A 41-yr-old male ASA II patient scheduled for posterior cranial fossa tumour surgery in the prone position was intubated with a 38FG sterilized Portex flexometallic ETT. Before insertion, a routine check3 as recommended for cuff and pilot balloon integrity, found the tube safe for use. However, about 30 min after intubation and before the patient could be turned prone, a cuff leak was detected. It persisted despite reinflation and required reintubation with a different flexometallic ETT. Repeat in vitro checks for cuff patency in this defective ETT did not reveal any leak. After a couple of days, the same ETT was used successfully for 6 h in a patient undergoing aneurysm-clipping surgery after a routine check for cuff patency. This ETT, however, when used after sterilization for the third time, demonstrated a cuff leak in vivo despite a preintubation check. A similar problem was also encountered with a different brand, size 36FG flexometallic ETT (Rusch, Germany). The cuff of this ETT was also found to deflate in some patients after intubation, despite a normal check for cuff patency in vitro, while in other cases it worked well.
To find the cause of this intriguing problem, we inspected these two ETTs for structural defects using a magnifying glass. The Portex flexometallic ETT showed fine surface cuts extending over the embedded inflation tube, at about 2224 cm from the patient end (Fig. 1). These cuts became more prominent and gaped when the side of the tube on which they were present was made convex. They disappeared upon flexing the tube in the opposite direction. The ETT cuff was then inflated and the tube was flexed in different directions. This revealed deflation of the cuff only when the embedded inflation tube was on the convex side of it (Figs 2 and 3). The Rusch flexometallic ETT was largely normal except for a slight unevenness on its surface near the 22 cm mark. This tube was subsequently checked under water by flexing it in different directions. This demonstrated a leak of air occurring from the site of unevenness when the embedded inflation tube was on the convex side of the flexed tube (Fig. 4).
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In conclusion, flexometallic ETTs should not be reused. If repeat use is inevitable for economic reasons, it is essential that a cuff leak should be checked for by flexing the tube in different directions, and especially by keeping the embedded cuff inflation tube on its convex surface to reveal occult leaks.
PGIMER-Chandigarh, India
References
1 Charlton JE. Checklists and patient safety. Anaesthesia 1990; 45: 4256[ISI][Medline]
2 Dorsch JA, Dorsch SE. Tracheal tubes. In: Dorsch JA, Dorsch SE, eds. Understanding Anaesthesia Equipment, 3rd Edn. Williams & Wilkins: Pennsylvania, USA, 1999; 557675
3 American Society for Testing and Materials. Standard specifications for cuffed and uncuffed tubes (ASTM F124296). West Conshohocken, PA, USA: ASTM, 1996
4 Verborgh C, Camu F. Management of cuff incompetence in an endotracheal tube. Anesthesiology 1987: 64: 4412
5 Fisher MM. Repairing pilot balloon lines. Anaesth Intensive Care 1988; 16: 5001
6 Tamakawa S, Sugawara K, Yanagita Y, Saito Y. Occult air leak of an endotracheal tube. Anesth Analg 1998; 87: 7428[ISI][Medline]