Ultrasonography-Guided Nasogastric Tube Placement and Verification: A Standardized Nursing Protocol

Summary

Ultrasonography provides a safe, radiation-free, bedside method for real-time verification of nasogastric tubes. This evidence-based nursing protocol standardizes indications, acquisition, interpretation, and decision-making, supporting timely gastric access and demonstrating nurses’ capacity to achieve high diagnostic accuracy.

Abstract

This protocol presents a standardized, evidence-based nursing approach for ultrasonography-guided nasogastric tube (NGT) placement and verification in adult patients. The method was developed from a scoping review of 29 studies that examined clinical indications, technical procedures, and decision-making strategies for point-of-care ultrasonography (PoCUS) in NGT confirmation. Across the literature, ultrasonography consistently emerged as a safe, rapid, radiation-free tool for real-time visualization of the tube within the esophagus and stomach. While chest radiography remains the conventional reference standard, the cumulative evidence demonstrates that ultrasound reduces delays in confirming placement and initiating enteral nutrition—an outcome of particular relevance in critically ill or nutritionally vulnerable populations. The protocol describes key technical components, including optimal patient positioning, selection of cervical and epigastric sonographic windows, and the use of linear and convex transducers for accurate visualization. It also integrates direct and indirect verification techniques, such as hyperechoic tube identification and dynamic fogging. Overall, this protocol aims to enhance patient safety, standardize clinical practice, expand nursing autonomy, and support broader adoption of PoCUS for gastric access verification.

Introduction

Nasogastric tube (NGT) insertion is a high-frequency nursing procedure and remains one of the most common sources of preventable adverse events related to enteral therapy in adult patients^1,2. Misplacement of the tube into the respiratory tract or inadequate gastric positioning may result in serious complications, including pneumothorax, aspiration pneumonia, and delayed or unsafe initiation of enteral nutrition^1,2,3. For this reason, accurate and timely verification of tube position is a critical component of patient safety and clinical decision-making in hospital settings^2,3.

Chest radiography is widely recognized as the conventional reference standard for confirming NGT placement^2,3. However, reliance on radiographic confirmation is associated with important limitations, including exposure to ionizing radiation, delays in feeding initiation, increased workload, and dependence on logistical availability of imaging services^3,4. These limitations are particularly relevant in critically ill patients, nutritionally vulnerable populations, and contexts where repeated tube insertions or verifications are required^3,4. Consequently, there has been growing interest in bedside, non-radiological methods that can support safer and more efficient verification processes^5,6,7,8.

Point-of-care ultrasonography (PoCUS) has emerged as a promising technique for NGT placement guidance and verification^5,6,7,8,9,10. The overall goal of this method is to provide real-time, bedside visualization of the tube’s trajectory through the esophagus and its position within the stomach, thereby reducing the risk of respiratory misplacement and minimizing delays in clinical care^5,6. Ultrasonography enables direct anatomical assessment rather than reliance on indirect physiological cues, aligning with contemporary patient safety recommendations that discourage auscultation and blind air insufflation tests due to their poor diagnostic accuracy³.

The rationale for the development and use of ultrasonography in this context is supported by a growing body of evidence demonstrating its feasibility, safety, and diagnostic accuracy across different clinical environments, including intensive care units, emergency departments, and general wards^{7,8,9,10,11,12,13,14}. Importantly, several studies have shown that nurses, after structured training, can perform PoCUS for NGT verification with accuracy comparable to that of physicians^14,15,16. This supports the integration of ultrasound into advanced nursing practice and reinforces its role as an extension of systematic clinical assessment rather than a replacement for professional judgment^5,14.

Compared with alternative bedside techniques, ultrasonography offers several advantages^3,17,18. Unlike auscultation or pH testing of gastric aspirate, ultrasound allows visualization of the tube within the esophagus and gastric antrum, reducing false reassurance associated with indirect methods^3,17,18. In contrast to radiography, PoCUS is radiation-free, repeatable, and immediately available at the bedside, facilitating earlier initiation of enteral nutrition and more timely clinical decisions^6,8,18. Systematic reviews and randomized trials have reported shorter verification times and high sensitivity for gastric placement when ultrasound is used, particularly when cervical and epigastric windows are combined^12,18,19.

Within the wider body of literature, the application of PoCUS for NGT verification aligns with the expanding use of ultrasound for bedside assessment and procedural guidance in nursing and multidisciplinary care^5,6. Frameworks such as the Indication–Acquisition–Interpretation–Decision-Making (I-AIM) model provide a structured approach for integrating PoCUS into clinical workflows and have been successfully applied to gastric ultrasound and other point-of-care applications²⁰. Nevertheless, the literature also highlights significant heterogeneity in scanning techniques, probe selection, interpretation criteria, and decision thresholds, which limits reproducibility and broader implementation^19,21.

To address these gaps, the present work proposes a standardized, nurse-led protocol for ultrasonography-guided NGT placement and verification. This protocol translates the available evidence into operational steps^{7,8,9,10,11,12,13,14}, detailing indications, image acquisition, interpretation of sonographic signs, and clinical decision-making. It is intended for adult patients who require bedside verification and may be particularly appropriate in settings where radiographic confirmation is delayed, repeated verification is anticipated, or radiation exposure should be minimized. However, the method may be less suitable in patients with severe obesity, extensive postoperative anatomical alterations, or excessive bowel gas, where ultrasound windows are suboptimal, and additional confirmation methods may be required^22,23.

By clearly defining its scope, indications, advantages, and limitations, this protocol aims to support clinicians and institutions in determining whether ultrasonography is appropriate for their specific clinical application, while reinforcing patient safety and evidence-based nursing practice^2,5.

Protocol

This study was reviewed and approved by the Institutional Review Board of the Ribeirão Preto College of Nursing, University of São Paulo (CAAE No. 78296623.2.0000.5393). The Institutional Review Board approved the use of ultrasound image data for research purposes and waived the requirement for additional approval related to diagnostic imaging, as no CT scan data were used in this study. Informed consent was obtained from all individuals, and all images included in this work were acquired and used with the participants' explicit authorization.

1. Overview of the operational framework

1. Eligibility criteria
   1. Use this protocol for adult patients requiring bedside verification of NGT placement.
   2. Select clinically stable patients in whom ultrasound windows are expected to be accessible.
   3. Avoid this method or proceed with caution in patients with relative contraindications such as extensive cervical surgical alterations, large neck masses, massive subcutaneous emphysema, and hemodynamic instability requiring immediate radiographic confirmation.
2. Criteria for positive confirmation
   1. Confirm gastric placement only after clearly visualizing at least one direct sonographic sign in both anatomical regions: (1) Visualize the tube within the cervical esophagus during insertion in real-time, and (2) identify a hyperechoic linear or double-line structure within the gastric antrum.
      NOTE: The presence of dynamic fogging following a 10–20 mL air flush may be used as a supportive but not isolated confirmation sign.
3. Criteria for inconclusive examination
   1. Classify the examination as inconclusive if any of the following conditions occur:
   2. The tube is not clearly visualized in either the cervical or epigastric window.
   3. Only indirect signs are present without direct visualization of the tube.
   4. Image quality remains suboptimal despite technical optimization maneuvers.
   5. If only one ultrasound window is positive (either cervical or epigastric) while the second window is negative or inconclusive, the examination should be considered incomplete. In this situation, repeat the scan after technical optimization and reassessment of probe positioning.
      NOTE: If discordant findings persist, radiographic confirmation should be obtained before initiating enteral feeding.
4. Criteria for escalation to radiographic confirmation
   1. Escalate to immediate radiographic confirmation if a) ultrasound findings are inconclusive; b) clinical findings conflict with ultrasound images; c) the patient presents a high risk of pulmonary misplacement (e.g., altered airway reflexes, mechanical ventilation), and adequate acoustic windows cannot be obtained after troubleshooting maneuvers.
5. Operator competency and framework
   NOTE: The protocol assumes prior structured PoCUS training and familiarity with cervical and gastric sonoanatomy. The protocol uses an operational adaptation of the Indication–Acquisition–Interpretation–Decision-Making (I-AIM) framework for PoCUS²⁰.
   1. Ensure competency validation before implementing independent clinical use in institutions.
   2. Apply the I-AIM framework exclusively as an organizational structure and translate each component into explicit, step-by-step instructions to ensure reproducibility in clinical practice.

2. Ultrasound system preparation

1. Turn on the ultrasound device and select the appropriate presets:
   1. Select the Soft tissues or Neck preset and use a high-frequency linear transducer (typically 6–13 MHz) for cervical esophageal imaging.
   2. Select the Abdominal preset and use a low-frequency convex transducer (typically 2–5 MHz) for epigastric scanning of the gastric antrum.
2. Ensure the device is connected to a reliable power supply or has an adequate battery charge.
3. Position the machine on the right side of the patient, in alignment with typical scanning ergonomics as used in literature, to facilitate ease of operator movement.

3. Patient and environment preparation

1. Place the patient in a supine position.
2. For cervical scanning, ensure the head is in a neutral or slightly extended posture to elongate the anterior neck and optimize esophageal visualization.
3. For epigastric scanning, ensure the upper abdomen is exposed from the xiphoid process to the left costal margin.
4. Adjust ambient light by dimming the overhead lighting to improve screen visibility.
5. Position the ultrasound monitor directly in the operator’s line of sight to maintain real-time coordination during NGT insertion and scanning.
6. Determine the estimated insertion depth of the NGT using a standardized external measurement method consistent with institutional policy prior to ultrasound confirmation.
7. Use the nose–ear–xiphoid (NEX) or nose–ear–mid-umbilicus (NEMU) technique as indicated; however, preferentially adopt validated corrected formulas (e.g., modified Hanson-based calculations) when available, given the documented limitations of the standard NEX approach.
8. Mark the selected measurement on the tube prior to insertion to guide advancement to the estimated gastric position. Perform ultrasound scanning during tube advancement and/or immediately after reaching the predetermined insertion depth.
   NOTE: Do not use ultrasound confirmation as a substitute for appropriate initial length estimation. Use ultrasound as a real-time method to verify esophageal passage and final intragastric positioning.
9. Safety and infection control considerations
   1. Follow standard infection prevention precautions throughout the procedure. Perform hand hygiene before and after patient contact and use appropriate personal protective equipment (PPE) in accordance with institutional and isolation protocols.
   2. Clean and disinfect the ultrasound transducer before and after each use in accordance with manufacturer recommendations and institutional infection control policies. Use a single-use probe cover when scanning patients under contact or droplet precautions.
   3. Maintain continuous monitoring of respiratory status and hemodynamic stability during tube insertion and ultrasound scanning.
   4. Adjust the supine position if the patient demonstrates intolerance, respiratory compromise, or increased aspiration risk. In high-risk patients, consider semi-recumbent positioning (30–45° head elevation) when clinically feasible.
   5. Discard all single-use consumables (e.g., gloves, syringes, gauze, and probe cover) after completion of the procedure in accordance with institutional waste management and biosafety policies.
   6. Handle ultrasound gel containers according to local infection prevention guidelines, and do not share multi-dose containers between isolation rooms.

4. Perform cervical esophageal scanning (High-Frequency Linear Probe, 6–13 MHz)

1. Apply an adequate amount of ultrasound gel to the linear transducer to avoid air interference and ensure proper acoustic coupling.
2. Place the probe transversely on the neck, just superior to the suprasternal notch and lateral to the trachea, at the level of the cricoid cartilage.
3. Ensure the probe marker corresponds to the left side of the ultrasound screen.
4. Identify the following anatomical landmarks (Figure 1):
   1. Trachea: Hyperechoic anterior wall with posterior acoustic shadowing.
   2. Esophagus: Typically located posterior and slightly left of the trachea, compressible, and may appear hypoechoic unless distended.
   3. Carotid artery and internal jugular vein: Lateral reference points to confirm orientation.
5. Adjust the settings to improve visualization of the esophageal lumen: a) Set depth to 3–5 cm for cervical structures; b) Set gain to a moderate level to avoid saturation that obscures hyperechoic tube patterns; c) Optimize focus to enhance image sharpness.
6. During NGT insertion, maintain real-time visualization of the advancing tube. Observe for the appearance of a hyperechoic linear structure within the esophagus (Figure 3 and Supplemental Video S1).
7. Instruct a cooperative patient to swallow during tube advancement to enhance esophageal peristalsis and facilitate identification of the characteristic ultrasonographic “flash” artifact associated with esophageal passage.

5. Perform epigastric/gastric antrum scanning (Low-frequency convex probe, 2–5 MHz)

1. Position the convex probe
   1. Select the convex transducer and apply adequate gel.
   2. Position the probe in longitudinal orientation over the epigastric or subxiphoid region, with the probe marker directed toward the patient’s head.
2. Identify Anatomical Landmarks (Figure 2)
   1. Identify the left lobe of the liver as the anterior acoustic window.
   2. Identify the gastric antrum posterior to the liver.
   3. Confirm the presence of the aorta and the superior mesenteric artery as posterior structures relative to the gastric antrum.
3. Adjust the following imaging parameters: a) Set depth to 3–4 cm for optimal visualization of the gastric antrum; b) Optimize gain for clear visualization of the stomach wall and luminal contents; c) Position focus at or slightly below the depth of the gastric antrum.
4. Confirm Gastric Placement
   1. Once the NGT reaches its target depth, observe for the appearance of a hyperechoic linear or double-line structure within the gastric antrum (Supplemental Videos S2 and S3).
   2. Optionally, inject 10–20 mL of air rapidly through the tube using a syringe while maintaining real-time ultrasound visualization of the gastric antrum. Observe the gastric lumen for transient turbulent echogenicity or “dynamic fogging,” characterized by a brief hyperechoic cloud or swirling artifact appearing immediately after air injection. If no turbulence is observed, reassess probe positioning and repeat the maneuver once. If the sign remains absent or visualization is uncertain, do not use this finding as confirmation, and rely on direct tube visualization or proceed to additional verification methods. (Supplemental Video S4).

6. Optimize image quality (Knobology)

1. Continuously adjust the following controls to ensure high-quality image acquisition:
   1. Depth: Adjust to frame the esophagus or gastric antrum centrally.
   2. Gain: Balance to avoid under- or over-illumination of the image.
   3. Time Gain Compensation (TGC): Adjust to normalize brightness throughout the image.
   4. Focal zone: Align with the deepest structure of interest, typically the gastric antrum.
2. Image Capture and Documentation
   1. Once optimal visualization is achieved, press Freeze and capture representative images: a) Tube within the esophagus (transverse and/or longitudinal views). b) Tube within the gastric antrum (longitudinal view).
   2. Label images according to institutional and research standards (e.g., “NGT visualized within the cervical esophagus and the gastric antrum”).
   3. Save captured images in the patient record.

7. Troubleshooting during acquisition

1. If the esophagus is not visible, tilt or slide the probe laterally to adjust its position and rotate the probe slightly to differentiate the esophagus from vascular structures. If the patient is cooperative, ask them to swallow and observe the flash artifact within the esophagus.
2. If visualization of the gastric antrum is impaired, apply gentle epigastric pressure to improve visualization. Re-scan from the left upper quadrant if necessary. Reduce bowel gas artifact by brief patient repositioning.
3. For patients with obesity, postoperative anatomical changes, or reduced cervical mobility, anticipate technically difficult windows. Use both cervical and epigastric views and consider using a non-radiological adjunct, such as gastric aspirate pH measurement, to support verification.
   NOTE: If direct visualization of the tube cannot be achieved after optimization maneuvers in both cervical and epigastric windows, the examination should be classified as technically difficult and considered insufficient for independent confirmation.

Results

In successful examinations, the cervical esophageal window allowed clear visualization of the NGT as a hyperechoic linear or double-line structure within the esophageal lumen, typically posterior and slightly lateral to the trachea (Supplemental Video S1). During real-time insertion, dynamic observation of tube advancement through the cervical esophagus confirmed correct esophageal passage and excluded airway misplacement.

At the epigastric window, correct gastric placement wa...

Discussion

The present protocol provides a structured, reproducible approach to ultrasonography-guided NGT placement and verification, translating established sonographic principles into actionable steps for bedside practice. One of the most critical steps in the protocol is the systematic acquisition of both cervical and epigastric windows, as reliance on a single anatomical window may lead to false reassurance or incomplete assessment. Continuous real-time visualization during tube advancement, particularly at the cervical esopha...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Ultrasound system (portable or bedside)	VINNO Technology (Suzhou) Co., Ltd	8000166	System capable of abdominal and superficial imaging
Linear ultrasound probe (6–13 MHz)	VINNO Technology (Suzhou) Co., Ltd	8000166	Used for cervical window visualization
Curvilinear ultrasound probe (2–5 MHz)	VINNO Technology (Suzhou) Co., Ltd	N/A	Used for epigastric/gastric window
Nasogastric tube (adult)	Medicone	80020550040	Standard enteral feeding tube
20 mL syringe	General	N/A	Used for optional air flush maneuver
Ultrasound gel	General	N/A	Acoustic coupling for ultrasound examination
Medical gloves	General	3600714832	Standard infection control precautions
Lubricant gel	General	N/A	Facilitates nasogastric tube insertion
Adhesive tape or tube fixation device	General	N/A	Secures the tube after placement
Patient bed or examination stretcher	General	N/A	Patient positioned in semi-recumbent position