Mailing List Archive

Mailing List: techdiver

Message Display

>
>Hi,
>
>I am a new reader to the techdiver group. A couple of your readers
>suggested I join in. My diving qualifications are under the BSAC
>(First class diver and National Instructor) and ANDI.
>
>Following a recent Nitrox course I began to wonder about the following
>question. I would appreciate your views or comments.
>
>When teaching on a BSAC Oxygen Administration course we tell our students
>to expect a transient worsening of symptons to a casualty shortly after
>starting to administer 100% O2. This is due to two reasons. Firslty, if
>there is a lodged bubble some of the oxygen in solution will diffuse into
>the nitrogen bubble. Secondly, the body reacts to the higher partial pressure
>of O2 and reduces the blood flow due to vasoconstriction. This can be read
>in the BSAC Safety and Rescue manual.
>
>My basic question is if a diver does a dive on air and then transfers to
>O2 for stops does the vasoconstriction occur? This will reduce blood flow
>and hence increase the risk of DCS.

Stuart,
look at the previous posts on this subject by gopher or www, there
has been alot of discussion on this subject recently.  There is 
experimental evidence that changing from breathing air O2 will 
reduce nitrogen elimination compared to breathing another normobaric 
gas mixture (eg oxygen/argon).  However the increase in inert gas
difference between tissues and inspired gas that is achieved by 
using high pO2 nitrox or oxygen during a decompression stop is 
generally a larger advantage than any problems due to vasoconstriction.
Vasoconstriction will not increase the "risk" of decompression 
illness, per se.  Oxygen itself may contribute to decompression 
illness, but for practical purposes is not a major consideration 
as its elimination from tissues or bubbles is fast in comparison 
to normal decompression schedules.



David Doolette
ddoolett@me*.ad*.ed*.au*

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]