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A microbiologist's view of commissioning operating theatres
Journal
of Hospital
Infection (1990)
A microbiologist’s
J. Holton,
16, 2934
view
of commissioning theatres
G. L. Ridgway
operating
and A. J. Reynoldson*
Department of Microbiology, University College and Middlesex School of Medicine and *Engineering Services Department, Middlesex Hospital, London WI Accepted for publication
23 February
1990
Summary:
We report our experiences of microbiological testing of operating theatres over a lo-year period. Major faults within the theatres can be detected by microbiological monitoring of air flow direction and the bioload in theatre air. We advocate that there should be a close cooperation between the microbiologist and the hospital engineering department for effective monitoring of theatre commissioning and upgrading. Also we recommend that contract work should be closely supervised particularly with respect to theatre ventilation systems.
Keywords:
Operating
theatres;
commissioning;
aerobiology.
Introduction Operating theatre design in the U.K. is based upon the recommendations of a Medical Research Council report (Medical Research Council, 1962). The underlying theme is one of zoning, with increasing levels of cleanliness centred around the preparation and operating rooms. The rooms are plenum ventilated with approximately 20 changes of air per hour in the preparation and operating rooms and decreasing numbers of air changes in the other rooms and corridors giving an air flow directed outward from the operating or preparation room. Operations such as orthopaedic prosthetic implants, where the consequences of infection may be disastrous, are often performed in ultraclean air theatres which deliver high rates of air flow within a fully- or partially-walled enclosure within the operating room. This area encloses the operating team. Clear evidence has been obtained that using ultraclean air specifically for clean orthopaedic operations can substantially reduce the infection rate (Lidwell et al., 1982). The contribution of airborne organisms to wound infection for other types of operations is unknown. Despite this, Correspondence Grafton Way,
0195-6701/90/050029+06
to: London
Dr
G. L. Ridgway, WClE 6AU.
Department
of Microbiology,
$03.00/O
University
College
0 1990 The Hospital
29
Hospital,
Infection
Society
30
J. Holton
et al.
results with orthopaedic surgery have been extrapolated to suggest that the quality of the air must be maintained within certain limits in all operating theatres and guidelines for these limits have been proposed (DHSS, 1982) and subsequently modified (Arrowsmith, 1985). In an empty operating theatre there should be less than 35 colony forming units (cfu) of bacteria per cubic metre of air, with less than 1 cfu of Clostridium perfringens or Staphylococcus aweus in 30 m 3. During an operation there should be less than 18Ocfu mP3. It has been proposed that ultraclean air theatres have more stringent requirements (Whyte et al., 1983). For example, in a partially walled enclosure with a downward airflow and with the operating team not wearing exhaust body suits, there should be less than 20 cfu me3 at the periphery of the enclosure and less than 10 cfu rnw3 in the centre. In addition to the bioload in the air, the direction of airflow is important and should be from the central ‘clean’ area to the peripheral ‘dirty’ areas. Recommended air flow rates ranging from O-28 to 0.47 m3 s-r across an open door are given to prevent backflow into a relatively ‘cleaner’ area (DHSS, 1983). In an ultraclean air enclosure the airflow should be not less than O-2 m s-i 1 m above the floor (Whyte et al., 1983). It is recommended that microbiological testing of theatres should be performed at commissioning and after any major refurbishment. However, the value of such testing has been questioned (Editorial, 1984). We do not advocate routine microbiological testing of operating theatres other than for ultraclean suites, but have for the last ten years followed a policy of commissioning new and refurbished operating theatres after all works have been completed, but before surgery commences. We report our experiences here. Materials
and
methods
Operating theatres Our central London teaching hospital complex comprises 12 operating suites at nine geographical locations. Eleven of the operating suites are conventionally ventilated and one is an ultraclean air suite containing two theatres. Most were built before 1962 and do not conform to modern architectural practice. Testing Testing of theatres was performed at commissioning and after upgrading, or refurbishment to the ventilation plant or air conditioning system. The ultraclean air suite is tested on a regular basis, and is not the subject of this study. Testing followed the guidelines laid out in DHSS (1983). Before commissioning and testing, the following criteria were required: (i) all building and engineering works were completed; (ii) the ducting had been vacuum cleaned; (iii) the plant had been running at full power for 24 h prior to the test; (iv) there was no other activity in the theatre.
Commissioning
of operating
theatres
31
The theatres were tested by noting the direction of air movement using a smoke test (MSA Vent-Smoke Tubes, Glasgow); checking, where appropriate, the air velocity using a hot wire anemometer (Edra SLV, Airflow Developments Ltd), performing counts of bacteria-carrying particles (BCP) by sampling 30 1 of air using a Cassella slit sampler MK II (Casella, London) and 5% Columbia blood agar plates. The operator was absent from the room during slit sampling. Plates were incubated at 37°C and room temperature for 48 h before being counted. Finally, visual inspection of the fabric of the building was carried out. Occasionally, particle counting using a Status 4000 (Hawksley & Son, Lancing, UK) was performed. A theatre failed a test if any of the following were found: (a) an airflow direction (or velocity) not conforming to the recommendations of DHSS (1983); (b) counts of bacteria-carrying particles greater than 3.5 cfu m-3 in an empty conventionally ventilated theatre; > 18Ocfu mW3 at a post-commissioning check; we did not look for Clostridium perfr-ingens; (c) unacceptable defects of fabric, e.g. peeling plaster, exposed pipework, or damaged flooring. Results
The results cover the period 1978-l 988 and the theatres were tested on over 60 occasions and failed on 24. Most testing followed engineering works to the existing ventilation system rather than commissioning of new plant. The reasons for failure fell into three categories. (1) Theatres failed because the air flow direction was incorrect, and this necessitated adjusting the ventilation balance before a successful test was achieved. The counts of BCP were within the recommended limits. (2) Although the direction of the airflow was correct the counts of BCP were in excess of the recommended limits. In a few instances this was corrected after the theatre had received a thorough second cleaning, removing high level dust missed on the first occasion. On some occasions replacement of defective units in the ventilation system such as filters, corrected the fault. On other occasions, repair to cracked ventilation ducting was necessary. (3) Several theatres failed because of multiple faults in cleaning and defects in the ventilation system giving both incorrect airflow and high levels of BCP in the air. For example, on some occasions air baffles were found to be absent, fire dampers across the ventilation duct were closed, or unsealed windows and high level dust were also found. Particular problems are illustrated in three theatre suites which required repeated testing. Theatre suite 1. This theatre suite was tested following major upgrading works that had occurred 6 months previously. Tests carried out immediately after upgrading were satisfactory. The re-testing was requested because of insects and pests noted to be infesting the theatre and a
J. Holton
32
et al.
collection of bird feathers in the ceiling lights. Testing revealed excessive BCP in the air of all three theatres in the suite and the suite was closed. On inspection it was noted that there had been a failure to seal the roof space from the exterior and nesting pigeons were found in the roof space. There had also been a failure to effectively seal the ceiling between the roof spaces above the theatres, allowing access of the pigeons to the false ceiling and insects into theatre, and behind the theatre control panel. The air intake in the roof space was unsealed, with one of the walls absent, allowing about 60% of the air to the theatre to come directly from the pigeon-infested loft. In addition, removal of the false ceiling demonstrated that the rewiring was dangerous. Inspection of work had not been carried out previously, owing to closure of the false ceiling before hand-over from the contractors. Theatre suite 2. This was a commissioning test. BCP counts of five times the recommended levels were found. There was obvious evidence of a poor final clean. After a second clean, tests also failed, with high counts of BCPs. A particle count revealed a size distribution larger than the specification of the filter should have allowed. On inspection of the ventilation system it was noted that the ducting contained large amounts of brick dust, and although the ducting was supposed to have been vacuum cleaned, it had been unsupervised. After vacuum cleaning of the ducting system the tests were within the recommended limits. Theatre suite 3 (Figure 1). This theatre suite was tested as part of its commissioning. Entraining of air under the doors from recovery (R) into the
LA Theatre
Figure
suite
L P PR
B
1. Diagram
D A E R -3 +
of Theatre
suite
3 showing
Lift shaft and stair to theatre complex Preparation room Pump room Operating theatre Disposal room Anaesthetic room Entrance lobby Recovery room Air flow correct Air flow incorrect
direction
well,
exterior
of airflow.
Commissioning
of operating
theatres
33
preparation room (P2) and disposal room (D2) was noted. Also there was air flow from the lift well outside the whole complex and from theatre suite B into the entrance lobby E, and a high air flow from the lobby into the recovery room of theatre suite 3. This theatre suite was tested on six occasions. The results of the BCP counts are given in Table I. It can be seen that high counts were consistently found in the part of the theatre suite nearest to the entrance lobby and lift well (P2-A2). This probably reflects entraining of air from the lift and stair well into this side of the theatre suite, enhanced by the pumping action of the lift upon the air mass within the lift well. The varied reasons for failure were as follows: initially the filters were found to have been fitted back to front. The refitted filter bypassed the main dropper duct, and it was found that the ducting required cleaning. Subsequently the plant shut off during testing because of overload. New overloads when fitted also failed. Finally it was found that the belt drive had been fitted incorrectly. On rectifying this the theatre passed its sixth commissioning test. Table
I. Bacteria
carrying particles per cubic metre of air in various locations within on dzyerent test dates
Theatre 3
Date Room*
25:s
I:6
22:6
29:6
3:7
13:7
204-f 198
106 73
145 99 154 79 231 33
4
FE ND
66
204 ND 52 99 13
72 99
T2 R PI Tl Al R
112 158 112 145 66
138
it
1:; ND
46 53 ND
2: ND
:: ND ND
* P2, preparation room; room 1; Al, anaesthetic t BCP mm3 of air tested.
A2, anaesthetic room 1; Tl,
room operating
2; T2, operating room room 1; R. recovery;
2; PR, ND,
pump room; not done.
E 52 ND 39 ND Pi,
preparation
Many other faults were also noted during the various microbiology tests carried out over the study period. These included poor final cleaning, faulty workmanship, air baffles fitted the wrong way round, poor sealing to ventilation ducting and ill-fitting doors. Discussion
Within the hospital environment there are few areas where problems associated with infection control will not be a feature. It is important that the Infection Control Team is involved at an early stage in the planning of new facilities, and also at the final stage before opening. One critical area is the provision of new or refurbished Operating Departments. Advice is
34
J. Holton
et al.
available on what tests should be performed by the Microbiology Department as part of the commissioning process. We endorse Kundsin’s (1977) fi ve criteria for such microbiological monitoring which are that it must be planned, purposeful, scientifically accurate, properly analysed and effectively communicated. The involvement of the microbiologist in theatre testing allows the opportunity to carry out formal tests under carefully defined conditions and allows for the examination of the plant, and the overall standard of workmanship. We have demonstrated the value of such microbiological involvement in theatre testing both at commissioning and after upgrading. Major faults can be picked up by simple tests, such as monitoring airflow directions and BCP counts. Although outside air is unlikely to be a source of heavy bacteriological contamination, the source of air flow into theatres may highlight building errors. In some cases, despite major defects, these two indicators may be within normal limits but the commissioning test gives the opportunity to inspect the operating theatre suite and identify other faults. We recommend that the final inspection of the contract work is supervised by a member of the hospital engineering department, particularly duct vacuum cleaning and theatre cleaning. We further recommend that there should be close cooperation between the engineering and microbiology departments for effective supervision of theatre commissioning and upgrading. References Arrowsmith, L. W. M. (1985). Air sampling in operating theatres. Journal of Hospital Infection 6, 352-353. DHSS, 1982. Ventilation of operating theatre suites. A Joint Working Party Report. DHSS, 1983. Ventilation of operating department. A design guide. Study Group 10. Editorial (1984). Air sampling in operating theatres. Journal of Hospital Infection 5, l-2. Kundsin, R. B. (1977). Microbiological monitoring of the hospital environment in infection control in Health Care facilities. In Microbiological Surveillance (Cundy K. R. & Bail, W. Eds). University Park Press, Baltimore. Lidweii, 0. M., Lowbury, E. J. L., Whyte, W., Blowers, R., Stanley, S. & Lowe, D. (1982). Thk effect bf uitraci&n a& in oper&g rooms on deep sepsis in the joint after t&al hip or knee reuiacement: a randomised studv. British Medical Yournal285. 10-14. Medical Research Council (1962). Design and ventilation of operating room suites for control of infection and comfort. Lancet 2, 945-951. Whyte, W., Lidweii, 0. M., Lowbury, E. J. L., Blowers, R. (1983). Suggested bacteriological standards for air in ultraclean operating rooms. Journal of Hospital Infection 4, 133-I 39.
of Hospital
Infection (1990)
A microbiologist’s
J. Holton,
16, 2934
view
of commissioning theatres
G. L. Ridgway
operating
and A. J. Reynoldson*
Department of Microbiology, University College and Middlesex School of Medicine and *Engineering Services Department, Middlesex Hospital, London WI Accepted for publication
23 February
1990
Summary:
We report our experiences of microbiological testing of operating theatres over a lo-year period. Major faults within the theatres can be detected by microbiological monitoring of air flow direction and the bioload in theatre air. We advocate that there should be a close cooperation between the microbiologist and the hospital engineering department for effective monitoring of theatre commissioning and upgrading. Also we recommend that contract work should be closely supervised particularly with respect to theatre ventilation systems.
Keywords:
Operating
theatres;
commissioning;
aerobiology.
Introduction Operating theatre design in the U.K. is based upon the recommendations of a Medical Research Council report (Medical Research Council, 1962). The underlying theme is one of zoning, with increasing levels of cleanliness centred around the preparation and operating rooms. The rooms are plenum ventilated with approximately 20 changes of air per hour in the preparation and operating rooms and decreasing numbers of air changes in the other rooms and corridors giving an air flow directed outward from the operating or preparation room. Operations such as orthopaedic prosthetic implants, where the consequences of infection may be disastrous, are often performed in ultraclean air theatres which deliver high rates of air flow within a fully- or partially-walled enclosure within the operating room. This area encloses the operating team. Clear evidence has been obtained that using ultraclean air specifically for clean orthopaedic operations can substantially reduce the infection rate (Lidwell et al., 1982). The contribution of airborne organisms to wound infection for other types of operations is unknown. Despite this, Correspondence Grafton Way,
0195-6701/90/050029+06
to: London
Dr
G. L. Ridgway, WClE 6AU.
Department
of Microbiology,
$03.00/O
University
College
0 1990 The Hospital
29
Hospital,
Infection
Society
30
J. Holton
et al.
results with orthopaedic surgery have been extrapolated to suggest that the quality of the air must be maintained within certain limits in all operating theatres and guidelines for these limits have been proposed (DHSS, 1982) and subsequently modified (Arrowsmith, 1985). In an empty operating theatre there should be less than 35 colony forming units (cfu) of bacteria per cubic metre of air, with less than 1 cfu of Clostridium perfringens or Staphylococcus aweus in 30 m 3. During an operation there should be less than 18Ocfu mP3. It has been proposed that ultraclean air theatres have more stringent requirements (Whyte et al., 1983). For example, in a partially walled enclosure with a downward airflow and with the operating team not wearing exhaust body suits, there should be less than 20 cfu me3 at the periphery of the enclosure and less than 10 cfu rnw3 in the centre. In addition to the bioload in the air, the direction of airflow is important and should be from the central ‘clean’ area to the peripheral ‘dirty’ areas. Recommended air flow rates ranging from O-28 to 0.47 m3 s-r across an open door are given to prevent backflow into a relatively ‘cleaner’ area (DHSS, 1983). In an ultraclean air enclosure the airflow should be not less than O-2 m s-i 1 m above the floor (Whyte et al., 1983). It is recommended that microbiological testing of theatres should be performed at commissioning and after any major refurbishment. However, the value of such testing has been questioned (Editorial, 1984). We do not advocate routine microbiological testing of operating theatres other than for ultraclean suites, but have for the last ten years followed a policy of commissioning new and refurbished operating theatres after all works have been completed, but before surgery commences. We report our experiences here. Materials
and
methods
Operating theatres Our central London teaching hospital complex comprises 12 operating suites at nine geographical locations. Eleven of the operating suites are conventionally ventilated and one is an ultraclean air suite containing two theatres. Most were built before 1962 and do not conform to modern architectural practice. Testing Testing of theatres was performed at commissioning and after upgrading, or refurbishment to the ventilation plant or air conditioning system. The ultraclean air suite is tested on a regular basis, and is not the subject of this study. Testing followed the guidelines laid out in DHSS (1983). Before commissioning and testing, the following criteria were required: (i) all building and engineering works were completed; (ii) the ducting had been vacuum cleaned; (iii) the plant had been running at full power for 24 h prior to the test; (iv) there was no other activity in the theatre.
Commissioning
of operating
theatres
31
The theatres were tested by noting the direction of air movement using a smoke test (MSA Vent-Smoke Tubes, Glasgow); checking, where appropriate, the air velocity using a hot wire anemometer (Edra SLV, Airflow Developments Ltd), performing counts of bacteria-carrying particles (BCP) by sampling 30 1 of air using a Cassella slit sampler MK II (Casella, London) and 5% Columbia blood agar plates. The operator was absent from the room during slit sampling. Plates were incubated at 37°C and room temperature for 48 h before being counted. Finally, visual inspection of the fabric of the building was carried out. Occasionally, particle counting using a Status 4000 (Hawksley & Son, Lancing, UK) was performed. A theatre failed a test if any of the following were found: (a) an airflow direction (or velocity) not conforming to the recommendations of DHSS (1983); (b) counts of bacteria-carrying particles greater than 3.5 cfu m-3 in an empty conventionally ventilated theatre; > 18Ocfu mW3 at a post-commissioning check; we did not look for Clostridium perfr-ingens; (c) unacceptable defects of fabric, e.g. peeling plaster, exposed pipework, or damaged flooring. Results
The results cover the period 1978-l 988 and the theatres were tested on over 60 occasions and failed on 24. Most testing followed engineering works to the existing ventilation system rather than commissioning of new plant. The reasons for failure fell into three categories. (1) Theatres failed because the air flow direction was incorrect, and this necessitated adjusting the ventilation balance before a successful test was achieved. The counts of BCP were within the recommended limits. (2) Although the direction of the airflow was correct the counts of BCP were in excess of the recommended limits. In a few instances this was corrected after the theatre had received a thorough second cleaning, removing high level dust missed on the first occasion. On some occasions replacement of defective units in the ventilation system such as filters, corrected the fault. On other occasions, repair to cracked ventilation ducting was necessary. (3) Several theatres failed because of multiple faults in cleaning and defects in the ventilation system giving both incorrect airflow and high levels of BCP in the air. For example, on some occasions air baffles were found to be absent, fire dampers across the ventilation duct were closed, or unsealed windows and high level dust were also found. Particular problems are illustrated in three theatre suites which required repeated testing. Theatre suite 1. This theatre suite was tested following major upgrading works that had occurred 6 months previously. Tests carried out immediately after upgrading were satisfactory. The re-testing was requested because of insects and pests noted to be infesting the theatre and a
J. Holton
32
et al.
collection of bird feathers in the ceiling lights. Testing revealed excessive BCP in the air of all three theatres in the suite and the suite was closed. On inspection it was noted that there had been a failure to seal the roof space from the exterior and nesting pigeons were found in the roof space. There had also been a failure to effectively seal the ceiling between the roof spaces above the theatres, allowing access of the pigeons to the false ceiling and insects into theatre, and behind the theatre control panel. The air intake in the roof space was unsealed, with one of the walls absent, allowing about 60% of the air to the theatre to come directly from the pigeon-infested loft. In addition, removal of the false ceiling demonstrated that the rewiring was dangerous. Inspection of work had not been carried out previously, owing to closure of the false ceiling before hand-over from the contractors. Theatre suite 2. This was a commissioning test. BCP counts of five times the recommended levels were found. There was obvious evidence of a poor final clean. After a second clean, tests also failed, with high counts of BCPs. A particle count revealed a size distribution larger than the specification of the filter should have allowed. On inspection of the ventilation system it was noted that the ducting contained large amounts of brick dust, and although the ducting was supposed to have been vacuum cleaned, it had been unsupervised. After vacuum cleaning of the ducting system the tests were within the recommended limits. Theatre suite 3 (Figure 1). This theatre suite was tested as part of its commissioning. Entraining of air under the doors from recovery (R) into the
LA Theatre
Figure
suite
L P PR
B
1. Diagram
D A E R -3 +
of Theatre
suite
3 showing
Lift shaft and stair to theatre complex Preparation room Pump room Operating theatre Disposal room Anaesthetic room Entrance lobby Recovery room Air flow correct Air flow incorrect
direction
well,
exterior
of airflow.
Commissioning
of operating
theatres
33
preparation room (P2) and disposal room (D2) was noted. Also there was air flow from the lift well outside the whole complex and from theatre suite B into the entrance lobby E, and a high air flow from the lobby into the recovery room of theatre suite 3. This theatre suite was tested on six occasions. The results of the BCP counts are given in Table I. It can be seen that high counts were consistently found in the part of the theatre suite nearest to the entrance lobby and lift well (P2-A2). This probably reflects entraining of air from the lift and stair well into this side of the theatre suite, enhanced by the pumping action of the lift upon the air mass within the lift well. The varied reasons for failure were as follows: initially the filters were found to have been fitted back to front. The refitted filter bypassed the main dropper duct, and it was found that the ducting required cleaning. Subsequently the plant shut off during testing because of overload. New overloads when fitted also failed. Finally it was found that the belt drive had been fitted incorrectly. On rectifying this the theatre passed its sixth commissioning test. Table
I. Bacteria
carrying particles per cubic metre of air in various locations within on dzyerent test dates
Theatre 3
Date Room*
25:s
I:6
22:6
29:6
3:7
13:7
204-f 198
106 73
145 99 154 79 231 33
4
FE ND
66
204 ND 52 99 13
72 99
T2 R PI Tl Al R
112 158 112 145 66
138
it
1:; ND
46 53 ND
2: ND
:: ND ND
* P2, preparation room; room 1; Al, anaesthetic t BCP mm3 of air tested.
A2, anaesthetic room 1; Tl,
room operating
2; T2, operating room room 1; R. recovery;
2; PR, ND,
pump room; not done.
E 52 ND 39 ND Pi,
preparation
Many other faults were also noted during the various microbiology tests carried out over the study period. These included poor final cleaning, faulty workmanship, air baffles fitted the wrong way round, poor sealing to ventilation ducting and ill-fitting doors. Discussion
Within the hospital environment there are few areas where problems associated with infection control will not be a feature. It is important that the Infection Control Team is involved at an early stage in the planning of new facilities, and also at the final stage before opening. One critical area is the provision of new or refurbished Operating Departments. Advice is
34
J. Holton
et al.
available on what tests should be performed by the Microbiology Department as part of the commissioning process. We endorse Kundsin’s (1977) fi ve criteria for such microbiological monitoring which are that it must be planned, purposeful, scientifically accurate, properly analysed and effectively communicated. The involvement of the microbiologist in theatre testing allows the opportunity to carry out formal tests under carefully defined conditions and allows for the examination of the plant, and the overall standard of workmanship. We have demonstrated the value of such microbiological involvement in theatre testing both at commissioning and after upgrading. Major faults can be picked up by simple tests, such as monitoring airflow directions and BCP counts. Although outside air is unlikely to be a source of heavy bacteriological contamination, the source of air flow into theatres may highlight building errors. In some cases, despite major defects, these two indicators may be within normal limits but the commissioning test gives the opportunity to inspect the operating theatre suite and identify other faults. We recommend that the final inspection of the contract work is supervised by a member of the hospital engineering department, particularly duct vacuum cleaning and theatre cleaning. We further recommend that there should be close cooperation between the engineering and microbiology departments for effective supervision of theatre commissioning and upgrading. References Arrowsmith, L. W. M. (1985). Air sampling in operating theatres. Journal of Hospital Infection 6, 352-353. DHSS, 1982. Ventilation of operating theatre suites. A Joint Working Party Report. DHSS, 1983. Ventilation of operating department. A design guide. Study Group 10. Editorial (1984). Air sampling in operating theatres. Journal of Hospital Infection 5, l-2. Kundsin, R. B. (1977). Microbiological monitoring of the hospital environment in infection control in Health Care facilities. In Microbiological Surveillance (Cundy K. R. & Bail, W. Eds). University Park Press, Baltimore. Lidweii, 0. M., Lowbury, E. J. L., Whyte, W., Blowers, R., Stanley, S. & Lowe, D. (1982). Thk effect bf uitraci&n a& in oper&g rooms on deep sepsis in the joint after t&al hip or knee reuiacement: a randomised studv. British Medical Yournal285. 10-14. Medical Research Council (1962). Design and ventilation of operating room suites for control of infection and comfort. Lancet 2, 945-951. Whyte, W., Lidweii, 0. M., Lowbury, E. J. L., Blowers, R. (1983). Suggested bacteriological standards for air in ultraclean operating rooms. Journal of Hospital Infection 4, 133-I 39.