Gastric emptying, pulmonary function, gas exchange, and respiratory quotient after feeding a moderate versus high fat enteral formula meal in chronic obstructive pulmonary disease patients

High fat enteral formulas have advocated for the nutritional support of chronic obstructive pulmonary disease (COPD) patients because dietary fat utilization under ideal conditions produces less CO2 per O-2 consumed than carbohydrate. No data exist for these patients comparing the effects of a moderate fat vs. a high fat enteral formula on gastric emptying times (GE) and subsequent CO2 production (V over dot CO2), oxygen consumption (V over dot O-2), respiratory quotient (RQ), and pulmonary function. Our double-blind crossover study compared these parameters after feeding a 355 mL (530 kcal) meal with either 41% fat calories (Respalor(R)) or 55% fat calories (Pulmocare(R)). Thirty-six COPD outpatients with a forced expiratory volume in 1 s (FEV(1)) <60% of predicted were studied after an overnight fast. Gastric emptying half-time (GE t(1/2)) was measured using the Tc-99M-radionuclide technique; V over dot CO2 , Vover dot O-2 RQ, and other pulmonary functions were measured at 0, 30, 90, and 150 min postprandial using the Canopy Mode of the Deltatrac Metabolic Monitor and the Renaissance Spirometry System. We observed a significantly (p = 0.0001) longer GE postprandial, the V over dot CO2 and V over dot O-2 for patients fed the moderate-fat formula were significantly (P = 0.005) higher than for those fed the high-fat formula; no differences were observed for the other pulmonary functions. Although RQ increased significantly (p = 0.01) after both meals, no differences between formulas were noted at all postprandial times tested. Compared to the high-fat meal, the moderate-fat meal significantly enhanced gastric emptying. The earlier rise in V over dot CO2 and V over dot O-2 after the moderate-fat meal did not impact pulmonary function and reflected the earlier utilization of the moderate-fat meal. The fact that RQ was not different was most likely due to earlier gastric emptying of the moderate-fat meal rather than the difference of the fat-to-carbohydrate ratio between the two tested meals. The impact of these findings on long-term management of COPD patients awaits long-term prospective studies.