Safety Analysis of NOAA Nitrox I and NOAA Nitrox II Decompression Tables

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Safety Analysis of NOAA Nitrox I and NOAA Nitrox II Decompression Tables

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Title: Safety Analysis of NOAA Nitrox I and NOAA Nitrox II Decompression Tables
Author: Lambertsen, CJ
Abstract: The NOAA Nitrox I and II Diving/Decompression Tables are based upon an advantageous compromise between usefulness of (a) oxygen to dilute nitrogen and (b) nitrogen to dilute oxygen. The aim, initially proposed in 1941 (6), is extended diving duration, with avoidance of both decompression sickness and oxygen poisoning. A fundamental concept in decompression procedures development is that, in the useful range of nitrogen-based diving, decompression sickness initiation is due to evolution of free gas phase. Free gas phase (gas lesions, emboli) results from excessive degree and duration of an excess inert gas partial pressure relative to hydrostatic effect of ambient pressure transmitted throughout tissues. The pivotal role of nitrogen, as the inert gas in free gas phase generation, has led to the now well established concept of "Eguivalent Air Depth" upon which the NOAA Nitrox Tables are based. "Equivalent Air Depth" of a planned N2-02 (Nitrox) dive is the depth of an air breathing dive at which the inspired nitrogen partial pressure would be equal to the nitrogen partial pressure in the planned dive using the specific nitrogen-oxygen mixture. Decompression requirement within the limits of operational Nitrox diving exposures is generally based on the inspired nitrogen partial pressure/duration profile. A contributory role for oxygen acting in an inert molecular form in generating decompression sickness has not been demonstrated at practical inspired oxygen partial pressures. The limits of oxygen advantage are therefore imposed entirely by the toxic risks of oxygen depth/duration exposures (primarily central nervous system, i.e., convulsions). Nitrox and "Equivalent Air Depth" diving have both, for many years, been accepted and operationally validated concepts. Therefore the safety and usefulness of any specific Nitrox diving decompression table will depend upon the theoretical basis, laboratory trials and operational experience used for design of the underlying air decompression procedures, and the associated oxygen exposure limits. The present safety analysis project for NOAA Nitrox I and II includes the characteristics of the Standard Air Diving Tables (U.S.N.), from which the NOAA Nitrox modifications were developed, and the oxygen limits employed .
Description: The items forming the Rubicon Research Repository Christian J. Lambertsen collection are generously donated by the Lambertsen Family. All items in this collection are released through Creative Commons Attribution + Noncommercial + ShareAlike (BY-NC-SA) licenses in an attempt to encourage the use of these works to further scientific understanding of physiology.
URI: http://archive.rubicon-foundation.org/10583
Date: 1994

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