This study was supported, in part, by the National Institutes of Health/National Cancer Institute (Bethesda, Maryland) Cancer Support Grant P30 CA008748.

This scanning protocol is for clinical training and has not been published elsewhere. The ultrasound images were obtained from a volunteer and de-identified. As per the institutional guidelines, this protocol is beyond the Common Rule and FDA definition of the human research subject, and formal IRB approval is not required.
1. Transducer and image optimization
<ol>
	<li>Use a linear array 12-4 MHz transducer. This is a high-frequency transducer for superficial imaging structures.</li>
	<li>Practice holding the transducer at a 90&#176; angle to the skin with both hands and standing on both sides of the patient, which may be necessary when working in a limited space. Apply light pressure on the neck. Otherwise, the image becomes distorted.</li>
	<li>Practice transducer manipulation with fine movements for image optimization.
	<ol>
		<li>Small adjustments are often required to obtain a better image. Try holding the probe like a pencil. Do not rest the hand part on the neck, as this distorts the image.</li>
	</ol>
	</li>
	<li>Practice using different models of ultrasound machines with different linear arrays, 12-4 MHz or 12-5 MHz, 13-6 MHz, or curvilinear C5-1 MHz transducers to adjust to different weights.</li>
	<li>Practice image optimization.
	<ol>
		<li>Practice knobology manipulation for an optimal image using focus, gain, time compensation (TGC), depth, and zoom. 
		NOTE: The ideal depth is 3.5-4 cm.
		<ol>
			<li>Avoid too much and too little gain, which creates a poor image.</li>
			<li>Use time gain compensation (TGC) to adjust the near/far field gain. This fine-tunes the gain at a specific grayscale depth for an optimal image.</li>
			<li>Zoom in to the desired area of interest.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Practice freezing, measuring, and acquiring the images.</li>
</ol>
2. Patient position
<ol>
	<li>Place the patient in a supine position without a pillow.</li>
	<li>Ask the patient to maintain the head and neck in a neutral position to ensure standardization.The sniffing position may be unattainable in head and neck cancer patients, and the neutral position achieves the best measurements.</li>
	<li>Ask the patient to rest their tongue on the lower incisors. The tongue position within the mouth changes the thickness of the soft tissues; therefore, the tongue should always be in the same position during ultrasound examination to ensure consistency.</li>
</ol>
3. Transducer technique for image optimization
<ol>
	<li>Apply a gel medium between the transducer and the skin so that there is no air in between. 
	NOTE: Ultrasound waves do not travel through the air.</li>
	<li>Place the transducer transversely on the anterior neck with minimal pressure, and preserve skin contact. 
	NOTE: Pressure applied to the anterior neck can narrow the upper airway, change the tissue measurements, elicit coughing, and make the patient uncomfortable.</li>
	<li>Place the transducer midline on the central axis in the transverse position.</li>
	<li>Start from the submandibular space, and, with slow fine movements, move the transducer caudally. 
	&#8203;NOTE: The superficial location of the larynx helps in the identification of its structures. The anterior neck soft tissue thickness is obtained at five points.</li>
</ol>
4. Hyomental distance (HMD, Figure 1)
<ol>
	<li>Place the transducer longitudinally in the submental space along the body&#39;s central axis to obtain a submandibular image. 
	NOTE: The floor of the mouth image shows a fine tissue echogenicity between the acoustic shadows of the mentum and the hyoid bone. The hard palate is hyperechoic and is depicted as a white line.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the outer border of the mentum to the hyoid bone. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Rotate the transducer in the transverse position, and place it over the central axis of the neck.</li>
	<li>Manipulate the transducer with fine slow movements caudally to visualize the following structures7.</li>
</ol>
5. Thyrohyoid membrane (THM, Figure 2)
<ol>
	<li>Palpate the thyroid cartilage and the hyoid bone, and place the transducer in between in the transverse position, making sure to stay in the central axis of the neck. 
	NOTE: The thyrohyoid membrane expands from the caudal border of the hyoid bone to the cephalad border of the thyroid cartilage. The epiglottis comes into view as a hypoechoic curvilinear structure, and is a dark space.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the anterior border of the epiglottis in the center. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the transducer 1 cm to the right.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure the distance from the skin to the anterior border of the epiglottis. The distance will pop up in centimeters (cm) on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the transducer 1 cm to the left of the center, and repeat steps 5.6-5.8.</li>
	<li>Average the three measurements to obtain the THM8.</li>
</ol>
6. Distance from the skin to the epiglottis (DSE, Figure 3)
<ol>
	<li>Keep the transducer in the same position, and stay in the neck&#39;s central axis. 
	NOTE: The epiglottis should be in view. The epiglottis is a hypoechoic curvilinear structure seen as a dark space, and it remains so throughout the patient&#39;s life. Posteriorly, the air mucosal interface is a bright white line.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the center of the bright white line. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the probe 1 cm left of the midline.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the bright white line. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the transducer 1 cm to the right of the midline, and repeat steps 6.6-6.8.</li>
	<li>Average the three measurements to obtain the DSE9.</li>
</ol>
7. Distance from the skin to the hyoid bone (SHB, Figure 4)
<ol>
	<li>Angle the transducer tail slightly down (about 20&#176;), palpate the hyoid bone, and place the transducer directly over the hyoid bone, making sure to stay in the central axis of the neck. 
	NOTE: The hyoid bone is seen as a bright echogenic line curved upside down. Below is a hypoechoic shadow.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the center of the hyoid bone. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the probe 1 cm lateral to the midline on the left.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the hyoid bone. A distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Move the transducer 1 cm to the right of the midline, and repeat steps 7.6-7.8</li>
	<li>Average the three measurements to obtain the SHB distance10.</li>
</ol>
8. Distance from the skin to the vocal cords (SVC, Figure 5)
<ol>
	<li>Place the ultrasound probe transversely over the thyroid cartilage, making sure to stay in the central axis of the neck. 
	NOTE: The thyroid cartilage is visualized as a large upside-down V-shaped structure with fine tissue echogenicity. The vocal cords are two triangular shapes within the V-shaped structure.</li>
	<li>Click on Freeze.</li>
	<li>Click on Measure. Measure from the skin to the upper border of the right vocal cord. The distance in centimeters (cm) will pop up on the screen.</li>
	<li>Click on Acquire.</li>
	<li>Repeat steps 8.2-8.4 on the left vocal cord.</li>
	<li>Average the two measurements to obtain the SVC11.</li>
</ol>

<ol>
	<li>Apfelbaum, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=American+Society+of+Anesthesiologists+Practice+Guidelines+for+Management+of+the+Difficult+Airway.">American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway.</a> Anesthesiology. 136 (1), 31-81 (2022).</li><li>Ji, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+between+modified+LEMON+score+and+intubation+difficulty+in+adult+trauma+patients+undergoing+emergency+surgery.">Correlation between modified LEMON score and intubation difficulty in adult trauma patients undergoing emergency surgery.</a> World Journal of Emergency Surgery. 13, 33 (2018).</li><li>Hall, E. A., Showaihi, I., Shofer, F. S., Panebianco, N. L., Dean, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+evaluation+of+the+airway+in+the+ED:+A+feasibility+study.">Ultrasound evaluation of the airway in the ED: A feasibility study.</a> Critical Ultrasound Journal. 10 (1), 3 (2018).</li><li>Chou, H. -. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracheal+rapid+ultrasound+exam+(T.R.U.E.)+for+confirming+endotracheal+tube+placement+during+emergency+intubation.">Tracheal rapid ultrasound exam (T.R.U.E.) for confirming endotracheal tube placement during emergency intubation.</a> Resuscitation. 82 (10), 1279-1284 (2011).</li><li>Sotoodehnia, M., Rafiemanesh, H., Mirfazaelian, H., Safaie, A., Baratloo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonography+indicators+for+predicting+difficult+intubation:+A+systematic+review+and+meta-analysis.">Ultrasonography indicators for predicting difficult intubation: A systematic review and meta-analysis.</a> BMC Emergency Medicine. 21 (1), 76 (2021).</li><li>Prasad, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+sonography+and+computed+tomography+as+imaging+tools+for+assessment+of+airway+structures.">Comparison of sonography and computed tomography as imaging tools for assessment of airway structures.</a> Journal of Ultrasound in Medicine. 30 (7), 965-972 (2011).</li><li>Andruszkiewicz, P., Wojtczak, J., Sobczyk, D., Stach, O., Kowalik, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effectiveness+and+validity+of+sonographic+upper+airway+evaluation+to+predict+difficult+laryngoscopy.">Effectiveness and validity of sonographic upper airway evaluation to predict difficult laryngoscopy.</a> Journal of Ultrasound in Medicine. 35 (10), 2243-2252 (2016).</li><li>Adhikari, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pilot+study+to+determine+the+utility+of+point-of-care+ultrasound+in+assessing+difficult+laryngoscopy.">Pilot study to determine the utility of point-of-care ultrasound in assessing difficult laryngoscopy.</a> Academic Emergency Medicine. 18 (7), 754-758 (2011).</li><li>Ezri, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+difficult+laryngoscopy+in+obese+patients+by+ultrasound+quantification+of+anterior+neck+soft+tissue.">Prediction of difficult laryngoscopy in obese patients by ultrasound quantification of anterior neck soft tissue.</a> Anaesthesia. 58 (11), 1111-1114 (2003).</li><li>Yadav, N. K., Rudingwa, P., Mishra, S. K., Pannerselvam, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+measurement+of+anterior+neck+soft+tissue+and+tongue+thickness+to+predict+difficult+laryngoscopy+-+An+observational+analytical+study.">Ultrasound measurement of anterior neck soft tissue and tongue thickness to predict difficult laryngoscopy - An observational analytical study.</a> Indian Journal of Anaesthesia. 63 (8), 629-634 (2019).</li><li>Martinez-Garcia, A., Guerrero-Orriach, J. L., Pino-Galvez, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonography+for+predicting+difficult+laryngoscopy.+Getting+closer.">Ultrasonography for predicting difficult laryngoscopy. Getting closer.</a> Journal of Clinical Monitoring and Computing. 35 (2), 269-277 (2020).</li><li>Carsetti, A., Sorbello, M., Adrario, E., Donati, A., Falcetta, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Airway+ultrasound+as+predictor+of+difficult+direct+laryngoscopy:+A+systematic+review+and+meta-analysis.">Airway ultrasound as predictor of difficult direct laryngoscopy: A systematic review and meta-analysis.</a> Anesthesia and Analgesia. 134 (4), 740-750 (2022).</li><li>Petrisor, C., Szabo, R., Constantinescu, C., Prie, A., Hagau, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound-based+assessment+of+hyomental+distances+in+neutral,+ramped,+and+maximum+hyperextended+positions,+and+derived+ratios,+for+the+prediction+of+difficult+airway+in+the+obese+population:+A+pilot+diagnostic+accuracy+study.">Ultrasound-based assessment of hyomental distances in neutral, ramped, and maximum hyperextended positions, and derived ratios, for the prediction of difficult airway in the obese population: A pilot diagnostic accuracy study.</a> Anaesthesiology Intensive Therapy. 50 (2), 110-116 (2018).</li><li>Reddy, P. B., Punetha, P., Chalam, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonography+-+A+viable+tool+for+airway+assessment.">Ultrasonography - A viable tool for airway assessment.</a> Indian Journal of Anaesthesia. 60 (11), 807-813 (2016).</li><li>Wu, J., Dong, J., Ding, Y., Zheng, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+anterior+neck+soft+tissue+quantifications+by+ultrasound+in+predicting+difficult+laryngoscopy.">Role of anterior neck soft tissue quantifications by ultrasound in predicting difficult laryngoscopy.</a> Medical Science Monitor. 20, 2343-2350 (2014).</li><li>Pinto, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predicting+difficult+laryngoscopy+using+ultrasound+measurement+of+the+distance+from+skin+to+the+epiglottis.">Predicting difficult laryngoscopy using ultrasound measurement of the distance from skin to the epiglottis.</a> Journal of Critical Care. 33, 26-31 (2016).</li><li>Falcetta, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+two+neck+ultrasound+measurements+as+predictors+of+difficult+direct+laryngoscopy:+A+prospective+observational+study.">Evaluation of two neck ultrasound measurements as predictors of difficult direct laryngoscopy: A prospective observational study.</a> European Journal of Anaesthesiology. 35 (8), 605-612 (2018).</li><li>Chalumeau-Lemoine, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Results+of+short-term+training+na&#239;ve+physicians+in+focused+general+ultrasonography+in+an+intensive-care+unit.">Results of short-term training na&#239;ve physicians in focused general ultrasonography in an intensive-care unit.</a> Intensive Care Medicine. 35 (10), 1767-1771 (2009).</li></ol>

The author has nothing to disclose.

Ultrasound of the airway is an effective methodology to examine the airway. The goal is to incorporate airway examination into daily practice to give additive value to the standard pre-anesthetic assessment of the airway before the induction of anesthesia.
It is best to start the scanning protocol from the submandibular space with the transducer positioned along the long axis of the body - the sagittal plane. From there, the transducer is turned in the transverse position along the midline and slowly moved caudally as each parameter comes into view. All the steps should be performed consistently and systemically, and focused training and practice are critical to maintaining good images for future studies.
Alternatively, the scanning protocol starts at the sternal notch, and the tracheal rings will come into view; at this point, one should slowly move the transducer cephalad as the ultrasound parameters focus into view. The scanning sequence can be organized and the order of the views can be changed depending on the sonographer&#39;s experience. The submandibular space is best seen with the curvilinear C5-1 MHz transducer, which gives a broad view. A high-frequency linear array 12-4 MHz transducer can obtain all the airway images if only one transducer is available.
The most important aspect of this technique is the patient position. The patient should be supine, with a neutral head position and without a pillow. Small cephalad and caudal movements of the transducer are often necessary to obtain the best images. If specific parameters are difficult to visualize, the sonographer can start over from the most cephalad position with the transducer positioned transversely in the midline and slowly move the transducer caudally.
The linear array L12-4 MHz transducer is a high-frequency transducer that reaches 8 cm in depth. The lines on the right of the ultrasound screen depict the depth to which the ultrasound waves will reach. The depth knob adjusts between shallow or deep depth. A good depth is 3.5-4 cm. Changing the gain knob up or down alters the overall gain, thus making the picture brighter or darker. The gain should be adjusted for the optimal visualization of all the structures. The near/far field and time gain compensation (TGC) fine-tune and adjust the gain at a specific depth in the grayscale ultrasound images. The TGC was middle negative to middle positive from the top to the bottom rows of the narrative review images. The focus knob adjusts the area of interest of the ultrasound image.
The limitations of this technique include the availability of ultrasound and the required training in basic airway ultrasound. Chalumeau-Lemoine et al. concluded that a comprehensive training of 8.5 h, with 2.5 h of didactic sessions and three 2 h hands-on sessions, allowed individuals to achieve competency in essential ultrasound examination, even without prior knowledge of the ultrasound technique18. Additionally, interpretation improved with experience18. A consensus or guidelines about the parameters&#39; cutoff values do not exist. The different populations studied can explain this incongruity, and the results cannot be generalized to other groups. Ultrasound measurements are in centimeters (cm), and the pressure applied to the anterior neck may alter the measured values. A minimal pressure to the anterior neck that allows for the maintenance of skin contact should be applied. A higher risk of difficult laryngoscopy in obese or pregnant patients precluded their inclusion in these study groups.
The thickness of the anterior neck measured by ultrasound has superior sensitivity and specificity than traditional airway assessment in predicting difficult laryngoscopy. Combined with standard bedside clinical assessments, an ultrasound examination of the anterior neck can significantly improve the prediction of difficult laryngoscopy. To date, the studies are small, and there is no common use of ultrasound in airway management other than to confirm the placement of an endotracheal tube or to localize the cricothyroid membrane in case of an emergent surgical airway.
Despite the uncertainty, in the future, portable and handheld ultrasound devices are likely to be accepted as an adjunct to clinical examinations for immediate bedside assessment and management, just as the stethoscope, mobile airway, and other management devices were established previously. This acceptance involves setting up standard protocols and incorporating ultrasound into airway management guidelines. Quality assessment and improved patient safety require training and regular simulation education. Three-dimensional and handheld ultrasound devices are likely to push the boundaries for quality images and the widespread accessibility of point-of-care devices.
Clinical airway examination by the LEMON method is an external assessment of the airway above the hyoid bone. Ultrasound examination is the internal assessment of the structures below the hyoid bone. The study results show that ultrasound-based airway management could be a valuable adjunct to traditional bedside assessment and a helpful tool in predicting difficult airways. The integration of POCUS is increasingly becoming the mainstay for difficult airway management. Its novelty and portability mean that it is feasible to integrate POCUS in the perioperative setting.

Airway management is a crucial part of a patient&#39;s perioperative care and is an essential skill for an anesthesiologist. Failure to secure a proper airway can result in unplanned intensive care admissions and complications, prolonged hospital stays, and an increased risk of brain damage and death. The American Society of Anesthesiologists (ASA) 2022 difficult airway task force updated the definition of a difficult airway to include the following: difficult mask ventilation, a difficult laryngoscopy view, a high number of intubation attempts, the use of advanced airway adjuncts, and difficult extubation or ventilation1. The visual assessment of the airway before intubation includes looking for, evaluating, and allocating a Mallampati score, observing for signs of obstruction, and assessing the neck mobility. This is commonly known as the LEMON method. Additional assessments include radiographic, oropharyngeal, or external anatomic airway structure assessments and the upper lip bite test2.&#160;No method is without limitations as a predictor of significant intubation difficulty. These many quality assessments may explain why the incidence of difficult airways varies from 5% to 22% and the positive predictive value (PPV) is low. A recent meta-analysis showed a low prevalence of difficult intubation in patients with a Mallampati score of III or IV, making the Mallampatti scoring system less sensitive and specific than measured ultrasound parameters3. Images of the airway provided on ultrasound are comparable to radiography, rendering it an appealing alternative. Ultrasound of the airway has been gaining momentum as an adjunct in airway management since point-of-care ultrasound protocols were introduced and shown to be supported by clinical data based on identifying endotracheal tube placement in trauma patients4. Ultrasound provides the clinician with a dynamic anatomical assessment, which is impossible with clinical examination alone.
Studies indicate the added value of specific ultrasound parameters in determining a difficult laryngoscopy visualization. The feasibility of point-of-care ultrasound (POCUS) for airway management in the perioperative setting is still an area of great interest. Ultrasound reliably images all the structures visualized by CT, and infrahyoid airway structures agree well with the parameters measured by CT5. Various ultrasound measurements at different levels of the neck have been studied. The following measurements correlate with difficult direct laryngoscopy: (1) the hyomental distance (HMD); (2) the thyrohyoid membrane (THM); (3) the distance from the skin to the epiglottis (DSE); (4) the distance from the skin to the hyoid bone (SHB); and (5) the distance from the skin to the vocal cords (SVC). This method is suitable for general populations and specific populations, such as those with obesity. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck mobility from different causes preclude using ultrasound to assess the airway.
This narrative review discusses the significant ultrasound parameters in the POCUS of the airway and supplies training suggestions that can be used in everyday practice. Ultrasound is simple, portable, easy, and has a short learning curve.
Sound above a frequency of 20 MHz is called ultrasound, and medical imaging uses 2-15 MHz. Ultrasound waves are transmitted and received by an ultrasound transducer, commonly called an ultrasound probe. The resistance of the ultrasound wave traveling through tissue is called the acoustic impedance. Ultrasound waves reflect from the tissue-air interface back to the transducer, and different tissues have different acoustic impedances. Bone gives a strong echo, meaning it is referred to as being hyperechoic and appears white. In addition, bone absorbs the ultrasound waves, and nothing passes beyond it. This phenomenon is described as acoustic shadowing. Airway structures that contain cartilage create a small echo; they are described as hypoechoic structures and appear dark on the ultrasound image. As calcifications develop with aging, these structures appear more echogenic5.&#160;A more heterogenic appearance is seen with muscle and connective tissue. Glandular tissue appears brighter, meaning this tissue is hyperechoic. It is essential to understand the air-tissue border concept. The ultrasound waves do not travel through the air but return to the transducer, creating a strong reflection. The returning echo signal is a dispersion artifact - a reverberation causing multiple white lines. The ultrasound beam at the air-mucosa interface creates a bright white line. Denser tissue appears brighter on the screen, and the structures beyond cannot be observed. Clinically, only the tissue from the skin to the anterior luminal surface of solid tissue is visualized. The posterior wall of the pharynx and larynx cannot be visualized. Acoustic shadowing reflects the ultrasound beams returning to the probe6.
The ultrasound transducers include a curved low-frequency (C5-1 MHz) transducer, a high-frequency linear array (L12-4 MHz), (L12-5) MHz, or&#160;(L13-6 MHz) transducer. The airway structures are superficial within 2-3 cm from the skin but are deeper in obese patients due to the increased anterior neck fat tissue. The curved low-frequency C5-1 MHz transducer displays a broader field of view for a better submandibular view. If only one transducer is available, then the high-frequency linear array performs all ultrasound examinations relevant to the airway assessment. The transducer must have complete contact with the skin. A generous amount of conductive gel is needed to maintain the skin contact. In males, it is challenging to prevent air from being trapped between the skin and the transducer due to the prominent thyroid cartilage. In this instance, minimal caudal and cranial adjustments can be used to optimize the image.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Gel-Lubricant jelly</td>
			<td>MediChoice</td>
			<td>13143 gram, LUB Sterile</td>
			<td>Bacteriostatic,water soluble-alcohol free.</td>
		</tr>
		<tr>
			<td>Philips SPARQ Point of Care System</td>
			<td>Philips</td>
			<td>Transducer L12-4 MHz</td>
			<td>Broadband linear. 128elements. 38.4 mm.</td>
		</tr>
	</tbody>
</table>

point-of-care ultrasound: a review of ultrasound parameters for predicting difficult airways

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

This paper aims to provide significant ultrasound parameters that are predictive of a difficult laryngoscopy. To date, 30 studies have analyzed several different ultrasound parameters. Two meta-analyses have identified the five most studied parameters that significantly differ between easy and difficult direct laryngoscopy views and have higher sensitivity and specificity than the classic Mallampatti classification12. This narrative review follows the scanning protocols from the studies shown in Table 1 and Table 2.
Distance from the skin to the epiglottis (DSE) 
To obtain the DSE at the level of the thyroid membrane, the patient is placed supine, with the head and neck in a neutral position and without a pillow. The transducer is placed transversely along the anterior surface of the neck and is moved from the floor of the mouth to the sternal notch level. The epiglottis is a hypoechoic (dark) curvilinear structure visualized via the thyroid membrane anteriorly and the bright air-mucosa interface posteriorly. The transducer tail is slightly angled cephalad or/and caudal for optimal visualization. Swallowing enables a mobile view of the epiglottis. The measurements are from the skin to the posterior border of the epiglottis along the central axis and 1 cm to the left and right and are averaged.
A recent meta-analysis by Carsetti et al. of 15 eligible studies found the distance from the skin to the epiglottis (DSE) was the parameter that correlated the most with a difficult direct laryngoscopy12. The DSE was higher in patients with a higher Cormack-Lehane laryngoscopy grade. The average DSE ultrasound measurement was &#62;2-2.5 cm, with a positive predictive value (PPV) of 30%-49.4%, indicating a 30%-50% probability of difficult intubation. The negative predictive value (NPV) ranged from 95%-97%, meaning the likelihood of easy intubation with the above ultrasound parameter would be 95%-97%. In clinical practice, a positive result prompts caution in the intubation method12.
Hyomental distance (HMD) and hyomental distance ratio (HMDR) 
The HMD is determined by obtaining a submandibular image, which involves placing the transducer in the sagittal plane - longitudinally - in the submental space along the long central axis of the body. The image of the floor of the mouth shows a fine tissue echogenicity between the acoustic shadows of the mentum and the hyoid bone. The hard palate projects a hyperechoic white line. The HMD is measured from the upper border of the hyoid bone to the lower edge of the mentum of the mandible. The HMDR is the ratio of the hyomental distances in the neutral head position and the extended head position. The HMDR reflects the ability to estimate the submandibular space, which is essential during laryngoscopy. The hyoid bone moves with the extension of the neck, increasing the submandibular area. The inability to visualize the hyoid bone on ultrasound increases the likelihood of a difficult direct laryngoscopy. The below parameters are associated with a difficult direct laryngoscopy and are predictive in both the obese and general populations13,14:
1. HMD in the neutral position in the range of 3.43-4.55 cm (sensitivity: 100%, specificity: 71.4%)
2. HMD in the extended head position less than 5.50 cm (sensitivity: 100%, specificity: 71.4%)
3.HMDR less than 1.20 cm (sensitivity: 75%, specificity: 76.2%)
Distance from the skin to the vocal cords (SVC) 
Placing the ultrasound transducer on the thyroid cartilage in the transverse position allows the vocal cords to be visualized within a large upside-down V-shaped structure. The vocal cords display fine tissue echogenicity. With age, the thyroid cartilage calcifies at the level of the vocal cords. The vocal cords move with respiration. They are hypoechoic and triangular in shape, overlie the vocal cord muscles, and are medially attached to the hyperechoic ligaments; with phonation, the vocal cords close at the midline. The false vocal cords are hyperechoic because they contain fat, are parallel and cephalad, and do not move during phonation. Fine movements of the transducer cephalad and caudad distinguish the true vocal cords from the false vocal cords. The false vocal cords are hyperechoic, more prominent, and circular to oval. The true vocal cords are often only distinguished by the hyperechoic vocal cord ligaments.
A study by Ezri reported an overall 0.27 cm higher SVC value in difficult direct laryngoscopy and SVC measurements from 1.10-2.80 cm. The sensitivity and specificity were 53% and 66%, respectively10. A second study noted a distance between 0.92-1.30 cm with greater than 0.38 cm difference and a sensitivity and specificity of 75% and 80.6%, respectively, correlating with a difficult laryngoscopy11,15.
Distance from the skin to the hyoid bone (SHB) 
The placement of the probe transversally over the hyoid bone optimizes the view. The hyoid bone is a bright echogenic line that is curved upside. Below it, there is a hypoechoic shadow.
A distance of greater than 1.28 cm from the skin to the hyoid bone correlates with difficult direct laryngoscopy. The sensitivity is 85.7%, and the specificity 85.1%. In addition, a difference of 0.2 cm differentiates an easy airway from a difficult airway. In contrast, the Mallampatti airway classification is inconsistent, less sensitive, and less specific12. The ability to visualize the hyoid bone is associated with a lower Cormack-Lehane laryngoscopy grade and easy intubation13.
Thyrohyoid membrane (THM) 
The thyrohyoid membrane expands from the caudal border of the hyoid bone to the cephalad border of the thyroid cartilage. The view is optimized with the transducer in the transverse position between these two structures. The epiglottis is a hypoechoic (dark) curvilinear structure at this level. The thyrohyoid membrane distance is measured from the skin to the anterior border of the epiglottic space.
Adhikari et al. and Pinto et al. found that the anterior neck soft tissue thickness at the thyrohyoid membrane level is an independent predictor of difficult laryngoscopy8,16. Compared to an easy direct laryngoscopy, a 0.24 cm lower THM value was statistically significant for a difficult direct laryngoscopy. A value of more than 2.8 cm was predictive of a difficult laryngoscopy. Adhikari et al. did not report the sensitivity or specificity8. In the study from Pinto et al.16, the sensitivity was 64.7%, and the specificity was 77.1%. These two studies did not find an association between ultrasound measurements and clinical evaluation. Still, they concluded that the ultrasound measurement at the level of the THM was a better predictor than the SVC measurements.
Two other parameters are often mentioned in the ultrasound evaluation of the airway: the distance from the skin to the anterior surface of the first tracheal cartilage and the thickness of the tongue. However, these parameters were identified by small studies with inconsistent results, and a larger sample size is needed to supply substantial evidence17.
Table 1: Ultrasound parameters associated with difficult direct laryngoscopy. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/Table1.xlsx" target="_blank">Please click here to download this Table.</a>
Table 2: Ultrasound parameters in a difficult airway. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648_Table2.xlsx" target="_blank">Please click here to download this Table.</a>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64648/64648fig01.jpg" /> 
Figure 1: Hyomental distance (HMD). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64648/64648fig02.jpg" /> 
Figure 2: Thyrohyoid membrane (THM). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64648/64648fig03.jpg" /> 
Figure 3: Distance from the skin to the epiglottis (DSE). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/64648/64648fig04.jpg" /> 
Figure 4: Distance from the skin to the hyoid bone (SHB). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64648/64648fig05.jpg" /> 
Figure 5: Distance from the skin to the vocal cords (SVC). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64648/64648fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways

A point-of-care ultrasound (POCUS) is a simple, non-invasive, and portable tool that enables dynamic airway assessment. Several studies have attempted to determine the role of ultrasound parameters as an adjunct to clinical examination in predicting difficult laryngoscopies.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON ...

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1.3K Views.  Weill Cornell Medical Center (WCMC). A point-of-care ultrasound (POCUS) is a simple, non-invasive, and portable tool that enables dynamic airway assessment. Several studies have attempted to determine the role of ultrasound parameters as an adjunct to clinical examination in predicting difficult laryngoscopies.

Video: Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways

Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood

There is the need for a clinical assay to determine the extent to which a patient's blood is effectively anticoagulated by the low-molecular-weight-heparin (LMWH), enoxaparin. There are also urgent clinical situations where it would be important if this could be determined rapidly. The present assay is designed to accomplish this. We only assayed human blood samples that were spiked with known concentrations of enoxaparin. The essential feature of the present assay is the quantification of the efficacy of enoxaparin in a patient's blood sample by degrading it to complete inactivity with heparinase. Two blood samples were drawn into Vacutainer tubes (Becton-Dickenson; Franklin Lakes, NJ) that were spiked with enoxaparin; one sample was digested with heparinase for 5 min at 37 &deg;C, the other sample represented the patient's baseline anticoagulated status. The percent shortening of clotting time in the heparinase-treated sample, as compared to the baseline state, yielded the anticoagulant contribution of enoxaparin. We used the portable, battery operated Hemochron 801 apparatus for measurements of clotting times (International Technidyne Corp., Edison, NJ). The apparatus has 2 thermostatically controlled (37 &deg;C) assay tube wells. We conducted the assays in two types of assay cartridges that are available from the manufacturer of the instrument. One cartridge was modified to increase its sensitivity. We removed the kaolin from the FTK-ACT cartridge by extensive rinsing with distilled water, leaving only the glass surface of the tube, and perhaps the detection magnet, as activators. We called this our minimally activated assay (MAA). The use of a minimally activated assay has been studied by us and others. 2-4 The second cartridge that was studied was an activated partial thromboplastin time (aPTT) assay (A104). This was used as supplied from the manufacturer. The thermostated wells of the instrument were used for both the heparinase digestion and coagulation assays. The assay can be completed within 10 min. The MAA assay showed robust changes in clotting time after heparinase digestion of enoxaparin over a typical clinical concentration range. At 0.2 anti-Xa I.U. of enoxaparin per ml of blood sample, heparinase digestion caused an average decrease of 9.8% (20.4 sec) in clotting time; at 1.0 I.U. per ml of enoxaparin there was a 41.4% decrease (148.8 sec). This report only presents the experimental application of the assay; its value in a clinical setting must still be established.

Demonstration of a rapid quantitative assay of the inhibition of blood coagulation by the low-molecular-weight-heparin, enoxaparin. The contribution of enoxaparin is assessed by removing its influence through digestion with heparinase. A fuller description of the assay is detailed in our published paper.1 The assay still requires clinical confirmation.

There is the need for a clinical assay to determine the extent to which a patient's blood is effectively anticoagulated by the ...

Protocol and Guidelines for Point-of-Care Lung Ultrasound in Diagnosing Neonatal Pulmonary Diseases Based on International Expert Consensus

Ultrasound is a safe bedside imaging tool that obviates the use of ionizing radiation diagnostic procedures. Due to its convenience, the lung ultrasound has received increasing attention from neonatal physicians. Nevertheless, clear reference standards and guideline limits are needed for accurate application of this diagnostic modality. This document aims to summarize expert opinions and to provide precise guidance to help facilitate the use of the lung ultrasound in the diagnosis of neonatal lung diseases.

Lung ultrasound is a noninvasive and valuable tool for bedside evaluation of neonatal lung diseases. However, a relative lack of reference standards, protocols and guidelines may limit its application. Here, we aim to develop a standardized neonatal lung ultrasound diagnostic protocol to be used in clinical decision-making.

Ultrasound is a safe bedside imaging tool that obviates the use of ionizing radiation diagnostic procedures. Due to its convenience, the lung ultrasound ...

Evaluation of a Point-of-Care Testing Analyzer for Measuring Peripheral Blood Leukocytes

White blood cell (WBC) is an important indicator of inflammation in the body, and it can help distinguish between bacterial and viral infections. At present, most primary medical institutions in China have a poor percentage of adoption of blood-testing technology, and a hematology detection system with a high price to performance ratio and easy operation is urgently needed in primary healthcare centers. This paper introduces the principle and operation procedures of a point-of-care testing (POCT) card-based leukocyte analyzer (evaluated system), which was used to detect WBC indexes such as neutrophils, lymphocytes, and intermediate group cells (including eosinophils, basophils, and monocytes) in whole blood. The results from the evaluated system were compared to those from two commercial automatic hematology analyzers (reference system). The correlation and consistency between the evaluated system and the commercial reference systems were analyzed. The results showed that WBC count and number of granulocytes detected by the evaluated and reference systems showed a strong positive correlation (rs = 0.972 and 0.973, respectively), while the number of lymphocytes showed a relatively low correlation (rs = 0.851). A Bland-Altman plot showed that the major difference between the values detected by the evaluated system and the reference systems is within 95% limits of agreement (LoA), indicating that the two systems are in good agreement. In conclusion, the evaluated system has an excellent correlation, robust consistency, and a reliable comparison with the results of the widely used automatic hematology analyzers. It is ideal for WBC detection in primary medical institutions where a full-automatic five-category hematology analyzer is unavailable, especially during the COVID-19 normalized prevention and control period.

A protocol to measure peripheral blood leukocytes using a POCT card-based leukocyte analyzer is presented here. Same blood samples were tested by two automated hematology analyzers to evaluate the consistency and accuracy of the results. The results showed that the evaluated analyzer had a good correlation with the reference system.

White blood cell (WBC) is an important indicator of inflammation in the body, and it can help distinguish between bacterial and viral infections. At ...

Point-Of-Care Ultrasound Screening for Proximal Lower Extremity Deep Venous Thrombosis

Acute lower extremity deep venous thrombosis (DVT) is a serious vascular disorder that requires accurate and early diagnosis to prevent life-threatening sequelae. While whole leg compression ultrasound with color and spectral Doppler is commonly performed in radiology and vascular labs, point-of-care ultrasound (POCUS) is becoming more common in the acute care setting. Providers appropriately trained in focused POCUS can perform a rapid bedside examination with high sensitivity and specificity in critically ill patients. This paper describes a simplified yet validated approach to POCUS by describing a three-zone protocol for lower extremity DVT POCUS image acquisition. The protocol explains the steps in obtaining vascular images at six compression points in the lower extremity. Beginning at the level of the proximal thigh and moving distally to the popliteal space, the protocol guides the user through each of the compression points in a stepwise manner: from the common femoral vein to the femoral and deep femoral vein bifurcation, and, finally, to the popliteal vein. Further, a visual aid is provided that may assist providers during real-time image acquisition. The goal in presenting this protocol is to help make proximal lower extremity DVT exams more accessible and efficient for POCUS users at the patient&#39;s bedside.

Traditionally, lower extremity deep venous thrombosis (DVT) is diagnosed by radiology-performed venous duplex ultrasound. Providers appropriately trained in focused point-of-care ultrasound (POCUS) can perform a rapid bedside examination with high sensitivity and specificity in critically ill patients. We describe the scanning technique for focused POCUS DVT lower extremity examination.

Acute lower extremity deep venous thrombosis (DVT) is a serious vascular disorder that requires accurate and early diagnosis to prevent life-threatening ...

Point-of-Care Lung Ultrasound in Adults: Image Acquisition

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally prevents direct visualization of the lung parenchyma. When showing the lung parenchyma, ultrasound typically generates a number of non-anatomic artifacts. However, over the past several decades, these artifacts have been studied by diagnostic point-of-care ultrasound (POCUS) practitioners, who have identified findings that have value in narrowing the differential diagnoses of cardiopulmonary dysfunction. For instance, in patients presenting with dyspnea, lung POCUS is superior to chest radiography (CXR) for the diagnosis of pneumothorax, pulmonary edema, lung consolidations, and pleural effusions. Despite its known diagnostic value, the utilization of lung POCUS in clinical medicine remains variable, in part because training in this modality across hospitals remains inconsistent. To address this educational gap, this narrative review describes lung POCUS image acquisition in adults, including patient positioning, transducer selection, probe placement, acquisition sequence, and image optimization.

Point-of-care ultrasound (POCUS) of the lungs provides quick answers in rapidly changing clinical scenarios. We present an efficient and informative protocol for image acquisition for use in acute care settings.

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally ...

Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter (ONSD). Diagnostic ultrasound of the ONSD to detect intracranial hypertension has traditionally faced many problems because of methodologic discrepancies. Due to inconsistencies in the measuring techniques, the potential for ONSD to become a non-invasive bedside monitoring tool for ICP has been hampered. However, establishing a transparent, consistent methodology for measuring the ONSD would support its use as a valid and reliable method of identifying intracranial hypertension. This is important as it has both high sensitivity and specificity in acute care settings. This narrative review describes ONSD POCUS image acquisition, including patient positioning, transducer selection, probe placement, the acquisition sequence, and image optimization. Further, visual aids are provided to assist in real-time during image acquisition. This method should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place.

Point-of-care ultrasound (POCUS) of the optic nerve sheath diameter (ONSD) has been shown to be useful in identifying patients with increased intracranial pressure (ICP). However, the non-standardized technique for this POCUS has hampered its use. We present a standardized image acquisition protocol for use in the acute care setting.

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter ...

Imaging the Abdominal Aorta with Point-of-Care Ultrasound

An Approach to Point-Of-Care Ultrasound Evaluation of the Abdominal Aorta

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography (CT) is the current gold standard to image the abdominal aorta, the process of obtaining a CT may be time-consuming, requires the use of intravenous contrast dye, and involves exposure to ionizing radiation. Point-of-care Ultrasound (POCUS) can be performed at the bedside and has excellent sensitivity and specificity for the diagnosis of abdominal aortic aneurysm and excellent specificity for the diagnosis of abdominal aortic dissection. Additionally, POCUS is non-invasive, cost-effective, lacks ionizing radiation, requires no intravenous contrast dye, and can be performed without taking the patient from a critical care area. Screening for abdominal aortic aneurysm (AAA) can be done in primary care settings as well. 
This article will review the approach to POCUS of the abdominal aorta to evaluate such critical pathology. In this paper, we will review the sonographic anatomy of the abdominal aorta as well as the choice of the ultrasound probe, description of POCUS image acquisition, and some pearls and pitfalls of using POCUS to aid in the diagnosis of potentially life-threatening abdominal aortic pathology.

Author Spotlight: Using Point-of-Care Ultrasound for Comprehensive Evaluation of the Abdominal Aorta

This protocol reviews the steps to image the abdominal aorta with point-of-care ultrasound. We discuss image acquisition, troubleshooting imaging pitfalls and artifacts, and the recognition of life-threatening abdominal aortic pathology.

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography ...

Gastric Ultrasound Technique for Mitigating Peri-Procedural Aspiration Risk

Gastric Point of Care Ultrasound in Adults: Image Acquisition and Interpretation

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical inquiries related to gastric content. One emerging concern pertains to patients about to undergo sedation and/or endotracheal intubation: the elevated risk of aspiration from the patient&#39;s stomach contents. Aspiration of gastric contents into the lungs poses a serious and potentially life-threatening complication. This occurs more frequently when the stomach is considered &#34;full&#34; and can be affected by the techniques employed for airway management, making it potentially preventable. To mitigate the risk of peri-procedural aspiration, two distinct medical specialties (anesthesiology and critical care medicine) have independently developed techniques to utilize ultrasonography for identifying patients requiring &#34;full stomach&#34; precautions. Due to these separate specialties, the work of each group remains relatively unfamiliar outside its respective field. This article presents descriptions of both techniques for gastric ultrasound. Furthermore, it explains how these approaches can complement each other when one of them falls short. Regarding image acquisition, the article covers the following topics: indications and contraindications, selection of the appropriate probe, patient positioning, and troubleshooting. The article also delves into image interpretation, complete with example images. Additionally, it demonstrates how one of the two techniques can be employed to estimate gastric fluid volume. Lastly, the article briefly discusses medical decision-making based on the findings of this examination.

Author Spotlight: Point-of-Care Ultrasound for Gastric Content Assessment and Risk Stratification in Perioperative Care 

This protocol introduces two methods for image acquisition in gastric ultrasonography. Additionally, tips are provided for interpreting this information to assist in medical decision-making.

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical ...

Ultrasound in Evaluating Diaphragm Dysfunction and Monitoring Treatment

Measuring Diaphragm Thickness and Function Using Point-of-Care Ultrasound

The diaphragm is the main component of the respiratory muscle pump. Diaphragm dysfunction can cause dyspnea and exercise intolerance, and predisposes affected individuals to respiratory failure. In mechanically ventilated patients, the diaphragm is susceptible to atrophy and dysfunction through disuse and other mechanisms. This contributes to failure to wean and poor long-term clinical outcomes. Point-of-care ultrasound provides a valid and reproducible method for evaluating diaphragm thickness and contractile activity (thickening fraction during inspiration) that can be readily employed by clinicians and researchers alike. This article presents best practices for measuring diaphragm thickness and quantifying diaphragm thickening during tidal breathing or maximal inspiration. Once mastered, this technique can be used to diagnose and prognosticate diaphragm dysfunction, and guide and monitor response to treatment over time in both healthy individuals and acute or chronically ill patients.

Author Spotlight: Unraveling the Impact of Mechanical Ventilation on Diaphragm Function and Patient Outcomes 

Diaphragm thickness and function can be assessed in healthy individuals and critically ill patients using point-of-care ultrasound. This technique offers an accurate, reproducible, feasible, and well-tolerated method for evaluating diaphragm structure and function.

The diaphragm is the main component of the respiratory muscle pump. Diaphragm dysfunction can cause dyspnea and exercise intolerance, and predisposes ...

Novel PLL-AF Suture Technique for Annulus Fibrosus Repair in Lumbar Endoscopy

A Suture Technique for Ruptured Annulus Fibrosus Following Decompression Under Percutaneous Transforaminal Endoscopic Discectomy

The suture technique for a ruptured annulus fibrosus (AF) under full-endoscopy remains challenging. Direct suturing of a ruptured annular tear after full decompression has been shown to decrease the recurrence rate of lumbar disc herniation during endoscopic surgery. Traditional suture operations under endoscopy involve only simple suturing of the ruptured AF. Due to the weak and poor quality of the AF tissue around the tear portal, using this area as needle insertion points during suturing may lead to insufficient tension and a low success rate of AF closure. Currently, there is no detailed technical illustration based on video for AF tear suturing under lumbar full-endoscopy. We innovatively propose a method of covering and suturing the AF tear by pulling up the posterior longitudinal ligament (PLL) under lumbar endoscopy and using three stitches (PLL-AF suture technique). The patient who received the novel suture technique achieved satisfactory results. Six months after the operation, lumbar MRI showed no evidence of recurrence in the outpatient clinic.

Author Spotlight: Development and Application of a Novel Suture Technique for Annular Fibrosus Repair in Percutaneous Transforaminal Endoscopic Discectomy

This protocol describes an innovative suture technique for ruptured annular fibrosus during percutaneous transforaminal endoscopic discectomy.

The suture technique for a ruptured annulus fibrosus (AF) under full-endoscopy remains challenging. Direct suturing of a ruptured annular tear after full ...