Commissioning operating theatres

Journal of Hospital Injection (1993) 23, 153-160

INFECTION

Commissioning J. Holton Department

of Medical

CONTROL

operating

Operating

theatres

and G. L. Ridgway

Microbiology, University College London, School, London, WlP 7PN

Accepted for publication Keywords:

IN PRACTICE

theatre;

Medical

29 December 1992

commissioning;

air sampling;

standards

Introduction Ever since Lister introduced his carbolic spray in 1867 in order to destroy the agents of putrefaction floating in the air of his operating theatre (which he later realized the spray could not do), the role of air as a source of infection has been a matter of dispute. Despite a reduction in mortality, mainly due to sepsis, from 63% to 18% after introduction of the spray, Lister came to believe that the spray was relatively ineffective, and the air was probably less important than other sources. Coincident with using the carbolic spray, Lister also introduced many other changes to his operations, developing what we would now call aseptic techniques. He believed that these measures resulted in his lower sepsis rates.’ Positive (plenum) pressure ventilation of operating suites was introduced in the 194Os, resulting in a reduction in the number of bacteria detected in the air, which was paralleled by a reduction in the post-operative sepsis rate. However, other changes in operative techniques had also been introduced and there was no direct comparison of sepsis rates with and without plenum ventilation. In the mid 196Os, Charnley introduced a ventilation system which filtered and recirculated air, producing a laminar air flow over the operation site. A marked reduction in the number of airborne bacteria occurred and the post-operative sepsis rate fell from 8.9% to 0.9%.’ Again, changes in operative techniques were introduced simultaneously, making it difficult to determine the precise contribution of airborne bacteria to the sepsis rate. In 1974, a large controlled multicentre trial in the UK and Sweden was set up to determine the relevance of air quality to post-operative sepsis, by

154

J. Holton

and G. L. Ridgway

comparing the sepsis rate in a conventional plenum ventilated operating room to the sepsis rate in the ultra clean air theatres advocated by Charnley. The results unequivocally demonstrated that the lower the counts of airborne bacteria, the lower the sepsis rate. 3 This large trial only addressed the post-operative joint sepsis rate following prosthetic implants in cold orthopaedic surgery. The importance of the aerial route to post-operative sepsis in these operations cannot be necessarily extrapolated to other types of operation. Circumstantial evidence suggests that the air can be a source of post-operative sepsis, particularly if individuals in the theatre team disperse large numbers of organisms.4 However, the value of conventional plenum ventilation systems in operating suites is questionable’ and the role of the airborne bacteria as a source of infection for most types of operation continues to be a matter for debate. It seems likely that there is a relationship between quality of the air and the degree of asepsis. With a moderate level of asepsis, improvement of air quality from high levels of contamination to moderate levels of contamination will have a detectable effect on sepsis. However, further improvement in sepsis rates will be dependent on better aseptic technique and there would be no point in trying to improve air quality further. In contrast, where the degree of asepsis is high, the contribution of the air quality to sepsis will be greater unless the bacterial count is reduced to very low levels.6 Despite the lack of formal demonstration that the air is an important source for post-operative infection in general surgery it is recommended that operating theatres should conform to a minimum standard of design and ventilation control, not only to dilute the airborne bacteria but also to maintain an equable temperature and humidity in the theatre.7’s

Operating

theatre

standards

The design and operating parameters for a theatre ventilation system are set out in a DHSS Engineering Data document.’ Although intended for the Hospital Engineering Department, the Microbiologist should be familiar with its contents, particularly those sections concerned with the basic design of the suite and the air handling plant, and the recommendations for commissioning and post-commissioning microbiological tests. The usual temperature range in operating rooms is between 1%25°C depending on the ambient external temperature. The relative humidity should be between 40-60% and the airflow should be between 0*13-0.25 m s-’ in the operating room. There should be 17-20 air changes per hour in the operating room to maintain an effective dilution of the bioload in the air. The airflow direction should be from ‘clean’ to ‘dirty’ areas, that is from the operating room out into all other rooms. The preparation room can be considered as part of the operating room if a full

Commissioning

operating

theatres

155

tray service is provided, and the instruments are not laid out in the preparation room. If on the other hand, instruments are laid out in the preparation room the airflow should be directed from this room into the operating room. Other airflow directions should be from anaesthetic rooms into recov’ery or lobby and from the theatre suite out into the rest of the hospital. It is recommended that the bioload should not exceed 35 bacteria carrying particles per cubic metre of air (bcp rn- 3, in an empty theatre or 180 cfu mm-’ during an operation.“’ The operating parameters for an ultra clean air theatre are different from those for a conventionally ventilated theatre, and depend upon the design of the system. Whyte et al. have suggested bacteriological standards for ultra-clean air operating rooms. ‘i In a fully walled enclosure the airflow 1 m from the filter face should not fall below 0.3 m s-’ but in a partially walled enclosure, because there is a greater diffusion of air, the airflow at 1 m from the floor (about the level of the operating table surface), should not be less than 0.2 m s-i. These minimum values should be met even under the most adverse temperature differential where warm air is supplied into a cold theatre. The integrity of the enclosure is measured by the penetration of particles into the enclosure from outside and each of the four walls of the enclosure should have been tested. At 1 m from the floor in the centre of the enclosure there should be less than 1% penetration of the particles, and less than 10% penetration at each of four points in the periphery of the enclosure. Particle testing should not be carried out as part of the microbiological commissioning, but the Microbiologist should confirm that such testing has been done, and the result is satisfactory. Bacterial counts at 1 m from the floor should be less than 1.0 bcp mm3 of air in an empty enclosure and when tested during an operation there should be less than lObcpm-” at the level of the operating table in the centre of the enclosure. Additionally, if the system is partially vvalled, then on each of the four sides at the periphery of the enclosure the bacteriological counts should not exceed 20 bcp me3.

When

to test

It can be argued that in a conventionally ventilated theatre, all that is required as commissioning checks is an assessment of the physical engineering parameters. However, a bacteriological assessment of the air quality in the theatre can also be of value in highlighting defects in the ventilation system.‘* In an ultra-clean air theatre, regular bacteriological assessment is mandatory because factors other than simple ventilation parameters are important in determining the quality of the air. These would include the type of garment worn by the operating team. The use of air sampling thus becomes a quality control measure for the theatre. A conventionally ventilated theatre requires microbiological checks at

156

J. Holton

and G. L. Ridgway Pre-commissioning

All building and engineering work completed Ducting clean by vacuum extraction Plant running for at least 24 h No other activity in theatre suite

Air quality

Workmanship

Check: air change rate ventilation balance bacteria carrying particle counts (BCP)

Check: terminal cleaning joint sealing gaps around doors temperature/ humidity

Post-commissioning

Figure 1. Plan for commissioning

of operating theatres.

and at any commissioning (Figure l), immediately after commissioning major refurbishment. Routine microbiological assessment is not required. In contrast, an ultra-clean air theatre requires assessment not only at commissioning, but also as part of the routine service to the theatres, and ideally the microbiological checks should be performed every 3 months. Routine checks are required because of the long incubation period for joint sepsis, and any system defect needs to be detected early and rectified quickly. Material required for testing The materials required for the microbiological theatres are: (1) a hot-wire Gallenkamp

or vane anemometer Ltd;

covering

assessment

of operating

the range O-5 m s-l

e.g.

Commissioning

operating

157

theatres

(2) smoke tubes, e.g. MSA, Queenslie Estate, Glasgow; (3) a microbiological air sampler. The Casella slit sampler (Mk 2 Large Model) is the instrument of choice. It has a separate air inlet and outlet and the airflow is driven by a vacuum pump. A rotating table takes a 15 cm plate and it can sample air from 30 1 min-’ to 700 1 min- ’ through 1, 2, 3 or 4 slits, each 4.45 cm by 0.1 mm dimensions, contained in the sampling head. The centrifugal air sampler (Biotest RCS Folex Ltd) has a central impeller which drives air on to an agar strip slotted into the circumference of the sampling head. There is no separate air outlet and the exact sampling rate is in doubt. The manufacturer suggests a rate of 40 1 min-’ although various measurements have suggested flow rates of 340 1 min-’ or less than 5 pm are not 1661min ’ for particles of 17 l.lrn. ” Particles effectively sampled. l4 The centrifugal sampler is adequate for most monitoring tasks, particularly if comparative measurements rather than absolute values are required. ‘s However, the instrument is not adequate for testing ultra-clean air theatres and a Casella slit sampler is essential. Settle plates have no role in the commissioning of operating theatre suites. They may occasionally be of value in the investigation of specific operating theatre associated infections. (4) Any general

purpose

agar such as nutrient

Assessment

or blood

agar

of air quality

The microbiological assessment of operating theatres requires close co-operation with the Hospital Engineering Department. One should determine that the necessary physical parameters of number of air-changes and ventilation balance have been passed by the engineers. A certificate confirming that the ducting has been vacuum cleaned prior to hand over should be obtained. The theatre should have been fully cleaned, the doors closed, and the ventilation system working at full power for at least 1 h prior to testing, and preferably overnight. The theatre suite should be empty apart from the individual performing the tests, who should change into theatre garments including a close fitting mask. It is preferable to start by sampling the air-quality before any other measurements are taken. Microbiological sampling of air Conventional plenum ventilated theatre. The sampler is placed in the centre of the operating room, about 1 m from the floor and duplicate samples, each of 1 m3 of air are sampled on to separate 5% blood or nutrient agar plates. Similar samples are taken in the anaesthetic room, preparation room, recovery room and lobby. A control plate is processed by loading and unloading the air-sampler. All the plates should be incubated at 37°C for 48 h before counting the number of colonies.

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J. Holton

and G. L. Ridgway

Ultra-clean air theatre. A copy of the results of the filter efficiency test and the degree of penetration of test particles should be obtained from the contractors who installed the system. The Casella slit sampler, set to work at a maximum volume of 700 1 min-‘, is placed 1 m from the floor, in a central location (test 1). In addition, for a partially walled system, the slit sampler should be placed peripherally at each of the four sides of the enclosure (test 2). The sampler should be switched on outside the enclosure and at least 10 m3 of air sampled per test. At the maximum sampling rate for the recommended air sampler this will require about 15 min per test. Testing of air velocity and air jlow Once the air quality has been tested, the speed and direction of the air-flow can be determined using the anemometer and smoke tubes. The anemometer is placed in the air-stream, perpendicular to the direction of flow and the value is recorded. When using a vane-anemometer it is important to ensure that the measuring head is pointing in the correct direction to the line of air-movement. It is as well to measure the air-flow at several locations particularly in an ultra-clean air enclosure. The direction of air-flow is determined using the smoke tubes. In a conventionally ventilated theatre the direction of the air-flow should be determined at inlet and outlet grills and at each of the doors, with the door closed and open. Open doors should be checked at top and bottom. The net flow should be in the direction ‘clean’ to ‘dirty’. However, depending upon the air balance and the temperature differentials between the rooms some counter-flow may occur across the base of an open door. This can be safely ignored, but it should nevertheless be recorded. In an ultra-clean air theatre, the flow of air should be determined beneath the hood, at several locations, centrally and peripherally. In a partially walled enclosure the air curtain can be tested by directing the smoke towards the air curtain from outside the enclosure at different heights from the floor, and against all four faces. It is as well to check for entrainment under the base of the curtain, particularly with the theatre doors open and closed. Assessment

of quality

of workmanship

On completion of these measurements the general finish of the theatre suite can be checked. Look particularly for evidence of a poor terminal clean, missing panels, poor sealing around corners and at floors/wall joins, and for the correct type of wash basins and fittings for taps. Check the gaps along the doors. The recommended limits are 4 mm at the base, 3 mm at the top and sides and 2 mm between double doors. Finally note the temperature and humidity and ensure that the users are aware of how to interpret warning lights and operate any environment controls in the operating room. One should confirm that where a set back facility is provided to reduce air

Commissioning

operating

changes during periods of inactivity, operating room will not be used whilst

theatres

159

checks exist to ensure that the the air supply is in set back mode.

Post-commissioning

checks

Once the theatre has been handed over from the contractors to the Health and the commissioning checks have been satisfactorily Authority completed, a post commissioning check should be performed whilst the theatre is in normal use. For a conventionally ventilated theatre it is sufficient to test once. The presence of excessive numbers of people or excessive movement during testing should be recorded. The air sampler should be positioned in a location as near to the operating table as convenient, but away from traffic. Duplicate air samples, each of 1 m3, should be obtained, and the plates (with controls) should be incubated as previously, before counting the number of colonies. When performing post-commissioning checks on ultra-clean air theatres, one should initially sample 20 m3 of air, with the sampler placed within 30 cm of the operating site. In some cases, an extension tube will have to be fitted to the sampler and if this is done the sampling efficiency of the apparatus should be reassessed using a known aerosol challenge prior to use in the theatre. An equivalent volume of air should also be sampled at the periphery of the enclosure at the working height. Five operations should be monitored. After the initial post-commission checks, routine air sampling of ultra clean air theatres requires only a check on one operation with the sampler placed centrally and peripherally at working height and 20 m3 of air sampled at each location. Calculation

One cubic metre of air m-3) can be calculated plate (N) and the total can be calculated from test (T min).

and communication

of results

is equivalent to 1000 litres. Thus the bioload (B bcp from the number of colonies counted on the sample volume of air sampled. The total volume sampled the sampling rate (R 1 min-‘) and the duration of the

B

=

lOOON

RT

bcp mm3

The results should be recorded for each of the rooms in the theatre suite. The air-flow direction and velocity can be conveniently recorded on a plan diagram of the operating suite. Some comment as to the interpretation of the results should be made, e.g. that the theatre has passed the commissioning tests and is suitable for use or that the unit has failed and detailing the defects that need to be rectified. A record of the results should be sent to the Unit General Manager, the Theatre Manager and the Hospital Engineer.

160 This

J. Holton is one in a series of invited

articles

and G. L. Ridgway that provide

guidelines

on infection

control

practice.

References J. An address on the present position of aseptic surgery. BY MedJ 1890; 2: 377. J. Post operative infection after total hip replacement. Clin Orthop 1972; 87: 167-187. Lidwell OM, Lowbury EJL, Whyte W, Blowers R, Stanley SJ, Lowe D. Effect of ultraclean air in operating rooms on deep sepsis in a joint after total hip or knee replacement: a randomised study. BY Med J 1982; 285: 1@14. Ayliffe GAJ, Collins B. Wound infections acquired from a disperser of an unusual strain of S. aureus. J Clin Path01 1967; 20: 195-198. Ayliffe GAJ. Role of the environment of the operating suite in surgical wound infections. Rev Infect Dis 1991; 13 (Suppl. 10): S8OtXS804. Lidwell OM. Bacteriological considerations. In Johnson IDA, Hunter AR Eds. The Design and Utilisation of Operating Theatres. London: Edward Arnold, 1984: 22-28. Report. Design and ventilation of operating-room suites for control of infection and for comfort. Lancet 1962; 2: 945-951. NHS Estates 1991. Health Building Note 26. Operating Departments. DHSS, 1983. Ventilation of Operating Department. A Design Guide. Arrowsmith WM. Air sampling in operating theatres. J Hasp Infect 1985; 6: 352-353. Whyte W, Lidwell OM, Lowbury EJL, Blowers R. Suggested bacteriological standards for air in ultra-clean operating rooms. J Hasp Infect 1983; 4: 133-139. Holton J, Ridgway GL, Reynoldson AJ. A microbiologists view of commissioning operating theatres. J Hasp Infect 1990; 16: 29-34. Casewell MW, Fermle PG, Thomas C, Simmons NA. Bacterial air counts obtained with a centrifugal (RCG) sampler and a slit sampler-the influence of aerosols. J Hosp Infect 1984; 5: 76-82. Clark S, Lath V, Lidwell OM. The performance of the Biotest RCS centrifugal air sampler. J Hosp Infect. 1981; 2: 181-188. Casewell MW, Desai N, Leuse EJ. The use of the Reuter centrifugal air sampler for the estimation of bacterial air counts in different hospital locations. J Hasp Infect 1986; 7: 250-260. Lister

;: Charnley 3. 4. 5. 6. 7. 8. 1:: 11. 12. 13. 14. 15.