Anterior neck soft tissue measurements on computed tomography to predict difficult laryngoscopy: a retrospective study.

Predicting difficult laryngoscopy is an essential component of the airway management. We aimed to evaluate the use of anterior neck soft tissue measurements on computed tomography for predicting difficult laryngoscopy and to present a clear measurement protocol. In this retrospective study, 281 adult patients whose tracheas were intubated using a direct laryngoscope for thyroidectomy were enrolled. On computed tomography, the distances from the midpoint of the thyrohyoid membrane to the closest concave point of the vallecular (membrane-to-vallecula distance; dMV), and to the most distant point of the epiglottis (membrane-to-epiglottis distance; dME) were measured, respectively. The extended distances straight to the skin anterior from the dMV and dME were called the skin-to-vallecula distance (dSV) and skin-to-epiglottis distance (dSE), respectively. Difficult laryngoscopy was defined by a Cormack-Lehane grade of > 2. Difficult laryngoscopy occurred in 40 (14%) cases. Among four indices, the dMV showed the highest prediction ability for difficult laryngoscopy with an area under the receiver operating characteristic curve of 0.884 (95% confidence interval 0.841-0.919, P < 0.001). The optimal dMV cut-off value for predicting difficult laryngoscopy was 2.33 cm (sensitivity 75.0%; specificity 93.8%). The current study provides novel evidence that increased dMV is a potential predictive indicator of difficult laryngoscopy.

Measurement of subglottic diameter and distance to pre-epiglottic space among Chinese adults.

Proper endotracheal tube (ETT) size selection and identification of potentially difficult airways are important to reduce laryngeal injury during intubation. However, controversies exist concerning transverse subglottic diameter-the narrowest part of the airway-and the distance to pre-epiglottic space. Because few studies have reported the distance from skin to the midpoint of the epiglottis (DSE) among normal individuals, whether the DSE varies between individuals and by ethnicity remains uncertain. The present study aims to investigate the sonographic subglottic diameter and DSE among healthy Chinese adults. Healthy volunteers were recruited at National Taiwan University Hospital between October and November 2019. Exclusion criteria included pre-existing airway or respiratory diseases, neck tumors, and a history of neck operation. Age, sex, height, weight, body mass index (BMI), sonographic DSE, and transverse subglottic diameter were recorded. A total of 124 participants were enrolled. The average age was 32.5 ± 10.4 years and 63 participants (51%) were males. The subglottic diameter was positively associated with sex (males, 14.40 mm; females, 11.10 mm, p < 0.001) and BMI (underweight, 12.13 mm; normal weight, 12.47 mm; overweight, 13.80 mm; obese, 13.67 mm, p = 0.007). Moreover, the DSE was shorter in males (male, 16.18 mm; females, 14.54 mm, p < 0.001) and participants with increased BMI (underweight, 13.70 mm; normal weight, 15.06 mm; overweight, 16.58 mm; obese, 18.18 mm, p < 0.001). As compared with other ethnicity, a smaller size of subglottic diameter and a shorter DSE were noted among Chinese participants, and we suggest that a relatively smaller size of endotracheal tube selection should be considered in tracheal intubations.

Upper airway in children with unilateral cleft lip and palate evaluated with computational fluid dynamics.

INTRODUCTION: Children with unilateral cleft lip and palate (UCLP) exhibit snoring and mouth breathing. They are also reported to show obstructive sleep apnea syndrome. However, their upper airway ventilation condition is not clearly understood. Therefore, this study was performed to evaluate upper airway ventilation condition in children with UCLP with the use of computational fluid dynamics. METHODS: Twenty-one children (12 boys, 9 girls; mean age 9.1 years) with UCLP and 25 children (13 boys, 12 girls; mean age 9.2 years) without UCLP who required orthodontic treatment underwent cone-beam computed tomography (CBCT). Nasal resistance and upper airway ventilation condition were evaluated with the use of computational fluid dynamics from CBCT data. The groups were compared with the use of Mann-Whitney U tests and Student t tests. RESULTS: Nasal resistance of the UCLP group (0.97 Pa/cm3/s) was significantly higher than that of the control group (0.26 Pa/cm3/s; P < 0.001). Maximal pressure of the upper airway (335.02 Pa) was significantly higher in the UCLP group than in the control group (67.57 Pa; P < 0.001). Pharyngeal airway (from choanae to base of epiglottis) pressure in the UCLP group (140.46 Pa) was significantly higher than in the control group (15.92 Pa; P < 0.02). CONCLUSIONS: Upper airway obstruction in children with UCLP resulted from both nasal and pharyngeal airway effects.

Estimation of nares-to-epiglottis distance for selecting an appropriate nasopharyngeal airway.

The nasopharyngeal airway is an important equipment in airway management, a correct placement is crucial for its effectiveness. We measured the nares-to-epiglottis distance (NED) and examined the correlations of the optimal insertion length (NED-1) with patient characteristics and various external facial measurements. We aimed to develop a simple method for estimating the optimal insertion length and to help select an appropriate nasopharyngeal airway.Two hundred patients of ASA grade I & II aged >20 years undergoing elective surgery under general anesthesia were enrolled. We measured nares-to-ear tragus distance (NTD), nares-to-mandibular angle distance (NMD), philtrum-to-ear tragus distance (PTD), and philtrum-to-mandibular angle distance (PMD). The NED was measured by fiber-optic bronchoscope. All measurements were obtained in centimeters. NED-1 (cm) was defined as the optimal insertion length. The patient's sex, age, body weight, body height, and body mass index were recorded.The NED-1 significantly correlated with body weight, body height, NTD, NMD, PTD, and PMD. Backward stepwise multiple linear regression analysis yielded the formula for predicting NED-1: 0.331 - 0.018 × BW + 0.061 × BH + 1.080 × NMD - 1.256 × PMD + 0.697 × PTD (r = 0.640, P < .001). The regression lines of the optimal insertion length versus PTD showed the best fit to the equality line. The measurements of PTD showed the minimal differences from NED-1 and with the most patients showing <1 cm differences from NED-1.The optimal insertion depth of nasopharyngeal airway can easily be predicted by the distance from philtrum-to-ear tragus, and a nasopharyngeal airway of an appropriate size can be selected accordingly.

Evaluation of Normal Epiglottis on Computed Tomography with Special Attention to Thickness.

To our knowledge, this is the first study to investigate the thickness of the normal epiglottis on computed tomography (CT) in a Japanese population. The focus was on determining the thickness of a normal epiglottis, which could then serve as a reference in detecting abnormalities. We believe that this would facilitate diagnosing and determining the extent of cancerous invasion of the supraglottis and secondary invasion of the epiglottis. This retrospective study was based on a review of radiographic data in patient charts. Cervical CT scans obtained from 79 Japanese patients (44 men [55.7%] and 35 women [44.3%]; age range, 28-85 years; mean, 58.9 years) showing a normal epiglottis under laryngoscopy were evaluated. The thickness of the epiglottis was measured on CT scans and the results analyzed with the Student's t-test, an analysis of variance, and the Tukey-Kramer test. The epiglottis in men was significantly thicker than that in women (p<0.05). A statistically significant difference was observed in thickness depending on longitudinal height (p=<0.001). The thickness at the median was larger than that bilaterally in all patients (p=<0.001). No statistically significant difference was observed in thickness depending on side or age. The thickness of the normal epiglottis was established at each level. We believe that these data could serve as a reference in diagnosing and detecting abnormalities of the epiglottis.

Radiologic indicators for prediction of difficult laryngoscopy in patients with cervical spondylosis.

BACKGROUND: We identified the most useful variables for prediction of difficult laryngoscopy in patients with cervical spondylosis according to physical indicators and preoperative skeletal X-ray and soft tissue MRI measurements. We hypothesized that there was a closer association between difficult laryngoscopy and radiologic indicators. METHODS: We randomly enroled 315 patients undergoing elective cervical spine surgery and analysed the radiological and physical data in predicting difficult laryngoscopy. RESULTS: We identified five variables that were most useful in predicting difficult laryngoscopy: the inter-incisor gap (P = 0.006), modified Mallampati test score (P = 0.004), distance from the highest point of the hyoid bone to the mandibular body (P < 0.001), most antero-inferior point of the upper central incisor tooth (P < 0.001), and length of the epiglottis (P = 0.002). Binary multivariate logistic regression analyses identified three factors that were independently associated with difficult laryngoscopy: the Mallampati score, distance from the hyoid bone to the mandibular body, and the anterior-inferior point of the upper central incisor tooth. The odds ratios and 95% confidence intervals were 1.547 (1.029-2.327), 1.222 (1.139-1.310), and 1.224 (1.133-1.322), respectively. The AUC for hyoid bone distance to mandibular body (0.832) was larger than that of anterior-inferior point of the upper central incisor tooth (0.802, P > 0.05) and that of modified Mallampati test (0.602, P < 0.05). CONCLUSION: Distance from the highest point of the hyoid bone to the mandibular body appears to be the most accurate indicator for difficult laryngoscopy in patients with cervical spondylosis.

Surface anatomy of major anatomical landmarks of the neck in an adult population: A Ct Evaluation of Vertebral Level.

To compare the projectional surface anatomy of healthy individuals in an adult population with those with a thyroid mass, using computed tomography (CT). Sixteen slice CT images of 101 individuals were analyzed using a 32-bit Radiant DICOM viewer to establish the relationships among major anatomical landmarks in the neck and their vertebral levels. The structures investigated included: hard palate (HP), hyoid bone (HB) including body and lesser horns, soft palate (SP), thyroid gland (TG) (both superior and inferior poles), thyroid gland anteroposterior (APD) and superoinferior (SID) diameters, thyroid isthmus (TI) superoinferior dimension, epiglottis, vertebral arteries (right and left), and both right and left parotid glands (superior and inferior extents). The vertebral levels noted most frequently were: body of hyoid bone (C4, 42.71%); lesser horns of hyoid bone (C3, 36.46%); thyroid gland superior pole (C6, 31.25%); and thyroid gland inferior pole (T2, 30.2%). TG-ID, TG-APD, and TG-SID were not significantly different between males and females in the healthy group; however, there was a significant gender difference in thyroid gland inferior diameter in the pathology group [males 2.16(±1.16) vs. females 3.37(±1.30), P = 0.01, paired sample t-test]. Further studies are needed to determine whether neck pathology in those with a thyroid mass affects the dimensions of the thyroid gland. Moreover, the surface anatomy of the neck should be revisited using modern imaging techniques to address inconsistencies in anatomy and clinical reference texts. Clin. Anat. 30:781-787, 2017. © 2017Wiley Periodicals, Inc.

Tongue Size and Posterior Airway Space Changes in Class III Malocclusion After Maxillomandibular Surgery: A Retrospective Study.

The purpose of this study was to evaluate the changes in the airway space after surgical correction of Class III skeletal dentofacial deformity and to determine if orthognathic surgery alters the airway space and improves obstructive sleep apnea. Twenty-four Class III adults treated with orthognathic surgery were divided into two groups as Mandibular set-back (Bilateral Sagittal Split Osteotomy-BSSO, 10 patients) and two jaw surgery (Bilateral Sagittal Split Osteotomy combined with Le Fort I maxillary advancement, 14 patients). Lateral cephalometric radiographs were traced before (T0) and 6 months after surgery (T1). Steiner and McNamara analysis, linear pharyngeal airway measurements (PNS-PPW1, SPT-PPW2, E-PPW3, PNS-SPT), tongue volume measurements (TH, Tt-Eb) and pharyngeal area measurements (nasopharyngeal, upper oropharyngeal, lower oropharyngeal, epiglottis area) were performed. The data obtained was analyzed statistically by repeated measurement ANOVA and Duncan's test. The increase of PNS-PPW1 was important in two jaw surgery group (p < 0.05). The nasopharyngeal area was statistically different between T0 and T1 (p < 0.01), and the lower oropharyngeal area was statistically significant between BSSO and two jaw surgery groups (p < 0.05). Surgical correction of Class III skeletal dentofacial deformity alters posterior airway dimensions. Two jaw surgery is advantageous considering the risk for obstructive sleep apnea, because it evokes an increase in the upper pharyngeal airway dimensions. Keywords: Tongue size, posterior airway space, maxillomandibular surgery.

Comparison of the laryngoscopy views with the size 1 Miller and Macintosh laryngoscope blades lifting the epiglottis or the base of the tongue in infants and children <2 yr of age.

BACKGROUND: Miller laryngoscope blades are preferred for laryngoscopy in infants and children <2 yr of age. Despite their long history, the laryngeal view with the Miller blade size 1 has never been compared with that with the Macintosh (MAC) blade in children. This prospective, single-blinded, randomized study was designed to compare the laryngeal views with the size 1 Miller and MAC blades in children <2 yr. METHODS: With IRB approval, 50 ASA I and II children <2 yr undergoing elective surgery were enrolled. After an inhalation induction and neuromuscular block with i.v. rocuronium 0.5 mg kg(-1), two laryngeal views were obtained with a single blade (Miller or MAC) in each child: one lifting the epiglottis and another lifting the tongue base. The best laryngeal views in each blade position were photographed with a SONY(®) Cyber-shot camera and rated by a blinded anaesthesiologist using the percentage of glottic opening scale. RESULTS: The scores with the Miller blade lifting the epiglottis and the MAC blade lifting the tongue base were similar. The scores with the Miller blade lifting the epiglottis and the tongue base were similar. The scores for the MAC blade lifting the tongue base were greater than those lifting the epiglottis (95% confidence interval: 7.6-26.8) (P=0.0004). CONCLUSIONS: In infants and children <2 yr of age, optimal laryngeal views may be obtained with either the Miller size 1 blade lifting the epiglottis or with the Miller or MAC blades lifting the tongue base. CLINICAL TRIAL REGISTRATION: NCT01717872 at Clinical Trials.gov.

Is video laryngoscope-assisted flexible tracheoscope intubation feasible for patients with predicted difficult airway? A prospective, randomized clinical trial.

BACKGROUND: Failed intubation may result in both increased morbidity and mortality. The combination of a video laryngoscope and a flexible tracheoscope used as a flexible video stylet may improve the success rate of securing a difficult airway. We tested the hypothesis that this combination is a feasible way to facilitate intubation in patients with a predicted difficult airway in that it will shorten intubation times and reduce the number of intubation attempts. METHODS: We conducted a randomized, prospective trial in 140 patients with anticipated difficult airways undergoing elective or urgent surgery. After insertion of video laryngoscope, patients were randomly assigned to either having their tube placed with the use of a preformed stylet (control group) or with a flexible tracheoscope (intervention group). The primary outcome measures were time to successful intubation and number of intubation attempts. RESULTS: The number of intubations requiring 2 or more intubation attempts was similar in the 2 groups (14% control vs 13% intervention, P = 1.0); the number of patients requiring 3 or more intubation attempts was not significantly different (8.6% control vs 1.4% intervention, P = 0.12). Distribution for time to intubation also did not differ between the control (median of 66 seconds, interquartile range 47-89) and the intervention group (median of 71 seconds, interquartile range 52-100; P = 0.35). In the control group, 4 patients, all with cervical spine pathology, had the trachea intubated successfully with the video laryngoscope plus flexible tracheoscope after 3 failed attempts with video laryngoscope and rigid stylet. For these 4 patients, time from the decision to change the intubation method to successful intubation with a flexible tracheoscope was 36 ± 14 seconds. Overall success probability for cervical spine patients was 100% (20/20) in the intervention group and 80% (16/20) in the control group, with an exact 95% confidence interval for the difference of 1.4% to 44%, P = 0.04. CONCLUSIONS: Flexible tracheoscope-assisted video laryngoscopic intubation is a feasible alternative to video laryngoscope only intubation in patients with predicted difficult airways. A flexible tracheoscope used in combination with video laryngoscope may also further increase the success rate of intubation in select patients with a proven difficult airway, particularly when in-line stabilization is required.

Estimation of the nares-to-epiglottis distance and the nares-to-vocal cords distance in young children.

BACKGROUND: Estimation of the nares-to-epiglottis and nares-to-vocal cords distances would facilitate the selection of properly sized nasopharyngeal airways and appropriate positioning of a fibreoptic bronchoscope in young children. The purposes of this study were to measure the nares-to-epiglottis and nares-to-vocal cords distances and to create an algorithm to predict these distances based on anatomical landmarks and paediatric characteristic data. METHODS: Two hundred and eleven children, aged 1-10 yr, undergoing elective surgery were investigated. After induction of general anaesthesia, the distances from the nares to the epiglottis/vocal cords were measured using a nasogastric tube. After intubation, the distances from the lateral border of the nose to the ipsilateral mandible angle (nares-to-mandible distance) and the tragus of the ear (nares-to-tragus distance) were measured using a tape measure. RESULTS: The nares-to-epiglottis and nares-to-vocal cords distances were significantly correlated with the age, weight, height, and external measurements (P<0.001). By stepwise multiple linear regression analysis, formulas were obtained for the nares-to-epiglottis distance (cm)=2.606+0.058×height (cm)+0.231×the nares-to-mandible distance (cm)-0.304 (gender) (r(2)=0.754) and for the nares-to-vocal cords distance (cm)=4.947+0.06×height (cm)+0.228×nares-to-mandible distance (cm)-0.283 (gender) (r(2)=0.803). CONCLUSIONS: The nares-to-epiglottis and nares-to-vocal cords distances can be predicted using the height and the nares-to-mandible distance in young children. CLINICAL TRIAL REGISTRATION NUMBER: Clinical Research Information Service KCT0000150.

A clinical evaluation of the I-gel ™ supraglottic airway device in children.

BACKGROUND: The i-gel(TM) is one of the latest commercially available, second-generation supraglottic airway devices (SADs). Specific features include a distal cuff made of a thermoplastic elastomer gel that does not require inflation and a gastric side channel to allow passage of a gastric tube, venting of gas from the stomach, and an early indication of regurgitation. Previous studies in older children and adults have shown that it is a reliable, efficient, and safe device for airway management. METHODS: We evaluated the i-gel(TM) in sizes ranging from 1 to 2.5 in children considered suitable for a supraglottic device. We assessed successful rates of insertion, airway leak pressure, position confirmed by fiberoptic laryngoscopy, gastric tube placement, manipulations required, and complications. RESULTS: The i-gel(TM) was used in 154 children over a period of 12 months. The median age [interquartile range (IQR)] was 4 years 11 months (2-7 years), median weight (IQR) 19 kg (13-26), and median (IQR) duration of procedure 29 (30-45) min. First insertion attempt was successful in 93.5% of patients, and second attempt in 5.8%. The median (IQR) time to insertion was 14 (13-16) s. The median (IQR) leak pressure was 20 (15-25) cmH(2) 0. Gastric tube placement was successful in 90% of cases. On fiberoptic examination, the vocal cords were visible in 97% of patients. Complications arose in 20% of patients, but the majority were minor. Anesthetists commented that the device had a tendency to displace upward out of the mouth and that extension toward the forehead and flexion toward the feet of the proximal tube altered the quality of the airway. Overall, in seven (4.5%) patients, the device was abandoned and an alternative airway was used. CONCLUSIONS: Pediatric i-gel(TM) sizes 1.5-2.5 provided a satisfactory airway during anesthesia for spontaneously breathing infants and children. However, to ensure a clear airway, considerable vigilance is required when fixing the device in the mouth and to avoid the negative effects of flexion of the proximal tubing. The i-gel(TM) is more expensive than first-generation devices. Whether this additional cost for the potential benefit of greater airway protection is considered acceptable will depend on longer-time evaluation and surveillance to establish overall safety.

Parker Flex-Tip Tube® provides higher intubation success with the Pentax-AWS Airwayscope® despite the AWS tip being inserted into the vallecula.

The Parker Flex-Tip(®) tube, in combination with the Pentax-Airwayscope(®) (AWS), is anecdotally reported to facilitate intubation when the AWS tip fails to be inserted behind the epiglottis. We examined whether the Parker tube facilitates intubation when the AWS tip is inserted into the vallecula. Forty patients were randomly assigned into either the standard or Parker tube group. Following general anesthesia induction, AWS intubation was attempted with the blade tip inserted into the vallecula. After obtaining an optimal laryngeal view, the tube was advanced toward the glottis. The laryngoscopist allowed additional adjustment of the blade tip direction when the first tube insertion failed because of involvement or folding of the epiglottis resulting from advancement of the tube. The primary outcome was defined as the success rate for intubation and secondary outcome as the time needed for tube placement. The Parker tube provided both a higher intubation success rate (17/20 vs. 4/20, P < 0.01), and a faster intubation time (17 ± 5 s vs. 25 ± 4 s, P < 0.01), than the standard tube. We conclude the use of the Parker tube in combination with the AWS is an optional technique allowing the laryngoscopist to obtain more reliable intubation success despite insertion of the AWS tip into the vallecula.

The laryngeal saccule: clinical significance.

The association between the laryngeal saccule and a laryngocele is an important clinical relationship. Here, we describe this and other clinical correlations of the saccule including infection and carcinoma and suggest that these should be discussed in medical gross anatomy courses. We also briefly present some descriptive information on the anatomy and function of the saccule in humans and other higher primates.

Ultrasonographic modification of Cormack Lehane classification for pre-anesthetic airway assessment.

BACKGROUND: The major drawback of Cormack Lehane classification for airway assessment is its dependence on invasive direct laryngoscopy and hence it is inapplicable for pre-anesthetic assessment of airway in patients with no prior history of tracheal intubation. STUDY OBJECTIVES: The purpose of the study was to compare and correlate the ultrasound view of the airway and the Cormack Lehane classification of the direct laryngoscopy. METHODS/STUDY PROCEDURES: The present study was conducted on patients scheduled for elective surgery and requiring general anesthesia with direct laryngoscopy and endotracheal intubation. In the pre-operative holding area, the following measurements were obtained with the oblique-transverse ultrasound view of the airway: (a) the distance from the epiglottis to the midpoint of the distance between the vocal folds, (b) the depth of the pre-epiglottic space, and (c) the total time taken by the operator to achieve the final ultrasonic image. The data was then compared with the Cormack Lehane classification during direct laryngoscopy in the operating room. Subsequently based on the correlation data, the ultrasonographic modification of Cormack-Lehane Classification was developed. RESULTS: It was observed that there was a correlation of the distance between the epiglottis and the vocal cords (E-VC) with the Cormack Lehane Grading; correlation was strong negative with regression coefficient of -0.966 (95% CI -1.431 to -0.501; p = 0.0001). Subsequently, the correlation of the pre-epiglottis space (Pre-E) with the Cormack Lehane Grading was strong in positive direction with regression coefficient of0.595 (95% CI 0.261 to 0.929; p = 0.0008). Finally the ratio of Pre-E and E-VC distances with the Cormack Lehane Grading had the strongest positive correlation with regression coefficient of 0.495 (95% CI 0.319 to 0.671; p < 0.0001). Based on these statistical calculations and after rearranging the data, we found that prediction of Cormack Lehane (CL) grades can be adequately (67%-68% sensitivity) made by the ratio of Pre-E and E-VC distances (Pre-E/E-VC) {0 < [Pre-E/E-VC] < 1 approximately CL grade 1; 1 < [Pre-E/E-VC] < 2 approximately CL grade 2; and 2 < [Pre-E/E-VC] < 3 approximately CL grade 3}. The average time taken to complete the ultrasound examination of airway in the preoperative area was 31.7 +/- 12.4 seconds. CONCLUSION: The non-invasive ultrasonographic modification of invasive Cormack Lehane classification for pre-anesthetic airway assessment can supplement the presently available noninvasive modalities of pre-anesthetic airway assessment including the Mallampati Classification.

Measurements of normal upper airway assessed by 3-dimensional computed tomography in Chinese children and adolescents.

OBJECTIVE: To establish normative data of upper airway dimensions in Chinese children and adolescents by age and sex. METHODS: CT-scans of 281 Chinese children and adolescents (140 girls, 141 boys) aged from 6 to 18 years (yr) were selected among the patients who visited in Department of Oral and Maxillofacial Surgery from September 2009 to August 2010. Child was defined as 6-12 yr, and adolescent as 13-18 yr. All the subjects were divided into 4 groups according to age as 6-9, 10-12, 13-15 and 16-18. The upper airway was divided into four distinct anatomic regions: the nasopharynx, the palatopharynx, the glossopharynx and the epiglottic region. Using 3-dimension image processing software, the minimal cross-sectional area with its sagittal diameter and transversal diameter, length and volume of upper airway segmentations were measured. RESULTS: There was no difference in all parameters of segmentations between genders in children. In adolescents the differences of airway parameters were evident between genders. Male adolescents' upper airway were bigger and longer than female's. Volumes and lengths of segmentations were increased with age in male and female respectively. CONCLUSIONS: Norms for upper airway in Chinese children and adolescents assessed by 3-D reconstruction computed tomography have been established. Volume and other dimension of upper airway are increased with age. Significant sex dimorphisms in upper airway dimension are evident in adolescents.