Pulmonary Circulation

Question 1

Pulmonary Circulation vs. Systemic (1 similarity, 3 differences, 2 results)

Answer 1

Must be equal in magnitude, but pulmonary has:
Lower pressures/resistance
Significant resistance in capillaries, not just arterioles
Thinner more compressible walls (low P)
So bigger effects of gravity/passive forces
Low hydrostatic pressure reduces filtration across capillaries (prevents edema in lungs)

Question 2

Fick Principle

Answer 2

VO2 = Qt x (Cao2 - Cvo2)

Question 3

Resistance =

Answer 3

Pressure gradient/blood flow (PVR = about 1.7 mm Hg/L/min)

Question 4

Magnitude vs. Distribution

Answer 4

Magnitude of pulmonary circulation determined by cardiac output and shit, but PVR controls distribution and how much work the right heart must do to drive blood flow

Question 5

Zone 1,2,3 PA, Pa, and Pv relationships

Answer 5

1: PA > Pa > Pv (closed)
2: Pa > PA > Pv (compressed)
3: Pa > Pv > PA (blood flow)

Question 6

Ventilation Distribution

Answer 6

Greater at base bc has to be kept standard with perfusion. Base intrapleural pressures greater (less neg) than apical bc small fluid column. On inspiration, same pressure change throughout but the change in volume is greater starting from removing greater pressures

Question 7

Vascular Pressure and PVR

Answer 7

Increase in pressures lead to decrease in PVR via recruitment and distension of alveolar capillaries (and large increase in flow)

Question 8

Positive Pressure Ventilation Effect on Capillaries

Answer 8

Compress capillaries in alveoli making it harder for RH

Question 9

PVR by Lung Volume

Answer 9

Minimal at functional residual capacity. As it gets bigger, alveolar vessels compressed so their resistance increases (although extraalveolar vessels expand bc intrapleural pressure decreases on inspiration). On expiration, opposite happens and extra alveolar vessel resistance increases

Question 10

Low pO2 and acidic blood pH (high CO2)

Answer 10

Pulmonary a.s constrict, bypassing poorly ventilated regions. Good usually and before birth, but problem w/ high elevations

Question 11

3 Reasons Interstitial Edema Develops before Alveolar

Answer 11

Tissue hydrostatic pressures more negative outside interstial rather than alveolar vessels
Endothelium more water permeable than alv epithelium
Type II cells pump Na out of alv and water follows

Question 12

2 Chemical Sensitivities of Pulmonary Circulation

Answer 12

Constricted by endothelin

Dilated by NO