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Aviation History
1948
1948 - 0019.PDF
TST, TQ48 FLIGHT OXYGEN for PASSENGERS Details of New Developments for Oxygen Supply in Civil Aircraft IN the recommendations for standards, practices, andprocedures dealing with international air service opera-tions (Ops) issued by P.I.C.A.O. in May, 1946, article VII of section 8 in chapter IV states that '' Oxygen supply necessary for adequate protection of crew and passengers shall be available on those operations involving regular or accepted operations with a cabin pressure less than that equivalent to 10,oooft (3,048 metres). An adequate emer- gency supply of oxygen shall also be available for the use of the flight crew on all regular or accepted operations an altitude above 10,000ft whether or not the cabin is essurized." It is with the first half of this recommenda- tion that we are here concerned, for it raises an issue that, so far at least, has been sidestepped. Oxygenaire (London), Ltd., is a company whose name is better known in the world of medicine than in that of aviation. Being specialists in a specialized field, they are able to approach this particular problem of oxygen provision with all the ad- vantages attendant upon such specialization. Although one is apt to associate the term '' passenger '' only with adult persons, it does, m fact, embrace travellers of all ages and it is patent that the means whereby the oxygen is administered must be physically appropriate to the user. Part of this problem is fairly simply solved by provision of suitable oxygen masks, and the new "Oxyair" face mask is a great advance on anything of a similar nature that we have yet seen. The second part of the problem— that is, administering oxygen to babies—is by no means so simple of solution; however, Oxygenaire have tackled the problem with con- siderable imagination, and the real ingenuity of their solution tends to be obscured by its extreme simplicity. The intention is that the baby passenger shall be sup- plied with oxygen whilst lying in a special cot, but the part of this scheme which is of such outstand- ing interest is that the child is not enclosed in the cot; it simply lies there as in its own cot at home. Ths "Oxyair" face mask, showing the elastic single-strap attachment. Masking Advances The '' Oxyair '' face mask is a great contrast to the wartime Ser- vice mask. The airline passenger is b givep a thin, translucent, Ided plastic mask of negligible _;ht; this can be worn for con- ild*erable periods without discom- fort, and it does not interfere with the wearing of spectacles, nor do the reservoir bag or the small-bore tube for oxygen supply interfere un- duly with the wearer's movement. The mask is of the re-breathing, reservoir type, a continuous supply of oxygen being fed via the small- bore tube into the reservoir bag from the supply point adjacent to the passenger's seat. During inspiration, air is drawn in through a gauze-covered ventilation hole in the front of the mask after the oxygen in the bag has been exhausted. During expiration the relatively uncontaminated proportion of the expired breath re-enters the bag, and the remainder is expired through the ventilation hole. The gauze-covered hole —careful design and positioning of which allows the wearer to carry on conversation—provides a minimum resistance to breathing and also creates a turbulence which is an advantage at high respiratory flows; additionally, the reservoir bag has the advantage of being self-collapsible and, due to the extreme thinness of its walls, is particularly sensitive to small changes in pressure. The connection of the reservoir bag to the mask, together The open-topped " Oxycot " for baby passengers. with the positioning shape of the inlet tube, have been so designed as to avoid any possibility of accidental closure of the neck of the reservoir bag. Furthermore, the low re- sistance of the ventilation nole ensures that an ade- quate supply of air will reach the wearer should a temporary, short-duration interruption occur in the oxygen supply. The face mask is completely free from odour and taste and, due to the inert nature of the plastic material of which it is made, will not cause irritation. The an- cillary items are easily de- tachable and this, together with the smooth finish of the mask and its freedom from cavities, facilitates sterilization by washing in antiseptic solutions; the mask should not, however, be boiled. Although the basic design of the mask is such that it should be capable of snugly fitting a very much larger proportion of faces than is normally the case, it has been decided that production masks should be in large, medium and small sizes to give the widest pos- sible application. Cot Construction The '' Oxycot ' is designed to accommodate any child which can comfortably lie in a Karrikot, the dimensions of the former (32m x 14111x14111) being substantially similar to those of the latter. As shown in our detail sketch, the "Oxycot" is constructed with plastic side- and end-plates, padded with a soft, cellular wad- ding, and covered inside and out with a non-inflammable, gas-proof plastic material which is not cold to tho touch; the mattress is en- tirely similar in construction and is detachable. Sides and ends are arranged to fold inward so that stowage is facilitated, the thickness 1 "^ I for this purpose being of the order \\ I I of 3in. The weight is approxi- 11,1 f mately 4J 1b. The reason why a baby can be supplied with oxygen in the cot without any enclosing cover is, of course, that oxygen is heavier than air. Thus, so long as the child's head is below the level of the top of the cot, oxygen fed into the cot will fill it and then spill over the sides. There is no question of over-supplying the child with oxygen, for the human body- will absorb only the amount of oxygen it actually requires; thus it is that, although the normal human requires an average- oxygen concentration of 21 per cent by volume, he can breathe quite comfortably without ill effect in an atmosphere with a 50, 60 or 70 per cent oxygen content—the blood will accommo- date its requirement from the 21 per cent oxygen concentration and will reject the rest. Oxygen supply to the cot can be through a bobbin-type flow- meter carried in loop slings at the side and calibrated in litres/ minute. By this means the mother can see that her child is ob- taining oxygen, and the stewardess can make a simple check that the flow is of the required order. (The average oxygen
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