Effects of fat emulsion on O₂ transport and alveolar-arterial gas tensions

¹ Physiology-Biophysics Branch, School of Aviation Medicine, Brooks Air Force Base, Texas

Ten dogs were made progressively hypoxic by rebreathing from an air-filled spirometer. Arterial blood samples were drawn at five levels of alveolar Po₂ (100, 70, 55, 40, and 25 mm Hg), as well as samples before and after the hypoxia for O₂-capacity determinations. Half the animals then were given 25 ml/kg of fat emulsion intravenously and the others were given the same amount of dextran. The same sampling procedure was repeated and the blood was analyzed for O₂ content. In separate experiments, the same procedure was followed for five dogs but only fat emulsion was given and the arterial blood was analyzed for Po₂ and Pco₂. Oxyhemoglobin dissociation curves were constructed from the values of saturation at progressively falling alveolar Po₂. These were transformed into a linear equation by the Hill equation and treated statistically. No significant differences were found between any of the comparisons of slope or displacement. It was concluded that lipemia offered no practical hindrance to the uptake of O₂ by the red cell. Alveolar-arterial gas tension differences revealed no change after intravenous fat emulsion in the Po₂ difference, but there was a threefold increase in the Pco₂ difference.