Interfacility Transport: Choosing Ground vs Air

Overview

Interfacility transport — moving a patient between hospitals — almost always means transferring to a higher level of care. Three mode options exist: ground ambulance, rotor-wing (helicopter), and fixed-wing (airplane). Each has a different speed profile, weather tolerance, cabin environment, and altitude physiology. Mode selection requires balancing distance, time-criticality, weather, patient acuity, available crew, geography, and cost. There is no single “best” mode — there is the best mode for this patient on this day.

The respiratory therapist’s role in transport preparation spans oxygen supply reconciliation, altitude physiology management, airway and tube security, and ensuring crew scope matches patient acuity before the wheels or rotors turn.

Key Concepts

• Ground ambulance.Most available and lowest cost. Offers the largest working space, no altitude or cabin-pressure physiology, and is the least weather-limited option. The trade-off is speed: ground transport is slowest over distance and subject to traffic. Best suited for short transfers (roughly under 100–150 miles) and for any situation in which weather has grounded aircraft.
• Rotor-wing (helicopter).Fast over short-to-moderate distances (commonly up to ~150 miles), point-to-point without requiring an airport, and capable of reaching scenes inaccessible by road. Strongly limited by weather (visibility minimums, icing, low ceilings), cramped and noisy with high vibration, and weight/space constrained. Rotor-wing cabins are generally unpressurized — cabin altitude tracks terrain, rising with the aircraft. Best for time-critical short and medium transfers when weather permits.
• Fixed-wing (airplane).The right choice for long distances (roughly over 150–250 miles). Pressurized cabin, faster and smoother cruise, and can fly above most weather. The cost is operational complexity: airports are required at both ends, adding ground legs that extend door-to-door time. Even with pressurization, the equivalent cabin altitude typically sits at ~6,000–8,000 ft, meaning gas expansion and hypoxia risk still apply.

Mode Comparison

Assessment & Findings

Before committing to a mode, the transport team must answer four core questions:

1. Can the patient tolerate the door-to-door time? This is not just flight time — it includes preparation, ground legs, and any realistic delays. A 45-minute helicopter flight may represent 2+ hours bed-to-bed.
2. What is the O₂ requirement, and will altitude worsen it? Calculate current flow rate, project total consumption over the entire trip including buffer time, and determine whether the available supply is adequate. Patients with low SpO₂ at sea level will desaturate further at altitude due to the reduced partial pressure of O₂ (lower PiO₂).
3. Might procedures be needed en route? A cramped rotor-wing cabin severely limits the ability to perform chest compressions, intubation, chest tube insertion, or line placement. Anticipate needs and intervene before departure when possible.
4. Does crew scope match patient acuity? Confirm the transport team can manage the patient’s current status and any anticipated deterioration. Scope of practice varies significantly between basic life support (BLS), advanced life support (ALS), and critical care transport (CCT) crews.

RT Priorities & Interventions

• Reconcile oxygen supply for the full trip plus reserve. Calculate flow rate × total trip duration (including ground legs and a realistic delay buffer). Air transport frequently requires liquid oxygen (LOX) or multiple cylinders. Never depart with a supply that only covers the estimated flight time.
• Prepare for altitude physiology on any air transport. Decompress closed gas spaces before departure: ensure a nasogastric tube is vented open and functioning; any pneumothorax must be chest-tubed before flight (not observed conservatively); replace the air in the ETT cuff with saline or actively monitor cuff pressure throughout the flight, as trapped air expands at altitude and can cause mucosal ischemia. Boyle’s Law: at ~8,000 ft equivalent, trapped gas volume increases roughly 30–35%.
• Secure every line and tube before departure. Once airborne or en route, access is limited, lighting may be poor, and turbulence or vibration raises dislodgement risk. Tape, confirm depth, and document all tubes, lines, and drips before the team moves the patient.
• Transition ventilator settings for altitude if applicable. Volume-targeted modes continue to deliver the set tidal volume despite altitude-related changes in gas density; however, SpO₂ and ETCO₂ monitoring targets may need adjustment. Confirm the transport ventilator is calibrated and functioning before departure.

Common Pitfalls

• Choosing air when weather will abort or divert the mission. Requesting rotor-wing transport when marginal weather is forecast leads to mission aborts mid-transfer — sometimes leaving the patient in an intermediate location without the receiving team’s resources. Check current and projected conditions for the entire route.
• Assuming “air is always faster.” For short distances, helicopter launch preparation, flight, landing, and the ground leg to the receiving unit often make total transport time equal to or longer than a direct ground ambulance run. For distances under ~30–50 miles in urban areas, ground is frequently the faster option.
• Underestimating oxygen needs for predictable delays. High-flow patients on 15 L/min consume O₂ rapidly. Add a realistic buffer for weather holds, landing delays, or longer-than-planned ground legs. Running out of O₂ in flight is a critical, preventable emergency.
• Sending a patient with an untreated pneumothorax by air. This is among the most dangerous transport errors. Expansion of trapped gas at altitude can cause rapid tension pneumothorax with cardiovascular collapse. The receiving team will confirm the patient arrived deteriorated — or did not arrive at all.
• Failing to confirm crew scope before accepting the request. A critical care patient dispatched with a BLS crew represents a scope mismatch that cannot be corrected in transit.

Board Exam Pearls

FAQ

Related Resources

Sources

1. Warren J, Fromm RE Jr, Orr RA, Rotello LC, Horst HM; American College of Critical Care Medicine. Guidelines for the inter- and intrahospital transport of critically ill patients. Crit Care Med. 2004;32(1):256-262.
2. Commission on Accreditation of Medical Transport Systems. Accreditation Standards of the Commission on Accreditation of Medical Transport Systems. 11th ed. CAMTS; 2018.
3. Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021. Physics of gas behavior and medical gas therapy chapters.