Currens, J. | bioRxiv Science

bioRxiv2026

A quantitative approach to assess similarity between dives under the Buhlmann decompression algorithm constraints

Undersea and high-altitude operations regularly put operators at risk for decompression sickness (DCS), which is attributed to bubble formation and growth during decompression. DCS mitigation strategies are validated with empirical testing, often conducted in hyperbaric chambers, which provide precise control of the pressure-time profile. A degree of variability for study outcome is anticipated in both decompression sickness (DCS) and venous gas emboli (VGE) endpoints. Experimentation in a chamber offers precision, but is not always practical or operationally relevant, leading researchers to use open water for the dive exposure. Dive profile consistency may vary by diver skill level and environmental conditions, potentially introducing dive profile deviations, which may be a factor of individual variability. There does not exist a quantitative framework for evaluating dive profile consistency and quantifying deviations in open water studies. In this work, we evaluate existing dive profile metrics and propose a workflow to estimate dive profile deviations using the Buhlmann dissolved gas phase model. The dive profile metrics included depth and time-based calculations, as well as surface gradient factor, degree-of-conservatism and the root mean square error of the Buhlmann tissue compartments. We developed a set of simulated dive profiles and obtained a set of 40 open water dives previously collected by certified divers, both of which were used to evaluate performance of the dive profile metrics. Depth and time-based metrics offered sensitivity to varying depths and time durations of the dive profiles, respectively. For the field dives, we found the Buhlmann root mean square error metric performed best at identifying the deviation profile, followed by pressure root time. These evaluations demonstrate the utility and limitations of previously published dive profile metrics and emphasize the importance of accounting for dive profile consistency in open water decompression trials.

physiology↗

bioRxiv2026

Human decompression in real time: programmable ultrasound imaging during hyperbaric exposure

The formation of inert gas bubbles during decompression can lead to decompression sickness (DCS), a major operational risk for divers, compressed-gas workers, astronauts, and high-altitude aviators. In diving, DCS risk is typically inferred from post-dive ultrasound detection of venous gas emboli (VGE), precluding modification of decompression schedules based on real-time physiological feedback. Two-dimensional ultrasound imaging could provide additional insight into decompression-related physiological changes; however, its use in hyperbaric environments has been largely precluded by fire risk associated with elevated oxygen partial pressures (ppO2) in enclosed spaces. Here, we developed a workflow for operating a programmable ultrasound system under hyperbaric conditions and acquiring ultrasound data from the subclavian vein and calf muscle during decompression. A total of 42 dives were conducted by 26 individuals using a previously characterized dive profile to 132 feet seawater (FSW) for 20 min with 9 min of decompression. Three exposure conditions were evaluated: non-exercising, exercising, and a brief pause at 20 FSW during compression. Twelve dives included programmable ultrasound imaging during decompression. Post-dive VGE responses were consistent with prior reports while demonstrating substantial inter-individual variability and sensitivity to modest profile modifications. VGE were detected in the subclavian vein during decompression in two participants and subsequently confirmed by post-dive echocardiography. Calf muscle ultrasound brightness typically increased from pre-dive to decompression measurements, before decreasing below baseline in the 120 min post dive measurement period. These findings demonstrate the feasibility of programmable ultrasound imaging during human decompression and establish a practical framework for ultrasound operation under hyperbaric conditions. This approach may support future physiological studies and development of automated decompression monitoring technologies. New and NoteworthyThis study demonstrates the first use of a programmable ultrasound system to acquire and quantitatively analyze ultrasound data during human decompression. The approach enabled direct visualization of venous gas emboli during decompression and revealed calf muscle ultrasound signal changes, providing a new tool for investigating physiological responses during decompression that are not accessible through conventional post-dive monitoring.

physiology↗