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In regard to the article by Mann et al,1 the issue of endotracheal tube (ETT) cuff inflation in response to reduced barometric pressure at altitude has been recognised for a long time. The most recent study published in 2004 used pressure transducers to examine the effects in vivo.2 The pressure effects of altitude on cuff volume are predicted by Boyle's law, which states that a fixed mass of gas will expand as ambient pressure decreases. If there is no method of venting this expansion, there will be an increase in pressure within any air filled space. Accordingly a number of authorities recommend the use of saline (incompressible) rather than air in ETT cuffs for aeromedical transport of intubated patients.3,4 This avoids the problems of gas expansion and contraction in response to changes in barometric pressure and/or the use of a relatively complex formula for deflation on ascent and re‐inflation on descent.
Competing interests: none