Lung Function Booklet

Question 1

Explain how to measure peak expiratory flow (PEF)

Answer 1

• Patient takes a full breath in (i.e. TLC) and then exhales as rapidly as possible into a suitable measuring instrument

Question 2

What are the most common measuring instruments of PEF?

Answer 2

• Wright’s peak flow meter: not very precise, portable

- Spirometer: a flow-measuring device with a continuous output, more precise

Question 3

What is the unit of measurement of PEF?

Answer 3

L/min.

Question 4

What is the pattern of normality of PEF?

Answer 4

• 36 y.o. male, height 183cm: 620 (+/- 60) L/min

- Diurnal variation: lower in morning than in evening, should be less than 10%

Question 5

What are the most common measuring instruments of PEF?

Answer 5

• Wright’s peak flow meter: not very precise, portable

- Spirometer: a flow-measuring device with a continuous output, more precise

Question 6

What is the unit of measurement of PEF?

Answer 6

L/min.

Question 7

What is the significance of a abnormal values for PEF?

Answer 7

This suggests airflow obstruction.

Question 8

Describe dynamic lung volumes

Answer 8

• FEV1 and FVC are measured during a forced expiration from TLC to RV (like PEF)
• FEV1:FVC indicates lung volume and airway calibre that allows that air volume to be exhaled

Question 9

What is the most common measuring instrument of DLVs?

Answer 9

Spirometer.

Question 10

Explain how to measure peak expiratory flow (PEF)

Answer 10

• Patient takes a full breath in (i.e. TLC) and then exhales as rapidly as possible into a suitable measuring instrument

Question 11

What is the pattern of normality of PEF?

Answer 11

• 36 y.o. male, height 183cm: 620 (+/- 60) L/min

- Diurnal variation: lower in morning than in evening, should be less than 10%

Question 12

What is the unit of measurement for PEF?

Answer 12

L/min.

Question 13

What is the pattern of normality of DLVs?

Answer 13

36 y.o. male, height 183cm:

• FEV1 = 4.5 (+/- 0.5) L
• FVC = 5.6 (+/- 0.6) L
• FEV1:FVC = 81 (+/- 5%)

Question 14

What is the significance of a reduced value for DLVs?

Answer 14

• Fall in FEV1 and fall in FEV1:FVC suggests airway obstruction
• Fall in FEV1 but FEV1:FVC remain same suggests restrictive ventilatory problem

Question 15

What is the most common measuring instrument of DLVs?

Answer 15

Spirometer.

Question 16

What is the unit of measurement for DLVs?

Answer 16

• FEV1 and FVC are expressed as absolute volume in L
• Sometime expressed as % in reference to predicted values
• Compared to atm T and P (ATPS) or to body T and P (BTPS)
• FEV1:FVC ratio expressed as %

Question 17

What is the pattern of normality of DLVs?

Answer 17

36 y.o. male, height 183cm:

• FEV1 = 4.5 (+/- 0.5) L
• FVC = 5.6 (+/- 0.6) L
• FEV1:FVC = 81 (+/- 5%)

Question 18

What is the significance of a reduced value for DLVs?

Answer 18

• Fall in FEV1 and fall in FEV1:FVC suggests airway obstruction
• Fall in FEV1 but FEV1:FVC remain same suggests restrictive ventilatory problem

Question 19

What is the most common measuring instrument of SLVs?

Answer 19

Apparatus comprises of;

• Two bags: one for initial gas mix, one to collect sample
• A valve to switch between both bags
• A system to remove CO2 from first bag
• An O2 source to add O2 into first bag
• Series of analysers to measure O2, CO2 and inert gas concs

Question 20

What is the unit of measurement for SLVs?

Answer 20

• All in L
• TLC, VC RV, TV, FRC
• RV/TLC

Question 21

What is the unit of measurement for SLVs?

Answer 21

• TLC, VC RV, TV, FRC: litres

- RV/TLC: %

Question 22

What is the pattern of normality of SLVs?

Answer 22

36 y.o. male, height 183cm;

• FRC = 3.7 (+/- 0.7) L
• RV = 1.9 (+/- 0.4) L
• VC = 5.6 (+/- 0.6) L
• TLV = 7.3 (+/- 0.8) L
• RV/TLC = 25 (+/- 0.4) % (increase in obstructive, decrease in restrictive)

Question 23

What is the significance of a reduced value for SLVs?

Answer 23

Obstructive;

• Increased TLC, RV, FRC
• Increased RV/TLC ratio

Restrictive;

• Decrease all
• Normal/low RV/TLC ratio