Untitled Document

Surgery

The place of hyperbaric oxygen in the treatment of patients is still largely an open question and particularly in regard to apnoea neonatorum. The only series published in this country certainly showed favourable results¹. Despite the many critics of this method, it seemed worthwhile to try to construct a relatively simple chamber at a cost sufficiently low to make it generally available. The prototype chamber to be described was constructed with the support of the North Middlesex Hospital, where it has been installed.

SPECIFICATION

The chamber is made of mild steel 5/16" thick (figures 1 and 2). Inside it measures two feet in length and one foot in diameter. Round it is a narrow jacket for circulating hot water but we have not found it necessary to use this so far.

Two six-inch windows of special-strength glass allow illumination and inspection. Along the top of the chamber are sockets for pressure-gauge, oxygen inlet, two openings to the water jacket and a Bailey safety-valve 4" in internal diameter set to 351b/sq.in above atmospheric pressure. At the side is a tap allowing outflow of oxygen from the chamber through a flowmeter. At the lowest part of the hot-water jacket is an inflow pipe.

The chamber is closed by a heavy door sealed by a set-in rubber gasket and secured by four hand-wheels. Inside the chamber is a simple rectangle of steel rod across which is slung a removable cloth hammock. The inflow from the oxygen cylinder is controlled by an ordinary welder's two-stage oxygen regulator which can be set to any desired pressure between 0 and 30lb/sq.in. (just over three atmospheres absolute). Inside the chamber the oxygen stream is broken up by a baffle. The outflow tap on the side of the chamber can be set to a rate of flow which can be measured up to ten litres per minute, but can exceed this rate several times. The flow rate is constant at any given pressure and alters little as the internal pressure is changed. The chamber is mounted on a laminex topped table. By good luck it is situated in a room the temperature of which is kept at 85 to 90°F by nearby central heating pipes.

The shell of the chamber complete with port-holes and door was supplied by Messrs Fraser and Fraser of Bromley at a cost of £117. The reducing valve and associated apparatus including the pressure gauge cost a further £11. It is difficult to assess the value of other ancilliary equipment because much of it was made in the Hospital or adapted from surplus equipment already available but the overall cost of material can not have exceeded £140 excluding labour. Testing and insurance against explosion risks amounted to a further £10.

METHOD OF USE

In use the chamber is first flushed out with oxygen. The rate of compression and decompression is controlled by frequent small manual adjustments of the pressure valve. Similarly, the flow rate of oxygen through the chamber is controlled by the tap on the side.

Safety precautions are important. A pressure vessel of this kind must fulfil accepted standards of design and construction and then undergo pressure tests. All these are supervised by the insuring company. When oxygen is used, naked flames including cigarettes are prohibited nearby. Mineral oils must be removed scrupulously and replaced by special non-combustible lubricants. Highly inflammable fabrics are not allowed in the chamber. The working team should be familiar with the complications of the hyperbaric environment such as decompression illness, as well as being masters of the clinical problem under treatment.

Monitoring

The infants have been monitored by observation of respiration and apex-beat from outside the chamber. More elaborate monitoring, including electrocardiography, could, however, easily be installed by leading wires through porcelain or other pressure resisting plugs.

CLINICAL NOTES

The chamber is installed a few yards away from the labour ward, where more than 3,000 babies are born each year. Initially, the aim has been to place in the chamber only those neonates obviously dying despite accepted methods of resuscitation.

The first infant placed in the chamber was one dying from respiratory distress syndrome some hours after birth. Compression in the chamber, in oxygen, to 151b/sq.in. had no effect. A further increase in pressure to 301b/sq.in. was followed after 5 minutes by a quickening of respiration, from one to eight spontaneous breaths per minute and a very definite change from cyanosis to a pink colour. The baby was removed from the chamber in this improved condition after 40 minutes, but died two hours later after reverting to its previous state.

The next case was of a second twin apparently stillborn. Ten minutes after intubation with IPPR, cardiac massage and administration of adrenaline and vandid. a heart beat was restored, but only occasional respiratory gasps were present when it was placed in the chamber 80 minutes after delivery. Compression to 301b/sq.in. produced no effect and after decompression some blood-stained frothy secretions were aspirated from the trachea with some improvement in its colour. It died at three hours and post-mortem showed bilateral pulmonary atelectasis.

The third baby was born as an assisted breech delivery weighing 31b and in very poor condition, its facies being compatible with oligohydramnios. Ninety minutes after resuscitation was begun the baby had a heart rate of 10 to 20 per minute, and breathed only once or twice a minute. When the baby was placed in the chamber and compressed to 151b/sq.in its respirations increased almost immediately to 32 per minute, while the apex beat counted through the window rose to between 80 and 90. For the first time the baby became pink and started to move its limbs. When decompressed after 40 minutes its condition gradually declined and responded only temporarily to recompression, dying seven hours after birth.

These abbreviated notes are not intended as clinical summaries, but it is hoped that it will be possible to present an account of experience in treating infants with the chamber at a later date.

SUMMARY

A simple hyperbaric oxygen chamber for the treatment of asphyxia neonatorum has been constructed and put into clinical use at a cost of under £150.

Acknowledgements

Among the many helpers in this project I must thank especially the manufacturers, Messrs Fraser and Fraser of Bromley, The National Boiler and General Insurance Company, Mr George Hardes, AMIWE, of the Halesmere Garage and Mr. J. G. Rouse of BIG Ltd. The costs were met by the research funds of the North Middlesex Hospital and I am grateful to my colleagues and seniors there who supported this work.

References

HUTCHISON, J. IL, KERR, M. M., WILLIAMS, K. G. and HOPKINSON, W.I. (1963). Lancet, ii. 1019

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FIGURE 1 A hyperbaric oxygen chamber for new born infants

FIGURE 2

[with G.B. Gillies] A hyperbaric chamber for newborn infants, Anaesthesia, 20, 351-5. 1965

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This seemed like a good idea at the time. I had read about the new idea of high pressure oxygen for treating patients. The obstetric department at the North Middlesex Hospital, a very busy one, was round the corner from the children's ward where I saw patients every working day.

I somehow heard of "asphyxia neonatorum", the same condition that killed the new-born son of President John Kennedy, where a thick mucus membrane prevented oxygen getting through the lungs to the bloodstream. It seemed an obvious opportunity for doing good.

I persuaded the hospital to private funds (Fifty pounds sterling, from memory) and got a patient who happened to be a welder to put the chamber together.

It worked wonderfully well - blue babies turned pink - but what I and others didn't think of was the problem of getting rid of carbon dioxide from the baby's blood-stream. One way of treating this problem could have been infusion of sodium bicarbonate, but no one thought of this at the time.

However the project had some benefits. It introduced me to practical engineering, the realities and problems of invention, and the new field of hyperbaric medicine, which was useful in later years for patients of mine with gas gangrene.

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