680

haemodilution improved previously intractable symptoms.Lowering the plasma-fibrinogen in these types of caseswould, however, seem a more logical approach, since itwould leave the haemoglobin concentration unaffected.

This concept of hypernbrinogensmia and hyperviscositybeing one of the factors in myocardial ischxmia will per-haps become more attractive with the current disillusion-ment with the effectiveness of hypolipidaemic drugs,reflected in your leader (March 1, p. 501). As you pointout, it has never been established that lowering an ab-normally high plasma-cholesterol-triglyceride in patientswith established myocardial disease is of any clinical benefit.The occasional benefit reported with the use of " hypo-lipid2emic " drugs in the treatment of angina may wellhave been due to their effect on the abnormally raisedplasma-fibrinogen which is often a coexisting abnormality.This possibility in the case of clofibrate has been suggestedin a recent pilot study again in intermittent claudicants.7It is perhaps unfortunate that in none of the large-scaledouble-blind studies of clofibrate and other hypolipidasmicdrugs has the plasma-fibrinogen and whole-blood viscositybeen measured.

St. James’ Hospital,Sarsfeld Road,

London SW12 8HW. JOHN A. DORMANDY.

TERMINAL FITTINGS FOR MEDICALGAS PIPELINES

SIR,-I was interested to read the letter by Dr Sniper(Feb. 22, p. 457) in which he said that a new BritishStandard terminal unit had been investigated in which theoriginal two-stage locking mechanism was part of thestandard. As I am the chairman of the B.S.I. subcommitteewhich is looking at connectors for medical gas pipelinesystems, perhaps I might be allowed to comment.Dr Sniper is incorrect in that a British Standard terminal

unit for medical gas pipelines has been designated. Thedraft British Standard " connectors for medical gas pipe-line systems " only exists in draft form and is at themoment being redrafted by the editing committee, forconsideration by the complete subcommittee.There is a section in this draft document entitled

" secondary locking " which is that referred to by DrSniper as the two-stage locking mechanism. The draft

only suggests a secondary retaining mechanism may beprovided in the design to operate upon the release of theprimary engagement of the connecting probe. This

secondary locking was originally a requirement of HTM 22,as Dr Sniper has pointed out, but is not a mandatoryfeature of the draft British Standard. We considered this

provision necessary, to allow existing equipment withdirect probes (which otherwise met the proposed standard)to continue in use without expensive modification.The standardisation of connectors for medical gas

pipelines is a subject which is fraught with difficulty. It is

relatively easy to design a new pipeline connector whichwill meet most of the criticisms which have been madeabout existing medical gas pipeline connectors, but it is

very questionable that the introduction of such a standard,which would require complete modification of existingpipelines, would contribute as much to patient safety as ifthe enormous cost of modification of existing pipelineswas put to some other use in patient care. It was for thisreason that the B.S.I. subcommittee have been lookingmore at the process of rationalisation rather than standardi-sation. If a new standard were to be introduced, thenwhenever an existing pipeline was extended or modified itwould be necessary to change all medical pipeline outlets

7. Dormandy, J. A., Gutteridge, J. M. C., Hoare, E., Dormandy, T. L.ibid. 1974, iv, 259.

in that hospital to the new standard and also all the equip-ment probes used to connect apparatus to the pipelines.There are two types of probe: the direct probe and the

remote probe. The direct probe is one in which secondaryequipment, such as flow meters and vacuum bottles, aredirectly coupled to the pipeline using the pipeline connectorto maintain the equipment on the walls. The remote

probe is always attached to a flexible hose and terminatesin equipment sited remotely from the pipeline connector.Direct probes require the use of unnecessarily strengthenedpipeline terminal units to mount such equipment. How-ever, a large number of items of existing equipment aredirectly coupled to the pipeline and for this reason a

secondary locking mechanism is considered necessary,otherwise such equipment may be inadvertently discon-nected from the pipeline and dropped. As an interimmeasure, therefore, we have considered it necessary to makethe secondary locking mechanism as an optional featureof the pipeline terminal unit to safeguard existing direct-probe equipment.

It is hoped that in the not too distant future the directprobe will no longer be in use. The pipeline connectorsystem we have proposed allows the vast majority of

existing pipelines to be used’ with the proposed BritishStandard without any modification other than a clip beingfitted to the wall near the pre-B.S.I. terminal connector,so that flow-meters and vacuum bottles can be fitted to thewall and connected to the pipeline by a short flexiblehose tail. This would mean that there would be no directprobe equipment in use, but such standardisation can bedone slowly as finance permits.We were well aware of the possibility of imperfect

connections when a secondary lock was in place, and thatthis could lead to the emptying of an emergency oxygencylinder on an anaesthetic machine if oxygen were not

flowing to the machine from the pipeline. However, thecost of modification was such that we are proposing

rationalisation of existing pipelines and standardisation offuture installations. We are aware that this is a compromise,but have not found any other method which meets therequirements of increased patient safety and which is

financially feasible. For example, to change the pipelineterminal units to the proposed British Standard in butone block of an existing modern hospital would cost inexcess of E17.000.Department of Anæsthetics,Queen Elizabeth Hospital,Birmingham B15 2TH. JOHN S. ROBINSON.

SYNOVECTOMY

SIR,-I fear that Dr Gumpel and Mr Roles (March 1,p. 488) overstate their case with regard to surgicalsynovectomy when compared with the radioactive-yttriummethod.

The postoperative treatment of our synovectomies overthe past few years has been weight-bearing after forty-eighthours, with encouragement to flex the knee. This islimited to about 40° for the first seven days. Patients arekept in hospital, on average, seven days and come up tooutpatients two. have stitches removed after fourteen days.They receive active physiotherapy from the second day,but rarely any more than routine physiotherapy after afortnight. With this regimen we have never had to manipu-late any postoperative knees. We accept that the operationdoes restrict flexion slightly.

Homœopathic Hospital,Church Road,

Tunbridge Wells,Kent TN1 1JU. I. A. WILLIAMS.