How Often Should Ventilator Circuits be Changed?
December 1, 2001
How Often Should Ventilator Circuits be Changed?
Abstract & CommentaryHan and colleagues investigated whether decreasing ventilator circuit changes from every 2 days to every 7 days would impact ventilator-associated pneumonia rates. All mechanically ventilated patients at Peking Union Medical College Hospital in China were studied over a 21-month period. From March 1998 to February 1999, ventilator circuits were changed every 2 days, and from June 1999 through December 1999, ventilator circuits were changed every 7 days. Nosocomial pneumonia was identified using the criteria of the Centers for Disease Control. In the 2-day-change group, there were 2277 ventilator-patient days and 38 patients developed pneumonia, resulting in a pneumonia rate of 16.7 cases per 1000 ventilator days. The 7-day-change group accumulated 972 ventilator days and 8 patients contracted pneumonia, resulting in a pneumonia rate of 8.2 cases per 1000 ventilator days. The pneumonia rate was significantly lower in the 7-day-change group (P = 0.007). To standardize for seasonal variability, results were compared from the same seasonal time frames (June 1998 to December 1998 for the 2-day-change group, and June 1999 to December 1999 for the 7-day-change group), and obtained similar findings; during those periods, pneumonia rates were 24.2 cases per 1000 ventilator days for the 2-day-change group and 8.9 cases per 1000 ventilator days for the 7-day-change group (P = 0.001). It is concluded that a circuit-change interval of 7 days had a lower risk of ventilator-associated pneumonia (VAP) than a 2-day change interval. (Han JN, et al. Effects of decreasing the frequency of ventilator circuit changes to every 7 days on the rate of ventilator-associated pneumonia in a Beijing hospital. Respir Care. 2001; 46[9]:891-896).
Comment by Dean R. Hess, PhD, RRT
It has become increasing recognized that VAP is unlikely to be related to the ventilator or the ventilator circuit per se. Patients are more likely to develop VAP from secretions aspirated past the cuff of the endotracheal tube than by what is breathed through the endotracheal tube. It is not surprising, then, that the rate of VAP has been reported to be decreased if subglottic secretions are aspirated so that they cannot be aspirated into the trachea. Moreover, reduced rates of VAP have been reported when noninvasive ventilation is used (therefore, no endotracheal tube) compared to invasive ventilatory support.
Over the past 15 years, there have been both observational studies1-5 and randomized, controlled trials6-9 reporting the effects of less frequent ventilator circuit changes. As individual studies, no significant differences in VAP have been reported when circuit change intervals have been lengthened. Several studies have now reported no change in VAP rates when circuits are only changed on an at-needed basis. It is interesting to note that no change in VAP rate occurred when inline suction catheters are changed on an as-needed basis rather than on a daily basis.10 For nearly 5 years, it has been the practice at the Massachusetts General Hospital to change ventilator circuits and inline suction catheters on an as-needed basis (and, of course, between patients).
I recently used the tools of evidence-based medicine and meta-analysis to explore the effects of less frequent ventilator circuit changes on the development of VAP. For the observational studies,1-5 the risk of VAP is significantly reduced (P = 0.04) for less frequent circuit changes (odds ratio, 0.79, 95% CI, 0.63-0.99). For the randomized controlled trials,6-9 the risk of VAP is also significantly reduced (P = 0.03) for less frequent circuit changes (relative risk, 0.70, 95% CI, 0.51-0.96). This analysis suggests that there might be a reduction of about 25% in the risk of VAP with less frequent circuit changes.
The available evidence suggests that ventilator circuits do not need to be changed at frequent intervals. In fact, the evidence suggests that ventilator circuits do not need to be changed at any regular intervals. Adoption of this practice results in important health care cost savings, and might actually decrease the risk for VAP.
References
1. Lareau SC, et al. Am Rev Respir Dis. 1978;118: 493-496.
2. Hess D, et al. Anesthesiology. 1995;82:903-911.
3. Thompson, RE. Respir Care. 1996;41:601-606.
4. Fink JB, et al. Chest. 1998;113:405-411.
5. Han JN, et al. Respir Care. 2001;46:891-896.
6. Craven DE, et al. Am Rev Respir Dis. 1986;133: 792-796.
7. Dreyfuss D, et al. Am Rev Respir Dis. 1991;143: 738-743.
8. Kollef MH, et al. Ann Intern Med. 1995;123:168-174.
9. Long MN, et al. Infect Control Hosp Epidemiol. 1996; 17:14-19.
10. Kollef MH, et al. Am J Respir Crit Care Med. 1997; 156:466-472.
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