Lung volume and capacities

Question 1

Tidal volume (TV)

Answer 1

Volume of air entering or leaving lungs during a single breath
500 ml

Question 2

Inspiratory reserve volume (IRV)

Answer 2

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume

[3000 ml]

Question 3

Inspiratory capacity (IC)

Answer 3

Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + IV)
[3500 ml]

Question 4

Expiratory reserve volume (ERV)

Answer 4

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
[1000 ml]

Question 5

Residual volume (RV)

Answer 5

Minimum volume of air remaining in the lungs even after a maximal expiration
[1200 ml]

Question 6

Functional residual capacity (FRC)

Answer 6

Volume of air in lungs at end of normal passive expiration
(FRC = ERV + RV)
2200 ml

Question 7

Vital capacity (VC)

Answer 7

Maximum volume of air that can be moved out during a single breath following a maximal inspiration
(VC = IRV + TV + ERV)
4500 ml

Question 8

Total lung capacity (TLC)

Answer 8

Maximum volume of air that the lungs can hold
(TLC = VC + RV)
5700 ml

Question 9

Forced expiratory volume in one second (FEV1)

Answer 9

Volume of air that can be expired during the first second of expiration in a VC determination

Question 10

Normal Spirogram: lung operates at “half full

Answer 10

Question 11

Answer 11

Abnormal spirograms associated with obstructive and restrictive lung diseases.

Question 12

Abnormal spirograms associated with obstructive and restrictive lung diseases.

Answer 12

• Because a patient with obstructive lung disease experiences more difficulty emptying the lungs than filling them, the total lung capacity (TLC) is essentially normal, but the functional residual capacity (FRC) and the residual volume (RV) are elevated as a result of the additional air trapped in the lungs following expiration.
• Because the RV is increased, the vital capacity (VC) is reduced.
• With more air remaining in the lungs, less of the TLC is available to be used in exchanging air with the atmosphere.
• Another common finding is a markedly reduced forced expiratory volume in one second (FEV1) because the airflow rate is reduced by the airway obstruction.
• Even though both the VC and the FEV1 are reduced, the FEV1 is reduced more markedly than is the VC.
• As a result, the FEV1/VC% is much lower than the normal 80%; that is, much less than 80% of the reduced VC can be blown out during the first second.
• In restrictive lung disease, the lungs are less compliant than normal.
• Total lung capacity, inspiratory capacity, and VC are reduced because the lungs cannot be expanded as normal.
• The percentage of the VC that can be exhaled within one second is the normal 80% or an even higher percentage because air can flow freely in the airways.
• Therefore, the FEV1/VC% is particularly useful in distinguishing between obstructive and restrictive lung disease. - Also, in contrast to obstructive lung disease, the RV is usually normal in restrictive lung disease.

Question 13

Pulmonary ventilation (ml/min) =

Answer 13

tidal volume (ml/breath)  x 
respiratory rate (breaths/min)