Operation Everest III (Comex'97): altitude-induced decompression sickness during a hypobaric chamber experiment: necessity for circulating venous gas emboli monitoring for the investigators.

Abstract

INTRODUCTION: Acute exposure to altitude changes increases the risk of decompression sickness (DCS). Altitude-induced DCS incidence is from 15 to 20% and > 30% above 8,000 m. A particular risk occurs for scientific investigators during hypobaric chamber experiments. OBJECTIVE: In the present study, we assess whether the detection of nitrogen venous gas emboli (VGE) could help to screen the investigators at risk for altitude-induced DCS. MATERIAL AND METHODS: During a 32-day hypobaric chamber experiment, we collected clinical episodes of DCS symptoms in the investigators, and performed detection of VGE using two-dimensional (2D) echocardiography and pulsed Doppler ultrasonography guided by 2D images, graded from 0 to 5. RESULTS: Eight investigators made a total of 32 flights, including 8 flights above 8,000 m, with a 15.6% overall incidence of DCS symptoms and a 50% incidence above 8,000 m. VGE detections were systematically performed at or above 8,000 m (eight detections), and some detections were performed at 5,000 m, 6,000 m, and 7,000 m. VGE grades 3 and 4 were present in all but one subject with DCS symptoms and preceded the "bends" in all cases. VGE detection thus confirmed, in a more sensitive way compared to clinical examination, that our precautionary measures for DCS were not optimized. CONCLUSION: VGE monitoring for investigators during hypobaric chamber experiments increased the sensitivity for the detection of subjects at risk for DCS.