One of the most common procedures in critical care units, emergency rooms, and operating rooms is insertion of a nasogastric tube (NGT). ¹ The NGT is a tube that is placed through the clear nostril, passes through the nasopharynx and esophagus, and ends in the stomach. ²

Placing an NGT in a patient who is mindful and awake is easier than placing an NGT in a patient who is unconscious while under anaesthesia. ³ Nasogastric tubes may be required in unconscious patients for the following reasons: feeding, medication administration, prevention of aspiration pneumonia, stomach decompression (which is ultimately the most important step when a patient is anesthetized for surgery), and removal of stomach contents. NGT insertion is usually required for patients undergoing abdominal and thoracic procedures. Even for very skilled anesthesiologists, inserting an NGT can be highly challenging, as it requires expert hands. ⁴ In anesthetized patients, the gastric tube coils at the piriform sinuses and arytenoid cartilage after passing through the nasal or oral passage, which is commonly seen. ⁵

The standard procedure for inserting the NGT involves doing it blindly, where the patient's head is maintained in a neutral position. ⁶ In addition, standard methods for NGT insertion rely on two distinct types: anatomical and equipment. Anatomical methods include lateral pressure on the neck, cooling of the tube, anterior displacement of the larynx, lifting of the thyroid cartilage, neck flexion, lateral head positioning, anterior displacement of the mandible, and the SORT maneuver. The equipment-based methods include endotracheal tube-guided placement Using Macintosh laryngoscope or Glidescope with the assistance of Magill forceps, ureteral guidewire, I-gel, Ultrasonography, Airway scope, ^{7, 4} etc.

Clinically, the placement of a nasogastric tube can be confirmed by various approaches, such as auscultating the epigastrium and aspirating the contents of the stomach through the NGT, etc. ⁸ Auscultation is the most widely used method for this purpose. However, there are some drawbacks to this approach. Even though the NGT is located in the pleural space, esophagus, or tracheobronchial tree, a whooshing sound can still be heard from the epigastrium. Additional techniques for confirming the location of NGTs include magnetic tracking, X-rays, ultrasound, endoscopy, fluoroscopy, and calorimetric carbon dioxide indicators. ^{9, 10}

Insertion of NGT in anesthetized patients is associated with several problems, as reported in several studies. Minor complications include sinusitis, nosebleeds, tube decompression or rupture, NGT kinking and coiling, or serious conditions including intracranial placement, pulmonary aspiration, laryngeal edema with asphyxia, esophageal or tracheobronchial perforation, and pneumothorax. ¹¹ After an initial failure, repeated attempts typically end in failure because of the NGT coiling, kinking, or knotting tendency. When NGT kinks, it tends to kink again at the same location. As an accuracy method, it is important to verify that the NGT is correctly positioned. The fact that there are numerous approaches with varying established success rates suggests room for improvement. ^{12– 14}

The goal of the current study was to compare the various modified NGT insertion techniques to the standard approach in terms of first-attempt success rate, number of attempts, procedure time, and adverse events.

This study was conducted only after obtaining approval from the Institutional Research Committee, Institutional Ethics Committee, and the CTRI registration. This was a cross-sectional, observational study evaluated at a tertiary care hospital in Manipal, India, over 8 months, from September 2023 to April 2024. The study observed and evaluated various approaches for NGT insertion among anesthetized and intubated patients while ensuring ethical guidelines and participant safety. The aim of this study was to analyze the most common technique of NGT insertion among participants based on the first attempt success rate, number of attempts, and time taken for insertion of NGT and to observe for any occurrence of complications and the technique of confirming proper NGT placement. Based on the proportion outcome (10%) of the NGT techniques, as seen in previous studies, a minimum sample size of 215 patients at a 5% level of significance was recruited for this study. ¹⁵

Patients aged > 18 years undergoing procedures under general anesthesia who required NGT insertion were considered during the preoperative evaluation. Both male and female patients with American Society of Anesthesiologists (ASA) physical status grades I, II, or III were considered. The following exclusion criteria were considered: esophageal disorders, nasal mass or obstruction, upper respiratory tract deformities, bleeding disorders, and anticoagulant use.

After admission, a pre-anesthetic check-up was performed. After discussion of the study procedure and expected complications, written informed consent was obtained from each patient. The demographic characteristics of the participants were collected after anesthetizing and intubating the patient. These details included age, sex, height, weight, body mass index (BMI), ASA status, Mallampati class, and neck movement. An iv cannula of 18-G was established for the intravenous (IV) line either before entering the operating room (OR) or inside the OR. Intravenous fluid was started with lactated Ringer’s solution.

Anesthesia machines and drugs were prepared and kept ready. Premedication drugs, such as inj. Fentanyl, inj. Glycopyrrolate, inj. Atropine was administered through the intravenous route as a single push. The patient was sedated with propofol and muscle relaxation with vecuronium or atracurium. Intubation was performed using a cuffed endotracheal tube (7–8 mm internal diameter according to the patient’s size). After tracheal intubation, ROMSONS FG-14 ( Figure 1), that is, NGT, which is sterile and lubricated, was used. The NGT features a - ball-weighted tip, radiopaque line throughout the tube, luer connector at the proximal end, and length markings as well. ¹⁶ The preferred method of NGT insertion was selected based on the convenience of the anesthesiologist. If the technique failed after several attempts, an alternative method was chosen for the insertion of the NGT, and the preferred method was used for the confirmation of NGT placement.

Thus, our study totally included five different approaches for inserting the NGT in comparison to the traditional method. The first technique was the conventional method. It is a technique of blindly inserting the NGT through a clear nostril where the head is positioned in neutral position, without the need for any other equipment or maneuvers. The appropriate length of NGT placement to reach the stomach was determined by measuring the total distance from the ipsilateral nostril to the ipsilateral tragus and then to the xiphoid process. ^{17– 19} The second technique was frozen NGT. In this method, the tube was stored in a refrigerator in which there was an increase in the rigidity of the tube, making it easier for insertion.

The third technique was the Reverse Sellick maneuver, in which the cricoid cartilage was lifted anteriorly to find space for the insertion of the NGT, while the head was managed in a neutral position. ²⁰ The fourth technique is the oral airway assisted method, in which the oral airway is inserted before the insertion of the NGT to facilitate the smooth insertion of the tube. The fifth technique was the laryngoscope-assisted method, which is a technique similar to the oral airway-assisted method that helps in aiding the tube for faster insertion. The sixth technique involves the head in the lateral position. In this method, a lubricated NGT was inserted through a clear nostril, by slightly turning the head towards the right or left lateral position.

The procedure time (in seconds) was evaluated from the beginning of tube insertion until the NGT placement was confirmed. The auscultation method was used. This was calculated using a timer or stopwatch. The other outcomes included the first-attempt success rate, total number of attempts, and complications such as kinking, coiling, and mucosal bleeding. Hemodynamic parameters, such as heart rate and mean arterial pressure (MAP) i.e., one minute before insertion and after insertion of the NGT, were also noted.

In the present study, a total number of 215 patients were enrolled in the beginning during the time of sample size calculation, after which, due to the availability of time during the data collection, 24 more patients were enrolled, and 239 patients were finalized in the present study, who were scheduled for elective surgeries and required the insertion of NGT.

Of the 239 patients, we observed that six different techniques of inserting NGT were used: the conventional method in 102(42.7%) patients, head in lateral position in only 1(0.4%) patient, frozen NGT in 2(0.8%) patients, Reverse Sellick's maneuver in 19(7.9%) patients, laryngoscope assisted in 11(4.6%) patients, and oral airway assisted in 104(43.5%) patients.

No significant differences were observed in sex, age group, height, weight, and neck movements in any of the six techniques. However, BMI, American Society of Anesthesiologists (ASA) status, and Mallampati class were significant with the six NGT insertion techniques because Mallampati class 4 was found to be more significant with the NGT insertion techniques, and patients who met the criteria for BMI (obese >30) were less likely to require difficult NGT insertion ( Table 1).

As observed in our study, the most practiced and preferred technique in obese patients was the conventional method, and easy insertion of the tube was observed in the oral airway-assisted technique. Therefore, all these factors contributed to the association between NGT insertion techniques.

In contrast to different techniques, out of 102 participants in the conventional method, 16 (15.7%) had mucosal bleeding and 20(19.6%) had NGT coiling, which was the highest among all the methods. The oral airway-assisted technique had 2(1.9%) cases of mucosal bleeding and coiling as the lowest among the methods. “The Likelihood ratio test” was used to compare adverse events according to NGT insertion technique. Hence, mucosal bleeding and coiling were significantly associated (p < 0.05) with NGT insertion techniques ( Table 2).

A shorter procedure time was noted with the frozen technique, followed by the oral airway-assisted technique. Reverse Sellick’s maneuver and the oral airway assisted technique were significantly faster than the conventional method. The head in the lateral position and laryngoscope-assisted methods have subsequently taken a longer procedure time.

Frozen NGT followed by the oral airway assisted technique had the lowest count for the total number of attempts in comparison to the conventional method, whereas the head in the lateral position and laryngoscope-assisted methods showed the highest count for the total number of attempts. One-way ANOVA was used to compare the success rate and duration of the procedure according to the NGT insertion techniques. A difference was observed (p < 0.05) in the success rate and procedure time according to the NGT insertion technique ( Table 3).

In the first attempt, the highest success rate of NGT insertion was observed in the frozen NGT with almost the oral airway-assisted technique, showing significantly better success rates in the first attempt in contrast to the conventional method. The failure was observed to be the highest in the conventional method. In the second attempt, the highest success rates were observed with the head in the lateral position and Reverse Sellick’s maneuver. Meanwhile, the oral airway-assisted technique again showed better success rates in the second attempt than the traditional method of insertion.

Hence, the overall success rates of frozen NGT, oral airway-assisted technique, head in lateral position, and reverse Sellick’s maneuver were all the same, that is, 100%, whereas we compared these rates with the conventional method (91.2%) and laryngoscope-assisted method (72.7%) which was quite less ( Table 4).

The traditional method of NGT insertion involves blindly inserting the NGT through the specified nostril in a neutral position, without the need for any other equipment or manoeuvers. ²¹ In frozen NGT, the tube is stored in the refrigerator, which increases the rigidity of the tube, making it easier for insertion. In the Reverse Sellick’s maneuver, the cricoid cartilage is anteriorly lifted to find space for the insertion of the NGT. Oral airway assistance is a method of inserting the oral airway before inserting the NGT to facilitate smooth insertion of the tube, which is similar to the technique of Laryngoscope assisted method. ^{22– 24}

In the present study, a greater success rate for NGT insertion was evaluated in the frozen NGT (100%), followed by the oral airway-assisted technique (91.3%), and then in the Reverse Sellick’s maneuver (89.5%), compared to the conventional method (56.9%). Ranjan et al. observed frozen NGT and found it to be more successful than the traditional method (84.6% vs. 69.2%). Based on the observations of our present study and Sekhar Ranjan et al., frozen NGT has an overall higher success rate when compared to the conventional method. The increased rigidity of the distal end of the NGT due to freezing facilitates smoother insertion, resulting in a higher success rate. ⁸ Mandal et al. found that the Reverse Sellick’s maneuver achieved a higher rate of success (86%) than the traditional method (56%), which agrees with the results of our study (89.5% vs. 56.9%). Therefore, in contrast to both studies, the overall success rate of the Reverse Sellick’s maneuver is reported to be more than 80%. Thus, a wider opening of the esophagus facilitates the easy passage of the NGT. ¹⁴

This study also included two more methods, that is, head in the lateral position and laryngoscope-assisted method, which had overall success rates of (100% and 72.7%) respectively. Sait et al. conducted a study comparing the head in the lateral position with the McGrath video laryngoscope, which showed an overall higher success rate of (88% and 98%) respectively, when compared to the conventional technique (66%). They used the McGrath video laryngoscope, which helped in direct visualization of the esophagus, facilitating smoother and faster insertion of the NGT. In our study, we observed the use of a Macintosh laryngoscope rather than a video laryngoscope for NGT insertion, which may have results in differ. ¹⁶ In addition, through oral airway support, a new technique for NGT insertion was developed in this study. The success rate of this technique was 100% overall and 91.3% on the first attempt. We observed two patients in our study who had failure of the conventional method even after the fourth attempt, but the clinician was finally successful in the 5 ^th and 6 ^th attempts, respectively, using the laryngoscope-assisted method, as it was necessary to insert the NGT for surgical purposes. Therefore, these alternative methods can be used for the insertion of the NGT in comparison to the traditional method, as these have apparently shown greater success rates. ^{25– 28}

The total time required for NGT insertion was lower in the frozen method (37s), followed by the oral airway assisted method (51.5s). The time required by the traditional method was (112.91s) which was still higher than that of the Reverse Sellick’s maneuver (58.68s). The time spent auscultation and suctioning the contents to verify the tube location is included in the overall process time, as shown above. Even then, the frozen method and the oral airway assisted method took the least time for insertion in comparison to the traditional method. In comparison to other approaches, the Reverse Sellick's maneuver has also taken less time and is a useful technique for NGT insertion. According to our observations, the oral airway-assisted method, which is a more recent technique, often requires the shortest amount of time for insertion, considering the larger number of participants in this approach rather than the frozen method, which had a smaller number of participants. In order to minimize resistance and facilitate tube insertion, the oral airway-assisted approach helps with NGT insertion by preventing the tongue from falling, as we observed in our investigation. Chun et al. found that the standard approach for NGT insertion took more time (120s) when compared to the frozen method (83s) which is similar to our findings. Consequently, compared to other approaches, the frozen method and oral airway assisted method were found to be more effective. ^{6, 10, 14}

Our study also included a comparison of heart rate and blood pressure before and one minute after NGT insertion, but there was no significant difference between the two in contrast to the various NGT approaches. In the present study, 49(20.50%) of 239 patients developed complications. Coiling of the tube (10.9%) and mucosal bleeding (9.2%) were repeated adverse events. Frequent attempts at tube insertion increase the incidence of mucosal bleeding. In comparison to various techniques, mucosal bleeding and coiling were reported to be the highest in the conventional method, followed by the laryngoscope-assisted, oral airway-assisted, and head in the lateral position. We also observed one patient with kinking of the tube using the conventional method, which was not developed in any of the other techniques. The Reverse Sellick's maneuver and frozen NGT did not find any adverse events such as lifting up of the cricoid cartilage, and the advantage of making the tube rigid might aid in smoother insertion of the tube, and the fact that a smaller number of participants might also differ in the results.

The observations in this present study are in line to the results of the study investigated by Rajiv Roy et al. They reported that the Reverse Sellick's maneuver has fewer adverse events than the conventional method. ^{9, 12} According to our newer technique, oral airway assistance helps create space for the insertion of the NGT, which reduces the incidence of adverse events. Thus, in the current study, the oral airway-assisted approach had the lowest frequency of adverse events.

Many techniques exist to verify the location of NGT insertion, including aspirating the tube contents and auscultation at the epigastrium for the sound of whooshing through the deflation of a feeding syringe and using a portable X-ray machine, capnography, and pH paper to evaluate the pH of the aspirate. However, portable X-ray machines and pH paper are considered the gold-standard methods for confirming this position. Several other techniques have been reported for verifying the correct placement, including magnet tracking, endoscopy, ultrasound, fluoroscopy, and a calorimetric carbon dioxide alert system. At the bedside, auscultation is the most accessible technique, with the least amount of technical assistance required. This method was employed in the current investigation to verify the location of the NGT in adult patients who had been anesthetized and intubated. ^{6– 10}

The NGT insertion technique varies from person to person but must be tailored according to the individual’s requirement. Patients who are obese with a BMI >30 and Mallampati classification 3 and 4 may require more than one attempt or a different technique while inserting the nasogastric tube. Studying various NGT insertion methods in intubated and anesthetized patients enhances clinical practice and the literature. Knowledge of techniques with high success rates and fewer complications can help clinicians perform these procedures more routinely.

Ethical clearance was obtained from the Kasturba Medical College and the Kasturba Hospital Institutional Ethics Committee on 14 ^th July 14, 2023 - Approval no: (IEC:434/2023) and adhere to the guidelines under Declaration of Helsinki.