Endotracheal tube and laryngeal mask airway cuff volume changes with altitude: a rule of thumb for aeromedical transport.

Full Abstract

BACKGROUND:
Helicopters and light (unpressurised) aircraft are used increasingly for the transport of ventilated patients. Most of these patients are ventilated through endotracheal tubes (ETTs), others through laryngeal mask airways (LMAs). The cuffs of both ETTs and LMAs inflate with increases in altitude as barometric pressure decreases (30 mbar/1000 feet). Tracheal mucosa perfusion becomes compromised at a pressure of approximately 30 cm H2O; critical perfusion pressure is 50 cm H2O.

METHODS:
The change in dimensions of the inflated cuffs of a size 8 ETT and a size 5 LMA were measured with digital callipers at 1000 feet intervals in the unpressurised cabin of an Agusta 109 helicopter used by the Warwickshire and Northamptonshire Air Ambulance.

RESULTS:
A linear expansion in cuff dimensions as a function of altitude increase was identified. For ETTs, a formula for removal of air from the cuff with increasing altitude was calculated and is recommended for use in aeromedical transfers. This is 1/17x1.1 = 0.06 ml/1000 foot ascent/ml initial cuff inflation.

CONCLUSION:
The data for LMA cuff expansion failed to show significant correlation with altitude change. Further work is required to determine a similar rule of thumb for LMA cuff deflation.

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Author information

Author/s: Mann, Catherine (C); Parkinson, Neil (N); Bleetman, Anthony (A);

Affiliation: University of Birmingham, Birmingham, UK.

Journal and publication information

Publication Type: Journal Article

Journal: Emergency medicine journal : EMJ (Emerg Med J), published in England. (Language: eng)

Reference: 2007-Mar; vol 24 (issue 3) : pp 165-7

Dates: Created 2007/03/12; Completed 2007/06/05; Revised 2007/11/02;

PMID: 17351218, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

Comments and Corrections

CommentIn: Emerg Med J. 2007 Aug;24(8):605. (PMID: 17652705)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Humans
Intubation, Intratracheal - instrumentation
Laryngeal Masks
Models, Biological

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