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American Journal of Critical Care. 2009;18: 73-76 doi:10.4037/ajcc2009911
Copyright © 2009 by the American Association of Critical-Care Nurses.
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A regular feature of the American Journal of Critical Care, Clinical Evidence Review unveils available scientific evidence to answer questions faced in contemporary clinical practice. It is intended to support, refute, or shed light on health care practices where little evidence exists. To send an eLetter or to contribute to an online discussion about this article, visit www.ajcconline.org and click "Respond to This Article" on either the full-text or PDF view of the article. We welcome letters regarding this feature and encourage the submission of questions for future review.

Feeding Tube Placement in Adults: Safe Verification Method For Blindly Inserted Tubes

By Annette M. Bourgault, RN, MSc, CNCC(C) and Margo A. Halm, RN, PhD, CNS-BC. Annette M. Bourgault is an instructor with the department of Physiological and Technological Nursing, Medical College of Georgia, Augusta, where she teaches critical care, medical/surgical nursing, and evidence-based practice. Margo A. Halm is a clinical nurse specialist and director of nursing research and quality at United Hospital in St Paul, Minnesota, where she leads and mentors staff in principles of clinical research and evidence-based practice.

Corresponding author: Margo A. Halm, RN, PhD, CNS-BC, United Hospital - Mailstop 60316, 333 N. Smith Ave, St Paul, MN 55102 (e-mail: margo.a.halm{at}allina.com).

Enteral feeding is a common and necessary practice in critical care. Clinical practice for verification of small- and large-bore feeding tubes is variable. Although radiographic confirmation is the reference standard for blindly inserted small-bore tubes, it is not consistently performed to verify large-bore tubes before administration of formula or medication.

These practices raise concerns; both small- and large-bore tube placement in the tracheobronchial tree have been reported.1–6 Malpositioning has also involved the intracranial cavity.7 In a review of more than 2000 insertions of small-bore tubes, 50 pulmonary placements (3%) were detected.6 In another study,1 the incidence of inadvertent pulmonary placement did not differ between small- and large-bore tubes. Of note, endotracheal or tracheostomy tube cuffs do not prevent pulmonary malposition.6

Unfortunately, pulmonary malplacement may occur silently, without coughing, dyspnea, or oxygen desaturation.3 Adding confusion, aspirated fluids that resemble gastric fluids have been obtained from tubes placed in the lungs.8 Malpositioned tubes may cause pneumonia, pneumothorax, perforations, empyema, and bronchopleural fistula—events that can lead to death in rare cases.6 The Joint Commission9 identified pulmonary malposition of nasogastric tubes as one of the most frequent procedural complications that result in postoperative sentinel events. Expert recommendation included checking tube placement with an abdominal radiograph.9 Also, failure to report malpositioned tubes and complications due to insertion continues to be a problem.6

In addition to pulmonary malposition, aspiration risk is high when tubes are placed in the esophagus or gastroesophageal junction.10 Patients at highest risk are those who are sedated, confused, or uncooperative during insertion, and those who have artificial airways, decreased cough-gag reflexes, a decreased level of consciousness, or craniofacial trauma.10,11 Given the risk for tube malposition and aspiration in critically ill patients, this clinical review synthesizes current evidence on the accuracy of methods to verify initial placement of blindly inserted feeding tubes.


   Methods
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The search strategy included MEDLINE and CINAHL, as well as hand-searching bibliographies. Key words included enteral feeding/nutrition, nasogastric/feeding tubes, and placement/verification/confirmation. All types of evidence (nonexperimental/experimental, systematic reviews) were included, but only if the evidence related to verification of initial feeding tube placement in adults.


   Results
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Twelve pertinent studies were published between 1988 and 2007 (Table 1Go).1,2,4,8,12–19 A variety of methods were used to evaluate tube placement: 7 studies evaluated pH, 3 used capnography/capnometry, 3 used auscultation, 2 measured bilirubin levels, 1 measured enzyme levels, and 1 used visual inspection. Five of the 12 studies used multiple methods. Populations included adults from acute/intermediate care and intesive care unit settings. Sample sizes, often measured as number of feeding tubes or specimens, ranged from 51 to 880.


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  		Table 1 Evidence summary for verification of feeding tube placement in adults

 
pH Testing
Although a pH less than 5.0 may indicate gastric placement of a feeding tube, this method is not helpful for detecting esophageal placement, because aspirate could be gastric reflux.14 Other limitations include inability to determine placement when pH exceeds 6.0,14 difficulty obtaining aspirates,4,5,19 and possible inaccuracy related to use/timing of acid-lowering medications such as H2 blockers, and recent ingestion of enteral formula or food.4,13,14,19

Capnography/Capnometry
Carbon dioxide detection using capnography/capnometry has yielded variable results. With this method, color change indicates detection of carbon dioxide and, therefore, pulmonary placement. Although pulmonary vs gastric placement was differentiated in 2 studies, the exact location within the gastrointestinal tract was unknown.1,18 Pulmonary placement was suspected because carbon dioxide was detected in 27% of tubes, although such placement was not confirmed radiographically.1 A third study indicated 15 false-positive results, suggesting pulmonary placement, although disconfirmed by radiography.2 Furthermore, capnometry relies on tube patency and avoidance of reflux for accuracy.

Auscultation/Water Bubbling
Numerous studies identified audible air entry over the epigastrum even when tubes were malpositioned in the esophagus, pulmonary system, and brain.2–4,7 No research was located on the water bubbling method, which involves placing the proximal end of the tube into water to observe for bubbling. A case report confirmed that this method lacks accuracy; no bubbling was observed in a tube with known pulmonary placement, possibly because the ports were occluded.3

Bilirubin/Enzyme Testing
Pulmonary fluid has little or no trypsin or pepsin, whereas intestinal fluid has high levels of trypsin and gastric fluid has high levels of pepsin.15 On their own, bilirubin results can be misleading, because levels less than 5 mg/dL could indicate gastric/pulmonary placement; however, a combination of a pH greater than 5 and a bilirubin level less than 5 mg/dL typically indicates pulmonary placement.16,17 Similar to other verification methods, these tests may help to differentiate gastrointestinal from pulmonary placement of tubes, but are not helpful for determining whether tubes are placed in the esophagus or at the gastroesophageal junction.

Visual Inspection
Inspection of aspirated fluid had 48% to 90% accuracy for tube location in the stomach or intestines.8 However, visual inspection had only 57% accuracy for proper identification of the fluid source for tubes with pulmonary placement.8


   Recommendations
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Levels of evidence for feeding tube verification vary by methods, ranging from indeterminate to class III (Table 2Go). Although pH, enzyme, bilirubin, and carbon dioxide testing have been used to distinguish respiratory from gastrointestinal placement of feeding tubes, none of these methods has enabled detection of tube placement in the esophagus or gastroesophageal junction. Additionally, although bilirubin/enzyme testing shows promising results, these methods are not available for use at the bedside.15–17


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  		Table 2 Evidence grading

 
Three practices that have been used for tube verification—auscultation, aspirate inspection, and placing tubes underwater to assess for "bubbling"—should be discontinued because of their lack of established efficacy and potential risk for harm. Of concern, an audible "air pop" over the epigastrum falsely leads clinicians to assume correct gastric placement of a feeding tube. Hospital policies should be revised to reflect evidence-based practices.

Although clinicians may have concerns about financial and time constraints that make radiographic confirmation of all tube placements impractical, radiography remains the only reliable method to verify initial placement of blindly inserted small- or large-bore feeding tubes.21–23 In addition, according to research and expert opinion, secondary confirmation (via pH or carbon dioxide testing, visualization of tube at exit site) must be performed regularly to ensure ongoing assessment of tube location. Judgment must be used to assess for tube dislocation after the patient vomits or retches, or when tubes are improperly secured or pulled. Practice changes should include evaluation of outcomes and reporting of adverse events, including malpositioned tubes and the aspiration of formula or medications. Until verification methods consistently enable pulmonary and esophageal placement of feeding tubes to be detected, radiographic confirmation remains the method of choice for initial verification of blindly inserted feeding tubes.

To purchase electronic or print reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, reprints{at}aacn.org.


   REFERENCES
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  1. Burns SM, Carpenter R, Blevins C, et al. Detection of inadvertent airway intubation during gastric tube insertion: capnography versus a colorimetric carbon dioxide detector. Am J Crit Care. 2006;15(2):188–195.[Abstract/Free Full Text]
  2. Elpern EH, Killeen K, Talla E, et al. Capnometry and air insufflation for assessing initial placement of gastric tubes. Am J Crit Care. 2007;16(6):544–549.[Abstract/Free Full Text]
  3. Metheny N, Dettenmeier P, Hampton K, Wiersema L, Williams P. Detection of inadvertent respiratory placement of small-bore feeding tubes: a report of 10 cases. Heart Lung. 1990;19(6):631–638.[Medline]
  4. Neumann MJ, Meyer CT, Dutton JL, Smith R. Hold that x-ray: aspirate pH and auscultation prove enteral tube placement. J Clin Gastroenterol. 1995;20(4):293–295.[Medline]
  5. Metheny N, Wehrle MA, Wiersema L, Clark J. Testing feeding tube placement: auscultation vs pH method. Am J Nurs. 1998;98(5):37–42.[Medline]
  6. Sorokin R, Gottlieb JE. Enhancing patient safety during feeding-tube insertion: a review of more than 2000 insertions. JPEN. 2006;30(5):440–445.[Abstract/Free Full Text]
  7. Metheny NA. Inadvertent intracranial nasogastric tube placement. Am J Nurs. 2002;102(8):25–27.[Medline]
  8. Metheny N, Reed L, Berglund B, Wehrle MA. Visual characteristics of aspirates from feeding tubes as a method for predicting tube location. Nurs Res. 1994;43(5):282–287.[Medline]
  9. Joint Commission. Sentinel Event Alert: Operative and postoperative complications: lessons for the future. Joint Commission on Accreditation of Healthcare Organizations. 12; 4 February 2000. www.jointcommission.org/SentinelEvents/SentinelEventAlert/sea_12.htm.
  10. Metheny NA, Titler MG. Assessing placement of feeding tubes. Am J Nurs. 2001;101(5):36–45. Accessed August 29, 2008.[Medline]
  11. Metheny NA, Clouse RE, Chang YH, Stewart BJ, Oliver DA, Kollef MH. Tracheobronchial aspiration of gastric contents in critically ill tube-fed patients: frequency, outcomes, and risk factors. Crit Care Med. 2006;34(4):1007–1015.[CrossRef][Medline]
  12. Metheny NA, Spies MA, Eisenberg P. Measures to test placement of nasoenteral feeding tubes. West J Nurs Res. 1988;10(4):367–383.[Free Full Text]
  13. Metheny N, Williams P, Wiersema L, Wehrle MA, Eisenberg P, McSweeney M. Effectiveness of pH measurements in predicting feeding tube placement. Nurs Res. 1989;38(5): 280–285.[Medline]
  14. Metheny N, Reed L, Wiersema L, McSweeney M, Wehrle MA, Clark J. Effectiveness of pH measurements in predicting feeding tube placement: an update. Nurs Res. 1993;42(6): 324–331.[Medline]
  15. Metheny NA, Stewart BJ, Smith L, Yan H, Diebold M, Clouse RE. pH and concentrations of pepsin and trypsin in feeding tube aspirates as predictors of tube placement. JPEN. 1997;21(5):279–285.[Abstract/Free Full Text]
  16. Metheny NA, Stewart BJ, Smith L, Yan H, Diebold M, Clouse RE. pH and concentration of bilirubin in feeding tube aspirates as predictors of tube placement. Nurs Res. 1999;48(4):189–197.[CrossRef][Medline]
  17. Metheny NA, Smith L, Stewart BJ. Development of a reliable and valid bedside test for bilirubin and its utility for improving prediction of feeding tube location. Nurs Res. 2000; 49(6):302–309.[CrossRef][Medline]
  18. Araujo-Preza CE, Melhado ME, Gutierrez FJ, Maniatis T, Castellano MA. Use of capnometry to verify feeding tube placement. Crit Care Med. 2002;30(10):2255–2259.[CrossRef][Medline]
  19. Conner TM, Carver D. The role of gastric pH testing with small-bore feeding tubes in the intensive care unit. Dimens Crit Care Nurs. 2005;24(5):210–214.[CrossRef][Medline]
  20. Classes of recommendations 2000. Part 1: Introduction to the international guidelines 2000 for CPR and ECC. Circulation 2000;102:I-1.[Medline]
  21. American Association of Critical-Care Nurses. Practice alert: Verification of feeding tube placement. www.aacn.org/WD/Practice/Docs/Verification_of_Feeding_Tube_Placement_05-2005.pdf. Accessed August 29, 2008.
  22. Metheny NA, Meert KL, Clouse RE. Complications related to feeding tube placement. Curr Opin Gastroenterol. 2007; 23(2):178–182.[Medline]
  23. Rauen CA, Chulay M, Bridges E, Vollman KM, Arbour R. Seven evidence-based practice habits: putting some sacred cows out to pasture. Crit Care Nurs. 2008;28(2):98–124.




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