A hypobaric chamber, or altitude chamber, is a chamber used during
aerospace
Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...
or high terrestrial altitude research or training to simulate the effects of
high altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
on the human body, especially
hypoxia (low oxygen) and hypobaria (low ambient air pressure). Some chambers also control for
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and
relative humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
Humidity depe ...
.
Procedure
One or more subjects (usually,
pilots
An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators, because they a ...
or crew members, though anyone interested in the effects of high altitude can usually arrange a visit) are placed in the chamber. Before "ascending" to the desired
altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
, subjects breathe oxygen from
oxygen masks to purge
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
from their bloodstream so
decompression sickness
Decompression sickness (abbreviated DCS; also called divers' disease, the bends, aerobullosis, and caisson disease) is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompressio ...
(DCS) does not occur. With masks in place, the
atmospheric pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...
inside the chamber is then reduced to simulate altitudes of up to tens of thousands of feet. The subjects then remove their
oxygen masks and experience the symptoms of
hypoxia. An inside safety observer, breathing oxygen by mask, should always be present to place a subject's mask back on in the event a subject passes out
unconscious
Unconscious may refer to:
Physiology
* Unconsciousness, the lack of consciousness or responsiveness to people and other environmental stimuli
Psychology
* Unconscious mind, the mind operating well outside the attention of the conscious mind a ...
. Outside observers monitor the subjects' condition via closed circuit television and viewing ports.
While the masks are off, subjects may be asked to do trivial tasks, such as arithmetic and signing their own names. When such tasks start taking excessive lengths of time to be done or are done poorly, it is usually a sign that the "
Time of Useful Consciousness
Time of useful consciousness (TUC), also effective performance time (EPT), is defined as the amount of time an individual is able to function effectively (e.g. perform flying duties) in an environment of inadequate oxygen supply. It is the period ...
" has been exceeded and that the masks should be replaced. Subjects may also ensure that they are able to do tasks such as clear their nose and sinuses easily, as pain from such problems can be a major distraction in an emergency such as
rapid decompression
Uncontrolled decompression is an unplanned drop in the pressure of a sealed system, such as an aircraft cabin or hyperbaric chamber, and typically results from human error, material fatigue, engineering failure, or impact, causing a pressure vesse ...
.
Use in training
The primary purpose of the altitude chamber is for the subjects to learn what their hypoxia symptoms are. The symptoms of hypoxia are different for each individual, and this training is helpful for aviators to be able to recognize these symptoms during actual flight so as to avoid in-flight oxygen emergencies. Military pilots who fly aircraft at altitudes in excess of 10,000 feet, and civilian pilots who fly unpressurized aircraft above 12,500 feet, must use oxygen equipment. Altitude chamber training is required of
U.S. military aviators every five years. The
FAA
The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
and some larger
airline
An airline is a company that provides civil aviation, air transport services for traveling passengers and freight. Airlines use aircraft to supply these services and may form partnerships or Airline alliance, alliances with other airlines for ...
s also require their pilots to periodically take altitude chamber training. Anyone with a pilot certificate in the United States who has a
current Class I or Class II medical certificate can normally sign up and receive altitude training from several commercial facilities and a very limited availability from a government facility.
There are many procedures followed during chamber training for aircrew. Usually new aircrew will undergo a familiarization profile, where the chamber ascends to an altitude of 10,000 ft. During the ascent they are instructed on the proper procedure to clear the ears. During ascent, students are asked to yawn and on descent they need to perform the
valsalva maneuver
The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air out as if blowing up a balloon. Variations of the maneuver can ...
. If they perform the valsalva during ascent, they risk suffering barotrauma of the ear. This is because the ears are susceptible to
Boyle's Law
Boyle's law, also referred to as the Boyle–Mariotte law, or Mariotte's law (especially in France), is an experimental gas law that describes the relationship between pressure and volume of a confined gas. Boyle's law has been stated as:
The ...
.
There are also other profiles, such a hypoxia training profile, where the chamber ascends to an altitude of 25,000 ft. Upon arriving at 25,000 ft, students are removed from their oxygen supply two at a time, for around 2 to 3 minutes. During this time, they will be asked to complete simple tasks such as copying shapes on a piece of paper. They are asked during the time off oxygen how they feel. After being placed back on oxygen, they will understand how their judgement was impaired during the time that they were experiencing hypoxia.
The training goes further with rapid decompression profiles, where the chamber is very rapidly ascended from 8,000 ft to 22,000 ft within 10 to 20 seconds, to simulate the loss of a cabin door. For fighter pilots this is done from an altitude of 25,000 ft to 43,000 ft within 5 seconds which simulates the loss of a fighter aircraft's canopy.
Hypobaric chambers are also finding increasing use as a means of improving athletic performance. Since the human body adapts to extended mild hypoxia by increasing the quantity of red cells in the blood and this raises aerobic performance, athletes sleep in them as part of their training regimen. This has roughly the same effect as training in high altitudes, but the use of hypobaric chambers plays into the controversial issue of enhanced athletic performance. Mika LaVaque-Manty asks in his book, "Are hypobaric chambers, which simulate high-altitude conditions, a natural way to improve your body?" This hints that the hypobaric chambers use can be likened to blood doping and thus be deemed an unfair athletic advantage. This could lead to a ban on hypobaric chambers for athletic training.
Institutions with hypobaric chambers
Centro de Medicina Aeroespacial de la Fuerza Aerea Colombiana Aviation medicine, physiological, and hypobaric services
Aviation medicine training and hypobaric services
*
U.S. Army Institute of Environmental Medicine,
Natick, MA
Natick ( ) is a town in Middlesex County, Massachusetts, United States. It is near the center of the MetroWest region of Massachusetts, with a population of 37,006 at the 2020 census. west of Boston, Natick is part of the Greater Boston area. ...
, ''33 years experience with its Hypobaric Chamber Facility''
*
Sheppard Air Force Base
Sheppard Air Force Base is a United States Air Force (USAF) base located north of the central business district of Wichita Falls, in Wichita County, Texas, United States. It is the largest training base and most diversified in Air Educati ...
in Wichita Falls, Texas.
*
University of North Dakota
The University of North Dakota (also known as UND or North Dakota) is a public research university in Grand Forks, North Dakota. It was established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of ...
's
John D. Odegard School of Aerospace Sciences
The John D. Odegard School of Aerospace Sciences (UND Aerospace) is a multidisciplinary college within the University of North Dakota (UND) in Grand Forks, North Dakota. The school was formed in 1968. The majority of the school's fleet of over 120 ...
, Aviation Training
Naval Operational Medicine Institute Operational medical and survival training and consultative services to military forces worldwide
Aircrew training, research, and other uses
National AeroSpace Training And Research (NASTAR) Center South Air and space training, research, and education
*
RAF Centre of Aviation Medicine
The RAF Centre of Aviation Medicine (RAF CAM) is a medical organisation run by the Royal Air Force and based at RAF Henlow in Bedfordshire. It is the main organisation conducting aviation medicine research in the UK.
History Formation
The centr ...
Center for Man in Aviation, Royal Netherlands Air Force Aircrew training, physiology, research and certification of equipment
*
University Hospitals Cleveland Medical Center
University Hospitals Cleveland Medical Center (UH Cleveland Medical Center) is a large not-for-profit academic medical complex in Cleveland, Ohio, United States. University Hospitals Cleveland Medical Center is the main affiliate hospital of Ca ...
in
Cleveland, Ohio
Cleveland ( ), officially the City of Cleveland, is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located in the northeastern part of the state, it is situated along the southern shore of Lake Erie, across the U.S. ...
, aerospace physiology research
* AXA Training Center, Training ground of
Liverpool F.C
Liverpool Football Club is a professional Football club (association football), football club based in Liverpool, England. The club competes in the Premier League, the top tier of English football league system, English football. Founded in ...
.
See also
*
Hyperbaric chamber
A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of ...
. In contrast to ''hypo''baric chambers, a
''hyper''baric chamber places subjects under increased atmospheric pressure or increased
oxygen saturation
Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
, or both, for purposes including improved wound healing.
Notes
External links
{{commons and category
Altitude Chamber Training FacilityAltitude Chamber manufacturer
Aviation medicine