The influence of surgical hoods and togas on airborne particle concentration at the surgical site: an experimental study P. D. McGovern, M. Albrecht, S. K. Khan, S. D. Muller & M. R. Reed
Journal of Orthopaedic Science Official Journal of the Japanese Orthopaedic Association ISSN 0949-2658 J Orthop Sci DOI 10.1007/s00776-013-0445-7
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Author's personal copy J Orthop Sci DOI 10.1007/s00776-013-0445-7
ORIGINAL ARTICLE
The influence of surgical hoods and togas on airborne particle concentration at the surgical site: an experimental study P. D. McGovern • M. Albrecht • S. K. Khan S. D. Muller • M. R. Reed
•
Received: 13 January 2013 / Accepted: 16 July 2013 Ó The Japanese Orthopaedic Association 2013
Abstract Background Arthroplasty surgeons are increasingly using personal protection systems with helmets. It is theoretically possible for the fans in these helmets to blow squames, sweat droplets and orobronchial fomites onto the surgical site. A controlled experiment was set up to investigate the effect of different surgical gowns on counts of airborne particles measuring C0.3 lm, using a hand-held particle counter. Methods The clothing that was sequentially tested included the following: 1.
2.
3.
BarrierÒ surgical gown (single use) made from nonwoven polypropylene (Mo¨lnlycke Health Care Ltd, Dunstable, UK) StrykerÒ T5 Helmet (reusable) covered with a disposable StrykerÒ T4/T5 urethane hood worn separate to and enclosed by the BarrierÒ surgical gown both at the front and back StrykerÒ T5 Helmet (reusable) worn within a disposable StrykerÒ T4/T5 urethane zippered toga (Stryker Corporation, Kalamazoo, MI, USA)
P. D. McGovern Medway Maritime Hospital, Windmill Road, Gillingham, Kent ME7 5NY, UK M. Albrecht School of Statistics, University of Minnesota, 224 Church Street Southeast, Minneapolis, MN 55455, USA S. K. Khan S. D. Muller M. R. Reed Northumbria Healthcare NHS Foundation Trust, Woodhorn Lane, Ashington, Northumberland NE63 9JJ, UK S. K. Khan (&) 35 Fellsdyke Court, Sheriff Hill, Gateshead NE10 9SB, UK e-mail:
[email protected]
Six readings were taken for each of the following three setups in a randomised order: 1. 2.
Gown: surgeon with surgical gown and face mask Hood: surgeon with surgical gown and hood, maximum fan speed 3. Toga: surgeon with toga, maximum fan speed Wilcoxon rank sum tests were applied to assess equality of means between the three occlusive measures (gown, hood, toga). P values were computed based upon one-sided tests and adjusted for multiple comparisons using the Bonferroni correction. Results The mean particle counts (over more than 5 L of air) for the three set-ups were: gown: 1178 (least protective), hood: 328, toga: 42 (most protective). There was a significant reduction in particle counts for the toga versus gown (p = 0.007) and toga versus hood (p = 0.037); differences in particle counts were not significant between the hood and gown (p = 0.140). Conclusions The fans in the helmets do not increase contaminants by blowing particles from the head area. A significant reduction in surgeon-originated contaminants was seen with the toga compared to both the hood/gown separate ensemble and gowns alone.
Introduction The operating team are a potential source of microbe-laden airborne particles, which can contribute to surgical site infection [1, 2]. Laminar airflow (LAF) theatres are designed to remove these contaminants and deliver ultraclean air (less than 10 CFU/m3) to the surgical area [3, 4]. The attire for the scrub team has evolved as well, with many units introducing personal protection systems using
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Author's personal copy P. D. McGovern et al.
helmets [5]. These helmet systems differ from the ‘‘body exhaust’’ suits pioneered in the 1960s by Charnley [6, 7]. The helmets can be worn under a disposable hood-cover separate to the surgical gown, or under the all-in-one, surgical ‘‘toga’’ [8]. The helmets are lightweight with adjustable airflow rates and are connected to a rechargeable power pack clipped to the surgeon’s clothes. The fans are designed to bring air in from outside the hood and channel this down inside the face shield and out through the skirt of the surgical gown, into the region of the operating room floor. It is theoretically possible for the fans to blow some particles from the surgeon’s head onto the working area and potentially influence the incidence of surgical site infections. These include squames from the scalp and face, sweat droplets from the forehead, and squames, droplets and fomites from the oral cavity or the respiratory system [9, 10]. We therefore designed a controlled experiment to investigate the impact of toga, hood and normal gown on airborne particle concentrations near the surgeon’s hands at the level of the surgical site in a LAF theatre.
Materials and methods The experiment was set up in a partial-walled orthopaedic theatre under vertical LAF. The model installed in our unit (ExFlow 90; Howorth, Bolton, UK) incorporates an array of ceiling-mounted vents circumscribed by a solid plastic hood to stabilise airflow. This hood marks the LAF boundary and is identified on the theatre floor. Air within the LAF hood is considered ultra-clean [4]. A theatre with LAF active and undisturbed for 1 h (doors closed, theatre lights moved out of the way, patient warming measures removed [11]) was chosen. The experiment was conducted by two authors (MA and PM); one the monitor, the other the ‘‘surgeon’’. Both wore disposable tie-back theatre caps (Universal Hospital Supplies Ltd, Enfield, UK) throughout the experiment [12]. The monitor wore a standard Kimberly-ClarkTM tie-back facemask (Universal Hospital Supplies Ltd, Enfield, UK), and remained outside the LAF. The surgeon was scrubbed and held his hands clasped in front of his chest, to avoid interfering with the particle counter. The clothing that was sequentially tested included the following: 1.
2.
BarrierÒ surgical gown (single use) made from nonwoven polypropylene (Mo¨lnlycke Health Care Ltd, Dunstable, UK) StrykerÒ T5 Helmet (reusable) covered with a disposable StrykerÒ T4/T5 urethane hood worn separate to and enclosed by the BarrierÒ surgical gown both at the front and back
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3.
StrykerÒ T5 Helmet (reusable) worn within a disposable StrykerÒ T4/T5 urethane zippered toga (Stryker Corporation, Kalamazoo, MI, USA)
A handheld particle counter (Handilaz Mini, Particle Measuring Systems Inc., Boulder, CO, USA) was installed on a freestanding tripod at working height for the surgeon, i.e. at elbow height and 10 cm from his torso. Figure 1 shows the setup with the surgeon wearing a toga. The counter draws air at a constant rate of 2.83 L/min over a laser array and measures diffractions off ambient particles, inferring counts of particles 0.3, 0.5 and 5 lm in size [13]. Six readings were taken for each of the following three setups in a randomised order: 1. 2. 3.
Gown: surgeon with surgical gown and face mask Hood: surgeon with surgical gown and hood, maximum fan speed Toga: surgeon with toga, maximum fan speed
Each reading lasted 2 min, sampling more than 5 L of air. The study protocol included 1-min delays between consecutive setups to allow theatre conditions to equilibrate. The surgeon did not change his attire between readings during a single setup. He uttered the same sentences during each reading, simulating the normal conversation during the procedure. Statistical analysis Wilcoxon rank sum tests were applied to assess equality of means between the three occlusive measures (gown, hood,
Fig. 1 The particle-counter installation, demonstrated for the toga setup (surgeon with toga, fan on maximum ventilation). The particle counter is indicated by the white arrow
Author's personal copy Ambient particles with hoods and togas
toga). P values were computed based upon one-sided tests and adjusted for multiple comparisons using the Bonferroni correction. P values of less than 0.05 were deemed significant.
Table 1 Raw particle counts for the three setups, classified by particle size Setup type
0.3 lm
Gown
Results Particle counts quantify the degree to which different occlusive clothing types prevented surgeon-borne contaminants from being emitted into the vicinity of the surgical site (Table 1; Fig. 2). The degrees of protection offered by the three occlusive measures are best categorised as follows: the gown offered the least protection, with a mean particle count(SD) of 1178(96); the hood offered moderate protection, with a mean particle count of 328(22); and the toga offered the best protection with a mean particle count of 42(3) (all particles were counted over more than 5 L of air). Statistical comparisons between all three occlusive measures (Table 2) identified a significant reduction in particle counts for the toga versus gown (p = 0.007) and toga versus hood (p = 0.037); differences in particle counts were not significant between the hood and gown (p = 0.140).
0.5 lm
5 lm
24
14
326
48
0
143
80
11
138
28
4
35
20
0
41
26
1
17 36
8 23
2 3
29
13
3
4
4
0
27
20
4
84
25
7
5
0
0
0
0
0
8
1
0
5
3
0
3
2
0
4
2
0
Hood
Toga
1
Six readings were taken for each of the following three setups in a randomised order: (1) Gown: surgeon with surgical gown and face mask. (2) Hood: surgeon with surgical gown and hood, maximum fan speed. (3) Toga: surgeon with toga, maximum fan speed
Discussion Surgeon-originated particles are a major source of airborne contaminants in operating theatres. Ritter has described the number of colony-forming units rising significantly from 13 units/ft3 in an empty operating theatre to greater than 400 units/ft3 during actual surgery [2]. The particle counts in the presented experiment represent the degree to which different clothing types prevented surgeon-borne contaminants from being emitted into the vicinity of the surgical site. We have demonstrated a much more significant reduction in airborne particle concentration with the use of the one-piece zippered togas rather than with the two-piece helmet hood and surgical gown ensemble. Previous studies have shown variable results in comparing the efficacies of different theatre attires at reducing airborne contamination. Friberg et al. used a similar air sampling technique in 30 standardised sham operations, and found a comparable reduction with both disposable hood and a self-contained sterile helmet-aspirator system [9]. Conversely, in an experiment including 18 sham hip arthroplasties under LAF, use of a helmet hood with standard gowns led to a fivefold decrease in shed colony-forming units at the surgical site than with standard surgeon’s hood and mask attire [14]. This is broadly similar to our finding of a 3.6fold reduction in contamination (hood v/s gown), but this did not reach statistical significance. In the toga, the
Fig. 2 Raw data plot of particle counts [0.3 lm/ft3 (horizontal axis) for each occlusive factor (vertical axis)
Table 2 Wilcoxon rank-sum tests for equality of means Mean comparison
Test statistic realization
P value
FWER P value*
Hood \ gown
7
0.047
0.140
Toga \ gown
0?
0.002
0.007
Toga \ hood
3.5?
0.012
0.037
FWER familywise error rate * Bonferroni correction applied for multiple comparisons ?
Continuity correction applied for ties in the data
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surgeon-generated particulates have nowhere to go but round the back; in both the hood and gown it can bellow out through the neck. This could possibly explain the difference found in this experiment. Our study was designed to detect potentially microbiologically active squames rather than submicron aerosols. A sensitive instrument was used for particle counting but the particle counters express a count of laser diffractions that correspond to statistically likely particle counts, not a true count of individual particles. A similar particle counter (from the same manufacturer) was used by Stocks et al. in their study of 22 arthroplasties in a non-laminar flow theatre [15]. An impact air sampler adjacent to the particle counter fed air through a tube onto a culture plate, which collected particulates (with viable pathogens) on an agar plate. Particles greater than 3 lm significantly predicted increases in CFUs, and particles greater than 10 lm were extremely significantly predictive. Our study has some limitations. This experimental setup was designed to investigate the effect of surgical attire on airborne contamination from a single source (the scrubbed surgeon) at a predefined level (surgeon’s hands near an imaginary surgical site). In practical terms, intraoperative airborne particulate contaminants would be reduced by different factors acting in concert, e.g. the surgeons wearing togas, using convection-type patient warming [16], minimising door-opening and trying to minimise duration of surgery, etc. In real procedures, the operating surgeon would be expected to move his upper limbs through different positions during the course of a procedure. The spatially neutral position of clasped hands in front was adopted as the minimal denominator to standardise for this in all setups. This experiment showed a significant reduction in surgeon-originated contaminants with the toga compared to both the hood/gown separate ensemble and gowns alone. The results can be extrapolated to arthroplasty surgery, where the scrubbed surgical team consists of at least three persons, and thus a further reduction in contamination around the wound. Acknowledgments We would like to thank Dr Christoper Coldwell, GP trainee at Royal Lancaster Infirmary, for his help with setting up the experiment. This experiment did not incur any running costs. The particle counter was bought by the orthopaedic department. No external funding was received.
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References 1. Edmiston CE Jr, Sinski S, Seabrook GR, Simons D, Goheen MP. Airborne particulates in the OR environment. AORN J. 1999; 69:1169–79. 2. Ritter MA. Operating room environment. Clin Orthop Relat Res. 1999;369:1039. 3. Friberg B. Ultraclean laminar airflow ORs. AORN J. 1998; 67:841–2, 845–51. 4. Department of Health (Gateway Review Estates and Facilities Division). Health Technical Memorandum 03-01: specialised ventilation for healthcare premises. Part A: design and validation. 1st ed. London: The Stationery Office; 2007, p. 54–6. 5. Kearns KA, Witmer D, Makda J, Parvizi J, Jungkind D. Sterility of the personal protection system in total joint arthroplasty. Clin Orthop Relat Res. 2011;469:3065–9. 6. Charnley J. Postoperative infection after total hip replacement with special reference to air contamination in the operating room. Clin Orthop Relat Res. 1972;87:167–87. 7. Franco JA, Baer H, Enneking WF. Airborne contamination in orthopedic surgery. Evaluation of laminar airflow system and aspiration suit. Clin Orthop Relat Res. 1977;122:231–43. 8. Anon. Surgical helmet systems. Health Devices. 1996;25:116–45. 9. Friberg B, Friberg S, Ostensson R, Burman LG. Surgical area contamination—comparable bacterial counts using disposable head and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar air-flow. J Hosp Infect. 2001;47:110–5. 10. Johnson GR, Morawska L, Ristovski ZD, Hargreaves M, Mengersen K, Chao CYH, Wan MP, Li Y, Xie X, Katoshevski D, Corbette S. Modality of human expired aerosol size distributions. J Aerosol Sci. 2011;42:839–51. 11. Reed MR. Re: Does the use of laminar flow and space suits reduce early deep infection? eLetter. J Bone Jt Surg Br. 2011; 93:85–90. 12. Universal Hospital Supplies. Product references UN48100 and UN91220, respectively. http://www.uhs.co.uk/prodfiles/Uhs_ PPE_Brochure.pdf. Accessed 17 September 2012. 13. Particle Measuring Systems. Handheld Particle Counter: HandilazÒ Mini. http://www.pmeasuring.com/particleCounter/air/mobile/ handilazmini. Accessed 17 September 2012. 14. Michla Y, Holliday M, Gould K, Weir DJ, McCaskie AW. The impact on bacterial contamination of hip arthroplasty wounds of personal protection helmet systems. J Bone Jt Surg Br. 2006;88–B:412. 15. Stocks GW, Self SD, Thompson B, Adam XA, O’Connor DP. Predicting bacterial populations based on airborne particulates: a study performed in nonlaminar flow operating rooms during joint arthroplasty surgery. Am J Infect Control. 2010;38:199–204. 16. McGovern PD, Albrecht M, Belani KG, Nachtsheim C, Partington PF, Carluke I, Reed MR. Forced-air warming and ultraclean ventilation do not mix: an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics. J Bone Jt Surg Br. 2011;93:1537–44.
