TOTAL-ENERGY EXPENDITURE IN PATIENTS WITH SMALL-CELL LUNG-CANCER - RESULTS OF A VALIDATED STUDY USING THE BICARBONATE-UREA METHOD

The bicarbonate-urea method for measuring CO2 production was applied t o eight free-living patients (mean age, 68 +/- 10 years; mean weight, 69 +/- 10 kg; mean height, 1.65 +/- 0.10 m) with unresectable small-ce ll lung cancer for a period of 1 day (n = 5) or 2 days (n = 3). The ba sal metabolic rate (BMR) was measured in all subjects. The technique w as first validated against whole-body indirect calorimetry over an add itional 24-hour period in five of these subjects. The bicarbonate-urea method predicted net CO2 production to be 102.1% +/- 3.4% of that mea sured by whole-body indirect calorimetry, and energy expenditure, 101. 5% +/- 3.8% of the measured calorimeter value (8.1 +/- 1.6 MJ/d). The 24-hour recovery of label in CO2 excreted by the body was 95.6% +/- 0. 5%. In free-living conditions, the bicarbonate-urea method predicted e nergy expenditure to be 9.0 +/- 2.6 MJ/d. BMR was elevated by a mean o f 6% (P < .05) compared with the Schofield standards. The physical act ivity level ([PAL] the ratio of total energy expenditure [TEE] to BMR) was variable (1.15 to 1.87), but the mean value was only 1.36 a 0.22, considerably less than that of moderately active healthy subjects wit h estimated PAL values of 1.55 (P < .05) to 1.65 (P < .01) and the mea n results obtained by doubly labeled water (previous studies) in healt hy age- and sex-matched subjects. This is the first time a tracer meth od for measuring CO2 production and energy expenditure has been valida ted against whole-body 24-hour indirect calorimetry in patients with l ung cancer or a systemic inflammatory reaction. The agreement between the two methods is similar to that observed in normal subjects. This i s also the first time a tracer method has been used to measure energy expenditure in free-living patients with lung cancer. The results sugg est that TEE and the energy requirements necessary to maintain energy balance were not increased despite basal hypermetabolism, because of t he associated decrease in physical activity. Copyright (C) 1997 by W.B . Saunders Company.