All that seems well is not always well—intermittently malfunctioning flexometallic tracheal tubes

Editor—Checking anaesthetic equipment before use helps to prevent equipment-related morbidity and mortality.1 There are recommendations for checking endotracheal tubes (ETTs) before insertion to detect defects such as splitting, holes, cuff leaks and missing sections.2 3 We describe some interesting cases where everything seemed correct on routine preoperative checking as recommended for flexometallic ETTs. However, in some patients the cuff deflated over time, while in other patients the same ETT worked well.

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 22–24 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).



View larger version (79K):
[in this window]
[in a new window]
 
Fig 1 Fine surface cuts on a Portex flexometallic ETT extending over the embedded inflation tube (under magnification).

 


View larger version (117K):
[in this window]
[in a new window]
 
Fig 2 Normal check for cuff patency when Portex flexometallic ETT is flexed with the embedded inflation tube on concave side.

 


View larger version (116K):
[in this window]
[in a new window]
 
Fig 3 Occult air leak revealed (cuff deflated, arrow) when Portex flexometallic ETT is flexed with the embedded inflation tube on convex side (arrow).

 


View larger version (102K):
[in this window]
[in a new window]
 
Fig 4 Occult air leak detected (air bubbles) when the Rusch flexometallic ETT is dipped in water, keeping the embedded inflation tube on its convex side.

 
There are reports of cuff incompetence in ETTs and methods to repair them.4 5 In situations such as craniotomy, when the ETT cuff starts malfunctioning sometime after intubation and after surgery has started, replacement of the defective tube is not feasible. Hence, identification of such an occult leak in such defective ETTs is important before using them. Flexometallic tubes have a metal or nylon spiral-wound reinforcing wire covered internally and externally by rubber, PVC, latex or silicone.2 Overuse and repeated sterilization of reusable spiral embedded tubes can predispose them to problems.2 In this instance, both the flexometallic ETTs revealed defects under magnification 22–24 cm from the patient end. This is usually the site of securing the tube with an adhesive tape or bandage. In the Portex flexometallic ETT, the fine cuts were probably the result of earlier attempts to remove the adhesive tape after extubation using a sharp surgical blade. With the Rusch flexometallic ETT, frequent use of too tight a bandage knot to secure it could explain the unevenness on its surface. This might have led to a breach in integrity of the embedded inflation tube at this level. These cuts/holes autoseal when the ETT is straight or when they are on the concave surface of the ETT. However, when made convex, these defects stretch, allowing air to leak. As flexometallic ETTs are straight without pre-formed curves, there are equal chances of these defects lying on the concave or convex surface once the trachea is intubated. This explains their malfunction only in some patients and despite normal routine checks. A similar occult leak caused by a bitten notch has been reported by Tamakawa and colleagues.6

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.

V. K. Arya, A. Kumar, J. Radhakrishnan and A. K. Durairaju

PGIMER-Chandigarh, India

References

1 Charlton JE. Checklists and patient safety. Anaesthesia 1990; 45: 425–6[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; 557–675

3 American Society for Testing and Materials. Standard specifications for cuffed and uncuffed tubes (ASTM F1242–96). West Conshohocken, PA, USA: ASTM, 1996

4 Verborgh C, Camu F. Management of cuff incompetence in an endotracheal tube. Anesthesiology 1987: 64: 441–2

5 Fisher MM. Repairing pilot balloon lines. Anaesth Intensive Care 1988; 16: 500–1

6 Tamakawa S, Sugawara K, Yanagita Y, Saito Y. Occult air leak of an endotracheal tube. Anesth Analg 1998; 87: 742–8[ISI][Medline]





This Article
Full Text (PDF)
E-Letters: Submit a response to the article
Alert me when this article is cited
Alert me when E-letters are posted
Alert me if a correction is posted
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Add to My Personal Archive
Download to citation manager
Disclaimer
Request Permissions
Google Scholar
Articles by Arya, V. K.
Articles by Durairaju, A. K.
PubMed
PubMed Citation
Articles by Arya, V. K.
Articles by Durairaju, A. K.