Effect of hyperlipidaemia on pulmonary diffusing capacity for carbon monoxide.

There is conflicting evidence on the effect of hyperlipidaemia on pulmonary diffusing capacity for carbon monoxide (DLCO or TLCO) in man. We have measured the carbon monoxide transfer factor per unit alveolar volume (TLCO/VA or KCO) by the single breath method in 25 patients with hyperlipidaemia, and in three normal subjects before and after infusions of an intravenous fat emulsion, Intralipid. Non-smokers with hyperlipidaemia had normal levels of TLCO/VA, whereas some of the smokers showed a slight reduction. In neither group was there any correlation of TLCO/VA with serum triglyceride or cholesterol concentrations. A reduction in triglyceride concentrations of up to five-fold produced by plasma exchange (three studies in two patients) or by dietary manipulation (one patient) had no significant effect on the levels of TLCO/VA. Intralipid infusion in three normal subjects caused a four- to five-fold increase in serum triglyceride concentration but had no effect on TLCO/VA. We conclude that moderate degrees of hyperlipidaemia have no effect on pulmonary diffusion.