RESUMO
The maintenance of body cell mass (BCM) is critical for survival in human immunodeficiency virus (HIV) infection. Accuracy of bioimpedance for measuring change (Delta) in intracellular water (ICW), which defines BCM, is uncertain. To evaluate bioimpedance-estimated DeltaBCM, the ICW of 21 weight-losing HIV patients was measured before and after anabolic steroid therapy by dilution (total body water by deuterium - extracellular water by bromide) and bioimpedance. Multiple-frequency modeling- and dilution-determined DeltaICW did not differ. The DeltaICW was predicted poorly by 50-kHz parallel reactance, 50-kHz impedance, and 200 - 5-kHz impedance. The DeltaICW predicted by 500 - 5-kHz impedance was closer to, but statistically different from, dilution-determined DeltaICW. However, the effect of random error on the measurement of systematic error in the 500 - 5-kHz method was 12-13% of the average measured DeltaICW; this was nearly twice the percent difference between obtained and threshold statistics. Although the 500 - 5-kHz method cannot be fully rejected, these results support the conclusion that only the multiple-frequency modeling approach accurately monitors DeltaBCM in HIV infection.
Assuntos
Impedância Elétrica , Infecções por HIV/patologia , Adulto , Anabolizantes/uso terapêutico , Água Corporal/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Estudos de Avaliação como Assunto , Espaço Extracelular/efeitos dos fármacos , Feminino , Infecções por HIV/tratamento farmacológico , Humanos , Líquido Intracelular/efeitos dos fármacos , Masculino , Métodos , Pessoa de Meia-Idade , Oxandrolona/uso terapêutico , Redução de Peso/efeitos dos fármacosAssuntos
Líquidos Corporais , Estado Terminal , Pletismografia de Impedância , Desequilíbrio Hidroeletrolítico/diagnóstico , Viés , Cuidados Críticos/métodos , Humanos , Pletismografia de Impedância/métodos , Sistemas Automatizados de Assistência Junto ao Leito , Valor Preditivo dos Testes , Reprodutibilidade dos Testes , Desequilíbrio Hidroeletrolítico/etiologiaRESUMO
OBJECTIVE: To determine the precision and bias of single- and multiple-frequency bioimpedance estimates of total body water (TBW) and extracellular water (ECW) volumes in comparison with the true values for these volumes established by gold standard dilution techniques. DESIGN: Controlled, prospective, open-label investigation. SETTING: Private, not-for-profit university-affiliated, acute care hospital. PARTICIPANTS: Normal, healthy men (n = 8) and women (n = 6) volunteers, 25-46 years of age. INTERVENTIONS: A single oral dose of a mixture of deuterium oxide 10 g and bromine 30 mmol; bioimpedance analysis pre- and three hours postmixture administration. MAIN OUTCOME PARAMETERS: TBW and ECW volumes established by deuterium oxide and bromine dilutional spaces (gold standards), respectively, and single- and multiple-frequency bioimpedance estimates of those same volumes. RESULTS: The mean multiple-frequency bioimpedance (MFB) and single frequency bioimpedance (SFB) estimates of TBW, 41.2 and 42.1 L, respectively, were not statistically different (NS) from the 41.2 L deuterium oxide value. Although the two methods had similar precision (NS), MFB was less biased. For ECW, the mean MFB and SFB values of 19.5 and 24.8 L, respectively, were significantly different from the bromine value of 18.8 L (p = 0.013 and p = 0.001, respectively). MFB was the more precise and less biased predictor of ECW. CONCLUSIONS: Compared with SFB, the MFB approach is a more precise and less biased predictor of TBW and ECW volumes in young, healthy adults, and may offer more accurate assessment in subjects with aberrant physiology.
