Variability in circulating gas emboli after a same scuba diving exposure
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A reduction in ambient pressure or decompression from scuba diving can result in ultrasound-detectable venous gas emboli (VGE). These environmental exposures carry a risk of decompression sickness (DCS) which is mitigated by adherence to decompression schedules; however, bubbles are routinely observed for dives well within these limits and significant inter-personal variability in DCS risk exists. Here, we assess the variability and evolution of VGE for 2 h post-dive using echocardiography, following a standardized pool dive in calm warm conditions.
14 divers performed either one or two (with a 24 h interval) standardized scuba dives to 33 mfw (400 kPa) for 20 min of immersion time at NEMO 33 in Brussels, Belgium. Measurements were performed at 21, 56, 91 and 126 min post-dive: bubbles were counted for all 68 echocardiography recordings and the average over ten consecutive cardiac cycles taken as the bubble score.
Significant inter-personal variability was demonstrated despite all divers following the same protocol in controlled pool conditions: in the detection or not of VGE, in the peak VGE score, as well as time to VGE peak. In addition, intra-personal differences in 2/3 of the consecutive day dives were seen (lower VGE counts or faster clearance).
Since VGE evolution post-dive varies between people, more work is clearly needed to isolate contributing factors. In this respect, going toward a more continuous evaluation, or developing new means to detect decompression stress markers, may offer the ability to better assess dynamic correlations to other physiological parameters.
KeywordsEchocardiography Venous gas emboli Ultrasound Decompression sickness Microbubble
Venous gas emboli
The authors wish to thank the NEMO33 pool for kindly hosting us after hours, all the volunteers who so generously donated their time, as well as Mindray for technical support. This work was supported in part by the PHYPODE project, funded by the European Union under a Marie Curie Initial Training Network (FP7-PEOPLE-2010-ITN program, Grant Agreement No. 264816), as well as the Divers Alert Network/R.W. (Bill) Hamilton Memorial Dive Medicine Research Grant (VP award 2017) administered by the Women Divers Hall of Fame.
VP, PG, DC, MXT and CB substantially contributed to conception and design of the study. VP, GO and AB acquired all the data. ST supervised and coordinated all diving and measurement schedule adherence. VP, PG, DC, RJE, PAD, GO, AB, MXT, ST and CB substantially contributed to data analysis and interpretation. VP drafted the article. PG, DC, RJE, PAD, GO, AB, MXT, ST and CB revised the article critically for important intellectual content. Additional information: sadly, coauthor David Cosgrove (DC) passed away. All other authors read and approved the final version of the manuscript.
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