Airborne bacteria in hospital operating rooms during ongoing surgery

Introduction
Post-operative infections obtained from open-wound surgeries constitute an unnecessary load on both healthcare and affected patients. It is well established that increased air cleanliness reduces the number of post-operative infections. Therefore, the ventilation system is important in order to reduce the number of infectious particles in the air during surgery. Ventilation with high airflow, as in operating rooms, consumes a high amount of energy and it is thus desirable to find energy efficient solutions.

Objectives
The purpose of this work was to evaluate air quality, energy efficiency and working environment comfort for three different ventilation techniques in operating rooms.

Method
The newly developed ventilation system temperature controlled airflow (TcAF) was compared with the conventionally used turbulent mixed airflow (TMA) and laminar airflow (LAF). In total, 750 air sample measurements were performed during 45 orthopaedic operations: 15 for each type of ventilation system [1]. The concentration of colony forming units (CFU)/m3 was measured at three locations in the rooms: close to the wound (<0.5 m), at the instrument table and peripherally in the room. The working environment comfort was evaluated in a questionnaire.

Results
Our study shows that both LAF and TcAF maintains CFU concentrations in the air during ongoing surgery significantly below 10 CFU/m3 at the wound and at the instrument table, and for TcAF also in the periphery of the room, see Figure 1. The median CFU concentration in TMA was at or above 10 CFU/m3 at all locations. TcAF used less than half the airflow to that of LAF, resulting in a 28% reduction in energy consumption. The working environment comfort was perceived less noisy and having less draft in the TcAF than the LAF ventilation.

Summary
Both the LAF and TcAF ventilation maintain high air cleanliness with low CFU concentrations throughout the operation. TMA is less efficient in removing bacteria from the air close to the patient.