An introduction to diving physiology


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At the end of this course you should understand why?

  • Decompression Illness (DCI) is by nature a probabilistic event.
  • DCI relates to DCS- (decompression sickness) and AGE- Arterial Gas embolism.
  • As divers we want to get out of the water as clean as possible, without any symptoms of DCS.
  • General overview of decompression theory and practice.

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A little bit of history

Lesson one

  • Paul Bert concluded that nitrogen is absorbed by the body in a proportion to the pressure and sometimes forms bubbles when the pressure is released.
    He also understood the notion of what we know today as bubble seeds or micronuclei.

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A little bit of history

Lesson one

  • Haldane developed the notion of various “tissues” (compartments) within the body, affected by blood flow, the gas loading in those tissues behaves according to the law of exponential decay found throughout nature (e.g. radiation). Base on his studies on goats submitted to depressurisation in hyperbaric chambers, he suggested humans would reach full saturation in five hours.

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A little bit of history

Lesson one

  • They understood that decompression sickness (becomes symptomatic) cannot occur if there aren’t bubbles seeds presents prior to the dive, which they called points (micro-nuclei).

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A little bit of history

Lesson one

  • Workman in 1957 concluded (1507 total man-hours of test dives) that the faster compartments tolerate greater overpressure ratios than the slower ones.

We will discuss the concept of halftime later in the course.


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A little bit of history

Lesson one

  • In 1965 Workman included nitrogen and helium in his work, coined the term “M-values” for them (where M stands for maximum). He presented a computational “linear projection” algorithm.

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A little bit of history

Lesson one

  • Bühlmann indicated that the M-value will vary according to the proportion of each gas present in the compartment, in accordance to the partial pressures of the different inert gases and their solubility coefficients in the plasma (blood).

4 of Bühlmann’s book were published from 1983 to 1995.


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A little bit of history

Lesson one

Deep Stops, early 1990

  • Richard Pyle anecdotal evidence.- Arbitrary approach.
  • Yount DE, Hoffman DC Varying permeability model (VPM), introduced the use of a bubble formation model to calculate diving tables, the general idea is to control the size of the bubbles already formed.- Not an arbitrary approach.

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A little bit of history

Lesson one

Edward Thalmann (NAVY)

  • Dr. Edward Thalmann (NAVY) published in 1984 an algorithm based on the asymmetric gas kinetics concept (VVal–18) which was implemented by Cochran Undersea Technology (2012).

    Also, Cochran Undersea Technology has a proprietary algorithm (with deep stops) implemented on his diving computers.


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A little bit of history

Lesson one

Deep Stops

  • Erik Baker introduced gradient factors (GF), a computational methodology that shift the M-value line toward the ambient pressure which introduces deep stops but also extends shallow stops, according to the value given (GF Hi;GF Low).- Arbitrary approach.

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A little bit of history

Lesson one

Decompression Computation and Analysis Program (DCAP) made by Dr. Robert (Bill) Hamilton.

  • Table-generation software and estimates the probability occurrence of DCS.
    This software embedded several decompression models, but incorporated the Hamilton-Kenyon bubble model, that has been developed from VPM.
  • Also build in the NOAA-Hamilton Trimix Decompression Tables used by NOAA for diving on the American Civil War vessel USS Monitor.


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A little bit of history

Lesson one

DCAP

A recreational- technical decompression software was released called Nautilus under the umbrella of Joel D Silverstein and Dan Nafe, sadly the efforts for a technical diving decompression base on DCAP was abandoned.

Currently Poseidon Rebreathers system use DCAP in their recreational- tech computers.


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Remember that this keynote is an overview of the course, refer to it for deeper study material.

Also don’t neglect to check our library.

End Chapter of History


Copy Right Carlos Lander -www.diveimmersion.com