Study objectives: To compare the changes in resting energy expenditure (REE) to concomitant changes in clinical status and pulmonary function in cystic fibrosis (CF) patients during treatment for acute pulmonary exacerbation. To determine if weight loss during exacerbation in CF is related to decreased calorie intake or increased energy needs.
Design: Measurements of REE, pulmonary function tests, oxygen saturation, respiratory rate, maximal inspiratory pressure (MIP), white blood cell count, chest x-ray films and attribution of clinical score (ACS) on admission, mid-hospitalization, and discharge. Anthropometric measurements on admission, assessment of dietary intake and nitrogen balance upon admission and prior to discharge.
Subjects: Thirteen CF patients admitted for treatment of acute pulmonary exacerbation with a mean age of 11.0 +/- 7.9 (SD) years.
Results: From admission to discharge, REE decreased from 44.5 +/- 9.0 to 33.8 +/- 8.5 kilocalorie (kcal)/kg/d (p < 0.003). Similarly, the ACS improved from 7.5 +/- 2.0 to 4.0 +/- 2.2 (p < 0.0001); the absolute neutrophil count decreased from 10,685 +/- 6,226/microliters to 6,363 +/- 168/microliters (p < 0.005); respiratory rate decreased from 32.6 +/- 6.2 to 25.0 +/- 3.7 breaths per minute (p < 0.01); and MIP increased from 77.5 +/- 20.0 to 90.0 +/- 20.4 cm H2O (p < 0.01). In parallel, less significant improvements occurred in pulmonary function tests, oxygen saturation and chest x-ray film scores. Calorie intake was 1,893 +/- 635 and 2,054 +/- 707 kcal/d on admission and discharge, respectively (p = NS); during hospitalization, weight increased from 23.6 +/- 10.1 to 25.7 +/- 10.1 kg (p < 0.005). While carbohydrate and fat content of the diet remained essentially unchanged, a significant increase in protein intake (3.15 +/- 0.92 to 3.5 +/- 0.81 g/kg/d [p < 0.05]) and in nitrogen balance (1.8 +/- 2.5 to 5.6 +/- 2.9 g of nitrogen per day [p < 0.05]) were observed.
Conclusions: In acute CF, pulmonary exacerbation, changes in REE parallel those of clinical improvements and are more sensitive than pulmonary function tests and chest x-ray films as an objective clinical correlate. Increased metabolic requirements but not decreased dietary intake are the cause of weight loss in CF patients.