Hemodynamics, pulmonary diffusing capacity (DLco) blood gases, oxygen consumption (Vo2) and carbon dioxide excretion (Vco2) were studied in healthy volunteers and ventilator-treated, critically ill patients before and during infusion of lipid emulsion for 4 h. Triglyceride levels rose from 1.0 mmole/L to 8.5 mmole/L in the volunteers and from 1.4 mmole/L to 6.3 mmole/L hi the patients after 4 h. No adverse effects on cardiovascular performance were observed. Increases in Vo2, and Vco2 and cardiac output were found m both groups, while RQ remained constant. No changes hi DLco and blood gases occurred.