292 Correspondence

Securing the endotracheal tube I was interested in Dr T.M. Young’s method of securing the endotracheal tube using a plastic ‘Nosworthy’ connector and a commercially available ‘0’ ring (Anaesthesia, 1976,31,1094) and would like to describe my own, very simple, method.

I have overcome the problems described by Dr

Young by securing the tape to the endotracheal tube with a self locking STA-STRAP* cable tie (as illustrated in Figs 1 & 2). This method allows complete union of the two parts of the plastic

* Panduit Corp., Tinley Park, Illinois, U.S.A.

Fig. 1. Sta-Strap cable ties looped and locked in position.

Fig. 2. Cable tie locked in position; the excess plastic strap has been cut off.

Correspondence 293

connector which is not possible when the ‘0’ ring Securing the endotracheal tube is positioned above the flange of the proximal connector. Incomplete union of the connectors may lead to them falling apart with disastrous conse- quences.

1 wish to thank Mr T. Dee, Medical Illustration Department, Queen Elizabeth Hospital, for pro- ducing the illustrations. Queen Elizabeth Hospital, EDWARD MATHEWS Edgbaston, Birtningham B15 2TH

I was surprised to see a photograph in Anaesthesia which showed an endotracheal tube dragging at the corner of a patient’s mouth. (Anaesthesia, 1976, 31, 1094). This is frequently damaging and I feel that it is especially important for us in this age of technological innovation to exercise with even greater care those skills of patient care which tend to be forgotten in our search for knowledge. Department of Anaesthetics, D.E. JEAL P.O. Box 17039, Congella, 4013 Durban, South Africa

Defective and misused co-axial circuits

Faulty co-axial circuits Dental anaesthesia is a field where pollution

We wish to report a complication of the use of the co-axial Mapleson D pattern of anaesthetic breath- ing circuit manufactured by Penlon Ltd.

After about 3 months of uneventful use of the circuit as part of a pollution control system for dental anaesthesia, we suddenly found that patients having more than the very briefest of procedures were difficult to maintain at a reasonable depth of anaesthesia and were showing evidence of cyanosis. The cause of this only became apparent when a very detailed inspection of the apparatus concerned was undertaken. The rubber sleeve connecting the flexible inner tube to the inner tube of the valve head had torn through so that fresh gas leaked from inner to outer tube. As soon as a gas-tight seal was obtained with the patient most of the fresh gas was passing directly out of the expiratory value and the rest of the circuit was acting as ventilatory dead space. The fault was not visible through the semi- transparent outer tube.

Penlon Ltd have issued a warning notice indicating that some circuits were manufactured using faulty connecting sleeves and the following is a quotation from that notice.

‘It is strongly recommended that a thorough visual inspection be made of all co-axial circuits and spare tube assemblies in service, and in stock. The two alternative inner tube end sleeves may be identified thus:

Extrusion: smooth, seamless appear- ance Unsafe Mouldings: has two exterior, longi- tudinal raised seams gaps and raised lip at tube end. Circular mark at inner end Safe All tube assemblies containing extruded black

inner tube end sleeves should be withdrawn and returned to Penlon Ltd.’

control is particularly difficult to achieve with simple apparatus, and co-axial circuits are very useful. However, they have their own particular problems which have included improper connec- tion’ and both disconnection+ and kinking3 of the inner tube. It is important that when such circuits are in use, the routine anaesthetic machine check should include a close inspection of both the patency and continuity of the inner tube. The semi-trans- parent nature of the outer tubecannot be relied upon to make faults visible. Possibly manufacturers should consider attaching the fresh gas tube along the outside of the larger tube. Edinburgh Dental Hospital, J.A.W. WrmsMrin Chanibers Street, Edinburgh D.J. GRUBB

References

1. PATERSON, J.G. & VANHOOYDONK, V. (1975) A hazard associated with improper connection of the Bain breathing circuit. Canadian Anaesthetists’ Society Journal, 22, 373.

2. HANALLAH, R. & ROSALES, J.K. (1974) A hazard connected with re-use of the Bain’s Circuit: A case report. Canadian Anaesthetists’ Society Journal, 21, 511.

3. MANSELL, W.H. (1976) Bain Circuit: ‘The Hazard of the Hidden Tube’. Canadian Anaesthetists’ Society Journal, 23, 227.

Misuse of co-axial circuits The Bain Circuit and Penlon co-axial circuit are being quite widely used for dental anaesthesia and relative analgesia with continuous flow machines with apparent success.

Under these conditions, a flow of fresh gas of the mixture selected on the flowmeter is delivered to the patient through the small bore inner tube, there being ample pressure available on the continuous