Shunt Equations Problems

 

 

  1. QT (CO) = VO2 ml/min

liters/min      [Cao2 – CVO2] [10]

 

 

2.        QT = Qaterialized + Q sp (shunt)

             

 

 

3.        Qsp = Cco2 – Cao2                          Equation for Physiologic Shunt

      QT       Cco2 – Cvo2

 

 

  1. Qsp = Cco2 – Cao2 Good         Equation for Estimated Shunt--Stable Metabolic Rate and Cardiovascular Status

            QT       3.5 + (Cco2 – Cao2)

           

             

            Problem #1 Determine Phis Shunt given following information:

            Pao2 = 90 mmHg, Pvo2 = 40 mmHg ,Sco = 100%

            Hb = 15 gms, SVO2 = 70%

            Sao2 = 95% for PAO2

Given  FIO2 = .21

PB = 760         PaCO2 = 40      

PH20 = 47       r = .8               

Figure out 1) CC02, 2) CaO2, 3) CVO2, 4) Phis Shunt 5) Est Shunt 6) A – VO2 Diff

 

  1. CCO2 = (PAO2 x .003) + (Hb x 1.34 x Sat %)

 

a.        PAO2 = ( PB – PH20) FIO2 – Paco2 / r

             = (713) (.21) – 40 /  8

             = 149.73 – 50 = 99.73

 

  1. CCO2 = (99.73 x .003) + (15 x 1.34 x 1.0)

(.299) + (20.1) = 20.399 vol %

 

 

2. Cao2 = (Pao2 x .003) + (Hb x 1.34 x Sat)

= (90 x .003) + (15 x 1.34 x .95)

= (.27) + (19.09) = 19.36 vol %

 

 

3. Cvo2 = (Pvo2 x .003) + (Hb x 1.34 x Sat)

= (40 x .003) + (15x 1.34 x .70)

= (.12) + (14.07) = 14.19 vol %

 

 

4. Qs = Cco2 – Cao2 = 20.39 – 19.36 = 1.03

QT Cco2 – Cvo2 20.39 – 14.19 6.2

= .166 = 16.6%

 

 

5. Qs =      Cco2 – Cao2   =                     1.03                 =         1.03 /4.53    =22.7 % Shunt

QT Est       (3.5) + (Cco2 – Cao2)              (3.5) + (1.03) 4.53

 

6) A – V02 Diff.  = 19.36 vol% -14.19 vol%  = 5.17 Vol%

 

#2 Given Hb = 13 gms, Pao2 = 86 mmHg ,Sao2 = 90% ,FI02 = .4, Pa C02 = 50 mmHg,

r = .8, PB = 760 mmHg, Pvo2 = 65 mmHg, SV02 = 70%

 Figure out 1) Cco2 2) Cao2 3) Cvo2 4) Phis Shunt 5) Est. Shunt

 

  1. Cc02 = (PA02 x .003) + (Hb x 1.34 x Sat%)

 

a.        PA02 = (PB – PH20) (FI02) – Paco2 / r

= (713) (4) – 50 / .8

= 285.2 – 62.5º = 222.7 mm Hg

b. CcO2 = (196 x .003) + (13 x 1.34) x 1)

= (.688) + (17.42) = 18.08 vol %

 

 

2. Ca02 = (Pa02 x .003) + (Hb x 1.34 x Sat%)

             = (86 x .003) + (13 x 1.34 x .9)

             = (.258) + (15.678) = 15.936 vol %

 

 

3. CV02 = (Pv02 x .003) + (Hb x 1.34 x Sat) %

= (65 x .003) + (13 x 1.34 x .7)

= (.195) + (12.194) = 12.389 vol %

 

 

4. Qs    =    Cc02 – Ca02       = 18.08 – 15.936                   = 2.144

QT       Cc02 – CV02          18.08 – 12.389                       5.69

= 37.6 =38% Shunt

 

5. Est Qs =            Cc02 = Ca02 =                        2.072 =                        2.144 = 38%

             QT                  3.5 + (Cc02 = Ca02)              (3.5 + 2.144)               5.644

 

 6. (A-V) Difference  = CaO2 –CvO2  = 15.936 vol% – 12.389 vol%  = 3.54Vol%

 

 Shunt Problem #3  Given the following information:

PaO2 = 60 mm Hg, SvO2 = 50%, SCo2 = 100% Hb = 8gms, FIO2 = 40%, Sao2 = 80%, PaCO2 = 55, PVO2 = 30 mmHg, r = .8

Figure out:  1) CcO2 2) CaO2 3) CvO2 4) Phis Shunt 5) Est Shunt 6, A-V O2 difference

1)         a)CcO2-àPAO2

            PAO2 = (713) (.4)  - 55 / .8  = 285.2 – 68.75 = 216.45

            b) CcO2 = (216.45 x .003) + (8 x 1.34 x 1.0) = (.649) + (10.72) = 11.36 Vol%

 

2. CaO2 = (60 x .003) + (8 x 1.34 x .88) = (.18) + (9.43) = 9.61 Vol%

 

3. CvO2 = (30 x .003) + (8 x 1.34 x.5) = (.09) + (5.36) = 5.45 Vol%

 

4. Qs /Qt = 11.36 -9.61/ 11.36 -5.45  = 17.5 /5.1 =.343 = 34% shunt

 

5. Qs /Qt Est = 11.36 -9.61 /(3.5) + (11.36 -9.6) = 1.75/ (3.5) + (175.) = 1.75 /5.25 =.333 =33.3% shunt

 

6. A-V O2 difference = 9.61 -5.45 =$.16 Vol%

 

Shunt Equations Problems