Experimental study of the effect of operating lamps on downward airflow distribution in an operating theatre at St. Olavs Hospital in Norway

Sisäilmastoseminaari 2017:

EXPERIMENTAL STUDY OF THE EFFECT OF OPERATING LAMPS ON DOWNWARD AIRFLOW DISTRIBUTION IN AN OPERATING THEATRE AT ST. OLAVS HOSPITAL IN NORWAY

Guangyu Cao1, Amar Aganovic1, Liv-Inger Stenstad2, Jan Gunnar Skogås2

1 Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway
2 St. Olavs Hospital, Trondheim, Norway

ABSTRACT

The objective of this study was to exam the effect of surgical lamps on the downward airflow distribution from the laminar ceiling diffuser in one operating theatre at St. Olav Hospital in Norway. Measurement results show that the height of the operating lamps may influence the particle concentration at the level of the operating table. The measured value of Colony Forming Unit (CFU) was higher when the operating lamps were located at a height of 1.92 m from the floor than at a height of 1.75 m from the floor. The angle of the operating lamps may also affect the particle concentration at the level of the operating table. The particle concentration (0.3-3.0 micron) increased when the angle of the operating lamps was changed from 45° to horizontal. However, the increase of measured particle concentration did not results in the increase of measured CFU, which may indicate that the CFU may be affected by other factors.

INTRODUCTION

The indoor air quality of operating theatres is important for patients and surgical staff in terms of surgical-site infections. Earlier studies showed that among surgical patients surgical-site infections (SSIs) are the most common hospital-acquired infections accounting for 36% of nosocomial infections /1-3/. Currently, SSI occurs for approximately 7% of all operations and is the third most frequently reported healthcare- associated infection in Sweden /4/. In Norway, the national average SSI rate was 2.0% which is higher than lower respiratory infection (1.4%), urinary tract infection (1.2%) and septicaemia (0.9%) in 2015 /5/.

In fact, the design of the microclimate in operating theatres (OT) is a complex task mainly due to the stability of air temperature, relative humidity, scheme of pressures, mean velocity and air quality /6/. The ultra-clean ventilation systems and laminar air flow ceilings are used in OTs to improve the indoor air quality. One early study found that the measured bacterial and particle concentrations close to the operating field and at the level of instrument table were 20-fold lower in operating theatres with laminar airflow ceilings than in hospital rooms used for diagnostic or therapeutic procedures without ultra-clean ventilation systems /7/. However, another individual study showed significantly higher severe SSI rates following knee prosthesis and significantly higher SSI rates following hip prosthesis under laminar airflow conditions /8-9/.

The objective of this study was to exam the effect of surgical lamps on the downward airflow distribution from laminar airflow ceilings close to the operating table in an operating theatre at St. Olav Hospital in Norway.

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EXPERIMENTAL SETUP The operating theatre (OT)

The measurements were conducted in a real OT which is located in St. Olav Hospital in Norway. In the middle of the OT, a laminar airflow ceiling was mounted to provide laminar downward airflow to the operating table (see Figure 1). In this study, five persons were employed during the measurements to mimic two surgeons, one patient, one assistant and one anaesthetist in simulated operations. Two people simulating surgeons stood beside the operating table with one assistant standing close to the operating table. The simulated anaesthetist sat close to the head of the simulated patient laying on the operating table. Two type of measurement instruments were installed closely to the operating table to measure the number concentration of particulate matter pollutants and colony forming unit (CFU) (see Figure 2).

Operation zone

Figure 1 A photo of the operating theatre with all the medical equipment used in real operations

Measurement instrument

CFU sampling plate

Simulated surgeons

Particle counter

Two TSI AeroTrak® Handheld Particle Counters Model 9306-v2 were used to measure the particle concentration. The particle counters may measure particles in the range of 0.3 to 10 μm with a flow rate of 0.1 CFM (2.83 L/min). The counting efficiency of this instrument is 50% at 0.3 μm; 100% for particles >0.45 μm (per ISO 21501-4 and JIS). The two AeroTrak counters have been calibrated by the manufacturer before the measurements.

a) b)

Figure 1 Measurement instruments, a) AEROTRAKTM Handheld Particle Counter Model 9306, b) CFU measurement device

Measurement conditions

Figure 2 The locations of the measurement instruments for CFU measurement and particle measurement

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The measurements were performed in the OT and all the normal procedures for a real operation were followed, including cleaning, room preparation, sterilization of operating field and equipment, and arrangement of surgical staff. Table 1 shows more detailed information of the 6 cases.

Table 1 measurement conditions

RESULTS
Measured fine particle concentration and CFU

Figure 4 shows the measured fine particle concentration (0.3-1.0 micron) and CFU in all cases. The measured particle concentration (0.3-1.0 micron) in Case 1 is lower than other cases. It may indicate that the downward laminar airflow may dominate the operating table area regarding the fine particle control when the lamps were located at the height of 1.92 m. However, the measured value of CFU in Case 1 is higher than the values in case 2- 4. In addition, Figure 1 shows that the installation angle of the operating lamp may not affect the dispersion of airborne fungus in case 3 and case 5. Due to the change of patient, the measured results in case 6 shows a drastic increase of particulate matter concentration and CFU concentration. This indicates the activity of the patient has a great impact of the local airborne pollutant distribution.

a)

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b)

Figure 4 The measured fine particle concentration and CFU, a) 0.3-0.5 micron, b) 0.5-1.0 micron

Measured coarse particle concentration and CFU

Figure 5 shows the measured coarse particle concentration (1.0-14 micron) and CFU in all cases. It shows the measured particle concentrations (1.0-3.0 micron) in Case 3-5 are higher than other cases. The results may indicate that the downward laminar airflow may be disturbed by the lamp near the operating table area when the lamps were located at the height of 1.75 m regardless the installation angle. However, the measured CFU is lower in case 3- 5 than in other cases. However, the lower CFU may be caused by the reduced number of door opening, which may be factor to induce more bacteria from outside of OT.

Figure 5a shows that the height of the lamps has different effect on particles with different sizes. When the height of the lamps was 1.92 m from the floor, the particle concentration (1.0-3.0 micron) is higher than other particle sizes: 0.3-1.0 micron and 3-14 micron. On the other hand, the particle concentration (1.0-3.0 micron) is higher in all cases than other particle sizes. This may indicate the increased CFU may be associated with particles with the size of 1.0-3.0 micron. However, this needs to be confirmed by more measurements due to the limited measured cases.

a)

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b)

Figure 5 The measured coarse particle concentration and CFU, a) 1.0-3.0 micron, b) 3.0- 5.0 micron, c) 5.0-10 micron, d) 10-14 micron

CONCLUSIONS

In operating theatres, many factors, including the number of staff, clothing, different airflow schemes, ventilation systems, supply airflow rate and the use of portable ultra- clean airflow unit, may influence the indoor air quality and SSI. Earlier studies have reported that the increased airflow rate and the use of laminar ultra-clean airflow may make contribution to reduce the SSI. However, few studies have reported the influence of surgical lights on the air distribution close to the operating table. This study found that the height of the operating lamps may influence the particle concentration at level of operating

c)

d)

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table. However, the measured CFU shows the opposite trend. The angle of the operating lamps may also affect the particle concentration at level of operating table. The particle concentration (0.3-3.0 micron) increased when the angle of the operating lamps was changed from 45° to horizontal. However, the change of the measured particle concentration did not results in the increase of measured CFU. This study indicates that the activity of the patient has a great impact of the local airborne pollutant distribution. The limited measurement cases may not find out the correlation between the measured particle concentration and CFU. More field measurements in different cases should be carried out to receive a better understanding of the effect of operating lamps together with other factors on measured particle concentration and CFU close to the operating table.

ACKNOLWLEDGEMENT

The authors wish to express their thanks for financial support from the Operating Room of the Future program at St. Olavs Hospital and the Norwegian University of Science and Technology, NTNU.

REFERENCES

1. Poggio, J.L. (2013) Perioperative Strategies to Prevent Surgical-Site Infection. Clin Colon Rectal Surg. Sep; 26(3): 168–173. doi: 10.1055/s-0033-1351133.

2. Klevens, R.M, Edwards, J.R, Richards, C.L Jr. et al. (2007) Estimating health care- associated infections and deaths in U.S. hospitals, 2002. Public Health Rep. 122(2):160–166.

3. Horan, T.C., Gaynes, R.P., Martone, W.J., Jarvis, W.R, Emori, T.G. (1992) CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol.13(10):606– 608.

4. Sadrizadeh, S., Tammelin, A., Ekolind, P., Holmberg, S. (2014) Influence of staff number and internal constellation on surgical siteinfection in an operating room. Particuology 13 42–51.

5. https://helsenorge.no/Kvalitetsindikatorer/infeksjoner/sykehusinfeksjoner#Se-resultater

6. Balocco, C., Petrone, G. and Cammarata, G. (2015) Numerical Investigation of Different Airflow Schemes in a Real Operating Theatre. J. Biomedical Science and Engineering, 8, 73-89. http://dx.doi.org/10.4236/jbise.2015.82008.

7. Hansen, D., Krabs, C., Benner, D., Brauksiepe, A., Popp, W. (2005) Laminar air flow provides high air quality in the operating field evenduring real operating conditions, but personal protection seems to be necessary in operations with tissue combustion. Int. J. Hyg. Environ.-Health 208, 455–460.

8. Brandt, C., Hott, U., Sohr, D., Daschner, F., Gastmeier, P., Ruden, H. (2008) Operating room ventilation with laminar airflow shows no protective effect on the surgical site infection rate in orthopedic and abdominal surgery. Ann Surg. 248(5):695-700.

9. Gastmeier P, Breier AC, Brandt C. Influence of laminar airflow on prosthetic joint infections: a systematic review. J Hosp Infect. 2012;81(2):73-8.

Denne fagartikkelen er knyttet til Gemini.no-saken: Operasjonslampas plassering virker inn på infeksjonsrisikoen etter operasjon