13 spirometry

Question 1

What are the 2 main ways lung volumes can be measures, and what methods might be used for each?

Answer 1

Direct (piston spirometer or water ball spirometer)

indirect (peak flow meter, pneumotachograph)

Question 2

What principle does a pneumotachograph use?

Answer 2

P = flow x R, because R is constant, a change in pressure is proportional to flow

Question 3

What are the 3 options for plotting the variables?

Answer 3

flow-volume loop
flow vs time (peak expiratory flow rate)
volume v time (spirogram)

Question 4

How would you measure flow v time?

Answer 4

peak expiratory flow rate
inspire to TLC, the forcibly exhale for as long as possible through a peak flowmeter, recording a single value for maximum airflow rate

Question 5

What effect would a restrictive lung disease have on PFT’s?

Answer 5

reduced lung volumes, reduced SA for gas exchange

therefore vital capacity reduced

Question 6

What effect would an obstructive lung disease have on PFT’s?

Answer 6

increased airway resistance

resistance increases with 1/r^4, so a lower rate

Question 7

What lung disease shows both restrictive and obstructive issues?

Answer 7

emphysema
early - loss of alveolar structure
later - inflammation