Peter Saundby has put the following posting on the U.K. u.r.a.s.:

Following the string on oxygen systems, pilots intending to fly at altitude
should be very wary of relying upon oxymetry devices intended for clinical
use to confirm in the air that they are adequately oxygenated. Professor
John Ernsting, long of the RAF Institute of Aviation Medicine gave a
presentation on their limitations at the recent International Congress of
Aerospace Medicine in Warsaw. These devices have been used by pilots of
unpressurised aircraft to monitor the adequacy of their oxygen supply or to
assess the performance of emergency oxygen systems. The problem is that
when suffering a degree of hypoxia there is a tendency to hyperventilate and
the consequent reduction of carbon dioxide will increase the stability of
oxy-haemoglobin. While blood saturation appears adequate, too little oxygen
will be released to the brain. This theory was confirmed by experiment in a
chamber; therefore extreme caution should be exercised when using oximetry
at altitude because it can offer a false assurance.

Hypoxia is a real hazard in aviation, witness the recent accident to an
airliner in Greece. Systems must be used within manufacturers guidance and
above FL245 any problem can be rapidly lethal.

Peter Saundby

Peter Saundby is a Retired Air Commodore RAF Medical Branch.

He has been the BGA medical adviser since the 1960s.

He has been a glider pilot for longer than most of us care to remember,
first with the RAF and currently at the Black Mountains Gliding Club,
Talgarth.

He is a qualified RAF pilot.

I would think very hard indeed before ignoring his advice on aero-medical
matters.

W.J. (Bill) Dean (U.K.).
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