Bioelectrical impedance analysis in estimating nutritional status and outcome of patients with chronic obstructive pulmonary disease and acute respiratory failure

Objective: To evaluate bioelectrical impedance analysis (BIA) in estimating the nutritional status and outcome of patients with chronic obstructive pu lmonary disease (COPD) and acute respiratory failure (ARF) in comparison wi th measurements of anthropometric parameters and plasma levels of visceral proteins Design: Retrospective study Setting: A ten-bed intensive care unit (ICU) in a university teaching hospi tal Patients: 51 COPD patients with ARF in whom BIA data, anthropometric parame ters, and measurements of visceral proteins were available Measurements and results: BIA results in patients requiring mechanical vent ilation (MV) vs, those who did not showed lower active cell mass (ACM; 37.5 +/- 6.5% vs. 42.4 +/- 7.2% body weight, P = 0.01) and a higher extra-/intr acellular water volume ratio (ECW/ICW; 1.25 +/- 0.2 vs. 1.04 +/- 0.2, P = 0 .0001), suggesting a more severe alteration in the nutritional status among those on MV. Anthropometric data showed the opposite results, since body w eight, body mass index (BMI), triceps skinfold thickness (TSF), and fat mas s were significantly higher in the invasively ventilated patients, whereas middle-arm muscle circumference (MAMC) did not differ between the two group s. The marked inflation of the extracellular compartment (ECW, ECW/ ICW) th at was well shown by BIA in the invasively ventilated patients presumably l ead to inaccurate anthropometric results (overestimation of TSF and fat mas s, and erroneous measure of MAMC). A higher death rate (38% vs. 0%, P = 0.0 1) was observed in the patients with ACM depletion (ACM less than or equal to 40.6% body weight, n = 26) than in those without ACM depletion (n = 25). Low albumin level ( < 30 g/l) was associated with increased mortality (33% vs. 7%, P = 0.04), but the differences in the other biological and anthrop ometric parameters (prealbumin and transferrin levels, body weight, BMI, TS F, MAMC, fat mass, and fat-free mass) were not associated with mortality Conclusion: This study suggests that the decrease in BIA-derived ACM is a g ood indication of malnutrition and of poor outcome in COPD patients with AR F.