The Effect of Whole-Body Vibration Preconditioning on High-Altitude-Induced Venous Gas Emboli
Abstract: Decompression sickness (DCS) is a risk associated with high-altitude aviation and diving. During these activities, decompression may lead to supersaturation of inert gas dissolved in bodily tissues and subsequently activate bubble formation in various bodily tissues, including in venous blood, known as venous gas emboli (VGE). It has been shown that the amount of VGE detected during and after decompression is linked to the risk of developing DCS. Thus, lowering the incidence of VGE would lower the risk of developing DCS. Previous studies have demonstrated that a session of whole-body vibration prior to a diving session is effective in lowering VGE formation. However, no study has investigated the effect of whole-body vibration on high-altitude-induced VGE. For the present study, 3 participants were recruited. The subjects performed on separate days (interspaced by 48 h) and in a randomised manner, three different preconditioning strategies: (A) 40-min seated rest, (B) 30-min seated rest followed by 150 knee squats performed over a 10 min period and (C) 30-min whole-body vibration (40 Hz) proceeded by a 10 min seated rest. Thereafter, subjects were exposed to an altitude of 24,000 ft continuously for 90 min, whilst laying in a supine position and breathing a normoxic gas mixture (PIO2 = 21 kPa). Heart rate (HR), cardiac output (CO) and stroke volume (SV) were monitored throughout the high-altitude exposure. Every 5 min, VGE prevalence was assessed ultrasonically and graded according to the Eftedal-Brubakk 5-point scale. In addition, every 15 min, subjects were asked to perform three fast, unloaded knee-bends while in their left-side horizontal recumbent position, with VGE prevalence being estimated both before and after the three knee-bends. The control strategy was associated with a higher VGE scores (2.7 ± 1.2) compared to vibration (1.0 ± 1.0) and squats (1.3 ± 0.6) strategies. VGE appeared earlier during the control strategy (35 ± 23 min) compared to the vibration (65 ± 31 min) and squats (50 ± 17 min) strategies. A strong negative correlation was only observed in the control strategy between VGE and CO (r = -0.63) and SV (r = -0.64). This study demonstrated that whole-body vibration is the most effective preconditioning strategy in lowering the amount of high-altitude-induced VGE compared with 40-min of seated-rest and 150 knee squats performed over a period of 10 min.
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