OK, but how else do you check for hypoxia? We know that self-diagnosis by
checking one's own hypoxia symptoms isn't reliable either. The US Navy
studies show that the first symptom of hypoxia can be unconsciousness.

Is Prof. John Ernsting saying, "These things don't work so don't worry about
it"? Or, "Just trust that the O2 system was manufactured and installed
correctly - RTFM and go fly high"? Maybe the millions of patients
hyperventilating due to pain and who have had a oxymeter cuff stuck on their
finger were being conned by their doctors. This isn't too helpful.

Most pilots these days fly with cannulas so hyperventilating is likely to
mean breathing by mouth thus leading to oxygen deprivation as well as CO2
reduction. Maybe pilots who hyperventilate should take a few more flights
with an instructor so they can calm down when flying.

While writing this, I got a return call from a manufacturer of oxymeters who
says that they know all about CO2 scrubbing and their laser diode sensors
take it into account as do all oxymeters as far as they know. The SpO2
readings are correct in spite of it. Nothing's perfect, but oxymeters are a
better solution than anything else.

Bill Daniels


"W.J. (Bill) Dean (U.K.)." wrote in message
...
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.).
Remove "ic" to reply.