The effect of operating lights on laminar flow: an experimental study using neutrally buoyant helium bubbles

The interaction between surgical lighting and laminar airflow is poorly understood. We undertook an experiment to identify any effect contemporary surgical lights have on laminar flow and recommend practical strategies to limit any negative effects.

Neutrally buoyant bubbles were introduced into the surgical field of a simulated setup for a routine total knee arthroplasty in a laminar flow theatre. Patterns of airflow were observed and the number of bubbles remaining above the surgical field over time identified. Five different lighting configurations were assessed. Data were analysed using simple linear regression after logarithmic transformation.

In the absence of surgical lights, laminar airflow was observed, bubbles were cleared rapidly and did not accumulate. If lights were placed above the surgical field laminar airflow was abolished and bubbles rose from the surgical field to the lights then circulated back to the surgical field. The value of the decay parameter (slope) of the two setups differed significantly; no light (b = -1.589) versus one light (b = -0.1273, p < 0.001). Two lights touching (b = -0.1191) above the surgical field had a similar effect to that of a single light (p = 0. 2719). Two lights positioned by arms outstretched had a similar effect (b = -0.1204) to two lights touching (p = 0.998) and one light (p = 0.444). When lights were separated widely (160 cm), laminar airflow was observed but the rate of clearance of the bubbles remained slower (b = -1.1165) than with no lights present (p = 0.004).

Surgical lights have a significantly negative effect on laminar airflow. Lights should be positioned as far away as practicable from the surgical field to limit this effect. Cite this article: Bone Joint J 2017;99-B:1061-6.