Ventilator‑associated pneumonia (VAP), also known as postoperative pneumonia, is a hospital‑acquired infection. There is no consensus definition, but it is often considered to be nosocomial pneumonia that occurs 48 hours or more after intubation with an endotracheal or tracheostomy tube, and was not present before intubation. Clinical signs and symptoms of VAP are similar to those of many common conditions in intensive care unit (ICU) patients, such as acute respiratory distress syndrome, sepsis and cardiac failure. There is no gold standard to diagnose VAP; a firm diagnosis is generally made on the basis of clinical signs and symptoms, chest X‑ray and microbiological confirmation (American Thoracic Society, 2005).

The precise number of patients in the NHS having mechanical ventilation each year is unknown. However, the incidence of prolonged mechanical ventilation (defined as a period of 21 days or more) in critically ill patients in a health care region of the UK was reported as 4.4 per 100 ICU admissions and 6.3 per 100 ventilated ICU admissions. In addition, 1 in 16 ventilated patients needed prolonged mechanical ventilation (Lone and Walsh 2011; Nouraei et al. 2009).

The exact incidence of VAP is difficult to quantify because of a lack of standardised criteria for VAP diagnosis. There are no current data on the incidence of VAP in the UK, but in the USA VAP represents 31% of all ICU‑acquired infections. According to a systematic review and meta‑analysis of English language publications, VAP is associated with substantial morbidity, a 2‑fold mortality rate, longer hospital stays and related additional hospital costs (Safdar et al. 2005). A more recent systematic review and meta‑analysis, based on English language publications only, also estimated that the overall attributable mortality rate of VAP is 13% (Melsen et al. 2013).

VAP contributes to approximately half of all cases of hospital‑acquired pneumonia (American Thoracic Society 2005; Vincent et al. 1995). Risk factors for developing VAP include a primary admitting diagnosis of burns, trauma, central nervous system disease, respiratory disease, cardiac disease, mechanical ventilation in the previous 24 hours, witnessed aspiration and paralytic agents (Cook et al. 1998). Non‑modifiable risk factors for hospital‑acquired pneumonia include old age, underlying chronic lung disease, immunosuppression and previous thoracoabdominal surgery (American Thoracic Society 2005; Tablan et al. 2004). A recent European study found that VAP did not occur more frequently in older people, but the associated mortality in these patients was higher (Blot et al. 2014).

Modifiable risk factors include reintubation, a depressed level of consciousness, malnutrition, oropharyngeal colonisation, enteral nutrition, supine positioning and stress bleeding prophylaxis (American Thoracic Society 2005; Tablan et al. 2004). Nonpharmacological preventive measures for VAP include, among others, an oral (non‑nasal) route of intubation and continuous subglottic drainage (Kollef 1999; Dodek et al. 2004). For several years, designers have been developing endotracheal tubes with features intended to reduce VAP incidence, such as inflatable cuffs or subglottic suction ports.