Estimation of the length of the nares-vocal cord

Accidental retropharyngeal dissection extending close to the right common carotid artery during nasotracheal intubation: a case report

BACKGROUND

Retropharyngeal dissection is a possible complication during nasotracheal intubation. We report a case of a retropharyngeal dissection extending close to the right common carotid artery occurring while inserting a nasotracheal tube.

CASE PRESENTATION

An 81-year-old woman, scheduled for laparoscopic and endoscopic cooperative surgery for a duodenal tumor under general anesthesia, sustained submucosal dissection of the retropharyngeal space during nasotracheal intubation. Postoperative computed tomography revealed retropharyngeal tissue injury extending close to the right common carotid artery. The patient was treated with prophylactic antibiotic therapy and discharged uneventfully on postoperative day 13.

CONCLUSIONS

Submucosal dissection of the retropharyngeal tissue during nasotracheal intubation has a potential risk of major cervical vessel injury. Therefore, when the tip of the tube cannot be visualized within the oropharynx, clinicians must proceed with caution regarding the expected depth of the tube.

Comparison of the selection of nasotracheal tube diameter based on the patient's sex or size of the nasal airway: A prospective observational study

When selecting the nasotracheal tube diameter for nasotracheal intubation, atraumatic introduction of the tube through the nasal passage and a safe location of the tube's cuff and tip should be ensured simultaneously. To maintain safety margin for the tube's cuff and tip from the vocal cords and carina (2 cm and 3 cm, respectively), the maximum allowable proximal-cuff-to-tip distance was calculated as 5 cm less than the measured vocal cords-to-carina distance. The primary aim of this study was to find a single predictive preoperative factor of the nostril size and maximum allowable proximal-cuff-to-tip distance of nasotracheal tubes. The secondary aim was to compare the difference in the safety margin between the maximum allowable proximal-cuff-to-tip distance based on the patient's airway and the actual proximal-cuff-to-tip distance of the selected tube. We used fiberoptic bronchoscope to measure the distance from the vocal cords to the carina for the calculation of the maximum allowable proximal-cuff-to-tip distance. We analyzed the association of preoperative characteristics such as age, sex, height, and weight with the nostril size and maximum allowable proximal-cuff-to-tip distance. The proportion of patients with appropriate locations of both the cuff and tip was evaluated. Sex and height were significant predictive factors of the nostril size and maximum allowable proximal-cuff-to-tip distance, respectively (p = 0.0001 and p = 0.0048). The difference in the safety margin was significantly decreased when the tube diameter was selected based on the nostril size rather than by sex (p<0.0001). The proportion of patients who had the appropriate cuff/tip location was significantly larger (75.2%) when the tube diameter was selected by sex compared to when it was selected by the nostril size (65%) (p<0.0001). It is more suitable to select the nasotracheal tube diameter based on sex rather than by nostril size to ensure the safe location of the tube's cuff and tip simultaneously.

Textile Masks and Surface Covers-A Spray Simulation Method and a "Universal Droplet Reduction Model" Against Respiratory Pandemics

The main form of COVID-19 transmission is via "oral-respiratory droplet contamination" (droplet: very small drop of liquid) produced when individuals talk, sneeze, or cough. In hospitals, health-care workers wear facemasks as a minimum medical "droplet precaution" to protect themselves. Due to the shortage of masks during the pandemic, priority is given to hospitals for their distribution. As a result, the availability/use of medical masks is discouraged for the public. However, for asymptomatic individuals, not wearing masks in public could easily cause the spread of COVID-19. The prevention of "environmental droplet contamination" (EnvDC) from coughing/sneezing/speech is fundamental to reducing transmission. As an immediate solution to promote "public droplet safety," we assessed household textiles to quantify their potential as effective environmental droplet barriers (EDBs). The synchronized implementation of a universal "community droplet reduction solution" is discussed as a model against COVID-19. Using a bacterial-suspension spray simulation model of droplet ejection (mimicking a sneeze), we quantified the extent by which widely available clothing fabrics reduce the dispersion of droplets onto surfaces within 1.8 m, the minimum distance recommended for COVID-19 "social distancing." All textiles reduced the number of droplets reaching surfaces, restricting their dispersion to <30 cm, when used as single layers. When used as double-layers, textiles were as effective as medical mask/surgical-cloth materials, reducing droplet dispersion to <10 cm, and the area of circumferential contamination to ~0.3%. The synchronized implementation of EDBs as a "community droplet reduction solution" (i.e., face covers/scarfs/masks and surface covers) will reduce COVID-19 EnvDC and thus the risk of transmitting/acquiring COVID-19.

Nasolaryngeal Distances in the Adult Population and an Evaluation of Commercially Available Nasotracheal Tubes

BACKGROUND

Preformed nasal endotracheal tubes (NETs) come with a predefined insertion depth due to their curved design. While size indication refers to internal diameter, there is a considerable variability in the corresponding lengths and proportions of same-sized tubes of different manufacturers which is probably based on the lack of data of nasolaryngeal distances (NLDs) in the adult population. Choosing the best-fitting NET is therefore difficult and carries the risk of endobronchial intubation or, on the contrary, cuff inflation at the vocal cord level. The aim of this study was to develop a prediction model for NLD and a selection guide to choose the appropriate NET based on a radiographic description of NLD in comparison to the measurements of available NETs of several manufacturers.

METHODS

After institutional ethics board review, 388 computed tomography (CT) scan images of head, neck, and upper thorax in a heterogeneous adult cohort were included. Mean distances from the nares to the lower border of the thyroid cartilage were measured. NETs from different manufacturers were measured and compared to the NLD derived from the radiographic analysis. The patients' sex, body height, and weight were considered as possible covariates in quantile regression models for predicting the NLD.

RESULTS

Data from 200 patients were analyzed. NLD was associated with sex, body height, and weight. A simple quantile regression model using the body height as the only covariate sufficed to achieve accurate predictions of NLD. Validation on independent test data showed that 92.8% of the NLD predictions were closer than ±20 mm to the observed NLD values. Measurements of equal-sized NETs varied considerably in outer diameter, proportion, the nasopharyngeal part, and guide marks. Length differences of the bend-to-cuff distance, containing the anatomically NLD, ranged between 218 and 270 mm at same sizes.

CONCLUSIONS

A reliable prediction of NLD can be obtained simply by body height, using the formula (Equation is included in full-text article.). As manufacturers' tube lengths vary substantially, additional information about the bend-to-cuff distance as corresponding tube section would allow for more accurate tube selection.

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.

Shallow nasal RAE tube depth after head and neck surgery: association with preoperative and intraoperative factors

PURPOSE

To evaluate risk factors associated with improper postoperative nasal Ring-Adair-Elwyn (RAE) tube depth.

METHODS

We retrospectively enrolled 133 adult patients who were admitted to the intensive care unit (ICU) with the nasal RAE tube after head and neck surgery. Postoperative chest radiography was performed to confirm nasal RAE tube depth immediately after the patient was admitted to the ICU. Proper tube depth was defined as the tube tip between 2 and 7 cm above the carina. The patients were divided into the proper-depth group (78 patients) and the improper-depth group (55 patients). Patients' characteristics were collected. The risk factors for improper postoperative tube depth were assessed using logistic regression analysis.

MAIN RESULTS

All patients who showed improper tube depth had a shallow tube depth (the tube tip > 7 cm above the carina). Multivariable analysis revealed that tall stature [odds ratio (OR) 1.16; 95% confidence interval (CI) 1.08-1.25; P < 0.001], prolonged anesthesia duration (OR 1.16; 95% CI 1.02-1.32; P = 0.026), and right-sided surgical field as compared to the left (OR 0.36; 95% CI 0.14-0.93; P = 0.034) or median field (OR 0.25; 95% CI 0.07-0.85; P = 0.027) were risk factors associated with postoperative shallow tube depth.

CONCLUSIONS

Tall stature, prolonged anesthesia duration, and right-sided surgical field were independent risk factors for postoperative shallow nasal RAE tube depth.

Insertion depth of nasotracheal tubes sized to fit the nostril: an observational study

Objective

Nasotracheal (NT) intubation is commonly applied during head and neck surgery. However, improper tube size and depth may cause complications. In the current study, we investigated whether NT tubes are being appropriately used in terms of size and depth in adult patients.

Methods

Nares were sized in 40 patients using standard nasopharyngeal airways (6.0–8.0) before elective surgery under general anesthesia. The largest sized airway that passed easily into the nasopharynx without resistance was considered as a proper size. Using a fiberoptic scope, the distances from the nares to the vocal cords and the nares to the carina were measured. Rates of proper NT tube positioning were calculated with regard to the cuff and distal tip.

Results

The most frequent sizes of properly fitted NT tubes were 6.5 and 6.0 in male and female patients, respectively. Positioning of the cuff and distal tip was only appropriate when using a properly sized tube in 26% and 47% of male and female patients, respectively.

Conclusion

Care should be taken to determine the insertion depth after placing an NT tube that has been sized to fit the nostril. Moreover, NT tubes of the same diameter may be required in various lengths.

Trial registration: Registered at ClinicalTrial.gov; https://clinicaltrials.gov/ct2/show/NCT02876913; Registration number NCT02876913

Estimation of optimal nasotracheal tube depth in adult patients

Background

The aim of this study was to estimate the optimal depth of nasotracheal tube placement.

Methods

We enrolled 110 patients scheduled to undergo oral and maxillofacial surgery, requiring nasotracheal intubation. After intubation, the depth of tube insertion was measured. The neck circumference and distances from nares to tragus, tragus to angle of the mandible, and angle of the mandible to sternal notch were measured. To estimate optimal tube depth, correlation and regression analyses were performed using clinical and anthropometric parameters.

Results

The mean tube depth was 28.9 ± 1.3 cm in men (n = 62), and 26.6 ± 1.5 cm in women (n = 48). Tube depth significantly correlated with height (r = 0.735, P < 0.001). Distances from nares to tragus, tragus to angle of the mandible, and angle of the mandible to sternal notch correlated with depth of the endotracheal tube (r = 0.363, r = 0.362, and r = 0.546, P < 0.05). The tube depth also correlated with the sum of these distances (r = 0.646, P < 0.001). We devised the following formula for estimating tube depth: 19.856 + 0.267 × sum of the three distances (R² = 0.432, P < 0.001).

Conclusion

The optimal tube depth for nasotracheally intubated adult patients correlated with height and sum of the distances from nares to tragus, tragus to angle of the mandible, and angle of the mandible to sternal notch. The proposed equation would be a useful guide to determine optimal nasotracheal tube placement.

Optimal length of the pre-inserted tracheal tube for excellent view in nasal fiberoptic intubation

PURPOSE

Inexperienced physicians frequently have difficulty performing nasal fiberoptic intubation. A pre-inserted tracheal tube of the appropriate length allows an excellent view of the laryngeal opening. The purpose of this study was to determine the ideal length of a pre-inserted tracheal tube for nasal fiberoptic intubation and to investigate if it could be predicted from easily measureable patient parameters.

METHODS

This was an observational study in which data on adult patients (n = 150) requiring nasal intubation were collected and analyzed by stepwise regression. During the pre-anesthesia examination, a right-angled gauge was used to measure the distance from the mid-point of the lateral border of the nares to the tragus of the ear (NT distance) and to the mandibular angle (NM distance). The distance from the tragus to the mandibular angle (TM distance) was also measured. The age, sex, height, and weight of each patient were recorded. After induction of anesthesia, the minimum and maximum lengths of the pre-inserted tracheal tube that provided an excellent view of laryngeal opening during nasal fiberoptic intubation were measured. The optimal length was calculated, and an equation was derived through stepwise regression analysis.

RESULTS

The optimal length for each patient could be reliably predicted using the equation (distances in cm, weight in kg): optimal length (cm) = 1.952 + 0.051 × height (cm) + 0.354 × NM distance (cm) - 0.011 × weight (kg) (r (2) = 0.460, P < 0.001).

CONCLUSION

The optimal length of pre-inserted tracheal tube for nasal fiberoptic intubation can be predicted using a newly developed formula with three patient parameters, namely, height, the NM distance, and weight. Application of this equation in the clinical setting should facilitate nasal fiberoptic intubation.

Clinical evaluation of nares-vocal cord distance and its correlation with various external body parameters

Background and Aims:

The optimal visualisation of vocal cords during fibreoptic intubation may be utilised for the nares-vocal cord distance (NVD) estimation. The present study was conducted to measure NVD and to correlate with various external body parameters.

Methods:

This study was conducted on 50 males and 50 females. We measured NVD and analysed its relationship with height, nares to tragus of ear distance (NED), nares to angle of mandible distance (NMD), sternal length (SL), thyro-mental distance (TMD), sterno-mental distance (SMD) and arm span (AS).

Results:

The mean NVD of the males was 18.5 ± 1.5 cm, and that of the females was 15.9 ± 1.1 cm. The relationship between the NVD and body height (males P = 0.001, r = 0.463, females P = 0.000, r = 0.555), SL (males P = 0.000, r = 0.463, females P < 0.000, r = 0.801) or AS (males P = 0.000, r = 0.561, females P = 0.000, r = 0.499) showed a significant correlation but NED, NMD, TMD, SMD did not. After combining male and female groups, (n = 100), the correlation of NVD with external body parameters is as follows SL (r = 0.887), height (r = 0.791), AS (r = 0.769), weight (r = 0.531), SMD (r = 0.466), NED (r = 0.459), NMD (r = 0.391), TMD (r = 0.379).

Conclusion:

The relationship of NVD to external body parameters had strong correlation in all parameters in the combined group; whereas when gender was taken into consideration NVD correlated significantly only with SL, height and AS.

Bedside prediction of airway length by measuring upper incisor manubrio-sternal joint length

BACKGROUND

Malpositioning of endotracheal tube may lead to serious complications like endobronchial intubation or accidental extubation. Using anatomical measurements for prediction of airway length would be more practical in resource constrained settings.

MATERIALS AND METHODS

One hundred adult patients of American Society of Anesthesiologists (ASA) grade 1 or 2, without any evidence of difficult airway, were randomly allocated to two cohorts - a model cohort of 70 (50 males) and test cohort of 30 (20 males) subjects. Height, the straight length from the upper incisor to manubrio-sternal joint in fully extended head position (IncManustL), the length from upper incisor to the carina in neutral head position (IncCarinaL), and degree of neck extension were measured in all subjects. Relationship between the two lengths in the model cohort was explored by Pearson's coefficient (r). Predictions were made for subjects in the test cohort and actual and predicted values assessed for agreement using intra-class correlation coefficient (ICC).

RESULTS

Good agreement was found between IncManustL and IncCarinaL for both male (r = 0.69) and female (r = 0.54) subjects. Multiple regression analysis suggested height to be another significant predictor, unlike age, weight, and neck extension. The gender-specific regression equations were used to predict IncCarinaL for the test cohort. ICC for absolute agreement between the actual and predicted values was 0.723 (95% CI 0.495-0.858).

CONCLUSIONS

It is possible to predict airway length in adult Indian subjects by making two simple anatomical measurements, namely stature and incisor manubrio-sternal joint length.

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.

The transnasal esophagoscopy documentation dilemma

OBJECTIVE

To determine radiographically the anatomic length difference between the nasal and oral aerodigestive tracts and to clarify gaps in the literature regarding standardized landmark measurements and documentation techniques in transnasal esophagoscopy, as opposed to traditional transoral esophagoscopy.

STUDY DESIGN

This is a prospective radiographic cohort study.

METHODS

Digital computerized tomography measurement techniques were used to determine the difference in length between the nasal and oral aerodigestive tracts. Using sagittal plane images from consecutive patients, the mean nares-cricoid (NC) distance, upper incisor-cricoid (IC) distance, and their mean differences were determined. Male, female, and overall distances and differences were calculated. Standard deviations, 95% confidence intervals, and 90% prediction intervals were also calculated. Mean difference data were applied to reported standard oral esophagoscopy landmark measurements to convert to standard landmark measurements from the nares.

RESULTS

Overall mean NC and IC distances were 175.4 mm and 147.5 mm, respectively. For males, these mean distances were 185.5 mm and 155.0 mm, respectively. For females, these mean distances were 165.3 mm and 140.0 mm, respectively. Overall mean NC to IC difference was 27.9 mm. The mean NC to IC difference for males and females was 30.5 mm and 25.2 mm, respectively.

CONCLUSIONS

Historically, landmark and report measurements in esophagoscopy have been measured and standardized from the upper incisor. This study demonstrates and clarifies the inherent anatomic length difference of the nasal and oral aerodigestive tracts and the resultant documentation dilemma produced by transnasal esophagoscopy techniques. These data provide easy conversion of esophagoscopy measurements reported from the incisors or nares, providing better communication between endoscopists of different disciplines and techniques.