Effect of an anaesthetic screening drape on vertical laminar airflow

Abstract

Effective operating room ventilation is required to reduce the risk of surgical site infection. Vertical laminar airflow from above the surgical field provides a source of 'ultra-clean' air, carrying contaminants away from the operative site. An anaesthetic screening drape is often used to shield the operative site from the anaesthetic team, and this defies the principles of vertical laminar airflow. A mock theatre set-up for a total knee replacement was constructed with and without the use of an anaesthetic screening drape. A 10×10 grid was set up within the surgical canopy, and the downward air velocities were measured using a hot air anemometer. The average velocity and range of velocities at each grid point were measured in both set-ups. The range was used as the marker of turbulence. Within the surgical canopy, the average downward air velocity was 0.35m/s. With the use of an anaesthetic screening drape, the mean downward air velocity in the area above the patient decreased from 0.36m/s to 0.29m/s (P=0.02). In the area immediately above the drape, the average velocity was 0.18m/s. Turbulent air currents were produced in the areas adjacent to the drape near to the mock surgical site. For the area above the patient, the range increased from an average of 0.034m/s to 0.05m/s (P=0.04). In the area directly above the drape, the average range was 0.08m/s. Use of an anaesthetic screening drape causes disruption to normal vertical laminar airflow.