- Email: [email protected]
Ventilation of Operating-theatres
967
LEADING ARTICLES
THE LANCET LONDON
2
MAY
1964
Ventilation of Operating-theatres To provide many of their essential services, hospitals are equipped with complex machinery. Its working is generally beyond the understanding of the medical staff, and when it fails they often get unsatisfactory answers to their inquiries about the cause. Ventilation plants in operating-theatres may fail-sometimes even from the moment of installation-to give satisfactory comfort and satisfactory bacteriological controls. Surgeons have rightly demanded to know the reasons. In Glasgow, the Hospital Engineering Research Unit1 has made a detailed study of ventilation performance in four operating-suites and has sought the reasons for the many faults it discovered. The faults were broadly classified as due to inadequate specification, to failure of the installation to meet the specification, and to poor maintenance. Detailed bacteriological studies are not reported, but observations were made on the two main ventilation features whose effects on bacteriological conditions are known-the volume of air delivered, and the direction of air movement between the rooms. The volumes of air supplied to the suites were 97%, 93%, 91%, and 67% of the specified amounts and those for the individual rooms ranged from 100% to 33%. Some electrical and other maintenance faults were found; but it was clear that, even when first installed, the plants had been incapable of delivering the specified volumes of air. Some of the causes were incorrect calculation of system and plant resistance, ducts not conforming to
design specification, a fan running below design speed because the wrong pulley had been fitted, and a poorly constructed duct damper which worked loose and closed stream. These faults should have been discovered when the plant was commissioned; but the hospital authorities had apparently been satisfied by a verbal assurance from the installing engineers that the plant was working properly, and had made no detailed commissioning tests of their own. The airflow tests were done with clean filters in position; dirty filters caused further reductions of ventilation efficiency. Failure to change filters may sometimes be due to procrastination; but one of the hospital engineers, working to a fixed budget, admitted that he delayed the filter changes for as long as he could because the ventilation plant was fitted with 0-5 [.L filters and the annual cost of changing them was 8% of the installation cost of the whole plant. Yet it is already established that sub-micron filters are unnecessary in surgical ventilation units : BLOWERS and CREW2 found that, despite the average bacterial size of only 1 !1-,
against the air
I
I
I
I
1. Hospital Engineering Research Unit. A study of the performance of the air conditioning plants at three operating theatre suites. Sponsored by the Nuffield Provincial Hospitals Trust and the University of Glasgow. 1963. 2. Blowers, R., Crew, B. J. Hyg., Camb. 1960, 58, 427.
outdoor air after 5 [t filtration contained very few organisms of any sort and no pathogens at all. NOBLE et al.3 have shown the reason for this rather surprising fact: pathogenic bacteria are carried in the air not as naked organisms but embedded in particles ranging from 4 to 20 11- and averaging about 13 11-. Relatively simple filters thus remove all organisms that are able to cause wound sepsis. The Glasgow studies showed that airflow between the rooms of the suites was generally as planned (i.e., from " clean " to " dirty " areas) when doors were closed; but reverse flow occurred freely when doors were left open and when there were many openings not fitted with doors. On the matter of comfort, the staff were generally satisfied; but in two theatres conditions ranged from comfortably warm" to too warm "; one of these had an air refrigeration unit and the other had not. Among the faults contributing to overheating were inadequate airflow, due to blocked filters and the other causes already mentioned, and poorly designed and ill-maintained automatic controls, while in one hospital the ventilation air was drawn not from outdoors but from the very warm plant-room. Better design and maintenance would have given greater comfort in all the suites. Perhaps the most important revelation from this study is that the engineering departments of regional hospital boards neither demanded nor themselves applied detailed commissioning tests for ventilation equipment. The required performance has already been stated 4; what is now needed is a standard code of practice for tests to ensure that this is attained. These tests should be performed and a certificate issued by the installing engineers and perhaps repeated by the engineering staff of regional boards before the equipment is accepted. The Ministry of Health should call on an expert body to devise these tests and then recommend them to regional boards. "
"
The Prison Medical Service FOR some years the Prison Medical Service has been seriously undermanned; this has been especially unfortunate at a time of rapid development in both penal and psychiatric treatment of offenders. Insufficient suitably qualified recruits have been attracted to this small service (62 whole-time and 78 part-time doctors), with slow promotion by seniority, liability to posting to distant institutions, and very limited opportunities for specialist study or secondment. The difficulty in recruitment applies especially to psychiatrists. Because of the greatly increased demand for reporting to the courts and for providing treatment they are needed more than in former years. But young psychiatrists, on the threshold of a specialist career, have not felt inclined to join a service where they will spend much of their time in general medical duties, cut off from colleagues and teaching institutions, when they can expect to reach consultant level far more quickly in the National Health Service. Moreover, prison medical officers are hardpressed and have little opportunity to take part in newer 3. Noble, W. C., Lidwell, O. M., Kingston, D. ibid. 4. Medical Research Council. Lancet, 1962, i, 945.
1963, 61, 385.
LEADING ARTICLES
THE LANCET LONDON
2
MAY
1964
Ventilation of Operating-theatres To provide many of their essential services, hospitals are equipped with complex machinery. Its working is generally beyond the understanding of the medical staff, and when it fails they often get unsatisfactory answers to their inquiries about the cause. Ventilation plants in operating-theatres may fail-sometimes even from the moment of installation-to give satisfactory comfort and satisfactory bacteriological controls. Surgeons have rightly demanded to know the reasons. In Glasgow, the Hospital Engineering Research Unit1 has made a detailed study of ventilation performance in four operating-suites and has sought the reasons for the many faults it discovered. The faults were broadly classified as due to inadequate specification, to failure of the installation to meet the specification, and to poor maintenance. Detailed bacteriological studies are not reported, but observations were made on the two main ventilation features whose effects on bacteriological conditions are known-the volume of air delivered, and the direction of air movement between the rooms. The volumes of air supplied to the suites were 97%, 93%, 91%, and 67% of the specified amounts and those for the individual rooms ranged from 100% to 33%. Some electrical and other maintenance faults were found; but it was clear that, even when first installed, the plants had been incapable of delivering the specified volumes of air. Some of the causes were incorrect calculation of system and plant resistance, ducts not conforming to
design specification, a fan running below design speed because the wrong pulley had been fitted, and a poorly constructed duct damper which worked loose and closed stream. These faults should have been discovered when the plant was commissioned; but the hospital authorities had apparently been satisfied by a verbal assurance from the installing engineers that the plant was working properly, and had made no detailed commissioning tests of their own. The airflow tests were done with clean filters in position; dirty filters caused further reductions of ventilation efficiency. Failure to change filters may sometimes be due to procrastination; but one of the hospital engineers, working to a fixed budget, admitted that he delayed the filter changes for as long as he could because the ventilation plant was fitted with 0-5 [.L filters and the annual cost of changing them was 8% of the installation cost of the whole plant. Yet it is already established that sub-micron filters are unnecessary in surgical ventilation units : BLOWERS and CREW2 found that, despite the average bacterial size of only 1 !1-,
against the air
I
I
I
I
1. Hospital Engineering Research Unit. A study of the performance of the air conditioning plants at three operating theatre suites. Sponsored by the Nuffield Provincial Hospitals Trust and the University of Glasgow. 1963. 2. Blowers, R., Crew, B. J. Hyg., Camb. 1960, 58, 427.
outdoor air after 5 [t filtration contained very few organisms of any sort and no pathogens at all. NOBLE et al.3 have shown the reason for this rather surprising fact: pathogenic bacteria are carried in the air not as naked organisms but embedded in particles ranging from 4 to 20 11- and averaging about 13 11-. Relatively simple filters thus remove all organisms that are able to cause wound sepsis. The Glasgow studies showed that airflow between the rooms of the suites was generally as planned (i.e., from " clean " to " dirty " areas) when doors were closed; but reverse flow occurred freely when doors were left open and when there were many openings not fitted with doors. On the matter of comfort, the staff were generally satisfied; but in two theatres conditions ranged from comfortably warm" to too warm "; one of these had an air refrigeration unit and the other had not. Among the faults contributing to overheating were inadequate airflow, due to blocked filters and the other causes already mentioned, and poorly designed and ill-maintained automatic controls, while in one hospital the ventilation air was drawn not from outdoors but from the very warm plant-room. Better design and maintenance would have given greater comfort in all the suites. Perhaps the most important revelation from this study is that the engineering departments of regional hospital boards neither demanded nor themselves applied detailed commissioning tests for ventilation equipment. The required performance has already been stated 4; what is now needed is a standard code of practice for tests to ensure that this is attained. These tests should be performed and a certificate issued by the installing engineers and perhaps repeated by the engineering staff of regional boards before the equipment is accepted. The Ministry of Health should call on an expert body to devise these tests and then recommend them to regional boards. "
"
The Prison Medical Service FOR some years the Prison Medical Service has been seriously undermanned; this has been especially unfortunate at a time of rapid development in both penal and psychiatric treatment of offenders. Insufficient suitably qualified recruits have been attracted to this small service (62 whole-time and 78 part-time doctors), with slow promotion by seniority, liability to posting to distant institutions, and very limited opportunities for specialist study or secondment. The difficulty in recruitment applies especially to psychiatrists. Because of the greatly increased demand for reporting to the courts and for providing treatment they are needed more than in former years. But young psychiatrists, on the threshold of a specialist career, have not felt inclined to join a service where they will spend much of their time in general medical duties, cut off from colleagues and teaching institutions, when they can expect to reach consultant level far more quickly in the National Health Service. Moreover, prison medical officers are hardpressed and have little opportunity to take part in newer 3. Noble, W. C., Lidwell, O. M., Kingston, D. ibid. 4. Medical Research Council. Lancet, 1962, i, 945.
1963, 61, 385.