The ultimate goal of the proposed study is to increase the safety of mechanically ventilated tube-fed patients. Because these patients are at high risk for frequent micro-aspirations of regurgitated gastric contents, they are prone to potentially life-threatening nosocomial pneumonia. Efforts are made in practice settings to detect these events early so that interventions can be initiated to prevent morbidity and mortality. However, nurses are often unsure about how to accomplish this because protocols for detection are not well defined; further, there are questions about the sensitivity and specificity for currently used methods. The overall major aim of the proposed work is to determine the accuracy of these currently used methods (observing tracheal secretions for dye added to the tube-feeding formula, and testing for glucose in tracheal secretions to determine if glucose-rich formula is present) and a potential new test which consists of assaying for pepsin in tracheal secretions. The study will require 240 experimental rabbits who will intubated and mechanically ventilated prior to have a mixture of human gastric juice and dye-stained enteral formula slowly instilled into their tracheas. The five independent variables are: two concentrations of dye (0.8 ml/L and 1.5 ml/L), three concentrations of glucose in the enteral formulas (low, moderate, and high), two volumes of the fluid instilled (0.2 ml/kg/hr and 0.33 ml/kg/hr), presence or absence of prior mild lung injury, and time of observation (2, 4 and 6 hours). Observations will be made on suctioned tracheal secretions every 2 hours over a 6-hour period and dependent variables will consist of: visibility of dye, concentration of glucose, and concentration of pepsin in the secretions. Twenty control animals with have normal saline intratracheally instilled. A secondary aim of the study is to determine in rabbits with healthy lungs whether three other dependent variables (peak airway pressures, mixed to determine in rabbits with healthy lungs whether three other dependent variables (peak airway pressures, mixed venous admixture readings, and neutrophil counts in post mortem pulmonary lavage fluid) are affected by an additional independent variable (use or non-use of gastric acid inhibiting agents by the 240 acutely ill humans who will provide the gastric juice for tracheal instillation in the rabbits). Following completion of the study, the animals will be euthanized and their lungs lavaged for neutrophil counts. Data will primarily be analyzed by repeated measures analyses of covariance (ANCOVAs) and main-effect F tests. While direct extrapolation of results from animals to humans is not possible, results from this study will provide information that will help nurses develop protocols for use in clinical settings to more effectively monitor for aspiration in mechanically ventilated tube-fed patients.

National Institute of Health (NIH)
National Institute of Nursing Research (NINR)
Research Project (R01)
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Special Emphasis Panel (ZRG1-ALTX-4 (03))
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Bryan, Yvonne E
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Saint Louis University
Schools of Nursing
Saint Louis
United States
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Metheny, Norma A; Stewart, Barbara J; McClave, Stephen A (2011) Relationship between feeding tube site and respiratory outcomes. JPEN J Parenter Enteral Nutr 35:346-55
Metheny, Norma A; Davis-Jackson, Jami; Stewart, Barbara J (2010) Effectiveness of an aspiration risk-reduction protocol. Nurs Res 59:18-25
Metheny, Norma A; Schallom, Lynn; Oliver, Dana A et al. (2008) Gastric residual volume and aspiration in critically ill patients receiving gastric feedings. Am J Crit Care 17:512-9;quiz 520
Metheny, Norma A; Clouse, Ray E; Chang, Yie-Hwa et al. (2006) Tracheobronchial aspiration of gastric contents in critically ill tube-fed patients: frequency, outcomes, and risk factors. Crit Care Med 34:1007-15
Metheny, Norma A; Schnelker, Renee; McGinnis, Joan et al. (2005) Indicators of tubesite during feedings. J Neurosci Nurs 37:320-5
Metheny, Norma A; Stewart, Jena; Nuetzel, Gretel et al. (2005) Effect of feeding-tube properties on residual volume measurements in tube-fed patients. JPEN J Parenter Enteral Nutr 29:192-7
Schallom, Lynn; Metheny, Norma A; Stewart, Jena et al. (2005) Effect of frequency of manual turning on pneumonia. Am J Crit Care 14:476-8
Metheny, Norma A; Dahms, Thomas E; Stewart, Barbara J et al. (2005) Verification of inefficacy of the glucose method in detecting aspiration associated with tube feedings. Medsurg Nurs 14:112-9, 121; discussion 120
Metheny, Norma A; Dahms, Thomas E; Chang, Yie-Hwa et al. (2004) Detection of pepsin in tracheal secretions after forced small-volume aspirations of gastric juice. JPEN J Parenter Enteral Nutr 28:79-84
Metheny, Norma A; Chang, Yie-Hwa; Ye, Jing Song et al. (2002) Pepsin as a marker for pulmonary aspiration. Am J Crit Care 11:150-4

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