5. Testing for V/Q Mismatch
Nonuniform gas distribution
Alveolar plateau of closing volume test
Nitrogen washout
Trapped gas
Single breath of 133Xe
99mTc-labeled DTPA (diethylene triamine pentaacetic acid)

9. Testing for V/Q Mismatch
Nonuniform pulmonary blood flow
Pulmonary angiogram
Lung scans:
131I-labeled MAA
99mTc-labeled MAA
133Xe

10. Testing for V/Q Mismatch
Mismatched V/Q
Physiologic shunts : shunt equation
Anatomic
Intrapulmonary
Absolute
Shuntlike states (low V/Q)
Physiologic dead space : Bohr equation
Alveolar : (a-A)Dco2
(A-a)Do2
Lung scans after inhaled and infused markers
Multiple inert gas technique . .

12. Physiologic Shunt Physiologic = Anatomic + Intrapulmonary Shunt Shunt
Absolute Shunt
Shuntlike States

14. Shunt Equation QS Qt .
CC´ – Ca O2
CC´ – Cv =

15. PHYSIOLOGIC DEAD SPACE
Anatomic Dead space
Alveolar
Dead space = +

16. Bohr Equation
Pa PE VD
CO2
CO2
CO2 = VT Pa
CO2

17. Causes of Increased Alveolar-Arterial Oxygen Partial Pressure Gradient
Increased right - to left shunt
Anatomic
Intrapulmonary
Increased ventilation-perfusion mismatch
Impaired diffusion
Increased inspired partial pressure of oxygen
Decreased mixed venous partial pressure of oxygen
Shift of oxyhemoglobin dissociation curve

22. . . . . vol VA Q VA / Q Po2 Pco2 PN2 O2 CO2 pH O2 CO2 (%) (liters/min)
(mmHg)
content (ml/100ml)
in out (ml/min) 7
.24
.07
3.3
132 28
553
20.0 42
7.51 4 8 13
.82
1.29
0.63 89 42
582
19.2 49
7.39 60 39