The tracheal tube: gateway to ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is defined as pneumonia occurring in a mechanically ventilated patient after 48 hours of endotracheal intubation [1]. Despite significant advances in managing intubated patients, VAP remains a common and occasionally fatal complication in the ICU [2]. A systematic review of published data since 1990 showed the incidence of VAP to be 10 to 20%, with a possible two-fold increase in mortality attributable to VAP [3]. The ICU length of stay was also significantly increased by a mean of 6.1 days with an attributable cost of $10,019 per case [3]. A recent Canadian study estimated an additional 4.3 ICU days attributable to VAP, occupying 2% of all ICU days and an estimated national cost of CAN$43 million per year [4]. Similar findings were reported by a North American study with increased unadjusted ICU length of stay and mortality in patients with VAP (50% mortality in VAP patients versus 34% in non-VAP) with an estimated $11,897 attributable cost [5]. Furthermore, the burden of VAP takes up a significant portion of antibiotic dispensing in the ICU [6] and may well be a contributor to the development of multi-resistant bacteria [7].Importantly, many units are recently reporting a reduction in VAP incidence following implementation of various prevention measures, as well as programs that increase compliance with such care bundles [8-10].The pathogenesis of VAP mainly stems from the introduction of microbial pathogens by microaspiration past the tracheal tube cuff and into the lower respiratory tract (Figure 1). Subsequent colonization and overwhelming of the host mechanical, humoral and cellular defence mechanisms lead to the development of VAP [11]. The tracheal tube forms the essential first part of this mechanistic pathway by breeching the anatomic barriers formed by the glottis and larynx. Suppression of the cough reflex as a result of sedation further hampers natural reflexes [2]. The oropharynx, nasal sinuses and the stomach have