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Oxymetry.
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. |
#2
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Hi,
Please define what an "oxymetry device" is. Paul Remde "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. |
#3
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Paul Remde wrote:
Hi, Please define what an "oxymetry device" is. Paul Remde I assume it's one of those small clip on pulseox devices that have become popular of late. Runs about $250 and reads out the sats and pulse rate. I have one, but I really don't rely on it too much. Oxygen is cheap, I use it liberally. |
#4
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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. |
#5
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W.J. (Bill) Dean (U.K.). wrote:
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. Lower pH, resulting from hyperventilation, decreases hemoglobin's affinity for O2. The rest makes sense (higher affinity, higher measured saturation level, and yet poor O2 delivery in tissues). Could it be *hypo* ventilation. Do you have any references we could read. Shawn |
#6
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How does blood vessel constriction due to cold affect the readings? The
meters usually take a bit of time to a stable reading, during which time the glove is off. It is usually not tropically warm at the altitudes where oximeters are most valuable. - Hartley Falbaum "Shawn" sdotcurry@bresnananotherdotnet wrote in message ... W.J. (Bill) Dean (U.K.). wrote: 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. Lower pH, resulting from hyperventilation, decreases hemoglobin's affinity for O2. The rest makes sense (higher affinity, higher measured saturation level, and yet poor O2 delivery in tissues). Could it be *hypo* ventilation. Do you have any references we could read. Shawn |
#7
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"Shawn" sdotcurry@bresnananotherdotnet wrote in message ... W.J. (Bill) Dean (U.K.). wrote: 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. Lower pH, resulting from hyperventilation, decreases hemoglobin's affinity for O2. The rest makes sense (higher affinity, higher measured saturation level, and yet poor O2 delivery in tissues). Could it be *hypo* ventilation. Do you have any references we could read. Shawn I agree with Shawn.....but still feel that an oxymeter is the best way of providing info wrt your oxygen system working. I also think that within the flight levels that most of us fly it is a clinically insignificant difference. If your saturation is OK then there would be less drive to hyperventilate and so it would be less of an influence. I'd like to see the original data too. Casey Lenox KC Phoenix |
#8
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That should be "higher pH caused by hyperventillation"
Someone who is underventillating (not breathing) gets a lower (acidotic) pH. due to the buildup of CO2. We hyperventillate patients on mechanical ventillators in the OR all the time, and still rely on the oximeters. The readings correllate very well to actual measured blood gases, taken from an artery. It would take a lot of hyperventillating to shift the oxyhemoglobin dissociation curve enough to be significant. (Core Temperature is probably as important, btw) If one is not to rely upon an oximeter.....what other convenient mechanical means of measuring hypoxia should we rely on? Certainly, if your oximeter reading is in the high 90's, you are OK. One should become familiar with one's baseline readings on the ground, btw. Normals differ from person to person due to age, cardiovascular health...etc. A healthy, normal person breathing 21% O2 (room air at sea level) usually shows anywhere from 97 to 99 on an oximeter. Also, it takes a good minute, often longer, of not breathing to see a change in oximeter readings. Conversely, there is a lag in upswing of the readings once you start breathing again. Breathing a slightly thinner atmosphere (at altitude) should show a slowly dropping reading as altitude is gained, and/or more time is spent at that higher altitude. (Time at altitude relationship, as mentioned in the FAR's regarding Oxygen use while flying) I guess the lesson would be to familiarize yourself with these vagaries on the ground before using/relying upon the instrument at altitude. It's a good numerical safety check to have on board the aircraft, but like they teach us in training.....don't forget to also check the patient! "Kilo Charlie" wrote in message news:eupYe.261468$E95.67794@fed1read01... "Shawn" sdotcurry@bresnananotherdotnet wrote in message ... W.J. (Bill) Dean (U.K.). wrote: 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. Lower pH, resulting from hyperventilation, decreases hemoglobin's affinity for O2. The rest makes sense (higher affinity, higher measured saturation level, and yet poor O2 delivery in tissues). Could it be *hypo* ventilation. Do you have any references we could read. Shawn I agree with Shawn.....but still feel that an oxymeter is the best way of providing info wrt your oxygen system working. I also think that within the flight levels that most of us fly it is a clinically insignificant difference. If your saturation is OK then there would be less drive to hyperventilate and so it would be less of an influence. I'd like to see the original data too. Casey Lenox KC Phoenix |
#9
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"Shawn" wrote in message W.J. (Bill) Dean (U.K.). wrote: 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. Lower pH, resulting from hyperventilation, decreases hemoglobin's affinity for O2. The rest makes sense (higher affinity, higher measured saturation level, and yet poor O2 delivery in tissues). Could it be *hypo* ventilation. Do you have any references we could read. Shawn Oops. My bad. I was getting pCO2 (partial pressure of CO2 in blood) and pH confused. Hyperventilation blows off CO2/carbonate, lowering pCO2, less acid *higher* pH (duh!), higher affinity can result in higher saturation. Hemoglobin has higher affinity for O2 at higher pH-lungs, lower affinity at low pH-tissues, makes sense. Truly embarrassing, I stand (well I'm sitting actually) corrected. I'd still like a reference though. Shawn |
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