Incomplete sealing of tracheal diverticula by a tracheal tube cuff during positive-pressure ventilation causes barotrauma but the concrete possibility of incomplete sealing has not been indicated. We aimed to assess the possibility of incomplete sealing in a simulated situation of tracheal intubation for patients with tracheal diverticula with tube fixation where the tracheal tube\'s vocal cord guide overlaps with the patient\'s vocal cord.
We retrospectively assessed the characteristics of tracheal diverticula based on thoracic computed tomography data in our institution from January 2018 to July 2020. Then, we assessed the structural parameters of three single-lumen tracheal tubes (Parker Flex-Tip [Parker Medical, Bridgewater, CT, USA], Portex Soft Seal [ICU Medical, San Clemente, CA, USA], and Shiley TaperGuard [Medtronic, Dublin, Ireland]; 6.0-8.0 mm inner diameter size) and simulated the positional relationships between tracheal diverticula and the tracheal tube during tracheal intubation where the vocal cord guide overlaps with the patient\'s vocal cord. We assessed each tube product\'s possibility of incompletely sealing tracheal diverticula and the possibility of unintended bronchial intubation.
In 5,854 patients, the prevalence of tracheal diverticula was 5.7%. The mean (SD) length from the vocal cord to the distal end of the tracheal diverticula was 52.2 (12.8) mm. Tracheal tubes with length from the distal end of the tracheal cuff to the vocal cord guide of ≥ 70 mm had a low risk of incompletely sealing tracheal diverticula (< 5%) and length from the distal end of the tube to the vocal cord guide of ≤ 95 mm had a low risk of unintended bronchial intubation (< 5%). No products in this study satisfied both outcomes.
Tube fixation, where the vocal cord guide overlaps with the patient\'s vocal cord, is associated with risk of incompletely sealing of tracheal diverticula depending on the tube\'s manufacturer and tube\'s inner diameter size, although it was not a high risk. The use of small inner diameter sized tube relative to patient\'s body size is high risk of incomplete sealing of tracheal diverticula.
This trial was prospectively registered at University Hospital Medical Information Network (UMIN).
UMIN000043317 (URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000048055 ).

Flexible bronchoscope-guided tracheal intubation through supraglottic airway devices (SGAs) is a well-established element of difficult intubation algorithms. Success can be limited by dimensional incompatibilities between tracheal tubes (TTs) and SGAs.
In this in vitro study, we tested the feasibility of TT passage through SGAs, removal of SGAs over TTs, and the ability to guide the flexible bronchoscope with 13 TT brands (internal diameter, 6.5-8.0 mm) and ten different SGAs (#4 and #5) in an intubation mannequin.
We tested 1,040 combinations of SGAs and TTs. Tracheal tube passage failed in 155 (30%) combinations of the five tested first-generation SGAs (117 [46%] with SGA #4, 38 [15%] with SGA #5) and in three (0.6%) combinations of the five tested second-generation SGAs (two [0.8%] with SGA #4 and one [0.4%] with SGA #5). The reason for failed passage of a TT through a first-generation SGA consistently was a too-narrow SGA connector. Removal of the SGA over the TT in the 882 remaining combinations was impossible for all sizes of reinforced TTs, except the Parker Reinforced TT, and was possible for all non-reinforced TTs. Only one combination with SGA #4 and 84 combinations with SGA #5 were not ideal to adequately guide the flexible bronchoscope.
Clinically relevant combinations of adult-size TTs and SGAs can be incompatible, rendering flexible bronchoscope-guided tracheal intubation through an SGA impossible. Additional limitations exist regarding removal of the SGA and maneuverability of the flexible bronchoscope.
RéSUMé: CONTEXTE: L’intubation endotrachéale guidée par bronchoscope flexible via un dispositif supraglottique (DSG) est un élément établi des algorithmes utilisés pour les intubations difficiles. La réussite de l’intubation peut être limitée par des incompatibilités dimensionnelles entre les tubes endotrachéaux (TET) et les DSG. MéTHODE: Dans cette étude in vitro, nous avons testé la faisabilité de faire passer un TET par un DSG, le retrait du DSG par-dessus le TET et la possibilité de guider un bronchoscope flexible avec 13 marques de TET (diamètre interne, 6,5-8,0 mm) et dix DSG différents (#4 et #5) sur un mannequin d’intubation. RéSULTATS: Nous avons testé 1040 combinaisons de DSG et de TET. Le passage du tube endotrachéal a échoué dans 155 (30 %) combinaisons avec les cinq DSG de première génération testés (117 [46 %] avec DSG #4, 38 [15 %] avec DSG #5) et dans trois (0,6 %) combinaisons avec les cinq DSG de deuxième génération testés (deux [0,8 %] avec DSG #4 et une [0,4 %] avec DSG #5). La raison de l’échec du passage d’un TET à travers un DSG de première génération était systématiquement liée à un connecteur de DSG trop étroit. Dans les 882 combinaisons restantes, le retrait du DSG par-dessus le TET s’est avéré impossible avec toutes les tailles de TET armés, à l’exception du TET armé Parker, et était possible avec tous les TET non armés. Une seule combinaison avec le DSG #4 et 84 combinaisons avec le DSG #5 n’étaient pas idéales pour guider le bronchoscope flexible de manière adéquate. CONCLUSION: Les combinaisons cliniquement pertinentes de TET et de DSG de tailles adultes peuvent être incompatibles, rendant impossible l’intubation endotrachéale guidée par bronchoscope flexible via un DSG. D’autres limites existent en ce qui concerne le retrait du DSG et la maniabilité du bronchoscope flexible.

BACKGROUND: We examined the association between emergent postoperative tracheal intubation and the use of supraglottic airway devices (SGAs) vs tracheal tubes.
METHODS: We included data from adult noncardiac surgical cases under general anaesthesia between 2008 and 2018. We only included cases (n=59 991) in which both airways were deemed to be feasible options. Multivariable logistic regression, instrumental variable analysis, propensity matching, and mediation analysis were used.
RESULTS: Use of a tracheal tube was associated with a higher risk of emergent postoperative intubation (adjusted absolute risk difference [ARD]=0.80%; 95% confidence interval (CI), 0.64-0.97; P<0.001), and a higher risk of post-extubation hypoxaemia (ARD=3.9%; 95% CI, 3.4-4.4; P<0.001). The effect was modified by the use of non-depolarising neuromuscular blocking agents (NMBAs); mediation analyses revealed that 28.9% (95% CI, 14.4-43.4%; P<0.001) of the main effect was attributable to NMBA. Airway management modified the association of NMBA and risk of emergent postoperative intubation (Pinteraction=0.02). Patients managed with an SGA had higher odds of NMBA-associated reintubation compared to patients managed with a tracheal tube (adjusted odds ratio [aOR]=3.65, 95% CI, 1.99-6.67 vs aOR=1.68, 95% CI, 1.29-2.18 [P<0.001], respectively).
CONCLUSIONS: In patients undergoing procedures under general anaesthesia that could be managed with either SGA or tracheal tube, use of an SGA was associated with lower risk of emergent postoperative intubation. The effect can partly be explained by use of NMBAs. Use of NMBAs in patients with an SGA appears to increase the risk of emergent postoperative intubation.

OBJECTIVE: Poor monitoring of tracheal tube cuff pressure may result in patient complications. The objective method of using a manometer is recommended to keep safe cuff pressure values (20-30 cm H2O). However, as manometers are not readily available, anesthesiologists use subjective methods. We aimed to assess appropriateness of a subjective method for attaining cuff pressure and the expertise level of manometer handling among anesthesiology staff and residents in a university teaching hospital.
METHODS: Prospective observational study, recruiting participants that performed tracheal intubation and the subjective method for tube cuff inflation. Patients with difficult airway, larynx and trachea anatomic abnormality and emergency procedures were not included. Up to 60 minutes after tracheal intubation, an investigator registered the cuff pressure using an aneroid manometer (AMBU®) connected to the tube pilot balloon.
RESULTS: Forty-seven anesthesiologists were included in the study - 24 residents and 23 staff. Mean (SD) and medians (IQR) measured in cm H2O were, respectively, 52.5 (27.1) and 50 (30-70). We registered 83% of measurements outside the recommended pressure range, with no difference between specialists and residents. The level of expertise with the objective method was also similar in both groups. Pressure adjustments were performed in 76.6% of cases.
CONCLUSIONS: The subjective method for inflating the tracheal tube cuff resulted in a high rate of inadequate cuff pressures, with no difference in performance between anesthesiology specialists and residents.

Anaesthesia and positive pressure ventilation cause ventral redistribution of regional ventilation, potentially caused by the tracheal tube. We used electrical impedance tomography to map regional ventilation during anaesthesia in 10 patients with and without a tracheal tube. We recorded impedance data in subjects who were awake, during bag-mask ventilation, with the tracheal tube positioned normally, rotated 90° to each side and advanced until in an endobronchial position. We recorded the following measurements: ventilation of the right lung (proportion, %); centre of ventilation (100% = entirely ventral); global inhomogeneity (0% = homogenous); and regional ventilation delay, an index of temporal heterogeneity. We compared the results using Student\'s t-tests. Relative to subjects who were awake, anaesthesia with bag-mask ventilation reduced right-sided ventilation by 5.6% (p = 0.002), reduced regional ventilation delay by 1.6% (p = 0.025), and moved the centre of ventilation ventrally from 51.4% to 58.2% (p = 0.0001). Tracheal tube ventilation caused a further centre of ventilation increase of 1.3% (p = 0.009). With the tube near the carina, right-sided ventilation increased by 3.2% (p = 0.031) and regional ventilation delay by 2.8% (p = 0.049). Tube rotation caused a 1.6% increase in right-sided ventilation compared with normal position (p = 0.043 left and p = 0.031 right). Global inhomogeneity remained mostly unchanged. Ventral ventilation with positive pressure ventilation occurred with bag-mask ventilation, but was exacerbated by a tracheal tube. Tube position influenced ventilation of the right and left lungs, while ventilation overall remained homogenous. Tube rotation in either direction resulted in ventilation patterns being closer to when awake than either bag-mask ventilation or a normally positioned tube. These results suggest that even ideal tube positioning cannot avoid the ventral shift in ventilation.

Clinicians sometimes encounter resistance in advancing a tracheal tube, which is inserted via a nostril, from the nasal cavity into the oropharynx during nasotracheal intubation. The purpose of this study was to investigate the effect of neck extension on the advancement of tracheal tubes from the nasal cavity into the oropharynx during nasotracheal intubation.
Patients were randomized to the \'neck extension group (E group)\' or \'neutral position group (N group)\' for this randomized controlled trial. After induction of anesthesia, a nasal RAE tube was inserted via a nostril. For the E group, an anesthesiologist advanced the tube from the nasal cavity into the oropharynx with the patient\'s neck extended. For the N group, an anesthesiologist advanced the tube without neck extension. If the tube was successfully advanced into the oropharynx within two attempts by the same maneuver according to the assigned group, the case was defined as \'success.\' We compared the success rate of tube advancement between the two groups.
Thirty-two patients in the E group and 33 in the N group completed the trial. The success rate of tube passage during the first two attempts was significantly higher in the E group than in the N group (93.8% vs. 60.6%; odds ratio = 9.75, 95% CI = [1.98, 47.94], p = 0.002).
Neck extension during tube advancement from the nasal cavity to the oropharynx before laryngoscopy could be helpful in nasotracheal intubation.
ClinicalTrials.gov Identifier NCT03377114 , registered on 13 December 2017.

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0-16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time-points: during volume-controlled ventilation 6 ml.kg-1 , PEEP 5 cmH2 O and during pressure-controlled ventilation 10 cmH2 O / PEEP 5 cmH2 O. The pressure-controlled ventilation measurement time-points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume-controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg-1 , median (IQR [range]) 0.20 (0.13-0.39 [0.04-0.60]) vs. 0.82 (0.58-1.38 [0.24-4.85]), respectively, p < 0.001. With pressure-controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30-min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30-min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short-term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long-term follow-up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

OBJECTIVE: Aspiration pneumonia is a complication of tracheal intubation and mechanical ventilation. We hypothesized that tracheal tubes removed after anesthesia that have an acidic pH may reflect latent regurgitation of gastric fluid.
METHODS: A prospective observational study.
METHODS: Operating room.
METHODS: Tracheal tubes removed from 200 patients (age range, 20-85 years) who had undergone general anesthesia with tracheal intubation and gastric tube placement were examined.
METHODS: To detect regurgitated gastric fluid on the tubes, we measured pH at 5 different points along the tubes and in the water in which the removed tracheal tubes were immersed.
RESULTS: Of the 200 removed tracheal tubes, 5 had an acidic pH. The tubes were used in patients who were in the prone (1 patients) or head-down (4 patients) position while under anesthesia. The incidence of acidic pH was significantly higher in patients who were in the prone (1/32) or head-down (4/56) position, compared with those in the supine (0/92) or lateral (0/20) position (P<.05).
CONCLUSIONS: Acidic pH was found on about 2.5% of removed tracheal tubes. These tubes were used in patients who were in the prone or head-down position during general anesthesia, although they did not exhibit significant aspiration symptom. Anesthesiologists should be aware of the inherent risk of gastric fluid regurgitation when their patients undergo general anesthesia in these positions.

BACKGROUND: Incorrect endobronchial placement of the tracheal tube can lead to serious complications. Hence, it is necessary to determine the accuracy of tracheal tube positioning. Markers are included on tracheal tubes, in the process of their manufacture, as indicators of approximate intubation depth. In addition, continuous chest auscultation has been used for determining the proper position of the tube. We examined insertion depth using the cuff depth and continuous chest auscultation method (CC method), compared with insertion depth determined by the marker method, to assess the accuracy of these methods.
METHODS: After induction of anesthesia, tracheal intubation was performed in each patient. In the CC method, the depth of tube insertion was measured when the cuff had passed through the glottis, and again when breath sounds changed in quality; the depth of tube insertion was determined from these values. In the marker method, the depth of tube insertion was measured and determined when the marker of the tube had reached the glottis, using insertion depth according to the marker as an index.
RESULTS: Insertion depth by the marker method was 26.6 ± 1.2 cm and by the CC method was 28.0 ± 1.2 cm (P < 0.0001). The CC method indicated a significantly greater depth than the marker method.
CONCLUSIONS: This study determined the safe range of tracheal tube placement. Tube positions determined by the CC method were about 1 cm deeper than those determined by the marker. This information is important to prevent accidental one-lung ventilation and accidental extubation.
BACKGROUND: UMIN No. UMIN000011375.

BACKGROUND: The main function of an endotracheal tube (ETT) cuff is to prevent aspiration. High cuff pressure is usually associated with postoperative complications. We tried to compare cuff inflation guided by pressure volume loop closure (PV-L) with those by just to seal technique (JS) and assess the postoperative incidence of sore throat, cough and hoarseness.
METHODS: In a prospective, randomized clinical trial, 100 patients\' tracheas were intubated. In the first group (n = 50), ETT cuff inflation was guided by PV-L, while in the second group (n. = 50) the ETT cuff was inflated using the JS technique. Intracuff pressures and volumes were measured. The incidence of postoperative cuff-related complications was reported.
RESULTS: Demographic data and durations of intubation were comparable between the groups. The use of PV-L was associated with a lesser amount of intracuff air [4.05 (3.7-4.5) vs 5 (4.8-5.5), P < 0.001] and lower cuff pressure than those in the JS group [18.25 (18-19) vs 33 (32-35), P ≤ 0.001]. The incidence of postextubation cuff-related complications was significantly less frequent among the PV-L group patients as compared with the JS group patients (P ≤ 0.009), except for hoarseness of voice, which was less frequent among the PV-L group, but not statistically significant (P ≤ 0.065). Multiple regression models for prediction of intra-cuff pressure after intubation and before extubation revealed a statistically significant association with the technique used for cuff inflation (P < 0.0001).
CONCLUSIONS: The study confirms that PV-L-guided ETT cuff inflation is an effective way to seal the airway and associates with a lower ETT cuff pressure and lower incidence of cuff-related complications.