Pulmonary Physiology, Gas Pressures & Volumes, Dr. D. Penney




Table 1.01. Standard lung volume values.



Others:

Respiratory minute volume (rest ): 6 liters/min
Alveolar ventilation (rest): 4.2 liters/min
Maximal voluntary ventilation (BTPS): 125-170 liters/min
Timed vital capacity: 83% of total in 1 sec; 97% in 3 sec
Work of quiet breathing: 0.5 kg-m/min
Maximal work of breathing: 10 kg-m/breath
As seen, there are differences between men and women with respect to IRV and ERV, men generally having the larger values. Thus the vital capacity of men is also usually larger. This is mainly due to the larger body mass of men, but probably also because men on average have less body fat, and pulmonary capacity is more a function of lean body mass.

Minute Ventilation does not equal Alveolar Ventilation! Each minute at rest about 6 liters of air moves in and out of the lungs (e.g. 12 breaths/min X 500 ml/breath) but only about 4 L of fresh air gets down into the alveolar sacs. That air which stays in the bronchus, bronchioles, etc. does not participate in gas exchange - it is termed the Anatomic Dead Space. Thus alveolar ventilation is 12 X (500 Tidal Volume - 150 Anatomic Dead Space) = 4200 ml/min).

During periods of maximal work/effort, maximal voluntary ventilation can increase over 20-fold. This is a far greater increase that the heart can achieve in terms of cardiac output.

Various measures of the rate at which the lungs can be filled or emptied are used. Sometimes these are percentage change in 1, 2, 3 minutes, time to 50%, etc.


Last Changed 04/23/00


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