Physiology

Question 1

Changes in lung function in pregnancy

Answer 1

FEV1/FVC/PEFR largely unchanged
FRC, RV decrease
Inspiratory capacity increases

Question 2

Boyle’s law:

Answer 2

Boyle’s Law describes the behavior of gases under varying amounts of atmospheric pressure.
- As a diver rises to surface - volume of gas in lungs increases

Question 3

Calculation for pulmonary ventilation

Answer 3

Tidal volume x respiratory rate

Question 4

Tests of respiratory muscle strength:

Answer 4

Mean Inspiratory Pressure (MIP), maximal sniff nasal inspiratory pressure (SNIP) - measure diaphragm and other inspiratory muscle strength
Mean Expiratory Pressure (MEP) - strength of abdominal and other expiratory muscles

Should request if you suspect patient has a degree of respiratory muscle weakness or PFTs suggestive of respiratory muscle weakness (restrictive pattern, low vital capacity, reduced diffusion capcaity)

Low MIP/SNIP - good negative predicitve value - but low result cannot reliably confirm inspiratory muscle weakness as poor effort common