Assessment of the subglottic region by ultrasonography for estimation of appropriate size endotracheal tube: A clinical prospective study

A Scoping Review of Ultrasonographic Techniques in the Evaluation of the Pediatric Airway

Point-of-care ultrasound is making rapid advancements in pediatrics, and ultrasonographic assessment of the airway is being employed in many specialties such as the pediatric, cardiac, and neonatal intensive care units, emergency department, pulmonary clinic, and the perioperative setting. This scoping review provides a technical description of image acquisition and interpretation, accompanying ultrasound images of the hallmark airway applications in pediatrics, and supporting evidence when available. We describe and illustrate ultrasound-determined endotracheal tube (ETT) sizing, ETT placement and depth confirmation, vocal fold assessment, prediction of post-extubation stridor, difficult laryngoscopy prediction, and cricothyrotomy guidance. This review aims to provide the descriptions and images necessary to learn and apply these skills at the point of care in the pediatric patient.

Clinical and ultrasonographic assessment of airway indices among non-pregnant, normotensive pregnant and pre-eclamptic patients: a prospective observational study

BACKGROUND

Prediction of a difficult airway is of paramount importance for an anaesthesiologist. Various anatomical and physiological factors contribute to a difficult airway in pregnant females, especially those with pre-eclampsia. The aim of the study was to assess airway indices using both routinely used clinical methods and ultrasound.

METHODS

Fifty-five non-pregnant females, 55 normotensive pregnant females and 55 females with pre-eclampsia were included in this prospective study. Clinical airway assessment was the modified Mallampati score, thyromental distance, hyomental distance, hyomental distance ratio, chest circumference, neck circumference and chest-to-neck circumference ratio. Sonographic assessment included tongue width, tongue volume, anterior neck soft tissue thickness at the level of hyoid, epiglottis and vocal cords, subglottic diameter, ratio of pre-epiglottic space to anterior, posterior and midpoint of anterior and posterior vocal folds.

RESULTS

Several significant differences were observed between pregnant and non-pregnant females, with additional changes in pre-eclamptic females. These included clinical parameters such as the modified Mallampati score and sonographic measurements of tongue width, tongue volume, subglottic diameter, anterior neck soft tissue thickness at the level of hyoid, epiglottis and vocal cords, and the ratio of pre-epiglottic space to anterior, posterior and midpoint of anterior and posterior vocal folds.

CONCLUSION

Routinely used clinical methods of airway assessment lack sensitivity and specificity. Ultrasound can visualise anatomical structures in the supraglottic and subglottic views and is encouraging as an airway assessment tool.

Examining the pediatric subglottic airway by ultrasound: A systematic review

OBJECTIVE

The purpose of this review was to determine the ability of ultrasound (US) to assess the subglottic airway in pediatric patients to estimate the appropriate size of endotracheal tube (ETT).

DATA SOURCES

Pubmed, Scopus, and Embase databases.

METHODS

A search of the literature was performed for studies that utilized ultrasonography to examine the minimal transverse diameter of the subglottic airway (MTDSA) in the pediatric (age < 18) population to estimate endotracheal tube (ETT) size. Articles were excluded if they involved adults or non-humans, had no comparison method, or were case reports. The primary outcome was the successful use of ultrasound compared to the reference standard defined by the study.

RESULTS

Sixteen studies were included, for a total of 1,633 pediatric subjects in whom transcervical laryngeal ultrasound was used prospectively to examine the MTDSA to estimate ETT size prior to intubation. Ultrasound reliably predicted the clinically best fit endotracheal tube by air leak test in 48-100% of subjects, while age-based formulas were accurate 24-95% of the time. Ultrasound was highly predictive of proper size, with R2 ranging between 0.684 to 0.980. Of those reintubated (n = 104), 86 (83%) required larger-sized tubes, while 18 (17%) required smaller-sized tubes. Both methods tended to underestimate ETT size, but the age-based formulas accounted for most of these differences.

CONCLUSION

Transcervical laryngeal ultrasound appears to be a reliable predictor of endotracheal tube size in children undergoing elective surgery, which has implications for preventing intubation-related trauma and ensuring adequate ventilation for those who may require prolonged intubation.

Ultrasonography measurement of glottic transverse diameter and subglottic diameter to predict endotracheal tube size in children: a prospective cohort study

We aimed to determine the correlation between mid-glottic transverse diameter/subglottic diameter and outer diameter of endotracheal tube (ETT) by ultrasonography in children. Ninety-five patients aged 1–8 years who underwent general anesthesia were included. Ultrasonography of glottic/subglottic transverse diameter was performed by two investigators after patients were anesthetized and when the train of four showed ≤ 4. The subglottic diameter was measured at the mid cricoid cartilage. The mid-glottic transverse diameter was measured at the mid-point of true vocal fold triangle whereas the distance between arytenoids was considered as the glottic transverse diameter. Linear regression models and correlation coefficients (r) were used to determine the best formula of glottic/subglottic transverse diameter to predict the outer diameter of ETT. The predicted outer diameter of ETT formula for subglottic diameter, mid-glottic transverse diameter, and glottic transverse diameter were 5.7 + (subglottic_mm/3) with an r of 0.45, 5.5 + (midglottic_mm/2) with an r of 0.47, and 5.7 + (glottic_mm/4) with an r of 0.46, respectively. The correlation between subglottic diameter and mid-glottic transverse diameter was 0.50. Subglottic/mid-glottic/glottic transverse diameter formulae had moderate correlations with the outer diameter of ETT. The glottic/mid-glottic transverse diameter can be used alternatively to predict the ETT size.

Trial registration: Thai Clinical Trial Registry: TCTR20191022002 Registered 22/10/2019—Prospectively registered, https://www.thaiclinicaltrials.org/# TCTR20191022002.

Safe ultrasound-guided percutaneous tracheostomy in eight steps and necessary precautions in COVID-19 patients

Percutaneous tracheostomy has been considered the standard method today, the bronchoscopy-guided technique being the most frequently performed. A safe alternative is ultrasound-guided percutaneous tracheostomy, which can be carried out by the surgeon, avoiding the logistical difficulties of having a specialist in bronchoscopy. Studies prove that the efficacy and safety of the ultrasound-guided technique are similar when compared to the bronchoscopy-guided one. Thus, it is of paramount importance that surgeons have ultrasound-guided percutaneous tracheostomy as a viable and beneficial alternative to the open procedure. In this article, we describe eight main steps in performing ultrasound-guided percutaneous tracheostomy, highlighting essential technical points that can reduce the risk of complications from the procedure. Furthermore, we detail some precautions that one must observe to reduce the risk of aerosolization and contamination of the team when percutaneous tracheostomy is indicated in patients with COVID-19.

Prediction of endotracheal tube size in the pediatric age group by ultrasound: A systematic review and meta-analysis

Anatomical differences in the airway in pediatric patients, compared to adults pose many challenges during endotracheal intubation, such as selecting the proper sized endotracheal tube (ETT) during intubation. Our primary objective was to assess how accurate is ultrasound (US) co-relation in comparison to standard age-based formulas in pediatric patients. Meta-analysis was registered in PROSPERO 2020, CRD42020220041. Online literature available in PubMed, Cochrane, and Embase, Goggle scholar was searched from year 2000 till November 30, 2020, using relevant Mesh terms, ('airway US' OR (('airway'/exp OR airway) AND ('US'/exp OR US))) AND ('endotracheal intubation'/exp OR 'endotracheal intubation') AND ('pediatric'/exp OR pediatric)" to Predict endotracheal tube size/placement in pediatric age (neonate till 18 years) by the US. Bibliographic cross-references of selected publications were further manually screened. The full texts of each article were studied, once the abstract was found appropriate independently by two reviewers. A total of 48 papers published between 2010 and 2020 were identified as relevant and read in detail. Average numbers of patients were 86 and total numbers of patients were 1978. Most of the studies included pediatric patients posted for elective surgeries under general anesthesia and excluded emergency procedures, known laryngeal or tracheal pathology, high-risk patients, recent upper respiratory tract infections or allergy to ultrasound gel. A total of 18 independent correlations were analyzed. Final combined r value calculated from all the included articles was 0.824 (95% CI 0.677, 0.908) with a P < 0.00001 {strong co-relation (r > 0.80)}. Q statistic of 756.484, and I² statistics of 97.53% showed a large degree of heterogeneity in the effect size across the studies. Use of US for upper airway in pediatric patients is an effective modality and can effectively predict endotracheal tube size estimations in comparison to standard age-based or height-based formulae in the pediatric age group. US is a non-invasive, cost-effective, portable, and reproducible technique as compared to CT and MRI. It also takes less time with increasing expertise and experience.

Age-Related Changes in Upper Airway Anatomy Via Ultrasonography in Pediatric Patients

PURPOSE

Ultrasonography is a portable, noninvasive tool that may be used to evaluate the upper airway. The purpose of our study was to present a systematic approach to identify salient features of the pediatric airway and determine whether ultrasonography can identify anatomical changes that occur with growth and development.

METHODS

We present a prospective, observational trial where patients included were between 1 day and 10 years of age presenting for elective surgery who had no known history of unfavorable airway pathology. We sequentially obtained 5 ultrasound views under anesthesia: (1) sagittal sternal notch view of the trachea, (2) sagittal longitudinal view of trachea (LT), (3) axial view at the level of the vocal cords (AVC), (4) axial view at the level of the cricoid membrane (AC), and (5) sagittal longitudinal submental space view (SM). A broadband linear array transducer was used to identify airway structures and perform measurements.

RESULTS

Eighty-four percent of enrolled patients underwent airway imaging and were analyzed using multiple regression and Spearman correlation (ρ). In view 1, tracheal diameter via sagittal sternal notch view was immeasurable because of air disturbance. In the LT view, the distance from the skin to the cricothyroid membrane (LT1) did not statistically increase with age in days (P = 0.06); however, the distance from the cricoid to thyroid cartilage (LT2) did correlate to age (P < 0.001; 99% confidence interval [CI], 1.8 × 10-5, 7.7 × 10-5; ρ = 0.77, P = 0.001). We found a statistically significant relationship between age and the distance between the anterior and posterior commissures (AVC2; P < 0.001; 99% CI, 1.0 × 10-4, 1.7 × 10-4; ρ = 0.80, P < 0.001), the distance from the skin to the posterior commissure (AVC3; P < 0.001; 99% CI, 9.6 × 10-5, 2.0 × 10-4; ρ = 0.73, P < 0.001), the distance to the cricoid cartilage (AC; P < 0.001; 99% CI, 2.0 × 10-5, 7.7 × 10-5; ρ = 0.66, P < 0.001), and the distance from the tongue base to the soft palate (SM2; P < 0.001; 9% CI, 1.8 × 10-4, 3.9 × 10-4; ρ = 0.85, P < 0.001). There were no significant relationships between age and AVC1 (P = 0.16) and SM1 (P = 0.44).

CONCLUSIONS

Airway ultrasound is a feasible tool to evaluate the pediatric airway in children younger than 10 years; however, the detection of age-related changes of certain structures is limited to select measurements.

Measurement of the subglottic diameter of the trachea and its distance from the skin by ultrasonography in children

OBJECTIVE

To investigate the relationship between age, sex, height, weight and body mass index (BMI) by measuring the subglottic diameter of the trachea (SDT) and its distance to the skin by ultrasonography (US) in children.

METHODS

This prospective study included a total of 234 children, 104 girls and 134 boys, with ages ranging from 3 to 17 years. Demographic data including sex, age, height, weight and BMI were recorded. The SDT and its distance to the skin was measured with a 14L5 high-frequency surface transducer. The correlation of SDT and its distance to the skin with basic descriptive data was investigated. Statistical analyses used were Mann-Whitney U, Kruskal-Wallis and Spearman correlation tests.

RESULTS

No significant difference was found among the median SDT and distance of the trachea from the skin values for boys (10.85 mm) and girls (11.15 mm) (p = 0.58). The distance of the trachea from the skin was greater in girls (5.5 mm) than in boys (4.75 mm) (p = 0.009). Median SDT values were 9.4 mm, 11.2 mm, and 13.35 mm in age groups 1, 2, and 3, respectively. There were highly significant strong positive correlations between SDT with age (p = 0.001, r = 0.78), height (p = 0.001, r = 0.76), and weight (p = 0.001, r = 0.70), and a highly significant moderate positive correlation between SDT with BMI (p = 0.001, r = 0.43). Median distance values of the trachea from the skin were 4.6 mm, 5.2 mm, and 6.2 mm in age groups 1, 2, and 3, respectively. There were moderate positive correlations between distance of the trachea from the skin with age (p = 0.001, r = 0.41), height (p = 0.001, r = 0.42), weight (p = 0.001, r = 0.53), and BMI (p = 0.001, r = 0.54).

CONCLUSION

US is an accurate, safe, inexpensive, non-invasive and accessible method for objective evaluation of SDT and its distance to the skin. There is a positive correlation between age, height, weight, and BMI with SDT and its distance to the skin in healthy children.

Is Ultrasonography a Better Method of Endotracheal Tube Size Estimation in Pediatric Age Group than the Conventional Physical Indices-Based Formulae?

Background:

Providing safe anaesthesia to paediatric patients is a challenging task. This requires a thorough knowledge of the soft and pliable paediatric airway. Owing to the vulnerability of the anatomical structures involved, choosing an appropiate sized endotracheal tube (ETT) is important in these cases. A larger sized ETT may lead to trauma and a smaller one would result in leakage and risk of aspiration. Both situations demand an immediate tube change, thereby complicating the condition. The physical indices- based formulae have often failed to justify the purpose leading to repeated laryngoscopy and tube change during intubation. The increase in availability of the modern ultrasound devices have shown promise in these cases.

Aims and Objectives:

In this study we examine the accuracy of ultrasonography (USG)to assess the appropriate ETT size, comparing it with physical indices based formulae suggested ETT size so that repeated attempts on intubation can be minimized.

Materials and Methods:

The study group included 100 patients of 1-5 years, ASA I- II, requiring orotracheal intubation under general anaesthesia. The tracheal sub-glottic diameter was estimated by pre-anaesthetic USG to determine the ETT size, both cuffed and uncuffed. ETT data obtained by these methods were compared by Pearson's correlation coefficient and t-test.

Results:

USG predicted ETT size were significantly more consistent than the physical indices based formulae. Also the age based formulae were found to be more precise than the height based ones. Seven patients required change of tube once.

Conclusion:

Ultrasonography is an effective tool in predicting paediatric ETT size.

Use of Airway Ultrasound in Infants With Unexpected Subglottic Stenosis During Anesthesia Induction: A Case Report

Point-of-care ultrasound has been integrated into airway management because it allows for rapid and noninvasive assessments. We present 2 cases of unexpected subglottic stenosis in infants during induction of anesthesia. Intubation failed even with endotracheal tubes that were small for patients' age. Airway ultrasound was used to measure the subglottic airway diameters, which were 2.0 and 3.0 mm in first and second cases, respectively. The severity of subglottic stenosis in the first case was grade III, requiring emergent tracheostomy. In conclusion, airway ultrasound helps to assess possibility of intubation and plan further airway management in children with unexpected difficult airway.

Accuracy of ultrasound to measure the cricoid cartilage diameter in children

BACKGROUND

Ultrasonography is used to pre-operatively predict the endotracheal tube size required for intubation by measuring the cricoid cartilage diameter. This study aimed to determine the accuracy of ultrasound measurements of the transverse diameters of the cricoid cartilage in children.

METHODS

We examined 50 children who underwent magnetic resonance imaging (MRI) scans at the HongHui Hospital, Xi'an Jiaotong University, from February 2019 to December 2019. Each child underwent MRI and ultrasound scans for measurement of the transverse diameters of the cricoid cartilage. The data measured by each technique were compared using Bland-Altman analysis and linear regression analysis.

RESULTS

Results of linear regression and Bland-Altman analysis showed strong correlation in the level of agreement between MRI and ultrasound measurements (r = 0.94, P < .001). The estimated bias was 0.11 mm; precision, 0.25 mm; and the limit of agreement, -0.47 to 0.70 mm.

CONCLUSION

Ultrasound is a reliable tool for measuring the transverse diameters of the cricoid cartilage in children.

Ultrasound-guided versus Shikani optical stylet-aided tracheal intubation: a prospective randomized study

Background

To compare ultrasound-guided tracheal intubation (UGTI) versus Shikani optical stylet (SOS)-aided tracheal intubation in patients with anticipated normal airway.

Methods

Sixty patients aged 18–65 years old who presented for elective surgery under general anesthesia were recruited in this prospective randomized study. They were assigned into two equal groups, either an ultrasound-guided group (Group UG, n = 30) or an SOS-aided group (Group SOS, n = 30). After the induction of anesthesia, the tracheal intubation was performed by a specified skilled anesthesiologist. The number of tracheal intubation attempt and the duration of successful intubation on the first attempt were recorded. Complications relative to tracheal intubation including desaturation, hoarseness and sore throat were also recorded.

Results

The first-attempt success rate is 93.3% (28/30) in Group UG and 90% (27/30) in Group SOS (P = 0.640). The second-attempt was all successful for the 2 and 3 patients left in the two groups, and the overall success rate of both groups was 100%. The duration of successful intubation on the first attempt of Group UG was not significantly different from that of Group SOS (34.0 ± 20.8 s vs 35.5 ± 23.2 s, P = 0.784). One patient in Group SOS had desaturation (P = 0.313), and there was none hoarseness in the two groups. Sore throat was detected in both group (4 in Group UG, 5 in Group SOS, P = 0.718).

Conclusion

Ultrasound-guided tracheal intubation was as effective as Shikani optical stylet-aided tracheal intubation in adult patients with anticipated normal airway.

Trial registration

Chinese Clinical Trial Registry, ChiCTR-IIC-17010875. Date of Registration: 15 March 2017.

The accuracy of ultrasound to predict endotracheal tube size for pediatric patients with congenital scoliosis

Background

Ultrasonography has been used to predict the necessary endotracheal tube (ETT) size by measuring the cricoid cartilage diameter. The aim of this study was to determine the accuracy of ultrasound to predict ETT size for pediatric patients with congenital scoliosis.

Methods

Fifty pediatric patients who underwent scoliosis surgery were included in the study. According to the position of the scoliosis, patients were divided into three groups: Group C (cervical lateral bending), Group T (thoracic scoliosis), and Group L (lumbar scoliosis). For all participants, the transverse diameter of the cricoid cartilage was measured with ultrasonography. The initial ETT size was chosen according to the measurements, then the leak test was used to determine the best-fit ETT size. The ETT size predicted by ultrasound and the best-fit ETT size were compared using Bland-Altman analysis.

Results

There was a strong correlation between the best-fit ETT size and the ETT size predicted by ultrasound in Group T (r = 0.93, p < 0.001) and Group L (r = 0.94, p < 0.001) and a moderate correlation in Group C (r = 0.83, p < 0.001). Bland-Altman analysis showed that the ETT size was overestimated by ultrasound in pediatric patients with cervical lateral bending (bias = 0.73 mm, precision = 0.42 mm, limit of agreement = 0.08 to 1.38 mm).

Conclusion

Ultrasound is a reliable tool to predict ETT size for pediatric patients with thoracic or lumbar scoliosis. However, pediatric patients with cervical lateral bending will need an ETT smaller than the size predicted by ultrasonography.

Trial registration

Chinese Clinical Trial Registry, TRN: ChiCTR1900023408, date of registration: 05.26.2019, ‘retrospectively registered’.

Airway ultrasound: Point of care in children-The time is now

BACKGROUND

Point-of-care ultrasonography of the airway is becoming a first-line noninvasive adjunct assessment tool of the pediatric airway. It is defined as a focused and goal-directed portable ultrasonography brought to the patient and performed and interpreted on the spot by the provider. Successful use requires a thorough understanding of airway anatomy and ultrasound experience.

AIMS

To outline the many benefits, and some limitations, of airway ultrasonography in the clinical and perioperative setting.

MATERIALS AND METHODS

Expert review of the recent literature.

RESULTS

Ultrasound assessment of the airway may provide the clinician with valuable information that is specific to the individual airway static and dynamic anatomy of the patient. Ultrasound can help identify vocal cord dysfunction and pathology, assess airway size, predict the appropriate diameter of endotracheal and tracheostomy tubes, differentiate tracheal from esophageal intubation, localize the cricothyroid membrane for emergency airway access and identify tracheal rings for US-guided tracheostomy. Ultrasonography is also a great tool for the intraoperative diagnosis of a pneumothorax, the visualization of the movement of the diaphragms, and quantifying the amount of gastric content. Ultrasonography signs, tips, and pearls that allow these diagnoses are highlighted. The major disadvantage of ultrasonography remains interobserver variability, and operator dependence, as it requires specific training and experience.

CONCLUSION

Although it is not standard of care yet, there is significant potential for the integration of ultrasound technology into the routine care of the airway.

Correlation between correctly sized uncuffed endotracheal tube and ultrasonographically determined subglottic diameter in paediatric population

Background and Aims:

Conventional age-based formulae often fail to predict correct size of endotracheal tube (ETT). In this study, we evaluated usefulness of ultrasound in determining appropriate tube size and derived a formula which enables us to predict correct tube size.

Methods:

A total of 41 American Society of Anesthesiologists' physical status 1 and 2 children in the age group of 2–6 years, undergoing elective surgery under general anaesthesia with uncuffed ETT were included in the study. Ultrasonography (US) was used to measure the subglottic diameter after induction of anaesthesia. The trachea was intubated with an ETT that allowed an audible leak between 15–30 mmHg. Pearson's correlation was used to assess the correlation between US measured subglottic diameter (US-SD) with diameter of ETT used. Linear regression was used to derive a formula for predicting ETT size.

Results:

We found that US-SD and patient's age correlated well with actual ETT OD (r: 0.83 and 0.84, respectively). Age-based formula, ETT ID = (Age/3) +3.5 [r: 0.81] had better correlation with actual ETT OD than conventional age-based Cole's formula, i.e., ETT ID = Age/4 + 4 [r: 0.77]. Our results enabled us to derive a formula for selecting uncuffed ETT based on US-SD.

Conclusion:

Our study concludes that although US-SD correlates with actual tracheal tube used and may be useful in choosing appropriate size ETT, there was no difference in number of correct predictions of ETT size by US measurement, universal formula, and locally derived formula.

Correlation between ultrasound-guided subglottic diameter and little finger breadth with the outer diameter of the endotracheal tube in paediatric patients - A prospective observational study

Background and Aims

Selection of an appropriate endotracheal tube (ETT) in paediatric patients is a challenging situation. The purpose of this study was to compare whether measurement of subglottic diameter with ultrasound or the age-old little finger width correlates better with the outer diameter (OD) of the ETT used for intubation.

Methods

Following approval from the Institutional Ethics board and a written informed consent from parent or guardian, this prospective observational study was carried out on 60 American Society of Anesthesiologists physical status I and II patients aged 6 months-8 years, scheduled for elective surgery under general anaesthesia requiring oral endotracheal intubation. Preoperatively ultrasound-guided subglottic diameter (USGD) and little finger breadth (LFB) measurements were taken. On the day of surgery, intubation was done with an uncuffed ETT, whose OD was noted. The concordance and agreeability between two techniques for estimation of the OD of the ETT were measured by Lin's concordance correlation coefficient. Further, the bias and precision between the techniques and the inter-changeability of the techniques were assessed by using Bland and Altman and Mountain plotting, respectively.

Results

Lin's concordance correlation coefficient between USGD and LFB with the OD of the ETT was found to be 0.29 (0.13-0.41) and 0.46 (0.29-0.6), respectively.

Conclusion

Overall, neither USGD nor LFB can be used as a reliable tool to predict the OD of the ETT. Registered in Clinical Trial Registry of India. REF/2016/08/011955.

Role of ultrasound measuring position and ventilation pressure in determining correct tube size in children

BACKGROUND

Ultrasound measurements of the airway are useful for determining correctly sized, uncuffed endotracheal tubes in children.

AIMS

The primary objective of this study was to evaluate the influence of ventilation pressure on the sonographically measured tracheal diameter at different levels.

METHODS

A total of 100 patients (under 7 years) were enrolled in this study. Six sonographic measurements of minimal transverse diameters at 3 locations (vocal chords, cricoid cartilage, and proximal trachea) and at 2 different ventilation pressures (0 and 15 mbar) were performed before the intubation procedure. The intubating anesthesiologists were blinded to the results of the ultrasound measurements. The rate of agreement of the outer diameter of the correctly sized endotracheal tube (reference) with the 6 sonographic diameters was determined. In addition, the correct tube sizes were compared with the results of traditional prediction methods (Penlington's and Cole's formula in children ≥1 year and a decision table in children <1 year).

RESULTS

Best rate of agreement resulted from cricoid cartilage (70% and 83% at 0 and 15 mbar).

CONCLUSION

The airway level selected for ultrasound and airway pressure during measurement determines the rate of agreement between the measurement result and correct ETT size.

Ultrasonographic Estimation of Endotracheal Tube Size in Paediatric Patients and its Comparison with Physical Indices Based Formulae: A Prospective Study

INTRODUCTION

Choosing the correct Endotracheal Tube (ETT) size is important in paediatric anaesthesia. The subglottic diameter being the narrowest diameter of the paediatric upper airway plays an important role in appropriate ETT size selection.

AIM

This study was planned to determine the accuracy of Ultrasonography (USG) to assess the appropriate ETT size and compare it with physical indices based formulae. The secondary outcome was to assess the number of times the tube was changed based on air leak test for USG estimated tube size.

MATERIALS AND METHODS

After ethical committee approval, a prospective clinical observational study for a period of one year was conducted on 75 children (power of study 80%, confidence interval 95%) aged one to 14 years of American Society of Anaesthesiologists Physical Status (ASA) I and II undergoing elective surgery under general anaesthesia with orotracheal intubation. Parental consent was obtained. Pre-anaesthetic ultrasonography was performed on every patient at the subglottic region. The tracheal subglottic diameter was estimated to select the ETT size for cuffed and uncuffed tubes. The size estimated by USG and that based on age and height based formulae were compared with clinically used appropriate tube size. Data analysis was done using IBM Statistical Package for the Social Sciences (SPSS) version 20.0; One-way Analysis of Variance (ANOVA) and t-test for comparison were used.

RESULTS

USG predicted the appropriate ETT size (p<0.05) better than physical indices based formulae for cuffed and uncuffed tubes. The age based formula predicted the clinically used ETT size well (p=0.58) and the height based formula did not correlate with clinically used tube size (p=0.0002 - a statistically significant value). Eight patients required change of tube once.

CONCLUSION

Ultrasonographic estimation of subglottic diameter is useful for optimal paediatric ETT size selection. USG is effective in estimating the appropriate sized ETT both for cuffed and uncuffed tubes.