The use of respiratory quotient to determine the efficacy of nutrition support regimens.

Respiratory quotient (RQ) is an indicator of fuel utilization. This study examined the RQs of patients receiving intensive nutrition support to assess the frequency with which net fat synthesis occurred, as determined by RQs greater than 1.0. One hundred twelve RQs were calculated from data obtained using indirect calorimetry. Seventy-four measurements were made while patients were receiving parenteral nutrition--55 with glucose and amino acid (GAAPN) and 19 with glucose, fat, and amino acid (GFAAPN). Thirty-eight measurements were made while patients were receiving either oral or nasoenterally administered carbohydrate, fat, and protein in the form of standard hospital diets or liquid defined formula diets (CFPEN). The mean RQ of the GAAPN patients was significantly higher than those of both the GFAAPN and the CFPEN patients. RQs were greater than 1.0 in a significantly greater number of the GAAPN patients than the GFAAPN or CFPEN patients. The route of nutrient intake did not influence energy nutrient utilization, as determined by RQ. This study suggests that nutrition support regimens containing fat, in addition to carbohydrate and protein, are more efficiently utilized to meet the energy requirements of hospitalized patients than are regimens containing only glucose and amino acid.