Key result
Subclavian high bubble grades were more strongly associated with decompression sickness risk (RR 6.0; 95% CI 2.7-12.3) than precordial grades (RR 2.6; 95% CI 1.1-6.0).
Why the study?
Does subclavian venous gas emboli detection better predict decompression sickness compared to precordial detection in scuba divers?
Cohort (n=1,016)
Does subclavian venous gas emboli detection better predict decompression sickness compared to precordial detection in scuba divers?
Relative Risk: 6 (95% CI 2.7–12.3)
p-value: p=<0.001
Subclavian venous gas emboli detection shows a stronger association with decompression sickness risk than precordial detection, suggesting its usefulness in decompression stress evaluation.
Subclavian VGE grades were associated with higher DCS risk than precordial; leaves open whether dual-site monitoring improves decompression assessment in practice.
INTRODUCTION: Ultrasonic detection of venous gas emboli (VGE) in the precordial (PRE) region is commonly used in evaluation of decompression stress. While subclavian (SC) VGE detection can also be used to augment and improve the evaluation, no study has rigorously compared VGE grades from both sites as decompression stress indicators. METHODS: This retrospective study examined 1,016 man-dives breathing air extracted from the Defence Research and Development Canada dataset. Data for each man-dive included dive parameters (depth, bottom time, total ascent time), PRE and SC VGE grades (Kisman-Masurel) and post-dive decompression sickness (DCS) status. Correlation between SC and PRE grades was analyzed and the association of the probability of DCS (pDCS) with dive parameters and high bubble grades (HBG III- to IV) was modelled by logistic regression for SC and PRE separately for DCS risk ratio comparisons. RESULTS: PRE and SC VGE grades were substantially correlated (R = 0.66) and were not statistically different (p = 0.61). For both sites, pDCS increased with increasing VGE grade. When adjusted for dive parameters, the DCS risk was significantly associated with HBG for both PRE (p = 0.03) and SC (p < 0.001) but the DCS risk ratio for SC HBG (RR = 6.0, 95% CI [2.7-12.3]) was significantly higher than for PRE HBG (RR = 2.6, 95% CI [1.1-6.0]). CONCLUSIONS: The association of bubble grades with DCS occurrence is stronger for SC than PRE when exposure severity is taken into account. The usefulness of SC VGE in decompression stress evaluation has been underestimated in the past.
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France et al. (2018) conducted a cohort in Decompression stress following scuba diving (n=1,016). Subclavian venous gas emboli high bubble grades vs. Precordial venous gas emboli high bubble grades was evaluated on Decompression sickness (DCS) (RR 6.0, 95% CI 2.7-12.3, p=<0.001). Subclavian high bubble grades were more strongly associated with decompression sickness risk (RR 6.0; 95% CI 2.7-12.3) than precordial grades (RR 2.6; 95% CI 1.1-6.0).
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