Ventilator-associated pneumonia (VAP) is a clinical entity leading to increased morbidity and mortality in mechanically ventilated patients. VAP can occur when secretions from the oropharynx or stomach are aspirated into the lower respiratory track. These bacteria-rich secretions can pool in the oropharynx or subglottic space above the endotracheal tube cuff, so removal of these secretions is one strategy for reducing VAP. Multiple randomized Controlled studies including over 3,100 patients and subsequent meta-analyses have examined subglottic suctioning as an intervention to reduce VAP incidence. These trials have demonstrated a significant reduction in VAP, with studies ranging from 40-67% VAP reduction, with some studies reporting secondary outcomes in reduced antibiotic exposure, delayed onset of VAP, decreased length of mechanical ventilation, and decreased length of ICU stay. A small number of case reports have shown complications due to damage of the tracheal mucosa with high frequency or continuous subglottic suction, but no increase in mortality has been seen with subglottic suctioning.
Five meta-analyses were reviewed which examined the effect of subglottic suctioning on pneumonia (hospital-acquired or ventilator-associated) incidence. All five studies concluded that subglottic suctioning significantly reduced pneumonia incidence by 44-49%. Subglottic suctioning also improved secondary clinically relevant outcomes such as reduced duration of mechanical ventilation and delayed onset of VAP.
Device Failures and Patient Harm
Several studies have identified damage to tracheal mucosa and failure to suction as limitations of subglottic suctioning. These adverse events are associated with specialized endotracheal tubes with dorsal subglottic suction orifices and continuous or high frequency (every 15 seconds), intermittent suctioning. Less frequent intermittent subglottic suctioning such as every 1 hour which has been employed in several randomized control trials (Lacherade 2010, Lorente 2007, and Mahul 1992) may not have these risks. Additionally, the clinically significant ramifications of tracheal mucosal entrapment, fistula formation and re-intubation, have been described in case reports of patients with prolonged orotracheal intubation (Harvey 2007) and patients in randomized trials (Girou 2004).
Limitations of current devices
During in-depth interviews with pulmonologists, critical care specialists, and respiratory therapists, users reported that the clinical performance of current commercial subglottic suction endotracheal tubes is severely limited. High blockage rates, low fluid removal, and blood evacuation are common issues reported by users (Exhibit B). Radiographic confirmation in 18 patients demonstrates that the dorsal suction port routinely comes into contact with airway tissues (Exhibit A). In a small on=going study being conducted at UCSF, postmortem examination of chronically ventilated patients has confirmed tissue damage from intermittent subglottic suctioning.