RESTING ENERGY-EXPENDITURE AND NUTRITIONAL STATE OF PATIENTS WITH INCREASED OXYGEN COST OF BREATHING DUE TO EMPHYSEMA, SCOLIOSIS AND THORACOPLASTY

Background - Weight loss is a well recognised feature of patients with emphysematous chronic obstructive pulmonary disease (COPD). It has be en suggested that this weight loss could be due to a hypermetabolic st ate resulting from the increased oxygen cost of breathing (OCB). To cl arify the relation between resting energy expenditure (REE), nutrition al state, and OCB these indices were measured in patients with respira tory impairment and an increased OCB due to COBB, scoliosis, and thora coplasty. Methods - Eighteen patients (six COED, six scoliosis, six th oracoplasty) of mean (SD) age 59.9 (8.6) years (8M, 10F) and six contr ols (45.5 (9.9) years; 2M, 4F) were studied. OCB was estimated by the addition of dead space to the breathing circuit and REE was measured b y indirect calorimetry using a ventilated canopy system. Height, arm s pan, weight, triceps skin fold thickness (TSF), mid-arm muscle circumf erence (MAMC), forced expiratory volume in one second (FEV(1)), and vi tal capacity (VC) were measured in all study subjects. Results - OCB w as elevated in all patient groups (mean 7.0 ml/l) compared with contro ls (1.9 ml/l). All patients with COBB, four with scoliosis, three with thoracoplasty, and none of the controls were <90% ideal body weight. Mean (SD) measured REE as % predicted (Harris-Benedict equation) was 1 03.8 (7.6) in patients with COPD, 105.5 (10.9) in those with scoliosis , 106.3 (6.9) in the thoracoplasty patients, and 103.3 (3.4) in contro ls. One patient with COPD, two with scoliosis, two with thoracoplasty, but no controls were hypermetabolic (REE >110% predicted). In all gro ups there was a negative relation between OCB and lung function (OCB v FEV(1) r= -0.83 in COPD, -0.62 in scoliosis, -0.67 in thoracoplasty, and -0.76 in controls). There was no correlation between REE and OCB o r MAMC. Conclusions - In patients with respiratory disease OCB (augmen ted ventilation) is related to lung function but not to REE. This is e vidence against the hypothesis that hypermetabolism due to increased o xygen cost of breathing at rest is the sole or major cause of malnutri tion in patients with lung disease.