Selection and placement of oral ventilation tubes based on tracheal morphometry

Size Matters: Endotracheal Tube Sizes and Glottic Stenosis Familiarity Among Intubating Physicians

Objective

Given the prevalence of post-intubation acute laryngeal injury (ALgI) and its association with glottic stenosis, greater attention has been placed on the mitigation of modifiable risk factors in patients requiring intubation, notably endotracheal tube (ETT) size. No widely accepted guidelines for adult ETT sizing exist. To better understand how factors driving ETT sizing may differ across specialties, we conducted a survey of faculty Anesthesiologists, Intensivists, and Emergency Medicine (EM) physicians.

Methods

An anonymous 14-question Qualtrics survey was distributed to relevant faculty employed at a single tertiary care institution. Participants completed questions pertaining to their training, ETT sizing preferences, factors considered in decision-making, and perceived knowledge regarding risk factors of glottic stenosis.

Results

A total of 103 complete responses were included, with a response rate of 55.1%. Standard ETT size was reported by 94 (91.3%) respondents to be 7.5 mm or larger in adult males and by 92 (89.3%) respondents to be 7.0 mm or larger in adult females. All respondents preferred a significantly larger ETT size for males compared to females (all p < 0.001). "Need for bronchoscopy" was the most cited factor precluding both males and females from being intubated with a smaller ETT across all specialties. When queried on posterior glottic stenosis, 64 (62.1%) respondents erroneously identified cuff pressure as a risk factor.

Conclusions

Understanding ETT sizing among intubating physicians is critical to reducing intubation-related ALgI. Future laryngologist-led interventions may be directed toward the adoption of a predominately height-based model for ETT sizing and education on glottic stenosis.

Level of Evidence

5.

Radiologic Findings of Cricoid Chondronecrosis after Intubation in the Setting of COVID-19

This case series examines seven patients diagnosed with cricoid chondronecrosis after intubation in the setting of COVID-19 and presents a novel "cricoid chondronecrosis computed tomography (CT) grading rubric" to standardize reporting of radiological findings. Application of this radiological grading rubric can improve communication among clinicians and radiologists and aid in prognosis determination of patients with cricoid chondronecrosis. Laryngoscope, 135:251-256, 2025.

Acute Laryngeal Injury in Patients Undergoing Airway Screening at a Long-Term Acute Care Hospital

BACKGROUND/OBJECTIVES

Acute laryngeal injury (ALgI) is an identified complication of prolonged intubation. Its evolution into mature stenosis and factors affecting decannulation are unclear. This retrospective review aims to characterize the incidence and characteristics of ALgI development and decannulation.

METHODS

Retrospective study of post-intubated patients with a tracheostomy seen for screening evaluation at a single long-term acute care hospital (LTACH) from 2019 to 2022.

RESULTS

Patients were followed for an average of 115 days after extubation. Forty-nine of 119 adult patients had ALgI. Those with ALgI were more likely female (61% vs. 35.7%, p = 0.006) with higher body mass index (BMI; 32.9 vs. 28.1, p = 0.03) and lower height (166 vs. 171.1 cm, p = 0.01). Decannulation rates in patients with ALgI were 69.4% compared to 84.3% in patients without ALgI (p = 0.053). Patients with ALgI were scoped more quickly post-extubation (28.8 vs. 36.6 days, p = 0.04), but time to decannulation did not differ (66.6 vs. 81.2 days, p = 0.74). Lower CCI (4.03 vs 6.93) and lack of tobacco use (41.2% vs 73.3%) were associated with successful decannulation (p = 0.038, p = 0.0008). Patients with ALgI treated conservatively (observation or medical management) were decannulated up to 71 days post-extubation. Further decannulations only occurred with surgical intervention.

CONCLUSIONS

Female gender, higher BMI, and shorter height are associated with ALgI among patients undergoing a LTACH screening evaluation. CCI and tobacco have a negative association with decannulation success. Among the ALgI cohort, no patient treated conservatively was decannulated after 71 days.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:4642-4648, 2024.

Micro-CT Imaging of Tracheal Development in Down Syndrome and Non-Down Syndrome Fetuses

OBJECTIVES

Down syndrome (DS) is associated with airway abnormalities including a narrowed trachea. It is uncertain whether this narrowed trachea in DS is a consequence of deviant fetal development or an acquired disorder following endotracheal intubation after birth. This study aimed to compare the tracheal morphology in DS and non-DS fetuses using microfocus computed tomography (micro-CT).

METHODS

Twenty fetal samples were obtained from the Dutch Fetal Biobank and divided into groups based on gestational age. Micro-CT images were processed to analyze tracheal length, volume, and cross-sectional area (CSA).

RESULTS

Mean tracheal length and tracheal volume were similar in DS and non-DS fetuses for all gestational age groups. Mean, minimum, and maximal tracheal CSA were statistically significantly increased in the single DS fetus in the group of 21-24 weeks of gestation, but not in other gestational age groups. In 90% of all studied fetuses, the minimum tracheal CSA was located in the middle third of the trachea.

CONCLUSION

Tracheal development in DS fetuses was similar to non-DS fetuses between 13 and 21 weeks of gestation. This suggests that the narrowed tracheal diameter in DS children may occur later in fetal development or results from postnatal intubation trauma. The narrowest part of the trachea is in majority of DS and non-DS fetuses the middle third.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:4389-4395, 2024.

Measurement of the lengths of different sections of the upper airway and their predictive factors

BACKGROUND

No studies have been conducted to define the lengths of the upper airway's different segments in normal healthy adults.

AIMS/OBJECTIVES

This study aimed to determine the length of the subglottis and extrathoracic trachea and the factors affecting it.

MATERIAL AND METHODS

This was an observational retrospective review study. Included 102 adult patients who underwent CT scan during the quiet inspiration phase of the upper airway.

RESULTS

The results revealed significant positive linear relationships between height and both anterior and posterior subglottic measurements (p < 0.001). Additionally, a statistically significant, moderately strong negative correlation between age and extrathoracic tracheal measurements (p > 0.001) was observed. Men exhibited longer anterior (p < 0.001) and posterior (p > 0.001) subglottic measurements. In both sexes, the average length of the anterior subglottis was 14.16 (standard deviation [SD]: 2.72) mm, posterior subglottis was 14.51 (SD: 2.85) mm and extrathoracic trachea was 66.37 (SD: 13.71) mm.

CONCLUSION AND SIGNIFICANCE

We concluded that a normal healthy adult's anterior subglottis length is 6.3-19.3 mm (mean: 14.16 [SD: 2.72] mm), posterior subglottis length is 6.1-20.0 mm (mean: 14.51 [SD: 2.85] mm) and extrathoracic trachea length is 25.2-98.5 mm (mean: 66.37 [SD: 13.71] mm). Age, height and sex affected the upper airway length.

Evolving Endotracheal Tube Preferences and Practices: Intensivist Knowledge Gaps and Sex Disparities

OBJECTIVES

The complex management of intubation-related laryngeal injury makes prevention vital. The purpose of this study is to assess endotracheal tube (ETT) practices and preferences among intensivists at our institution.

METHODS

Chart review of intubated patients and intensivist survey were simultaneously performed in January 2016 and August 2022. A height-to-ETT size ratio (H:ETT) was calculated for each patient in the 2022 cohort. Intubated patients were followed until tracheostomy, extubation, or death occurred. Surveys assessed intensivist preferences for ETT size and management of intubated patients.

RESULTS

300 ICU patients were included. The mean ETT size for males decreased from 7.73 ± 0.30 in 2016 to 7.57 ± 0.25 in 2022 (p < 0.001). The average H:ETT of men was higher than females (p = 0.004), indicating that females in this population were intubated with larger ETTs relative to their height compared to males. Whereas the majority (66.7%) of intensivists endorse 7.0 ETTs as the standard for women, the majority (70%) of women at our institution are intubated with a 7.5 ETT or larger. Of intubated patients in the ICU, 23 (19.5%) were intubated for 11 days or longer.

CONCLUSIONS

Compared to men, women are intubated with larger-than-preferred ETTs relative to height. Additionally, patients in our study were intubated for longer than preferred based on intensivist surveys, putting this population at higher risk for acute laryngeal injury (AlgI)-related laryngotracheal stenosis (LTS). Further studies should seek to identify similar trends and barriers to reducing ALgI-related LTS.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:3080-3086, 2023.

Clinicodemographic Predictors of Tracheotomy Tube Size and Decannulation: A Multiinstitutional Retrospective Cohort Study on Tracheotomy

OBJECTIVE

We aimed to discern clinico-demographic predictors of large (≥8) tracheostomy tube size placement, and, secondarily, to assess the effect of large tracheostomy tube size and other parameters on odds of decannulation before hospital discharge.

SUMMARY OF BACKGROUND DATA

Factors determining choice of tracheostomy tube size are not well-characterized in the current literature, despite evidence linking large tracheostomy tube size with posttracheotomy tracheal stenosis. The effect of tracheostomy tube size on timing of decannulation is also unknown, an important consideration given reported associations between endotracheal tube size and probability of failed extubation.

METHODS

We collected information pertaining to patients who underwent tracheotomy at 1 of 10 U.S. health care institutions between 2010 and 2019. Tracheostomy tube size was dichotomized (≥8 and <8). Multivariable logistic regression models were fit to identify predictors of (1) large tracheostomy tube size, and (2) decannulation before hospital discharge.

RESULTS

The study included 5307 patients, including 2797 (52.7%) in the large tracheostomy cohort. Patient height (odds ratio [OR] = 1.060 per inch; 95% confidence interval [CI] 1.041-1.070) and obesity (1.37; 95% CI 1.1891.579) were associated with greater odds of large tracheostomy tube; otolaryngology performing the tracheotomy was associated with significantly lower odds of large tracheostomy tube (OR = 0.155; 95% CI 0.131-0.184). Large tracheostomy tube size (OR = 1.036; 95% CI 0.885-1.213) did not affect odds of decannulation.

CONCLUSIONS

Obesity was linked with increased likelihood of large tracheostomy tube size, independent of patient height. Probability of decannulation before hospital discharge is influenced by multiple patient-centric factors, but not by size of tracheostomy tube.

Association of Educational Intervention With Knowledge of Airway Injury After Endotracheal Intubation and Tube Size Selection

In this nonrandomized controlled trial, an educational intervention for emergency medicine residents was developed to increase knowledge of airway injury following prolonged intubation and reduce the proportion of large-for-height endotracheal tubes placed in the emergency department.

The Effects of Endotracheal Tube Size During Bronchoscopy in Simulated Models of Intubated Patients

OBJECTIVE

The aim is to use a simulation lung model to assess the possibility of performing bronchoscopy through endotracheal tubes (ETT) less than 8.0-mm while appropriately ventilating patients with normal and ARDS lungs in the setting of SARS-CoV-2.

METHODS

Five SHERIDAN® ETTs were used to ventilate SimMan® 3G under respiratory compliance levels representing normal and severe ARDS lungs. Baseline measurements of peak pressure, plateau pressure, and auto-positive end expiratory pressure (auto-PEEP) were recorded at four different inspiratory times (Ti). Three different-sized disposable bronchoscopes were inserted, and all measurements were repeated.

RESULTS

Normal lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures <30 cm H₂ O, and increasing Ti to minimize peak pressure resulted in low auto-PEEP. Regular bronchoscopes in 7.0-mm ETTs had similar results. Large bronchoscopes in 7.5-mm ETTs generated plateau pressures ranging from 28 to 35 cm H₂ O with modest auto-PEEP. Severe ARDS lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures of 46 and an auto-PEEP of 5 cm H₂ O. Regular bronchoscopes in 7.0-mm ETTs generated similar results. Large bronchoscopes in 8.0-mm ETTs displayed plateau pressures of 44 and an auto-PEEP of 2 cm H₂ O.

CONCLUSION

To mitigate risk of laryngeal injury, larger ETTs during bronchoscopy should be avoided. Our data show bronchoscopy with any ETT causes auto-PEEP and high plateau pressures, especially in lungs with poor compliance; however, ETT less than 7.5 mm can be used when considering several factors. Our data also suggest similar studies in patients with varying degrees of ARDS would be informative.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:147-153, 2023.

Endotracheal Tube Size in Critically Ill Patients

Importance

Many patients who survive critical illness are left with laryngeal functional impairment from endotracheal intubation that permanently limits their recovery and quality of life. Although the risk for laryngeal injury increases with larger endotracheal tube sizes, there are no data delineating the association of smaller endotracheal tube sizes with survival or acute recovery from critical illness.

Objective

To determine if smaller endotracheal tubes are noninferior to larger endotracheal tubes with respect to critical illness outcomes.

Design, Setting, and Participants

This propensity score-matched retrospective cohort study included all adult patients who underwent endotracheal intubation in the emergency department or intensive care unit and received mechanical ventilation for at least 12 hours from June 2020 to November 2020 at a single tertiary referral academic medical center.

Exposures

Endotracheal intubation.

Main Outcomes and Measures

Propensity score-matched analyses were performed with respect to the primary end point of 30-day all-cause in-hospital survival as well as the secondary end points of duration of invasive mechanical ventilation, length of hospital stay, mean peak inspiratory pressure, 30-day readmission, need for reintubation, and need for tracheostomy or gastrostomy tube placement.

Results

Overall, 523 participants (64%) were men and 291 (36%) were women. Of these, 814 patients were categorized into 3 endotracheal tube groups: small for height (n = 182), appropriate for height (n = 408), and large for height (n = 224). There was not a significant difference in 30-day all-cause in-hospital survival between groups ([HR, 1.1; 95% CI, 0.7-1.7] for small vs appropriate; [HR, 1.1; 95% CI, 0.7-1.6] for large vs appropriate). Patients with small-for-height endotracheal tubes had longer intubation durations (mean difference, 32.5 hrs [95% CI, 6.4-58.6 hrs]) compared with patients with appropriate-for-height tubes.

Conclusions and Relevance

Despite differences in intubation duration, the results of this cohort study suggest that smaller endotracheal tube sizes are not associated with impaired survival or recovery from critical illness. They support future prospective exploration of the association of smaller endotracheal tube sizes with recovery from critical illness.

Awake nasotracheal intubation under bronchoscopic guidance and anesthetic management in a patient undergoing excision of an endotracheal mass: A case report

RATIONALE

The main challenge facing anesthesiologists during endotracheal mass resection is securing effective airway management during surgery. It is important to select an airway intubation and airway maintenance method according to the patient's condition and the characteristics of the mass.

PATIENT CONCERNS

A 74-year-old woman with aggravated dyspnea for 1 year was scheduled to undergo endotracheal mass excision under general anesthesia.

DIAGNOSIS

The mass was 4 × 3 × 3 cm ovoid-shaped, and located 4 cm above the carina, occupying 41% of the tracheal lumen in a preoperative chest computed tomography and bronchoscopy.

INTERVENTIONS

After preparing extracorporeal membrane oxygenation in case of the inability to ventilate and intubate, we attempted awake bronchoscopy-guided nasotracheal intubation using a reinforced endotracheal tube with an inner diameter of 5.5 mm and outer diameter of 7.8 mm after a translaryngeal block. The tube was passed around the mass without resistance and placed right above the carina. With the tube pulled back above the mass, another tube was introduced from the opened trachea below the mass to the right main bronchus. Following the resection of the tracheal portion containing the mass, the posterior wall of the remaining trachea was reconstructed. The tube placed in the right main bronchus was removed and the tube in the upper trachea was introduced right above the carina. The patient's head was kept flexed once the anastomosis of the trachea was completed, and the surgery ended uneventfully.

OUTCOMES

The mass was confirmed as schwannoma by histopathological finding. The patient was discharged from the hospital on the 6th postoperative day without complication.

LESSONS

Awake bronchoscopy-guided intubation is a safe airway management method in patients with an endotracheal mass. Close cooperation between anesthesiologist and surgeon, and preparation for airway management before surgery is essential. It is necessary to establish alternative plans that can be implemented in the case that intubation and ventilation are not possible.

Compatibility of left-sided double-lumen endobronchial tubes with tracheal and bronchial dimensions: a retrospective comparative study

BACKGROUND

Double-lumen endobronchial tubes (DLT) continue to be the most widely used method for obtaining lung isolation during anesthesia. We compared recommendations for DLT size selection with radiologically assessed lower airway dimensions gathered from a large patient population.

METHODS

For this retrospective comparative study, we assessed computed tomography (CT) scans of 150 adults with no known airway pathologies. Using these scans, we measured the diameter and length of the trachea and the diameter of the mainstem bronchi. These airway dimensions were then compared to the dimensions of left-sided DLTs of three different manufacturers. Size selection was based on one standard textbook's recommendations.

RESULTS

We found the recommended DLT sizes were occasionally too small but more often too large, particularly in the endobronchial airway. With the DLT Vivasight-DL®, mismatching occurred in 28.7% (43/150) of the patients at the distal mainstem bronchus and 8% (12/150) at the tracheal level. This mismatching happened most often in females (left distal mainstem bronchus 34/68, 50%; trachea 9/68, 13.2%). Conversely, the DLT was more often too small for male patients in both the left main bronchus (SHER-I-BRONCH®: 8/82, 9.8%) and the trachea (SHER-I-BRONCH®: 2/82, 2.4%). The endobronchial tube portion was more often too long in females (Vivasight® DLT: 11/68, 16%) than males (9/82, 11%).

CONCLUSIONS

A considerable proportion of the recommended DLT sizes from all three manufacturers was incompatible with individual patient's lower airway dimensions.

Evaluation of sex-based differences in airway size and the physiological implications

Recent evidence suggests healthy females have significantly smaller central conducting airways than males when matched for either height or lung volume during analysis. This anatomical sex-based difference could impact the integrative response to exercise. Our review critically evaluates the literature on direct and indirect techniques to measure central conducting airway size and their limitations. We present multiple sources highlighting the difference between male and female central conducting airway size in both pediatric and adult populations. Following the discussion of measurement techniques and results, we discuss the functional implications of these differences in central conducting airway size, including work of breathing, oxygen cost of breathing, and how these impacts will continue into elderly populations. We then discuss a range of topics for the future direction of airway differences and the benefits they could provide to both healthy and diseased populations. Specially, these sex-differences in central conducting airway size could result in different aerosol deposition or how lung disease manifests. Finally, we detail emerging techniques that uniquely allow for high-resolution imaging to be paired with detailed physiological measures.

Does the Retromolar Area Provide Adequate Space for an Oral Endotracheal Tube Without Interfering With Intermaxillary Fixation?

PURPOSE

Traumatic maxillofacial injuries requiring intermaxillary fixation (IMF) traditionally necessitate airway management via tracheostomy or submental intubation. The aim of this study is to understand whether the retromolar space can accommodate passage of a reinforced endotracheal tube (ETT) without interfering with establishing IMF, a technique previously described as retromolar intubation.

METHODS

A retrospective cross-sectional study was created including previously treated facial trauma patients by our department as the study sample. From this group, 3D reconstructed scans were created and used to estimate that dimensions of the retromolar space. The averages of these dimensions were calculated and compared to the area occupied by different sized reinforced ETTs (6.0, 6.5, 7.0, 7.5, 8.0). A 1-sample t-test was used to compare the retromolar areas to each ETT size for all patients and by gender.

RESULTS

Forty-one patients, ages 19-69 years old, treated from July 2010 to November 2018 were included in this study. This included 24 males (21-69yo) and 17 females (19-60yo), with a total of 80 characteristics measured. The retromolar areas calculated were statistically bigger than the reinforced ETT sizes 6.0, 6.5, and 7.0 compared to the average retromolar space area, but not statistically significant for reinforced oral ETT sizes 7.5 and 8.0.

CONCLUSION

Our study results suggest the use of 6.0, 6.5 and 7.0 reinforced ETTs can be positioned in the retromolar space, allowing the surgeon to place a patient in IMF without occlusal interference. This technique could provide an alternative option to submental intubation or tracheostomy.

Incidence of Laryngotracheal Stenosis after Thermal Inhalation Airway Injury

Inhalation injury is independently associated with burn mortality, yet little information is available on the incidence, risk factors, or functional outcomes of thermal injury to the airway. In patients with thermal inhalation injury, we sought to define the incidence of laryngotracheal stenosis (LTS), delineate risk factors associated with LTS development, and assess long-term tracheostomy dependence as a proxy for laryngeal function. Retrospective cohort study of adult patients treated for thermal inhalation injury at a single institution burn critical care unit from 2012 to 2017. Eligible patients' records were assessed for LTS (laryngeal, subglottic, or tracheal stenosis). Patient characteristics, burn injury characteristics, and treatment-specific covariates were assessed. Descriptive statistics, Mann-Whitney U-tests, odds ratio, and chi-square tests compared LTS versus non-LTS groups. Of 129 patients with thermal inhalation injury during the study period, 8 (6.2%) developed LTS. When compared with the non-LTS group, patients with LTS had greater mean TBSA (mean 30.3, Interquartile Range 7-57.5 vs 10.5, Interquartile Range 0-15.12, P = .01), higher grade of inhalation injury (mean 2.63 vs 1.80, P = .05), longer duration of intubation (12.63 vs 5.44; P < .001), and greater inflammatory response (mean white blood cell count on presentation 25.8 vs 14.9, P = .02, mean hyperglycemia on presentation 176.4 vs 136.9, P = .01). LTS patients had a significantly higher rate of tracheostomy dependence at last follow-up (50 vs 1.7%, P < .001). Six percent of patients with thermal inhalation injury develop LTS. LTS was associated with more severe thermal airway injury, longer duration of intubation, and more severe initial host inflammation. Patients with inhalation injury and LTS are at high risk for tracheostomy dependence. In burn patients with thermal inhalation injury, laryngeal evaluation and directed therapy should be incorporated early into multispecialty pathways of care.

Current Practices in Endotracheal Tube Size Selection for Adults

OBJECTIVES/HYPOTHESIS

Intubation with inappropriately sized endotracheal tubes (ETT) can cause long-term tracheal and laryngeal injuries often requiring surgical intervention. Although tracheal size has been demonstrated to vary based on height and sex, it is unclear whether these guidelines are regularly implemented in patients undergoing endotracheal intubation. The objective of this study is to determine the rate of appropriate ETT size selection in patients undergoing intubation and assess provider decision making in ETT size selection.

STUDY DESIGN

Retrospective cohort study.

METHODS

The study population was all patients who underwent endotracheal intubation over a two-week period at a tertiary academic medical center. Data were collected on patient age, gender, height, BMI, comorbidities, ETT size, duration of intubation, bronchoscopies, and type of practitioner who performed the intubation. A height-based nomogram for ETT size selection was used to determine the recommended ETT size for each patient.

RESULTS

One hundred five patients met the inclusion criteria. 22% of patients were intubated with an inappropriately large tube, defined as 1.0 mm larger than the recommended size. Women were more likely to be intubated with an inappropriately large ETT (OR = 13.58, P = .001), as were patients with height less than 160 cm (OR = 141, P = .001). Other factors related to disease severity, anticipation for bronchoscopy, and BMI were not risk factors for the use of inappropriately large ETT.

CONCLUSIONS

Although there is compelling evidence that height is a strong predictor of tracheal morphology and appropriate ETT size, height-based guidelines have yet to be universally adopted for ETT size selection. Laryngoscope, 131:1967-1971, 2021.

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.

Predicting pediatric tracheal airway size from anthropomorphic measurements

OBJECTIVES

To determine the relationship between body mass index and tracheal airway size in children.

METHODS

Retrospective case series. CT or MRI images of the neck of 171 pediatric patients obtained from 2000 to 2010 at a tertiary pediatric hospital were analyzed. Age, gender, height, weight, BMI and CDC weight classification for each patient were compared with axial CT measurements (AP diameter and width) and calculated cross-sectional airway area. Linear regression models were performed to identify factors predictive of airway size.

RESULTS

Age ranged from 2 to 20 years. Weight was the most significant predictor of tracheal AP diameter (P = 0.029), with height also approaching statistical significance (P = 0.051). Tracheal width was best predicted by height (P = 0.09). Weight was the only statistically significant predictor of cross-sectional tracheal area (P = 0.002). Body mass index was not a statistically significant predictor of airway size in any dimension; however, there was an obvious trend towards decreasing tracheal width and cross-sectional area in patients with BMI of 25 or greater.

CONCLUSION

In pediatric patients, estimation of endotracheal or tracheostomy tube size should take into account height, weight and BMI in addition to the patient's age. Patients with elevated BMI may have smaller tracheal sizes in various dimensions than normal or low-weight patients.

Incidence and Outcomes of Acute Laryngeal Injury After Prolonged Mechanical Ventilation

OBJECTIVES

Upper airway injury is a recognized complication of prolonged endotracheal intubation, yet little attention has been paid to the consequences of laryngeal injury and functional impact. The purpose of our study was to prospectively define the incidence of acute laryngeal injury and investigate the impact of injury on breathing and voice outcomes.

DESIGN

Prospective cohort study.

SETTING

Tertiary referral critical care center.

PATIENTS

Consecutive adult patients intubated greater than 12 hours in the medical ICU from August 2017 to May 2018 who underwent laryngoscopy within 36 hours of extubation.

INTERVENTIONS

Laryngoscopy following endotracheal intubation.

MEASUREMENTS AND MAIN RESULTS

One hundred consecutive patients (62% male; median age, 58.5 yr) underwent endoscopic examination after extubation. Acute laryngeal injury (i.e., mucosal ulceration or granulation tissue in the larynx) was present in 57 patients (57%). Patients with laryngeal injury had significantly worse patient-reported breathing (Clinical Chronic Obstructive Pulmonary Disease Questionnaire: median, 1.05; interquartile range, 0.48-2.10) and vocal symptoms (Voice Handicap Index-10: median, 2; interquartile range, 0-6) compared with patients without injury (Clinical Chronic Obstructive Pulmonary Disease Questionnaire: median, 0.20; interquartile range, 0-0.80; p < 0.001; and Voice Handicap Index-10: median, 0; interquartile range, 0-1; p = 0.005). Multivariable logistic regression independently associated diabetes, body habitus, and endotracheal tube size greater than 7.0 with the development of laryngeal injury.

CONCLUSIONS

Acute laryngeal injury occurs in more than half of patients who receive mechanical ventilation and is associated with significantly worse breathing and voicing 10 weeks after extubation. An endotracheal tube greater than size 7.0, diabetes, and larger body habitus may predispose to injury. Our results suggest that acute laryngeal injury impacts functional recovery from critical illness.

Tracheal tube size in adults undergoing elective surgery - a narrative review

Tracheal tubes are routinely used in adults undergoing elective surgery. The size of the tracheal tube, defined by its internal diameter, is often generically selected according to sex, with 7-7.5 mm and 8-8.5 mm tubes recommended in women and men, respectively. Tracheal diameter in adults is highly variable, being narrowest at the subglottis, and is affected by height and sex. The outer diameter of routinely used tracheal tubes may exceed these dimensions, traumatise the airway and increase the risk of postoperative sore throat and hoarseness. These complications disproportionately affect women and may be mitigated by using smaller tracheal tubes (6-6.5 mm). Patient safety concerns about using small tracheal tubes are based on critical care populations undergoing prolonged periods of tracheal intubation and not patients undergoing elective surgery. The internal diameter of the tube corresponds to its clinical utility. Tracheal tubes as small as 6.0 mm will accommodate routinely used intubation aids, suction devices and slim-line fibreoptic bronchoscopes. Positive pressure ventilation may be performed without increasing the risk of ventilator-induced lung injury or air trapping, even when high minute volumes are required. There is also no demonstrable increased risk of aspiration or cuff pressure damage when using smaller tracheal tubes. Small tracheal tubes may not be safe in all patients, such as those with high secretion loads and airflow limitation. A balanced view of risks and benefits should be taken appropriate to the clinical context, to select the smallest tracheal tube that permits safe peri-operative management.

Proposing an Endotracheal Tube Selection Tool Based on Multivariate Analysis of Airway Imaging

OBJECTIVES

We aimed to comprehensively investigate different upper airway segments in adults, determine the predictors of the size of each segment, and identify an appropriate endotracheal tube (ETT) size chart.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary care center.

MATERIALS AND METHODS

The data for patients aged >18 years who underwent neck computed tomography were screened. Patients with existing tumors, trauma, or any pathology that can alter the normal airway anatomy and those with intubation, tracheostomy, or nasogastric tubes were excluded. Computed tomography software was used to measure the anteroposterior diameter (APD), transverse diameter (TD), and cross-sectional area (CSA) at the glottic, proximal subglottic, distal subglottic, and tracheal levels. Multiple regression analysis was used to identify the predictors of the airway size.

RESULTS

One hundred patients were reviewed. The TD was consistently smaller than or equal to the APD at each level in all but 3 patients. The mean CSA and TD (170 mm² and 11.3 mm, respectively) of the glottis indicated that the glottis was most often the narrowest level, followed by the proximal subglottis where the mean CSA and TD were 192.1 mm² and 12.7 mm, respectively. Moreover, the mean APD was the smallest at the level of the trachea (20.1 mm). Multiple regression analysis confirmed that height and sex were the predominant predictors of measurements for the 4 airway segments. In addition, age was associated with the TD and CSA of the distal subglottic and tracheal segments, respectively.

CONCLUSION

One-third of our participants exhibited a proximal subglottic diameter that was equal to or smaller than the glottic diameter. Our findings also suggested that the height and sex of the patients are important variables for the selection of an appropriate ETT size.

Comparison Between Mathematical and Software Calculation Methods for the Measurement of the Cross-sectional Area in Upper Airway Imaging

Objectives This study aimed to compare the results of a software calculation method (SCM) and the mathematical calculation method (MCM) in measuring the cross-sectional area (CSA) at four different upper airway segments. Methods The data from the retrospective chart reviews of patients older than 18 years who had undergone computed tomography (CT) of the neck at our tertiary care center between September 2014 and September 2018 were reviewed. Data of patients who were intubated, tracheostomized, had nasogastric tubes, tumors, craniofacial anomalies, trauma, or any pathology that may affect the normal airway anatomy were excluded. We measured the anteroposterior (APD) and transverse diameter (TD) utilizing the CT software. CSA was calculated using both the mathematical formula (MCM) and software (SCM) at the glottis, proximal subglottis, distal subglottis, and tracheal levels. A paired sample t-test was used to determine the significant difference between SCM and MCM at each level. Results The data of 100 patients (59% female) were reviewed. There was a significant difference between the SCM and MCM at all four levels. The mean differences between the SCM and MCM were -33.63 mm², -24.20 mm², 6.04 mm² (p < 0.001) at the glottis, proximal subglottis, and trachea, respectively. The mean difference at the distal subglottis was -4.08 mm² (p = 0.01). Conclusion Our study found a significant difference between the SCM and MCM in measuring the CSA of the four airway segments. Theoretically, the SCM is more accurate and precise than MCM in measuring CSA; however, we could not prove the superiority of either method.

Pediatric tracheal dimensions on computed tomography and its correlation with tracheostomy tube sizes

OBJECTIVE

Age-based formulas for selecting the appropriate size of tracheostomy tubes in children are based on data on tracheal dimensions. This study aims to measure the tracheal dimensions of Indian children by computerized tomography (CT) and to compare this with the dimensions of age-appropriate tracheostomy tubes.

METHODS

CT scans of children aged less than 16 years that were taken for indications other than respiratory distress were included. Tracheal diameters at the tracheostomy point and tracheal length from the tracheostomy point to the carina were calculated from the scans. These dimensions were correlated with age, weight, and height. The measurement on the CT scan was used to predict the appropriate size of tracheostomy tube, which was compared with the tracheostomy tube sizes.

RESULTS

Two hundred and fourteen CT scans of children aged below 16 years were included in the study. On multiple logistic regression analysis, tracheal diameter correlated well with age and weight (P = 0.04 and 0.001, respectively), whereas tracheal length correlated well with age and height of the child (P = 0.03 and 0 < 0.001, respectively). On comparison with dimensions of the tracheostomy tube, tracheal diameter correlated well, and the length was found to be longer than needed to prevent endobronchial intubation. The regression value was used to predict the size of an ideal tracheostomy tube.

CONCLUSION

Tracheal diameter of Indian children correlates well with the outer diameter of age-appropriate tracheostomy tubes, but the length of these tubes is longer than the ideal length. This would necessitate a change in the design of these tubes.

LEVEL OF EVIDENCE

2b Laryngoscope, 130:1316-1321, 2020.

Height is an independent risk factor for postintubation laryngeal injury

OBJECTIVES/HYPOTHESIS

Intubation is an essential component of intensive care, yet it does have potential complications. Posterior glottic stenosis (PGS) is among the most severe sequela. Risk factors are poorly understood. One hypothesis is that large endotracheal tubes (ETTs) in smaller airways may increase risk. Because tracheal diameter is proportional to height, we designed a case-control study to evaluate the association between intensive care unit (ICU)-patient height (proxy for tracheal diameter) and their risk of postintubation PGS.

STUDY DESIGN

Retrospective case-control study METHODS: Among patients who underwent intubation in an ICU at a single tertiary care medical center between 2001 and 2015, a convenience sample of all patients with confirmed PGS (cases) were enrolled. Cases were matched 1:1 by age, sex, and race with intubated non-PGS controls chosen from the same population of ventilated patients. Data on height, weight, comorbidities, size of ETT, and duration of intubation were abstracted from the medical record. Multivariate models were used to test the association between patient height and risk of PGS development.

RESULTS

In all, 106 PGS cases (mean age 48.9 years, 50.7% female, 79.2% Caucasian) were identified; 77 met inclusion criteria. Compared to matched controls, cases were significantly shorter (mean 166 cm vs. 173 cm, P = .001). Height and PGS showed an inverse relationship in multivariate models. Specifically, odds of PGS decreased 9% (95% confidence interval: 0.01%-16%) for each centimeter increase in height.

CONCLUSIONS

Shorter height is independently associated with increased odds of having PGS. Further work should consider whether height should be incorporated into ETT selection algorithms.

LEVEL OF EVIDENCE

3b Laryngoscope, 128:2811-2814, 2018.

The Tracheal Accordion and the Position of the Endotracheal Tube

The purpose of this review is to, first, determine the static factors that affect the length of the human trachea across different populations and, second, to investigate whether or not there are dynamic factors that cause the length of the human trachea to vary within the same individual. We also investigated whether these changes in tracheal length within the same individual are significant enough to increase the risk of endobronchial intubation or accidental extubation. A PubMed/MEDLINE and a Web of Science database English-language literature search was conducted in May 2016 with relevant keywords and MeSH terms when available. We found that gender, extremes of age, patient height, postsurgical changes and co-existing disease are static patient factors that affect the length of the human trachea. Dynamic clinical changes that occur under anaesthesia, including Trendelenburg position, head and neck flexion and extension, paralysis of the diaphragm and pneumoperitoneum, cause the trachea to act as an accordion, decreasing and increasing its length. The length of the human trachea in both awake and anaesthetised and paralysed patients is a critical consideration in preventing both endobronchial intubation and tracheal extubation. It is clear from the literature that tracheal length varies widely across populations and, additionally, with the dynamic clinical changes that occur under anaesthesia, the trachea acts as an accordion decreasing and increasing its length within the same individual. Knowledge of the magnitude of the change in tracheal dimensions in response to these factors is an important clinical consideration.

A Comparative Study of Tracheal Diameter in Caucasian and Chinese Patients

Ethnicity may be considered a factor when considering what size endotracheal tube to insert. In particular it has been suggested that Chinese patients have a smaller tracheal diameter, justifying the selection of smaller endotracheal tubes. We systematically evaluated transverse tracheal diameters in Chinese and Caucasian patients, utilising archived computer tomography images. A convenience sample of 100 Caucasian patients from Australia was compared with 100 Chinese patients from Hong Kong. Patients over 18 years of age who had undergone a computerised tomography scan of the neck and thorax, and also had accurate body height and weight recorded, were studied. The mean transverse diameter of the trachea measured at three levels was similar between the Chinese and Caucasian patients. At the narrowest measurement point, the immediate subcricoid transverse diameter, the unadjusted mean difference between male Chinese and Caucasian patients was small (1 mm, standard deviation 0.83 mm, P=0.01), and similarly small between female Chinese and Caucasian patients (1.5 mm, standard deviation 0.8 mm, P <0.01). Multivariate analysis demonstrated only a small influence related to ethnicity (12% relative contribution to the overall variance [R2] of the model), but substantial influence of height (40%) and sex (41%). Our findings do not support the practice of routinely selecting a smaller endotracheal tube size for Chinese patients on the basis that there is a difference related to the Chinese ethnic phenotype. Considerations regarding choice of endotracheal tube size should rather focus on patient sex and height.

Intrinsic positive end-expiratory pressure during ventilation through small endotracheal tubes during general anesthesia: incidence, mechanism, and predictive factors

STUDY OBJECTIVE

To assess the safety of mechanical ventilation and effectiveness of extrinsic positive end-expiratory pressure (PEEP) (PEEPe) in improving peripheral oxygen saturation (SpO2) during direct microlaryngeal laser surgery; to assess the incidence, amount, and nature (dynamic hyperinflation or airflow obstruction) of ensuing intrinsic PEEP (PEEPi); and to find a surrogate PEEPi indicator.

DESIGN

Quasiexperimental.

SETTING

S. Raffaele Hospital (Milano), November 2009 to December 2010.

PATIENTS

Fifty-two adults scheduled for direct microlaryngeal laser surgery. Exclusion criterion is pregnancy.

INTERVENTIONS

Twenty-one percent O2 mechanical ventilation through 4.5- to 5.5-mm internal diameter endotracheal tubes; in 29 patients, after measurement of PEEPi, an identical amount of PEEPe was added; and PEEPi.

MEASUREMENTS

SpO2, peak (Pawpeak) and plateau (Pawplateau) airway pressure, and end-expiratory carbon dioxide were measured every 5 minutes. Respiratory compliance (Crs) was computed. PEEPi was measured (end-expiratory occlusion method).

MAIN RESULTS

PEEPi ≥5 cm H2O occurred in 14 patients (27%) after intubation, in 16 (30%) at the beginning, and in 14 (27.3%) at the end of surgery. Thirty-one patients (59.4%) exhibited PEEPi ≥5 cm H2O on at least 1 time point. PEEPi at the beginning of surgery was positively correlated with Pawplateau, Crs, tidal volume, and body mass index. Body mass index was the only predictor for the occurrence of PEEPi ≥5 cm H2O. At the beginning of surgery, the Pawplateau receiver operating characteristic curve predicting PEEPi ≥5 cm H2O had area under the receiver operating characteristic curve of 0.85; best cutoff value of 15.5 cm H2O (sensitivity, 88.9%; specificity, 75%; correctly classified cases, 86.1%). When PEEPe was applied, in 23 cases (82.1%), total PEEP equaled PEEPe+ PEEPi; in 3 (10.7%), it was lower; and in 2 (7.1%), it was higher. Application of PEEPe increased SpO2 (P< .05) and Crs (P< .05).

CONCLUSIONS

During ventilation through small endotracheal tubes, PEEPi (mostly due to dynamic hyperinflation) is common. Hemodynamic complications, barotrauma, and O2 desaturation (reversible with PEEPe) are rare. Pawplateau provided by ventilators is useful in suspecting and monitoring the occurrence of PEEPi and allows detection of lung overdistension as PEEPe is applied.

Association of Oversized Tracheal Tubes and Cuff Overinsufflation With Postintubation Tracheal Ruptures

Objectives

Postintubation tracheal ruptures (PTR) are rare but cause severe complications. Our objective was to investigate the tracheal pattern of injury resulting from cuff inflation of the tracheal tube, to study the two main factors responsible for PTR (cuff overinsufflation and inapplicable tube sizes), and to explain the context, why small women are particularly susceptible to PTR.

Methods

Experimental study performed on 28 fresh human laryngotracheal specimens (16 males, 12 females) within 24 hours post autopsy. Artificial ventilation was simulated by using an underwater construction and a standard tracheal tube. Tube sizes were selected according to our previously published nomogram. Tracheal lesions were detected visually and tracheal diameters measured. The influence of body size, sex difference and appropriate tube size were investigated according to patient height.

Results

In all 28 cases, the typical tracheal lesion pattern was a longitudinal median rupture of the posterior trachea. Appropriate tube sizes according to body size caused PTR with significantly higher cuff pressure when compared with oversized tubes. An increased risk of PTR was found in shorter patients, when oversized tubes were used. Sex difference did not have any significant influence.

Conclusion

This experimental model provides information about tracheal patterns in PTR for the first time. The model confirms by experiment the observations of case series in PTR patients, and therefore emphasizes the importance of correct tube size selection according to patient height. This minimizes the risk of PTR, especially in shorter patients, who have an increased risk of PTR when oversized tubes are used.

Tracheal Size Variability Is Associated With Sex

Purpose:

Whereas selection of endotracheal tube (ETT) size in pediatric patients benefits from predictive nomograms, adult ETT sizing is relatively arbitrary. We sought to determine associations between cervical tracheal cross-sectional area (CTCSA) and clinical variables.

Methods:

One hundred thirty-two consecutive patients undergoing noncontrasted chest computed tomography (CT) at a single tertiary care institution from January 2010 to June 2011 were reviewed. Patients with improper CT technique, endotracheal intubation, and pulmonary/tracheal pathology were excluded. Tracheal luminal diameters in anteroposterior (D1) and transverse (D2) were measured 2 cm inferior to the cricoid and used to determine CTCSA = π*D1*D2*¼. The demographic variables of age, height, weight, and body mass index (BMI) were tested for association with CTCSA by Spearman correlation. Wilcoxon rank-sum test was used to compare CTCSA by race and sex. Multivariate linear regression was performed including all clinical variables.

Results:

There were 91 patients who met inclusion criteria. There was no correlation between age, weight, or BMI and CTCSA. There was a significant positive correlation between patient height and CTCSA ( P = .001, R = 0.35); however, this was confounded by sex. Female patients had significantly smaller CTCSA (mean = 241 mm2) compared to male patients (mean = 349 mm2, P < .001). Multivariate linear regression stratified by sex revealed that height is correlated with CTCSA only in males ( P = .028). Males also had more variability in CTCSA (SD 118.6) compared to females (SD 65.5).

Conclusion:

Our data suggest that selection of ETT size in male patients should include height as a predictive factor. For female patients, it may be appropriate to select a uniformly smaller diameter ETT size.