MIXING OF GASES WITHIN RESPIRATORY SYSTEM WITH A NEW TYPE NITROGEN METER

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Abstract
By means of rapid electronic recorders for measuring N2 and expired and inspired volumes, the patterns of gas concn. and volume during single expirations, are presented for normal human subjects. To emphasize the patterns due to mixing processes, the subject first effectively cleared his lungs of N2 by breathing O2 and results were recorded when he started breathing air; during the short recording time (10 sec.) it can be shown that only about 5 ml, of N2 can be taken up by the blood from the lungs. In a maximal expiration, the records show 3 main phases: (1) a sloping water-vapor plateau of between 70 and 125 ml., curving downward into (2), a rapidly falling N2 phase (riser) of 100 to 150 ml., which slowly curves into (3), a sloping final plateau, starting at 1000 ml. and continuing to the end of the expiration. By determining the volume of N2 inspired and expired from these records, one can calculate the "residual lung volume" and hence the "total lung volume" at each instant. To emphasize the kinetic mechanisms responsible for phases (1) and (2), a factor called the kinetic dead-space is defined in terms of these 2 phases. The slope of the final plateau (%N2/liter expired) is taken as a measure of mixing efficiency. A normal, resting expiration does not reach the constant slope seen in a maximal expiration; in one case the slope of the curve varied from a maximum, in phase (2) of -215% N2/1. at 170 ml. to -4.6% N2/1. at 700 ml. to -1.75% N2/1. between 1000 and 4730 ml., of total expired volume. Relations between these recorded patterns and the following factors are discussed: Krogh''s dead-space, respiration models and pathological processes impairing mixing efficiency. Alternative procedures, using these and other rapid recorders, are discussed.
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