Bioelectrical Impedance Vector Analysis: A Valuable Tool to Monitor Daily Body Hydration Dynamics at Altitude

Abstract

Bioelectrical impedance vector analysis (BIVA) is a method used to estimate variation in body hydration. We assessed the potential of BIVA for monitoring daily body hydration fluctuations in nine healthy, normally active males under matching normoxic (NX) and hypobaric hypoxic (HH) experimental conditions. Furthermore, we aimed to investigate whether changes in BIVA may correspond with the development of acute mountain sickness (AMS). Subjects were exposed in a hypobaric chamber to both NX (corresponding to an altitude of 262 m) and HH conditions corresponding to an altitude of 3500 m during two four-day sojourns within which food, water intake and physical activity were controlled. Bioimpedance and body weight measurements were performed three times a day and medical symptoms were assessed every morning using the Lake Louise score (LLS). Total body water (TBW) was also assessed on the last day of both sojourns using the deuterium dilution technique. We detected circadian changes in vector length, indicating circadian body water variations that did not differ between NX and HH conditions (ANOVA effects: time: p = 0.018, eta2 = 0.149; interaction: p = 0.214, eta2 = 0.083; condition: p = 0.920, eta2 = 0.001). Even though none of the subjects developed AMS, four subjects showed clinical symptoms according to the LLS during the first 24 hours of HH conditions. These subjects showed a pronounced (Cohen’s d: 1.09), yet not statistically significant (p = 0.206) decrease in phase angle 6 hours after exposure, which may indicate fluid shift from the intracellular to the extracellular compartment. At the end of each sojourn, vector length correlated with deuterium dilution TBW “gold standard” measurements (linear regression: NX: p = 0.002 and r2 = 0.756, HH: p < 0.001 and r2 = 0.84). BIVA can be considered a valuable method for monitoring body hydration changes at altitude. Whether such changes are related to the development of clinical symptoms associated with AMS, as indicated in the present investigation, must be confirmed in future studies.

Changes in body mass, appetite-related hormones, and appetite sensation in women during 4 days of hypobaric hypoxic exposure equivalent to 3,500-m altitude

“…The present data, collected under strictly controlled conditions, demonstrate that short-term HH exposure (i.e., 4 days at 3,500 m) exerts an effect on appetite-regulating hormones (i.e., anorexigenic effect), suppresses appetite sensation, and can induce body weight loss in young healthy females. The magnitude of the observed weight loss was somewhat unexpected, as the participants received a standardized diet during both sojourns and no such effect was found in males ( 38 , 39 ). Among the investigated hormones, acylated ghrelin and leptin were the most likely to explain the effect on appetite suppression.…”

“…Finally, intestinal malabsorption could have contributed to a negative energy balance in HH, although this seems unlikely as malabsorption is only described at much higher altitudes ( 7 ). It is noteworthy that men previously exposed to the same study protocol experienced no HH-induced reduction in body weight ( 38 , 39 ), suggesting a possible sex-specific effect of HH on body weight that could be investigated in future studies.…”

Bioimpedance Vector Analysis for Heart Failure: Should We Put It on the Agenda?

“…Early detection of fluid retention is challenging in HF. Recently, bioimpedance vector analysis (BIVA) has emerged as a new tool able to evaluate congestion ( 20 ). The electrical impedance field is also corroborated by implanted devices able to assess intrathoracic impedance and communicate data directly via telemonitoring.…”