CFRN key terms

Oxygen is scarce in the inhaled gas or the lungs fail to move it into the blood, lowering arterial oxygen content. Causes include high cabin altitude, airway obstruction, drowning, and pneumonia.

The blood cannot carry its normal oxygen load even though the lungs and inhaled air are adequate. Anemia, carbon monoxide poisoning, methemoglobinemia, and massive hemorrhage are typical causes.

Oxygen delivery fails because blood flow itself is too low, as in shock, heart failure, cardiac arrest, or an occluded vessel. Oxygen content may be normal while tissues still starve.

Cells cannot use the oxygen delivered to them because a toxin disrupts cellular respiration, as with cyanide or severe sepsis. Arterial oxygen levels may appear normal while tissue metabolism fails.

The window after oxygen supply is lost in which a person can still act purposefully before becoming incapacitated. It shortens rapidly with altitude, so oxygen and descent are urgent.

The effective altitude inside a pressurized cabin, usually kept between about 5,000 and 8,000 feet. It sets the oxygen partial pressure that the patient and crew actually breathe in flight.

In a gas mixture, total pressure equals the sum of the partial pressures of each gas present. This explains why oxygen partial pressure falls with altitude even though oxygen remains 21 percent of air.

At a constant temperature, gas volume is inversely proportional to pressure. During ascent, trapped gas expands in ears, sinuses, lungs, cuffs, and tubing, causing barotrauma or equipment failure.

The amount of gas dissolved in a liquid rises with that gas's partial pressure. When ambient pressure drops quickly, dissolved nitrogen forms bubbles, which is the basis of decompression sickness.

Injury to gas-filled body spaces when pressure cannot equalize during ascent or descent. It causes ear and sinus pain, eardrum rupture, or lung injury with pneumothorax.

Illness from nitrogen bubbles forming in tissues and blood after a rapid pressure drop. Joint pain, respiratory symptoms, and neurological deficits appear; treatment includes oxygen, descent, and recompression.

A mismatch between sensed and actual orientation or motion, arising when visual references are poor and vestibular cues mislead. Pilots must trust instruments and avoid abrupt head movements.

Conflict between the body's internal clock and the sleep-wake schedule imposed by shifts and night flights. It reduces alertness, slows reaction time, and increases the risk of error.

A rapid first pass through airway, breathing, circulation, disability, and exposure that finds and treats immediately life-threatening problems before any detailed examination is begun.

A head-to-toe examination plus history performed after life threats are managed. It looks for injuries or conditions that could worsen during flight, such as hidden bleeding or a changing neuro exam.

A 3 to 15 point score of eye, verbal, and motor responses that quantifies level of consciousness and, when repeated, reveals neurologic trends over time.

Heart rate divided by systolic blood pressure, normally below about 0.9. A rising value suggests compensated shock or occult bleeding before the blood pressure falls.

Continuous measurement and waveform display of exhaled carbon dioxide. It confirms tube placement, monitors ventilation quality, and can reflect changes in circulation.

A light-based estimate of hemoglobin oxygen saturation. Poor perfusion, motion, carbon monoxide, and very low saturation make readings unreliable, so results are judged alongside the clinical picture.

Coordinated sedation and paralysis to secure the airway quickly while limiting aspiration risk. It requires preoxygenation, hemodynamic planning, backup devices, and a rescue plan for failure.

Ventilation using roughly 6 mL/kg of predicted body weight tidal volume and limited plateau pressure to reduce ventilator-induced lung injury, particularly in acute respiratory distress syndrome.

Limiting spine movement in suspected unstable injury with a collar, vacuum mattress, or board while balancing airway access and pressure injury risk. Manual stabilization precedes device application.

Stopping major bleeding with direct pressure, tourniquets, hemostatic dressings, or pelvic binding. Uncontrolled hemorrhage is addressed early because it drives shock and cardiac arrest.

Using all available resources, including crew, equipment, and information, through clear communication, assertiveness, workload sharing, and mutual monitoring to prevent and trap errors.

A rule limiting nonessential conversation and tasks during critical flight phases such as taxi, takeoff, approach, and landing so the pilot's attention stays on flying.

An organization-wide framework for identifying hazards, assessing and mitigating risk, and improving safety through reporting, investigation, and feedback.

A model that treats honest error and system failure as learning opportunities while still holding people accountable for reckless conduct, which encourages open reporting of mistakes.

The final decision to accept or decline a flight after weighing patient acuity, weather, aircraft capability, crew fatigue, and other hazards. Any crew member can decline.

The share of total gas pressure contributed by oxygen. It falls as altitude rises and determines whether a patient can maintain adequate saturation in an unpressurized cabin.

A site chosen for helicopter arrival and departure, evaluated for size, surface, slope, obstruction clearance, wind, and safe access, and cleared of debris and bystanders.

The small tail-mounted rotor that counteracts main rotor torque and controls yaw. It is nearly invisible when spinning and is a leading cause of fatal ground injuries.

Downward airflow from turning rotors that can send debris flying, tip vehicles, and knock people down. Crews approach from the side, stay low, and secure loose items.

The calculation confirming the loaded aircraft stays within weight and center-of-gravity limits. Patients, crew, fuel, and equipment all affect performance and controllability.

Fastening stretchers, monitors, pumps, and cylinders so they cannot shift during turbulence or a hard landing, protecting both the patient and life-support function.

Voluntary agreement to a proposed treatment or transport after understandable information about benefits, risks, and alternatives, given by a patient with decision-making capacity.

Declining recommended treatment or transport by a patient with capacity after being informed of the risks. The discussion, capacity assessment, and follow-up instructions are documented.

Federal law requiring a medical screening examination and stabilization for emergency conditions, and setting rules for transfers to hospitals with a higher level of capability.

The duties and interventions a clinician may legally perform, defined by state law, licensure, employer policy, and approved transport protocols.

A structured transfer of information using situation, background, assessment, and recommendation, which keeps handoffs clear and lets the receiver confirm understanding.

Care falling below what a reasonably prudent clinician would provide in similar circumstances that causes harm; proving it requires duty, breach, causation, and damages.