Lange Ch22

Question 1

How much is physiologic dead space? Per weight?

Answer 1

1 cc per lb. so average physiologic dead space is 150cc

Question 2

Bohr equation for dead space to tidal volume ratio Vd/Vt

Answer 2

Vd/Vt = (PACO2 - PeCO2) / PACO2. Avg ratio is 33% for 150/450. PeCO2 is mixed expired

Question 3

Relationships of Pa, Pv, and PA in the 3 lung zones

Answer 3

Zone 1: PA > Pa > Pv, high V/Q
Zone 2: Pa > PA > Pv
Zone 3: Pa > Pv > PA, low V/Q
Ventilation and perfusion improve in dependent areas

Question 4

How to calculate PAO2?

Answer 4

PAO2 = FiO2*(760-47) - (PCO2 / 0.8)

PAO2 ~ FiO2 * 6

Question 5

MC mechanism of hypoxemia

Answer 5

Increased A-a gradient caused by R->L shunt, V/Q mismatch, low MvO2 (low cardiac output, high O2 consumption, anemia)

Question 6

Venous admixture (physiologic shunt) equation

Answer 6

Qs/Qt = (CcO2 - CaO2) / (CcO2 - CvO2)

Normal shunt is 5%

Question 7

Total oxygen delivery (DO2) equation

Answer 7

DO2 = cardiac output * arterial O2 content

Question 8

Oxygen consumption VO2 equation

Answer 8

VO2 = cardiac output * (arterial O2 content - mixed venous O2 content)

Question 9

Oxygen content equation

Answer 9

(O2sat * hgb * 1.31) + (PO2 * 0.003)

Question 10

Mixed venous oxygen content equation

Answer 10

CvO2 = CaO2 - (VO2 / Qt)
VO2 oxygen consumption ~ 250 mL/min
Qt cardiac output

Question 11

Basic breathing rhythm originates from what part of brain?

Answer 11

Medulla

Question 12

Effect of anesthesia on peripheral ventilatory response to hypoxemia

Answer 12

Abolished response