Normal Dead Space Volume. The normal dead space air in a young adult man is about 150 milliliters. This increases slightly with age.
Alveolar ventilation per minute is the total volume of new air entering the alveoli and adjacent gas exchange areas each minute. It is equal to the respiratory rate times the amount of new air that enters these areas with each breath.
where VA is the volume of alveolar ventilation per minute, Freq is the frequency of respiration per minute, VT is the tidal volume, and VD is the physiologic dead space volume.
Thus, with a normal tidal volume of 500 milliliters, a normal dead space of 150 milliliters, and a respiratory rate of 12 breaths per minute, alveolar ventilation equals 12 x (500 - 150), or 4200 ml/min.
Alveolar ventilation is one of the major factors determining the concentrations of oxygen and carbon dioxide in the alveoli. Therefore, almost all discussions of gaseous exchange in the following chapters on the respiratory system emphasize alveolar ventilation.
Functions of the Respiratory Passageways
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