Breath-by-breath sampling of end-expiratory gas

¹ Laboratories of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

An electromechanical method is described for breath-by-breath sampling of gas from the respiratory passages of experimental subjects or from various locations in the breathing apparatus employed. The sampling system includes features permitting the initiation of sampling at different phases of exhalation, initiation of sampling by inspiration and the varying of sampling duration. The breath-by-breath sampling system is shown to be adaptable to physiological and pharmacological studies of spontaneous fluctuations in the composition of end-tidal gas, studies of the rate of change of end-expiratory gas in transitional states and to artificial control of end-tidal pCO₂. The magnitude of the pCO₂ difference between end-tidal gas and arterial blood is shown to decrease to essentially zero as tidal volume is increased above normal levels.