EFFECT OF SLOPE AND SHAPE OF DISSOCIATION CURVE ON PULMONARY GAS EXCHANGE

Factors affecting gas exchange in the presence of ventilation-perfusion inequality have been examined. These include the slope and shape of the blood-gas dissociation curve, the type of ventilation-perfusion distribution, and whether the gas is being transferred into or out of the blood. It was found that the impairment of gas output caused by ventilation-perfusion inequality was greatest for inert gases of medium solubility such as nitrous oxide and was less for gases of both lower and higher solubilities. This was true both for symmetrical and skewed log normal distributions of ventilation-perfusion ratios. The factors governing gas uptake were similar except at high inspired concentrations. The shape of the blood-gas dissociation curve made remarkably little difference to the effect of uneven distribution on gas transfer. For example, when the effects of the shapes per se of the O2 and CO2 curves were compared, the differences were very small. In practice, the greater vulnerability of O2 uptake to ventilation-perfusion inequality can be explained by the slopes, not the shapes, of the two dissociation curves. © 1969.