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KEYWORDS Endotracheal tube / Anaesthesia / Pressure / Monitoring / Complications
Tracheal intubation constitutes a routine part of anaesthetic practice both in the operating theatre as well as in the care of critically ill patients. The procedure is estimated to be performed 13-20 million times annually in the United States alone. There has been a recent renewal of interest in the morbidity associated with endotracheal tube cuff overinflation, particularly regarding the rationale and requirement for endotracheal tube cuff monitoring intra-operatively.
This review describes the pathophysiology associated with inflated ET tube cuffs and the complications associated with excessive cuff pressure on the trachéal mucosa. Current practice in the specialties of anaesthesia, emergency medicine and intensive care is described. The review finally describes practical techniques of minimising complications secondary to cuff overinflation and provides 'safe' cuff pressure limits and monitoring recommendations based on best current scientific evidence.
Introduction
The first documented case of endotracheal intubation was described by Hippocrates (460-380 BC). Today endotracheal intubation forms a core skill of anaesthetic practice and training worldwide. Intubation of the trachea with an endotracheal tube (ET tube) is a very common anaesthetic procedure estimated to be performed 13-20 million times annually In the United States alone (Lovett et al 2006).
ET tubes are commonly used to either facilitate positive pressure ventilation (PPV) or to protect a patient's airway from aspiration of gastric contents. The cuff near the distal tip of the ET tube is inflated with air to create an airtight seal to allow PPV and to prevent passage of pharyngeal or gastric contents into the airway. In order to prevent aspiration, the pressure exerted by the cuff onto the wall of the trachea should exceed the sum of the hydrostatic pressure generated by a column of liquid above the cuff and the negative pressure generated during inspiration (Menta & Myat 1984). Two main approaches for creating an adequate seal using an ET tube cuff are recommended: the minimal leak technique (MLT) (Crimlisk et al 1996) and the minimal occlusive volume (MOV) (Crimlisk et al 1996, Guyton et al 1997). MLT is the smallest volume of air in the ET tube cuff that allows for a small air leak of 50-100 ml tidal volume decrease on inspiration (St...