Distribution (SELF STUDY) of Inspired Gases and Gas Transfer

Question 1

Factors affecting airway resistance

Answer 1

airway smooth muscle
gravity and posture
lung compliance
age
disease

Question 2

Airway smooth muscle

Answer 2

sensitive to neural and chemical stimulation

hyper-responsive - SM contracts and airflow is obstructed

Question 3

Gravity and posture

Answer 3

supine posture better for blood flow distribution

upright - decreased at top, increased at bottom

Question 4

Lung compliance factors

Answer 4

age - increases

disease: emphysema - increases; pulmonary fibrosis - decreases

Question 5

Auscultation of airways

Answer 5

bronchi/large bronchioles - high and turbulent flow velocity, therefore breath sound generated
small bronchioles - flow velocity is laminar
terminal airways - flow occurs via diffusion
small = silent zone

Question 6

Perfusion

Answer 6

process by which deoxygenated blood passes through the lungs and becomes re-oxygenated

Question 7

Ventilation perfusion ratio

Answer 7

Va/Q

ratio of alveolar ventilation to blood flow

Question 8

Normal Va/Q value

Answer 8

Va - 5
Q - 5
ratio - 1

Question 9

Where would the Va/Q value differ?

Answer 9

dead space and shunts

due to gravity

Question 10

Why does Va/Q differ at dead space

Answer 10

normal ventilation, no perfusion
no capacity to carry O2 away or bring CO2 to alveoli
no gas exhange between alveoli and blood, alveoli equilibrates with atmosphere

Question 11

Why does Va/Q differ at a shunt

Answer 11

no ventilation, perfusion normal

no new O2 into system, alveoli equilibrates with venous blood

Question 12

How does gravity affect Va/Q?

Answer 12

apex: decreased blood flow, increased ventilation (2)
base: increased blood flow, decreased ventilation (0.5)

Question 13

In clinic what is Va/Q used to diagnose?

Answer 13

pulmonary embolism

injection (perfusion) and inhalation (ventilation) of radioisotope