The authors have no acknowledgments. Alexandra Pop and Ioan Florin Marchis are featured in the video production that complements this article.

We designed a prospective, observational, single-center study evaluating the feasibility of tracheal intubation using the RTL with the approval of the University Ethics Committee no 432/24.11.2016 and registered with ClinicalTrials.gov NCT03341507. The study involved adult patients with ASA physical status 1&#8211;3, requiring general anesthesia for ear, parotid, and rhino-sinus surgery and having a presumed anatomically difficult airway as calculated with The Simplified Airway Risk Index (SARI) score8, with a score &#8805; 5, and no airway pathology.
NOTE: The pre-anesthetic exam focused on airway evaluation aiming to select patients with a modified Cormack-Lehane7 grade of glottic visualization &#8805;2b. The Cormack-Lehane classification defines the grade of glottis view during laryngoscopy, ranging from unrestricted glottic visualization-grade 1 to inability to see any laryngeal structure-grade 4. The SARI score8 is a multivariate risk score for predicting difficult tracheal intubation. A SARI score of 4 or above, 12 being maximum, enhances the chances of difficult intubation. Seven parameters contribute to the SARI score: mouth opening, thyromental distance, movement of the neck, Mallampati score, the ability to create an underbite, body weight, and previous intubation history.
1. Patient and equipment preparation
<ol>
	<li>Premedicate with 1 or 2 mg of midazolam intravenously for 10 min upon patient transportation in the operating theatre.</li>
	<li>Have the patient lie on the operating table with their head placed at a tilt in a sniffing position.</li>
	<li>Apply standard hemodynamic and respiratory monitoring: ECG, noninvasive arterial blood pressure, oxygen saturation, respiratory frequency, end-tidal CO2. Monitor patient anesthesia depth using bispectral index monitoring.</li>
	<li>Make sure that an experienced anesthetist or ENT physician is available in case of an emergency.</li>
	<li>Prepare a suction device with a suction probe in place and a difficult airway kit at hand. Prepare and check the connective piece with the light source attached with a set of rigid tubes of various sizes: three tubes that are 15-20 cm long with a 1.2-1.8 cm diameter for women and three tubes that are 20-25 cm long with a 1.2-2 cm diameter for men.</li>
	<li>Identify the thyroid cartilage (Adam&#39;s apple) by palpation of the anterior neck. Ask the patient to swallow and gently palpate the anterior neck with the thumb, the index, and the middle finger. The thyroid cartilage is the structure that moves while the patient swallows.
	<ol>
		<li>Ask the patient to extend the head and measure the distance between the labial commissure and the thyroid cartilage in a straight line using the thumb and the middle finger. Hold a rigid tube in the other hand while performing the measurement. The mandible impedes the use of a ruler to measure this distance.</li>
		<li>Note the length obtained on the rigid tube prepared, starting from its tip. Do this by directly translating the two fingers used to measure the distance mentioned in the previous step on the rigid tube.</li>
		<li>Expect to find the glottis when using the RTL at a depth equal with the distance between the labial commissure and thyroid cartilage. For a better grip and a useful lever effect, use a tube with a length of about double the above-measured distance.</li>
	</ol>
	</li>
</ol>
2. Induction of general anesthesia and conventional laryngoscopy
<ol>
	<li>Preoxygenate the patients for 5 min and start anesthesia induction with 2-3 &#181;g/kg fentanyl, 2-3 mg/kg propofol, and 1-1.5 mg/kg succinylcholine. Monitor the depth of anesthesia by checking the bispectral index level.</li>
	<li>After 1 min of mask ventilation with a pause during generalized muscular fasciculation provoked by succinylcholine, perform standard laryngoscopy with a curved blade laryngoscope, and register the modified Cormack-Lehane glottis visualization grade.
	<ol>
		<li>If the noticed degree is &#60;2b, resume the tracheal intubation conventionally with the curved blade laryngoscope.</li>
		<li>If the glottis view grade is &#8805;2b, meaning that, at the best, part of the arytenoids and the epiglottis are visible, withdraw the Macintosh laryngoscope, and maneuver further with the RTL. 
		CAUTION: If the mask ventilation is impossible or not efficient, the airway should be secured promptly following the institutional guidelines.</li>
	</ol>
	</li>
</ol>
3. Tracheal intubation with the rigid tube
<ol>
	<li>Cover the upper molars with a rubber teeth protector or a cotton swab on the side of the approach.</li>
	<li>Introduce the RTL in the oral cavity at the level of the right or left labial commissure with the bevel facing the superior arcade, the prismatic light deflector, and a functioning light source attached, held with the dominant hand with the light deflector inside the palm and the index following the tube.
	<ol>
		<li>Start with a 1.5-1.8 cm diameter tube to maximize the visual field.</li>
		<li>Displace the tongue gently to the contralateral site.</li>
		<li>If the pathology does not require otherwise, a righthanded practitioner should use the right retromolar space for approach.</li>
	</ol>
	</li>
	<li>Use the nondominant hand to open the patient&#8217;s mouth, hyperextend the patient&#39;s head, and advance the RTL towards the pharynx.</li>
	<li>Apply gentle pressure on the proximal end of the RTL against the protected superior molars as the tip of the tube is reaching the hypopharynx. That way, the tip of the RTL orientates anteriorly on the direction of the glottis. 
	NOTE: The thyroid cartilage is a landmark when moving the tip of the RTL from the retromolar space towards the midline.
	<ol>
		<li>If the epiglottis, the glottis or part of it is not getting into sight, withdraw the tube. At the second attempt, insert the tube in the oral cavity at the level of the incisors as that may make the tongue base and epiglottis easier to access. Once the epiglottis is in sight, slide the tube towards the labial commissure, keeping its tip in place, and advance further.</li>
		<li>Aspirate the secretions as needed with a flexible suction probe inserted through the RTL.</li>
		<li>Adjust the position of the larynx with the nondominant hand by gently pushing the thyroid cartilage and follow an imaginary line towards the thyroid cartilage as it improves the time needed for proper glottis visualization. 
		NOTE: When moving the cartilage while looking through the tube, the motion translates to the inner structures around the glottis and helps the practitioner orientate to reach his target.</li>
	</ol>
	</li>
	<li>Advance the RTL slowly until it reaches the epiglottis, and then lift the epiglottis with the tip of the device. Make sure that the bevel is oriented posteriorly. At that point, the vocal cords are visible at the distal end of the tube.
	<ol>
		<li>If, after lifting the epiglottis, the glottis is not in the visual field, consider using a smaller diameter RTL.</li>
	</ol>
	</li>
	<li>Once the glottis is in sight, place the intubating tube introducer through the RTL into the trachea. Do not insert the introducer too vigorously because the bronchial injury may occur.
	<ol>
		<li>Do not advance any more as soon as the glottis is visible after lifting the epiglottis because of the risk of vocal cord injury.</li>
	</ol>
	</li>
	<li>Extract the rigid tube.</li>
	<li>Place a standard cuffed lubricated intubating tube over the introducer into the trachea. Do not use force and gently rotate the intubating tube while advancing.
	<ol>
		<li>Make sure there is only a small gap between the inner diameter of the intubating tube and the introducer to reduce the chance of impingement.</li>
	</ol>
	</li>
	<li>Once the intubating tube is at the proper depth, 20-24 cm from the labial commissure, remove the intubating tube introducer leaving the intubating tube in place.</li>
	<li>Inflate the cuff and confirm tracheal intubation through lung auscultation and capnography.</li>
	<li>Inspect the upper lip and the teeth for damage. Be aware that the intubation over an intubating tube introducer carries the risk of vocal cords injury. Check the patient for sore throat and voice disturbance after surgery. 
	CAUTION: Stop the maneuver if it exceeds 100 s or if the patient desaturates to 80% and resume mask ventilation or an alternative method of securing the airway.</li>
</ol>

<ol>
	<li>Cook, T. M., Woodall, N., Frerk, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Major+complications+of+airway+management+in+the+UK:+results+of+the+4th+National+Audit+Project+of+the+Royal+College+of+Anaesthetists+and+the+Difficult+Airway+Society.+Part+1+Anaesthesia.">Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1 Anaesthesia.</a> British Journal of Anaesthesia. 106 (5), 617-631 (2011).</li><li>Halligan, M., Charters, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Learning+curve+for+the+Bonfils+intubation+fibrescope.">Learning curve for the Bonfils intubation fibrescope.</a> British Journal of Anaesthesia. 89, 671-672 (2002).</li><li>Smith, J. E., Jackson, A. P., Hurdley, J., Clifton, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Learning+curves+for+fibreoptic+nasotracheal+intubation+when+using+the+endoscopic+video+camera.">Learning curves for fibreoptic nasotracheal intubation when using the endoscopic video camera.</a> Anaesthesia. 52 (2), 101-106 (1997).</li><li>N&#248;rskov, A. K., 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=Diagnostic+accuracy+of+anaesthesiologists'+prediction+of+difficult+airway+management+in+daily+clinical+practice:+a+cohort+study+of+188+064+patients+registered+in+the+Danish+anaesthesia+database.">Diagnostic accuracy of anaesthesiologists' prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish anaesthesia database.</a> Anaesthesia. 70 (3), 272-281 (2015).</li><li>Fagan, J., De Groot, M., za, . <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rigid+Laryngoscopy,+Oesophagoscopy+&amp;+Bronchoscopy+in+Adults.">Rigid Laryngoscopy, Oesophagoscopy &amp; Bronchoscopy in Adults.</a> Open Access Atlas of Otolaryngology, Head &amp; Neck Operative Surgery. , (2019).</li><li>Marchis, F., Radeanu, D., Pop, S., Chirila, M., Cosgarea, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Rigid+Tube+of+Laryngoscopy+-+a+New+Intubation+Technique.">The Rigid Tube of Laryngoscopy - a New Intubation Technique.</a> Proceedings: National ENT, Head and Neck Surgery Conference. , 143-146 (2017).</li><li>Krage, R., 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=Cormack-Lehane+classification+revisited.">Cormack-Lehane classification revisited.</a> British Journal of Anaesthesia. 105 (2), 220-227 (2010).</li><li>N&#248;rskov, A. K., Rosenstock, C. V., Wetterslev, J., Lundstr&#248;m, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incidence+of+unanticipated+difficult+airway+using+an+objective+airway+score+versus+a+standard+clinical+airway+assessment:+the+DIFFICAIR+trial+-+trial+protocol+for+a+cluster+randomized+clinical+trial.">Incidence of unanticipated difficult airway using an objective airway score versus a standard clinical airway assessment: the DIFFICAIR trial - trial protocol for a cluster randomized clinical trial.</a> Trials. 14, 347 (2013).</li><li>Cook, T. M., MacDougall-Davis, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complications+and+failure+of+airway+management.">Complications and failure of airway management.</a> British Journal of Anaesthesia. 109 (1), 68-85 (2012).</li><li>Abdullah, H. R., Li-Ming, T., Marriott, A., Wong, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparison+between+the+Bonfils+Intubation+Fiberscope+and+McCoy+laryngoscope+for+tracheal+intubation+in+patients+with+a+simulated+difficult+airway.">A comparison between the Bonfils Intubation Fiberscope and McCoy laryngoscope for tracheal intubation in patients with a simulated difficult airway.</a> Anesthesia &amp; Analgesia. 117 (5), 1217-1220 (2013).</li><li>Henderson, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+paraglossal+straight+blade+laryngoscopy+in+difficult+tracheal+intubation.">The use of paraglossal straight blade laryngoscopy in difficult tracheal intubation.</a> Anaesthesia. 52 (6), 552-560 (1997).</li><li>Bein, B., 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+intubation+using+the+Bonfils+intubation+fibrescope+after+failed+direct+laryngoscopy.">Tracheal intubation using the Bonfils intubation fibrescope after failed direct laryngoscopy.</a> Anaesthesia. 59, 1207-1209 (2004).</li><li>Webb, 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+the+Bonfils+and+Levitan+optical+stylets+for+tracheal+intubation:+a+clinical+study.">Comparison of the Bonfils and Levitan optical stylets for tracheal intubation: a clinical study.</a> Anaesthesia and Intensive. 39 (6), 1093-1097 (2011).</li><li>Paul, A., Gibson, A. A., Robinson, O. D., Koch, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+traffic+light+bougie:+a+study+of+a+novel+safety+modification.">The traffic light bougie: a study of a novel safety modification.</a> Anaesthesia. 69 (3), 214-218 (2014).</li></ol>

The authors have nothing to disclose. We did not find a current commercial offer for the rigid tube and the connective piece we used in this study.

The most prevalent mistake when dealing with an unexpected problematic airway is to insist on the same tool and the same technique only to realize that it is not working. This makes the situation only worse by promoting edema or bleeding9.
We had the idea of testing this tool when we anesthetized a patient with a grade 4 glottic visualization at conventional laryngoscopy, according to the Cormack-Lehane classification. Since the rigid tube was prepared to investigate this patient, and we did not have another backup device at hand, we tried it using the retromolar approach and obtained a perfect glottis view.
Tracheal intubation with the RTL using the retromolar approach, resembling the Bonfil&#39;s Rigid Endoscope intubation technique10, offers an alternative when curved blade laryngoscopy is unsatisfactory. The improved view obtained with this technique may result from the reduced pressure applied on the tongue base and the consecutive decrease in the chance of backward displacement of the epiglottis11. In addition, because of the tubular shape of the RTL, the intrusion of the soft structures into the line of sight is eliminated. The reduced soft tissue compression, as compared with the Macintosh technique, comes from a better airway alignment during the retromolar approach in case of the more anterior position of the glottis. Using either side is an advantage for lefthanded and in the case of pharyngeal or cervical masses6. Patients with protruding upper teeth and a reduced inter-incisors gap may also benefit from this technique6.
In our research, the median intubation time with the rigid tube was 50 s. In a study carried by Bein et al., 25 patients with a poor glottis view at conventional laryngoscopy were intubated with the Bonfil&#39;s rigid endoscope in a median time of 47 s12. Another paper comparing two types of rigid stylets used in a retromolar manner reported 35-40 s to accomplish tracheal intubation13.
The thyroid cartilage being a landmark means that one should take care that the rigid tube orientates towards it during the RTL advancement. Accomplishing that requires a reasonable sense of spatial orientation as the investigator is alternatively looking through the device and following its progression in the direction of the thyroid cartilage. Once the tip of the RTL reaches the pharynx, the investigator adjusts the rigid tube direction, not looking through the tube but following with the tip of the device the location of the thyroid cartilage. When the tube and the thyroid cartilage are aligned, the operator is searching for the epiglottis and glottis looking through the instrument. From experience, following these steps will reduce the time needed for laryngoscopy. Inserting the tube in the oral cavity at the level of the incisors and sliding retromolar once the epiglottis is visible represents a viable alternative at the second attempt.
RTL is a compact instrument easy to decontaminate, resistant to long term use, and requires a minimal setup time; its cost of maintenance is lower than that of most of the tools used for airway control. The aspiration of saliva or blood proves facile by inserting a suction probe through the tube, and there is no risk of fogging since there is no distal optical system involved.
The main limitation of this method is the reduced visual field, proportional to the RTL diameter. Aiming the tip of the RTL towards the thyroid cartilage surpasses this deficiency in part. Dental injury and bleeding of the pharyngeal structures during the procedure are potential complications, especially if embedded with excessive force. The use of intubating tube introducers carries the risk of airway perforation if it is inserted too deep, vocal cord injury, and the impossibility of advancing the intubating tube in the trachea14. The technique needs a training period for reasonable expertise and regular use for proficiency preservation.
Although we did not find data in the literature regarding this method of airway approach, we are confident that this simple, cost-efficient technique, at hand in a hospital with an ENT department, might prove useful as a rescue option when a practitioner encounters difficult intubation.

Airway management incidents represent a large proportion of anesthesia-related mortality and severe morbidity despite the development of new tools for airway control and extensive educational resources1. The video laryngoscope and flexible or rigid endoscopes are big steps forward, but they require a supplementary investment in addition to training2,3. Difficult intubation is often unanticipated, so it is the practitioner&#39;s responsibility to have a backup plan and use the appropriate tool from those available4. This study aims to show that a cheap and straightforward tool, the rigid tube for laryngoscopy (RTL), could be efficiently used for tracheal intubation in patients with poor glottis visualization during conventional laryngoscopy.
The rigid tube for laryngoscopy (Figure 1) is a 15-25 cm long, straight, round hollow tube with a 5-20 mm diameter and a bevel end distally. It resembles a rigid bronchoscope or esophagoscope, but shorter5. A connective piece that has a prismatic light deflector with connection to a light source is attached to the proximal end of the rigid tube when in use, and the image is obtained directly, looking through this assembly. It is an instrument used by ear, nose, and throat specialists to visualize the larynx and its vicinity. In a pilot study, 20 patients with supraglottic pathology and anatomically challenging airways were intubated with the rigid tube, and the results were encouraging6.
This research included patients with anatomical criteria for difficult intubation and a modified Cormack-Lehane7 glottis view grade &#8805;2b when using a curved blade laryngoscope. The purpose was to demonstrate that laryngoscopy using the rigid tube with a retromolar approach could offer a quick glottic view in cases with poor glottic visualization at conventional laryngoscopy and the right conditions to intubate the trachea over the intubating tube introducer.

<table><tbody><tr><td>Airway management set</td><td>Karl Storz</td><td>11300 B3</td><td></td></tr><tr><td>Anesthesia machine</td><td>Draeger</td><td></td><td></td></tr><tr><td>Anesthetic drug: Fentanyl</td><td>Chiesi</td><td></td><td></td></tr><tr><td>Anesthetic drug: propofol</td><td>Fresenius</td><td></td><td></td></tr><tr><td>Anesthetic drug: succinylcholine</td><td>Takeda</td><td></td><td></td></tr><tr><td>Anesthetic drugs: midazolam</td><td>Aguettant</td><td></td><td></td></tr><tr><td>Intubation Tube</td><td>Touren</td><td></td><td>A 7-7.5 mm diameter is suitable for tracheal intubation over the bougie</td></tr><tr><td>Intubation Tube Introducer (Bougie)</td><td>Ontex</td><td></td><td></td></tr><tr><td>Lubricating gel</td><td>Dynarex</td><td></td><td></td></tr><tr><td>Mcintosh laryngoscope</td><td>Heine</td><td></td><td></td></tr><tr><td>Rigid tube with a removable connective piece that has a prismatic light deflector attached</td><td>Explorent GMBH</td><td></td><td>The connective piece serial number is: 650021&lt;br/&gt; We did not find a current commercial offer for the rigid tube and the connective piece we used in this study.</td></tr><tr><td>Table top light source with light cable</td><td>Karl Storz</td><td>20134001, 61594GW</td><td></td></tr></tbody></table>

the rigid tube as an alternative in controlling the problematic airway

The unexpected problematic airway represents a large proportion of anesthesia-related morbidity and mortality. The retromolar or paraglossal approach is an alternative to the majority of the rigid instruments used for tracheal intubation, which follow the midline to access the glottis. This single-center, prospective case-series study offers an option to conventional laryngoscopy in case of a poor glottic view, introducing an instrument (the rigid tube for laryngoscopy) that uses the retromolar approach to accomplish tracheal intubation. If after anesthesia induction, the modified Cormack-Lehane glottis view grade &#62;2b, the intubation is carried further with the rigid tube. The tube follows the direction of the thyroid cartilage while advancing from the labial commissure, displacing the tongue to the contralateral side. Adjusting the position of the larynx with the nondominant hand by gently pushing the thyroid cartilage and following an imaginary line towards it while advancing it improves the time needed for proper glottis visualization. Once the epiglottis is in sight, the practitioner progresses slowly, lifting the epiglottis and aiming the tip of the tube more anteriorly. When the glottis appears in the visual field, the intubating tube introducer is placed in the trachea, and a lubricated cuffed intubating tube is advanced over the introducer after the rigid tube is extracted. This tool was tested on 30 patients with an unsatisfactory glottic view when using the Macintosh laryngoscope and obtained excellent results with respect to intubation time and complications. The reduced visual field is the main limitation of this method, which requires a training period for reasonable expertise. This simple, robust, and cheap instrument could be a rescue option in case of a difficult airway.

Over 24 months, we included 64 patients with a SARI &#8805;5, predictive for difficult intubation (Supplemental File 1). Thirty of them presented a modified Cormack-Lehane glottis view grade &#8805;2b during the laryngoscopy performed with the curved blade laryngoscope, so they were attempted to be tracheal intubated with the RTL (Table 1). In all cases, with one exception, the procedure with the rigid tube was successful without any incidents occurring. The patient we did not intubate, with a grade 3 Cormack-Lehane glottis view, desaturated to 80% in less than a minute, so we decided to place a laryngeal mask since the patient would have ear surgery.
In most of the cases (two-thirds), the intervention was straightforward, and the glottis was in sight in less than 25 s from the start of the maneuver with the RTL with a median total time for intubation of 50 s (Figure 2). The advancement of the intubating tube over the intubating tube introducer lasted between 20 and 30 s and was uneventful also. We did not find a statistical correlation between the time needed for intubation and the Cormack-Lehane glottis view grade at conventional laryngoscopy.
The median oxygen saturation after tracheal intubation was 95%, and the lowest desaturation was 83%. We did not notice any significant complication during or after the procedure: five patients complained of sore throat, and three cases presented minor injury of the upper lip.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61102/61102fig01.jpg" /> 
Figure 1: The rigid tube for laryngoscopy with the connective piece. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61102/61102fig01large.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/61102/61102fig02.jpg" /> 
Figure 2: Intubation time with the rigid tube. 
The extreme values are indicated on the bottom respectively on the top of the chart, while the median value and the interquartile range values are filled with grey. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61102/61102fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Total,n</td>
			<td>30</td>
		</tr>
		<tr>
			<td>Age mean&#177;SD</td>
			<td>47.8 &#177;10.5</td>
		</tr>
		<tr>
			<td>Female sex, n</td>
			<td>4</td>
		</tr>
		<tr>
			<td>BMI mean&#177;SD</td>
			<td>33.2 &#177;4.5</td>
		</tr>
		<tr>
			<td>ASA (1/2/3),n</td>
			<td>5/14/11</td>
		</tr>
		<tr>
			<td>SARI score median</td>
			<td>6</td>
		</tr>
		<tr>
			<td>Baseline oxygen saturation (%) median (IQR)</td>
			<td>98(97-99)</td>
		</tr>
		<tr>
			<td>Cormack-Lehane (2b/3/4),n</td>
			<td>16/12/2.</td>
		</tr>
	</tbody>
</table>
Table 1: The essential pre-anesthetic features of the patients included in the study. ASA-American Society of Anesthesiologists; BMI- Body Mass Index; SARI- Simplified Airway Risk Index; IQR- Interquartile Range
Supplemental File 1: Experimental Flow Diagram. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61102/Flow_Diagram.docx" target="_blank">Please click here to download this file.</a>

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The Rigid Tube as an Alternative in Controlling the Problematic Airway

Presented here is a protocol of tracheal intubation over an intubating tube introducer using a rigid tube for laryngoscopy with an attached light source. The main characteristics of this maneuver are the retromolar approach and the use of the thyroid cartilage as a landmark while advancing the rigid tube.

The unexpected problematic airway represents a large proportion of anesthesia-related morbidity and mortality. The retromolar or paraglossal approach is ...

the-rigid-tube-as-an-alternative-in-controlling-the-problematic-airway

Nanyang Technological University

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JoVE Journal

Medicine

6.3K Views.  Iuliu Hatieganu University of Medicine and Pharmacy. Deze studie heeft tot doel aan te tonen dat een goedkoop en eenvoudig hulpmiddel, de stijve buis voor laryngoscopie, efficiënt kan worden gebruikt voor tracheale intubatie bij patiënten met slechte glottis-visualisatie tijdens conventionele laryngoscopie. Een heersende fout wanneer men zich bezighoudt met een onverwachte problematische luchtwegen is aan te dringen op dezelfde tool en dezelfde methode alleen om te beseffen dat het niet werkt. En de situatie wordt steeds erger door het bevord...

Video: The Rigid Tube as an Alternative in Controlling the Problematic Airway

A Novel Rescue Technique for Difficult Intubation and Difficult Ventilation

We describe a novel non surgical technique to maintain oxygenation and ventilation in a case of difficult intubation and difficult ventilation, which works especially well with poor mask fit.
Can not intubate, can not ventilate" (CICV) is a potentially life threatening situation. In this video we present a simulation of the technique we used in a case of CICV where oxygenation and ventilation were maintained by inserting an endotracheal tube (ETT) nasally down to the level of the naso-pharynx while sealing the mouth and nares for successful positive pressure ventilation.
A 13 year old patient was taken to the operating room for incision and drainage of a neck abcess and direct laryngobronchoscopy. After preoxygenation, anesthesia was induced intravenously. Mask ventilation was found to be extremely difficult because of the swelling of the soft tissue. The face mask could not fit properly on the face due to significant facial swelling as well. A direct laryngoscopy was attempted with no visualization of the larynx. Oxygen saturation was difficult to maintain, with saturations falling to 80%. In order to oxygenate and ventilate the patient, an endotracheal tube was then inserted nasally after nasal spray with nasal decongestant and lubricant. The tube was pushed gently and blindly into the hypopharynx. The mouth and nose of the patient were sealed by hand and positive pressure ventilation was possible with 100% O2 with good oxygen saturation during that period of time. Once the patient was stable and well sedated, a rigid bronchoscope was introduced by the otolaryngologist showing extensive subglottic and epiglottic edema, and a mass effect from the abscess, contributing to the airway compromise. The airway was secured with an ETT tube by the otolaryngologist.This video will show a simulation of the technique on a patient undergoing general anesthesia for dental restorations.

We describe a technique to maintain oxygenation and ventilation using an endotracheal tube inserted nasally to the level of the naso-pharynx while sealing the mouth and nares for successful positive pressure ventilation.

We describe a novel non surgical technique to maintain oxygenation and ventilation in a case of difficult intubation and difficult ventilation, which ...

An Improved Method for Rapid Intubation of the Trachea in Mice

Despite some anatomical and physiological differences, mouse models continue to be an essential tool for studying human lung disease. Bleomycin toxicity is a commonly used model to study both acute lung injury and fibrosis, and multiple methods have been developed for administering bleomycin (and other toxic agents) into the lungs. However, many of these approaches, such as transtracheal instillation, have inherent drawbacks, including the need for strong anesthetics and survival surgery. This paper reports a quick, reproducible method of intratracheal intubation that involves mild inhaled anesthesia, visualization of the trachea, and the use of a surrogate spirometer to confirm exposure. As a proof of concept, 8-12 week old C57BL/6 mice were administered either 2.0 U/kg of bleomycin or an equivalent volume of PBS, and both damage and fibrotic endpoints were measured post-exposure. This procedure allows researchers to treat a large cohort of mice in a relatively short period with little expense and minimal post-procedure care.

This article presents a rapid and simple method for administering bleomycin directly into the mouse trachea via intubation. Key advantages of this method are that it is highly reproducible, easy to master, and does not require specialized equipment or lengthy recovery times.

Despite some anatomical and physiological differences, mouse models continue to be an essential tool for studying human lung disease. Bleomycin toxicity ...

Manufacture of a Multi-Purpose Low-Cost Animal Bench-Model for Teaching Tracheostomy

Tracheostomy is one of the most frequent procedures, performed through various techniques in the intensive care unit and emergency situations. Despite this, there is a lack of training on this procedure that affects its outcome, which is also dependent on operator's dexterity. Here, we take the specific training and simulation into consideration. This article aims to describe every step of the manufacture of a new multi-purpose low-cost animal bench-model, with the support of video and images, and to obtain an opinion about the quality of this model by administering a questionnaire to professionals with experience in the procedures. 
Ten experts in the technique were enrolled. The model scored an average of 3.45/5 for its anatomical realism; 4.75/5 for its usefulness as a training tool for simulation courses and assessments. The time necessary to build the model was 15 minutes, and the cost amounted to 10&#8364;. The animal bench-model was considered a very useful simulator for tracheostomy training and assessments. Therefore, it could be used as a tool for medical courses and residencies.

This article illustrates every step of the manufacture of a new multi-purpose low-cost animal bench-model for subglottic airway access management. All the procedures are shown in the video. The model's realism and its suitability for training the given clinical maneuvers were assessed by independent senior otolaryngologists and anesthesiologists.

Tracheostomy is one of the most frequent procedures, performed through various techniques in the intensive care unit and emergency situations. Despite ...

Endotracheal Intubation Using a Flexible Intubation Endoscope as a Standardized Model for Safe Airway Management in Swine

Endotracheal intubation is often a basic requirement for translational research in porcine models for various interventions that require a secured airway or high ventilation pressures. Endotracheal intubation is a challenging skill,&#160;requiring a minimum number of successful endotracheal intubations to achieve a high success rate under optimal conditions, which is often unachievable for non-anaesthesiology researchers. Due to the specific porcine airway anatomy, a difficult airway can usually be assumed. The impossibility of establishing a secure airway can result in injury, adverse events, or death of the laboratory animal. Using a prospective, randomized, controlled evaluation approach, it has been shown that fiberoptic-assisted endotracheal intubation takes longer but has a higher first-pass success rate than conventional intubation without causing clinically relevant drops in oxygen saturation. This model presents a standardized regimen for endoscopically guided endotracheal intubation, providing a secured airway, especially for researchers who are inexperienced in the technique of endotracheal intubation via direct laryngoscopy. This procedure is expected to minimize animal suffering and unnecessary animal losses.

The use of pigs in research has increased in recent years. Nevertheless, pigs are characterized by difficult airway anatomy. By demonstrating how to perform endoscopically guided endotracheal intubation, the present protocol aims to further increase laboratory animals' safety to avoid animal suffering and unnecessary death.

Endotracheal intubation is often a basic requirement for translational research in porcine models for various interventions that require a secured airway ...

Image Acquisition using Portable Sonography for Emergency Airway Management

With its increasing popularity and accessibility, portable ultrasonography has been rapidly adapted not only to improve the perioperative care of patients, but also to address the potential benefits of employing ultrasound in airway management. The benefits of point of care ultrasound (POCUS) include its portability, the speed at which it can be utilized, and its lack of invasiveness or exposure of the patient to radiation of other imaging modalities.
Two primary indications for airway POCUS include confirmation of endotracheal intubation and identification of the cricothyroid membrane in the event a surgical airway is required. In this article, the technique of using ultrasound to confirm endotracheal intubation and the relevant anatomy is described, along with the associated ultrasonographic images. In addition, identification of the anatomy of the cricothyroid membrane and the ultrasonographic acquisition of appropriate images to perform this procedure are reviewed.
Future advances include utilizing airway POCUS to identify patient characteristics that might indicate difficult airway management. Traditional bedside clinical exams have, at best, fair predictive values. The addition of ultrasonographic airway assessment has the potential to improve this predictive accuracy. This article describes the use of POCUS for airway management, and initial evidence suggests that this has improved the diagnostic accuracy of predicting a difficult airway. Given that one of the limitations of airway POCUS is that it requires a skilled sonographer, and image analysis can be operator dependent, this paper will provide recommendations to standardize the technical aspects of airway ultrasonography and promote further research utilizing sonography in airway management. The goal of this protocol is to educate researchers and medical health professionals and to advance the research in the field of airway POCUS.

Point of care ultrasound (POCUS) is increasingly being utilized in airway management. Presented here are some clinical utilities of POCUS, including differentiating endotracheal and esophageal intubation, identification of the cricothyroid membrane in the event a surgical airway is required, and measuring anterior neck soft tissue to predict difficult airway management.

With its increasing popularity and accessibility, portable ultrasonography has been rapidly adapted not only to improve the perioperative care of ...

Endotracheal Intubation of Rabbits Using a Polypropylene Guide Catheter

Endotracheal intubation in rabbits can be challenging due to their unusual anatomy. Achieving a patent airway during anesthesia is critical for the avoidance of airway obstruction, prevention of gastric tympany, and to allow ventilatory support. Due to the difficulty of intubation, alternative methods such as the use of laryngeal mask airways or laryngeal tubes have been explored. However, these methods do not result in direct access to the trachea and thus may present a risk for development of complications. In addition, lack of direct intubation of the trachea can result in personnel exposure to waste anesthetic gases. Numerous methods for endotracheal intubation have been described, including blind placement, use of a fiberoptic laryngoscope or endoscope, and cricoid placement. Despite these numerous publications, many still struggle to achieve success. Here we provide a detailed description of an intubation technique that can be taught with minimal training with a short time to proficiency. Briefly, after administration of injectable anesthesia and proper positioning of the rabbit, a polypropylene catheter is placed into the trachea by direct visualization using a laryngoscope. The catheter is then used as a guide to direct the endotracheal tube into the trachea. This method allows for intubation without the need for expensive equipment and can be performed by a single individual without the need for an assistant. In conclusion, this technique can be easily taught and performed at very little cost in any clinical or research setting.

Endotracheal intubation in rabbits is challenging due to their unusual anatomy. Here we present a technique for direct intubation of the trachea using a polypropylene catheter as a guide. This method utilizes relatively inexpensive supplies, requires minimal training, and can be easily performed in any clinical setting.

Endotracheal intubation in rabbits can be challenging due to their unusual anatomy. Achieving a patent airway during anesthesia is critical for the ...

Biology

Flexible Bronchoscopy for Novice Bronchoscopists

Systematic Bronchoscopy: the Four Landmarks Approach

Flexible bronchoscopy is a technically difficult procedure and has been identified as the most important procedure that should be integrated into a simulation-based training program for pulmonologists. However, more specific guidelines that govern bronchoscopy training are needed to meet this demand. To ensure patients a competent examination, we propose a systematic, stepwise approach, splitting the procedure into four &#34;landmarks&#34; to support novice endoscopists navigating the bronchial maze. The procedure can be evaluated based on three established outcome measures to ensure a thorough and effective inspection of the bronchial tree: diagnostic completeness, structured progress, and procedure time.
The stepwise approach relying on the four landmarks is used at all simulation centers in Denmark and is being implemented in the Netherlands. To provide instant feedback to novice bronchoscopists when training and to relieve time constraints from consultants, we suggest that future studies should implement artificial intelligence&#160;as a feedback and certification tool when training new bronchoscopists.

Author Spotlight: Learning Systematic Bronchoscopy in a Simulation-Base Setting 

Here, we present a protocol to navigate the bronchial maze in a structured manner, splitting the bronchoscopy into a stepwise approach-the four landmarks approach.

Flexible bronchoscopy is a technically difficult procedure and has been identified as the most important procedure that should be integrated into a ...

Tracheotomy-Based Endotracheal Intubation Protocol for Non-Survival Rat Models

Endotracheal Intubation via Tracheotomy and Subsequent Thoracotomy in Rats for Non-Survival Applications

Endotracheal intubation and subsequent ventilation are often basic requirements for translational research in rat models for various interventions that require controlled or high ventilation pressures or access to the thoracic cavity and organs. Conventional endoorotracheal intubation using the anatomically existing route through the mouth is well suited for survival experiments. However, this procedure poses some challenges, including generally higher levels of the required experience and technical skill, more advanced equipment, and greater time effort with relevant intubation failure rates and complications such as tracheal perforation, temporary systemic hypooxygenation, and relevant aerial leakage.
This manuscript, therefore, presents a detailed step-by-step protocol for endotracheal intubation through tracheotomy in non-survival rat models when guaranteed intubation success, constant oxygenation levels, high ventilation pressures, or open thoracotomy are required.
The protocol emphasizes the importance of meticulous surgical technique to ensure consistent and reliable outcomes, especially for researchers who are inexperienced or lack routine in the technique of endoorotracheal intubation via direct laryngoscopy. This procedure is, therefore, expected to minimize animal suffering and unnecessary animal losses.

Here we introduce a standardized procedure for endotracheal intubation via tracheotomy followed by thoracotomy in rats, aimed at enhancing the precision and reproducibility of non-survival applications requiring invasive ventilation and exposure of thoracic organs in in vivo rat models.

Endotracheal intubation and subsequent ventilation are often basic requirements for translational research in rat models for various interventions that ...

A Minimally Invasive, Visualized Method for Nasojejunal Tube Placement

Malnutrition is a common issue in critically ill patients, often stemming from illness, injury, or surgery. Prolonged fasting leads to intestinal issues, emphasizing the importance of early enteral nutrition, specifically through jejunal nutrition. While enteral nutrition is crucial, complications with current techniques exist. Nasojejunal (NJ) tubes are commonly used, with placement methods categorized as surgical or non-surgical. Non-surgical methods, including endoscopic guidance, have varying success rates, with endoscopic-assisted placement being the most successful but requiring specialized expertise and logistics. 
This study introduces a bedside, visualized method for NJ tube placement to enhance success rates and reduce patient discomfort in the intensive care unit (ICU). In this study involving 19 ICU patients, the method achieved an initial success rate of 94.74% with an average insertion time of 11.2 &plusmn; 6.4 min. This visualized method demonstrates efficiency and reduces the need for additional imaging, and the introduction of a miniaturized endoscope shows promise, enabling successful intubation at the bedside and minimizing patient discomfort. Adjustments to the guidewire lens and catheter are necessary but pose opportunities for future refinements.

This study introduces a bedside visualized method to improve nasojejunal tube placement in intensive care unit patients, enhancing efficiency and reducing patient discomfort.

Malnutrition is a common issue in critically ill patients, often stemming from illness, injury, or surgery. Prolonged fasting leads to intestinal issues, ...

Awake Intubation in Difficult Airways: A Flexible Video Laryngoscope Method

The Flexible Rhino-Laryngoscope for Awake Nasotracheal Intubation

Difficulties or failures in securing the airway still occur and can lead to permanent disabilities and mortality. Patients with head and neck pathologies obstructing airway access are at risk of airway management failure once they lose spontaneous respiration. Awake flexible scope intubation is considered the gold standard for controlling the airway in such patients. Following a feasibility trial involving 25 patients with challenging airways, this article presents a step-by-step protocol for awake nasotracheal intubation using a flexible video rhino-laryngoscope, which is significantly shorter than conventional intubating flexible scopes. The flexible video laryngoscope only exceeds the intubating tube length by a few centimeters, allowing the tube to closely follow the flexible scope during the procedure. Once the scope reaches the pharynx, it can be easily manipulated with one hand, enabling the operator to focus on the safe advancement of the scope-intubating tube assembly through the glottis. Based on previous results and experience gained, this article highlights the potential benefits of the technique: the opportunity for a minimally invasive "quick look" preoperatively to establish a final management plan, a more convenient and safer tool for navigating distorted anatomy with a lower chance of intubating tube impingement and airway injury, and a fast and smooth procedure resulting in improved patient satisfaction.

Author Spotlight: Advancing Awake Nasotracheal Intubation with Flexible Video Rhino-Laryngoscopes

Presented here is a protocol for awake nasotracheal intubation using a flexible rhino-laryngoscope with a 300 mm working length. As this tool is minimally invasive and easy to manipulate, awake intubation performed with a flexible rhino-laryngoscope is well-tolerated, fast, and safe for patients with difficult airways.

Difficulties or failures in securing the airway still occur and can lead to permanent disabilities and mortality. Patients with head and neck pathologies ...

The Rigid Tube as an Alternative in Controlling the Problematic Airway

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