Abstract
Observing modern decompression protocols alone cannot fully prevent diving injuries especially in repetitive diving. Professional audio Doppler bubble measurements are not available to sports scuba divers. If those non-professionals were able to learn audio Doppler self-assessment for bubble grading, such skill could provide significant information on individual decisions with respect to diving safety. We taught audio Doppler self-assessment of subclavian and precordial probe position to 41 divers in a 45-min standardized, didactically optimized training. Assessment before and after air dives within sports diving limits was made through 684 audio Doppler measurements in dive-site conditions by both trained divers and a medical professional, plus additional 2D-echocardiography reference. In all dives (average maximum depth 22 m; dive time 44 min), 33% of all echocardiography measurements revealed bubbles. The specificity of audio bubble detection in combination of both detection sites was 95%, and sensitivity over all grades was 40%, increasing with higher bubble grades. Dive-site audio-Doppler-grading underestimated echo-derived bubble grades. Bubble detection sensitivity of audio Doppler self-assessments, compared to an experienced examiner, was 62% at subclavian and 73% at precordial position. 6 months after the training and 4.5 months after the last measurement, the achieved Doppler skill level remained stable. Audio Doppler self-assessment can be learned by non-professionals in a single teaching intervention. Despite accurate bubble grading is impossible in dive-site conditions, relevant high bubble grades can be detected by non-professionals. This qualitative information can be important in self-evaluating decompression stress and assessing measures for increased diving safety.
Highlights
During ascent in scuba diving, inert gases such as nitrogen can become supersaturated in tissues and blood
In 28 of 342 dives, the dive computer indicated a single-level decompression stop at 3 m, which was observed in addition to the 3 min safety stop
Due to evolving ultrasound technology and the recordings performed at the dive site without noise cancellation, we were able to show a clear advantage of 2D echocardiography for bubble detection in contrast to previous studies [16]
Summary
During ascent in scuba diving, inert gases such as nitrogen can become supersaturated in tissues and blood. This results in microbubbling and macrobubbling and can lead to symptoms of decompression sickness. Internal and Emergency Medicine sports diving limits [1], and there is a wide inter- and intraindividual variety in developing bubbles and decompression symptoms, despite following dive computer profiles that calculate ascent schedules from depth-time integrals. A high number of detectable bubbles after ascent in up to 50% of divers was related to symptoms of decompression sickness in 2–11% of sports dives and up to around 40% of decompression and mixed gas commercial dives [1,2,3]. Symptomatic divers need oxygen and recompression treatment, asymptomatic bubbling is not considered for treatment in sports diving and in most cases not diagnosed at all
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