Impact of air-conditioner outlet layout on the upward airflow induced by forced air warming in operating rooms


      • Relationship of position between ACOL and operating bed is important.
      • FAW can be used safely in the OR with appropriate ACOL position.
      • ACOL is more important to reduce contamination than cleanliness ability of OR.



      Previously, we found that an upward air current in the head area, induced by forced air warming (FAW), was completely counteracted by downward laminar airflow. However, this study did not include any consideration of the air-conditioner outlet layout (ACOL); hence, its impact remains unclear.


      This study was performed in 2 operating rooms (ORs)—ISO classes 5 and 6, which are denoted as OR-5 and OR-6, respectively. Both ORs have distinct ACOLs. The cleanliness, or the number or ratio of shifting artificial particles was evaluated.


      During the first 5 minutes after particles generation, significantly more particles shifted into the surgical field in OR-5 when compared to OR-6 (13,587 [4,341-15,913] and 106 [41-338] particles/cubic foot, P < .0001). Notably, FAW did not increase the number of shifting particles in OR-6. The laminar airflow system fully counteracted the upward airflow caused by FAW in OR-6, where the ACOL covered the operating bed. However, this did not occur in OR-5, where the ACOL did not fully cover the operating bed.


      Regardless of cleanliness ability of OR, an ACOL that fully covers the operating bed can prevent upward airflow in the head area and reduce the number of artificial particles shifting into the surgical field, which are typically caused by FAW.

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