Pyle stop

A Pyle stop is a short decompression stop at depths well below the first decompression stop mandated by a conventional dissolved phase decompression algorithm, such as the US Navy or Bühlmann decompression algorithms. They were named after Dr. Richard Pyle, an American ichthyologist from Hawaii, who found that they prevented his post-dive fatigue symptoms after deep dives to collect fish specimens.

The ascent pattern has become known as Pyle stops, or "deep stops" since the late 1990s.

These stops were developed by Pyle based on personal experience, and have had a significant influence on decompression theory and practice in the following years.

In the 1980s Pyle had been diving to explore depths between 180 and 220 feet (50 and 70 m) in search of fish to collect, a depth range often called the "twilight zone". He noticed that some dive patterns did not make him feel any post-dive fatigue. Reviewing his dive profiles, Pyle found his that post-dive fatigue symptoms were almost absent when he performed some "deep stops" before his mandatory decompression stops.

After many dives, Pyle correlated the post-dive malaise to those dives when, having caught no fish, he ascended directly to the first mandatory decompression stop. On the dives where he collected fish and interrupted his ascent to vent their swim bladders well before the first decompression stop, he did not exhibit fatigue symptoms on the surface. He then instituted a system of making brief deeper stops at a pressure half-way between the previous stop (or the dive's maximum depth initially) and the first stop mandated by his decompression schedule.

Pyle received some theoretical justification for his findings when he found in 1989 that his pattern of ascent was similar to that produced by Dr. David Yount's Varying Permeability Model (VPM) of decompression calculation. The ascent pattern became known as "Pyle's stops" or "Deep stops".

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