Assessment of the Environmental and Economic Impact of Air Changes in a Hospital Operating Room

Abstract

Potentially high risk medical procedures are performed in hospital operating rooms (ORs) across the country on a daily basis. There are detailed and stringent procedures in place for routine practices, such as handwashing and instrument sterilization, and for the HVAC (heating, ventilation and air conditioning) systems, such as controlling humidity and ventilation rates. To maintain the sterile conditions, ventilation rates, measured in air changes per hour (ACH), are understandably higher than any other hospital space. While the highest air change rates may be required to provide a quality indoor environment to minimize the risk of surgical site infections (SSIs), there are significant capital and operating costs associated with these requirements.

The ventilation requirements for ORs have increased over the past 10 years with minimal data to support that more air provides cleaner conditions. We hypothesized that a test of the air quality utilizing dynamic, surgical procedures would provide evidence showing increased ventilation does not necessarily provide cleaner conditions. The costs were estimated based on actual energy usage, while the air quality metrics were Environmental Quality Indicators (EQIs). This enabled a comparative analysis of the costs and benefits of different air change rates in an operating room to assist in defining the optimum air change rates.

To compare the air quality in ORs under realistic conditions, a testing protocol using EQIs was developed and implemented by an interdisciplinary team, including medical clinicians, air quality experts and engineers experienced in ORs. The testing included a “mock’ surgical procedure directed by a Board certified surgeon in three actual operating rooms using standard gowning and sterilization practices with experienced staff to simulate actual conditions.

The results showed that the air quality was significantly better at 20 ACH than at 15 ACH, but did not significantly improve at 25 ACH. The additional operating costs for 5 ACH at the typical facilities tested was approximately $4000 per year per operating room. For academic medical centers and hospital systems with many ORs, this could be significant savings, but the cost must be weighed against the risk of potentially increasing surgical site infections (SSIs).