Home › Reference › Glossary

Glossary & Acronyms

Glossary stub: 40 of a planned ≈150 terms. Definitions pending editorial review. Metadata CC0.

ACLS — Advanced cardiovascular life support

Hospital-level resuscitation algorithms (airway, defibrillation, cardiac drugs). Used as a training and equipment benchmark for crew medical officers and launch/landing medical teams.

AED — Automated external defibrillator

Portable device that analyzes heart rhythm and delivers a shock for ventricular fibrillation or pulseless ventricular tachycardia; flown on the International Space Station and stocked on landing-site emergency carts.

ALARA — As low as reasonably achievable

Radiation-protection principle: keep exposure as low as reasonably achievable even when below limits; required for NASA crews ([V1 4029]). space-radiation

ARED — Advanced Resistive Exercise Device

ISS resistance-exercise machine providing loads up to 600 lbf; associated with better bone and muscle protection than earlier devices. bone-loss

ATLS — Advanced trauma life support

Structured approach to the injured patient. NASA-STD-3001 requires launch/landing rescue assets to have ATLS-equivalent capability until hand-off to a definitive medical care facility.

CDP — Computerized dynamic posturography

Platform-based balance test that changes visual and support-surface cues to measure how well a person uses vision, inner ear (vestibular) and body-position senses; used before and after flight.

CHeCS — Crew Health Care System

The U.S. medical, environmental-monitoring and countermeasure hardware system on the International Space Station, including its medical kits, defibrillator, respiratory support and patient restraint.

CMO — Crew Medical Officer

Crewmember (usually not a physician) trained to deliver medical care in flight under ground flight-surgeon guidance; NASA requires at least two per vehicle.

CPET — Cardiopulmonary exercise test

Exercise test with breath-by-breath gas analysis that measures peak oxygen uptake (VO2 peak/VO2max) and how the heart, lungs and muscles respond to effort; used to document aerobic capacity before and after flight.

DCS — Decompression sickness

Illness from dissolved inert gas (nitrogen) forming bubbles when ambient pressure falls — in divers, aviators, and astronauts moving from cabin pressure to a low-pressure spacesuit.

DMCF — Definitive medical care facility

Pre-arranged, trauma-capable hospital that receives crew after launch or landing emergencies.

DXA — Dual-energy X-ray absorptiometry

Low-dose X-ray scan measuring bone mineral density (T- and Z-scores); NASA uses it for selection, triennial surveillance and post-flight follow-up. bone-loss

ECG — Electrocardiogram

Recording of the heart's electrical activity. A resting 12-lead ECG is part of astronaut and commercial orbital-passenger screening; a 24-hour ambulatory (Holter) ECG is used around long missions.

ETCO2 — End-tidal carbon dioxide

Carbon dioxide measured at the end of each breath (capnography); used to confirm airway tube placement and monitor ventilation.

EVA — Extravehicular activity

Activity performed by an astronaut outside a spacecraft, commonly called a spacewalk.

ExMC — Exploration Medical Capability

NASA Human Research Program element that studies and designs the medical system (people, training, equipment, drugs, data) for missions beyond low Earth orbit.

GCR — Galactic cosmic rays

High-energy charged particles originating outside the solar system, including heavy (HZE) ions. space-radiation

Holter — Ambulatory (24-hour) ECG monitor

Wearable ECG recorder worn for about 24 hours (or longer) to capture rhythm disturbances that a short resting ECG can miss.

HSP — Health Stabilization Program

Preflight measures (e.g., limiting contacts, screening) that reduce the chance crew carry infectious disease into flight.

IIH — Idiopathic intracranial hypertension

Raised intracranial pressure without a mass lesion, causing papilledema and headache; shares some findings with SANS but is a different condition. sans

ILMA — Intubating laryngeal mask airway

Supraglottic airway that sits over the larynx without entering the trachea and also allows a breathing tube to be passed through it; chosen for the space station because it is easier for non-specialists than standard intubation.

IMM — Integrated Medical Model

NASA probabilistic model that estimates how often about 100 medical conditions are likely to occur on a given mission and what resources would be needed to treat them; used to size medical kits.

LBNP — Lower body negative pressure

Device applying suction to the lower body to pull fluid toward the legs; studied as a countermeasure for headward fluid shift and SANS. sans

LEO — Low Earth orbit

Earth orbit at altitudes up to about 2,000 km; the ISS orbits in LEO.

LOC — Level of care (NASA-STD-3001, historical)

Five-tier scale (Level I first aid to Level V physician-led autonomous care) that NASA-STD-3001 Vol. 1 Rev A (2014) used to match medical capability to mission type; replaced in Rev B (2022) by risk-based health and medical care requirements but still widely cited.

OCHMO — Office of the Chief Health and Medical Officer

NASA office that owns NASA-STD-3001 and publishes its technical briefs.

OCT — Optical coherence tomography

Non-invasive retinal and optic nerve imaging; used in flight and on the ground to detect optic disc edema and choroidal folds in SANS. sans

OI — Orthostatic intolerance

Inability to maintain blood pressure and cerebral perfusion when upright, causing lightheadedness or fainting; common after returning from spaceflight. orthostatic-intolerance

PMC — Private medical conference

Confidential crew-to-flight-surgeon medical consultation during a mission.

POCUS — Point-of-care ultrasound

Ultrasound performed and interpreted at the bedside by the treating clinician; on the ISS, often acquired by non-physician crew under remote guidance.

PRA — Probabilistic risk assessment

Method that combines likelihood and consequence estimates to quantify risk. NASA-STD-3001 Rev B onward uses PRA to tailor a mission's medical capability.

Prebreathe — Oxygen prebreathe

Breathing 100% oxygen before decompression to wash nitrogen out of tissues and reduce the risk of decompression sickness before a spacewalk.

REID — Risk of exposure-induced death

Estimated added lifetime probability of dying from cancer caused by a radiation exposure; NASA's career limit is set to keep mean REID under 3%. space-radiation

RIDGE — Radiation, Isolation, Distance, Gravity, Environment

NASA's five-hazard framework for human spaceflight.

SANS — Spaceflight-associated neuro-ocular syndrome

Ophthalmic and neuro-ophthalmic findings associated with long-duration spaceflight; formerly called VIIP. sans

SFP — Spaceflight participant

A non-professional crew member, e.g. on a commercial flight.

SMS — Space motion sickness

Motion-sickness symptoms during early adaptation to weightlessness. space-motion-sickness

SPE — Solar particle event

An episode of elevated energetic particle (mainly proton) flux from the Sun, often associated with flares and coronal mass ejections. space-radiation

SpO2 — Peripheral oxygen saturation

Blood oxygen saturation measured non-invasively with a pulse oximeter clipped to a finger or ear.

VGE — Venous gas emboli

Gas bubbles in venous blood after decompression, detectable by Doppler or ultrasound; often asymptomatic and used to gauge decompression stress.