230 Correspondence

tube. The system does not allow any gas leak from the ventilator system.

We use Siemens-Elema Servo ventilators. As aerosol particles may impact on the mesh of the expiratory flow meter and disturb the measurements, we prefer to protect the meter during aerosol therapy by a filter (Drager Bacterial filter, Siemens-Elema 6606 784 E037E) between the expiratory tubings and the ventila- tor pipe.

Department of Anesthesiology, LARS NORDSTROM Unicersity Hospital, GUNNAR MALMKUIST

Sweden

Reference

9 2 2 1 8.5 LUND.

I . NORDSTR~M L. In: Ringqvist I , Svedmyr N, eds. Ohsrruktiu lung-sjukdom-inhalationsterapi. Goteborg: Glaxo Lakeme- del AB, 1975; 12&7.

Leaks and the position of the aerosol inhaler

In their recent letter, Dr John K. Kinnell and Dr Richard C. Johnson (Anaesthesia 1980; 35398) on the above subject described the use of the Portex Survival Connexion and the Conventional Aerosol Inhaler.

The conventional inhaler made by the manufacturers of bronchodilator aerosols has a leak round the canis- ter. This leak is necessary for self-administration. If this apparatus is connected to a ventilator system and aerosol is administered during the inspiratory phase of the cycle, most of the aerosol puffed in will be blown out into the atmosphere. This IS due to the low resistance of the space around the canister compared with that of the bronchial tree, and the situation will be made worse by increased airway resistance during bronchospasm.

Secondly, the aerosol canister should be vertical if a metered dose of aerosol is to be administered. The method describes a horizontal position for the inhaler. In this position only the pressurising gas can be discharged.

Furthermore, the system allows the administration of aerosol only when the patient is intubated. Although the authors claim that there will be very little distur- bance to the laminar flow of gas, the leak will presum- ably create considerable turbulence in the system.

Department of’ Anaesthetics. S.J.P. ARIARAJ Unioersity Hospital of Wales, Cardij’

A reply Thank you for sending us the correspondence regarding our brief article on aerosol bronchodilator therapy. We are glad it has stimulated such interest and comment.

Our intention with the equipment we described was to make possible the administration ofsome bronchodi- lator to the bronchial tree using equipment readily available in any operating area.

The nebuliser can be used in ventilated patients if the point in the cycle is suitably chosen. Leakage occurring round the side of the canister can be minimised by inserting a plastic foam disc in the base. Further air-tightness can be achieved, ifdesired, by fixing a latex finger stall over the canister holder.

The nebuliser can always be used in the vertical position by the simple expedient of turning the patient’s head to the side. This was well known in earlier days when using a Clover’s Inhaler (Probyn-Williams, 1909). Furthermore, it can be used in spontaneously breathing patients by inserting the silicone rubber muff into the orifice of a face mask.

We have used the equipment without difficulty on a number of patients and have found it simple and effective.

Department of Anaesthetics. J.D. KINNELL York District Hospital, R.C. JOHNSON Wiggiqton Road, York YO3 7HE

Reference I . PROBYN-WILLIAMS RJ. A Practical Guide to the Administ-

ration of Anaesthetics, 2nd ed. Edinburgh: Longman. 1909: 131.

What i s it and how does it work?

The apparatus illustrated in Figure 1 was recently disco- vered in our Department of Anaesthetics. It consists of two glass bottles each of 200-ml capacity and graduated 0-16 drachms. Each bottle screws into a metal top through which the afferent and efferent tubes pass and

the tops are connected by a bar marked ‘Coxeter Lon- don’. A hook is fitted through a hole drilled in the bar. A modern hand-bellows unit is fitted but there are no signs of modification or repair.

Within the bottles the arrangement of the tubes can

Correspondence 23 1

Fig. 1.

be seen. By virtue of the two long tubes being intercon- nected, it is apparent that any fluid in the upstream bottle would be forced into the downstream bottle before vaporisation could occur. If the flows were reversed then the same would still obtain.

There are certain similarities between this apparatus and a Junker’s inhaler,’ including the hook to allow it to hang from a lapel, and the fact that the bottles are graduated in drachms suggests that chloroform was the agent used. If it is a modification of a Junker inhaler what is the purpose of interconnection of the two long tubes?

Enquiry amongst the more senior members of the Department has been fruitless. Can anyone help?

Rotherham District General Hospital. A . M . DIXON Rotherham, S.J. MATHER South Yorkshire

Reference

1. Tnoum, KB. The development of anaesthetic apparatus. A history based on the Charles King Collection of the Associa- tion of Anaesthetists of Great Britain and Ireland. Oxford: Blackwell Scientific Publications, 1975:68-77.

O’Dwyer’s Tubes

I was able to identify the instruments in Fig. 3 of your Quiz Questions (Anaesfhesia 1980; 35929-30, as O’Dwyer’s tubes for blind intubation of the larynx.

During the winter of 1939, as a medical student in Chicago, I saw my teacher, Dr Archibald Hoyne, remove these tubes from several ambulatory children convalescing from the laryngeal form of diphtheria (membranous croup) and then immediately reinsert them just to show how easy it was ! I am sure that he

used only one instrument for removal and insertion, and I believe it was the extractor. He faced the child and his left index finger was placed over the tongue, while his right hand used the instrument.

Dept of Anaesthesia, Lister Hospital, St evenage, Herts SGI 4 A B

A.R. RYAN

Use of an epidural cannula for a difficult intubation

The use of epidural cannulae for guide for endotracheal intubation in difficult cases is well documented.’ We wish to report a different use of an epidural catheter. This was for a difficult intubation during planned sub-

stitution of a nasotracheal for an orotracheal tube in the immediate postoperative period following the repair of a ventricular septa1 defect in a 3.6 kg, 3-month-old female patient. After removal of the orotracheal tube