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Confirmation of Nasogastric Tube Placement by Colorimetric Indicator Detection of Carbon Dioxide: A Preliminary Report

Grant Medical Center, Columbus, Ohio

Address reprint requests to: Robert E. Falcone, MD, Regional Trauma Services, Grant Medical Center, 393 East Town Street, Suite 102, Columbus, OH 43215

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 
Background: Inadvertent insertion of nasogastric tubes into the trachea and distal airways is reported to range from 0.3% to 15% of insertions. Critically ill, mechanically ventilated patients are at a higher risk for such complications, some of which can be fatal.

Objective: This preliminary prospective clinical investigation was designed to determine whether a colorimetric carbon dioxide (CO₂) indicator device (Easy-Cap^TM, Nellcor, Inc., Hayward, CA) attached to the proximal end of a small bore feeding tube (FT) would reliably discriminate between those tubes passed into the airways and those passed into the alimentary tract.

Methods: Ten critically ill, mechanically ventilated trauma patients requiring a FT insertion were evaluated. An Easy-Cap^TM device was adapted to the proximal port of each FT. Each patient had one tube inserted per the nasogastric route and then another through the endotracheal tube while the Easy-Cap^TM was observed for color changes consistent with the presence of CO₂.

Results: All transtracheal insertions showed immediate and unambiguous color changes consistent with the presence of CO₂. None of the nasogastric insertions resulted in indicator color changes and all were confirmed with radiography (sensitivity 100%, specificity 100%, accuracy 100%).

Conclusions: This preliminary report suggests colorimetric CO₂ detection accurately and reliably identifies transtracheal FT insertion.

Key words: Capnometry, transtracheal feeding tube insertion

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 
Insertion of nasoenteric tubes is a frequent hospital procedure and their use is nearly universal in critical care unit patients. Inadvertent insertion of these tubes into the trachea and distal airways is reported to range from 0.3% to 15% [1–3]. Critically ill, mechanically ventilated patients are at a higher risk for complications associated with nasoenteric tube insertion including that of insertion into the airways [2,4]. Both airways penetration and introduction of various chemicals into the lung and pleural spaces may occur prior to recognition of tube misplacement and can be fatal [1,5,6].

Capnography is designed to monitor carbon dioxide expiration and is commonly used to verify endotracheal tube placement. Tubes placed within the trachea will allow expiration of carbon dioxide containing gas and will result in a normal capnography tracing. Those tubes inadvertently placed within the esophagus will not. A similar device, Easy-Cap^TM (Nellcor, Inc., Hayward, CA) attaches to the endotracheal tube and utilizes colorimetric indicator material to detect carbon dioxide (CO₂).

This study utilized this phenomenon in a reverse manner to confirm the placement of the nasoenteric tube into the alimentary tract rather than the tracheobronchial tree by demonstrating the absence of CO₂ within the tube lumen.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 
This was a prospective, clinical trial where each patient acted as their own control. Ten critically ill, mechanically ventilated trauma patients who required nasoenteric tubes for feeding were enrolled after informed consent.

An Easy-Cap^TM device was adapted (Fig. 1) and attached in an airtight manner to the proximal end of the nasoenteric tube (Corpak Medsystems, Wheeling, IL). The outlet plug on the Easy Cap^TM was left in place until an insertion depth of 30 cm was obtained. The outlet plug was then removed and the indicator was observed for color changes consistent with the presence or absence of CO₂. The tube was then advanced to its normal depth for nasogastric insertion and a post-insertion radiograph was obtained.

View larger version (40K): [in this window] [in a new window]   Fig. 1. Easy-CapTM feeding tube assembly. Ten French feeding tube attached to an Easy-CapTM with an adapter.

Patient demographics and injury severity were collected including: age, gender, mechanism of injury, Revised Trauma Score (RTS) [7], Injury Severity Score (ISS) [7], Glasgow Coma Score (GOS) [7]. Hospital Length of Stay (LOS), hospital charge, and outcome. Costs were reported as actual institutional cost. Standard formulas for sensitivity, specificity, and accuracy were utilized.

The study protocol was reviewed and approved by the Institutional Review Board at Grant Medical Center prior to the initiation of the study.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 
Ten critically ill, mechanically ventilated patients requiring nutritional support were enrolled in the study following their informed consent. Patients averaged 33.9 years of age, were primarily male (60%), and most commonly suffered a blunt mechanism of injury (90%). Table 1 provides a patient summary. Each patient acted as their own control and were instrumented with a nasoenteric tube in both their upper airway and gastrointestinal tract. No patient suffered complication as a result of this intentional transient upper respiratory tract instrumentation.

All transtracheal insertions showed immediate and unambiguous color changes (yellow to purple) consistent with the presence of carbon dioxide. None of the nasoenteric insertions resulted in indicator color changes.

Use of colorimetric CO₂ detection identified transtracheal insertion of nasoenteric feeding tubes with a sensitivity, specificity, and accuracy of 100% in this group of critically ill, mechanically ventilated trauma patients.

	DISCUSSION:

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 
Critically ill, mechanically ventilated patients are at a higher risk for complications associated with nasoenteric tube insertion including that of insertion into the airways [2,4]. Both airway penetration and introduction of various chemicals into the lung and pleural spaces may occur prior to recognition of tube misplacement and can be fatal [1,6,8,9].

The population studied is typical of the critically ill Trauma Intensive Care population. By design, all patients were mechanically ventilated and in need of nutritional support. The Revised Trauma Score, Glasgow Coma Scale Score and Injury Severity Score are indications of physiologic and anatomic derangement [7]. An average RTS of 5.68, GCS of 9.4 and ISS of 21.8 confirm a seriously ill and injured patient population.

Nasoenteric tube placement is often initially evaluated by aspirating fluid from the proximal port [4] or by insufflating air into the tube and auscultating the abdomen for a "pseudoconfirmatory gurgle" [8]. Both of these maneuvers may yield a false-positive result [4–6,9]. Even pH testing of aspirated fluid is not fail-safe [4].

Radiographic imaging is commonly utilized to confirm tube position and is strongly recommended prior to initiation of enteral feeding or to the instillation of drugs or other material through the tube [3,6]. However, misinterpretation of the radiograph can occur. Hendry et al [6], reported that of 11 patients with malpositioned nasogastric tubes (all of which had radiography for tube placement confirmation) the malposition was not identified in three (27%). Tube positioning in the left costophrenic sulcus is difficult to distinguish from intragastric placement [9] especially on a supine anterior-posterior chest radiograph such as those commonly obtained in the ICU. Capnography may have a useful adjunct in this patient population.

Capnography is designed to monitor carbon dioxide expiration and is commonly used to verify endotracheal tube placement. The results are displayed on a screen as either a waveform or numerically as a percentage of CO₂. The use of capnography for detection of CO₂ emanating from nasoenteric tubes inadvertently placed within the airways has been suggested [10,11]. However, routine use of this specialized instrumentation is infrequent due to its expense, complexity, and lack of availability.

Another method for detection of CO₂ utilizes a colorimetric indicator material enclosed within a small canister which can be attached in-line to the endotracheal tubing (Easy-Cap^TM, Nellcor, Inc., Hayward, CA). This study utilized this phenomenon in a reverse manner to confirm the placement of nasogastric or nasoenteric tubes into the alimentary tract rather than the tracheobronchial tree by demonstrating the absence of CO₂ within the tube lumen.

In this small study population an Easy-Cap^TM provided a rapid unambiguous indication of endotracheal feeding tube placement which was 100% sensitive and 100% specific. The cost compared favorably to radiographic evaluation. This simple rapid and inexpensive technology might find use as an adjunct to radiographic evaluation in the emergency setting when inadvertent endotracheal feeding tube placement is suspected, but not confirmed by radiography. Further study is warranted.

	ACKNOWLEDGMENTS

 
The authors would like to thank H. J. McClung, MD, for sponsoring the presentation of this report at the 37th Annual Meeting of the American College of Nutrition, San Francisco, CA, October 1996.

Received October 1, 1997. Accepted December 1, 1997.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION: REFERENCES

 

1. Bohnker BK, Artman LE, Hoskins WJ: Narrow bore nasogastric feeding tube complications. Nutr Clin Pract 2: 203–209, 1987.
2. Ghahremani GG, Gould RJ: Nasoenteric feeding tubes. Radiographic detection of complications. Dig Dis Sci 31: 574–585, 1986.[Medline]
3. Boyes RJ, Kruse JA: Nasogastric and nasoenteric intubation. Crit Care Clin 8: 865–878, 1992.[Medline]
4. Nakao MA, Killam D, Wilson R: Pneumothorax secondary to inadvertent nasotracheal placement of a nasoenteric tube past a cuffed endotracheal tube. Crit Care Med 11: 210–211, 1983.[Medline]
5. Balogh GJ, Adler SJ, VanderWoude J, Glazer HS, Roper C, Weyman PJ: Pneumothorax as a complication of feeding tube placement. AJR 141: 1275–1277, 1983.[Free Full Text]
6. Hendry PJ, Akyurekli Y, McIntyre R, Quarrington A, Keon WJ: Bronchopleural complications of nasogastric feeding tubes. Crit Care Med 14: 892–894, 1986.[Medline]
7. Wisner DH: History and current status of trauma scoring systems. Arch Surg 127: 111–117, 1992.[Abstract/Free Full Text]
8. Torrington KG, Bowman MA: Fatal hydrothorax and empyema complicating a malpositioned nasogastric tube. Chest 79: 240–242, 1981.[Abstract/Free Full Text]
9. Valentine RJ, Turner WW Jr: Pleural complications of nasoenteric feeding tubes. J Parenter Enteral Nutr 9: 605–607, 1985.[Abstract/Free Full Text]
10. Mercurio P, Levine P: Determining NG tube position. (Letter). Respir Care 30: 999, 1985.
11. D’Souza CR, Kilam SA, D’Souza U, Janzen EP, Sipos RA: Pulmonary complications of feeding tubes: a new technique of insertion and monitoring malposition. Can J Surg 37(5): 404–408, 1994.[Medline]

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