Hypoxia

[Music] m [Music] hi I'm Roy Neil and we're here to discuss a subject of great importance to every flight crew member trainee or passenger who flies in aircraft from the Air Force the subject is hypoxia or what happens to your body when the cells either don't get enough or can't use enough oxygen with me are four experts from different fields in the air Force who are here to give us some insight into some of the dangers of hypoxia and also to discuss its causes prevention and treatment our guests are Brigadier General Charles E Chuck Jagger director of Aerospace safety Colonel Giles W Hall chief of Aerospace physiology for headquarters air training command Colonel Sydney T Lewis flight surgeon for the life sciences group of the Air Force Safety Center and Captain Roger Paige Jr instructor pilot in the undergraduate pilot training program at Shepard Air Force Base and suppose we begin our discussion with General joerger General you've had a long and distinguished career in the Air Force first as a fighter pilot in World War II and then as a test pilot for the first research rocket plane the Bell X1 first man to fly supersonic later commandant of the Aerospace Pilot School a research pilot school now as director of Aerospace safety and in that capacity you're responsible for Air Force safety around the world it's an awesome responsibility yes Roy I've been around a long time I suppose I've sort of grown up with the air force uh as it is today and the job as the Director of safety for the air force uh I'm sort of responsible for all of the safety disciplines not only flying but ground and the the whole shebang and trying trying to save our resources around the world has hypoxia ever hit you yes uh I would very few pallots who have flown a lot especially in the old days uh have escaped the hazards of hypoxia or then anoxia uh in World War II we were flying uh quite a bit higher than our equipment uh would allow us or keep us normal we were flying over 36 to 38,000 ft with just demand oxygen Mas we didn't have pressure breathing equipment in those days I've I've seen a lot of uh bad experiences due to hypoxia I think one of the the ones that really uh impressed me the most uh was Joe Walker an NACA pilot we were doing some work on the X4 I checked him out in the aircraft we were calibrating the air speed systems I was flying an f86 uh on his wing and uh I had three calibrated systems air speed systems on the uh f86 and you go along and change the speed over the X4 and then I would record the readings of my three systems as he was stabilized and I noticed that Joe ran a point twice and uh we were supposed to be changing and I got up a little closer to him and looked him over and I saw he didn't look too alert and I asked him why he was doing this and became a little belligerent and uh I knew we were at 25,000 ft and the X4 didn't have a pressurization in the cockpit so I had to get his attention and get him down but since he had become belligerent uh I told him that IID had a flame out and was going down would he follow me down uh at least get him down below 15,000 ft and I said I'm flaming out and heading towards Poncho Bar's Ranch a good place he knew and so he did get excited enough and got out of his stuper to follow me down but uh you know this really impresses you on how this thing can creep up on you and it's just something that'll nail you if you're not careful let's backtrack just a bit if we may General Colonel h isn't it true that uh hypoxia can occur both at sea level and at altitude yes quite easily too uh give you a good example of hypoxia at sea level uh I can just simply reach up and just squeeze like this and more or less strangle myself as an excellent case of course we don't see too much of that uh another good example would be like a heart attack anemia a shock but our primary problem with hypox in the Air Force occurs when you as into altitude and of course this is caused by if c a partial pressure of oxygen in other words uh failing to use the oxygen equipment properly yes and uh one occasion you'll find that the equipment doesn't function properly itself but I say primarily our problems with hypoxia are caused by the pilot uh who doesn't uh display good oxygen discipline Captain Paige from your experience can you give us any examples of something like that yes as a matter of fact I uh encountered a brief experience with hypoxia which I'll consider due to equipment malfunction while on a high altitude student training Mission I felt a warm flush tingling in the fingertips and recognized my symptoms of hypoxia as I had been trained in the altitude chamber I immediately selected 100% oxygen and a pressure setting on the regulator initiated a desent we uh passed down rather quickly had no problem as soon as I got 100% oxygen I recovered from the symptoms of hypoxia now this I consider important I had done a price check two times on that equipment once prior to leaving the Squadron building and once after arriving at the aircraft the equipment was in good shape and it checked out properly both times however after takeoff several times during flight I had moved my oxygen mask with my hand and this perhaps caused the rip in the material near the valve that we discovered and in this case although it did happen I think the example of equipment failure is very rare C Lewis U what is the major concern here well oxygen equipment failure does lead to hypoxia but more common is the misuse of the equipment or the failure to use the equipment we've had two cases that were reported to us and both of these occurred in f-102s and both of the pilots involved were experienced Pilots they had been through their physiological training and certainly should know how to use the equipment but in the first case the pilot uh was afraid that he was going to develop what we call delayed aerotitis media which is occurs after breathing 100% oxygen forol long periods of time and occurs when the oxygen in the middle ear is reabsorbed he was going to resolve this problem by not using his equipment and what he would do would be to get into the aircraft make sure that there was sufficient oxygen in the aircraft hook up his equipment make sure it was functioning and then he would turn the regulator off and let the oxygen MK dangle at the side of his face he got away with this until one Mission uh in which he was flying an intercept and it was during an O so he really wanted to make this intercept and he was climbing up through 25,000 ft when his cabin altitude began to climb with him and soon he had a a cabin pressurization failure without oxygen and he was trying to get to the Target and he passed out and he really displayed his time of useful Consciousness at altitude when he recovered he was at 8,000 ft in an inverted Spin and he did recover the aircraft now he could very well have ended up in a smoking hole and we would have found that the cause of this accident was undetermined but he did recover the aircraft and he came back and told us about it so we could pass this on to air Crews so they won't make the same mistake that he did so we do have these problems in fact we've had pilots who have removed their oxygen masks in order to smoke a cigarette General gger would it be a fair statement that the primary causes of hypoxia then are equipment failure and failure to use the equipment properly yes uh Roy there's many cases uh accidents and incidents where guys abuse their oxygen equipment uh they lay a helmet and an oxygen mask out in the sun you get dust in the valves and it boils down at uh poor discipline when it comes to the use of the equipment can really cause accidents I'm sure there must be other factors too though U smoking fatigue um colon Lewis can you comment on those yes uh smoking is is one of our our major factors uh individuals smoke U have about 10% of their hemoglobin that is tied up as what we call carboxy hemoglobin and it is no value to carrying oxgen so they are in fact hypoxic on the ground and they have they have difficulties with this so we do have other factors let's see if we can pin this down somewhat um Colonel Hall what are the symptoms of hypoxia before you talk about the symptoms you want to talk about the characteristics uh the most important single characteristic of hypoxia is the simple fact that it's Insidious the term Insidious treacherous it has a tremendous ability to sneak up and take your life before you know what happens now when you speak about symptoms are very simple very easy to remember in fact they're very similar to the early scien and symptoms of a person who's inebriated or just plain drunk poor coordination lack of judgment an obvious one is a headache and then coinciding with all this is a dimming or a blurring evasion but we're going to talk more about symptoms later how can you uh prevent and how can you treat hypoxia oh to prevent it is very easy good common sense just exercise good oxygen discipline now to treat it again very simple we have a four rules that you should do number one when you get hypoxia quite obviously you want to get on 100% oxygen and descend down from altitude uh number two you should get on an emergency setting three check your oxygen equipment and then four and equally important monitor your rate in depth of breathing because you don't want to hyperventilate at a time like this uh so far we've discussed the the causes the symptoms the prevention of the treatment of hypoxia might be a good idea now to get a basic explanation of the four different types of hypoxia Colonel Hall would you tackle that one I would suggest let's take a look at a short animated film we have which clearly explains the four types of hypoxia and of course the various [Music] symptoms when we breathe air is inhaled through the nasal passages into the lungs the lungs are composed of millions of tiny air sacs Alvi all of them are surrounded by tiny blood vessels called capillaries one Alvis and one of its capillaries show their function as we breathe the Alvis fills with air containing its normal percentage by volume of oxygen Venus blood returning from the body cells releases carbon dioxide and takes on a fresh oxygen supply in the body under normal conditions the amount of oxygen transferring depends upon the difference between the oxygen pressure in the Alvis and that in the blood the heart pumps the blood to the body cells in another pressure differential exchange some 30% of the oxygen is absorbed a cell needs that much for normal metabolism the burning of nutrients to produce energy carbon dioxide and other products the carbon dioxide goes into solution in the blood for the ride back to the lungs through the veins it's a continuous cycle of demand Supply and delivery when we increase bodily activity the body cells demand more oxygen breathing deepens and speeds up to increase the supply and heart action accelerates to increase the rate of delivery however when there is a shortage of oxygen in the body cells there operating efficiency falls off the body loses its efficiency directly the effects are first apparent in the central nervous system which Demands a very large portion of all of the B's available oxygen and is therefore highly sensitive to its reduction the oxygen shortage to body and brain cells is hypoxia resulting in decreased overall body efficiency it varies from mild to severe if not relieved it increases in severity until unconsciousness and collapse occur from the onset of hypoxia many symptoms can be present in varying degrees for a while the body compensates as an exertion but the action is barely evident if at all to the individual early in the hypoxic condition visual Acuity and peripheral vision lose sharpness this may not be noticeable air areas such as fingernails and lips where the blood is near the surface begin to turn blue a sense of well-being and high self-confidence sets in perhaps tingling dizziness and nausea show up personality changes may occur mental faculties dull muscular coordination deteriorates until all control is gone finally unconsciousness followed quickly by collapse at altitude hypoxia is particularly dangerous it's Insidious it sneaks up on you it tells you you're doing great when you really aren't it progresses so rapidly when severe oxygen shortage occurs abruptly that you may not have time to help yourself it can lead to very serious consequences there are four ways that oxygen quantity getting into the body cells can be reduced hypoxic hypoxia results from insufficient oxygen pressure in the lungs a supply shortage it occurs in Suffocation pneumonia drowning or reduced atmospheric pressure as we go up total outside air pressure decreases and its oxygen pressure lessens correspondingly the Alvis capillary oxygen pressure differential lowers less oxygen enters the blood less of it gets to the body cells in slow Ascent this is the first phase of hypoxia slightly increased lung and heart action compensate easily for this oxygen deficiency there are no noticeable effects and the body still has some reserves there are no time restrictions on flights below 10,000 ft between 10 and 15,000 ft lung oxygen pressure gets so small that the blood can't meet normal body cell demands even with full compensating efforts hypoxia is evident any additional exercise increases it immediately from here to 20,000 compensation is completely inadequate hypoxia becomes severe physical and mental reserves are minimal unconsciousness is only minutes away to 25,000 there is acute physical and mental incapacitation leading to unconsciousness and in time convulsions and finally to cessation of breathing and circulation to fly at these high altitudes we need full protection from hypoxia so we hook on an oxygen supply it feeds through a regulator and a mask the regulator gives mostly air up to 10,000 ft then the regulator automatically adds more oxygen as altitude increases this keeps lung oxygen pressure near a CA level equivalent as we go up between 28 and 32,000 ft the mixer is delivering the 100% oxygen we need any leaks at the mask would let outside air in reducing pressure but by 40,000 even 100 100% oxygen on demand isn't enough to compensate for small leaks hypoxia is present again so back to approximately 28,000 ft now we add automatically a slight positive pressure this helps to seal the mask to the face and keeps the lung pressure up we stay ahead of hypoxia by adding pressure the operational ceiling of present day oxygen equipment is 43,000 ft during emergency conditions pressure demand oxygen equipment may be used up to 50,000 ft this is the limit but we have to fly a lot higher here is a device which will protect us at any altitude it has a helmet and an inflatable suit which covers the body the oxygen passes through the suit regulat to pressurize the body and feeds to the helmet for breathing its pressure to both varies automatically as required up to about 34,000 ft the B's environment inside the suit is equal to the actual environment outside it the suit holds the body at that altitude regardless of how high you go you've got hypoxia licked but there's yet another way to do it a way that conserves oxygen and increases Comfort we use a relatively airtight cabin we air pressurize it to keep the inside altitude lower than flight altitude but compressors can't always keep inside altitudes safely below those where hypoxia affects us a pressure demand oxygen system solves that problem and cabins can lose pressure by puncture or by mechanical or material failure gradually or abruptly in either case above 10,000 ft you need oxygen time of useful consciousness Tu at 18,000 ft averages 30 minutes your mask should be on or readily available Tu gets smaller as we go up even in a pressurized cabin at 26,000 you need your mask attached to your helmet and ready for use you need your mask on at 35,000 ft at 43 to 45,000 and above Tu is only a matter of seconds in Rapid decompression Tu may be only half as long so in a pressurized cabin with a pressure demand oxygen system you can Cruise comfortably up to 43,000 Ft but that's still the body's safe limit for routine operations without a pressure suit add one to keep the body at 34,000 ft when the cabin altitude gets above that you are automatically protected in decompression to any altitude a second type of hypoxia hypemic results from a reduction of the oxygen carrying capacity of the blood one cause is blood loss which reduces the number of red blood cells faster than the body can make new ones the fewer the red blood cells the less oxygen carried the greater the degree of hypoxia carbon monoxide is another cause when inhaled the Affinity of the red blood cells for it is 200 times greater than for oxygen this markedly reduces the oxygen carrying capacity of the blood severity of hypoxia depends upon the amount inhaled but even in small quantities as in smoking it appreciably lowers the body's tolerance for altitude don't smoke excessively before flying always avoid engine exhaust gases on the ground or in the air it takes a long time to get it out of the system when ever you detect smoke or fumes of any kind put your oxygen mask on turn your regulator to 100% and breathe at a normal rate in a third cause of hypemic hypoxia certain drugs inhibit the absorption of oxygen by the red blood cells and reduce delivery the effect is basically the same as that from carbon monoxide when you're ill always see your flight surgeon never self-medicate stagnant hypoxia results from the slowing down or restriction to the flow of blood there are four basic causes the first comes from being uncomfortably cold internal mechanisms which maintain constant body temperature know that the body may live with frozen extremities these mechanisms restrict the blood flow in the skin arms legs and head and slow it down to pool or stagnate while they speed up circulation around the vital organs to keep them alive there is less blood available for carrying oxygen temperature extremes such as heat or cold reduce altitude tolerance positive G forces are the most frequent cause of stagnant hypoxia centrifugal force pulls the blood from the head and pulls it in the lower extremities fighting uphill its flow rate slows drastically vision is impaired and soon after blackout occurs G suits exert pressure on abdomen and legs retarding the blood pooling and in turn helping to prevent blackout tensing muscles particularly in the legs and straining the abdomen while forcibly exhaling will help also a third cause of stagnant hypoxia is immobility normally the veins return the blood to the heart from the body at an adequate rate those leading up to the heart move it by a milking action tiny cuplike valves prevent back flow activity of the muscles around which the veins entwine keeps the milking flow going when the muscles are immobile vein action retards blood flow rate slows mild to severe hypoxia can result in either case altitude Toler is reduced the fourth cause of stagnant hypoxia is shock the body's anesthetic to Shield itself from s whenever we are hurt or extremely hot or see something distasteful or tragic involuntary nerves do two things they relax the heart so that it pumps less strongly slowing the flow of oxygen carrying blood to the body and they expand the veins creat ating a lower blood pressure Venus pooling occurs the oxygen supply is reduced and the brain cells become hypoxic the greater the shock the quicker the blackout if you suffer uncomfortable pain in Flight shock may be imminent go to 100% oxygen breathe at a normal rate histotoxic hypoxia differs from the other types in that there is plenty of oxygen in the blood but the body cells refuse to accept or use it in normal metabolism the body cells have set amounts of various catalysts primarily enzymes some harmful chemicals such as ethyl alcohol as well as narcotics and barbiturates disrupt the delicate metabolic enzymes metabolic rate decreases the cells still need the normal oxygen supply being delivered but their ability to absorb and use it is decreased hypoxia results the recovery period from the effects of alcohol is also a dangerous time severity and duration depend upon the amount of alcohol consumed the time in which it was consumed and individual tolerance taking an already hypoxic body up to regions of lower atmospheric pressure compounds the hypoxia breathing 100% oxygen will not help a hangover or make you safe to fly with one that's the hypoxia story but there is yet another important condition which leads to a hypoxic state this is hyperventilation when we breathe faster and deeper than normally because of fear anxiety stress or tension we expel more than the normal amount of carbon dioxide from the lungs and in turn from the blood very rapidly this upsets the acid base balance of the blood causing an insufficient amount of ox oxygen to be delivered to the body cells one of the first symptoms of hyperventilation is dizziness treat it as follows go to 100% oxygen and initiate an immediate descent check your regulator for proper operation make sure that your connections are okay and that the mask fits properly go to an emergency setting and concentrate on breathing normally an interesting film that just about wraps up our discussion General jerger any final comments well Roy uh in the past history of the Air Force hardly a day went by that there wasn't an incident report or an accident report where hypoxia was involved but for every one of those incident reports or accident reports there were 5,000 at least that were successful because the Cru used good oxygen discipline out it's pretty well up to the individual that flies in the airplane whether he's the pilot or the Navigator the load master or the flight engineer now when we lose these airplanes we can replace them but when it's your neck we can't replace it so give it a lot of thought [Music]