Variations in oxygen consumption and carbon dioxide production during parenteral nutrition

To verify that variations caused by total parenteral nutrition (TPN) in O2 intake (VO2) and CO2 output (VCO2) can affect respiratory function of non-hypercatabolic patients, we studied 18 patients in two groups; group I (control): eight patients receiving 75-100 g glucose/24 h, and group II: ten patients fed intravenously on 13.6 g N2 and approximately 2,800 kcal/24 h given as a) 62% glucose + 38% fats (TPN-G + F) and b) 100% glucose (TPN-G). VO2, VCO2, respiratory quotient (RQ) and minute ventilation (VE) were measured in all patients. We found that VCO2 was 27% higher in intravenously fed patients (p less than 0.01 and p less than 0.02). Similarly, VE was 26% higher in intravenously fed patients (p less than 0.001 and p less than 0.02). Comparison of TPN-G + F and TPN-G results showed no differences in VCO2; by contrast, VO2 was 21% less during TPN-G (p less than 0.01).