AOBPM Preventive Medicine key terms

A condition in which the tissues receive less oxygen than they need. In flight it may result from reduced oxygen pressure at altitude, lung or heart disease, or cabin depressurization, and it impairs judgment early.

The interval after loss of adequate oxygen at altitude during which a person can still take purposeful corrective action before incapacitation. It shortens rapidly as altitude increases and is reduced by exertion.

Loss of cabin pressure during flight, exposing occupants to the low pressure and oxygen levels of the outside altitude. It demands immediate use of supplemental oxygen and rapid descent to a safe breathing altitude.

The pressure exerted by the atmosphere at a given location, falling as altitude rises. It underlies altitude measurement, gas expansion in body cavities, and the partial pressure of oxygen available for breathing.

The principle that at constant temperature the volume of a gas is inversely proportional to its pressure. It explains expansion of trapped gases in the gut, sinuses, and middle ear during ascent and their contraction during descent.

Injury to gas-containing body spaces caused by pressure differences that the body cannot equalize. Common sites are the middle ear, sinuses, and lungs, producing pain, rupture, or air escape into surrounding tissues.

Illness caused by nitrogen bubbles forming in blood and tissues when ambient pressure falls too quickly, as in rapid ascent or diving followed by flight. Symptoms include joint pain, skin mottling, chest symptoms, and neurologic deficits.

The process of reducing dissolved nitrogen in the body before exposure to low pressure, usually by breathing 100 percent oxygen for a set period. It lowers the risk of decompression sickness during altitude exposure.

Oxygen supplied from a tank or generating system to raise the fraction breathed above that of ambient air. It is used to prevent hypoxia at altitude, during decompression, and for crew or passengers with cardiopulmonary impairment.

Delivery of breathing gas at pressure above ambient, requiring active exhalation. It is needed at very high altitudes or with protective equipment, and it increases breathing work and the risk of lung overpressure injury.

A pilot's mistaken perception of the aircraft's position or motion relative to the earth, usually when visual references are lost. It arises from misleading vestibular and proprioceptive signals and can lead to loss of control.

A false sensation of pitch or tilt produced by sustained linear acceleration or deceleration, such as during takeoff or braking. The pilot may perceive a climb when level or a dive when actually climbing.

The inner-ear organs that sense head rotation and linear acceleration, helping maintain balance and gaze stability. In flight without visual cues its signals can conflict with actual aircraft motion and produce illusions.

A misjudgment of distance, size, or motion caused by misleading visual cues such as featureless terrain, rain on the windshield, or runway slope. It can cause undershooting or overshooting during approach and landing.

A night landing situation with no visible ground cues between the aircraft and the runway, making the runway appear higher or closer than it is. It predisposes to a low, steep approach and touchdown short of the runway.

The study of how sustained acceleration along body axes affects circulation, vision, and consciousness. Head-to-foot acceleration reduces blood pressure at the brain, causing grayout or G-induced loss of consciousness.

Loss of consciousness from head-to-foot acceleration that lowers cerebral blood flow. Warning signs include tunnel vision and grayout; without prompt relief the pilot becomes incapacitated, often without regaining control quickly.

Garment that inflates over the legs and abdomen during high acceleration to limit blood pooling below the heart and preserve brain perfusion. It is combined with breathing maneuvers and muscle tensing for protection.

The internal roughly 24-hour cycle that governs sleep, alertness, temperature, and hormone patterns. It is reset by light and activity cues, and rapid travel across time zones or night work desynchronizes it.

A temporary sleep and alertness disturbance after rapid travel across multiple time zones, when the internal clock no longer matches local day and night. It impairs performance until the rhythm adapts.

A structured program of scheduling limits, rest opportunities, education, and reporting used to control the risk that tired crews make errors. It complements fixed duty-time rules with monitoring of actual sleep and alertness.

The branch of science concerned with how the body responds to flight environments such as low pressure, acceleration, vibration, noise, and confined space. It underpins preventive measures and medical standards for aircrew.

A sleep-wake disturbance with insomnia or excessive sleepiness linked to work hours that conflict with the normal sleep period. It causes chronic partial sleep loss and raises risk of errors and metabolic disease.

A regulatory or advisory ceiling on workplace air concentration of a hazard, usually averaged over a defined time, intended to protect most workers from harmful effects. It guides monitoring and control measures.

An exposure guideline published by a professional scientific body for airborne substances, expressed as a time-weighted average, short-term limit, or ceiling. It is advisory rather than legally enforceable and is updated as evidence changes.

A ranked approach to reducing workplace risk, from most to least effective: eliminate the hazard, substitute it, engineer controls, then administrative measures, with personal protective equipment last. It favors changes that do not depend on individual behavior.

Gear worn by a worker, such as respirators, gloves, or hearing protection, to reduce exposure to a hazard. It is the least reliable control because fit, comfort, and correct use vary and it protects only the wearer.

A written workplace program covering hazard assessment, selection of respirators, fit testing, medical evaluation, training, and maintenance. It ensures that respiratory devices actually deliver the expected protection.

Collection of air or biological measurements at the worker's breathing zone or from the worker's body over a shift. It estimates individual dose more accurately than fixed-area monitors and is compared with exposure limits.

Measurement of a substance or its metabolite in a worker's blood, urine, or exhaled breath to estimate absorbed dose. It captures exposure from all routes and reflects individual uptake rather than air concentration alone.

Systematic, repeated health checks of workers exposed to specific hazards, such as audiometry for noise or spirometry for dust, to detect early change. It supports prevention and does not replace exposure control.

Asthma caused or worsened by workplace exposures such as isocyanates, flour dust, or animal proteins. It often shows symptoms that improve away from work, and early removal from exposure improves the chance of recovery.

Development of an immune response to an agent after prior exposure, so that later contact triggers reactions at much lower levels. Once it occurs, exposure must be avoided because symptoms can worsen with each exposure.

Permanent hearing damage from prolonged or intense sound exposure, typically starting at high frequencies and impairing speech understanding. It is preventable through engineering controls, hearing protection, and audiometric monitoring.

The net load on the body from environmental heat, metabolic work, and clothing, which can overwhelm cooling and cause heat exhaustion or heat stroke. Acclimatization, fluid replacement, and work-rest cycles reduce risk.

Physiologic adjustment to a repeated environmental stress such as heat or high altitude, improving tolerance over days to weeks. In heat it increases sweating and lowers salt loss; it fades after exposure stops.

The number of new cases of a condition in a defined population divided by the person-time at risk during a stated period. It measures how fast new disease develops and is used to compare risk between groups.

The proportion of a population that has a condition at a given time, counting both new and existing cases. It reflects disease frequency and duration and is useful for planning health services.

The proportion of a defined group that becomes ill during a limited outbreak, usually after a common exposure. It is a form of incidence used to identify the source and mode of transmission.

The ratio of the risk of an outcome in an exposed group to the risk in an unexposed group. A value above one suggests increased risk, and it is calculated directly in cohort studies.

The ratio of the odds of exposure among cases to the odds among controls, used to estimate association in case-control studies. It approximates relative risk when the outcome is rare.

A distortion of an exposure-outcome association by a third factor that is related to both and is not part of the causal pathway. It is addressed in design by restriction or matching and in analysis by adjustment.

A systematic error arising when the groups compared differ in ways related to both exposure and outcome because of how participants were chosen or retained. It cannot usually be corrected by statistical adjustment after the fact.

Testing apparently healthy people to find unrecognized disease at a stage when treatment is more effective. It requires a suitable test, an accepted treatment, and evidence that early detection improves outcomes.

The proportion of people who truly have a condition and are correctly identified by a test. A highly sensitive test yields few false negatives and is favored when missing disease is dangerous.

The proportion of people without a condition who are correctly identified as negative by a test. A highly specific test yields few false positives and is favored when a positive result triggers harmful or costly action.

The probability that a person actually has, or does not have, a condition given a positive or negative test result. It depends on test sensitivity and specificity and on how common the condition is in the tested population.

The apparent survival gain produced only by detecting disease earlier, without any postponement of death. It makes screening look beneficial when the time of diagnosis shifts but the outcome does not change.

A structured response to excess cases of a disease, involving case definition, case finding, descriptive analysis, hypothesis testing, and control measures. Its goal is to stop transmission and identify preventable causes.

Indirect protection of susceptible people that arises when a sufficient proportion of a population is immune, reducing transmission. The threshold varies with how contagious the pathogen is.

Administration of a preparation that stimulates protective immunity against a pathogen without causing the disease. Population programs reduce incidence and can eliminate or eradicate a disease where coverage is sustained.

Measures taken before disease occurs to prevent its onset, such as immunization, hazard control, or health education. It acts on healthy people and on the environment rather than on existing illness.

Early detection and prompt treatment of disease that has begun but is not yet symptomatic or advanced, such as screening programs. Its aim is to halt progression and improve prognosis.