Canad. Med. Ass. J.July 2, 1966, vol. 95 LETTERS TO THE JOURNAL 35

phe does occur, a prearranged plan must be put intoaction for the immediate procurement and administra-tion of massive blood transfusion. (5) Laparotomymust be performed immediately regardless of the vitalsigns. (6) If the condition of the patient is grave,surgery may be temporarily halted after bilateral clamp-ing of the infundibulo-pelvic ligaments and the uterinevessels, or the clamping of the edges of the uterinelaceration. Massive blood transfusion is carried outthrough several portals until the blood pressure andother vital signs improve. This improvement occursrapidly once the bleeding has been controlled; surgerycan then be completed.

Editorial Subcommittee of theCommittee on Maternal Welfare,The Canadian Medical Association.

To the Editor:In the Discussion of the article on cephalopelvic

disproportion in the issue of May 21 (Canad. Med. Ass.J., 94: 1126, 1966), I read the following statement:

"The rupture of a classical Cesarean section scarseldom occurs during labour but characteristically takesplace in the seventh or eighth month of pregnancywhen the uterus is accommodating itself to the rapidlygrowing fetus."

I have been practising for 30 years and never heardthis before. I have agonized over whether to deliverpatients per vaginam after previous Cesarean sectionsand heard arguments for and against it. In the absenceof other indications there was always the thought thatone was exposing the patient to the unnecessary risk ofrupture of the previous scar.The statement quoted would indicate that this dan-

ger was very slight and would not need to be con-sidered unless the uterus was known to be infectedat the time of the previous surgery.

I would appreciate some discussion on this problem.R. HAYWARD, M.D.

Box 48,Little Current, Ont.

To the Editor:In reply to Dr. R. Hayward's query, the statement

was made that in the majority of women, scars ofprevious classical Cesarean section rupture before theonset of labour, because the Editorial Subcommitteeof the Committee on Maternal Welfare of the C.M.A.believe that this fact is not generally appreciated byall physicians giving obstetrical care. Some authoritiescontend that, regardless of the type of previous Cesar-ean section, the dictum "once a section, always asection" should be followed, while others teach thata repeat Cesarean section is not necessary in themanagement of non-recurring obstetrical complicationif the fetal head is well engaged at the onset of labour,if there is no disproportion, if labour is progressingnormally, and if good facilities are available for theimmediate care of a patient with rupture of the uterinescar. Such facilities include blood for immediate massivetransfusion and the immediate availability of adequatepersonnel and facilities for the anesthesia andlaparotomy.

Editorial Subcommittee of the Committeeon Maternal Welfare, C.M.A.

THE PHYSICIAN AND THE ENGINEERTo the Editor:

Dr. Driessen in his letter (Canad. Med. Ass. J., 94:918 [April 23], 1966) discussing an editorial has drawnattention to an area of great importance.The engineering profession is becoming increasingly

aware that equipment and systems to be used by manmust be designed for man. This need was showndramatically during the last war. At the Institute ofBio-Medical Electronics, University of Toronto, wehave been teaching a course on Human FactorsEngineering to postgraduate engineering students inco-operation with the Department of Industrial Engi-neering, and a course has also been given for severalyears at the University of Waterloo to final-year engi-neering students.

The medical profession has been far slower torealize the medical importance of designing equip-ment and systems so that men are not pushed beyondtheir physiological and psychological limits. Improperdesign is a cause of both mortality and morbidity andis a proper area of investigation for preventive andindustrial medicine. Yet with certain notable excep-tions, few industrial physicians have taken any interestin the product of the industry in which they are in-volved, or the machines used to produce the product.They regard their responsibilities as restricted to thehealth care of the workers.We are moving into an age of more and more com-

plex systems and equipment, whose powers to destroygrow at much the same rate as their powers to benefit.The modern automobile typifies this. Moreover, it is aparadox of modern engineering that, in making lifeeasier for most of us, it lays heavier and heavierburdens on a few of us. It is far easier to travel toVancouver today than it was 50 years ago; but a fewminutes in a busy air traffic control centre, or on theflight deck of an airliner landing in bad weather, aresufficient to show who is carrying the burden. Mensuch as air traffic controllers, airline pilots, surgeonsand others are often asked to solve difficult problems,control very complex equipment and make vital de-cisions in a very short time under considerable en-vironmental and mental pressure.

It is the responsibility of both medicine and engi-neering to ensure that the equipment and systems thatmen have to handle are designed to suit human physio-logical and psychological capabilities. This applies bothto the design of machines within a factory and thedesign of the products of those machines. The etiologyand prevention of a disaster is as much a medicalproblem as the surgical treatment of the victims.In attacking these problems they need the assistanceand perhaps direction of basic sciences, psychology,physiology, and physics. Nevertheless, the fact thatmedicine and engineering are the professions throughwhich scientific knowledge is applied to improve thewell-being of man means that it is these professionsthat are responsible for taking action.The bacteriologist can show the etiology of in-

fectious diseases and how they are spread; the phy-sician is the man who must stop them from spreading.

E. LLEWELLYN THOMAS, M.D., P.Eng.Institute of Bio-Medical Electronics,University of Toronto,Toronto 5, Ont.