Pulmonary Concepts and Phys

Question 1

Normal A-a gradient

Answer 1

5-15

Question 2

Normal A-a gradient with hypoxemia

Answer 2

Indicates Alveolar hypoventilation: high altitude, suppressed central respiratory drive, decreased inspiratory capacity

Question 3

Increased A-a gradient with hypoxemia

Answer 3

over 15: indicates diffusion impairments (ARDs, emphysema)

Question 4

Low PaO2 and its causes

Answer 4

Hypoxemia (low O2): low partial pressure of inspired O2, alveolar hypoventilation, diffusion impairments, ventilation/perfusion mismatch, right to left shunting

a) low partial mmHg of inspired O2 + alveolar hypoventilation = normal A-a
b) others abnormal A-a

Question 5

calculate alveolar ventilation

Answer 5

Tidal volume - dead space = alveolar vent

minute venti = tidal vol x RR

Question 6

calculate dead space

Answer 6

physiological dead space = tidal vol x ((PaCO2-PECO2)/PaCO2))