Altitude chamber
Encyclopedia
Aerospace physiology
Aerospace physiology refers to effects on the human body caused by characteristics of the aerospace environment.This subject includes, but is not limited to, the following topics:* Spatial disorientation and airsickness* Vestibular system...
or high terrestrial altitude research or training to simulate the effects of high altitude on the human body, especially hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
(low oxygen) and hypobaria (low ambient air pressure). Some chambers also control for temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and relative humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
.
Procedure
One or more subjects (usually, pilots 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 altitudeAltitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
, subjects breathe oxygen from oxygen mask
Oxygen mask
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 or the entire face...
s to purge nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
from their bloodstream so decompression sickness
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
(DCS) does not occur. With masks in place, the atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
inside the chamber is then reduced to simulate altitudes of up to tens of thousands of feet. The subjects then remove their oxygen mask
Oxygen mask
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 or the entire face...
s and experience the symptoms of hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
. 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
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...
. Outside observers monitor the subjects' condition via closed circuit television and viewing ports.
While the mask is off, subjects may be asked to do trivial tasks, such as arithmetic and signing their own name. 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
Time of useful consciousness is defined as the amount of time an individual is able to perform flying duties efficiently in an environment of inadequate oxygen supply...
" has been exceeded and that the mask should be replaced. Subjects may also insure 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.
Use in training
The primary purpose of the altitude chamber is for the subjects to determine 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. militaryMilitary of the United States
The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...
aviators every five years. The FAA
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
and some larger airline
Airline
An airline provides air transport services for traveling passengers and freight. Airlines lease or own their aircraft with which to supply these services and may form partnerships or alliances with other airlines for mutual benefit...
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 the government.
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 10,000ft. 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
Valsalva maneuver
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut...
. 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
Boyle's law is one of many gas laws and a special case of the ideal gas law. Boyle's law describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system...
.
There are also other profiles, such a hypoxia training profile, where the chamber ascends to an altitude of 25,000ft. Upon arriving at 25,000ft, 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 see 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 8,000ft to 22,000ft within 10 to 20 seconds, to simulate the loss of a cabin door. For fighter pilots this is done from an altitude of 25,000ft to 43,000ft 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.
Institutions with hypobaric chambers
- Royal New Zealand Air Force Aviation Medicine Unit provides aviation medicine training to aircrew and hypobaric services
- U.S. Army Institute of Environmental MedicineUnited States Army Research Institute of Environmental MedicineThe United States Army Research Institute of Environmental Medicine is the U.S Army’s main institution and facility for military environmental medicine and exercise physiology research. It is located at Natick, MA within the U.S. Army Soldier Systems Center installation, but is a subordinate lab...
, Natick, MANatick, MassachusettsNatick is a town in Middlesex County, Massachusetts, United States. Natick is located near the center of the MetroWest region of Massachusetts, with a population of 33,006 at the 2010 census. Only west from Boston, Natick is considered part of the Greater Boston area...
, 33 years experience with its Hypobaric Chamber Facility - University of North DakotaUniversity of North DakotaThe University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest and largest university in the state and enrolls over 14,000 students. ...
's John D. Odegard School of Aerospace SciencesJohn D. Odegard School of Aerospace SciencesThe John D. Odegard School of Aerospace Sciences is a part of the University of North Dakota in Grand Forks, North Dakota. The school was formed in 1968. The school's fleet of 120 aircraft is based at nearby Grand Forks International Airport and is the largest fleet of civilian flight training...
, Aviation Training - Naval Operational Medicine Institute provides operational medical and survival training and consultative services to military forces worldwide.
- Arizona State University Polytechnic Campus Aircrew training, research, and other uses. Available to the public by appointment.
External links
- Industrial Altitude Chamber Manufacturer
- Altitude Chamber Training Facility
- Hyperbaric chamber, in contrast to hypobaric chambers, these place subjects under increased atmospheric pressure.