DEEP SEA DIVING MEDICAL & PHYSICAL BACKGROUND

[Music] [Applause] [Music] [Applause] [Music] [Music] first records of time we know that man has sought to reach the depths of the sea either as an adventure or for gain or to bring defeat to his enemy in battle at the beginning his only means of descent were his own powers of endurance a deep breath and a headlong dive so equipped he could go all over the short distance and stay but a short time some prodigious liars of history to the contrary consequently he began to invent machines that would enable him to remain submerged for ever-increasing periods and mighty crude they were to for instance regard this gadget developed by Loreen II in 16:9 a fairly sure guarantee of hemorrhage in the lungs but despite the dangers and the difficulties despite the bends in suffocation man went on trying and trying until CB in 1819 devised the dress which is the basis of those we use today there was a workable invention that enabled man within limits to perform almost any underwater task you could search for lost objects on the bottom of the ocean he could find Rex long buried in the water and from them could raise treasures while still at seed he could repair ships damaged by collision or by war he could save these ships send them on their way to port or back against the enemy he could rescue his friends who were trapped in submarines releasing them from death it could work for men it never worked before welding cutting salvaging a great ship gutted by fire and lying useless on its side the ship needed in war to carry the men of war to the fighting front this he could save working far within it clearing the wreckage repairing the damage cutting away the obstructions so that it can go back to its job go back to the seven oceans but no matter how fine the dress no matter how alert his helpers the diver is still working in an element in which he does not belong a strange element with its own laws alien to the air-breathing animal and nothing can guarantee him success more than his own perfect physical condition it is not enough that he'd be able to pass the ordinary physical examination even the rigorous Navy examination you must be a better man than that a man of superb health alive in every nerve and sinew for water exerts pressure and a man must be able to adjust himself to the altered physics that that pressure brings about a cubic foot of salt water weighs sixty-four pounds or 445 thousands pounds per square inch an imaginary point submerged one foot under water has 445 thousands pounds per square inch pressing on it from all sides for since water is a fluid it exerts its pressure from all directions not from just one as the hammer that falls on your toe so a diver sixty six feet underwater is enduring the water pressure bearing on him from all sides of twenty nine and four tenths pounds per square inch this is not an exact figure since the pressure at his head is less than that at his feet his height governs the difference this measurement of pressure we call gauge pressure but there's another way of measuring this pressure air exerts pressure too since the air forming the Earth's atmosphere possesses weight on the surface of the earth there's a pressure of 14 and 7/10 pounds per square inch caused by this weight of the overlying streak of air and this pressure for obvious reasons we call an atmosphere the depth of salt water necessary to exert the same pressure 14 and 7/10 pounds is 33 feet and so when we had the average weight of the air on the Earth's surface - the weight of water at 33 feet we call the total weight of that depth or the gauge pressure plus the pressure of the atmosphere the absolute pressure or two atmospheres absolutely consequently at 66 feet the absolute pressure is three atmospheres absolutely at 99 feet four atmospheres absolute and so on down it is helpful to remember that one atmosphere equals 14 and 7/10 pounds or 33 feet of salt water or 760 millimeters of mercury now man was not designed with these pressures in mind he has to be able to adjust himself to their added weight and the quickest way to discover whether he is psychologically and physically healthy enough to endure them is to use the recompression chamber so design primarily as an aid in treating the diseases of pressure this chamber since it permits a man to be subjected to any desired pressure serves as an excellent examination room bread obviates the dangers of sending a man over the side and into depths from which it might not be easy to rescue him should he not be capable of withstanding increased pressure each candidate therefore as part of his examination must show that he can endure a pressure of 50 pounds gauge equivalent to a depth of approximately a hundred and twelve feet without undue physical discomfort or mental disorganization only after he has passed successfully can he be considered as satisfactory for diving instruction and so to pass a man has to be absolutely healthy if he is his body will withstand the increase of pressure the human body is composed of approximately 70% water 15% fat 15% solid tissue since it is almost impossible to compress water the healthy man is able by the very nature of his body to bear a pressure throughout his entire frame without altering shape equal to that exerted at 6,000 feet where the actual structure of his cells would change form but this is a depth to which at the moment there's no hope he'll be able to descend it is not the pressure itself on his body provided that body is healthy the tax is a man's endurance in the dark lower waters among other things it is the effect that the pressure has on the air a man breathes air as we know is composed of various gases it's approximate composition is oxygen 21 percent nitrogen 78 percent carbon dioxide 3 hundredths percent and certain rare gases 97 hundredths of 1% and these gases unlike water can be compressed that is a given amount of air can be squeezed into a smaller space than it originally occupied an open Bell at sea level contains air under a pressure of 14 and 7/10 pounds if it is lowered through the sea the pressure from without forces the surrounding water through the open bottom and makes its power felt' on the air pushing it into an ever smaller space it happens that at 2 atmospheres absolute or 29 and 4 tenths pounds the air is squeezed into half its original volume at 3 atmospheres absolute or 44 and one-tenth pounds into one third and so on the bell always contains the same quantity of air that air merely takes up less and less room as the pressure grows greater in other words its density increases the diver however is enclosed in a dress which has a fixed volume consequently since the air and it is under pressure according to the depth that the diver is submerged and since the actual space that air occupies is less than at sea level it will take a far greater quantity of air to fill his dress this increased density of the gases of the air has strange effects on man who is designed to breathe air at sea level pressure two of the gases nitrogen and oxygen become in large amounts definitely toxic and so limit the depths to which man can dive breathing compressed air this limit is considered to be 300 feet where the pressure is 148 and two tenths pounds absolute or 10 atmospheres absolute here the density of each gas present in the suit and so breathed into the lungs is increased 10 times and in such quantities both nitrogen and oxygen are proved poisonous nitrogen is the more dangerous for nitrogen in quantity has a narcotic effect produces in some individuals even at depths as small as 100 feet a narcosis akin to drunkenness or that produced by ether the 300 feet a divers responses are so slowed and his judgment is so inaccurate because of the abnormal amount of nitrogen breathed but it would be extremely dangerous if not fatal for him to descend further life-giving oxygen as well prohibits compressed air diving for depths greater than 300 feet oxygen is consumed by the body the lungs absorbing approximately 5% of that present in the air breathed this consumption occurs in the lungs as the oxygen combines with substances in the red corpuscles of the blood and then is delivered by the blood to the tissues of the body where it is burned this combustion forms carbon dioxide and water which the blood returns to the lungs where it is given off to the air when man is below two atmospheres absolute of pressure pure oxygen breathes long enough irritates the tissues of the lungs reduces nausea and dimness of vision there's the pressure is increased muscle spasms convulsions and unconsciousness ensue now air is approximately one-fifth oxygen three hundred feet equals 10 atmospheres absolute so the oxygen concentration at three hundred feet is the same as one fifth of 10 atmospheres or two atmospheres absolute of pure oxygen consequently 300 feet is as far as man can safely descend breathing compressed air diving to greater depths is possible only on a helium oxygen mixture in which helium replaces nitrogen and the amount of oxygen is reduced according to the depth so that the quantity breathed always remains less than two atmospheres Babson of pure oxygen but even the normal body is subject to diseases but in the comfortable world of sea level pressures are no problem and the pressure chamber brings these diseases to light the most important of these are diseases of the respiratory system though the basic examination for these are made before the candidate enters the chamber the chamber itself shows when pressure of 50 pounds is applied whether the candidates upper respiratory system is open to permit increased air pressure to reach the middle ear and sinuses which are but air chambers within the body and to equalize pressure all passages of the air and sinuses must be open the ear fundamentally a simple mechanism is composed of three parts the outer canal which gives entrance not only to sounds but also to the pressure of the atmosphere the middle ear where the eardrum receives the sounds and they are heard and the estación tube which connects with the nose and throat and by so doing provides the same pressure on the inner surface of the drum that is exerted on the outer now fortunately air and water are not rigid solids and so do exert their pressure in all directions with the result that anything submerged in either does not alter shape unless there is a closed off air space inside that object for instance a sealed and empty tin can is lowered into the water at a certain depth that is crushed by the weight of the water in the same way if there were any sealed off air spaces in the human body they would be crushed by the pressure of air but alone by the vastly greater pressures of water encountered in diving luckily man has no such sealed off parts but should the estación tube be blocked either temporarily by a cold or permanently by a growth or malformation a closed-off space would exist the increased pressure from without would not be equalized from within the air drum would Bend from the unequal pressure causing acute pain a difference of 1 to 2 pounds will produce this pain a difference of 5 pounds which is roughly equivalent to the pressure at 10 feet underwater may rupture the eardrum just as the top of a bass drum would collapse if you jumped on it since sinuses are air spaces in the head with openings into the nose is obvious that any stoppage in them will cause severe pain and possible injury nor are the you stake in tubes and the sinuses the only points of danger any part of the respiratory system can be blocked by cold and the balance of pressure altered and so a diver cannot be over susceptible to colds or sinus troubles nor can he have any other maladies of the nose throat pharynx or lungs any of which may cause sealed off places Norma he'd be overweight his body must be lean and wiry regardless of his size a man was fat content is considerable is a poor risk as a diver he is more subject to caisson disease or bends than any other physical type bends are another of the contributions of nitrogen under pressure to the perils of diving as we have seen oxygen and carbon dioxide combined with the blood nitrogen does not instead it remains in solution in the blood and tissues of the body each circulation of the blood through the lungs increases the nitrogen saturation in the blood so that when the diver is at a pressure of 10 atmospheres absolute or 300 feet the nitrogen in his body is approximately 10 times more than at one atmosphere is like a bottle of soda water that has been capped his blood and tissues are charged with gas and solution just as the soda water is and should he come to the surface too quickly his body reacts as does the soda water when released because the blood cannot carry in solution to the lungs the excess amount of nitrogen being released from the tissues this effect can obviously be disastrous bubbles in the joints will cause severe pain bubbles in the veins will stop the flow of blood bubbles in the brain and spinal cord will cause paralysis if within seven minutes the blood is not restored to the brain tissues the damage may be permanent a bubble of sufficient size lodged in the heart can cause instantaneous death this condition of excess nitrogen in bubble form is called the bends it has been found that if the pressure is reduced at the rate that will keep the absolute pressure of the nitrogen in the body at less than twice the absolute pressure of the air being breathed no bubbles are likely to be found this fact is referred to as the two-to-one rule this rule means that a diver can come up half his maximum absolute depth at any time without danger of bends in actual practice this distance is exceeded when the diver has not been on the bottom long enough to become completely saturated with nitrogen for instance let us suppose that our diver has been working at 150 feet for 30 minutes counting the time he used to descend he can then be brought to 75 feet by the two-two-one rule but by taking advantage of his incomplete saturation and of the amount of nitrogen lost in a slow ascent never exceeding 25 feet a minute he can safely be brought to 20 feet using a little over 5 minutes to reach that depth he is then following the stage is set forth in the navy standard decompression tables held at 20 feet for 13 minutes brought to 10 feet and held for 21 minutes and then drawn to the surface in the meanwhile our fat man is still on the scales and in addition he has his problem which is that fat will absorb about five times more nitrogen than the other tissues of the body and that since the circulation of blood through fat tissue is poor desaturation is much slower it is obvious that the poor fat man is either in danger of the bends or him spending far too much of his time in the recompression chamber fortunately however the amount of fat in a man's body can be determined by the specific gravity test this test with scientific accuracy measures the fat content of the body by discovering a man's specific gravity than comparing it with an established norm if a man's fat content is too great we know that he is not meant to be a diver through no fault of his own unless perhaps it'd be overeating there are as well tests for determining the speed of desaturation particularly when the man is exercising since we know that exercise increases that speed furthermore we know that a young man because he has better circulation better lung ventilation and less fat desaturates more quickly than an old man and that is why thirty years is the upper limit for candidates and so our diver must be a perfect physical specimen there must be nothing wrong with him his eyes must be 20/20 in the submerged world in which he will work there is no adequate illumination not even from the diving lamp nor can a man wear glasses in a diving helmet he must have no chronic gastrointestinal disturbance no disease of the kidneys we're gonna have no active skin or venereal disease a history of syphilis will cause his rejection his circulation must be normal in his heart a fine organ to work where it will be called upon to work and above all he must be healthy mentally the bottom of the ocean is no place for the neurotic the man who is afraid of the darker of confined spaces so though he has passed his examination and his training the diver has a duty to himself in the service to keep himself physically sound mentally healthy in his spare time he should exercise play games study the nature of his profession experiment learn only by being the best of men can he do justice to his profession the long hours of painstaking and important work that he is called upon to do under the waters in the mystery of the ocean [Music] [Applause] [Music] [Applause] [Music]