Helicopters & Planes
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In this article, Director of Nursing at New Zealand Air Ambulance Service, Angela Coward, discusses helicopters, planes and the special considerations planning aeromedical transfers involves.
There are two main methods of aeromedical transport: planes called “fixed wing” or helicopters referred to as “rotary wing”.
Working in aeromedical retrievals adds a whole extra layer to the work of the medical teams and it helps to understand how aviation operations are organised and regulated. Adding pilots, flight engineers and flight operators to the team requires good interdisciplinary communication and understanding. Patient and flight safety are equally important and only properly integrated medical and aviation teams will deliver the service safely to prevent incidents.
The balance of flight safety versus patient concerns has to be considered… if a flight has to be diverted due to poor visibility this will take priority even if it increases the transfer time and subsequent risk for the patient.
Key Points For Aeromedical Transfers
- Medical and aviation decisions to fly have to be separated
- Unsafe situations have to be identified, stopped and addressed immediately
- Strict adherence to aviation regulations is mandatory and trumps medical SOPs
Plane Or Helicopter?
- Flight time and working time restrictions for the pilots and crew
- Speed of the aircraft
- Runway length required by the aircraft
- Distance covered without refuelling & planning of refuelling stops if needed
- Fuel and staff costs in relation to distance and stopovers
- Noise restrictions
Different types of aircraft used by AMREF, Kenya, differing in range and cabin size
Stretcher transport in economy class occupying 8 seats
Cabin Altitude
- Helicopters used in transfer medicine usually have no option to pressurise the cabin. However, it would be ideal for staff and passengers to maintain the sea level pressure of 101.3kPa (760mmHg) in the cabin.
- The equipment needed to maintain this pressure is heavy, requires a lot of energy and needs a reinforced cabin wall to withstand the large pressure differences between the cabin and the atmosphere.
- In fixed wing planes the cabin pressure is kept between 6000 and 8000ft regardless of the flying altitude. This is significantly lower than the cruising altitude but significantly higher than sea level. It is called cabin altitude.
- The Federal Aviation Administration (FAA) requires all fixed-wing flights to be pressurised at cabin altitudes of no more than 8,000ft at maximum operating altitude.
- Air inside the cabin is compressed and has very low water vapour content, making the circulating air very dry and cool. Due to the low humidity experienced onboard, the use of a heat and moisture exchanger or other means of additional sources of humidification are recommended.
Helicopters
- The mission profile of the service will define the type of helicopter used. Coast guard and SAR (Search And Rescue) services, for example, require aircraft with long range capabilities or good performance in altitude when operating in mountainous areas.
- HEMS helicopters will use helicopters with rapid start and response times, whereas dedicated inter-hospital transfer organisations will prefer models with large cabin capacities and a long range.
- Compared to fixed wing operations, vibrations in helicopters are much more noticeable and can influence the pulse oximeters and cardiac monitor measurements and cause nausea and vomiting in both staff and patients.
Secondary retrieval with the AAKSS HEMS team in the UK
Use of an EC135 for primary HEMS missions and urgent transfers. Example of “Christoph 28” stationed in Fulda, Germany
Helicopter Landing Sites
Example of a hospital helipad with correct marking, illumination, fire control, safety barriers and noise control.
Planning A Retrieval Flight
- is the patient fit for air transfer?
- is a special set up needed for highly contagious diseases?
- how urgent is the transfer & is the staff qualified for this particular mission?
- are the weather and flying conditions suitable for the job?
- is a ground transfer to the aircraft necessary and feasible?
- is additional medical equipment required and will the aircraft tolerate the extra load?
- is a helicopter or plane the preferred option?
The choice of aircraft used for a transfer is therefore dependent on a balance of technical, logistical and clinical factors
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