Replacing Mercury

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doi:10.1136/bmj.320.7238.8152000;320;815-816BMJ

Eoin O'Brien

Replacing the mercury sphygmomanometer

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(455 articles)Hypertension(2046 articles)Other Cardiovascular Medicine

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Replacing the mercury sphygmomanometerRequires clinicians to demand better automated devices

When Scipione Riva-Rocci published hispapers on a new sphygmomanometrictechnique in 18961 he could not have

anticipated that his method was to become themainstay of clinical measurement for over a century.Because of this long and fruitful record of service anythreat to the familiar mercury sphygmomanometer ismet with resistancewhich may be interpreted as aris-

ing more from sentimentality than from scientific prin-ciple. But is this fair? May there not be more to theRiva-Rocci/Korotkoff technique than meets the eye?

Clinical sphygmomanometry will change as wemove into the next millennium. Firstly, we will nolonger be allowed to use mercury, and with its passingwill disappear the main argument against introducingthe kilopascal as the unit of measurementnamely,that we measure what we see.Mercurywillno longer bepermitted because it is toxic to the environment, andthe replacement of the millimetre of mercury with thekilopascal, used throughout science as the unit of pres-sure, may be seen as an opportunity to tidy up an irk-some anomaly in scientific nomenclature.2 3

The mercury thermometer has been replaced inmany countries, and in Sweden and the Netherlandsthe use of mercury is no longer permitted inhospitals.4 5 In other European countries, however,including the United Kingdom and Ireland, the moveto ban mercury from hospital use has not beenreceived with enthusiasm because we do not have anaccurate alternative to the mercury sphygmomanom-eter. None the less, the fear of mercury toxicity6 is mak-ing it difficult to get mercury sphygmomanometersserviced, and the precautions recommended fordealing with a mercury spill are influencing purchasingdecisions. Indeed, this is what government policy inmany countries would favourthe gradual disappear-ance of mercury without having to face the

consequence of collecting redundant mercury fromhospitals should a ban become operative.One consequence of this policy is that hospitals

and individual doctors are replacing mercury sphyg-momanometers with unreliable devices, such asaneroid sphygmomanometers, which become inaccu-rate with use and should not therefore be substitutedfor the mercury instrument.7 Most automated deviceshave had a poor record for accuracy,8 though moredevices are now satisfying the stringent criteria of theBritish Hypertension Society9 10 and the Associationfor the Advancement of Medical Instrumentation,11

and more will undoubtedly do so in the future.

The advent of accurate automated devices,howeverwelcome, is not without problems. Firstly, the availableautomated devices were designed for self measure-ment of blood pressure, and it should not be assumedthat they will be suited for clinical use,though some arebeing used successfully in hospital practice and in sev-eral major hypertension studies. Secondly, oscillomet-ric techniques cannot measure blood pressure in all

situations, particularly in patients with arrhythmias,such as rapid atrial fibrillation, but there are also indi-viduals in whom these devices cannot measure bloodpressure for reasons that are not always apparent.Thirdly, doctors are uneasy about trusting algorithmicmethods, zealously guarded by manufacturers. Toensure that new devices conform with recommendedvalidation protocols the mercury sphygmomanometerwill have to be retained as a gold standard indesignated laboratories.

Finally, there is an issue that goes beyond scientificlogic: the Riva-Rocci/Korotkoff technique possessesthat mystique peculiar to the clinical relationship,which is sensed by doctors and nurses and appreciatedby patients. Understandably, therefore, clinicians areunhappy at having to relinquish the Riva-Rocci/Korotkoff technique, which for all its inaccuracies pos-sesses subtle virtues. These include the performance ofan acquired skill, which may be important in establish-ing the rapport from which a successful clinicalrelationship between doctor and patient may develop.Others mourn the sacrifice of yet another clinical skillto the relentless march of technology.

Against all this, the passing of mercury sphyg-momanometers should not in itself be a cause for con-cern. In fact it might be argued that the sooner we ridourselves of an inaccurate technique,1 4 7 on which webase so many important decisions of management, thebetter. Automated devices can remove observer error

and also provide printouts of the measurement withthe date and time of the measurement and digital out-put that can be stored and plotted. Indeed, technologyshould be able to give us the best of both worlds: adevice that allows us to continue using the Riva-Rocci/Korotkoff technique without mercury.

We must prepare therefore for changes in clinicalsphygmomanometry. Several simple measures can betaken immediately. Healthcare providers can phase outmercury sphygmomanometers and replace them withdevices that have been independently validated againstthe relevant protocols. Automated devices should pro-vide blood pressures in both millimetres of mercury

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and kilopascals so that users become familiar with kilo-pascals. Finally, the medical and nursing professions,the clinical market for blood pressure measuringdevices, must ensure that manufacturers provide uswith accurate devices designed to our specifications,rather than accepting, as we have in the past, devices inwhich these considerations are secondary to the com-mercial success of the product.

Eoin OBrien chairmanWorking Party on Blood Pressure Measurement of the Br itishHypertension Society, Beaumont Hospital, PO Box 1297, Dublin 9([email protected] )

Other members of the working party are: Andrew Coats, M deSwiet, WA Littler, Finsa Mee, Paul Padfield, James Petrie.

EOB is a member of the board of AccuSphyg LLC, New York,a company developing an automated device.He has also receivedfunding over the past decade from several blood pressure devicemanufacturers to perform validation studies on automateddevices, the resultsof which have been published in peerreviewedjournals.

1 OBrien E. Ave atque vale: the centenary of clinical sphygmomanometry.Lancet1996;348:1569-70.

2 CENELEC/TC 62. Draft 1st working document prENV XXX Medicalinformatics:expression of the results of measurement in health sciences.CEN/TC251/PT-016. Brussels: European Committee for Standardisation,1994.

3 Council Directive of20 December1979 onthe approximation ofthe lawsof the Member States relating to units of measurement and on the repealof Directive 71/354/EEC. Official Journal of the European Communities1980;L 39:15.2.p 42.

4 OBrien E. Will mercury manometers soon be obsolete? J Human Hyper-tens1995;9:933-4.

5 OBrien E. Will the millimetre of mercury be replaced by the kilopascal?J Hypertens1998;16:259-61.

6 OBrien E, Beevers G, Marshall D.ABC of hypertension. 3rd ed. London:BMJ Books,1995.

7 OBrien E, Beevers G, Marshall D. ABC of hypertension. 3rd ed. London:BMJ Books,1995.

8 OBrien E, Mee F, Atkins N, OMalley K. Inaccuracy of seven popularsphygmomanometers for home-measurement of blood pressure.

J Hypertens1990;8:621-34.9 OBrien E. Automated blood pressure measurement: state of the market

in 1998 and the need for an international validation protocol for bloodpressure measuring devices.Blood Pressure Monit1998;3:205-11.

10 OBrien E, Petrie J, Littler WA, de Swiet M, Padfield PL, Altman D, et al.The British Hypertension Society Protocol for the evaluation of bloodpressure measuring devices.J Hypertens1993;11(suppl 2):S43-63.

11 American National Standard. Electronic or automated sphygmomanometers.Arlington, VA:Association for the Advancemento f Medical Instrumenta-tion,1993.

Heart and heart-lung transplantation in DownssyndromeThe lack of supportive evidence means each case must be carefully assessed

Congenital heart disease is common in Downssyndrome, occurring in about 40% of individu-als.1 Twenty years ago cardiac surgery was

often not attempted in children with Downs syndromebecause of operative mortality of up to 60% and ashort life expectancy.2 With improvements in paediat-ric cardiac surgery and changes in attitude towardschildren with Downs syndrome such children now

undergo corrective cardiac surgery. Some will inevita-bly develop complications and may benefit from hearttransplant. There is also a large group of young adultswith Downs syndrome who did not have heart surgerywhen young and who have uncorrected heart lesionsthat are now inoperable because of irreversible pulmo-nary vascular disease. They too are potential candi-dates for heart-lung transplantation. There is nopublished literature on heart or heart-lung transplan-tation in Downs syndrome, which makes it hard topredict the outcome in these patients.

Heart transplantation is now a widely acceptedtreatment, and medium term survival has steadilyimproved.3 The results of heart-lung transplantation

are not as good but have also improved. Long termoutcome of both is uncertain, with rejection and theside effects of immunosuppressive drugs (malignancyand infection) the major complications.

During a 14 year programme with over 800 trans-plants we have received only one referral for a patientwith Downs syndrome. A questionnaire sent to otherUK transplant centres revealed only two otherreferrals. None of these patients underwent transplan-tation (for reasons other than Downs syndrome).However, the paucity of referrals is surprising given thehigh prevalence of Downs syndrome and associatedcardiac problems. A similar situation has been noted in

paediatric oncology, with a lower than expectednumber of referrals for bone marrow transplant.4

Although few people are consciously prejudiced,parents, referring physicians, and transplant centresmay all worry that that a transplant will be too muchfor someone with Downs syndrome or that the patientwill be difficult to manage. Coexisting medicalproblems are common and may be contraindicationsto transplantation. There is also concern over infectiveand malignant complications. Although no publishedwork addresses the r isks of heart transplant in Downssyndrome, some information can be drawn from litera-ture about the immune system, bone marrow, andrenal transplants in this population.

Well documented immunological abnormalities inDowns syndrome result in a high incidence ofinfection, autoimmune disease, and malignancy.Impaired chemotaxis, antibody production, phagocy-tosis, and bacteriocidal activity; reduced numbers ofcirculating lymphocytes; and an abnormal thymicstructure are all recognised, although controversyexists on the precise immune defects.5 Immune abnor-

malities lead to an excess of all types of infection, butparticularly to pneumonia (because of physicaldifferences, including smaller airways, enlarged tonsilsand adenoids, and lax muscle).1

Leukaemia is 10-30 times more common inDowns syndrome.Reports on bone marrow transplan-tation describe increased infective complications,higher early mortality after transplantation, and morechemotherapeutic toxicity.6 Both the increased inci-dence of haematological malignancy and the increasedsensitivity to chemotherapeutic agents may be due to adecreased ability to repair genetic damage, which hasbeen shown in vitro.7This has implications for the risk

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