Converting standard air decompression tables for no-stop diving from altitude or habitat

Area of Science:

• Diving Physiology
• Decompression Theory
• Altitude Diving

Background:

• Standard air decompression tables require adjustments for altitude diving and normoxic habitats.
• Existing decompression models may be too conservative or unsafe under specific conditions.

Purpose of the Study:

• To develop predictive formulas for converting standard air decompression tables for no-stop dives.
• To evaluate the safety and accuracy of current decompression practices for altitude and habitat diving.
• To test hypotheses regarding gas release and decompression sickness.

Main Methods:

• Application of the phase equilibration theory (Hills, 1966; Hennessy & Hempleman, 1977).
• Comparison of predicted decompression profiles with existing altitude and habitat diving tables.
• Analysis of US Navy repetitive group rules for post-dive flight safety.

Main Results:

• Formulas were derived for altitude and normoxic habitat diving.
• Some existing rules were found to be too conservative or potentially unsafe.
• Predictions showed agreement with Swiss altitude tables and Hamilton et al. normoxic tables.
• US Navy repetitive group D rule may be unsafe for dives over 50 fsw before flying.

Conclusions:

• A single tissue and safe ascent pressure formula are sufficient for equivalent air dives.
• The volume of gas released during ascent governs Type I decompression sickness.
• No-stop ascents release all excess dissolved gas in the worst-case scenario.