Within-diver variability in venous gas emboli (VGE) following repeated dives.

Introduction: Venous gas emboli (VGE) are widely used as a surrogate endpoint instead of decompression sickness (DCS) in studies of decompression procedures. Peak post-dive VGE grades vary widely following repeated identical dives but little is known about how much of the variability in VGE grades is proportioned between-diver and within-diver.

Methods: A retrospective analysis of 834 man-dives on six dive profiles with post-dive VGE measurements was conducted under controlled laboratory conditions.

Extended lifetimes of bubbles at hyperbaric pressure may contribute to inner ear decompression sickness during saturation diving.

Inner ear decompression sickness (IEDCS) may occur after upward or downward excursions in saturation diving. Previous studies in nonsaturation diving strongly suggest that IEDCS is caused by arterialization of small venous bubbles across intracardiac or intrapulmonary right-to-left shunts and bubble growth through inward diffusion of supersaturated gas when they arrive in the inner ear. The present study used published saturation diving data and models of inner ear inert gas kinetics and bubble dynamics in arterial conditions to assess whether IEDCS after saturation excursions could also be explained by arterialization of venous bubbles and whether such bubbles might survive longer and be more likely to reach the inner ear under deep saturation diving conditions.

Manned validation of a US Navy Diving Manual, Revision 7, VVal-79 schedule for short bottom time, deep air decompression diving.

Introduction: The US Navy air decompression table was promulgated in 2008, and a revised version, calculated with the VVal-79 Thalmann algorithm, was promulgated in 2016. The Swedish Armed Forces conducted a laboratory dive trial using the 2008 air decompression table and 32 dives to 40 metres' seawater for 20 minutes bottom time resulted in two cases of decompression sickness (DCS) and high venous gas emboli (VGE) grades. These results motivated an examination of current US Navy air decompression schedules.

Gas micronuclei that underlie decompression bubbles and decompression sickness have not been identified.

Gas micronuclei are gas-filled voids in liquids from which bubbles can form at low gas supersaturation. If water is depleted of gas micronuclei, high gas supersaturation is required for bubble formation. This high gas supersaturation is required in part to overcome the Laplace pressure at the point of transition from dissolved gas to a bubble of perhaps nanometer-scale radius.