Performance Improvement of a Negative-Pressurized Isolation Room for Infection Control

Negative-pressurized isolation rooms have been approved effectively and applied widely for infectious patients. However, the outbreak of COVID-19 has led to a huge demand for negative-pressurized isolation rooms. It is critical and essential to ensure infection control performance through best practice of ventilation systems and optimum airflow distribution within isolation rooms. This study investigates a retrofitting project of an isolation room to accommodate COVID-19 patients. The field measurement has been conducted to ensure the compliance with the design specification from the CDC of Taiwan. The pressure differentials between negative-pressurized isolation rooms and corridor areas should be at least 8 Pa, while the air change rate per hour (ACH) should be 8–12 times. Computational fluid dynamics (CFD) is applied to evaluate the ventilation performance and contamination control. Different layout arrangements of exhaust air have been proposed to enhance the ventilation performance for infection control. A simple projected air-jet curtain has been proposed in the simulation model to enhance extra protection of medical staff. The resulting ventilation control revealed that the contamination control can be improved through the minor adjustment of exhaust air arrangement and the application of an air-jet curtain.

Do surgeons and surgical facilities disturb the clean air distribution close to a surgical patient in an orthopedic operating room with laminar airflow?

BACKGROUND

Airflow distribution in the operating room plays an important role in ensuring a clean operating microenvironment and preventing surgical site infections (SSIs) caused by airborne contaminations. The objective of this study was to characterize the airflow distribution in proximity to a patient in an orthopedic operating room.

METHODS

Experimental measurements were conducted in a real operating room at St. Olav's Hospital, Norway, with a laminar airflow system. Omnidirectional anemometers were used to investigate the air distribution in the operating zone, and 4 different cases were examined with a real person and a thermal manikin.

RESULTS

This study showed that the downward airflow from the laminar airflow system varies in each case with different surgical arrangement, such as the position of the operating lamp. The results indicate that the interaction of thermal plumes from a patient and the downward laminar airflow may dominate the operating microenvironment.

CONCLUSIONS

The airflow distribution in proximity to a patient is influenced by both the surgical facility and the presence of medical staff. A thermal manikin may be an economical and practical way to study the interaction of thermal plumes and downward laminar airflow. The provision of higher clean airflow rate in the operating microenvironment may be an effective way to prevent the development of SSIs caused by indoor airborne contamination.

Effect of heated-air blanket on the dispersion of squames in an operating room

High-fidelity, predictive fluid flow simulations of the interactions between the rising thermal plumes from forced air warming blower and the ultra-clean ventilation air in an operating room (OR) are conducted to explore whether this complex flow can impact the dispersion of squames to the surgical site. A large-eddy simulation, accurately capturing the spatiotemporal evolution of the flow in 3 dimensions together with the trajectories of squames, is performed for a realistic OR consisting of an operating table (OT), side tables, surgical lamps, medical staff, and a patient. Two cases are studied with blower-off and blower-on together with Lagrangian trajectories of 3 million squames initially placed on the floor surrounding the OT. The large-eddy simulation results show that with the blower-off, squames are quickly transported by the ventilation air away from the table and towards the exit grilles. In contrast, with the hot air blower turned on, the ventilation airflow above and below the OT is disrupted significantly. The rising thermal plumes from the hot air blower drag the squames above the OT and the side tables and then they are advected downwards toward the surgical site by the ventilation air from the ceiling. Temporal history of the number of squames reaching 4 imaginary boxes surrounding the side tables, the OT, and the patient's knee shows that several particles reach these boxes for the blower-on case.

Mobile laminar air flow screen for additional operating room ventilation: reduction of intraoperative bacterial contamination during total knee arthroplasty

BACKGROUND

Surgical site infections are important complications in orthopedic surgery. A mobile laminar air flow (LAF) screen could represent a useful addition to an operating room (OR) with conventional turbulent air ventilation (12.5 air changes/h), as it could decrease the bacterial count near the operating field. The purpose of this study was to evaluate LAF efficacy at reducing bacterial contamination in the surgical area during 34 total knee arthroplasties (TKAs).

MATERIALS AND METHODS

The additional unit was used in 17 operations; the LAF was positioned beside the operating table between two of the surgeons, with the air flow directed towards the surgical area (wound). The whole team wore conventional OR clothing and the correct hygiene procedures and rituals were used. Bacterial air contamination (CFU/m(3)) was evaluated in the wound area in 17 operations with the LAF unit and 17 without the LAF unit.

RESULTS

The LAF unit reduced the mean bacterial count in the wound area from 23.5 CFU/m(3) without the LAF to 3.5 CFU/m(3) with the LAF (P < 0.0001), which is below the suggested limit for an OR with ultraclean laminar ventilation. There were no significant differences in the mean bacterial count in the instrument table area: 28.6 CFU/m(3) were recorded with the LAF (N = 6) unit and 30.8 CFU/m(3) (N = 6) without the LAF unit (P = 0.631). During six operations with LAF and six without LAF, particle counts were performed and the number of 0.5 μm particles was analyzed. The particle counts decreased significantly when the LAF unit was used (P = 0.003).

CONCLUSION

When a mobile LAF unit was added to the standard OR ventilation, bacterial contamination of the wound area significantly decreased to below the accepted level for an ultraclean OR, preventing SSI infections.