Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: the effect of body position

Ann Intern Med. 1992 Apr 1;116(7):540-3. doi: 10.7326/0003-4819-116-7-540.


Objective: To determine if the semirecumbent position (45-degree angle) decreases aspiration of gastric contents to the airways in intubated and mechanically ventilated patients.

Design: A randomized, two-period crossover trial.

Setting: Respiratory intensive care unit.

Patients: Nineteen patients requiring intubation and mechanical ventilation.

Interventions: Patients were studied in the supine and semirecumbent positions on two separate days.

Measurements: After technetium (Tc)-99m sulphur colloid labeling of gastric contents, sequential radioactive counts in endobronchial secretions were measured at 30-minute intervals over a 5-hour period. Samples of endobronchial secretions, gastric juice, and pharyngeal contents were obtained for qualitative bacterial cultures.

Results: Mean radioactive counts in endobronchial secretions were higher in samples obtained while patients were in the supine position than in those obtained while patients were in the semirecumbent position (4154 cpm compared with 954 cpm; P = 0.036). Moreover, the aspiration pattern was time-dependent for each position: For the supine position, radioactivity was 298 cpm at 30 min and 2592 cpm at 300 min (P = 0.013); for the semirecumbent position, radioactivity was 103 cpm at 30 min and 216 cpm at 300 min (P = 0.04). The same microorganisms were isolated from stomach, pharynx, and endobronchial samples in 32% of studies done while patients were semirecumbent and in 68% of studies done while patients were in the supine position.

Conclusions: We conclude that the supine position and length of time the patient is kept in this position are potential risk factors for aspiration of gastric contents. Elevating the head of the bed for patients who can tolerate the semirecumbent position may be a simple, no-cost prophylactic measure.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Female
  • Gastric Juice / microbiology
  • Humans
  • Male
  • Middle Aged
  • Pharynx / microbiology
  • Pneumonia, Aspiration / etiology*
  • Pneumonia, Aspiration / prevention & control*
  • Posture
  • Respiration, Artificial / adverse effects*
  • Respiration, Artificial / methods*
  • Risk Factors
  • Supine Position
  • Technetium Tc 99m Sulfur Colloid
  • Trachea / microbiology


  • Technetium Tc 99m Sulfur Colloid