1. Total volatile organic compound concentration in operating room
The TVOC concentration at the two locations (“near the operating table” and “away from the operating table”) in 31 cases where the evacuation system was used and 30 cases where it was not used is shown in Figure 2. One case among the evacuation system group was excluded from analysis for the trouble of the measurement machine system. The average TVOC concentration ± standard deviation near the operating table when using the system was 28.3 ± 36.16 μg/m3, while the average concentration when not using the system was 68.5 ± 31.6 μg/m3. The average concentration when using the system was significantly lower than when not using the system (p<0.001). Away from the operating table, the average concentration was 13.8 ± 17.4 g/m3 when using the system and 33.6 ± 21.5 g/m3 when not using it. The average concentration was again significantly lower when the system was used compared with when it was not used (p<0.01).
As an example, Figure 3 shows changes in TVOC concentration over time for a procedure performed in operating room No. 12 with the evacuation system and another procedure performed without using the system. There were three significant TVOC concentration peaks during the procedure without the evacuation system, exceeding 3,000 μg/m3 near the operating table. Conversely, during the procedure where the evacuation system was used, the level peaked at around 175 μg/m3 30 minutes after the operation started.
- Dust concentration in operating room
The average dust concentration values and standard deviations at the two locations (“near the operating table” and “away from the operating table”) when the evacuation system was used and when it was not used were measured. The average dust concentration ± standard deviation near the operating table when using the system was 4.3 ± 5.2μg/m3, and when not using it, the average concentration was 4.8 ± 6.9 μg/m3. Away from the operating table, the respective figures were 3.6 ± 3.5 μg/m3 and 3.5 ± 3.4 μg/m3. No statistically significant differences between the two groups were observed. These figures are extremely low when compared with Japan’s indoor environment standard of 0.15 mg/m3 or less (150 μg/m3), as stipulated in the Act on Maintenance of Sanitation in Buildings.
- Formaldehyde concentration in operating room
The average formaldehyde concentration values and standard deviations at the two locations (“near the operating table” and “away from the operating table”) when the evacuation system was used and when it was not used are shown in Figure 4. The average formaldehyde concentration ± standard deviation near the operating table when using the system was 15.5 ± 8.4 μg/m3, and when not using it, the average concentration was 39.4 ± 18. 6μg/m3. The average concentration when using the system was significantly lower than when not using the system (p<0.001). Away from the operating table, the average formaldehyde concentration value was 7.3 ± 5.1 μg/m3 when using the system and 20.1 ± 14.1 μg/m3 when not using it, so the average concentration was likewise significantly lower when the system was used versus when it was not used (p<0.001).
- Temperature and humidity in operating room
The temperature near the operating table and away from the operating table when the evacuation system was used and when it was not used was maintained at 24 to 25°C, and no significant variation was observed.
The humidity near the operating table and away from the operating table when the evacuation system was used and when it was not used was maintained at 43.5 to 48.2%, and as was the case for temperature, no humidity differences were observed.
- Formaldehyde personal exposure level measurement results
The average formaldehyde exposure concentration ± standard deviation for surgeons, surgical assistants, anesthetists, direct care nurses (scrub nurses), and indirect care nurses (circulating nurses), broken down according to whether the evacuation system was used or not, is shown in Figure 5. For surgeons, surgical assistants, anesthetists, scrub nurses, and circulating nurses alike, the value was significantly lower for the “system used” group compared with the “system not used” group (p<0.05 or p<0.001). However, for both groups and all healthcare professional categories, the maximum formaldehyde exposure concentration did not exceed 100 μ/m3 (80 ppb), which is the indoor concentration limit suggested by Japan’s Ministry of Health, Labor and Welfare.
- Acetaldehyde personal exposure level measurement results
The average acetaldehyde exposure concentration ± standard deviation for surgeons, surgical assistants, anesthetists, direct care nurses (scrub nurses), and indirect care nurses (circulating nurses), broken down according to whether the evacuation system was used or not, is shown in Figure 6. The healthcare professionals for whom the results were significantly lower when the evacuation system was used versus when it was not used were surgeons, anesthetists, and scrub nurses (p<0.05, p<0.01, or p<0.001).
- Acetone personal exposure level measurement results
The average acetone exposure concentration ± standard deviation for surgeons, surgical assistants, anesthetists, direct care nurses (scrub nurses), and indirect care nurses (circulating nurses), broken down according to whether the evacuation system was used or not, is shown in Figure 7. The healthcare professionals for whom the results were significantly lower when the evacuation system was used versus when it was not used were surgeons and anesthetists (p<0.05 or p<0.01).
- Multiple regression analysis for healthcare professionals’ personal exposure levels
To test the relationship between the formaldehyde, acetaldehyde, and acetone personal exposure levels measured for healthcare professionals and various factors, a multiple regression analysis (stepwise method) was performed. The following were treated as independent variables: years of experience as a surgeon, whether or not the evacuation system was used, the type of mastectomy procedure, the type of anesthetic (sevoflurane: 0, desflurane: 1), operating time (minutes), operating room area (m2), operating room volume (m3), HEPA air flow (passage through HEPA filter: m3/hr), air exchange rate (per hour), and fresh air volume (fresh air intake volume: m3). The dependent variables were the formaldehyde, acetaldehyde, and acetone personal exposure levels of surgeons, surgical assistants, anesthetists, scrub nurses, and circulating nurses.
The formaldehyde personal exposure level multiple regression analysis results are shown in Table 2. For the decision variable (adjusted R2), the results were: 0.253 for surgeons, 0.158 for surgical assistants, 0.329 for anesthetists, 0.066 for scrub nurses, and 0.144 for circulating nurses. With regard to stepwise method independent variables, the factor remaining at the end for all healthcare professionals was use of the evacuation system. The acetaldehyde personal exposure level multiple regression analysis results are shown in Table2. For the decision variable (adjusted R2), the result was highest for anesthetists (0.257), while the factor remaining at the end was use of the evacuation system for surgeons, surgical assistants, anesthetists, and scrub nurses.
Based on the above results, it is clear that the evacuation system was a factor that significantly impacted healthcare professionals’ formaldehyde and acetaldehyde personal exposure levels, which were greatly reduced by the use of the system.