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

Abstract

Objective: To evaluate bioelectrical impedance analysis (BIA) in estimating the nutritional status and outcome of patients with chronic obstructive pulmonary disease (COPD) and acute respiratory failure (ARF) in comparison with 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 hospital. Patients: 51 COPD patients with ARF in whom BIA data, anthropometric parameters, and measurements of visceral proteins were available. Measurements and results: BIA results in patients requiring mechanical ventilation (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-/intracellular 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 weight, body mass index (BMI), triceps skinfold thickness (TSF), and fat mass were significantly higher in the invasively ventilated patients, whereas middle-arm muscle circumference (MAMC) did not differ between the two groups. The marked inflation of the extracellular compartment (ECW, ECW/ICW) that was well shown by BIA in the invasively ventilated patients presumably lead to inaccurate anthropometric results (overestimation of TSF and fat mass, and erroneous measure of MAMC). A higher death rate (38% vs. 0%, P = 0.01) was observed in the patients with ACM depletion (ACM ≤ 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 anthropometric parameters (prealbumin and transferrin levels, body weight, BMI, TSF, 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 good indication of malnutrition and of poor outcome in COPD patients with ARF.