Every now and again, an issue comes along that starts as a ripple, but can then lead to significant confusion and consternation in the air ambulance industry. Such an event happened recently when statements were published in several journals and websites to the effect that piston-powered unpressurised (PPUnp) aircraft are not suitable for even the simplest of patient transfers. There is a danger that such generic statements ignore some organisations with different operating conditions, and therefore it is important to look at these assertions from another perspective in order to test their validity.
It has been reported that the medical care provided for patients, and, indeed, their comfort, are compromised in PPUnp aircraft. However, although it may seem intuitive that patient comfort may well be less than ideal due to the flight conditions imposed by the necessary lower cruise altitude, where is the evidence that provision of care is compromised? A literature search doesn’t produce any papers that scientifically demonstrate detriment caused by compromised medical care during transport in unpressurised fixed-wing aircraft. Clearly, all helicopters are unpressurised, and nobody is suggesting that they can’t be used for patient transfers.
unpressurised aircraft are ideal for small hops during which there is little time to climb to high altitude
Undoubtedly, unpressurised aircraft are often noisier and may be subject to turbulence at lower levels. There may be a higher likelihood of route restrictions due to weather or terrain, and the patient’s oxygen status will require closer monitoring. However, on the plus side, such aircraft need much less runway for take-off and landing, can be flown from unpaved surfaces, and are ideal for small hops during which there is little time to climb to high altitude.
It’s worth remembering that the conventional range of cabin altitude equivalents in pressurised aircraft sits between 5,000 and 8,000 ft (1,500 and 2,500 m) – the cruising altitude of most unpressurised aircraft unless terrain dictates otherwise. Hence, on short flights, the use of a pressurised aircraft offers no cabin altitude advantage. Furthermore, in the unfortunate event of a rapid decompression at a cruising altitude of 45,000 ft (13,700 m) – where pressurised aircraft might benefit from reduced fuel costs and higher speeds – the time of useful consciousness is no more than 15 seconds. This is a significant risk to the aeromedical crew as well as the patient, who are likely to become unconscious rapidly as the only way to receive adequate oxygen above 40,000 ft (12,200 m) is to breathe 100-per-cent oxygen via positive pressure apparatus. Once unconscious, all onboard are dependent on the survival of the aircrew and their ability to descend the aircraft rapidly to 10,000 ft (3,050 m). At least the occupants of an unpressurised aircraft will never be exposed to the risks of a rapid decompression.
when budgets are tight, the only choice might be unpressurised
PPUnp aircraft certainly cost less to both lease and purchase, and also to operate over short distances. Although cost should never be the predominant factor in deciding on the mode of patient transport, when budgets are tight, the only choice might be unpressurised – take it or leave it. It goes without saying that if better care can be given in the air than is found on the ground, then there is no absolute contraindication to aeromedical transport. Similarly, in time-critical transfers, a transfer in a PPUnp aircraft is eminently superior to leaving the patient where he or she is, when the treatment needed is in a distant place.
In conclusion, PPUnp aircraft do have a role to play in certain types of aeromedical missions and there are many operators around the world who are still using them. Antagonists of PPUnp aircraft support their point of view by quoting European Aeromedical Institute (EURAMI) standards, although these are not freely accessible and it is unclear whether the evidence for this assertion has been published. On the other hand, the Commission on Accreditation of Medical Transport Systems (CAMTS) has recently published the eighth edition of its accreditation standards, which state: “Any in-service aircraft/ambulance should be configured in such a way that the medical transport personnel can provide patient care consistent with the mission statement and scope of care of the medical transport service. Patient care issues are considered when choosing the aircraft or ground transport.” This is simple and plain common sense and does not rule out the use of PPUnp aircraft as long as patient care issues are met.
In general, it is impossible to argue with the statement that pressurised aircraft are more suitable for patient transfers, and CAMTS even states that ‘pressurised aircraft with air conditioning are strongly preferred for medical transports’. However, the Commission’s rider that ‘a physician familiar with altitude physiology should be consulted or written policies address [sic] altitude limits for specific disease processes of the patient to be transported in an unpressurised cabin’ seems like a very reasonable compromise for those organisations that have no option but to continue with PPUnp missions.
Another argument against the use of PPUnp aircraft in England comes from those who extrapolate Care Quality Commission (CQC) standards of safety and quality based on terrestrial systems. Furthermore, some have stated that it is a legal requirement for all England-based air ambulance operators to register with the CQC. The purpose of the Care Quality Commission is to ensure that minimum standards of quality and safety are applied to all healthcare providers where the point of care is in England. It has no jurisdiction outside the boundaries of England (not even in the Channel Islands and Isle of Man) and is poorly framed to apply to the fixed-wing aeromedical industry. Although helicopter emergency medical services are covered, exemptions for travel insurance and military medevac puts much of the industry outside of the regulatory framework. I posed a simple question to the CQC: “If an overseas air ambulance provider delivers a patient to England and takes the patient to an English hospital, must the organisation register with the CQC?” The answer was a clear and resounding ‘no’. The next question was similar: “If an English air ambulance provider does the same, must it register with the CQC?” This time the answer was a very clear ‘yes’. Since the point of care is the same in both cases, I probed further and asked if a patient were collected from, or transferred to, the Channel Islands (which are British Crown Dependencies and therefore not part of England), would that require registration? This proved too difficult for the CQC spokesman and my questions were referred to an ‘expert’, who has yet to produce a ruling on the ‘legal requirement’ issue.
English operators must continue to use best evidence as it fits their individual mission statement
There is no doubt that registration and accreditation from some form of quality assurance authority with recognised and valid standards is an essential step in the development of an air ambulance organisation, but until the law in England is clarified, and it is placed in line with international standards, then English operators must continue to use best evidence as it fits their individual mission statement(s) and continue the quest for best quality care.
Readers interested in an overview of cabin pressurisation and the relevant physiology are referred to the very first edition of Waypoint AirMed & Rescue (Ask the Experts 1), January 2008.
An overview of accreditation (‘The stamp of approval’) was published in the ITIJ Review – Air Ambulance; April 2012.
Dr Terry Martin is a former RAF doctor and helicopter pilot with a broad background in anaesthetics, ICU, emergency medicine, general practice, and aviation medicine. He is a consultant intensivist and anaesthetist in the UK and directs the CCAT suite of aeromedical training courses in England and in other centres around the world. He is also medical director for Capital Air Ambulance and is on the board of directors of AMREF Flying Doctors.
Conflict of interest
Terry Martin is medical director of Capital Air Ambulance, which operates both pressurised and unpressurised aircraft in appropriate settings.