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Measurement of the concentration and size of aerosol particles and identification of the sources in orthopedic surgeries.

In this study, the measurement of the concentration and size of particles and the identification of their sources were carried out attire orthopedic surgeries. The aerosol concentration and particle size distribution, ranging from 0.3 [micro]m-10 [micro]m, were measured and related to the type of indoor activity. The handling of surgical linen and gowns, handling of the patient, use of electrosurgical apparatus, use of a bone saw, handling of equipment, and cleaning of the room were identified as the most important sources of particles, with each of these activities posing different risks to the health of the patients and workers. The results showed that most of the particles were above 0.5 [micro]m and that there was a strong correlation among all particles of sizes above 1 [micro]m. Particles with diameters in the range of 0.3 [micro]m-0.5 [micro]m had a good correlation only with particles in the ranges" of 0.5 [micro]m-1.0 [micro]m and 1.0 [micro]m-3.0 [micro]m in three of the surgeries analyzed. Findings led to the conclusion that most of the events responsible for generating aerosol particles in an orthopedic surgery room are brief intermittent, and highly variable, thus requiring the use of specific instrumentation for their continuous identification and characterization.

Introduction

Indoor air quality in hospital operating rooms is of great concern for patients and medical personnel. The concentration of aerosol particles inside an operating room can vary considerably depending on the type of activity performed inside the room and the capacity of the air conditioning system to remove them. These particles have basically three origins: (1) those generated inside the room, (2) those coming from the adjacent areas, and (3) those introduced into the operating room through the ventilation system. The air particles inside an operating room can contaminate the wound directly by settling on it or indirectly by contamination of instruments, other surgical materials (gloves, gauze, linen, etc.), and the clothes of the surgical team.

Particles, such as skin (from desquamation), hair, fibers, blood or other body fluids (from aerosolization), etc., due to their size, are easily dispersed by air currents and tend over a time to be deposited at varying rates on surfaces or may remain in suspension for several hours.

Particles that may be shed from the body surface or clothing also represent a potential risk when people are exposed to these agents in an operating room, because these particles can carry biological or pathological agents. With body movement, the bellows or pumping actions of these clothes together with the abrasive effect of the fabrics on the skin surface can detach and disperse skin scales (Clark and Cox 1973). Thus, it is important that the clothing does not itself release particles or fibers into the environment.

Since air touches every surface in a space, airborne particles in contact with contaminated surfaces may be further disturbed mechanically and made airborne again, and the cycle will continue. Therefore, airborne particles that settle onto surfaces can become candidates for the spread of infection. Thus, resuspension can considerably increase the concentration of potential pathogens within an operating room. Any movement of air near the surface where the particles are deposited (floor, equipment, walls) can cause its resuspension. Important factors that may cause the disruption and/or scattering of particles are moving people and equipment, tools used during surgery, air currents originated from air-conditioning systems, and air exchange through doors, etc. (Pereira 2008).

Similarly, cleaning procedures that can increase airborne particles and microorganism levels have important implications for operating rooms (Clark et al. 2009).

The magnitude of the effect of indoor resuspension is not well known, and only limited data are available in the literature. According to Thatcher et al. (2001), the magnitude of the deposition rate within a room is influenced by many factors, including the particle size, shape, and density; surface area, orientation, and roughness; surface-to-air temperature difference; surface particle charge; and air speed.

Owing to the multiplicity of factors involved in the generation of particles in operating rooms, an understanding of the means of transmission of infectious diseases is very important to help prevent the presence of particles that can carry biological or pathological agents. Similarly, the quantification of infection risks from these agents is only possible if the factors that affect their generation are properly understood. A means of achieving this is to quantify the concentration and size of the aerosols present in the hospital environment.

Although a number of studies have been carried out on particle levels during surgery and in hospitals (Scaltriti et al. 2007; Landrin et al. 2005; Nogler et al. 2001; Andersen et al. 1998; Morawska et al. 1998), the contribution made by airborne particles toward the overall burden of nosocomial infection is unclear, and much skepticism surrounds the issue (Beggs 2003; Roberts et al. 2006). One of the possible reasons for this is that many of the studies in this field do not identify or specify individually each source of particle generation in a surgical room. Furthermore, these studies do not analyze the behavior of each source in terms of the size of the particles generated. Consequently, the magnitude of airborne particle sources during operations has not been treated with due importance, and little has been done to control the activities performed in the room in order to decrease the levels of particle agents. Also, the contamination risk associated with airborne particle infection remains largely unknown.

Another important aspect is the difficulty in identifying particle sources, principally when the level of the activity is intense, as occurs inside an operating room. However, a knowledge of these sources and their control is of fundamental importance, particularly in orthopedic surgery due to the smoke and aerosols produced by tools such as electrosurgical apparatus (bone saws, drills, etc.), which can remain in the air for long periods. Such aerosols can be contaminated with potential pathogens and can be spread all over the operating room, contaminating the animate and inanimate environmental surfaces (Nogler et al. 2001). The surgical personnel and the environment are therefore exposed to these agents.

Clearly, the type and dynamics of particles released by these activities requires further and comprehensive investigation in order to gain a proper appreciation of the risks posed to patients and staff.

In this context, in this study, the concentration and size of aerosols present during orthopedic surgery were measured, and the potential sources were identified. Measurements of particle concentration and size were carried out with a portable particle counter, and the activities performed within the operating room were recorded to determine whether there was a relationship between the particles generated and the activities performed in the room.

This study was approved by the ethics committee of Institute of Orthopedics and Traumatology under protocol number 1095/06.

Materials and methods

The measurements were carried out in an operating room with an area of approximately 28 [m.sup.2] (301.7 [ft.sup.2]) and height of 2.7 m (8.8 ft), located in the city of Sao Paulo, Brazil. The air distribution system is of a laminar type (unidirectional) and uses absolute filtration (HEPA) with 30% of outdoor air and 22 air changes per hour (ACH) of total air. During the measurements, the indoor temperature was maintained at 22[degrees]C to 24[degrees]C (71.6[degrees]F to 75.2[degrees]1=) with 40%-50% relative humidity. Figure I shows a basic layout of the operating room.

The particle concentration and size were measured during five orthopedic surgeries. The measurements were carried out using particle counters calibrated by the manufacturer (Met One, Model HHPC-6), which yielded counts of particles in six size ranges: 0.3-0.5 [micro]m, 0.5-1.0 [micro]m, 1.0 3.0 [micro]m, 3.0-5.0 [micro]m, 5.0-10.0 [micro]m, and > 10 [micro]m, with a flow of 0.1 cfm (2.83 l/min).

[FIGURE 1 OMITTED]

The measurement equipment was set on the arm of the surgical light (see Figure 1), above the patient. In this position, the effect of the temperature of the surgical lamps did not affect the measurement through convective currents. According to Dharan and Pittet (2002), with a vertical flow system, heat generation by surgical lamps creates only minor air turbulence.

The measurements taken at this location revealed the influence of the physical activities inside the room on the particle concentration. They also provided a good insight into the nature of the contamination and, hence, contributed to the identification of pollution sources.

For each surgery, the collection of data started with an empty theater, soon after its cleaning and before the patient's entrance, and continued until the patient left the theater. There was a 5-min interval between each collection, and the sampling time was 1 min.

The activities performed in the operating theater were also recorded at 5-min intervals to investigate the relationship between the particles generated and the activities performed from the cleaning of the room until the end of the surgery.

This study did not account for particles from other rooms, because the doors remained closed during the measurements.

To determine whether particles of specific size ranges originate from the same source, the Pearson's correlation coefficient of (r) was used to identify correlations between the different particle sizes ranges. This coefficient indicates the degree to which two variables are related. Correlations between different particle sizes can provide an insight into the nature of the particles and may contribute to the identification of particle sources.

In order to show the influence of the sources on the concentration of particles with the different diameters, the parameter C/Cm was used, which is the ratio between the concentration at a certain time and the average of the concentration for the whole surgical operation.

Results

Figures 2 to 6 show the variations in the particle concentrations over time for surgeries 1, 2, 3, 4, and 5, respectively. The data are presented for the six particle size ranges (0.3-0.5 [micro]m, 0.5-1 [micro]m, 1-3 [micro]m, 3 5 [micro]m, 5-10 [micro]m, and >10 [micro]m). The occurrence and duration of key activities (e.g., the placing of bandages) are also indicated. To facilitate an easier understanding of the results in these figures, the activities that can lead to the generation of particles in surgical rooms are summarized in Table 1.

[FIGURE 2 OMITTED]

A summary of the indoor particle concentrations for the various diameters is presented in Tables 2-6. It can be seen that for all surgeries analyzed, the highest concentration of particles was in the size range of 0.3 [micro]m-0.5 [micro]m and the lowest was > 10.0 [micro]m. It can also be seen that, in all cases, as the size of the particles increased, their concentration decreased.

Table 2 shows that in surgery 1, particles between 0.3 [micro]m-0.5 [micro]m ranged from 9.52 to 31.75 particles/[cm.sup.3] (269,540 to 898,920 particles/[ft.sup.3]) and with an average of 16.49 particles/[cm.sup.3] (466,870 particles/[ft.sup.3]). Particles > 10 [micro]m ranged from 0.00 to 0.04 particles/[cm.sup.3] (0 to 1130 particles/[ft.sup.3]), with an average of 0.02 particles/[cm.sup.3] (570 particles/[ft.sup.3]). Thus, the concentration of particles in the size range of 0.3 [micro]m-0.5 [micro]m was 824 times higher than the concentration > 10 [micro]m. Particles in the range of 0.5 [micro]m 1.0 [micro]m had an average concentration of 2.64 particles/[cm.sup.3] (74,740 particles/[ft.sup.3]), which is approximately three times higher than that in the range of 1.0 [micro]m-3.0 [micro]m (0.89 particles/[cm.sup.3] [25,200 particles/[ft.sup.3]]). For the particle size range of 3.0 [micro]m-5.0 [micro]m, the average concentration was 0.20 particles/[cm.sup.3] (5660 particles/[ft.sup.3]), which is 2.5 times higher than the concentration of particles in the range of 5.0 [micro]m-10.0 [micro]m (0.08 particles/[cm.sup.3] [2260 particles/[ft.sup.3]]).

[FIGURE 3 OMITTED]

Figure 2 shows that before the patient entered the room the particle concentration was considerably affected by the process of cleaning (a), especially for the particles between 0.3 [micro]m and 0.5 [micro]m and 0.5 [micro]m and 1.0 [micro]m, which had the highest fluctuation. In the range of 0.3 [micro]m-0.5 [micro]m, particle concentrations reached approximately twice the average. It can also be seen clearly that during the surgery preparation, the cleaning of the skin and patient movement (b) caused an increase in particle concentrations, which affects mainly the particle sizes above 1 [micro]m. Also, during the preparation period, the placement of surgical linen and gowns (c) was also identified as a significant source of particles within the room. During these activities, particlse of 5.0 [micro]m-10.0 [micro]m and > 10.0 [micro]m reached the highest peaks. During the surgery, it was observed that the concentration of particles above 0.5 [micro]m decreased. At the end of the surgery, an intense peak occurred, due to the placing of bandages (e) and removal of the surgical linen and gowns (c). It is also important to highlight that, after the process of cleaning, the particle size range of 0.3 [micro]m-0.5 [micro]m was almost unaffected by the activities carried out inside the room.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

In surgery 2 (Table 3), the concentration of particles of 0.3 [micro]m-0.5 [micro]m ranged from 6.67 to 66.52 particles/[cm.sup.3] (188,840 to 1,883,350 particles/[ft.sup.3]), with an average of 20.49 particles/[cm.sup.3] (580,120 particles/[ft.sup.3]), and particles > 10.0 [micro]m ranged from 0.00 to 0.17 particles/[cm.sup.3] (0 to 4,810 particles/[ft.sup.3]), with an average of 0.03 particles/[cm.sup.3] (850 particles/[ft.sup.3]). The concentration of particles in the range of 0.3 [micro]m-0.5 [micro]m was 683 times higher than that of particle size > 10 [micro]m. The particle size range of 0.5 [micro]m-1.0 [micro]m had an average concentration of 4.55 particles/[cm.sup.3] (128,820 particles/[ft.sup.3]), which is approximately 4.5 times lower than 0.3 [micro]m-0.5 [micro]m and 2.5 times higher than 1.0 [micro]m-3.0 [micro]m (1.79 particles/[cm.sup.3] [50,680 particles/[ft.sup.3]]). For particles of 5.0 [micro]m-10.0 [micro]m, the average concentration was 0.16 particles/[cm.sup.3] (4530 particles/[ft.sup.3]). On comparing this concentration with that for particles of 3.0 [micro]m-5.0 [micro]m, it is also approximately 2.5 times higher.

Figure 3 shows that initially there was a small peak generated by the cleaning of the room (a), which affects mainly particles size 0.3 [micro]m-0.5 [micro]m. It can also be seen clearly that during the period of preparation for surgery 2, three significant sources of particles were identified in the room. The first peak was due to the removal of blankets (f) used for transporting the patient to the room, the second peak was due to the moving of the patient (g) by the surgery team, and the third was due to the placement of surgical linen and gowns (c). During the surgery, a high peak was generated by the intense use of electrosurgical apparatus (h), which can produce a cloud of smoke, mostly of particles ranging between 0.5 [micro]m and 1.0 [micro]m and 1.0 [micro]m and 3.0 [micro]m. Finally, at the end of the surgery, the increase in particle concentration was due to the removal of the surgical linen (c).

Table 4 summarizes the results for surgery 3. It can be seen that particles of 0.3 [micro]m-0.5 [micro]m ranged from 2.99 to 25.05 particles/[cm.sup.3] (84,660 to 709,230 particles/[ft.sup.3]), with an average of 10.49 particles/[cm.sup.3] (297,000 particles/[ft.sup.3]), and particles >10 [micro]m ranged from 0.01 to 0.48 particles/[cm.sup.3] (280 to 13,590 particles/[ft.sup.3]), with an average of 0.13 particles/[cm.sup.3] (3680 particles/[ft.sup.3]). In comparative terms, the concentration of particles 0.3 [micro]m-0.5 [micro]m was 80 times higher than that of particles > 10.0 [micro]m. In the case of particles of 0.5 [micro]m-l.0 [micro]m, the average concentration was 3.09 particles/[cm.sup.3] (87,490 particles/[ft.sup.3]), which was approximately three times lower than that of particle size 0.3 [micro]m-0.5 [micro]m and twice that of 1.0 [micro]m-3.0 [micro]m (1.44 particles/[cm.sup.3] [40,770 particles/[ft.sup.3]]). For particles of 5.0 [micro]m-10.0 [micro]m, the average concentration was 0.35 particles/[cm.sup.3] (9,910 particles/[ft.sup.3]), that is, approximately 17 times higher than particles of 3.0 [micro]m-5.0 [micro]m.

Figure 4 shows that initially there was a small increase in the concentration of particles of 0.3 [micro]m-0.5 [micro]m generated by the cleaning the room (a). It can also be seen that a main particle source during surgery 3 was the moving of equipment (i). The major impact caused by this source was in the size ranges above 1 [micro]m, but in the first peak, the main variation occurred in the range between 0.3 [micro]m-1.0 [micro]m. In this surgery, it was observed that the major source was the placement and removal of surgical linen and gowns during the preparation and after surgery.

In the case of surgery 4, Table 5 shows that particles of 0.3 [micro]m-0.5 [micro]m ranged from 5.49 to 30.24 particles/[cm.sup.3] (155,440 to 856,170 particles/[ft.sup.3]), with an average of 9.99 particles/[cm.sup.3] (282,840 particles/[ft.sup.3]), and particles > 10.0 [micro]m ranged from 0.00 to 0.13 particles/[cm.sup.3] (0 to 3,680 particles/[ft.sup.3]), with an average of 0.04 particles/[cm.sup.3] (1130 particles/[ft.sup.3]). The concentration of particles in the range of 0.3 [micro]m-0.5 [micro]m was 250 times higher than for particles > 10.0 [micro]m. Particles of 0.5 [micro]m-1.0 [micro]m had an average concentration of 3.46 particles/[cm.sup.3] (97,960 particles/[ft.sup.3]), which was approximately three times lower than those of 0.3 [micro]m-0.5 [micro]m and twice that of 1.0 [micro]m-3.0 [micro]m (1.59 particles/[cm.sup.3] [45,020 particles/[ft.sup.3]]). For particles of 3.0 [micro]m-5.0 [micro]m, the average concentration was 0.45 particles/[cm.sup.3] (12,740 particles/[ft.sup.3]), that is, approximately 2.5 times higher than 5.0 [micro]m-10.0 [micro]m (0.17 particles/[cm.sup.3] [4810 particles/[ft.sup.3]]).

It can be seen in Figure 5 that the indoor concentration was initially affected by the cleaning of the room (a) and that particles in the ranges of 0.3 [micro]m-0.5 [micro]m and 0.5 [micro]m-1.0 [micro]m had the highest fluctuations. In the range of 0.3 [micro]m-0.5 [micro]m, particle concentrations reached approximately a value that was twice the average. During the preparation for the surgery, the first source was the movement of equipment (i), and the others were the movement of the surgical linen (c), movement of the patient (g), and removal of bandages (1). All particle size ranges were affected by these sources. During the surgery, a sequence of peaks of different particle sizes was observed due to the intense movement of the surgical team (m) and to the movement of equipment (i). Finally, at the end of the surgery, an increase in particle concentration occurred with the removal of the surgical linen and gowns (c).

Finally, in surgery 5, Table 6 shows that the concentration of particles of 0.3 [micro]m-05 [micro]m ranged from 0.02 to 2.50 particles/[cm.sup.3] (570 to 70,780 particles/[ft.sup.3]), with an average of 1.06 particles/[cm.sup.3] (30,010 particles/[ft.sup.3]), and particles > 10 [micro]m ranged from 0.00 to 0.03 particles/[cm.sup.3] (0 to 850 particles/[ft.sup.3]), with an average of 0.01 particles/[cm.sup.3] (280 particles/[ft.sup.3]). The concentration of particles of 0.3 [micro]m-0.5 [micro]m was 106 times higher than for particles > 10 [micro]m. In the case of particles in the ranges of 0.5 [micro]m-1.0 [micro]m and 1.0 [micro]m-3.0 [micro]m, the average concentrations were 0.30 particles/[cm.sup.3] (8490 particles/[ft.sup.3]) and 0.16 particles/[cm.sup.3] (4530 particles/[ft.sup.3]), respectively; that is, the concentration of the former was twice as high as the latter. For particles of 3.0 [micro]m-5.0 [micro]m, the average concentration was 0.04 particles/[cm.sup.3] (1130 particles/[ft.sup.3]), approximately two times higher than particles of 5.0 [micro]m-10.0 [micro]m (0.02 particles/[cm.sup.3] [570 particles/[ft.sup.3]]).

Figure 6 illustrates that during surgery 5, the cleaning of the room (a) had little effect on the particle concentration inside the room. During the preparation for surgery, the first peak occurred due to the cleaning/moving of the patient (b) and the removal of bandages (l). The second peak was due to the moving of surgical linen (c) and of equipment (i). During the surgery, the use of a bone saw (j) was an important source of particles. It is important to highlight that the particle concentration remained high throughout the period when the saw was used. Finally, at the end of the surgery, the increase in particle concentration was associated with the removal of surgical linen (c) and the placing of bandages (e). It can also be noted that in this surgery, all sources observed after the cleaning of the room affected all particle size.

Figure 7 shows the correlation between all particle sizes for the five surgeries. It is evident that there is a strong correlation between all particle sizes above 1.0 [micro]m-3.0 [micro]m. Particle size 0.3 [micro]m-0.5 [micro]m only had a good correlation with particle size ranges of 0.5 [micro]m-l.0 [micro]m and 1.0 [micro]m-3.0 [micro]m in surgeries 2, 4, and 5. In the other ranges, there was either no correlation or the correlation was weak. In most cases, the particles size 0.5 [micro]m-1.0 [micro]m had a strong correlation with the other sizes. It can also be seen that in surgery 5, all particle size ranges had a strong correlation. This was probably due to the influence of the bone saw that generated a great amount of particles in all size ranges during the whole period in which it was used.

Analysis of results

The results showed that the concentration of particles varied considerably depending on the type of activity performed inside the room. A total of 32 events were identified as being associated with elevated particle concentrations, and these events were classified into 13 different types of indoor activities. The data collected showed that the sources of particles were expressed at different times and were usually characterized by a peak of a certain size range depending on the particle source. Some of these sources were specifically expressed in certain types of surgeries, while others are present in all of them, such as the placement and removal of surgical linen and gowns.

According to the data collected, most of the particles inside the room were generated by events that mechanically disturbed the particles that were deposited on different surfaces, which regenerates airborne contaminants. It is important to note that if these particles have micro-organisms attached to them or are bacterial, fungal, or viral agents, these can spread over the operating room, contaminate the environment, and pose a health risk to all personnel present during the surgical procedure, as was suggested by Nogler et al. (2001).

[FIGURE 7 OMITTED]

It was observed that particles above 0.5 [micro]m-1.0 [micro]m had much greater peaks and much more variation than those below 0.5 [micro]m-l.0 [micro]m. This suggests that most events inside the room generate particles above 0.5 [micro]m-l.0 [micro]m.

The results also clearly show that in most cases, the concentration of particles in the ranges of 0.3 [micro]m-0.5 [micro]m are completely independent of the particles above 0.5 [micro]m-1.0 [micro]m, suggesting that they can come from of different sources, as indicated by the correlation coefficient.

The influence of each activity on the generation of particles will now be described.

Cleaning the room (a)

It was verified that the process of cleaning the room was an important source of particle generation (Figures 2-6). This activity appeared to be mostly associated with the production of particles in the ranges of 0.3 [micro]m-0.5 [micro]m and 0.5 [micro]m-l.0 [micro]m. A large proportion of particles generated during the cleaning of the room were produced by the great disturbances caused by the intense movement of people, equipment, and material for cleaning, etc. The record of the activities performed in the surgical room in this study showed that there are differences in the cleaning procedures associated with each surgery. Depending on factors, such as the level of dirtiness of the room, the amount of surgical linen and gowns, and the equipment used, the concentration of particles generated in each diameter range can vary. Studies carried out by Clark et al. (1985) showed an increase in airborne bacteria during cleaning. According to Hambraeus et al. (1978), the floor bacteria contributed up to 15% of the flora of operating room air. However, in a study published by Morawska et al. (1998), it was concluded from chamber measurements that cleaning procedures using detergents do not contribute to airborne particulates in the hospital environment.

It is also important to note that some of the particles generated during the cleaning process can remain suspended. As stated by Andersen et al. (1998), although theater cleaning may decrease the microorganisms present on surfaces, this is not necessarily the case in terms of microorganisms present in the air.

Cleaning/moving the patient (b and g)

Cleaning/moving the patient (Figure 2) before and during the surgical procedure was also identified as a significant source of particles within the room. The particles generated by this source were > 1.0 [micro]m. This source must be taken into account mainly because the patient may be a potential carrier of Staphylococcus aureus and other microorganisms that can be released into the operating room. According to Kluytmans et al. (1995), the presence of S. aureus in surgical patients is a significant risk factor for surgical site infections.

Moving surgical linen and gowns (c)

It was also shown that the movement of linen and gowns (Figures 2-6) before, during, and after the surgeries was an important source of particle generation. This is an activity carried out in most of the surgeries, and the particles generated by these sources can be a potentially serious problem. Especially during the surgery, the handling of these materials tends to recirculate the particles deposited on their surfaces, which were generated during the surgery by various sources in the room. No studies were found in the literature on the potential contamination of wounds by this practice in the operating room. Thus, there is a need for further investigation regarding this practice to verify the potential risk of infection.

Placing and removal of bandages (e and l)

It was also observed that the removal of bandages (Figures 2, 5, and 6) caused considerable generation of particles. It is important to highlight that normally, the surfaces of these materials are dirty and contaminated because they were not sterilized prior to entering the room, and hence, they are a potential risk of infection. Once again, no studies were found in the literature on the contamination of wounds by this practice in the operating room, indicating that further investigation of this practice is required to verify the potential risk of infection.

Removal of blankets (f)

Similarly, the particles that are generated by objects, such as blankets (Figure 3), commonly used in transporting the patient to the room can be a great risk of infection, because this kind of material is not sterile. According to the Newcastle Regional Hospital Board Working Party (NRHBWP 1962), blankets have long been suspected of playing an important part in hospital infection. Pathogenic microorganisms that are accumulated on the surface can be dispersed in the air and contaminate the wound. Desquamated skin cells are likely to be the primary particle type resuspended.

This assumption is based on the knowledge that blankets are rarely washed after use by a long succession of patients and that they often harbor enormous numbers of bacteria, including the troublesome S. aureus (NRHBWP 1962).

It is important to note that due to a lack of recent studies in this area, principally in the operating room, there is a need for further investigation into this practice to verify the potential risk of infection.

Use of electrosurgical apparatus (h)

Particles generated by the use of electrosurgical apparatus (Figure 3) represent an important source of air contamination. More importantly, studies show that these small particles, gases, and vapors may contain potentially harmful contaminants, such as DNA viruses, aerosols, cell fragments, and other gaseous hydrocarbons, that can be inhaled by the occupants of the operating room (Wenig et al. 1993; Alp et al. 2006; Bruske-Hohlfeld et al. 2008).

Moving of equipment (i)

The results also revealed that the entrance, exit, and movement of equipment within the room (Figures 4, 5, and 6), such as video players, X-ray machines, image intensifiers, etc., were important sources of particle generation during the surgery. As suggested by Yeh et al. (1995) and Seal and Clark (1990), it is recognized that most of these particles are produced by the resuspension process, caused by intense air disturbance due to the movement of equipment and people close to contaminated surfaces.

Use of bone saw (j)

During surgery 5, the use of a bone saw was an important source of particles. It is important to highlight that the particle concentration remained high throughout the period in which the saw was used. This event generated particles in all of the size ranges that were considered. Nogler et al. (2001) showed that the use of a high-speed cutting device during surgery produces an aerosol cloud that can spread over the whole operating room (within an extension of 5-7 [micro]m) and contaminate it, as well as all of the mobile equipment and all personnel present.

Movement of the surgical team (m)

People walking around can re-disperse dust particles from the floor and at the same time can shed skin flakes from the body. The surgical team (Figure 5) is the largest source of the generation of particles inside an operating room (Yeh et al. 1995). In most of the surgeries analyzed, it was shown that during the preparation for the surgical procedure, where the activity level of the surgical team was most intense, there was a progressive increase in the concentration of particles. As the results show, the particles generated by people during this activity were mostly above 5 [micro]m. This evidence is of particular interest, because, as previously mentioned, skin flakes generated by the surgical team are the major sources of this kind of contamination. Skin squamae are relatively large particles (4 [micro]m-25 [micro]m), and once released or resuspended, they can transport staphylococci (Roberts et al. 2006). In addition, particles of this size offer a greater possibility of serving as a transport medium for pathogenic agents. According to Liu and Moser (2002), the size of the particles that contain bacteria in an operating room is usually in the range of 0.5 to 10 micrometers.

Conclusions

Particle concentrations in different size ranges were measured during five orthopedic surgeries in the operating room of a large hospital in the city of Sao Paulo, Brazil. For each surgery analyzed, the measurements and recording of activities began before the patient entered in the room, right after the cleaning of the room when it was still empty, and finished soon after the departure of the patient.

It is envisioned that the data presented herein will contribute to the overall knowledge of the relationship between surgical procedures and the particles they generate and to the exposure of the surgical team and the patients to aerosols in orthopedic operating rooms.

The results were obtained using an optical particle counter, technology that has some limitations, such as the possibility of interferences due to coincidence losses in particle counts at high particle concentrations. Another limitation of this technology is that it measures only particle concentration and size, without characterizing the type of particles measured, and neglects the effect of the particle shape.

Although the study developed by Seal and Clark (1990) identified a correlation between viable and airborne particle counting by portable particle counters, further studies employing different methodologies, such as the Andersen cascade impactor, are needed to provide information, such as biological composition, and to confirm the infection risk.

Another important limitation of this work is that surgical activities frequently change, with different tools being used and surgeons or nurses changing their location within the room from time to time. Thus, the particle concentration and size vary widely from procedure to procedure and over time during the same procedure. As a result, a single air sample at a single location at a discrete point in time may have limited value. Hence, the results obtained in this work cannot be considered as representative of the behavior of particles in the room as a whole, but they can be indicative of the situation in the area close to the site of surgery. Although monitoring of the full environment requires multiple particle counters, which adds considerable expense, this should be considered in future studies.

Acknowledgment

Authors Marcelo Luiz Pereira and Arlindo Tribess wish to acknowledge CNPq (Brazilian National Research Council) for the doctoral scholarship and research grant, respectively.

References

Alp, E., D. Biji, R.P. Bleichrodt, A. Hansson, and A. Voss. 2006. Surgical smoke and infection control. Journal of Hospital Infection 62:1-5.

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Clark, R.P., P.J. Reed, D.V. Seal, and M.L. Stephenson. 1985. Ventilation conditions and air-borne bacteria and particles in operating theatres: Proposed safe economies. Journal of Hygiene 95:325-35.

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Landrin, A., A. Bisseryb, and G. Kacc. 2005. Monitoring air sampling in operating theatres: Can particle counting replace microbiological sampling? Journal of Hospital Injection 61:27-9.

Liu, Y., and A. Moser. 2002. Airborne particle concentration control for an operating room. Proceedings of Room Vent 2002 (8th International Conference on Air Distribution in Rooms), September 8-11, Copenhagen.

Morawska, L., M. Jamriska, and P. Francis. 1998. Particulate matter in the hospital environment. Indoor Air 8:285-94.

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Pereira, M.L. 2008. Measurement, prediction and analysis of airborne particles in surgical rooms. Doctoral thesis, Polytechnic School of the University of Sao Paulo, Sao Paulo, Brazil. (in Portuguese).

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Scaltriti, S., S. Cencettib, S. Rovestia, I. Marchesia, A. Bargellinia, and P. Borellaa. 2007. Risk factors for particulate and microbial contamination of air in operating theatres. Journal of Hospital Injection 66(4):320-6.

Seal, D.V., and R.P. Clark. 1990. Electronic particle counting for evaluating the quality of ultra clean air in operating theatres: A potential basis for standards? Journal of Applied Bacteriology 68:225-30.

Thatcher, T.L., A.C.K. Lai, R. Moreno-Jackson, R.G. Sextro, and W.W. Nazaroff. 2001. Effects of room furnishings and air speed on particle deposition rates indoors. Atmospheric Environment 36:1811-9.

Wenig, B.L., Stenson, K.M., Wenig, B.M., and Tracey, D. 1993. Effects of plume produced by the Nd:YAG laser and electrocautery on the respiratory system. Lasers in Surgery and Medicine 13:242-5.

Yeh, H.C., R.S. Turner, R.K. Jones, B.A. Muggenburg, D.L. Lundgren, and J.P. Smith. 1995. Characterization of aerosols produced during surgical procedures in hospitals. Aerosol Science and Technology 22:151-61.

Marcelo Luiz Pereira, (1), * Rogerio Vilain, (1) Tomaz Puga Leivas, (2) and Arlindo Tribess (3)

(1) Department of Refrigeration and Air Conditioning, Federal Institute of Education, Science and Technology of Santa Catarina, Sdo Jose, Brazil

(2) Institute of Orthopedics and Traumatology, University of Sao Paulo, Sao Paulo, Brazil

(3) Department of Mechanical Engineering, University of Sao Paulo, Sao Paulo, Brazil

* Corresponding author e-mail: marcelo.pereira@ifsc.edu.br

Received March 10, 2011; accepted March 8, 2012

Mareelo Luiz Pereira, DSc, is Associate Professor. Rogerio Vilain, DSc, is Associate Professor. Tomaz Puga Leivas, DSc, is Chief Engineer of the Biomechanics Laboratory. Arlindo Tribess, DSc, is Associate Professor.

DOI: 10.1080/10789669.2012.705572
Table 1. Summary of the activities that can generate particles in
surgical rooms indicated in Figures 2-6.

   Process                       Description

a  Cleaning the room             Washing and scrubbing the floor,
                                 equipment, etc., before each surgery

b  Cleaning/moving the patient   Preparing the patient for surgery,
                                 performing activities (such as
                                 cleaning the area to be operated on),
                                 and movement of the patient for
                                 application of the anesthetic

c  Moving the surgical linen     Moving of surgical linen refers to
   and gowns                     the placement or arrangement of the
                                 sterile cotton sheet over the
                                 patient, which can occur before,
                                 during, or after surgery; moving
                                 gowns refers to the putting on of the
                                 surgical team gowns before surgery
                                 and the removal of the gowns at the
                                 end

d  Unidentified                  Activity unidentified

e  Placing of bandages           Redressing the wound with new
                                 bandages after surgery

f  Removal of blankets           Removing the blankets used to cover
                                 the patient during transport from the
                                 ward to the operating room; commonly
                                 used principally for elderly patients
                                 to keep them warm

g  Moving the patient            Movement required to place the
                                 patient in the right position for
                                 surgery

h  Use of electrosurgical        Using an electrical scalpel during
   apparatus                     surgery

i  Moving of equipment           Entry, movement inside the room, or
                                 removal of auxiliary equipment, such
                                 as an X-ray machine used during
                                 surgery

j  Use of bone saw               An instrument used frequently during
                                 orthopedic surgeries

1  Removal of bandages           Removing old bandages before surgery

m  Movement of the surgical      All movements of the surgical team
   team                          during surgery

Table 2. Summary of the particle concentrations for the various
diameters measured for surgery 1.

                                      Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   0.3-0.5 [micro]m   0.5-1.0 [micro]m

Average                       16.49               2.64
                            (466,870)           (74,740)
Minimum                        9.52               1.15
                            (269,540)           (32,560)
Maximum                       31.75               4.67
                            (898,920)          (132,220)
Standard                       5.19               1.10
  deviation                 (146,940)           (31,140)

                                      Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   1.0-3.0 [micro]m   3.0-5.0 [micro]m

Average                        0.89               0.20
                             (25,200)            (5660)
Minimum                        0.25               0.05
                              (7080)            (1,420)
Maximum                        1.98               0.52
                             (56,060)           (14,720)
Standard                       0.47               0.12
  deviation                  (13,300)            (3400)

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   5.0-10.0 [micro]m   > 10.0 [micro]m

Average                        0.08               0.02
                              (2260)              (570)
Minimum                        0.02                 0
                               (570)               (0)
Maximum                        0.21               0.04
                              (5,950)            (1130)
Standard                       0.05               0.02
  deviation                   (1420)              (570)

Table 3. Summary of the particle concentrations for the various
diameters measured for surgery 2.

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   0.3-0.5 [micro]m   0.5-1.0 [micro]m

Average                       20.49               4.55
                            (580,120)          (128,820)
Minimum                        6.67               0.51
                            (188,840)           (14,440)
Maximum                       66.52              25.78
                           (1,883,350)         (729,890)
Standard                      11.10               3.89
  deviation                 (314,270)          (110,140)

                                      Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   1.0-3.0 [micro]m   3.0-5.0 [micro]m

Average                        1.79               0.41
                             (50,680)           (11,610)
Minimum                        0.09               0.01
                              (2550)             (280)
Maximum                        9.99               1.81
                            (283,840)           (51,250)
Standard                       1.56               0.33
  deviation                  (44,170)            (9340)

                                        Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   5.0-10.0 [micro]m   > 10.0 [micro]m

Average                        0.16               0.03
                              (4530)              (850)
Minimum                        0.00               0.00
                                (0)                (0)
Maximum                        0.68               0.17
                             (19,250)            (4,810)
Standard                       0.13               0.03
  deviation                   (3680)              (850)

Table 4. Summary of the particle concentrations for b the various
diameters measured for surgery 3.

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   0.3-0.5 [micro]m   0.5-1.0 [micro]m

Average                       10.49               3.09
                            (297,000)           (87,490)
Minimum                        2.99               1.02
                             (84,650)           (28,880)
Maximum                       25.05               7.71
                            (709,230)          (218,290)
Standard                       2.99               1.46
  deviation                  (84,650)           (41,340)

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   1.0-3.0 [micro]m   3.0-5.0 [micro]m

Average                        1.44               0.02
                             (40,770)            (570)
Minimum                        0.19               0.00
                              (5380)              (0)
Maximum                        4.25               0.09
                            (120,330)            (2550)
Standard                       0.83               0.02
  deviation                  (23,500)            (570)

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   5.0-10.0 [micro]m   > 10.0 [micro]m

Average                        0.35               0.13
                              (9910)             (3680)
Minimum                        0.02               0.01
                               (570)              (280)
Maximum                        1.22               0.48
                             (34,540)           (13,590)
Standard                       0.21               0.08
  deviation                   (5950)             (2270)

Table 5. Summary of the particle concentrations for the various
diameters measured for surgery 4.

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   0.3-0.5 [micro]m   0.5-1.0 [micro]m

Average                        9.99               3.46
                            (282,840)           (97,960)
Minimum                        5.49               0.58
                            (155,440)           (16,420)
Maximum                       30.24              10.59
                            (856,170)          (299,830)
Standard                       5.01               2.26
  deviation                 (141,850)           (63,990)

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   1.0-3.0 [micro]m   3.0-5.0 [micro]m

Average                        1.59               0.45
                             (45,020)           (12,740)
Minimum                        0.03               0.05
                              (850)              (1420)
Maximum                        5.85               1.76
                            (165,630)           (49,830)
Standard                       1.26               0.36
  deviation                  (35,670)           (10,190)

                                        Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   5.0-10.0 [micro]m   > 10.0 [micro]m

Average                        0.17               0.04
                              (4810)             (1130)
Minimum                        0.01               0.00
                               (280)               (0)
Maximum                        0.70               0.13
                             (19,820)            (3680)
Standard                       0.15               0.03
  deviation                   (4250)              (850)

Table 6. Summary of the particle concentrations for the various
diameters measured for surgery 5.

                                      Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   0.3-0.5 [micro]m   0.5-1.0 [micro]m

Average                        1.06               0.30
                             (30,010)            (8490)
Minimum                        0.02               0.00
                              (570)               (0)
Maximum                        2.50               0.77
                             (70,780)           (21,800)
Standard                       0.82               0.26
  deviation                  (23,220)            (7360)

                                      Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   1.0-3.0 [micro]m   3.0-5.0 [micro]m

Average                        0.16               0.04
                              (4530)             (1130)
Minimum                        0.00               0.00
                               (0)                (0)
Maximum                        0.41               0.13
                             (11,610)            (3680)
Standard                       0.13               0.04
  deviation                   (3680)             (1130)

                                       Diameter
Parameter,
particles/[cm.sup.3]
(particles/[ft.sup.3])   5.0-10.0 [micro]m   > 10.0 [micro]m

Average                        0.02               0.01
                               (570)              (280)
Minimum                        0.00               0.00
                                (0)                (0)
Maximum                        0.06               0.03
                              (1700)              (850)
Standard                       0.01               0.01
  deviation                    (280)              (280)
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Author:Pereira, Marcelo Luiz; Vilain, Rogerio; Leivas, Tomaz Puga; Tribess, Arlindo
Publication:HVAC & R Research
Article Type:Report
Geographic Code:3BRAZ
Date:Aug 1, 2012
Words:7769
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