Whole-body vibration preconditioning reduces the formation and delays the manifestation of high-altitude-induced venous gas emboli.

Abstract

What is the central question of this study? Is performing a 30-min whole-body vibration (WBV) prior to a continuous 90-min exposure at 24,000ft sufficient to prevent venous gas emboli (VGE) formation? What is the main finding and its importance? WBV preconditioning significantly reduces the formation and delays the manifestation of high-altitude-induced VGE. This study suggests that WBV is an effective strategy in lowering decompression stress. Rapid decompression may give rise to formation of venous gas emboli (VGE) and resultantly, increase the risk of sustaining decompression sickness. Preconditioning aims at lowering the prevalence of VGE during decompression. The purpose of this study was to investigate the efficacy of whole-body vibration (WBV) preconditioning on high-altitude-induced VGE. Eight male subjects performed, on separate days in a randomised order, three preconditioning strategies: 40-min seated-rest (control), 30-min seated-rest followed by 150 knee-squats performed over a 10-min period (exercise) and 30-min WBV proceeded by a 10-min seated-rest. Thereafter, subjects were exposed to an altitude of 24,000ft (7315 m) for 90min whilst laying in a supine position and breathing 100% oxygen. VGE were assessed ultrasonically both during supine rest (5-min intervals) and after three fast, unloaded knee-bends (15-min intervals) and were scored using a 5-grade scale and evaluated using the Kisman Integrated Severity Score (KISS). There was a significant difference in VGE grade (P<0.001), time to VGE manifestation (P=0.014) and KISS score following knee-bends (P=0.002) across protocols, with a trend in KISS score during supine rest (P=0.070). WBV resulted in lower VGE grades (median (range), 1 (0-3)) and KISS score (2.69±4.56a.u.) compared with control (2 (1-3), P=0.002; 12.86±8.40a.u., P=0.011) and exercise (3 (2-4) , P<0.001; 22.04±13.45a.u., P=0.002). VGE were detected earlier during control (15±14min, P=0.024) and exercise (17±24min, P=0.032) than WBV (54±38min). Performing a 30-min WBV prior to a 90-min continuous exposure at 24,000ft both delays the manifestation and reduces the formation of VGE compared with control and exercise preconditioning.