AOBPM Preventive Medicine flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Boyle's law in aviation

At constant temperature, gas volume is inversely proportional to pressure. Trapped gas expands on ascent and contracts on descent, causing barotrauma of ears, sinuses, and gut.

Dalton's law

Total pressure of a gas mixture equals the sum of partial pressures. Alveolar oxygen depends on inspired oxygen fraction and barometric pressure, not altitude per se.

Henry's law

Amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid. Underlies nitrogen loading and unloading in decompression illness.

Decompression sickness type II

Form of DCS with neurologic, pulmonary, or cardiovascular involvement. It is more severe than type I musculoskeletal bends and requires urgent recompression therapy.

Arterial gas embolism

Gas bubbles entering arterial circulation after pulmonary barotrauma, causing sudden neurologic deficits within minutes of surfacing. Treated with hyperbaric oxygen and recompression.

Time of useful consciousness

Interval after loss of supplemental oxygen at altitude before performance degrades. It falls steeply above FL 350, reaching tens of seconds at very high cabin altitudes.

Somatogravic illusion

Vestibular misperception of linear acceleration as pitch or bank, causing pilots to misjudge attitude without visual reference. A common cause of spatial disorientation accidents.

G-LOC

G-induced loss of consciousness from cerebral hypoperfusion during sustained +Gz. Preceded by greyout and tunnel vision (almost-LOC) before full unconsciousness.

OSHA PEL vs NIOSH REL

PELs are legally enforceable exposure limits; RELs and ACGIH TLVs are health-based recommendations. The distinction matters when comparing regulatory and best-practice standards.

WBGT index

Wet bulb globe temperature combining dry-bulb, natural wet-bulb, and black-globe temperatures. Used to set work-rest cycles and fluid replacement in heat stress.

Standard threshold shift

Averaged hearing loss of at least 10 dB at 2000, 3000, and 4000 Hz compared with baseline. Triggers OSHA follow-up and hearing conservation actions.

Lead medical removal

OSHA removal threshold for blood lead at 50 µg/dL or higher (or averaged 60 µg/dL). Chelation is reserved for symptomatic or very high levels.

Asbestosis

Diffuse interstitial pulmonary fibrosis from cumulative asbestos exposure. Pleural plaques indicate exposure but do not themselves indicate fibrosis severity.

Silicosis

Fibrotic lung disease from inhaled crystalline silica. Chronic simple form follows long low-intensity exposure; risk of tuberculosis is increased in all forms.

Carbon monoxide affinity

CO binds hemoglobin roughly 200-250 times more avidly than oxygen. Symptoms include headache, nausea, and confusion; treat with high-flow oxygen.

Organophosphate poisoning

Cholinergic crisis from acetylcholinesterase inhibition, causing SLUDGE and DUMBELS effects. Atropine treats muscarinic effects; pralidoxime treats nicotinic effects.

Incidence vs prevalence

Incidence counts new cases over a period; prevalence counts existing cases. For stable disease, prevalence approximates incidence multiplied by average duration.

Relative risk

Ratio of disease incidence in exposed to incidence in unexposed, used in cohort studies. A value of 1.0 indicates no association between exposure and outcome.

Odds ratio

Ratio of odds of exposure in cases to odds in controls, used in case-control studies. Approximates relative risk when the disease is rare.

Sensitivity

Proportion of truly diseased people who test positive (TP divided by TP plus FN). High sensitivity is useful for ruling out disease when negative.

Specificity

Proportion of truly disease-free people who test negative (TN divided by TN plus FP). High specificity is useful for confirming disease when positive.

Positive predictive value

Proportion of test-positive people who actually have disease. It depends strongly on disease prevalence, unlike sensitivity and specificity.

Herd immunity threshold

Fraction of a population that must be immune to interrupt transmission, approximated as 1 minus 1/R0. Higher R0 requires higher coverage.

Primordial prevention

Prevention of risk factor emergence at the population level, such as policies discouraging smoking initiation. It precedes primary prevention of established risk factors.

Secondary prevention

Early detection and treatment of preclinical disease to improve outcomes, such as screening programs. It targets the detectable latent stage of disease.

Tertiary prevention

Reducing disability and improving function after disease is established, such as rehabilitation. It limits consequences rather than preventing onset.

Screening criteria

Conditions for a valid screening program: important disease, accepted treatment, detectable latent stage, suitable test, understood natural history, and cost-effectiveness.

Point source epidemic curve

Epidemic curve with a single sharp peak occurring within one incubation period of exposure. Indicates a brief common exposure rather than ongoing transmission.

Propagated outbreak curve

Epidemic curve with successive peaks spaced about one incubation period apart. Indicates person-to-person transmission rather than a single common exposure.

Selection bias

Systematic error from how participants are chosen, producing groups not comparable on other risk factors. It cannot be corrected by increasing sample size alone.

Confounding

A third variable associated with both exposure and outcome that distorts the observed association. Addressed by design (randomization) or analysis (stratification, adjustment).

Attributable risk

Difference in disease incidence between exposed and unexposed groups. Estimates the excess disease burden attributable to the exposure in the exposed population.