Determining feeding tube location by gastric and intestinal pH values

The purpose of this study was to evaluate a series of pH values of aspirates from feeding tubes to differentiate between gastric and intestinal tube placement.

One hundred ventilator-supported subjects, with an order for nasoduodenal feeding tube placement were randomly selected. The feeding tube was placed into the stomach, verified by auscultation, and 2 pH measurements were obtained. After the pH measurements were taken, tube location was then verified by fluoroscopy. When the tube was advanced into the small intestine, location was verified by fluoroscopy, and 2 additional pH measurements were obtained.

From the selected subjects, both a gastric and intestinal aspirate were obtained from 82 subjects. For the 82 subjects, the mean gastric and intestinal pH values were 4.8 +/- 2.3 and 7.1 +/- 1.0, respectively. For patients receiving acid-suppressing agents, these values were 5.0 +/- 2.3 and 7.2 +/- 1.0, respectively. For subjects not receiving acid-suppressing agents, these pH values were 4.0 +/- 2.5 and 6.7 +/- 1.1, respectively. For all patients, using a pH value of 6.5 as a predictor of feeding tube location, the sensitivity and specificity were 0.66 and 0.90. In addition, when an increase in pH > or = 1.0 was used as a predictor of location change for all patients, the sensitivity was 0.58.

The pH value was a reliable predictor of nasoduodenal tube placement. However, radiographic confirmation of location could not be excluded because of the low sensitivity using pH measurements alone. An increase of > or = 1.0 in gastric vs intestinal pH specimens could be useful to determine use of radiography confirmation of tube placement.