Epidemiology

One of the common settings in which pulmonary aspiration is known to take place is the perioperative period. Various risk factors including reduced consciousness, prolonged supine positioning, and illness acuity can predispose an individual to aspiration of gastric contents. In the US, reported incidence of perioperative pulmonary aspiration in the adult population ranges from 1 in 3216 (in 1993) to 1 in 7103 (in 2006).[5][6]​ Studies published in 1986 and 1993 reported that aspiration occurred in 1 in every 3000 cases of anesthesia and accounted for 10% to 30% of deaths associated with anesthesia.[2][5][7]​ Although the incidence of aspiration is low, the extent of surgery has increased in people with comorbidities and the older population, and these patients are expected to have a higher incidence of aspiration.[8]

In the pediatric population, one UK study published in 2013 notes an incidence of perioperative pulmonary aspiration of 1 in 4932 anesthetics in the elective setting and 1 in 4498 in the emergency setting.[9]​ This suggests an improvement compared with two prior US landmark studies in children, which reported an incidence of 1 in 2632 aspirations during general anesthesia between 1985 and 1997, and 1 in 978 between 1988 and 1993.[10][11]

Despite a low incidence, perioperative pulmonary aspiration carries a risk of morbidity and mortality. In US anesthesia malpractice claims data, 5% were attributed to aspiration, with a 57% mortality directly attributable to anesthesia.[12]​ Of those who aspirated, 61% had gastrointestinal obstruction or an acute abdomen.[12]

The body of literature regarding acute aspiration outside of the perioperative time frame is smaller, and limited by the lack of specific diagnostic testing for aspiration when it is not witnessed. Between 5% and 15% of community-acquired pneumonia has been attributed to aspiration.[2]​ Pneumonia due to aspiration events is more frequent in patients ages >80 years (10%) compared with patients ages <80 years (5%).[13]​ Predisposing factors for aspiration included dysphagia, and impaired consciousness and gag reflex.[13]​ Another study noted that of a cohort of patients admitted with pneumonia ages >70 years, about 55% were found to have dysphagia and aspiration on testing with a water swallow test.[14]​ In the Lung Injury Prediction Score cohort, aspiration was the third leading cause of acute lung injury among at-risk patients admitted to the US hospitals.[15]

Dysphagia may cause "acute on chronic" aspirations. According to one systematic review from 2005, the incidence of dysphagia (swallowing difficulties) following acute stroke was reported to vary from 37% to 78% depending on the site of the stroke and screening tools used to identify dysphagia.[16][17]​ A review from 2010 reported that up to 30% of older patients with dysphagia present with aspiration.[18]

Among patients admitted to the hospital who are receiving enteral nutrition, the reported prevalence varies widely from 4.4% to nearly 90%, depending on how aspiration is defined (silent versus symptomatic), the method of diagnosis, the position of the feeding tube in the gastrointestinal tract (nasogastric or nasojejunal), and the type of feeding tube (nasogastric or gastrostomy).[19][20]​​​ One meta-analysis conducted in 2019 including 41 studies and involving 3248 participants suggests there is a lower incidence of pulmonary aspiration with postpyloric feeding tube positioning compared with gastric positioning.[21]​ Clinically evident aspiration, however, is rare and is seen in <1% of patients given enteral nutrition.[20]

I​n the setting of severe trauma, the incidence of gross aspiration can be as high as 38%.[22]

Accidental aspiration of barium contrast medium during radiologic investigations is rare but can occur in up to 8% of children with GERD.[23] The severity of pulmonary damage depends on the density of the suspension, with high-density barium sulfate causing the most damage and being potentially fatal, especially in older patients.[4][24][25][Figure caption and citation for the preceding image starts]: Bronchoscopy showing barium aspiration in a lung transplant patient in the right mainstem bronchus after a barium swallow studyFrom the collection of Dr Kamran Mahmood [Citation ends].com.bmj.content.model.Caption@20a0d6c9[Figure caption and citation for the preceding image starts]: Barium aspiration. A barium swallow was conducted in a 53-year-old woman. Imaging revealed hyperdense airway-centered material in the left lower lobe consistent with barium aspiration bronchiolitis. A tracheoesophageal fistula was confirmedFrom the collection of Dr Augustine Lee; used with permission of Mayo Foundation for Medical Education and Research, all rights reserved [Citation ends].com.bmj.content.model.Caption@24b19f77

Use of this content is subject to our disclaimer