PSC 2019 Lecture 2

Question 1

What are the 3 functions of the lungs?

Answer 1

Uptake of oxygen
Elimination of CO2
Maintenance of acid - base stability

Question 2

In perfect Gas exchange at rest what is the pulmonary blood flow (Perfusion Q) and Ventilation

Answer 2

Perfusion = 5 Litres/minute
Ventilation = 5 Litres/minute

Question 3

What are the causes of uneven perfusion and ventilation?

Answer 3

Normal lungs: Gravity
Abnormal Lungs: patchy disease of airways, alveoli, vasculature
Consequences: efficiency of gas exchange depends on the dispersion of Ventilation/Perfusion ratio throughout the lungs

Question 4

What does regional tidal expansion refer to?

Answer 4

Upper parts of lungs are less ventilated than lower parts due to alveoli being bigger in the upper parts as a result of gravity (alveolar distension)

Question 5

what are the 4 mechanisms of Hypoxaemia

Answer 5

Low inspired oxygen
Hypoventilation
Impaired diffusion
Ventilation/perfusion mismatching

Question 6

What is Hypercapnia and what are its causes?

Answer 6

Hypercapnia is high levels of CO2
Causes: Hypoventilation, neuromuscular diseases, chest wall deformity (scoliosis), sedation

Question 7

what are the factors affecting DLCO

Answer 7

Distribution of inspired gas
integrity and number of alveoli
thickness of alveolar-capillary membrane
function of pulmonary capillaries
Hb conc