Ultrasound measurement of subglottic diameter and an empirical formula for proper endotracheal tube fitting in children

The accuracy of the ultrasound measured transverse cricoid diameter and the epiphyseal transverse diameter of the distal radius in predicting the pediatric endotracheal tube size

BACKGROUND

In everyday pediatric anesthesia practice, clinicians frequently exchange an already inserted endotracheal tube because of a leak or resistance causing significant morbidity. We investigated the accuracy of two ultrasound measurements; the transverse cricoid diameter and epiphyseal diameter of the distal radius in the prediction of endotracheal tube size that best fits in children compared to age-based formulas.

PATIENTS

One hundred children (1-6 years) who underwent elective surgery with endotracheal tube whether cuffed (n = 50) or uncuffed (n = 50) were enrolled. The primary endpoint was the agreement between the reference tube size for which its outer diameter was selected based on transverse cricoid diameter and the final best-fit-ETT. The Correlation and Bland Altman agreement tests were conducted between best-fit-ETT outer diameter and ultrasound-measured outer diameter, and between best-fit-ETT inner diameter and inner diameter calculated by age-based formulas.

RESULTS

The agreement rate between transverse cricoid diameter-based endotracheal tube size and best-fit-ETT size was 88% in cuffed group compared to 90% in uncuffed group. A significant positive correlation was reported between the outer diameter of best-fit-ETT and the outer diameter measured by the two ultrasound methods. A lower degree of positive correlation was reported between the inner diameter of best-fit-ETT, and the inner diameter calculated by age-based formulas. Bland Altman's analysis showed agreement between best-fit-ETT outer diameter and epiphyseal diameter of the distal radius in both groups and with transverse cricoid diameter in the cuffed group, with no agreement with age-based formulas in either group.

CONCLUSIONS

Both transverse cricoid diameter and epiphyseal diameter of the distal radius are reliable predictors of the size of best-fit-ETT pediatric endotracheal tube compared to age-based formulas. To save time and effort, we recommend the US measurement of the epiphyseal diameter of distal radius in the preoperative visit and documenting the predicted tube size with the preoperative assessments.

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.

The Effect of the Ultrasonography Measurement Method and the Conventional Measurement Method Used in Endotracheal Tube Size Selection in the Pediatric Patient Group on Postextubation Complications and Patient Recovery

INTRODUCTION

 In this study, we aimed to compare the cuffed intubation tube selected with the Cole formula and tracheal ultrasonography (USG) measurement method regarding postextubation complications in providing airway patency and determine its effects on patient recovery.

MATERIALS AND METHOD

 Between 01 July 2022 and 30 June 2023, American Society of Anesthesiologists (ASA) risk group I-III, 4-6-year-old patients who underwent pediatric orthodontic surgery (multiple tooth extraction) were included in the study. Data of age, gender, weight, ASA risk group, history, Cole formula, USG measurement results used in the endotracheal tube (ETT) selection (one of the two whichever application was used), fasting time, intubation success, operation time, 30th-minute modified Aldrete recovery score (MASS), and postoperative complications due to intubation (within the first postoperative hour) were analyzed retrospectively. The patients were divided into two groups according to the method used by the anesthesiologists in selecting the ETT at the beginning of the operation. The group that used Cole formula management was named I, while the group that used the USG measurement method was called II. Intubation-related complication data of the patients in the first 1 hour postoperatively and MASS values at the 30th minute were compared between the groups.

RESULTS

In this study, 52.5% of the cases were male (n=42), 47.5% were female (n=38), the mean age was 4.84±0.84 years, and the mean body weight was 22.56±7.58 kilogram. There was no statistically significant difference between the groups regarding age, gender, body weight, ASA score, operation time, and period without oral consumption. ETT diameter measurement values according to groups were 4.73±0.46 mm in Group I and 4.41±0.61 mm in Group II. Postoperative 30th-minute MASS values were median 7 in Group I and median 8 in Group II (p<.001). MASS values were significantly higher in the Group II patient group. Intubation-related complications (postoperative cough, stridor, laryngospasm, tachypnea, wheezing, dysphonia) were observed in Group I with a rate of 40% within the first postoperative hour, while complications were marked with a rate of 17.5% in Group II (p=0.026). Complications in group II were significantly lower.

CONCLUSION

 In the pediatric age group, especially under the age of 6, trachea measurement with USG and ETT selection is an effective, safe, and noninvasive method compared to other conventional methods. ETT size selection with USG accelerates postoperative patient recovery and reduces the risk of intubation-related complications. In addition, inflating the tube cuff under USG guidance can prevent cuff-related complications.

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.

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.

Applications of Airway Ultrasound for Endotracheal Intubation in Pediatric Patients: A Systematic Review

Endotracheal intubation is a challenging procedure for pediatric patients. Airway ultrasound as a new technology is suitable for aiding this process, but its diagnostic value remains unclear. We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and the Chinese biomedical literature database to summarize specific applications of airway ultrasound in each step of endotracheal intubation in pediatric patients. Diagnostic accuracy and 95% confidence interval were used as outcomes. In total, 33 studies (6 randomized controlled trials and 27 diagnostic studies) with 1934 airway ultrasound examinations were included. Population included neonates, infants, and older children. Airway ultrasound could be used to determine the endotracheal tube size and confirm endotracheal intubation and intubation depth; the diagnostic accuracy for all these factors was 23.3-100%, 90.6-100%, and 66.7-100%, respectively. Furthermore, the accuracy of airway ultrasound in predicting endotracheal tube size was consistently higher than traditional methods, such as height formula, age formula, and the width of the little finger. In conclusion, airway ultrasound has unique advantages for confirming successful endotracheal intubation in pediatric patients, and it may become an effective auxiliary tool in this field. There is a need to develop a unified airway ultrasound protocol to conduct clinical trials and practice in the future.

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.

Choice of the correct size of endotracheal tube in pediatric patients

Selection and insertion of an endotracheal tube (ETT) of appropriate size for airway management during general anesthesia in pediatric patients is very important. A very small ETT increases the risk of inadequate ventilation, air leakage, and aspiration, whereas a very large ETT may cause serious complications including airway damage, post-intubation croup, and, in severe cases, subglottic stenosis. Although the pediatric larynx is conical, the narrowest part, the rima glottidis, is cylindrical in the anteroposterior dimension, regardless of development, and the cricoid ring is slightly elliptical. A cuffed ETT reduces the number of endotracheal intubation attempts, and if cuff pressure can be maintained within a safe range, the risk of airway damage may not be greater than that of an ETT without cuff. The age-based formula suggested by Cole (age/4 + 4) has long been used to select the appropriate ETT size in children. Because age-based formulas in children are not always accurate, various alternative methods for estimating the ETT size have been examined and suggested. Chest radiography, ultrasound, and a three-dimensional airway model can be used to determine the appropriate ETT size; however, there are several limitations.

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.

Lung and airway ultrasound in pediatric anesthesia

Perioperative lung ultrasound is a continuously evolving modality with numerous applications for the pediatric anesthesiologist. Lung ultrasound can be used at the bedside, including intraoperatively, to augment traditional physical examination methods of assessing cardiopulmonary structures and identifying the presence of specific and clinically significant pathology. With regard to the lungs, ultrasound has been shown to be highly sensitive at identification of pulmonary pathologies, particularly those of interest in the acute care setting (eg, pleural effusion, pneumothorax). With its relative ease of performance, lung ultrasound should be considered in the initial evaluation of intraoperative hypoxemia particularly when traditional modes of evaluation are nonexplanatory. This educational review introduces the basic concepts of lung ultrasound as they relate to pediatric anesthesia patients.

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.

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.

Impact of endotracheal tube size and cuff pressure on tracheal and laryngeal mucosa of adult horses

OBJECTIVE

To assess the effects of two sizes of silicone endotracheal tubes with internal diameter 26 mm (ETT₂₆) and 30 mm (ETT₃₀) inflated to minimum occlusive volume on tracheal and laryngeal mucosa of adult horses anesthetized for 2 hours with isoflurane.

STUDY DESIGN

Prospective, randomized, blinded, crossover experimental study.

ANIMALS

A total of eight healthy adult mares.

METHODS

Upper airway endoscopy and ultrasound measurements of internal tracheal diameter were performed the day before anesthesia. Horses were anesthetized and orotracheally intubated with ETT₂₆ or ETT₃₀. Ease of intubation was scored. The cuff was inflated in 10 mL increments to produce a seal. Final volume of air used and intracuff (IC) pressure (measured by pressure transducer) were recorded. At the end of anesthesia, a manometer was used to measure IC pressure and these measurements compared against measurements from the pressure transducer. Laryngeal and tracheal mucosa were assessed via endoscopy and assigned a score 0-3 before anesthesia, and at 2 and 24 hours following extubation.

RESULTS

Data are from seven horses because one horse with laryngeal hemiplegia was excluded. Mean tracheal ultrasound measurement was 3.5 ± 0.4 cm. No significant differences were noted between endotracheal tube sizes for intubation score, IC pressures, inflation volumes or tracheal or laryngeal injury scores at any time point. IC pressure measured by manometer was slightly higher than that by transducer (+1.0 ± 2.8 mmHg).

CONCLUSIONS AND CLINICAL RELEVANCE

Results identified no clear advantage of one endotracheal tube size over the other in the population of horses studied, when endotracheal intubation is properly applied and IC pressure is carefully monitored. However, given that ETT₂₆ was associated with the highest observed IC pressures and the only observed incidents of tracheal circumferential erythema, the larger ETT₃₀ may be the better choice in most cases where tracheal size is sufficient.

Bedside Ultrasound for Procedural Assistance in Pediatrics

Point-of-care ultrasound (POCUS) is a noninvasive imaging tool with both diagnostic and therapeutic applications. In this article, the author will review the role of POCUS for vascular access, endotracheal intubation, lumbar puncture, chest tube, and diagnosing coronavirus disease 2019 lung pathology. This will include a review of the evidence, technique, and strategies for optimizing performance of these procedures. [Pediatr Ann. 2021;50(10):e404-e410.].

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.

Comparison of Endoscopic and Ultrasonographic Measurements of the Subglottic Airway in Children

OBJECTIVE

To compare measurements of the pediatric subglottis obtained by surgeon-performed ultrasound and endoscopy.

STUDY DESIGN

Prospective observational comparison-of-methods study.

SETTING

Tertiary care pediatric hospital.

SUBJECTS AND METHODS

Thirty-one patients who underwent direct laryngoscopy from May 2017 to July 2018 were recruited. Transcervical ultrasound was used to visualize the vocal folds, subglottis, and cervical trachea. The anterior-posterior (AP) and transverse (TV) diameter of the subglottic space were measured endoscopically and via ultrasound by 2 independent evaluators. Measurements were compared for correlation, bias, and agreement. A clinically acceptable bias for subglottic diameter was assumed to be 0.5 mm or less.

RESULTS

The median age of enrolled patients was 2.6 years (range, 4 months-13.3 years). Endoscopic subglottic AP and TV measurements ranged from 3.33 mm to 14.81 mm and from 4.44 mm to 11.65 mm, respectively, while ultrasonographic AP and TV measurements ranged from 4.57 mm to 9.85 mm and from 3.77 mm to 8.96 mm. Pearson coefficient showed strong a correlation for both endoscopic and ultrasound AP (R = 0.8081, P < .0001) and TV (R = 0.8796, P < .001) measurements of the subglottis. Bland-Altman plots revealed a bias (average discrepancy) for AP measurements of 0.22 mm and 0.11 mm for TV measurements.

CONCLUSION

Endoscopic and ultrasonography measurements of the pediatric subglottic airway were strongly correlated. The discrepancy between AP and TV measurements was less than 0.5 mm. Ultrasound of the subglottis may be an alternative to endoscopic assessment of the airway for measurement of the subglottic airway in children in select cases.

Point-of-care ultrasound in pediatric anesthesia: perioperative considerations

PURPOSE OF REVIEW

To review the perioperative applications of point-of-care ultrasound (POCUS).

RECENT FINDINGS

The role of point-of-care ultrasonography for perioperative care is expanding with respect to perioperative application. The imaging approach can complement the physical exam and provide additional information for decision-making in pediatric perioperative medicine. This review will focus on applications in the following organ systems: airway, cardiac, pulmonary and gastric. Specifically, POCUS of the airway has been used to optimize endotracheal tube depth, aid in tube size selection and predict difficulty with laryngoscopy and intubation. Lung POCUS has been used to assess for causes hypoxemia as well as to optimize ventilatory mechanics. Cardiac POCUS has been used for assessment of hemodynamics, valvular and ventricular function. Gastric ultrasound has emerged as an evaluative mechanism of gastric content in the setting of fasting as well as to confirm placement of gastric tubes. The applications of POCUS in the perioperative setting continue to evolve as a reliable diagnostic tool that can assist in timely diagnosis, improve procedural safety and has the potential to improve patient outcomes.

SUMMARY

The utility of perioperative POCUS has been well demonstrated, specifically for examination of the airway, stomach and cardiopulmonary system. It is advisable for the novice sonographer to perform POCUS within the guidelines set by the American Society of Echocardiography regarding basic POCUS. As with all diagnostic modalities, understanding the limitations of ultrasound and POCUS as well as continuous self-assessment is crucial.

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.

The development of the cricoid cartilage and its implications for the use of endotracheal tubes in the pediatric population

BACKGROUND

The rigid cricoid cartilage is functionally the narrowest portion of the larynx. There is some controversy over the shape of the pediatric cricoid cartilage in the transverse plane. It is important to understand the development of the cricoid cartilage so that endo-traceheal tubes can be used more safely.

AIM

To determine changes in the internal diameter and shape of the cricoid cartilage during development and explore the implications of those changes for the selection of ETT type and size for children.

METHODS

The cervical computed tomography scans were reviewed in patients aged 1-20 years. After performing the multiplanar reconstruction and correcting the slant, the transverse and anteroposterior internal diameters of the inlet and outlet of the cricoid cartilage were measured, respectively. The angle between the arch and the lamina of the cricoid cartilage in the middle sagittal plane was measured. The ratios of transverse to anteroposterior diameter for the inlet and outlet of the cricoid cartilage were calculated, respectively.

RESULTS

In females, the internal diameters of the cricoid cartilage increased linearly with age. In males, the internal diameters of the cricoid cartilage exhibited a growth spurt during adolescence. The transverse diameter of the inlet was the smallest diameter of the cricoid cartilage, and the predicting formula of the transverse diameter of the inlet for children aged 1-12 was 0.4 × age (year) + 5.1, R²  = .758. The angle between the arch and lamina of the cricoid cartilage and the ratios of transverse to anteroposterior diameter correlated weakly with age.

CONCLUSION

The transverse inner diameter of the inlet is the smallest diameter of the cricoid cartilage. The "funnel shape" of the cricoid cartilage remains unchanged during development. The outer diameter should be considered when selecting an endotracheal tube.

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.

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.

Subglottal resonances of American English speaking children

This paper presents an investigation of children's subglottal resonances (SGRs), the natural frequencies of the tracheo-bronchial acoustic system. A total of 43 children (31 male, 12 female) aged between 6 and 18 yr were recorded. Both microphone signals of various consonant-vowel-consonant words and subglottal accelerometer signals of the sustained vowel /ɑ/ were recorded for each of the children, along with age and standing height. The first three SGRs of each child were measured from the sustained vowel subglottal accelerometer signals. A model relating SGRs to standing height was developed based on the quarter-wavelength resonator model, previously developed for adult SGRs and heights. Based on difficulties in predicting the higher SGR values for the younger children, the model of the third SGR was refined to account for frequency-dependent acoustic lengths of the tracheo-bronchial system. This updated model more accurately estimates both adult and child SGRs based on their heights. These results indicate the importance of considering frequency-dependent acoustic lengths of the subglottal system.

Perioperative ultrasound-assisted clinical evaluation - A case based review

Ultrasound is increasingly being adopted into anaesthesia and intensive care practice. The range of ultrasound examination has also increased from transoesophageal echocardiography in cardiac surgery and ultrasound-guided nerve blocks and vascular access, to examination of the heart, lungs, abdomen and deep veins. Typically, the use of ultrasound is focused or basic, designed to be performed by the anaesthetist at the patient's bedside in real time to answer clinical questions and to direct therapy. Ultrasound is not performed in isolation, but used to complement clinical evaluation, and accordingly can be considered as 'ultrasound-assisted perioperative evaluation'. Whilst there is good evidence that ultrasound improves diagnostic accuracy and in turn alters management, there are few data examining whether ultrasound leads to improved clinical outcomes. This review will examine multiple uses of perioperative ultrasound with case studies to illustrate potential utility.

Selection of cuffed endotracheal tube for children with congenital heart disease based on an ultrasound-based linear regression formula

It remains to be discovered whether a formula predicting the subglottic transverse diameter measured by ultrasound (SGD_formula) for the selection of an appropriate endotracheal tube (ETT) for children without congenital heart disease (CHD) is useful for children with CHD. A formula for predicting SGD was established after assessing 60 children ≤ 8 years without CHD and validated on 60 children with CHD. We selected the cuffed ETT size based on the SGD by ultrasound (SGD_ultra). Subsequently, the fit of the ETT cuff in 60 children with CHD was examined via air-leak test. The maximum allowed difference between the SGD_formula and the ETT size that fit was 0.2 mm. The agreement among and accuracy of SGD_ultra, SGD_formula, and the ETT used in children was analyzed. For children without CHD, we adopted a linear formula, given by SGD_formula (mm) = 0.4 × age + 5.3. For children with CHD, allometric formula was adopted, given by SGD_formula (mm) = 5.4 × age^0.18. A stronger agreement exists between SGD_ultra and ETT size compared to that between SGD_formula and ETT size. And the mean bias (SGD_formula-ETT size and SGD_ultra-ETT size) was 0.21 mm (95% confidence interval, - 0.59 to 1.01 mm) and 0.00 mm (- 0.79 to 0.84 mm). For the CHD group, the ultrasound-based method yielded a 78% success rate of ETT size choice, while the formula-based method permitted an appropriate ETT size in only 32% of subjects (P < 0.001). Our analysis showed that measuring the SGD_ultra was more accurate in predicting the correct OD of the ETT in children with CHD undergoing cardiovascular surgery, based on the correlation and agreement with ETT OD.

Body Surface Area Is Not a Reliable Predictor of Tracheal Tube Size in Children

Objectives

The age-based Cole formula has been employed for the estimation of endotracheal tube (ETT) size due to its ease of use, but may not appropriately consider growth rates among children. Child growth is assessed by calculating the body surface area (BSA). The association between the outer diameter of an appropriate uncuffed-endotrachealtube (ETT-OD) and the BSA values of patients at 24–96 months of age was our primary outcome.

Methods

Cole formula, BSA, age, height, weight and ultrasound measurement of subglottic-transverse-diameter were evaluated for correlations with correct uncuffed ETT-OD. The Cole formula, BSA, and ultrasound measurements were analyzed for estimation rates in all patients and age subgroups. The maximum allowed error for the estimation of ETT-OD was ≤0.3 mm. Patients’ tracheas were intubated with tubes chosen by Cole formula and correct ETT-OD values were determined using leak test. ETT exchange rates were recorded.

Results

One-hundred twenty-seven patients were analyzed for the determination of estimation rates. Thirteen patients aged ≥72 months were intubated with cuffed ETT-OD of 8.4 mm and were accepted to need uncuffed ETT-OD >8.4 mm in order to be included in estimation rates, but excluded from correlations for size analysis. One-hundred fourteen patients were analyzed for correlations between correct ETT-OD (determined by the leak test) and outcome parameters. Cole formula, ultrasonography, and BSA had similar correct estimation rates. All three parameters had higher underestimation rates as age increased.

Conclusion.

The Cole formula, BSA, and ultrasonography had similar estimation rates in patients aged ≥24 to ≤96 months. BSA had a correct estimation rate of 40.2% and may not be reliable in clinical practice to predict uncuffedETT-size.

Selecting an Appropriate Cuffed Endotracheal Tube Using Ultrasound of the Cricoid in a Child with Down Syndrome

A 7-year-old girl (height, 94 cm; weight, 15.1 kg) with Down syndrome was scheduled for right patellar dislocation repositioning. The ultrasonographically measured internal transverse width of the cricoid before intubation was 7.8 mm. Attempted insertion of a cuffed Mallinckrodt® endotracheal tube (ETT) (internal diameter, 5.0 mm; deflated cuff portion, 8.4 mm diameter) failed. In contrast, the insertion of a cuffed Microcuff® ETT (5.0 mm ID; deflated cuff portion, 7.3 mm diameter) was successful. Thicker folds in the deflated cuff of the Mallinckrodt ETT could have hindered passage through the vocal cord, including the cricoid region. It is becoming standard to use the ultrasonographically measured internal width of the cricoid when choosing cuffed paediatric ETTs, and this approach may be suitable for patients with Down syndrome as well. In these children, approximately 20% of uncuffed ETTs inserted were one or two sizes smaller in diameter than those predicted for the same age. We may choose the ETT size in reference to an ultrasonographically obtained internal transverse width of the cricoid, stated outer diameter (OD) by the producer, and the actual OD depending on the cuff bulk instead of a tube size calculation in patients with growth retardation.

Pediatric Patients with High Pulmonary Arterial Pressure in Congenital Heart Disease Have Increased Tracheal Diameters Measured by Computed Tomography

OBJECTIVES

Determination of the appropriate tracheal tube size using formulas based on age or height often is inaccurate in pediatric patients with congenital heart disease (CHD), particularly in those with high pulmonary arterial pressure (PAP). Here, the authors compared tracheal diameters between pediatric patients with CHD with high PAP and low PAP.

DESIGN

Retrospective clinical study.

SETTING

Hospital.

PARTICIPANTS

Pediatric patients, from birth to 6 months of age, requiring general anesthesia and tracheal intubation who underwent computed tomography were included. Patients with mean pulmonary artery pressure >25 mmHg were allocated to the high PAP group, and the remaining patients were allocated to the low PAP group. The primary outcome was the tracheal diameter at the cricoid cartilage level, and the secondary goal was to observe whether the size of the tracheal tube was appropriate compared with that obtained using predictable formulas based on age or height.

MEASUREMENTS AND MAIN RESULTS

The mean tracheal diameter was significantly larger in the high PAP group than in the low PAP group (p < 0.01). Pediatric patients with high PAP required a larger tracheal tube size than predicted by formulas based on age or height (p = 0.04 for age and height).

CONCLUSIONS

Pediatric patients with high PAP had larger tracheal diameters than those with low PAP and required larger tracheal tubes compared with the size predicted using formulas based on age or height.

Point-of-care ultrasound in pediatric anesthesiology and critical care medicine

Ultrasound has increasingly become a clinical asset in the hands of the anesthesiologist and intensivist who cares for children. Though many applications for ultrasound parallel adult modalities, children as always are not simply small adults and benefit from the application of ultrasound to their management in various ways. Body composition and size are important factors that affect ultrasound performance in the child, as are the pathologies that may uniquely afflict children and aspects of procedures unique to this patient population. Ultrasound simplifies vascular access and other procedures by visualizing structures smaller than those in adults. Maturation of the thoracic cage presents challenges for the clinician performing pulmonary ultrasound though a greater proportion of the thorax can be seen. Moreover, ultrasound may provide unique solutions to sizing the airway and assessing it for cricothyroidotomy. Though cardiac ultrasound and neurosonology have historically been performed by well-developed diagnostic imaging services, emerging literature stresses the utility of clinician ultrasound in screening for pathology and providing serial observations for monitoring clinical status. Use of ultrasound is growing in clinical areas where time and diagnostic accuracy are crucial. Implementation of ultrasound at the bedside will require institutional support of education and credentialing. It is only natural that the pediatric anesthesiologist and intensivist will lead the incorporation of ultrasound in the future practice of these specialties.

Point-of-care ultrasound (POCUS) of the upper airway

Airway management is a critical skill in the practice of several medical specialities including anesthesia, emergency medicine, and critical care. Over the years mounting evidence has showed an increasing role of ultrasound (US) in airway management. The objective of this narrative review is to provide an overview of the indications for point-of-care ultrasound (POCUS) of the upper airway. The use of US to guide and assist clinical airway management has potential benefits for both provider and patient. Ultrasound can be utilized to determine airway size and predict the appropriate diameter of single-lumen endotracheal tubes (ETTs), double-lumen ETTs, and tracheostomy tubes. Ultrasonography can differentiate tracheal, esophageal, and endobronchial intubation. Ultrasonography of the neck can accurately localize the cricothyroid membrane for emergency airway access and similarly identify tracheal rings for US-guided tracheostomy. In addition, US can identify vocal cord dysfunction and pathology before induction of anesthesia. A rapidly growing body of evidence showing ultrasonography used in conjunction with hands-on management of the airway may benefit patient care. Increasing awareness and use of POCUS for many indications have resulted in technologic advancements and increased accessibility and portability. Upper airway POCUS has the potential to become the first-line non-invasive adjunct assessment tool in airway management.

Inter-rater and intra-rater reliability of the airway diameter measured by sonography

INTRODUCTION

Sonography has gained a broad field of applications in current anesthetic practice. During airway management, it could have an important role, because it allows real-time measurement of anatomical aspects and a functional evaluation with high safety profile. However, assessment of the reliability and precision of these measurements is critical if sonography is used as a clinical diagnostic tool. The aim of the study was to estimate inter-rater and intra-rater reliability of the airway diameter measured by sonography in heathy volunteers.

METHODS

We conducted a cross-sectional study during 2015 on healthy adult volunteers. Using sonography, transverse internal diameter of subglottic space was measured twice by two blinded sonographers.

RESULTS

Agreement was classified as very good for intra-rater measurements (ICC = 0.84) and good for the inter-rater measurements (ICC = 0.71). The 95% CI of agreement limits for the intra-rater measurements were inferior to those for the inter-rater measurements.

CONCLUSIONS

Ultrasound measurement is a reliable and precise method to measure the internal subglottic diameter of the airway. Ultimately, this method may provide clinicians valuable information regarding airway diameter in adults and may help to guide treatment options.

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.

The role of ultrasound in appropriate endotracheal tube size selection in pediatric patients

BACKGROUND

The aim of this prospective study was to investigate the success of ultrasound in pediatric patients in determining the appropriate sized cuffed endotracheal tube and to compare the results with conventional height-based (Broselow) tape and age-based formula tube size.

METHODS

One hundred and fifty-two children of 1-10 years of age, who received general anesthesia for adenotonsillectomy were enrolled to the study. In all participants, the transverse diameter of the subglottis was measured with ultrasound during apnea. An endotracheal tube was chosen with the outer diameter matched to the measured subglottic airway diameter. An age-based (Motoyama-Khine) and height-based (Broselow) endotracheal tube size was calculated. If there was resistance to passage of the tube into the trachea or an airway pressure >25 cmH₂ 0 was required to detect an audible leak, the endotracheal tube was replaced with internal diameter of 0.5 mm smaller. If there was an audible leak at airway pressure <10 cmH₂ O, or peak pressure >25 cmH₂ 0 or a cuff pressure > 25 cmH₂ O was required to seal, the tube was changed to the 0.5 mm larger internal diameter. Best-fit tube internal diameter was the resultant tube internal diameter that met the previously stated conditions. The need for endotracheal tube replacement and peak airway pressure were recorded.

RESULTS

The internal diameter of ultrasound determined tube was the same as best-fit tube in 88% of children. Endotracheal tube was replaced in 15 patients with a one size larger, and in three patients with one size smaller tube. Using Bland-Altman analysis, a better agreement was observed with ultrasound measurement rather than height-based estimation and age-based formulas.

CONCLUSION

Our findings show that subglottic diameter measured by ultrasound appears to be a reliable predictor for the assessment of the subglottic diameter of the airway in estimating appropriate size pediatric endotracheal tube.

A smartphone application to determine body length for body weight estimation in children: a prospective clinical trial

The aim of this study was to test the feasibility and accuracy of a smartphone application to measure the body length of children using the integrated camera and to evaluate the subsequent weight estimates. A prospective clinical trial of children aged 0-<13 years admitted to the emergency department of the University Children's Hospital Zurich. The primary outcome was to validate the length measurement by the smartphone application «Optisizer». The secondary outcome was to correlate the virtually calculated ordinal categories based on the length measured by the app to the categories based on the real length. The third and independent outcome was the comparison of the different weight estimations by physicians, nurses, parents and the app. For all 627 children, the Bland Altman analysis showed a bias of -0.1% (95% CI -0.3-0.2%) comparing real length and length measured by the app. Ordinal categories of real length were in excellent agreement with categories virtually calculated based upon app length (kappa = 0.83, 95% CI 0.79-0.86). Children's real weight was underestimated by physicians (-3.3, 95% CI -4.4 to -2.2%, p < 0.001), nurses (-2.6, 95% CI -3.8 to -1.5%, p < 0.001) and parents (-1.3, 95% CI -1.9 to -0.6%, p < 0.001) but overestimated by categories based upon app length (1.6, 95% CI 0.3-2.8%, p = 0.02) and categories based upon real length (2.3, 95% CI 1.1-3.5%, p < 0.001). Absolute weight differences were lowest, if estimated by the parents (5.4, 95% CI 4.9-5.9%, p < 0.001). This study showed the accuracy of length measurement of children by a smartphone application: body length determined by the smartphone application is in good agreement with the real patient length. Ordinal length categories derived from app-measured length are in excellent agreement with the ordinal length categories based upon the real patient length. The body weight estimations based upon length corresponded to known data and limitations. Precision of body weight estimations by paediatric physicians and nurses were comparable and not different to length based estimations. In this non-emergency setting, parental weight estimation was significantly better than all other means of estimation (paediatric physicians and nurses, length based estimations) in terms of precision and absolute difference.

Ultrasonographic Measurement of Subglottic Diameter for Paediatric Cuffed Endotracheal Tube Size Selection: Feasibility Report

OBJECTIVE

The aim of this feasibility study was to investigate the first attempt success of ultrasonography (USG) in paediatric patients in predicting an appropriate cuffed endotracheal tube (ETT) size.

METHODS

Fifty children who were 1-10 years of age and who received general anaesthesia with endotracheal intubation for adenoidectomy or adenotonsillectomy were enrolled in the study. In all participants, the transverse diameter of the subglottic airway was measured with USG at the cricoid level without ventilation. The outer diameter (OD) of the maximum allowable ETT was chosen according to the measured subglottic airway diameter. In the presence of resistance to passage of the tube into the trachea or in the absence of an audible leak at airway pressure of >25 cm H₂O, the ETT was replaced with a tube whose internal diameter (ID) was 0.5 mm smaller. If a leak was audible at airway pressures of <10 cm H₂O, if a seal could not be achieved with a cuff pressure of >25 cm H₂O or if a peak airway pressure of >25 cm H₂O was observed during ventilation, the tube was changed to a tube one size larger. The OD of the best-fit ETT was converted to the ID. The best-fit ID, the requirement for ETT replacement, the duration of airway diameter measurement by USG and the peak airway pressure were recorded.

RESULTS

The success rate of the first attempt with USG was 86%; the ETT was replaced in five patients with a tube one size larger and in two patients with a tube one size smaller.

CONCLUSION

Our findings show the subglottic diameter measured by USG to be a reliable predictor in estimating the appropriate paediatric ETT size.

Role of upper airway ultrasound in airway management

Upper airway ultrasound is a valuable, non-invasive, simple, and portable point of care ultrasound (POCUS) for evaluation of airway management even in anatomy distorted by pathology or trauma. Ultrasound enables us to identify important sonoanatomy of the upper airway such as thyroid cartilage, epiglottis, cricoid cartilage, cricothyroid membrane, tracheal cartilages, and esophagus. Understanding this applied sonoanatomy facilitates clinician to use ultrasound in assessment of airway anatomy for difficult intubation, ETT and LMA placement and depth, assessment of airway size, ultrasound-guided invasive procedures such as percutaneous needle cricothyroidotomy and tracheostomy, prediction of postextubation stridor and left double-lumen bronchial tube size, and detecting upper airway pathologies. Widespread POCUS awareness, better technological advancements, portability, and availability of ultrasound in most critical areas facilitate upper airway ultrasound to become the potential first-line non-invasive airway assessment tool in the future.

The Role of Airway and Endobronchial Ultrasound in Perioperative Medicine

Recent years have witnessed an increased use of ultrasound in evaluation of the airway and the lower parts of the respiratory system. Ultrasound examination is fast and reliable and can be performed at the bedside and does not carry the risk of exposure to ionizing radiation. Apart from use in diagnostics it may also provide safe guidance for invasive and semi-invasive procedures. Ultrasound examination of the oral cavity structures, epiglottis, vocal cords, and subglottic space may help in the prediction of difficult intubation. Preoperative ultrasound may diagnose vocal cord palsy or deviation or stenosis of the trachea. Ultrasonography can also be used for confirmation of endotracheal tube, double-lumen tube, or laryngeal mask placement. This can be achieved by direct examination of the tube inside the trachea or by indirect methods evaluating lung movements. Postoperative airway ultrasound may reveal laryngeal pathology or subglottic oedema. Conventional ultrasound is a reliable real-time navigational tool for emergency cricothyrotomy or percutaneous dilational tracheostomy. Endobronchial ultrasound is a combination of bronchoscopy and ultrasonography and is used for preoperative examination of lung cancer and solitary pulmonary nodules. The method is also useful for real-time navigated biopsies of such pathological structures.

[The influence of airway supporting maneuvers on glottis view in pediatric fiberoptic bronchoscopy]

INTRODUCTION

Flexible fiber optic bronchoscopy is a valuable intervention for evaluation and management of respiratory diseases in both infants, pediatric and adult patients. The aim of this study is to investigate the influence of the airway supporting maneuvers on glottis view during pediatric flexible fiberoptic bronchoscopy.

MATERIALS AND METHODS

In this randomized, controlled, crossover study; patients aged between 0 and 15 years who underwent flexible fiberoptic bronchoscopy procedure having American Society of Anesthesiologists I-II risk score were included. Patients having risk of difficult intubation, intubated or patients with tracheostomy, and patients with reduced neck mobility or having cautions for neck mobility were excluded from this study. After obtaining best glottic view at the neutral position, patients were positioned jaw trust with open mouth, jaw trust with teeth prottution, head tilt chin lift and triple airway maneuvers and best glottis scores were recorded.

RESULTS

Total of 121 pediatric patients, 57 girls and 64 boys, were included in this study. Both jaw trust with open mouth and jaw trust with teeth prottution maneuvers improved the glottis view compared with neutral position (p<0.05), but we did not observe any difference between jaw trust with open mouth and jaw trust with teeth prottution maneuvers (p>0.05). Head tilt chin lift and triple airway maneuvers improved glottis view when compared with both jaw trust with open mouth and jaw trust with teeth prottution maneuvers and neutral position (p<0.05); however we found no differences between head tilt chin lift and triple airway maneuvers (p>0.05).

CONCLUSION

All airway supporting maneuvers improved glottic view during pediatric flexible fiberoptic bronchoscopy; however head tilt chin lift and triple airway maneuvers were found to be the most effective maneuvers.