The rate of rise of alveolar carbon dioxide pressure during expiration in man.

Abstract

SUMMARY1. The purpose of the study was to see whether the rate of rise of alveolar Pco, (PA, co2) in expiration was directly proportional to the rate of pulmonary elimination of C02 ( Vco2) in man in the steady state.2. Alveolar ventilation at rest and during exercise in man was calculated from the difference between total ventilation and dead space ventilation, and from the ratio of the rate of pulmonary C02 elimination to the mean expired alveolar C02 (total) fraction. The results were indistinguishable. In agreement with other workers' findings alveolar ventilation changed in direct proportion to the rate of carbon dioxide elimination, confirming the isocapnia of exercise ventilation in man.3. The rate of rise of expiratory alveolar PCO2 in individual breaths has been obtained by two methods. In the first, a pattern of respiration with constant expiratory flow in each breath brought expiratory alveolar profiles to the outermost end of the airway. In the second method, the early part of the alveolar PCO2 during normal expiration was calculated from airway PCO2 and expired volume.4. The data obtained with both methods show that, in the steady state, expiratory alveolar PCO2 rises at a rate which is directly proportional to the rate of C02 production.

Effect of exercise intensity on the changes in alveolar slopes of carbon dioxide and oxygen expiratory profiles in humans

“…At rest and during exercise, the FO 2 and FCO 2 during the alveolar phase (phase III) of the respiratory cycle normally do not attain a real plateau but show an increase throughout this phase ( Fig. 1) (DeVries et al 1982;Cochrane et al 1982;Allen et al 1984;Whipp et al 1988). The details of these changes can now be assessed as more rapid and accurate breath-by-breath measurements of alveolar gas content are feasible.…”

“…The slope, or the mean rate of rise, of alveolar PCO 2 ( _ P A CO 2 ) in expiration has been demonstrated to increase markedly as the intensity of muscle exercise increases although the quantitative analysis has been restricted to relatively low exercise intensities (Allen and Jones 1984;Allen et al 1984;Cochrane et al 1982). But, although the corresponding slope of the declining partial pressures of alveolar oxygen ( _ P A O 2 ) also increases as exercise intensity increases, its characteristics have been virtually ignored compared with those of CO 2 .…”

Rate of change of alveolar carbon dioxide and the control of ventilation during exercise.

“…The mass-spectrometer response time is influenced by the transport time from the sampling site to the instrument, the response time of the instrument and the sampling frequency (Noguchi, Ogushi, Yoshiya, Itakura & Yamabayashi, 1982). If the transport time is measured (Beaver, Wasserman & Whipp, 1973;Pearce, Milhorn, Holloman & Reynolds, 1977) or assumed (Cochrane et al 1982;Linnarsson, 1974, Davies, Hahn, Spiro & Edwards, 1974 but the response time is ignored, there are systematic errors in 202 and yco2 measurements when these are compared to values obtained by simultaneous expired gas collection (Noguchi et al 1982). Several complex methods to correct for the instrumental response time have been developed (Noguchi et al 1982;Mitchell, 1979;Arieli & van Liew, 1981;Beaver et al 1981) that are all standardized against steady-state expired gas collections.…”

“…Recent studies (Cochrane, Newstead, Nowell, Openshaw & Wolff, 1982) (Band, Wolff, Ward, Cochrane & Prior, 1980 (Fowler, 1948) was applied to the PCO2 and Po, versus time plots by the computer, and each breath was partitioned into a dead-space and alveolar wash-out time. The PSc, and PO, at the mid-point of the alveolar phase of expiration were taken to represent mean alveolar PO, and Pco,.…”

Role of carbon dioxide oscillation in the control of respiration in the anesthetized dog.

“…This is mainly based on the following experimental findings: 1) the rate of rise of the respiratory CO2 oscillation reflects Vco2 (SAUNDERS, 1980;COCHRANE et al, 1982;ALLEN and JONES, 1984), 2) there is a linear relationship between Vc02 and ventilation (WASSERMAN et al, 1967;PHILLIPSON et al, 198 la); and 3) the peripheral chemoreceptor appears to provide a rate sensitivity to Paco2 (BLACK et a1.,1971;PoNTE and PURVES,1974). In addition, there have been many experiments which indirectly support this hypothesis (e.g., YAMAMOTO and EDWARDS, 1960;PHILLIPSON et al, 1981 b;CROSS et al, 1982).…”