Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorJody W.ZylkeMD, Contributing EditorIndividualAuthor
To the Editor: Dr Girou and colleagues1 concluded that patients who received noninvasive ventilation (NIV) had significantly lower rates of nosocomial pneumonia and other infections than patients who received endotracheal intubation and mechanical ventilation. Although this was described as a matched case-control study, the design was actually a retrospective cohort study—patients were selected on the basis of exposure and their outcome was then ascertained. Rates of infection were calculated on this basis. Based on their data, we calculate the relative risk of nosocomial pneumonia for patients undergoing mechanical ventilation as 2.75 (95% confidence interval [CI], 0.94-8.06), and the relative risk of any infection as 2.71 (95% CI, 1.25-5.88). However, because ventilation was initiated within 72 hours of admission but infections occurring as early as 48 hours after admission were included, it is unclear whether the exposure (type of ventilation) truly preceded the outcome (infection) in all patients. Unnecessary restriction of sample size by the matching process and use of some historical controls further limit the generalizability of these data.
Kagramanov V, Lyman A. Noninvasive Ventilation and Nosocomial Infection. JAMA. 2001;285(7):881. doi:10.1001/jama.285.7.879