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• Background Although assessment for aspiration of small volumes of gastric contents in tube-fed patients receiving mechanical ventilation is important, available methods for this purpose are not wholly satisfactory. A potential method is immunoassay of tracheal secretions for the gastric enzyme pepsin. • Objectives To determine the frequency with which pepsin in suctioned tracheal secretions from acutely ill, tube-fed patients receiving mechanical ventilation could be detected via an immunoassay. • Methods A convenience sample of 136 specimens of suctioned tracheal secretions was collected from 30 acutely ill, tube-fed adults receiving mechanical ventilation. Multiple samples were obtained from 26 of the 30 patients (range, 2–11 per subject). An immunoassay with rooster polyclonal antibodies to purified human pepsin was used to detect pepsin in the secretions. • Results Fourteen specimens tested positive for pepsin. Secretions from 5 patients accounted for the 14 pepsin-positive results. A significant relationship was found between the position of the head of the bed and the presence of pepsin in tracheal secretions (P< .001). Of the 14 pepsin-positive specimens, 13 (92.9%) were obtained from subjects in a flat position. • Conclusions A pepsin immunoassay can be used to detect pepsin in human tracheal secretions. If pepsin in tracheal secretions is considered an indicator of aspiration of gastric contents, aspiration occurred in 5 of the 30 subjects. A flat position is strongly associated with the presence of pepsin in tracheal secretions.

Study objective-To determine the extent to which a mixture of human gastric juice and enteral formula stained with two concentrations of FD&C Blue No. 1 food dye (0.8 and 1.5 mL/L) is visible in suctioned tracheobronchial secretions following three forced small-volume pulmonary aspirations over a 6-h period in an animal model. Design-Experimental 2 × 3 repeated measures.Setting-Animal laboratory and an acute care hospital. Participants-Ninety New Zealand white rabbits weighing approximately 3 kg each, and 90 acutely ill adults who furnished gastric juice.Interventions-A mixture of human gastric juice and enteral formula stained with 0.8 or 1.5 mL of dye per liter was instilled intratracheally over a 30-min period into anesthetized intubated animals at baseline, 2 h, and 4 h. A total of 0.4 mL/kg of the mixture was instilled at each session. Ninety minutes after each instillation, suctioned secretions were examined for visible dye and blood.Measurements and results-Dye was visible in 46.3% of the secretions (125 of 270). The concentration of dye had no significant effect on dye visibility. Blood that was present in 114 of 270 of the secretions (42.2%) interfered with dye visibility in all but two secretions. For reasons unknown, even in the absence of blood, dye visibility decreased from 90.2% (55 of 61 secretions) after the first aspiration event to only 61% (25 of 41 secretions) after the third aspiration event.Conclusions-Findings from this animal model study do not support the use of the dye method to detect repeated small-volume aspirations. For clinicians who choose to use the dye method in selected situations, it appears that a dye concentration of 0.8 mL/L may be as effective in detecting aspiration as a 1.5 mL/L concentration. Keywordsaspiration/diagnosis; enteral nutrition; food coloring agents/diagnostic use; pneumonia; rabbits A method often used to detect aspiration in tube-fed patients consists of adding FD&C Blue No. 1 dye to the feeding solution and observing for its appearance in secretions suctioned from the airway. 1-4 However, there is little research-based evidence defining the efficacy of this approach. To the contrary, several small studies 5-8 have indicated that it has low sensitivity. In addition, there is little agreement as to how the method should be implemented. 9The amount of dye that must be added to enteral formula in order to detect aspiration is unknown. In clinical practice, it is common to add dye until the visual intensity is perceived to "look right." The reported amounts to achieve this nebulous color intensity range from as little as a few drops per 240 mL of formula up to 10 mL per bag of formula (total volume unspecified). 10 Another factor to consider is the color of the gastric juice with which the dyestained formula becomes mixed as it is administered into the stomach. For example, while gastric juice may be clear and colorless, it is often green (from refluxed bile) or brown (from digested blood). 11 Therefore, it is conceivable that mixing a dye-stained ente...