Iatrogenic pneumothorax is a patient safety indicator (PSI) condition. It is a traumatic pneumothorax secondary to an invasive procedure or surgery, most commonly being a placement of a subclavian central venous line. Other causes include thoracentesis, pulmonary needle biopsy (transthoracic and transbronchial), nasogastric tube placement, CPR, or positive pressure ventilation.
We have observed an increased number of nasogastric/orogastric (NG/OG) tube insertions causing pneumothorax, especially in COVID-19 patients. Most of these NG/OG tubes are feeding tubes such as Keofeed or DobHoff. A total of 5 cases of pneumothorax caused by insertion of these tubes in the last 24 months was seen, which prompted the initiation of an improvement project.
The incidence of misplacement of nasogastric tubes into the airways ranges from 0.3% to 15% and is more common after chest trauma or mechanical ventilation. This may be due to the inadequate coordination of swallowing while on mechanical ventilation.
Traditionally, auscultation with insufflation of air has been used to verify the adequate placement of NG tubes. However, multiple studies have shown that insufflated air can transmit sounds to the epigastrium, regardless of whether the tube is positioned in the lung, esophagus, stomach, duodenum, or proximal jejunum [1]. Therefore, I searched for an alternative technique for verification that is more accurate and reliable to prevent or decrease the rate of pneumothorax associated with NGT placement.
2-x-ray Approach
This technique begins with inserting the NGT to a distance of 30-35 cm followed by advancement into the stomach only if the X-ray shows intra-esophageal placement of the tube. This safety measure results in a significant decrease in procedure-related pneumothorax (0.09% versus 0.38%, p < 0.05), and a decrease in pneumothorax among patients with an intrabronchial placement (3% versus 27%, p < 0.05) [2]. However, it has not been accommodated broadly as it is time consuming, associated with increased x-ray exposure, and costly.
Observation of Bubbles
Observing for bubbles is an easy way to determine if the tube is in the airways. The presence of bubbling when the exposed end of the tube is submerged in water indicates that the tube is in the airways and should be removed. However, there are instances in which bubbles may not be observed if the tube is occluded with the bronchial walls. In addition, the stomach may contain some air and produce bubbling even with correct positioning [3].
PH testing
The gastric aspirate has a pH ranging from 1-5 while the intestinal or respiratory pH is usually ⩾7.8. Therefore, biochemical testing of pH helps to determine if the NGT is placed inadvertently into the lung. The National Patient Safety Agency in the United Kingdom (UK) recommends this method as the first line to confirm appropriate placement of NGT. In a published review with data from multiple studies examining the pH of gastric aspirates, the sensitivity and specificity for each pH cutoff point was calculated. The cutoff point with the highest sensitivity and specificity for a gastric placement was a pH of ⩽5.5. The drawbacks of this method include the requirement of NGT aspirates (which may not be available in almost half of the cases), the alteration of pH by the time of last feed, and different medications [4].
Capnography
Capnography uses infrared technology for the detection of carbon dioxide in expired air. It can accurately detect the airway placement of NGT and prevent pneumothorax. A meta-analysis was performed for nine trials that investigated the diagnostic accuracy of CO2 detection in detecting airway intubation and differentiating respiratory and GI placement of the NGT. This method was found to detect airway placement of NGTs with 100% accuracy [5].
Ultrasound
Ultrasound can visualize NGT in the esophagus versus the trachea and can detect the NGT in the stomach when used at the epigastrium. It may also be used to obtain a real time image of the NGT’s passage through the esophagus. However, this technique requires elaborate training for users and may be difficult in intubated patients. Additionally, the esophagus can only be viewed via the ultrasound if the esophagus is in a laterotracheal position, and it may be difficult to determine if the NGT is in the trachea in intubated patients [6].
Electromagnetic Tracing
This method uses real-time computer navigation to direct and verify NGT placement. The tip of the NGT contains an electromagnetic transmitter which produces a location signal. Placed at the patient’s xiphoid process, a receiver receives the signal from the tip of the NGT and tracks the movement of the NGT during insertion. The location and path of the tube is shown on a bedside monitor. Compared to the use of X-rays, this method is easy and can identify lung placement of the tube with high accuracy [7].
Iris Technology
The best way is to see where the tube is inserted with direct visualization through a camera. This technology allows for withdrawal of the tube in case of airway insertion. This can be done using iris technology of the Kangaroo feeding tube. Due to the cost, this technique is not widely utilized [8].
Recommendations
The selected technique should be easy to use, reliable, accurate, and inexpensive. Among the available methods for NGT insertion, using capnography is .probably the best technique as it is easily used by nurses, does not expose the patient to more x-raying, and allows for the immediate withdrawal of the tube in case of airway intubation. We advise to insert the tube to a 30 cm mark, connect it to a capnography, and insert it further only if no CO2 signal is detected; otherwise, the tube is withdrawn. In all cases, critical thinking should be used by the nurses and an x-ray should still be obtained for appropriate positioning. Direct distance nose-ear-mid-umbilicus will guide in determining the insertion length of the tube.
REFERENCES
1. Metheny N, Wehrle M, Wiersema L, et al. Testing feeding tube placement: auscultation vs. pH method. Am J Nurs 1998; 98: 37–43.
2. Marderstein EL, Simmons RL, Ochoa JB. Patient safety: effect of institutional protocols on adverse events related to feeding tube placement in the critically ill. J Am Coll Surg. 2004 Jul;199(1):39-47; discussion 47-50. doi: 10.1016/j.jamcollsurg.2004.03.011. PMID: 15217627.
3. Metheny N and Titler M. Assessing placement of feeding tubes. Am J Nurs 2001; 101: 36–46
4. Fernandez R, Chau J, Thompson D, et al. Accuracy of biochemical markers for predicting nasogastric tube placement in adults: a systematic review of diagnostic studies. Int J Nurs Stud 2010; 47: 1037–1046.
5. Chau JP, Lo SH, Thompson DR, et al. Use of end-tidal carbon dioxide detection to determine correct placement of nasogastric tube: a meta-analysis. Int J Nurs Stud 2011; 48: 513–521.
6. Kim HM, So BH, Jeong WJ, et al. The effectiveness of ultrasonography in verifying the placement of a nasogastric tube in patients with low consciousness at an emergency center. Scand J Trauma Resusc Emerg Med 2012; 20: 38–38.
7. Powers J, Luebbehusen M, Spitzer T, et al. Verification of an electromagnetic placement device compared with abdominal radiograph to predict accuracy of feeding tube placement. J Parenter Enteral Nutr 2011; 35: 535–539.
8. Carrara G, Mizzi A, Cozzi S, et al. SUN-PP254: Kangaroo feeding tube with iris technology reduces the risk of pulmonary misplacement in critically ill patients. Clin Nutr 2015; 34: S117– S118.
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