EMPHYSEMA AS POSSIBLE EXPLANATION FOR ALTERATION OF EXPIRATORY PO2 AND PCO2 CURVES

  • 1 January 1976
    • journal article
    • research article
    • Vol. 12  (5) , 605-624
Abstract
It was proposed that the shape of deformed expiratory partial pressure curves of O2, CO2, N2 and foreign gases may be caused by sequential convective emptying of compartments with decreasing .ovrhdot.VA/.ovrhdot.Q [alveolar ventilation/min per blood flow in ml/g of tissue/min]; this same deformation can be observed in healthy subjects during simultaneous breathing of H and SF6, where the SF6 curve was deformed and the H curve had a normal shape. The high MW of SF6 caused a delay of its gaseous diffusion from the peripheral air spaces of the lung. A similar delay can be caused by emphysematous changes such as a longer distance for diffusion, an increased alveolar volume and a reduction of the number of small airways, where the gas has to pass through. Different data from cross-sectional and longitudinal studies, from induced changes of bronchomotor tone, from comparison of patients with relatively pure emphysema and patients with airway obstruction and from autopsy suggest that stratification and serial inhomogeneities, caused by emphysema, are a reasonable explanation for the deformation than the .ovrhdot.VA/.ovrhdot.Q concept with sequential emptying of parallel units.