Oxygen mask

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A plastic oxygen mask on an ER patient.
A plastic oxygen mask on an ER patient.

An oxygen mask provides a method to transfer breathing oxygen gas from a storage tank to the lungs. Oxygen masks may cover the nose and mouth (oral nasal mask) or the entire face (full-face mask). They may be made of plastic, silicone, or rubber.

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[edit] Medical plastic oxygen masks

Plastic masks are used primarily by medical care providers for oxygen therapy because they are disposable and so reduce cleaning costs.[1] As they are light in weight, they are more comfortable than some other masks, increasing patient acceptance. Transparent plastic masks also leave the face visible, allowing care providers to better ascertain patients’ conditions.

[edit] Silicone and rubber masks

Breathing 100% oxygen from a tightly-fitting aviators’ oxygen mask
Breathing 100% oxygen from a tightly-fitting aviators’ oxygen mask

Silicone and rubber oxygen masks are heavier than plastic masks. They are designed to provide a good seal for long-duration use by aviators, medical researcher subjects, and hyperbaric chamber and other patients that require administration of pure oxygen, such as carbon monoxide poisoning and decompression sickness victims.[2] Valves inside these tight-fitting masks control the flow of gases into and out of the masks, so that rebreathing of exhaled gas is minimised, thus optimising oxygen delivery.

[edit] Hoses and tubing and oxygen regulators

Hoses or tubing connect an oxygen mask to the oxygen supply. Hose is larger in diameter then tubing and can allow greater oxygen flow. When hose is used it may have a ribbed or corrugated design to allow bending of the hose while preventing twisting and cutting off the oxygen flow. The quantity of oxygen delivered from the storage tank to the oxygen mask is controlled by a valve called a regulator. Some types of oxygen masks have a breathing bag made of plastic or rubber attached to the mask or oxygen supply hose to store a supply of oxygen to allow deep breathing without waste of oxygen with use of simple fixed flow regulators.

[edit] Aviators’ masks

Aviators’ pressure-demand oxygen mask, showing sponge-rubber facial seal and inhalation valves. The exhalation valve is below the center of the mask.
Aviators’ pressure-demand oxygen mask, showing sponge-rubber facial seal and inhalation valves. The exhalation valve is below the center of the mask.

Three main kinds of oxygen masks are used by pilots and crews who fly at high altitudes: continuous flow, diluter demand, and pressure demand.[3]

A continuous-flow mask is usually equipped with a rebreather bag (recognizable from airline demonstrations) which recycles part of the exhaled air and saves oxygen. This type of mask is used by general-aviation aircraft flying above 12500 feet MSL (up to about 25000 MSL) and in the cabins of passenger craft.[3][4][5]

Diluter-demand and pressure-demand masks supply oxygen only when the user inhales.[6] They each require a good seal between the mask and the user’s face.

In a diluter-demand system, as the altitude increases (ambient pressure, and therefore the partial pressure of ambient oxygen, decreases), the oxygen flow increases such that the partial pressure of oxygen is roughly constant. Diluter-demand oxygen systems can be used up to 34000 feet.

In a pressure-demand system, oxygen in the mask is above ambient pressure, permitting breathing above 34000 feet. Because the pressure inside the mask is greater than the pressure around the user’s torso, inhalation is easy, but exhalation requires more effort. Aviators are trained in pressure-demand breathing in altitude chambers. Because they seal tightly, pressure-demand-type oxygen masks are also used in hyperbaric oxygen chambers and for oxygen breathing research projects with standard oxygen regulators.[2]

Aviators' oxygen masks often contain a microphone for talking on the plane's two-way radio.

They are often part of a pressure suit.

[edit] Aviation passenger masks and emergency oxygen systems

Main article: Emergency oxygen system
Emergency oxygen masks deployed
Emergency oxygen masks deployed

Most commercial aircraft are fitted with oxygen masks for use when cabin pressurization fails.[4][5] In general, commercial aircraft are pressurized so that the cabin air is at a pressure equivalent to about 8,000 feet altitude, where one can breathe normally without an oxygen mask. If the oxygen pressure in the cabin drops below a safe level, risking hypoxia, compartments containing the oxygen masks will open automatically, either above or in front of the passenger and crew seats, and in the lavatories.

In the early years of commercial flight, before pressurized cabins were invented, airliner passengers sometimes had to wear oxygen masks during routine flights.

[edit] Self-contained breathing apparatus (SCBA)

Firefighters and emergency service workers use full face masks that provide breathing air and eye and face protection.[7] These masks are typically attached to a tank carried upon the back of the wearer and are called self-contained breathing apparatuses (SCBA).[8] Because oxygen breathing is hazardous in areas where fires may be burning, SCBA units are normally filled with compressed breathing air rather than oxygen.

[edit] Specialized masks for divers and astronauts

Specialized full-face masks that supply oxygen or other breathing gases are used by divers and astronauts to remove nitrogen from their blood before space walks (EVA) or underwater decompression.[9]

[edit] Anaesthesia oxygen masks

Face masks that are designed to provide general anaesthesia inhalation gas to operative patients are called anaesthesia masks.[1] These masks are made of materials (anti static rubber or silicon) that are resistant to creating a spark or static electric discharge. The masks often use a Y fitting upon the mask and a double breathing hose system. One hose supplies breathing gas and oxygen from a anaesthesia machine , the other hose brings the exhaled gas back to the anaesthesia machine. These masks can be fitted with a exhalation valve and inhalation breathing bag to provide high oxygen inhalation levels for 100% oxygen breathing for carbon monoxide poisoning victims. They are fitted with 4 point head straps to provide a tight seal against the face.

[edit] Masks for high-altitude climbers

Oxygen masks are used by climbers of high peaks such as Mt. Everest.[10] The tanks are made of light-weight, high-strength metals and are covered in high-strength fiber such as kevlar. The special bottles are filled with oxygen at very high pressure which provides a longer time duration of oxygen for breathing then standard pressure bottles. These systems are generally only used above 7000 meters.

[edit] Oxygen helmets

Oxygen helmets are used in hyperbaric oxygen chambers for oxygen administration.[2] They are transparent light weight plastic helmets with a seal that goes around the wearers neck that looks like a space suit helmet. They offer a good visual field. Light weight plastic hoses provide oxygen to the helmet and remove exhaled gas to the outside of the chamber. Oxygen helmets are often preferred for oxygen administration in hyperbaric oxygen chambers for children and patients that are uncomfortable wearing a oxygen mask.

[edit] Mask retention systems

Medical oxygen masks are held in place by medical personnel or the user by hand, or they may be fitted with a light weight elastic headband so the mask can be removed quickly. Full-face masks are secured by several straps. Tightly fitting oxygen masks are secured at four points by two head straps. Aviators’ masks are often equipped with “quick don” harnesses that allow those in pressurized aircraft to rapidly don the masks in emergencies. Military aviators’ oxygen masks are secured to flight helmets with quick-release systems.

[edit] See also

[edit] References

  1. ^ a b Sim MA, Dean P, Kinsella J, Black R, Carter R, Hughes M (September 2008). "Performance of oxygen delivery devices when the breathing pattern of respiratory failure is simulated". Anaesthesia 63 (9): 938–40. doi:10.1111/j.1365-2044.2008.05536.x. PMID 18540928. Retrieved on 2008-08-31. 
  2. ^ a b c Stephenson RN, Mackenzie I, Watt SJ, Ross JA (September 1996). "Measurement of oxygen concentration in delivery systems used for hyperbaric oxygen therapy". Undersea Hyperb Med 23 (3): 185–8. PMID 8931286. Retrieved on 2008-08-31. 
  3. ^ a b FAA. "Equipment standards for oxygen dispensing units.". FAA.gov. Retrieved on 2008-08-31.
  4. ^ a b Brantigan JW (March 1980). "Investigation of flow rates of oxygen systems used in general aviation". Aviat Space Environ Med 51 (3): 293–4. PMID 6444812. 
  5. ^ a b Olson RM (April 1976). "Economical oxygen-delivery system". Aviat Space Environ Med 47 (4): 449–51. PMID 1275837. 
  6. ^ FAA. "Technical Standard Order - Subject: TSO-C89, OXYGEN REGULATORS, DEMAND". FAA.gov. Retrieved on 2008-08-31.
  7. ^ Dreger RW, Jones RL, Petersen SR (August 2006). "Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake". Ergonomics 49 (10): 911–20. doi:10.1080/00140130600667451. PMID 16803723. Retrieved on 2008-08-31. 
  8. ^ Campbell DL, Noonan GP, Merinar TR, Stobbe JA (April 1994). "Estimated workplace protection factors for positive-pressure self-contained breathing apparatus". Am Ind Hyg Assoc J 55 (4): 322–9. PMID 8209837. 
  9. ^ Norfleet WT, Hickey DD, Lundgren CE (November 1987). "A comparison of respiratory function in divers breathing with a mouthpiece or a full face mask". Undersea Biomed Res 14 (6): 503–26. PMID 3120386. Retrieved on 2008-08-31. 
  10. ^ Windsor JS, Rodway GW (2006). "Supplemental oxygen and sleep at altitude". High Alt. Med. Biol. 7 (4): 307–11. doi:10.1089/ham.2006.7.307. PMID 17173516. Retrieved on 2008-08-31. 
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