Breath-by-breath estimation of alveolar gas exchange.

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We have developed a method that estimated breath-by-breath alveolar gas exchange by a compensation for changes in lung gas stores in studying respiratory transients during exercise. Inspiratory and expiratory flow signals were recorded with separate pneumotachographs. CO<SUB>2</SUB> and O<SUB>2</SUB> gas fractions were measured at the mouth continuously. A data acquisition program consisted of A/D conversion of the respiratory signals and calculation of alveolar gas exchange variables. The correction for breath-by-breath changes in lung gas stores was applied to the total gas exchange which was obtained by subtracting expired from inspired gas volume. Incomplete or abnormal breath-by-breath dada were automatically inspected and edited either by combining with the previous or following incomplete companion breaths. The breath-by-breath variation in the gas exchange at the mouth was larger than the alveolar gas exchange, particularly in the transient state. The variation was attributed to the invalidity of the steady state gas uptake equations which assumed constant end-expiratory lung volume over a single respiratory cycle. However, during the steady state, the gas exchange at the mouth averaged to the same value as the alveolar gas exchange. The breath-by-breath analysis of alveolar gas exchange enables the investigator to study the transient and non -steady state responses to exercise.
日本生理人類学会の論文