Decompression limits for compressed air determined by ultrasonically detected blood bubbles

Area of Science:

• Diving Medicine
• Hyperbaric Physiology
• Ultrasonic Detection

Background:

• Assessing decompression limits is crucial for diver safety.
• Venous Gas Emboli (VGE) formation is a key indicator of decompression stress.
• Individual susceptibility to VGE and decompression sickness (bends) varies.

Purpose of the Study:

• To determine direct decompression limits using ultrasonic VGE detection.
• To investigate the relationship between VGE formation and bends.
• To evaluate the influence of dry chamber versus open ocean exposures on VGE and bends.

Main Methods:

• Ultrasonic detection of precordial venous gas emboli (VGE).
• Controlled dry chamber air exposures (233 ft/7 min to 25 ft/720 min).
• Open ocean dives (165 ft/10 min) with six divers.

Main Results:

• A strong individual propensity for VGE formation was observed, correlating with bends susceptibility.
• No bends occurred without prior detection of precordial VGE.
• Open ocean dives resulted in a higher incidence of VGE and bends compared to dry chamber exposures.
• The concept of no issues at 30 fsw was not supported.
• Computed isopleths showed VGE occurrence between 10-60%.

Conclusions:

• Individual susceptibility significantly influences VGE and bends risk.
• Precordial VGE detection is a reliable indicator preceding decompression sickness.
• Short-half-time tissue sensitivity is critical in saturation exposure management, more so than extended half times.