What does "sea level flight" actually mean?
The air pressure at the usual cruising altitude of a commercial or air ambulance aircraft (about 35,000 to 45,000 feet) is so low that a human being could only survive this environment for more than a few seconds. For this reason, aircraft have a "pressurised cabin" that provides the passenger with an air pressure equivalent to being on top of a mountain about 6,500ft / approx. 2,000 metres high.
However, even this cabin pressure - which is much higher than the outside air - affects the oxygen supply and influences the expansion of gases in the human body. For this reason, ambulance flights for certain clinical pictures are carried out in such a way that the pressure in the aircraft cabin almost corresponds to the air pressure at sea level ("sea level") and the effects of the flight on the human body are kept as low as possible.
For the execution of the flight, this means that the cruising altitude must be chosen lower than usual (approx. 28,000 ft), as the pressurised cabin of an aircraft only allows a maximum difference between internal and external air pressure.
For which patients or diagnoses do sea level flights make sense?
A decrease in air pressure leads to various physical changes in the human body. Particularly important is that gases expand under reduced ambient pressure and, where gases cannot escape, exert pressure on the surrounding tissue or organs. In healthy people, pressure equalisation takes place via various connections, for example between the throat and the inner ear. In traumatised patients, however, we often find air trapped in body regions due to an accident or also due to medical measures, which would not be found in healthy patients.
Escape of the air by natural means is then often not possible, for example in the head, in the eye or in the intestines. Typical examples are patients with air pockets in the skull or chest (pneumothorax). If this air expands and cannot escape to the outside, catastrophic consequences can occur, which must be avoided through careful planning and precise diagnosis. In addition, reduced atmospheric pressure reduces the oxygen available to the human body. In particular, patients who already need to be ventilated with 100% oxygen before the flight, would run into a dangerous oxygen deficiency at low atmospheric pressure. For these patient groups, flights with cabin pressure close to “sea level” are important to maintain an adequate oxygen supply.
What are the advantages and disadvantages of sea level flights?
If we conclude that a transport is only possible safely under "sea level" conditions to ensure sufficient oxygen supply or to minimise the risk of compression of tissue or organs by expanding air, we plan the flight accordingly. The lower altitude reduces the cruising speed, increases fuel consumption and often leads to additional stopovers for refuelling.
There are therefore also higher costs. The effects of the weather are also often more noticeable at lower altitudes. On any flight, it is ultimately a joint team decision between the flying and medical crew to determine the safest and most gentle flight procedure for the patient. Patient safety is always the first priority in such decisions.
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