To prevent serious pulmonary complications, nurses must confirm correct feeding tube location upon initial insertion and at regular intervals thereafter. Repeated x-rays for this purpose are impractical because of expense, radiation risk, and inaccessibility to patients in non-acute care settings. Previous studies have indicated that bedside pH testing is a promising method for predicting tube position; yet, instances of outlier readings occur frequently enough to require additional corroborative data. This study's ultimate aim is to facilitate development of bedside enzyme tests to use in conjunction with pH tests to confirm proper tube position, thereby increasing patient safety in a cost-effective manner. Before bedside enzyme tests can be developed, it is necessary to determine (1) the usual levels of pepsin and trypsin in feeding tube aspirates (by laboratory analyses) and (2) the extent to which the presence and concentration of these enzymes can predict feeding tube location. This basic work will be accomplished in the proposed study. Should the results demonstrate desirability and feasibility of bedside enzyme tests, a commercial source will be sought to develop the tests, and carry them to the clinical testing required by the FDA for a diagnostic, and production and marketing. The study will be conducted at five hospitals over a three year period, and a sample size of 400 subjects will be sought (200 with nasogastric tubes and 200 with nasointestinal tubes). Variables will include age, and presence or absence of H2 receptor antagonists. Data will be collected in two phases for each subject: immediately after feeding tube placement, and again after feedings have been initiated. Following initial placement (and within five minutes after an x-ray), fluid will be aspirated and tested for pH. The, laboratory analyses for enzymes (pepsin and trypsin) will be performed. Results of pH and enzyme tests will be compared to actual tube position, as determine by x-ray. The second phase of the study will also involve comparison of pH and enzyme measurements (at least one hour after feedings have ceased) with radiologic results. It is hypothesized that gastric aspirates will have low pH values and contain pepsin, and that intestinal aspirates will have high pHs and contain trypsin. Further, it is expected that inadvertent respiratory placement can be ruled out by the presence of pepsin or trypsin in fluid aspirated from the tube.
