Forced-air warming and ultra-clean ventilation do not mix: an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics

J Bone Joint Surg Br. 2011 Nov;93(11):1537-44. doi: 10.1302/0301-620X.93B11.27124.


We investigated the capacity of patient warming devices to disrupt the ultra-clean airflow system. We compared the effects of two patient warming technologies, forced-air and conductive fabric, on operating theatre ventilation during simulated hip replacement and lumbar spinal procedures using a mannequin as a patient. Infection data were reviewed to determine whether joint infection rates were associated with the type of patient warming device that was used. Neutral-buoyancy detergent bubbles were released adjacent to the mannequin's head and at floor level to assess the movement of non-sterile air into the clean airflow over the surgical site. During simulated hip replacement, bubble counts over the surgical site were greater for forced-air than for conductive fabric warming when the anaesthesia/surgery drape was laid down (p = 0.010) and at half-height (p < 0.001). For lumbar surgery, forced-air warming generated convection currents that mobilised floor air into the surgical site area. Conductive fabric warming had no such effect. A significant increase in deep joint infection, as demonstrated by an elevated infection odds ratio (3.8, p = 0.024), was identified during a period when forced-air warming was used compared to a period when conductive fabric warming was used. Air-free warming is, therefore, recommended over forced-air warming for orthopaedic procedures.

MeSH terms

  • Aged
  • Air Microbiology
  • Air Movements
  • Arthroplasty, Replacement / adverse effects
  • Arthroplasty, Replacement / methods*
  • Arthroplasty, Replacement, Hip / adverse effects
  • Bacteria / isolation & purification
  • Heating / adverse effects
  • Heating / methods*
  • Hip Joint / microbiology
  • Humans
  • Intraoperative Care / adverse effects
  • Intraoperative Care / methods
  • Knee Joint / microbiology
  • Lumbar Vertebrae / surgery
  • Manikins
  • Operating Rooms*
  • Prosthesis-Related Infections / etiology
  • Surgical Wound Infection / etiology
  • Ventilation / methods*