Pulmonary Physiology

Question 1

What is the aim of breathing?

Answer 1

To get oxygen into the lung and CO2 out of the lung

Question 2

What is required for gas flow in the airways?

Answer 2

A pressure difference (Δ pressure) between any two sections of a tube

Question 3

According to Boyle’s Law, what is the relationship between pressure and volume?

Answer 3

PV = K

Question 4

What happens to pressure during inspiration when lung volume increases?

Answer 4

Pressure decreases

Question 5

What is intrapulmonary pressure during normal breathing between breaths?

Answer 5

Atmospheric pressure (760 mmHg; respiratory pressure=0)

Question 6

What happens to intrapleural pressure during inspiration?

Answer 6

Intrapleural pressure decreases

Question 7

What are the two other factors that contribute to ventilation?

Answer 7

• Resistance
• Compliance

Question 8

How does smooth muscle contraction affect airflow resistance?

Answer 8

It alters resistance to airflow

Question 9

What is lung compliance?

Answer 9

The stretchability and ease with which lung expands

Question 10

What determines lung compliance?

Answer 10

• Elastic properties
• Surfactant

Question 11

What is the effect of loss of compliance on the lungs?

Answer 11

Stiff lung occurs as a result of fibrosis or scarring

Question 12

What does an increase in lung compliance indicate?

Answer 12

Emphysema, due to loss of elastic properties

Question 13

What is the role of surfactant in the alveoli?

Answer 13

Reduces surface tension to prevent alveolar collapse

Question 14

What does Laplace’s Law describe?

Answer 14

Pressure inside = 2 x Surface Tension / Radius

Question 15

What is the consequence of a lack of surfactant in newborns?

Answer 15

Respiratory Distress Syndrome due to low lung compliance

Question 16

What is anatomic dead space?

Answer 16

Volume of air in conducting airways that does not participate in gas exchange (150 ml)

Question 17

What is the formula for calculating alveolar ventilation?

Answer 17

Alveolar ventilation = (tidal volume - dead space) x frequency

Question 18

What is FEV1/FVC used to differentiate?

Answer 18

Between obstructive and restrictive lung diseases

Question 19

What does a FEV1/FVC ratio of 0.5 suggest?

Answer 19

Obstruction

Question 20

What are the two main components of the work of breathing?

Answer 20

• Elastic recoil of the lungs and chest wall
• Resistance to airflow

Question 21

What three things are required for efficient external respiration?

Answer 21

• Surface area of structure
• Partial pressure gradient between alveoli and capillaries
• V/Q match

Question 22

What is the significance of blood pH in relation to CO2 levels?

Answer 22

Blood pH needs to be constant; PCO2 cannot change that much

Question 23

What are the two types of chemoreceptors involved in breathing control?

Answer 23

• Central chemoreceptors
• Peripheral chemoreceptors

Question 24

What do central chemoreceptors primarily respond to?

Answer 24

Changes in H+ associated with CO2 levels in the cerebral spinal fluid

Question 25

How does hemoglobin function in oxygen transport?

Answer 25

Binds O2 in response to high PO2 in the lungs and exhibits cooperative binding

Question 26

What is the composition of oxygenated blood?

Answer 26

1L contains 200 ml of O2, with 197 ml bound to Hb and 3 ml dissolved in plasma

Question 27

What happens to hemoglobin saturation at low PO2 levels?

Answer 27

Hb releases O2 more readily to tissues that need it

Question 28

What is the role of the medulla in respiration?

Answer 28

Generates the cycle of inspiration and expiration

Question 29

What is the effect of exercise on oxygen consumption?

Answer 29

Increases due to factors like lactate, temperature, DPG, and PCO2

Question 30

What does the term V/Q matching refer to?

Answer 30

The balance between ventilation and perfusion in the lungs