LUNG VENTILATION PATTERNS DETERMINED BY ANALYSIS OF NITROGEN ELIMINATION RATES; USE OF THE MASS SPECTROMETER AS A CONTINUOUS GAS ANALYZER 1

Abstract

The ventilation of the lung in human subjects is studied by measuring the rates at which N2 is washed out of the lung while the subject breathes pure O2. A theory of lung ventilation in terms of differential equations is presented which gives an explanation for the apparent increase in dead space when there is non-uniform mixing and which provides new measures for the efficiency and effectiveness of ventilation. These are in terms of the renewal rates for gases in the lung. 18 normal subjects, 30 patients afflicted with poly-cythemia vera, and 12 patients having various lung diseases, resting and breathing at their normal rates, are compared with each other. Even in the normal groups there is considerable non-unformity of mixing in the lungs. This lowers the efficiency of ventilation to a mean of 0.57 of that which would be achieved with perfectly uniform mixing. In the normal and polycythemic groups a decrease of effectiveness of ventilation with an increase in age is shown. The ventilatory characteristics of the subjects with lung disease are shown to be appreciably different from those of subjects in the other groups, the mean effectiveness of ventilation being less than half that for the normal subjects. The use of the effectiveness and efficiency as indices of physical fitness and of the degree of impairment of function in disease is suggested. Expts. with normal exercising and hyperventilating subjects indicates that the ventilation of the deeper lung spaces is less readily modified by either form of hypernea than has been thought to be the case.