The Feasibility of Ultrasound to Assess Subglottic Diameter

Evaluation of neck ultrasound measurements as a difficult airway predictor: A prospective observational study

This study aimed to investigate the relationship between cervical measurements and difficult airways using ultrasonographic measurements. American Society of Anesthesiologists grade I to III, male or female, 120 adult patients, undergoing elective surgery were enrolled in the study. The study involved measuring the distance of the trachea, cricoid cartilage, thyroid cartilage, vocal cord anterior commissure, and hyoid bone to the skin using a 10 to 13 MHz linear ultrasound probe in the transverse plane. Additionally, the length of the cricothyroid and thyrohyoid membranes, along with their distance from the skin, were measured using the probe in the sagittal plane. Subsequently, another experienced anesthesiologist conducted mask ventilation and intubation after the patient's induction of general anesthesia. Throughout this process, the patient was assessed for difficulties in mask ventilation, laryngoscopy, and intubation. 28 (23.3%) patients had a difficult airway. Analyzing the measurements associated with difficult airways, the most reliable predictor was the epiglottis midline-skin distance [AUC (area under the curve): 0.847, P < .001, cutoff: >19.9, sensitivity: 78.6%, specificity: 79.4%]. Additionally, other factors such as hyoid bone to skin distance, thyroid cartilage to skin distance, thyrohyoid membrane to skin distance, and vocal cord anterior commissure-skin distance were also identified as predictors for a difficult airway. The increase in the distance of the epiglottis midline, vocal cord anterior commissure, hyoid bone, thyrohyoid membrane, and thyroid cartilage to the skin at the level of the isthmus measured by ultrasonography is predictive of difficult airways. Based on our study outcomes, we assert that ultrasonographic evaluation can be used in the prediction of difficult airways.

Point-of-care ultrasound for non-vascular invasive procedures in critically ill neonates and children: current status and future perspectives

Point-of-care ultrasound (POCUS) has been established as an essential bedside tool for real-time image guidance of invasive procedures in critically ill neonates and children. While procedural guidance using POCUS has become the standard of care across many adult medicine subspecialties, its use has more recently gained popularity in neonatal and pediatric medicine due in part to improvement in technology and integration of POCUS into physician training programs. With increasing use, emerging data have supported its adoption and shown improvement in pediatric outcomes. Procedures that have traditionally relied on physical landmarks, such as thoracentesis and lumbar puncture, can now be performed under direct visualization using POCUS, increasing success, and reducing complications in our most vulnerable patients. In this review, we describe a global and comprehensive use of POCUS to assist all steps of different non-vascular invasive procedures and the evidence base to support such approach.

CONCLUSION

There has been a recent growth of supportive evidence for using point-of-care ultrasound to guide neonatal and pediatric percutaneous procedural interventions. A global and comprehensive approach for the use of point-of-care ultrasound allows to assist all steps of different, non-vascular, invasive procedures.

WHAT IS KNOWN

• Point-of-care ultrasound has been established as a powerful tool providing for real-time image guidance of invasive procedures in critically ill neonates and children and allowing to increase both safety and success.

WHAT IS NEW

• A global and comprehensive use of point-of-care ultrasound allows to assist all steps of different, non-vascular, invasive procedures: from diagnosis to semi-quantitative assessment, and from real-time puncture to follow-up.

Role of ultrasonography in upper airway assessment: A comparison with computerized tomography measurements

INTRODUCTION

This study aimed to compare ultrasonography (US) measurements of the upper airway to computerized tomography (CT) measurements. Our study's primary outcome is to research the accuracy of US measurements in the evaluation of upper airway diameters when CT is taken as the gold standard; the secondary outcome is to determine the time required to obtain US measurements.

METHODS

This prospective study included patients ≥18 years old that had undergone thoracic or neck CT due to current clinical necessity. The US measurement for each patient was performed by two researchers with different levels of experience, both of whom were blinded to each other and the CT measurements. Measurements were obtained from the vocal cords and subglottic region. The duration of the US performance was also recorded.

RESULTS

The US and CT measurements were obtained from 94 patients. Concordance between US and CT measurements was found in the Bland-Altman analysis, with a mean -0.05 mm difference for vocal cord diameter and -1.2 mm for subglottic diameter. The intra-class correlation coefficients (ICC) between the CT and US measurements were 0.993, and 0.609 for vocal cord and subglottic diameter measurements, respectively. The ICC between US performers was 0.992 for vocal cord diameter and 0.959 for subglottic diameter. The US's mean time for vocal cord diameter measurement was 38 ± 23 s, and the mean time for subglottic diameter measurement was 49 ± 30 s.

CONCLUSION

The concordance between US and CT measurements is high and the measurements of different practitioners with different experience levels are compatible with each other.

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.

Point-of-care ultrasound-guided submucosal paclitaxel injection in tracheal stenosis model

Background and Objectives

Transcutaneous point-of-care ultrasound (POCUS) is a good tool to monitor the trachea in many clinical practices. The aim of our study is to verify the feasibility of POCUS-guided submucosal injection as a potential drug delivery method for the treatment of tracheal stenosis.

Materials and methods

The inner wall of the trachea was monitored via a bronchoscope during the POCUS-guided submucosal injection of methylene blue in fresh ex vivo porcine trachea to evaluate the distribution of methylene blue. The feasibility and eficacy of POCUS-guided submucosal injection were evaluated in a tracheal stenosis rabbit model. Animals were divided into sham group, tracheal stenosis group, and treatment group. Ten days after the scraping of the tracheal mucosa or sham operation, POCUS-guided submucosal injection of paclitaxel or saline was performed. Seven days after the submucosal injection, the trachea was assessed by cervical computed tomography (CT) scan and ultrasound.

Results

The distribution of methylene blue in trachea proved the technical feasibility of POCUS-guided submucosal injection. CT evaluation revealed that the tracheal stenosis index and the degree of tracheal stenosis increased significantly in the stenosis group, while POCUS-guided submucosal injection of paclitaxel partially reversed the tracheal stenosis. POCUS-guided submucosal injection of paclitaxel also decreased the lamina propria thickness and collagen deposition in the stenosed trachea.

Conclusion

POCUS-guided submucosal paclitaxel injection alleviated tracheal stenosis induced by scraping of the tracheal mucosa. POCUS-guided submucosal injection might be a potential method for the treatment of tracheal stenosis.

Comparison of Ultrasound Examination and Fiberoptic Laryngoscopy for Confirmation of Laryngeal Mask Airway Placement

OBJECTIVES

1) To compare ultrasound (US) examination and fiberoptic laryngoscopy (FOL) for confirmation of laryngeal mask airway (LMA) placement. 2) To evaluate the necessity for reinsertion of LMA based on FOL.

METHODS

This prospective observational study included 100 adult patients of American Society of Anesthesiologists (ASA) Grade I and II, undergoing elective surgery under General Anesthesia requiring Proseal LMA™ placement as an airway device. LMA placement was first confirmed by clinical tests. Clinically acceptable patients were further assessed by US and categorized as acceptable (US-A) or unacceptable (US-U) and again by FOL as (FOL-A and FOL-U). Categorical variables presented in number, percentage (%), and continuous variables presented as mean ± SD and median. Inter-rater kappa agreement was used to find out the strength of agreement of acceptability between FOL and US.

RESULTS

The LMA placement was clinically acceptable in 82% of patients on first attempt. FOL had 63% (FOL-A) acceptable LMA placement as compared with US examination which had 56% (US-A). In 85% of patients, US and FOL findings were in good agreement with each other for LMA placement (κ = 0.690 and P < .05). In all patients of FOL of unacceptable (FOL-U) category (37%), LMA was replaced with endotracheal tube.

CONCLUSION

US provides a safe, non-invasive, and real-time dynamic assessment with 85% diagnostic accuracy for confirmation of LMA placement as compared with FOL.

Neonatal and paediatric point-of-care ultrasound review

Purpose

Point-of-care ultrasound (POCUS) examinations for children and newborns are different from POCUS exams for adults due to dissimilarities in size and body composition, as well as distinct surgical procedures and pathologies in the paediatric patient. This review describes the major paediatric POCUS exams and how to perform them and summarizes the current evidence-based perioperative applications of POCUS in paediatric and neonatal patients.

Method

Literature searches using PubMed and Google Scholar databases for the period from January 2000 to November 2021 that included MeSH headings of [ultrasonography] and [point of care systems] and keywords including "ultrasound" for studies involving children aged 0 to 18 years.

Results

Paediatric and neonatal POCUS exams can evaluate airway, gastric, pulmonary, cardiac, abdominal, vascular, and cerebral systems.

Discussion

POCUS is rapidly expanding in its utility and presence in the perioperative care of paediatric and neonatal patients as their anatomy and pathophysiology are uniquely suited for ultrasound imaging applications that extend beyond the standard adult POCUS exams.

Conclusions

Paediatric POCUS is a powerful adjunct that complements and augments clinical diagnostic evaluation and treatment.

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.

Airway Ultrasound in Critically Ill Patients: A Narrative Review

Airway assessment and management have a central role in critical care medicine. Airway ultrasound can help us evaluate the anatomy, facilitate interventions such as intubation in difficult airways and tracheostomy, prevent post-extubation complications, and diagnose dysphagia. In this review, we will summarize the current use of ultrasound in airway assessment and management in critically ill patients.

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.

Point-of-care ultrasound to confirm endotracheal tube cuff position in relationship to the cricoid in the pediatric population

BACKGROUND

Anatomically, the subglottic area and the cricoid ring are the narrowest portions of the larynx. To limit the potential for damage related to mucosal pressure injuries from the presence of an endotracheal tube, the cuff should be placed below the cricoid in children. Previously, no clinical or imaging method has been used in real time to determine the exact location of the endotracheal tube cuff after endotracheal intubation. Point-of-care ultrasound may provide an option as a safe and rapid means of visualizing the endotracheal tube cuff and its relationship to the cricoid ring thereby achieving ideal endotracheal tube cuff positioning-below the cricoid.

METHODS

In this prospective, nonrandomized trial, point-of-care ultrasound was used following endotracheal intubation in children to evaluate the position of the endotracheal tube cuff in relationship to the cricoid and tracheal rings. After anesthesia was induced and the trachea was intubated, the endotracheal tube cuff and its position in relation to the cricoid and tracheal rings were identified in the longitudinal plane using point-of-care ultrasound. With the patient's neck in a neutral position, the level of the proximal (cephalad) margin of the saline-filled cuff of the endotracheal tube was identified and recorded in relationship to the cricoid and tracheal rings. The ideal position is defined as the cephalad margin of the endotracheal tube cuff below the level of the cricoid.

RESULTS

The study cohort included 80 patients, ranging in age from 1 to 78 months. In all patients, the cuff of the ETT, cricoid, and tracheal rings were identified. The cephalad end of the endotracheal tube cuff was found at the level of the cricoid in 16.3% of patients, at the first tracheal ring in 27.5% of patients, at the second tracheal ring in 23.8% of patients, at the third tracheal ring in 17.5% of patients, and at below the fourth tracheal ring in 15% of patients. Initial endotracheal tube cuff position had no significant association with age, height, weight, endotracheal tube size, and endotracheal tube type.

CONCLUSION

Point-of-care ultrasound provides a rapid and effective means of identifying the position of the endotracheal tube cuff in relationship to the cricoid ring. The technique may have applications in the perioperative arena, emergency departments, and intensive care units.

Correlation of airway ultrasonography and laryngoscopy findings in adults with subglottic stenosis: a pilot study

PURPOSE

Ultrasonography of the airway has potential as an alternative, non-invasive, method to monitor patients with subglottic stenosis in an outpatient setting. This prospective, interventional, double-blinded study aimed to correlate ultrasound-based and laryngoscopy-based subglottic stenosis assessment in adults.

METHODS

The study was conducted between July 2020 and March 2021 at a tertiary referral center. Consecutive adult patients with subglottic stenosis were evaluated using airway ultrasonography 1 day prior to scheduled laryngoscopy. The radiologist was blinded to the preoperative endoscopic findings, and the primary surgeon was blinded to the ultrasonographic measurements. The intraoperative subglottic diameter was defined as the outer diameter of an endotracheal tube passing through the subglottis without producing an air leak.

RESULTS

Sixteen patients (11 females; age range, 17-66 years; mean = 44.06, SD = 12.79) were included. The ultrasonographic subglottic diameter ranged from 5.20 mm to 8.00 mm (mean = 6.24 mm, SD = 0.90). In 15 of 16 patients, the diameter difference between the ultrasonographic and intraoperative measurements ranged from -0.80 mm to 0.30 mm (mean = -0.20 mm, SD = 0.35). However, patient 6 had a difference of - 2.10 mm between the two measurements, which was attributed to thick laryngotracheal secretions interfering with the ultrasonographic air shadow. Data analysis of all 16 patients showed a statistically significant correlation between the readings obtained by the two techniques (r = 0.84, P = 0.000051).

CONCLUSION

This study found a significant correlation between ultrasonography-based and laryngoscopy-based subglottic stenosis assessment in adult patients. It provides a basis for an alternative and potentially reliable method to monitor patients with subglottic stenosis.

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.

Assessing the accuracy of ultrasound measurements of tracheal diameter: an in vitro experimental study

Background

Recent studies indicate that ultrasound can detect changes in tracheal diameter during endotracheal tube (ETT) cuff inflation. We sought to assess the accuracy of ultrasound measurement of tracheal diameter, and to determine the relationship between tracheal wall pressure (TWP), cuff inflation volume (CIV), and the degree of tracheal deformation.

Methods

Our study comprised two parts: the first included 45 porcine tracheas, the second 41 porcine tracheas. Each trachea was intubated with a cuffed ETT, which was connected to an injector and the manometer via a three-way tap. The cuff was inflated and the cuff pressure recorded before and after intubation. The tracheal diameter was measured using ultrasound. This included three separate measurements: outer transverse diameter (OTD), internal transverse diameter (ITD), and anterior tracheal wall thicknesses (ATWT). A precision electronic Vernier caliper was also used to measure tracheal diameter. We calculated TWP and the percentage change of tracheal diameter. The Bland–Altman method, linear regression, and locally weighted regression (LOESS) were used to analyze the data.

Results

There were strong correlation and agreement for OTD (r = 0.97, P < 0.001) and ITD (r = 0.90, P < 0.001) as measured by ultrasound and by precision electronic Vernier caliper, but a poor correlation for ATWT (r = 0.58, P < 0.001). There was a strong correlation between the percentage change of OTD (OTD%, r = 0.75, P < 0.001) and CIV, the percentage change of ITD (ITD%, r = 0.77, P < 0.001) and CIV, TWP (r = 0.75, P < 0.001) and CIV. And a strong correlation was also found between TWP and OTD% (r = 0.84, P < 0.001), TWP and ITD% (r = 0.84, P < 0.001).

Conclusions

Use of ultrasound to measure OTD and ITD is accurate, but is less accurate for ATWT. There is a close correlation between OTD%, ITD%, CIV and TWP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01398-3.

Ultrasound for assessment and follow-up of airway stenosis

BACKGROUND

Ultrasound is a reliable tool for airway assessment and management. We evaluated the accuracy of Ultrasound in the pre-procedure planning and follow-up evaluation of patients undergoing airway stenting for benign upper airway stenosis.

METHODS

This was a retrospective single center study on patients with benign upper airway stenosis treated with airway stenting. Ultrasound evaluated the characteristics of the stenosis (distance from vocal folds, diameter and length) before treatment and any complications after treatment; these results were then statistically compared with those obtained by computed tomography, taking the endoscopy as the reference method.

RESULTS

Twenty-seven patients were evaluated. Ultrasound was significantly correlated with endoscopy and computed tomography scan measurements as distance of stenosis from vocal folds (r=0.88; p<0.001 and r=0.87; p<0.001, respectively); diameter of the stenosis (r=0.97; p<0.001 and r=0.97; p<0.001, respectively); and length of the stenosis (r=0.97; p<0.001 and r=0.97; p<0.001, respectively). Four out of 27 (15%) patients presented complications after treatment as stent migration (n=2; 7%); stent obstruction (n=1; 4%), and granulation of vocal fold (n=1; 4%). All complications but granulation of vocal fold were correctly depicted by Ultrasound and Computed Tomography without significant difference in comparison to endoscopy (p=0.87) CONCLUSIONS: Ultrasound is a promising tool in assessment of airway stenosis and follow-up of patients after stenting; it may be routinely used in adjunction to computed tomography and/or endoscopy in this setting, if our results are corroborated by future larger study.

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.

Point of care airway ultrasound to select tracheal tube and determine insertion depth in cleft repair surgery

We aimed to evaluate the efficacy of using airway ultrasonography to select the correct tracheal tube size and insertion depth in pediatric patients who underwent cleft repair surgery as a way to decrease airway complications and adverse events during perioperative periods. Fifty-one patients (age < 28 months) were consecutively divided into conventional (n = 28) and ultrasound (n = 23) groups. Tracheal tube size and insertion depth were determined using the age-based formula and auscultation in the conventional group, whereas using ultrasonographic measurement of subglottic diameter with auscultation and lung ultrasonography in the ultrasound group. We evaluated the initially selected tube size, insertion depth, ventilatory indices, and the incidence of airway complications and adverse events. Tube insertion depth (median [interquartile range]) was significantly greater in the ultrasound group than in the conventional group (13.5 cm [12.5-14.0] vs 13.0 cm [11.8-13.0], P = 0.045). The number of complications and adverse events was significantly higher in the conventional group than in the ultrasound group (32.1% vs 4.3%, P = 0.013). Airway ultrasound application could reduce airway-related complications and adverse events by determining the appropriate tracheal tube size and insertion depth.

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.

Ultrasound as a bedside tool for diagnosis of post-intubation tracheal stenosis

Background

Screening of post-intubation stenosis can allow early diagnosis, early management of stenosis, and possible prevention of progress. Fiberoptic bronchoscope is the gold standard for diagnosis of tracheal stenosis. Other imaging modalities as computed tomography can be considered but are not available in intensive care unit.

Purpose of the study

To evaluate the validity of ultrasound (US) as a bedside test for early diagnosis of post-intubation stenosis compared to multidetector computed tomography (MDCT) and fiberoptic bronchoscope (FOB).

Results

Out of the 50 included patients, 12 patients were found to have definite stenosis by FOB. Compared to CT, significant positive correlation was found between all ultrasound parameters (laryngeal width, tracheal diameter) and corresponding CT parameters (r = 0.798, p < 0.001; r = 0.714, p < 0.001 respectively). Compared to FOB results, the yield of MDCT chest for diagnosis of stenosis had 91.6% sensitivity and 100% specificity, while the yield of US detected by mucosal irregularity as a diagnostic tool for tracheal stenosis had comparable sensitivity (91.6%) but lower specificity (88.9%).

Conclusion

Due to its high sensitivity, US could help in detection of possible post-intubation laryngotracheal stenosis in critically ill MV patients.

Pre-extubation ultrasonographic measurement of intracricoid peritubal free space: A pilot study to predict post-extubation airway obstruction in children

OBJECTIVE

Post-extubation airway obstruction (PEAO) is common and difficult to predict in children. We hypothesized that Intracricoid Peritubal Free Space (IPFS) obtained by deducting the outer diameter of the endotracheal tube in situ (OD_TT - provided by the manufacturer) from the ultrasonographically measured internal transverse cricoid diameter (ICD_t) is likely to be inversely proportional to the risk of developing PEAO. This prospective observational study was planned to evaluate this hypothesis.

METHODS

This study was conducted in a Pediatric Intensive Care Unit of a tertiary care teaching hospital in a low-middle income economy. Laryngotracheal ultrasound was performed just prior to the first elective extubation in 93 patients (3mo-12yrs) intubated for ≥ 48 h, to calculate the IPFS. Patients with pre-existent upper airway conditions, chronic respiratory diseases and poor airway reflexes were excluded. Patients with Westley's Croup Score (WCS) ≥4 were classified as PEAO, and those with WCS ≥7, as extubation failure (EF).

RESULTS

Thirty-two (34%) patients developed PEAO, while seventeen (18%) developed EF. Baseline clinical characteristics were similar in patients with and without PEAO. IPFS was lesser in patients who developed PEAO (4.16 ± 1.18 mm vs. 5.28 ± 1.51 mm, p < 0.001) and EF (4.13 ± 1.44 mm vs. 5.07 ± 1.46 mm, p = 0.019) compared to those who did not. IPFS <5.16 mm predicted PEAO [sensitivity, 84%; positive predictive value (PPV), 87%; AUC, 0.714), while IPFS <3.77 mm predicted EF (specificity, 80%; PPV, 88%; AUC, 0.679). Combining clinical risk factors (presence of clinical edema, prolonged ventilation and younger age) and lesser IPFS helped develop a clinico-sonographic prediction model with improved predictability for PEAO and EF (AUC, 0.820 for both).

CONCLUSIONS

Lesser IPFS is reasonably sensitive and specific to predict PEAO and EF respectively with high PPV. Combining clinical risk factors and IPFS improved the PPV further. Further studies with larger samples stratified for different age groups in different clinical settings are required to confirm these observations.

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.

Airways ultrasound in predicting difficult face mask ventilation

BACKGROUND

Unanticipated difficult airway is a potentially life-threatening event during elective surgery or management of critical conditions. Nevertheless, predicting difficult mask ventilation currently remains a challenge due to the poor sensitivity of available clinical tests. Our primary goal was to verify whether preoperative upper airway ultrasound measurements were useful to predict difficult face mask ventilation. Our secondary goal was to evaluate clinical characteristics and differences between patients who are difficult to ventilate and patients who are not.

METHODS

We performed a prospective observational study, enrolling 250 adult patients selected for colorectal, gastric, bariatric and pancreatic elective surgery between September 2017 and October 2018. We performed a preoperative US assessment of the airways, following a standardized protocol. We measured the hyomental distance (DIM), the thickness of the base of the tongue (SBL), the thickness of the soft tissues anterior to the hyoid bone (STTi), thyro-hyoid distance (DTI), the thickness of soft tissue anterior to the epiglottis (STTe), to the arytenoid (STTa) and to the commissure of the vocal cords (STTcv).

RESULTS

SBL had a predictive role of difficult mask ventilation in curarized and noncurarized patients for values higher than 50 mm. Hyomental distance with hyperextension of the head and subluxation of the mandible (DIMs) had a predictive role in the curarized patient (protective parameter).

CONCLUSIONS

Airways ultrasound evaluation could be an important tool to predict difficult mask ventilation. Further studies are necessary to validate the parameters found and correlate them to the preoperative clinical evaluation.

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’.

Prediction of Double-Lumen Tube Size By Ultrasonography for Asian Women: A Prospective Observational Study

OBJECTIVE

To assess the agreement of the diameter of the cricoid cartilage by computed tomography and ultrasonography and to compare the accuracy of the left double-lumen tubes (DLTs) and right DLTs predicted by ultrasonography for Asian women.

DESIGN

Prospective observational study.

SETTING

Academic, tertiary care hospital.

PARTICIPANTS

Fifty female patients intubated with a left DLT and 50 female patients intubated with a right DLT.

INTERVENTIONS

No intervention.

MEASUREMENTS AND MAIN RESULTS

A radiologist measured the transverse cricoid diameter by computed tomography (CT), and an independent echographer measured the transverse cricoid diameter using ultrasonography. The size of the DLT was selected based on the cricoid diameter by ultrasonography. The agreement of the transverse cricoid diameter was assessed by computed tomography and ultrasonography. The accuracy of the DLT, the tracheal segment, and the bronchial segment were compared between the left intubation group and right intubation group. There was a good agreement between the transverse cricoid diameter measured by ultrasonography and CT (r = 0.946, p < 0.001). The overall accuracy of the DLTs was similar between the groups (86.0% v 92.0%, p = 0.318). There were no significant differences in the accuracy of the tracheal segment (96.0% v 94.0%; p = 1.000) and the bronchial segment (90.0% v 98.0%, p = 0.056).

CONCLUSIONS

The transverse diameter of the cricoid cartilage in most Asian women can be accurately measured by ultrasonography. The size of the DLT for Asian women can be predicted by ultrasonography measurement of the cricoid diameter.

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.

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.

Pilot Study to Assess the Use of Ultrasound in Evaluating the Abnormal Pediatric Airway

In this study, we sought to explore the feasibility of using ultrasonography to evaluate airway anomalies in awake children with previous airway reconstruction. For the month of December 2018, we reviewed the medical records of patients aged <18 years old with prior airway reconstruction who had an outpatient appointment and a microlaryngoscopy and bronchoscopy within 24 hours of each other. Four patients met inclusion criteria and were enrolled. Sonographic airway images and measurements were obtained during the outpatient appointment and compared with those obtained during endoscopy. Ultrasound identified extraluminal stents and glottic, subglottic, and tracheal pathology. Subglottic measurements obtained sonographically were within 0.1 to 0.5 mm of the outer diameter of the appropriate endotracheal tubes. Ultrasound did not visualize tracheotomy tubes or posterolateral pathology. Our findings lay the foundation for expanding the role of ultrasound in pediatric airway assessment, keeping in mind its apparent inability to visualize posterolateral airway pathology.

Tracheomegaly among Extremely Preterm Infants on Prolonged Mechanical Ventilation

By using phantom radiographs, the accuracy of tracheal measurements was established. Preterm infants (≤29 weeks) were enrolled in short (<7 days) and prolonged ventilation (≥28 days) groups. Both groups had 3 weight categories, namely, <1000 g, 1000-1999 g, and >2000 g. Tracheal sizes were measured on serial chest radiographs (CXR). We noted tracheomegaly in association with prolonged ventilation at ≥1000 g.

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.

Ultrasonographic assessment of airway

Ultrasound is gaining increasing popularity among anesthesiologists as it is readily available and provides real-time imaging for various procedures. It is considered as a “visual stethoscope” of the anesthesiologist. After establishing its use in regional blocks and central venous catheter insertion, it is now finding increasing use in anticipation of difficult airway and securing and maintaining it. It has challenged the classical approach of clinical assessment of airway and allows more dynamic bedside assessment. This article attempts to briefly outline the role of ultrasound and its applications for airway management in patients.

Ultrasound for airway management: An evidence-based review for the emergency clinician

BACKGROUND

Airway management is a common procedure performed in the Emergency Department with significant potential for complications. Many of the traditional physical examination maneuvers have limitations in the assessment and management of difficult airways. Point-of-care ultrasound (POCUS) has been increasingly studied for the evaluation and management of the airway in a variety of settings.

OBJECTIVE

This article summarizes the current literature on POCUS for airway assessment, intubation confirmation, endotracheal tube (ETT) depth assessment, and performing cricothyroidotomy with an emphasis on those components most relevant for the Emergency Medicine clinician.

DISCUSSION

POCUS can be a useful tool for identifying difficult airways by measuring the distance from the skin to the thyrohyoid membrane, hyoid bone, or epiglottis. It can also predict ETT size better than age-based formulae. POCUS is highly accurate for confirming ETT placement in adult and pediatric patients. The typical approach involves transtracheal visualization but can also include lung sliding and diaphragmatic elevation. ETT depth can be assessed by visualizing the ETT cuff in the trachea, as well as using lung sliding and the lung pulse sign. Finally, POCUS can identify the cricothyroid membrane more quickly and accurately than the landmark-based approach.

CONCLUSION

Airway management is a core skill in the Emergency Department. POCUS can be a valuable tool with applications ranging from airway assessment to dynamic cricothyroidotomy. This paper summarizes the key literature on POCUS for airway management.

Learning curve of ultrasound measurement of subglottic diameter for endotracheal tube selection in pediatric patients

BACKGROUND

Endotracheal tube size can be predicted according to ultrasound measurement of subglottic airway diameter. The learning curve for this method is not yet established. The aim was to evaluate the learning curve of anesthesiology residents in ultrasound measurement of subglottic airway diameter for prediction of endotracheal tube size using cumulative sum analysis.

METHODS

Sixteen anesthesiology residents measured transverse subglottic airway diameter in children undergoing general anesthesia with cuffed endotracheal intubation. Each resident performed 30 ultrasound examinations. Primary outcome was the successful prediction of endotracheal tube size according to ultrasound measurement. Cumulative sum analysis was performed with acceptable and unacceptable failure rates set as 20 and 40%, respectively.

RESULTS

Ten out of 16 residents (62.5%) were deemed successful as they were able to pass lower decision boundary, whereas six residents' CUSUM scores were between the decisions lines deeming them indeterminate. The overall success rate for determining the correct endotracheal tube size was 77.5%. Median number of attempts to cross lower decision boundary was 29 with minimum of 18 and maximum of 29 attempts among successful residents.

CONCLUSION

Learning curves constructed with cumulative sum analysis in this study showed that only 62.5% of residents were able to correctly predict cuffed endotracheal tube size with 80% success rate. Considerable variability in achieving competency necessitates objective follow-up of individual improvement.

Point of care ultrasound for the clinical anesthesiologist

Diagnostic ultrasonography was first utilized in the 1940s. The past 70+ years have seen an explosion in both ultrasound technology and availability of ultrasound technology to more and more clinicians. As ultrasound technology and availability have grown, the utility of ultrasound technology in the clinical setting as only been limited by clinicians' imagination. Due to its lack of radiation, non-invasive nature, and gentle learning curve, medical ultrasonography is now a tremendously useful Point of Care technology in the clinical arena. What follows is a discussion of Point of Care Ultrasound (PoCUS) and how it can be incorporated in the daily practice of any regional anesthesiology. While most regional anesthesiologists usually focus on the interventional aspects of ultrasonography (i.e. nerve blocks), our discussion will center on the diagnostic value of ultrasonography-especially concerning assessment of cardiac physiology and pathophysiology, gastric anatomy, airway anatomy, and intracranial pathophysiology. After reading and reviewing this chapter, the learner will have the knowledge to start training themselves in a variety of PoCUS exams that will allow rapid diagnosis of normal and abnormal patient conditions. Once an accurate diagnosis is established, the anesthesiologist and his/her team can then confidently optimize an anesthetic pain, prevent harm, and/or treat a patient condition. In this day and age, the ability to rapidly establish an accurate diagnosis cannot be overstated-especially in a critical situation. It is the authors' sincerest hope that the following discussion will help regional anesthesiologist to become even better and well-rounded clinical leaders.

Objective Assessment of Postoperative Swallowing Difficulty Through Ultrasound in Patients Undergoing Thyroidectomy

Swallowing discomfort is a common postoperative complaint in patients undergoing thyroidectomy. Contraction of the strap muscles might cause resistance to elevation of the laryngotracheal unit, and downward movement of the laryngotracheal unit may lead to swallowing discomfort. However, few studies have evaluated the mechanism related to limited laryngotracheal elevation after thyroidectomy. We aimed to objectively verify the presence of postoperative impaired laryngotracheal elevation through ultrasound evaluation in patients undergoing thyroidectomy and evaluate its relationship with limitation of laryngotracheal elevation. This is a prospective clinical study. Among patients undergoing hemithyroidectomy and total thyroidectomy, the patients who were followed up for ≥ 6 months were selected (N = 40). Ultrasound evaluation was done preoperatively and at 1, 3, and 6 months postoperatively. Laryngotracheal movement was recorded and the length of elevation was measured. Symptom after thyroidectomy was evaluated through swallowing-related items of thyroidectomy-related voice questionnaire. Ultrasound evaluation verified the presence of limited laryngotracheal elevation postoperatively in patients undergoing thyroidectomy. After thyroidectomy, the swallowing-related score was significantly increased, and was recovered time-dependently at 1 month. Laryngotracheal elevation showed significant decrease after thyroidectomy. The symptom score of swallowing was significantly correlated with the length of laryngotracheal elevation. Post-thyroidectomy ultrasound evaluation verified that laryngotracheal elevation was significantly impaired. Presence of adhesion between the laryngotracheal unit and the superficial soft tissue was the probable cause of the limitation at 6 months after thyroidectomy. The length of laryngotracheal elevation was related to the symptom score of swallowing after thyroid surgery.

Usefulness of ultrasound-guided measurement of minimal transverse diameter of subglottic airway in determining the endotracheal tube size in children with congenital heart disease: A prospective observational study

Introduction

The search for an accurate and predictable method to estimate the endotracheal tube (ETT) size in pediatric population had led to derivation of many formulae. Of this, age-based formulae are the most commonly used. Studies have shown that minimal transverse diameter of subglottic airway (MTDSA) measurements using a high-frequency probe improves the success rate of predicting the airway diameter to about 90%. We did a prospective observational study using MTDSA as the criteria to select the size of ETT in children with congenital heart disease.

Methods

In this prospective observational study, 51 children aged from 1 day to 5 years, scheduled for cardiac surgery, were enrolled for this study. The ETT size was guided solely based on the MTDSA. Leak test was used to determine the best-fit ETT size.

Results

Data from 49 patients were analyzed. Agreement between the ETT determined by MTDSA and that predicted by Cole's age-based formulas with the best-fit ETT size was analyzed using a Bland-Altman plot.

Conclusion

Age-based formula showed poor correlation (27.5%) compared to MTDSA (87.8%) in predicting the best-fit ETT. We observed that pediatric patients with congenital heart disease need a larger sized ETT as compared to what was predicted by age-based formula. Using ultrasound MTDSA measurements to guide selection of ETT size is a safe and accurate method in pediatric cardiac population.

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.