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A Model for Identifying the Optimal Clinical Practice
In this issue of CHEST (see page 405), Fink and colleagues describe their experience using various change intervals for ventilator circuit tubing at a tertiary teaching hospital. Using a sequential study design, these authors demonstrated that the incidence of ventilator-associated pneumonia (VAP) was significantly lower with circuit change intervals of either 7 days (3.3 per 1,000 ventilator days) or 30 days (6.3 per 1000 ventilator days) compared to their established practice of changing ventilator circuits every 2 days (11.9 per 1,000 ventilator days) (p=0.0004). Additionally, extending the use of ventilator circuits to 30 days resulted in a cost savings of $4,231 for each ventilator in use at their institution.
It is important to note that the design of this study has several important limitations that restrict the general application of the authors' findings. First, a sequential design was used which did not adequately control for ongoing changes in medical practices at the study facility. An important example of this is the switch to heated wire circuits which occurred after the second year of the study. The use of heated wire circuits may have decreased the incidence of VAP by reducing the accumulation of contaminated tubing condensate. Several studies have suggested that the presence of such condensate increases the risk of developing VAP.12 Second, severity of illness and hospital mortality between the study groups was not compared. Therefore, we cannot ascertain the full impact of the intervention on patient outcomes. Third, a clinical diagnosis of VAP was employed which did not rely on quantitative lower airway cultures. This clinical method of establishing the diagnosis of VAP is controversial due to its lack of specificity.3 However, investigations suggest that the use of clinical criteria are acceptable due to their greater sensitivity and their good correlation with patient outcomes.4,5
Despite the limitations noted, this investigation provides additional data confirming the safety and cost-effectiveness of prolonged ventilator circuit usage. To facilitate recommendations regarding specific medical practices, qualities of evidence...