The Controversy about Blood-Gas CO2 Equilibrium in Lungs: Reinvestigation by Prolonged CO2 Rebreathing in Awake Dogs during Rest and Exercise
When pulmonary diffusing capacity for O2 is to be determined in lungs with unequal distribution of alveolar ventilation to pulmonary perfusion it is common practice to correct arterial PO2 for the shunt effect and the end-tidal PO2 for alveolar dead space ventilation. The latter correction is based on the assumption that PCO2 in end-capillary blood is in equilibrium with alveolar gas (Riley and Cournand, 1949). It appears to follow from this assumption that in conditions of no gas exchange, such as rebreathing, PCO2 in alveolar gas should be equal to that in arterial blood. Thus the finding of negative blood-to-gas PCO2 differences during rebreathing in dogs (Gurtner et al., 1969) and in man (Jones et al., 1969, 1972; Denison et al., 1971) has challenged the fundamental concepts of pulmonary gas exchange. However, these results could not be reproduced by others (Scheid et al., 1972).
KeywordsPulmonary Diffuse Capacity Respiratory Mass Arterial PC02 Rebreathing Period Blood PC02
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