Surgical site infection (SSI) is associated with a variety of factors, and operating room air quality is a major concern for surgeons and sensory control personnel. As a classical disinfection method, UV light disinfection is used more often in the disinfection of general operating rooms at all levels of hospitals because of its ease of operation, relatively low price, and low contamination.
Traditional UV lamp irradiation requires an unoccupied environment and produces ozone that is harmful to humans; in recent years, a new type of upper space UV disinfector has emerged that can achieve human-machine coexistence and produces less ozone. At present, there are few studies on the disinfection efficiency of the upper space UV disinfector in the operating room in China, and this test is intended to explore the disinfection effect of the upper-level UV sterilizer in the operating room of a hospital.
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1 Object and method
1) Object of the study
One general interventional operating room in the hospital with an operating room area of 30 m² was selected and was observed before the installation of the upper level-flush UV sterilizer and recorded as the control group, and the same observation was performed after the installation and use of the upper level-flush UV sterilizer and recorded as the test group. The observations were conducted from August 12-16, 2019 and August 19-23, 2019, respectively, and focused on recording the number of medical personnel in the room and the number of medical personnel in the space during minimally invasive interventional procedures (e.g., radiofrequency thermocoagulation of the trigeminal meniscus, minimally invasive ablation of the intervertebral disc, and intervertebral foraminoscopic discotomy and aspiration) performed by physicians in the operating room. Ozone concentration in the room during interventional procedures (e.g., trigeminal hemi-radial coagulation, minimally invasive intervertebral disc ablation, and intervertebral laparoscopy) and air sampling in the operating room.
2) Test materials
The upper level flat-jet UV sterilizer was installed on the side wall 2.2 m above the floor of the operating room according to the instructions; the circulating air volume was 800 m³/h in the circulating air disinfection mode, and the circulating air was turned off in the upper level disinfection mode. A 9 cm diameter plain nutrient agar plate was used for air sampling. An ozone detector was used to measure the ozone concentration in the operating room.
3）Sampling method
Sampling and testing methods refer to GB 15982-2012 “Hospital Disinfection Health Standards“. The air in the operating room is sampled by the plate sedimentation method, with a total of 5 points at 4 corners and the center, and the 4 corners are 1 m from the wall. 1 m from the ground for each sampling point, the lid of the dish is opened and placed next to the dish, and the dish is covered after 15 min of exposure, and then sent to the 37℃ thermostat for 48 h; the number of bacterial colonies in each dish is calculated after the incubation and the total number of bacterial colonies ≤4 cfu/( 15min- The total number of bacterial colonies ≤4 cfu/( 15 min- dish) was qualified.
4）Measure ozone concentration
Measure the ozone concentration in the operating room with ozone detector according to the instruction; refer to GB/T 18202-2000 “Health Standard for Ozone in Indoor Air“, ozone concentration ≤ 0.1 mg/(m³ -h) is qualified. -The ozone concentration is qualified.
5) Test procedure
① During the observation period of the test group and the control group, both groups were cleaned at the beginning of the test, and after 15 min of standing, the first sampling was performed in both groups.
② After the first sampling, the test group started circulating wind UV light disinfection; the control group did not have UV light disinfection; after 15 min, the test group performed the second sampling, and the control group did not sample.
③ After the second sampling, the test group started to perform ultraviolet disinfection on the upper level while the medical staff started to work, and the third, fourth and fifth sampling was performed 1, 2, and 5 h later, respectively; the control group was sampled at the same time.
④ The number of people in the operating room at the time of sampling and the ozone concentration were recorded. For details, see the experimental design procedure, which was repeated for 4 days for the experimental group and 5 days for the control group.
6) Cleaning and disinfection
The operating room was routinely cleaned and disinfected between consecutive surgeries and at the end of the day’s surgery.
7) Statistical analysis
Graphad Prism 8 and SPSS 19.0 software were used for statistical analysis of the data. Statistical analysis was performed using Graphad Prism 8 and SPSS 19.0 software. A t-test was used to compare the measurement data between the two groups. The t-test was used to compare the measurement data between the two groups, and the χ2 test was used to compare the rates. The degree of correlation was expressed by spearman’s correlation coefficient. The statistical tests were all two-sided probability tests, and P < 0.05 was considered a statistically significant difference. The difference was statistically significant.
2 Results
1) Effect of UV light on the number of air colonies in the operating room
The sampling time of the first time was recorded as 0 h. The test and control groups were sampled at 0, 0.25, 1, 2, and 5 h. The number of colonies in the air at 0, 0.25, 1, 2, and 5 h are shown in Table 1. The number of colonies in the air at 0, 0.25, 1, 2, and 5 h are shown in Table 1. That is, the number of airborne colonies in the test group and the control group at 1, 2, and 5 h sampling time points is shown in Table 1. There was no statistical difference in the number of colonies in the air between the test and control groups at 1, 2, and 5 h sampling time points. The differences in the total number of colonies between the two groups were not statistically significant. The difference in the total number of colonies between the two groups was not statistically significant (t = 1. 043, P = 0. 304).
Table 1 Number of air colonies in the operating room of the test and control groups at different sampling times
| Group | Sampling Time |
|---|---|
| Experimental group | Group 1 |
2) The effect of the presence or absence of medical personnel in the operating room on the qualification rate of air sampling
The number of medical and nursing staff in the operating room at the 1, 2, and 5 h sampling times for the test and control groups is shown in Table 2. The difference in the number of medical and nursing personnel in the operating room between the test and control groups at the 1, 2, and 5 h sampling time points were not statistically significant; the difference in the total number of medical and nursing personnel between the two groups was not statistically significant (t = 0. 659, P = 0. 516). When there was medical staff in the operating room, all 27 air samples monitored failed; while when there was no medical staff in the operating room, 10 out of 13 samples monitored passed, with a passing rate of 76.92%. The difference was statistically significant (χ2 = 27.69, P < 0.001).
3) Comparison of maximum ozone concentration in the operating room air
The maximum ozone concentration in the operating room air was measured and recorded at 0, 0.25, 1, 2, and 5 h in the test group and at 0, 1, 2, and 5 h in the control group from day 1 to day 5, and the maximum ozone concentration recorded each day is shown in Table 3. It can be seen that the maximum ozone concentrations measured in the two groups were 0.008 mg/(m³-h) and 0.007 mg/(m³-h), which were lower than the national safety limit of 0.1 mg/(m³-h).
Table 2 Number of medical and nursing staff in the operating room at the time of sampling in the test and control groups
| Group | Sampling Time | Number of staff Day 1 | Number of staff Day 2 | Number of staff Day 3 | Number of staff Day 4 | Number of staff Day 5 | Average value |
|---|---|---|---|---|---|---|---|
| Experimental group | 1 | 5 | 5 | 6 | — | 9 | 6.25±1.89 |
| 2 | 4 | 6 | 11 | — | 9 | 7.50±3.11 | |
| 5 | 5 | 6 | 4 | — | 4 | 4.75±0.96 | |
| Control group | 1 | 4 | 11 | 7 | 4 | 6 | 6.40±2.88 |
| 2 | 6 | 5 | 3 | 3 | 4 | 4.20±1.30 | |
| 5 | 4 | 5 | 7 | 8 | 7 | 6.20±1.64 |
Table 3 Comparison of maximum ozone concentration in the air in the operating room between the test and control groups
| Group | Ozone (mg /m³*h) Day 1 | Ozone (mg /m³*h) Day 2 | Ozone (mg /m³*h) Day 3 | Ozone (mg /m³*h) Day 4 | Ozone (mg /m³*h) Day 5 |
|---|---|---|---|---|---|
| Experimental group | 0.006 | 0.007 | 0.008 | — | 0.007 |
| Control group | 0.007 | 0.006 | 0.006 | 0.007 | 0.006 |
4) Relationship between the sampling time of the operating room air and the number of colonies in the air
As shown in Figure 1, as the sampling time of the operating room air in the test group increased from 0 h to 5 h, the number of airborne colonies increased. As the sampling time in the operating room increased from 0 h to 5 h, the number of colonies in the air increased. The correlation coefficient was r = 0. 702, P < 0. 001, and the correlation was statistically significant. The correlation coefficient was r = 0.702, P < 0.001, and the correlation was statistically significant. The correlation coefficient of r = 0. 650, P < 0. 001, was statistically significant. 0.001, the correlation was statistically significant.
5) Relationship between the number of medical and nursing staff and the number of colonies in the operating room air
As shown in Figure 2, with the increase in the number of medical and nursing staff in the operating room of the test group, the number of colonies in the operating room air tended to increase, and the correlation coefficient between the two was r = 0. 851, P < 0. 0001, which was statistically significant; similarly, with the increase in the number of medical and nursing staff in the operating room of the control group, it was also positively correlated with the increase in the number of colonies in the air, r = 0. 797, P < 0. 000 1, which was statistically significant. The correlation was statistically significant.
3 Discussion
According to the working principle of the upper-level flat jet UV light air disinfector, the machine is installed in the upper part of the room and the UV irradiation is located in the upper area, while the lower part is relatively UV-free to ensure that it does not come into contact with indoor personnel. The pathogens in the upper air are killed and lose their ability to reproduce and form colonies Due to the temperature difference indoor air forms slow convection, the lower space air containing pathogens in the lower space continuously enters the upper UV zone, thus The air in the lower space contains pathogens that continuously enter the upper UV zone, thus disinfecting all the air in the room.
In this study, the ozone concentrations in the test and control groups were well below the upper safety limit. Below the upper safety limit, confirming that the machine does not pose a threat to the health of the indoor, confirms that the machine does not pose a health risk to the health care workers in the room. However, there was no statistical difference in the total number of bacteria in the air of the two groups. However, there was no statistical difference in the total number of colonies in the air between the two groups. There was also no statistical difference in the number of colonies in the air between the two groups at 1, 2, and 5 h after the start of surgery. It could not be confirmed that the upper-level flat UV The advantage of the upper-level flat UV light air disinfector in reducing the number of airborne colonies could not be confirmed.
Further analysis revealed that with increasing sampling time, the number of airborne colonies in the test and the control group showed an increasing trend in the number of airborne colonies, with a strong correlation between the two. There was a strong correlation between the two. This indicates that even with the continuous disinfection of the upper level of flat UV radiation, the number of airborne bacteria increased after 5 h. The number of colonies in the air continued to increase after 5 h. When the number of medical personnel in the operating room was used as the variable, the results of the study showed that the number of colonies in the air continued to increase as the number of medical personnel in the operating room increased. Showed that the number of colonies in the air increased with the increase in the number of personnel in the test and control groups. There was a significant correlation between the increase in the number of airborne colonies and the increase in the number of medical personnel in the operating room. It is suggested that controlling the number of personnel is the most effective way to ensure clean air in the operating room. The number of personnel is an important measure to ensure clean air in the operating room. In this study In this study, when air sampling was conducted, the samples monitored in the occupied room In this study, the samples monitored in the occupied room failed to pass the test; while in the unoccupied room, the sample passing rate was 76.92%, which also This indicates the need to control the number of personnel.
The cleanliness of the operating room air has long been considered to be closely related to SSI. Air cleanliness techniques are thought to reduce the number of pathogenic microorganisms in the operating room air, thereby preventing and controlling possible surgical site infections during surgery. The SSI Prevention Guidelines published by the CDC in 1999 suggested that laminar flow technology could be used to reduce SSI, and its updated version in 2017 does not explicitly recommend this technology. A systematic analysis of a large sample of literature also recommends that surgical technique remains a key factor influencing incisional infections. 2019 Chinese Surgical Site Infection Prevention Guidelines recommend bowel preparation, antimicrobial drug use, surgical hand disinfection, maintenance of body temperature, perioperative glycemic control, and antimicrobial-coated sutures, again air-cleaning techniques such as laminar flow were not emphasized.
A Meta-analysis by Bischoff et al. showed that clean air techniques such as laminar flow did not reduce the risk of deep surgical site infections after total hip and total knee arthroplasty compared with general operating room ventilation; nor did they have a beneficial effect on the risk of surgical site infections after abdominal and vascular surgery. In contrast to costly laminar flow systems, a combination of systemic antimicrobial drugs and antimicrobial-coated sutures under conventional ventilation in general operating rooms can provide the greatest benefit to patients and cost savings to hospitals.
The results of this trial also support the above-mentioned view that prevention of surgical site infections should not focus only on on-air disinfection. Without a reasonable reduction in operating time and regulation of the number of medical and nursing staff entering the operating room, even with the use of upper-level flat-light UV light air disinfection, its benefit in controlling SSI is still limited. The effective implementation of comprehensive preventive measures for SSI control and the judicious use of other air-cleaning technologies, such as upper-level UV light air disinfection, can help to reduce patient suffering and treatment costs, which is a direction that is constantly being explored by sensory control staff and clinicians.
References
[1] The use of light therapy in veterinary clinical practice [J]. Sun Lixia. Information on animal husbandry and veterinary science and technology. 2020(11)
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