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Air sampling in operating theatres
352
Letters Table i,,,
I.
to the Editor
Sizes of cannulae used (gauge as given by manufacturer)
,u,,,,i,,
.
.
.
.
Manufacturer Gauge
Wallace
Abbot
14 16 17 18 20 21
-7 86 62 -1
--4 231 24 m
Venflon 19 49 145
T h e three photographs supplied by D r Pilsworth of the Abbott, Venflon and Wallace cannulae are similar to our own examples, and still show differences in the surface of the bevel. D r Pilsworth intimates that the different surface is due to silicone b u t we suggest that it is due to the way the bevel is produced in the factory. T h e A b b o t t bevel is made by a heat/melt process in a m o u l d p r o v i d i n g a s m o o t h 'skin', the Venlon is produced by heating and then stretching before cutting. T h e Wallace bevel, as I saw on a visit to the factory in 1982, is produced by milling. D r P i l s w o r t h is correct that articles s h o u l d b e examined before publication a n d this is the function of referees to learned journals. I f it is thought that the findings are unrepresentative it is the task of other workers to r e p e a t the study. W e w o u l d not expect a drug to be introduced without adequate trial and yet there is a morbidity a,0sociated with 'devices' but no r e q u i r e m e n t for trials or licensing o f then L F a c t o r y inspection is not an adequate substitute for final pred,~ct assessment. Health care workers should ask whether this is the best way to deal with hospital equipment.
M . C. K e l s e y
M. G o s l i n g
Dept. of Microbiology, Whittington Hospital, Highgate Hill, London N19 5 N F Barnet General Hospital, Wellhouse Lane, Barnet, Herts E N 5 3Dff
Sir,
Air s a m p l i n g in operating theatres The, W o r k s G r o u p of the D e p a r t m e n t of Health and Social :Security ( D H S S ) has-~receivedl enquiries : aboUt"~ the: b a c t e r i o l o g i c a l : a i r sampling methods contained i n Ventilation of Operating Departments--a DesignGuide issuedlin F e b r u a r y 1983.
Letters t o the Editor
353
T h i s d o c u m e n t was i n t e n d e d to allow engineers to design conventionally ventilated operating rooms : to : t h e requirements o f : a :previous ~DHSS publication-- Ventilation o f Operating T h e a t r e S u i t e s p r e p a r e d : b y a J o i n t W o r k i n g P a r t y (JWP) in J u n e 1982, T h e J W P , W h i c h i n c l u d e d s t a f f o f , t h e D H S S , Medical Research Council a n d N H S was chaired by D r Lidwell. T h e J W P r e p o r t stated: 'Air delivered to the suite b y t h e ventilation system should not contain m o r e than one :colony o f Clostridium~ welchii or of Staphylococcus aureus m -3. T h e choice of ctostridia in this context is n o t that of relevance to infection, but as a marker of bacteria, possibly present in the outside air, which h a v e passed through the filters. T h e r e p o r t a l s o suggested that 'counts during operations can usually be kept below 180 m 3 by an air supply to the operating r o o m of 30-60 mZ/min-~. ' T h e c u r r e n t data sheet incorporated these r e q u i r e m e n t s . However, to s a m p l e : t h e n u m b e r of bacteria in 30 m 3 o f air is time consuming a n d only possible with a high volume sampler, w h i c h may not be readily available. W e t h e r e f o r e suggest that sampling for C1. w e l c h i i or Staph. aureus is replaced b y demonstration of total counts of less than 35 m 3 in the s u p p l y air. T h e design guide was i n t e n d e d for construction o f new operating r o o m s or upgrading of old rooms. N o advice was intended as to routine sampling'of theatre air. T h e J W P report notes t h a t t h i s is n o t needed as long as air supply and airflow specifications are fulfilled. T h e recommendations apply to operating rooms with conventional ventilation; for ultra-clean systems the DHSS is considering recommendations which are likely t o be in line with those of the M R C Committee (White et al., 1983). L. W. M . A r r o w s m i t h
Directorate of Works Operations,
DHSS, 286 Euston. Road, London N W I 3 D N Reference Whyte, W., Lidwell, O. M., Lowbury, E. J. L. & Blowers, R. (1983). Suggested bacteriological standards for air in ultraclean operating rooms. Journal of Hospital Infection 4, 133-139.
Sir, A h i g h i n c i d e n c e o f b l e e d i n g is o b s e r v e d i n a trial to d e t e r m i n e w h e t h e r a d d i t i o n o f m e t r o n i d a z o l e is n e e d e d w i t h l a t a m o x e f for p r o p h y l a x i s i n colorectal surgery
I suggest that M r M o r r i s and his colleagues (1984) have failed to substantiate their~ claim ~t h a t latamoxef ~was ! responsible for : thel ' high incidence :of b l e e d i n g in t h e i r recent: trial.: T h e y l r e c o r d e d the p r o t h r o m b i n time ~in ~16 p a t i e n t s , i n only !one oL whom:: did!it: exceed !itwice the c0ntr01 value. Sevitt::& ~.G a l l a g h e r ( 1 9 5 9 ) r e p o t r e d ' t h e use O f p h e n i n d i 0 n e for the
Letters Table i,,,
I.
to the Editor
Sizes of cannulae used (gauge as given by manufacturer)
,u,,,,i,,
.
.
.
.
Manufacturer Gauge
Wallace
Abbot
14 16 17 18 20 21
-7 86 62 -1
--4 231 24 m
Venflon 19 49 145
T h e three photographs supplied by D r Pilsworth of the Abbott, Venflon and Wallace cannulae are similar to our own examples, and still show differences in the surface of the bevel. D r Pilsworth intimates that the different surface is due to silicone b u t we suggest that it is due to the way the bevel is produced in the factory. T h e A b b o t t bevel is made by a heat/melt process in a m o u l d p r o v i d i n g a s m o o t h 'skin', the Venlon is produced by heating and then stretching before cutting. T h e Wallace bevel, as I saw on a visit to the factory in 1982, is produced by milling. D r P i l s w o r t h is correct that articles s h o u l d b e examined before publication a n d this is the function of referees to learned journals. I f it is thought that the findings are unrepresentative it is the task of other workers to r e p e a t the study. W e w o u l d not expect a drug to be introduced without adequate trial and yet there is a morbidity a,0sociated with 'devices' but no r e q u i r e m e n t for trials or licensing o f then L F a c t o r y inspection is not an adequate substitute for final pred,~ct assessment. Health care workers should ask whether this is the best way to deal with hospital equipment.
M . C. K e l s e y
M. G o s l i n g
Dept. of Microbiology, Whittington Hospital, Highgate Hill, London N19 5 N F Barnet General Hospital, Wellhouse Lane, Barnet, Herts E N 5 3Dff
Sir,
Air s a m p l i n g in operating theatres The, W o r k s G r o u p of the D e p a r t m e n t of Health and Social :Security ( D H S S ) has-~receivedl enquiries : aboUt"~ the: b a c t e r i o l o g i c a l : a i r sampling methods contained i n Ventilation of Operating Departments--a DesignGuide issuedlin F e b r u a r y 1983.
Letters t o the Editor
353
T h i s d o c u m e n t was i n t e n d e d to allow engineers to design conventionally ventilated operating rooms : to : t h e requirements o f : a :previous ~DHSS publication-- Ventilation o f Operating T h e a t r e S u i t e s p r e p a r e d : b y a J o i n t W o r k i n g P a r t y (JWP) in J u n e 1982, T h e J W P , W h i c h i n c l u d e d s t a f f o f , t h e D H S S , Medical Research Council a n d N H S was chaired by D r Lidwell. T h e J W P r e p o r t stated: 'Air delivered to the suite b y t h e ventilation system should not contain m o r e than one :colony o f Clostridium~ welchii or of Staphylococcus aureus m -3. T h e choice of ctostridia in this context is n o t that of relevance to infection, but as a marker of bacteria, possibly present in the outside air, which h a v e passed through the filters. T h e r e p o r t a l s o suggested that 'counts during operations can usually be kept below 180 m 3 by an air supply to the operating r o o m of 30-60 mZ/min-~. ' T h e c u r r e n t data sheet incorporated these r e q u i r e m e n t s . However, to s a m p l e : t h e n u m b e r of bacteria in 30 m 3 o f air is time consuming a n d only possible with a high volume sampler, w h i c h may not be readily available. W e t h e r e f o r e suggest that sampling for C1. w e l c h i i or Staph. aureus is replaced b y demonstration of total counts of less than 35 m 3 in the s u p p l y air. T h e design guide was i n t e n d e d for construction o f new operating r o o m s or upgrading of old rooms. N o advice was intended as to routine sampling'of theatre air. T h e J W P report notes t h a t t h i s is n o t needed as long as air supply and airflow specifications are fulfilled. T h e recommendations apply to operating rooms with conventional ventilation; for ultra-clean systems the DHSS is considering recommendations which are likely t o be in line with those of the M R C Committee (White et al., 1983). L. W. M . A r r o w s m i t h
Directorate of Works Operations,
DHSS, 286 Euston. Road, London N W I 3 D N Reference Whyte, W., Lidwell, O. M., Lowbury, E. J. L. & Blowers, R. (1983). Suggested bacteriological standards for air in ultraclean operating rooms. Journal of Hospital Infection 4, 133-139.
Sir, A h i g h i n c i d e n c e o f b l e e d i n g is o b s e r v e d i n a trial to d e t e r m i n e w h e t h e r a d d i t i o n o f m e t r o n i d a z o l e is n e e d e d w i t h l a t a m o x e f for p r o p h y l a x i s i n colorectal surgery
I suggest that M r M o r r i s and his colleagues (1984) have failed to substantiate their~ claim ~t h a t latamoxef ~was ! responsible for : thel ' high incidence :of b l e e d i n g in t h e i r recent: trial.: T h e y l r e c o r d e d the p r o t h r o m b i n time ~in ~16 p a t i e n t s , i n only !one oL whom:: did!it: exceed !itwice the c0ntr01 value. Sevitt::& ~.G a l l a g h e r ( 1 9 5 9 ) r e p o t r e d ' t h e use O f p h e n i n d i 0 n e for the