post-op or have debilitating diseases, gastric distention and metabolic toxins may cause unrelenting hiccups. C02 appears to work by initiating rhythmic discharges to the diaphragm that are so strong they override the spasmodic contractions from the hiccups. 4. Uses in Philadelphia--Scheiss Eye Institute at Presby--given as a retinal vasodilator to improve eye sight post cataract surgery

E. Ways Carbogen is administered. 5% C02/95% 02 for +/- 10 minutes--therapist must stay with the patient at all t1mes-Why? b. >5% C02-M.D. must be present at all times. administer with a well fitting Non-Rebreather Mask.

F. Potential Side Effects--Headache (HA), dizziness due to a drop in diastole blood pressure, dyspnea, palpitations, dimming vision, muscle tremors, parathesias, coldness of extremities, mental depression. If any of these appear, notify M.D. Toxic Symptoms--stop TX immediately-dyspnea, nausea and vomiting, disorientation, increased systolic BP. Carbogen--Danger-uses with extreme care!!

At CHOP--given to LV Hypoplastic Surgery candidates to decrease pulmonary blood flow and edema post-op.

Part VIII—Polysomnography

1. Stages of sleep

A. Non-REM Sleep-Quiet or slow wave sleep. Begins immediately and generally lasts for 60-90 minutes with movement into and out of the four stages of Non-REM sleep. Individuals can move into REM sleep during any stage but most common during Stages 1 & 2.

Four stages of sleep—Stages 1 and 2

Increasing and decreasing ventilatory rate and tidal volume with brief periods of apnea often seen.

Stages 3 and 4-Ventilation becomes slow and irregular with minute volume 1-2 liters less than in quiet wakeful ventilation. As a result, PaCO2 levels are 4-8 mm Hg higher, the PaO2 levels are 3-10 mm Hg lower, and the pH is .03 to .05 units lower (See pp793-795. Mosby)

B. REM Sleep(Active or Dreaming Sleep). Last 5-40 minutes and occurs every 60-90 minutes. The REM period lengthens and becomes more frequent towards the end of the night’s sleep. It accounts for 20-25% of the sleep time.

Sleep related hypoventilation and more frequent periods of apnea are usual. Normally individuals experience 5 periods of apnea or less an hour, lasting up to 15-20 seconds, without any adverse effects.

Hypercapnic and hypoxic ventilatory drive is reduced.

Heart rate becomes irregular.

Rapid eye movement and dreaming occurs.

Paralysis of movement occurs with skeletal muscle paralysis affecting the arms, legs, intercostals and upper airway muscles.

This affects ventilation in two ways:

1) Intercostal muscle movement is paradoxical, creating a decrease in FRC(Functional Residual Capacity).

2) The loss of tone in the upper airway may cause airway obstruction.

The negative pressure produced by the flattening of the diaphragm during inspiration brings the vocal cords together, Collapsing the pharyngeal wall and sucking the tongue back into the pharyngeal airway.

In order to evaluate how series sleep apnea is, we need to know the following definitions:

1.Apnea-complete cessation of air flow for 10 seconds or greater.

2.Hypopnea-reduction of airflow by 50% for 10 seconds or more with a physiological consequence (Ex, decrease saturation recorded on a pulse oximeter.

3.Apnea/Hypopnea Index—the number of apneic and hypopnea periods/the number of hours of sleep. Sleep apnea is considered present if the AHI is more than 5per hour.

Some patients have as many as 500 episodes per night.

Obstuctive Sleep Apnea(OSA)-caused by the anatomic obstruction of the upper airway in the presence of continued ventilatory effort(See fig 15-8, p 802, Mosby) Patient is quiet and still, followed by increasingly difficult efforts to inhale, ending in intense snoring (fricative Breathing). (See video from Sleep Multimedia program).

--more frequently seen in males than females (8: 1 ratio)with the approach of middle age occurring in 1-4% of the male population.

--obesity with a short neck increases the possibility of OSA because of narrowing of the pharyngeal airway (Pickwickian syndrome). Nor all patients with OSA are obese.

Neck measurements in males > 17 inches and >16 inches in women are a risk factor for OSA.

Central Sleep Apnea (CSA)—occurs when the respiratory center of the medulla fail to send signals to the respiratory muscles. As opposed to OSA, there is cessation of airflow at the nose and mouth, along with cessation of inspiratory efforts (i.e., the diaphragm doesn’t move). See Mosby. Pp 802-803, Figures 15-8,15-9.

Mixed Sleep Apnea-combination of OSA and CSA. It usually begins as central and progress to the obstructive type. It’s treated like the obstructive type.

Diagnosis of Sleep Apnea—

A. Polysomnographic Sleep Studies

1. EEG and Electrooculogram to identify sleep stages

2. Flow sensing devise to determine airflow into and out of the nose and mouth.

3. EKG to identify arrhythmias

4. Impedence Pneumography, intercostals electromyography or esophageal manometry to monitor ventilatory rate and effort.

5. Pulse oximetry or transcutaneous oxygen monitoring for O2 saturation.

6.Evaluation of brain stem lesions if CSA is suspected.

7. CT evaluation of upper airway(OSA).See Mosby, p798, Clinical practice guidelines 15-1.

B Additional Studies

1. Spirometry-upper airway obstruction.

2. Abg’s including Hb/Hct and COHb.

3. Thyroid function-Hypothyroidism implicated in both types.

4. CXR

Management of Sleep Apnea

A. Weight reduction

B. Sleep posture

C. O2 Therapy

D. Drug Therapy—

1. for OSA REM inhibitors such as Vivactil(protriptyline hydrochloride)

2. for CSA Diamox (Acetazolamide)-respiratory stimulant

E. Surgery

--Tracheostomy/Endotracheal intubation in an emergency

--Palatopharygoplasty-increase the diameter of the pharyngeal space.

--Mandibular Advancement (ex micrognathia) OSA can be due to mandibular regression.

F. Mechanical Ventilation

--CPAP is gold standard to Rx OSA and Mixed.

--CMV-when acute respiratory failure develops from OSA or CSA.

--Negative Pressure Ventilation(Iron Lung)-CSA

--Phrenic Nerve Pacemaker-CSA

--Dental Appliances that reposition the tongue and jaw to prevent the tongue from blocking the airway-experimental.

Women and Sleep-Menstrual Cycles, Pregnancy and Menopause

Restless Leg Syndrome

Sleep and Aging