The anatomy of the pediatric airway: Has our knowledge changed in 120 years? A review of historic and recent investigations of the anatomy of the pediatric larynx

Cuffed versus uncuffed endotracheal tubes in neonates undergoing noncardiac surgeries: A randomized controlled trial

BACKGROUND

The efficacy and safety of cuffed endotracheal tubes (ETTs) in neonates are still unclear, this study aimed to assess the efficacy of cuffed versus uncuffed ETTs in neonate undergoing noncardiac surgeries.

METHODS

Neonates scheduled for noncardiac surgeries were randomized into two groups according to the type of airway device during general anesthesia: cuffed ETT group (n = 60) and the uncuffed ETT group (n = 60). The primary outcome was the incidence of ETT exchange to find the appropriate ETT. Other outcomes included: duration of intubation, lung ultrasound score, and incidence of postoperative complications (croup, wheezes, hypoxia, etc.).

RESULTS

The frequency of ETT exchange was lower in the cuffed ETT group compared to the uncuffed one {1 (1.7%) vs. 28 (46.7%), p = .0001; relative risk [95% confidence interval]: 0.54 [0.43-0.69]}. Postoperative adverse events were comparable between both groups except for significantly higher post extubation croup in the uncuffed ETT group compared to the cuffed ETT {10 (16.7%) vs. 3(5%), p value = .04, relative risk (95% confidence interval): 1.14 (1-1.29)}.

CONCLUSION

In full term neonates undergoing noncardiac surgeries, the use of cuffed ETT was associated with less need to tracheal tube exchange and less incidence of postoperative croup, without increasing the postoperative respiratory complications compared to uncuffed ETT.

Randomized controlled trial to evaluate the rate of successful neonatal endotracheal intubation performed with a stylet versus without a stylet

INTRODUCTION

Neonates in intensive care units often require endotracheal intubation and mechanical ventilation. During this intubation procedure, a stylet is frequently used along with an endotracheal tube. Despite the widespread use of a stylet, it is still not known whether its use increases the intubation success rate. This study examined the association between stylet use and the intubation success rate in surgical neonates.

METHODOLOGY

This single-center study was conducted between December 2021 and December 2022 in the Neonatal surgical intensive care unit of a tertiary care center in Northern India. Infants were randomized to have the endotracheal intubation procedure performed using either an endotracheal tube alone or with a stylet. The primary outcome of the study was to assess the successful first-attempt neonatal endotracheal intubation rate with and without using a stylet. Apart from the rate of successful intubation, the duration of the intubation and complications during the intubation procedures as measured by bradycardia, desaturation episodes, and local trauma were also recorded. Both groups were thus compared on above mentioned outcomes.

RESULTS

The total number of neonates enrolled were 200, and the overall success rate (81% in the stylet group vs. 73% in the non-stylet group) was not statistically significant. Intubation time was however less, when stylet was used (16.2 ± 4.3 vs. 17.5 ± 5.0 s, p = .046). When the endotracheal tube size was 3 or less, the success rate was substantially higher in the stylet group (80%) than the non-stylet group (63%), p = .03. No statistical difference was recorded for bleeding and local trauma, though the esophageal intubation rate was higher when intubation was attempted without the stylet.

CONCLUSION

Endotracheal intubation using a stylet did not significantly improve the success rate of the procedure, however, intubation time significantly varied between groups and in different conditions. The rigidity and curvature provided by the stylet may facilitate the process of intubation when smaller caliber endotracheal tubes are used.

[Characteristics of the fetal and infant respiratory system : What the pediatric anesthetist should know]

Respiratory complications are the most frequent incidents in pediatric anesthesia after cardiac events. The pediatric respiratory physiology and airway anatomy are responsible for the particular respiratory vulnerability in this stage of life. This article explains the aspects of pulmonary embryogenesis relevant for anesthesia and their impact on the respiration of preterm infants and neonates. The respiratory distress syndrome and bronchopulmonary dysplasia are highlighted as well as the predisposition to apnea of preterm infants and neonates. Due to the anatomical characteristics, the low size ratios and the significantly shorter apnea tolerance, airway management in children frequently represents a challenge. This article gives useful assistance and provides an overview of formulas for calculating the appropriate tube size and depth of insertion. Finally, the pathophysiology and adequate treatment of laryngospasm are explained.

Comparison of four different techniques of i-gel insertion by anaesthesia trainees in children undergoing daycare surgery: A single-blind, randomised, comparative study

Background and Aims

Different techniques of i-gel insertion have been described with variable success rates. This study aimed to assess the incidence of malposition of i-gel in children with 90° rotation, 180° rotation, jaw thrust-assisted and standard insertion techniques.

Methods

The study included 132 children undergoing elective surgery under general anaesthesia without neuromuscular blockade after approval from the Institutional Ethics Committee. The i-gel was inserted using one of the four randomised techniques (90° rotation, 180° rotation, jaw thrust-assisted insertion or standard insertion technique) by anaesthesia trainees. The primary objective of this study was to assess device malposition using three alternative techniques compared to the standard insertion technique by flexible video bronchoscopy.

Results

The incidence of malposition was the least in the 180° rotation technique group (27%) versus 39% in the standard and 90° rotation technique groups and 70% in the jaw thrust technique group (P = 0.004). Oropharyngeal leak pressure (OLP) was highest in the 180° rotation technique group, that is, 27.1 (5.3) cm H2O in the 180° rotation technique group versus 23 (4.3), 25.8 (4.1) and 24.7 (5.6) cm H2O in the standard, 90° rotation and assisted jaw thrust groups, respectively (P = 0.006). The time to i-gel insertion was the least with the standard insertion technique, that is, 16.9 (3.3) s, compared to 18.4 (3.1) s in the 90° rotation group, 19.5 (3.2) s in the180° rotation group and 20.1 (3.4) s in the assisted jaw thrust technique group (P < 0.001).

Conclusion

The 180° rotation technique for i-gel placement in children by anaesthesia trainees has the lowest incidence of malposition and the best OLP versus other techniques but lacks any clear advantage in clinical performance and ventilation.

The neonatal airway

Safe and effective management of the neonatal airway requires knowledge, teamwork, preparation and experience. At baseline, the neonatal airway can present significant challenges to experienced neonatologists and paediatric anaesthesiologists, and increased difficulty can be due to anatomical abnormalities, physiological instability or increased situational stress. Neonatal airway obstruction is under recognised, and should be considered an emergency until the diagnosis and physiological implications are understood. When multiple types of difficulties are present or there are multiple levels of anatomical obstruction, the challenge increases exponentially. In these situations, preparation, multi-disciplinary teamwork and a consistent hospital-wide approach will help to reduce errors and morbidity.

Development and Disorders of the Airway in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), a disorder characterized by arrested lung development, is a frequent cause of morbidity and mortality in premature infants. Parenchymal lung changes in BPD are relatively well-characterized and highly studied; however, there has been less emphasis placed on the role that airways disease plays in the pathophysiology of BPD. In preterm infants born between 22 and 32 weeks gestation, the conducting airways are fully formed but still immature and therefore susceptible to injury and further disruption of development. The arrest of maturation results in more compliant airways that are more susceptible to deformation and damage. Consequently, neonates with BPD are prone to developing airway pathology, particularly for patients who require intubation and positive-pressure ventilation. Airway pathology, which can be divided into large and small airways disease, results in increased respiratory morbidity in neonates with chronic lung disease of prematurity.

Anatomical investigations on the upper airway in premature and newborn babies

Safe intubation of newborns remains a challenge. This investigates the upper airway anatomy of (pre-)term infants was investigated to improve airway management and the development of airway devices. Angles and diameters of both oral and nasal intubation pathways of 22 cadavers of premature and term stillborn infants were measured, relative to their gestational age (GA) and tested for statistical significance. The systematic influence of sex on the distribution of values was examined. Cast models of the oral and nasal intubation pathway were (produced using a silicone dental impression material) 3D-scanned. No significant correlation with GA was seen in the angles studied. However, four distances around the hard and soft palate did show statistically significant positive correlations with GA. Regarding differences between the sexes, only the angle between the entrance of the trachea and the esophagus was greater for male cadavers. The angles of the ventilation pathway of (pre-)term infants do not depend systematically on GA. Anatomically, laryngeal masks might therefore also be well-suited ventilators for preterm infants. Alterations in the size but not the shape of laryngeal masks for small preterm infants is recommended. The data obtained may thus be used as a basis for the development of airway devices and airway simulators for medical education and clinical training.

Plain Radiographic Analysis of Laryngeal Dimensions in Young Children: Normal versus Croup

(1) Background: Contrary to a tenet of the funnel-shaped pediatric larynx with the cricoid level being narrowest, recent studies show the glottis and subglottis as the narrowest levels. To locate the functionally narrowest level of the larynx, we reported normal laryngeal dimensions and their croup-related changes in young children. (2) Methods: We reviewed normal plain neck radiographs recorded for the evaluation of minor trauma or foreign bodies in 504 children aged ≤4 years who visited the emergency department from 2016 through 2021. Using computed tomography-based localization of the glottis, we radiographically defined the subglottis and cricoid. At these levels, we measured diameters and calculated cross-sectional areas (CSAs) on the radiographs. The values were compared to the equivalent values of a 1:1 age-matched population with croup. (3) Results: In the study population (n = 401), the narrowest diameter and CSA were observed in the glottis. In detail, the mean anteroposterior/transverse diameters were 9.8/3.4 mm at the glottis, 8.5/5.6 mm at the subglottis, and 7.4/6.8 mm at the cricoid (p < 0.001), respectively. In the same order, the mean CSAs were 26.5, 38.1, and 40.5 mm2 (p < 0.001). All dimensions were narrower in the croup population (p < 0.001). We found croup-related narrowing, namely reductions in the transverse diameter and CSA that were more severe closer to the glottis (p < 0.001), without differences per level in the anteroposterior diameter. (4) Conclusions: This study confirms the glottis as the narrowest level of the larynx in young children. In addition, level-based differences in croup-related narrowing suggest some point between the glottis and subglottis as the functionally narrowest level.

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.

Spatial aerosol deposition correlated to anatomic feature development in 6-year-old upper airway computational models

The upper airways of children undergo developmental changes around age 6, yielding differences between adult and pediatric anatomies. These differences include the cricoid ring area shape, the location of narrowest constriction, and the angle of the epiglottis, all of which are expected to alter local fluid dynamic profiles and subsequent upper airway deposition and downstream aerosol delivery of inhaled therapeutics. In this work, we quantify "pediatric"-like and "adult"-like geometric and fluid dynamic features of two computed tomography (CT)-scan derived models of 6-year-old upper airways in healthy subjects and compare to an idealized model. The two CT-scan models had a mixture of "adult"- and "pediatric"-like anatomic features, with Subject B exhibiting more "pediatric"-like features than Subject A, while the idealized model exhibited entirely "adult"-like features. By computational fluid-particle dynamics, these differences in anatomical features yielded distinct local fluid profiles with altered aerosol deposition between models. Notably, the idealized model better predicted deposition characteristics of Subject A, the more "adult"-like model, including the relationship between the impaction parameter, dp2Q and the fraction of deposition across a range of flow rates and particle diameters, as well as deposition of an approximate pharmaceutical particle size distribution model. Our results with even this limited dataset suggest that there are key personalized metrics that are influenced by anatomical development, which should be considered when developing pediatric inhalable therapeutics. Quantifying anatomical development and correlating to aerosol deposition has the potential for high-throughput developmental characterization and informing desired aerosol characteristics for pediatric applications.

Child requiring tracheostomy for removal of an airway foreign body at the tracheal bifurcation

Airway foreign bodies are typically removed orally using a rigid bronchoscope. We present a rare case of a foreign body at the tracheal bifurcation that required removal via tracheostomy. A child turned pale while eating nuts and was suspected to have choked on a foreign body. CT revealed a foreign body at the tracheal bifurcation. As his respiratory condition was unstable, tracheal intubation and removal were attempted using a rigid bronchoscope. Tracheal obstruction during oral removal resulted in respiratory failure and bradycardia. Following emergency tracheostomy, the foreign body was removed via the tracheal stoma after his respiratory condition stabilised. The patient was discharged 21 days later without neurological sequelae. To avoid hypoxaemia during airway foreign body removal, as in this case, assessing the size of the upper airway and foreign body is necessary. Tracheostomy and foreign body removal through the tracheal opening should be considered proactively.

Optimal Monitoring Technology for Pediatric Thyroidectomy

This retrospective study aimed to describe, firstly, characteristics and outcomes of the intraoperative neural monitoring technology in the pediatric population, and secondarily the recurrent laryngeal nerve complication rate. Thirty-seven patients (age <18 years) operated on from 2015 to 2021 by conventional open thyroid surgery were included. Twenty-four (64.9%) total thyroidectomies and 13 (35.1%) lobectomies were performed. Seven central and six lateral lymph node dissections completed 13 bilateral procedures. Histology showed malignancy in 45.9% of the cases. The differences between the electromyographic profiles of endotracheal tubes or electrodes for continuous monitoring were not statistically significant. In our series of young patients, both adhesive (even in 4- or 5-year-olds) and embedded endotracheal tubes were used, while in patients 3 years old or younger, the use of a more invasive detection method with transcartilage placement recording electrodes was required. Overall, out of 61 total at-risk nerves, 5 (8.2%) recurrent laryngeal nerves were injured with consequent intraoperative loss of the signal; however, all these lesions were transient, restoring their normal functionality within 4 months from surgical procedure. To our knowledge, this is the first study of intraoperative neural monitoring management in a cohort of Italian pediatric patients.

Cuffed versus uncuffed endotracheal tubes for neonates

BACKGROUND

Endotracheal intubation is a commonly performed procedure in neonates, the risks of which are well-described. Some endotracheal tubes (ETT) are equipped with a cuff that can be inflated after insertion of the ETT in the airway to limit leak or aspiration. Cuffed ETTs have been shown in larger children and adults to reduce gas leak around the ETT, ETT exchange, accidental extubation, and exposure of healthcare workers to anesthetic gas during surgery. With improved understanding of neonatal airway anatomy and the widespread use of cuffed ETTs by anesthesiologists, the use of cuffed tubes is increasing in neonates.

OBJECTIVES

To assess the benefits and harms of cuffed ETTs (inflated or non-inflated) compared to uncuffed ETTs for respiratory support in neonates.

SEARCH METHODS

We searched CENTRAL, PubMed, and CINAHL on 20 August 2021; we also searched trial registers and checked reference lists to identify additional studies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs), quasi-RCTs, and cluster-randomized trials comparing cuffed (inflated and non-inflated) versus uncuffed ETTs in newborns. We sought to compare 1. inflated, cuffed versus uncuffed ETT; 2. non-inflated, cuffed versus uncuffed ETT; and 3. inflated, cuffed versus non-inflated, cuffed ETT.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal. Two review authors independently assessed studies identified by the search strategy for inclusion, extracted data, and assessed risk of bias. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We identified one eligible RCT for inclusion that compared the use of cuffed (inflated if ETT leak greater than 20% with cuff pressure 20 cm H₂O or less) versus uncuffed ETT. The author provided a spreadsheet with individual data. Among 76 infants in the original manuscript, 69 met the inclusion and exclusion criteria for this Cochrane Review. We found possible bias due to lack of blinding and other bias. We are very uncertain about frequency of postextubation stridor, because the confidence intervals (CI) of the risk ratio (RR) were very wide (RR 1.36, 95% CI 0.35 to 5.25; risk difference (RD) 0.03, -0.11 to 0.18; 1 study, 69 participants; very low-certainty evidence). No neonate was diagnosed with postextubation subglottic stenosis; however, endoscopy was not available to confirm the clinical diagnosis. We are very uncertain about reintubation for stridor or subglottic stenosis because the CIs of the RR were very wide (RR 0.27, 95% CI 0.01 to 6.49; RD -0.03, 95% CI -0.11 to 0.05; 1 study, 69 participants; very low-certainty evidence). No neonate had surgical intervention (e.g. endoscopic balloon dilation, cricoid split, tracheostomy) for stridor or subglottic stenosis (1 study, 69 participants). Neonates randomized to cuffed ETT may be less likely to have a reintubation for any reason (RR 0.06, 95% CI 0.01 to 0.45; RD -0.39, 95% CI -0.57 to -0.21; number needed to treat for an additional beneficial outcome 3, 95% CI 2 to 5; 1 study, 69 participants; very low-certainty evidence). We are very uncertain about accidental extubation because the CIs of the RR were wide (RR 0.82, 95% CI 0.12 to 5.46; RD -0.01, 95% CI -0.12 to 0.10; 1 study, 69 participants; very low-certainty evidence). We are very uncertain about all-cause mortality during initial hospitalization because the CIs of the RR were extremely wide (RR 2.46, 95% CI 0.10 to 58.39; RD 0.03, 95% CI -0.05 to 0.10; 1 study, 69 participants; very low-certainty evidence). There is one ongoing trial. We classified two studies as awaiting classification because outcome data were not reported separately for newborns and older infants.

AUTHORS' CONCLUSIONS

Evidence for comparing cuffed versus uncuffed ETTs in neonates is limited by a small number of babies in a single RCT with possible bias. There is very low certainty evidence for all outcomes of this review. CIs of the estimate for postextubation stridor were wide. No neonate had clinical evidence for subglottic stenosis; however, endoscopy results were not available to assess the anatomy. Additional RCTs are necessary to evaluate the benefits and harms of cuffed ETTs (inflated and non-inflated) in the neonatal population. These studies must include neonates and be conducted both for short-term use (in the setting of the operating room) and chronic use (in the setting of chronic lung disease) of cuffed ETTs.

Management of Inedible Airway Foreign Bodies in Pediatric Rigid Bronchoscopy: Experience From a National Children's Regional Medical Center in China

The aim of this study is to analyze the characteristics of inedible airway foreign bodies in pediatric rigid bronchoscopy to facilitate the improvement of management and technology. This retrospective analytical study was performed from January 2017 to June 2020. All admissions of pediatric patients (age<18 years) with foreign-body aspiration diagnosis codes ([ICD]-10:T17 300, T17 400, T17 500 and T17 900) and procedure codes (33.7801) were extracted. Age, sex, preoperative history and imaging data, surgical records, length of hospital stay, reoperations and postoperative complications were included. Data were analyzed with SPSS 20. A total of 1237 patients were hospitalized and underwent rigid bronchoscopy. Forty-five (3.6%) patients with inedible foreign bodies in the airway were confirmed. There were no significant differences in sex, time of onset and length of hospital stay between the inedible and edible foreign body groups, except for age and a definite history of foreign body aspiration (P = 0.000). Coughing, wheezing and fever were the common clinical symptoms in all patients. The following were the common locations of inedible foreign bodies: right bronchus (22/45), left bronchus (18/45), trachea (3/45) and larynx (2/45). The most frequent inedible foreign bodies were parts of a pen (15/45), a light-emitting diode (7/45) and plastic parts of toys (6/45). Vocal cord injury and a laryngeal web were observed in one case each.

CONCLUSION

Rigid bronchoscopy is the method of choice for the removal of inedible foreign bodies. Adequate preoperative assessment to rely on CT scans, skillful operation techniques to avoid damaging and active management of postoperative complications are important for the success of the procedure.

TRANSITION AND LAMINAR FLOWS IN A REALISTIC GEOMETRY OF HUMAN UPPER AIRWAY

In this study, a realistic respiratory airway model extending from oral to the end of the trachea including all the key details of the passage was produced. A series of CT scan images were used to generate the topological data of airway cross-sections that were used to generate the computational model, as well as the three-dimensional (3D) printed model of the passage for experimental study. The airflow velocity field and pressure drop in the airway for different breathing rates of 5, 7.5, 10, and 12.5[Formula: see text]L/min were investigated numerically (by laminar and transition models) and experimentally. The velocity distributions, pressure variation, and streamlines along the oral–trachea airway model were studied. The maximum pressure drop was shown to occur in the narrowest part of the larynx region. It was also concluded that the laryngeal jet could significantly influence the airway flow patterns in the trachea. A comparison between the numerical results and experimental data showed that the transition [Formula: see text]–kl–[Formula: see text] model can give better predictions of pressure losses, especially for flow rates higher than 10[Formula: see text]L/min. The simulation results for the velocity profiles in the trachea were also compared with the available particle image velocimetry (PIV) data and earlier simulations. Despite inter-personal variability and difference in the flow regime, the qualitative agreement was found.

Computational Fluid Dynamic Modeling Reveals Nonlinear Airway Stress during Trachea Development

Normative trachea dimensions and aerodynamic information during development was collected to establish clinical benchmarks and showed that airway development seems to outpace respiratory demands. Infants and toddlers' trachea exhibit higher aerodynamic stress that significantly decreases by teenage years. This implies large airway pathology in younger children may have a more substantial clinical impact.

Effect of adenoid hypertrophy on the upper airway and craniomaxillofacial region

BACKGROUND

In recent years, annual incidences of adenoid hypertrophy (AH), a highly common tissue lesion in children, have increased. Currently, research on AH has focused on its obstruction of nasal cavity function, and little has been written on its influence on the upper airway's bone structure. For this reason, our present study seeks to determine the influence of AH on both the morphological development characteristics of the upper airway and the craniofacial features in children, with the goal being to offer more choices for diagnosing and treating the condition in the future.

METHODS

From June 2019 to December 2020 in Department of Orthodontics, Beijing Stomatological Hospital, Capital Medical University, 38 children with AH admitted to the Department of Otolaryngology [research group (RG)] and 35 children [control group (CG)] who underwent orthodontic treatment over the same time span were selected as the research objects. X-ray examination of the lateral position of the head, observation of the maxillofacial structure, and detection of the children's height, growth factors, and sleep status, and analysis of the differences between the two groups.

RESULTS

The height of RG, insulin-like growth factor-1 (IGF-1) as well as insulin-like growth factor binding protein-3 (IGFBP-3) were all lower than CG (P<0.05), the upper airway became narrower, and the malocclusion was aggravated (P<0.05). Cephalometric measurement showed that the angle between the subspinale and sella at nasion (SNA angle) and the angle between the subspinale and supraemental at nasion (ANB angle) of RG children decreased, and the angle between the supraemental and sella at nasion (SNB angle) increased (P<0.05). In addition, the sleep quality of RG was significantly lower than that of CG (P<0.05).

CONCLUSIONS

AH can change a child's breathing mode and function by giving rise to upper airway stenosis, and by inducing deformities of their craniomaxillofacial region and oral cavity, thus disrupting their normal growth and development.

[Ventilation in Pediatric Anesthesia]

About nine percent of all anesthesia procedures per year are performed in children. The risk for complications in pediatric anesthesia is higher in comparison with adults. There are significant differences in anatomy, physiology and pharmacology between pediatric and adult patients. Respiratory complications and circulations dysregulation occur more often in children. The most important consideration in the safe practice of pediatric anesthesia is to ensure a patent airway. Appropriate intraoperative management of newborns and infants needs a senior anesthetist with good knowledge and clinical experience including the management of possible complications.

Pediatric airway management

PURPOSE OF REVIEW

Children are at risk of severe hypoxemia in the perioperative period owing to their unique anatomy and physiology. Safe and effective airway management strategies are therefore key to the practice of pediatric anesthesia. The goal of this review is to highlight recent publications (2019-2021) aimed to advance pediatric airway safety and to highlight a proposed simple, pediatric-specific, universal framework to guide clinical practice.

RECENT FINDINGS

Recent investigations demonstrate that infants with normal and difficult airways experience high incidences of multiple laryngoscopy attempts and resulting hypoxemia. Video laryngoscopy may improve tracheal intubation first attempt success rate in infants with normal airways. In infants with difficult airways, standard blade video laryngoscopy is associated with higher first attempt success rates over non-standard blade video laryngoscopy. Recent studies in children with Pierre Robin sequence and mucopolysaccharidoses help guide airway equipment and technique selection. Department airway leads and hospital difficult airway services are necessary to disseminate knowledge, lead quality improvement initiatives, and promote evidence-based practice guidelines.

SUMMARY

Pediatric airway management morbidity is a common problem in pediatric anesthesia. Improvements in individual practitioner preparation and management strategies as well as systems-based policies are required. A simple, pediatric-specific, universal airway management framework can be adopted for safe pediatric anesthesia practice.

Anatomical In Vitro Investigations of the Pediatric Larynx: A Call for Manufacturer Redesign of Tracheal Tube Cuff Location and Perhaps a Call to Reconsider the Use of Uncuffed Tracheal Tubes

BACKGROUND

Some in vivo studies question the traditional "funnel-shaped" infant larynx; further anatomic examinations were warranted. Examination of fixative free fresh autopsy laryngeal and upper tracheal specimens and multiple measurements was needed to determine consistency between current tracheal tube designs and anatomic observations.

METHODS

Larynges from 19 males and 11 females (Caucasian term newborn to 126 months) were examined by the same forensic pathologist. Measurements included anterior/posterior (A/P) and transverse (T) diameters of the cricoid outlet (CO), interarytenoid diameter (IAD), cricothyroid membrane (CTM), distance from the vocal cords (VC) to CO (VC-CO), and calibration of the larynx lumen with uncuffed tracheal tubes as measuring rods. Assessment of "safe tracheal tube placement" was assessed using manufacturer recommended cuffed Microcuff (Kimberly-Clark, Koblenz, Germany) tubes.

RESULTS

In 77% (95% confidence interval [CI], 58-90) of specimens, the proximal end of the cuff was within the CO and in 23% even with or close to the CO. The VC-CO varied from 9.1 to 13.17 mm in infants, 11.55 to 15.17 mm in toddlers, and 13.19 to 18.34 mm in children. The AP/T ratio of the CO was nearly 0.99 in most larynges; the IAD was greater than CO in all specimens. The CTM could be minimally distended in all specimens.

CONCLUSIONS

First, despite being marketed as a safer tracheal tube design, the proximal end of the Microcuff cuff rested within or close to the cricoid cartilage theoretically increasing potential cuff-induced injury when using the VC markings for positioning. Our data suggest that the optimal cuff free distance (VC-CO) would be ~13.5 mm for a Microcuff internal diameter (ID) size 3.0, ~15 mm for size 3.5, and ~16 to 19 mm for greater sizes.Second, the CO was virtually circular in all specimens, suggesting that appropriately sized uncuffed tubes should provide an adequate seal in most neonates and toddlers, thus avoiding the potential for cuff-related necrosis injury.Third, the IAD was always greater than CO confirming that the narrowest point of the infant larynx is the nondistensible cricoid cartilage and not the easily distended glottis.Fourth, appropriately sized Microcuff tubes with the cuff deflated completely filled the lumen of the CO and proximal trachea in all specimens. Our data suggest the need for all manufacturers to further evaluate tracheal tube cuff locations and lengths in relation to the VC safe insertion markings, particularly for neonates and toddlers.Fifth, the CTM is minimally distensible, thus having important implications for emergency surgical airway access with most currently available emergency airway devices.

Structural and functional development in airways throughout childhood: Children are not small adults

Children are not small adults and this fact is particularly true when we consider the respiratory tract. The anatomic peculiarities of the upper airway make infants preferential nasal breathers between 2 and 6 months of life. The pediatric larynx has a more complex shape than previously believed, with the narrowest point located anatomically at the subglottic level and functionally at the cricoid cartilage. Alveolarization of the distal airways starts conventionally at 36-37 weeks of gestation, but occurs mainly after birth, continuing until adolescence. The pediatric chest wall has unique features that are particularly pronounced in infants. Neonates, infants, and toddlers have a higher metabolic rate, and consequently, their oxygen consumption at rest is more than double that of adults. The main anatomical and functional differences between pediatric and adult airways contribute to the understanding of various respiratory symptoms and disease conditions in childhood. Knowing the peculiarities of pediatric airways is helpful in the prevention, management, and treatment of acute and chronic diseases of the respiratory tract. Developmental modifications in the structure of the respiratory tract, in addition to immunological and neurological maturation, should be taken into consideration during childhood.

Efficient Collection and Representation of Preverbal Data in Typical and Atypical Development

Human preverbal development refers to the period of steadily increasing vocal capacities until the emergence of a child’s first meaningful words. Over the last decades, research has intensively focused on preverbal behavior in typical development. Preverbal vocal patterns have been phonetically classified and acoustically characterized. More recently, specific preverbal phenomena were discussed to play a role as early indicators of atypical development. Recent advancements in audio signal processing and machine learning have allowed for novel approaches in preverbal behavior analysis including automatic vocalization-based differentiation of typically and atypically developing individuals. In this paper, we give a methodological overview of current strategies for collecting and acoustically representing preverbal data for intelligent audio analysis paradigms. Efficiency in the context of data collection and data representation is discussed. Following current research trends, we set a special focus on challenges that arise when dealing with preverbal data of individuals with late detected developmental disorders, such as autism spectrum disorder or Rett syndrome.

Posterior glottic stenosis: management and outcomes

PURPOSE OF REVIEW

Pediatric posterior glottic stenosis (PGS) is a challenging clinical entity with multiple treatment options. This review describes the evaluation of patients with PGS and discusses existing surgical techniques.

RECENT FINDINGS

PGS secondary to a distinct scar band between the vocal folds can often be effectively managed with endoscopic division and surveillance. More advanced glottic scarring that also involves the interarytenoid mucosa, cricoarytenoid joints, or subglottis merits a more thorough investigation and repair. A postcricoid mucosal advancement flap can be employed in select adolescent or adult PGS, but long-term cricoarytenoid joint mobility is difficult to restore once it has been fixed. Younger pediatric patients have smaller airways and frequent concurrent subglottic stenosis which is better addressed with cartilage grafting.

SUMMARY

Surgical success in pediatric PGS depends on careful preoperative airway assessment and the accurate characterization of airway stenosis. A surgical technique should be chosen based on the severity and extent of stenosis.

Pediatric airway: What is new in approaches and treatments?

Perioperative morbidity and mortality are high among patients in the extremes of life undergoing anesthesia. Complications in children occur mainly as a result of airway management-related events such as difficult approach, laryngospasm, bronchospasm and severe hypoxemia, which may result in cardiac arrest, neurological deficit or death. Reports and new considerations that have changed clinical practice in pediatric airway management have emerged in recent years. This narrative literature review seeks to summarize and detail the findings on the primary cause of morbidity and mortality in pediatric anesthesia and to highlight those things that anesthetists need to be aware of, according to the scientific reports that have been changing practice in pediatric anesthesia. This review focuses on the identification of “new” and specific practices that have emerged over the past 10 years and have helped reduce complications associated with pediatric airway management. At least 9 practices grouped into 4 groups are described: assessment, approach techniques, devices, and algorithms. The same devices used in adults are essentially all available for the management of the pediatric airway, and anesthesia-related morbidity and mortality can be reduced through improved quality of care in pediatrics.

A comparison of videolaryngoscopy using standard blades or non-standard blades in children in the Paediatric Difficult Intubation Registry

BACKGROUND

The design of a videolaryngoscope blade may affect its efficacy. We classified videolaryngoscope blades as standard and non-standard shapes to compare their efficacy performing tracheal intubation in children enrolled in the Paediatric Difficult Intubation Registry.

METHODS

Cases entered in the Registry from March 2017 to January 2020 were analysed. We compared the success rates of initial and eventual tracheal intubation, complications, and technical difficulties between the two groups and by weight stratification.

RESULTS

Videolaryngoscopy was used in 1313 patients. Standard and non-standard blades were used in 529 and 740 patients, respectively. Both types were used in 44 patients. In children weighing <5 kg, standard blades had significantly greater success than non-standard blades at initial (51% vs 26%, P=0.002) and eventual (81% vs 58%, P=0.002) attempts at tracheal intubation. In multivariable logistic regression analysis, standard blades had 3-fold greater odds of success at initial tracheal intubations compared with non-standard blades (adjusted odds ratio 3.0, 95% confidence interval): 1.32-6.86, P=0.0009). Standard blades had 2.6-fold greater odds of success at eventual tracheal intubation compared with non-standard blades in children weighing <5 kg (adjusted odds ratio 2.6, 95% confidence interval: 1.08-6.25, P=0.033). There was no significant difference found in children weighing ≥5 kg.

CONCLUSIONS

In infants weighing <5 kg, videolaryngoscopy with standard blades was associated with a significantly greater success rate than videolaryngoscopy with non-standard blades. Videolaryngoscopy with a standard blade is a sensible choice for tracheal intubation in children who weigh <5 kg.

Postnatal Development of the Mouse Larynx: Negative Allometry, Age-Dependent Shape Changes, Morphological Integration, and a Size-Dependent Spectral Feature

Purpose The larynx plays a role in swallowing, respiration, and voice production. All three functions change during ontogeny. We investigated ontogenetic shape changes using a mouse model to inform our understanding of how laryngeal form and function are integrated. We understand the characterization of developmental changes to larynx anatomy as a critical step toward using rodent models to study human vocal communication disorders. Method Contrast-enhanced micro-computed tomography image stacks were used to generate three-dimensional reconstructions of the CD-1 mouse (Mus musculus) laryngeal cartilaginous framework. Then, we quantified size and shape in four age groups: pups, weanlings, young, and old adults using a combination of landmark and linear morphometrics. We analyzed postnatal patterns of growth and shape in the laryngeal skeleton, as well as morphological integration among four laryngeal cartilages using geometric morphometric methods. Acoustic analysis of vocal patterns was employed to investigate morphological and functional integration. Results Four cartilages scaled with negative allometry on body mass. Additionally, thyroid, arytenoid, and epiglottic cartilages, but not the cricoid cartilage, showed shape change associated with developmental age. A test for modularity between the four cartilages suggests greater independence of thyroid cartilage shape, hinting at the importance of embryological origin during postnatal development. Finally, mean fundamental frequency, but not fundamental frequency range, varied predictably with size. Conclusion In a mouse model, the four main laryngeal cartilages do not develop uniformly throughout the first 12 months of life. High-dimensional shape analysis effectively quantified variation in shape across development and in relation to size, as well as clarifying patterns of covariation in shape among cartilages and possibly the ventral pouch. Supplemental Material https://doi.org/10.23641/asha.12735917.

Age-related Change of the Dimensions of the Cricoid Cartilage in Adults

OBJECTIVES

To measure the dimensions of the cricoid cartilage in adults and to investigate the age-related change of the dimensions of the cricoid cartilage.

METHODS

After performing the multiplanar reconstruction and correcting the slant of the cervical computed tomography scans, the transverse and anteroposterior internal diameters of the inlet (TD-in and APD-in) and outlet (TD-out and APD-out) of the cricoid cartilage were measured, respectively. The angle between the arch and lamina of the cricoid cartilage in the middle sagittal plane was measured. The ratios of transverse to anteroposterior diameter for the inlet (Ratio-in) and outlet (Ratio-out) of the cricoid cartilage were calculated, respectively.

RESULTS

A total of 1200 adults were included in this study, with 600 males and 600 females. The TD-in is the smallest cricoid diameter and the APD-in is the largest cricoid diameter. The mean cricoid diameters and the cricoid angle in males were larger than those in females. The cricoid inlet is oval shaped and the cricoid cartilage is "funnel-shaped" in the middle sagittal plane. The shape of the outlet of the cricoid cartilage varies greatly among individuals. In males, the APD-in and APD-out were negatively correlated with age while the Ratio-in and Ratio-out was positively correlated with age. In females, the APD-out were negatively correlated with age while the Ratio-out was negatively correlated with age.

CONCLUSIONS

The dimensions of the cricoid cartilage change as age advances in adult population and the sexual dimorphism of the cricoid outlet occurs after 50 years old.

Tracheostomy in Infants in the Neonatal Intensive Care Unit

Approximately half of all pediatric tracheostomies are performed in infants younger than 1 year. Most tracheostomies in patients in the NICU are performed in cases of chronic respiratory failure requiring prolonged mechanical ventilation or upper airway obstruction. With improvements in ventilation and management of long-term intubation, indications for tracheostomy and perioperative management in this population continue to evolve. Evidence-based protocols to guide routine postoperative care, prevent and manage tracheostomy emergencies including accidental decannulation and tube obstruction, and attempt elective decannulation are sparse. Clinician awareness of safe tracheostomy practices and larger, prospective studies in infants are needed to improve clinical care of this vulnerable population.

Developmental changes of upper airway dimensions in children

BACKGROUND

Knowledge about airway dimensions during child growth is of paramount importance for pediatric clinical practice. Decisions about airway management in children are based on relatively limited, imprecise, or incomplete data about airway size.

AIMS

The aim of this work was to determine the anatomical development and size of airway structures from birth to adolescence using high-resolution computed tomography scans and to study the correlation between airway measurements and biometric data.

METHODS

We conducted a retrospective study of all high-resolution computed tomography scans including the respiratory tract, performed in our tertiary pediatric center (for reasons unrelated to airway symptoms) between June 1, 2016, and October 15, 2017, on children aged from 1 day to 14 years old. On each scan, 23 measurements of the larynx, trachea, and mainstem bronchi were performed. Patients were stratified into 16 groups according to their age. We calculated median value for each measurement in each group. Statistical models were calculated to explore correlation between measurements and age or weight.

RESULTS

A total of 192 scans were included (127 boys/65 girls). The mean age was 7 years. The correlations between airway measurements and age or weight were always significant. The relationship between measurements and age was found to be suitably represented by a cubic polynomial equation suggesting that the airway has a rapid growth phase in the first 3 years, followed by a slow growth phase and a second rapid growth phase during adolescence. The most relevant biometric parameter was age concerning 21 of the measurements.

CONCLUSION

This comprehensive anatomical database of upper airway dimensions provides important data in the field of pediatric airway anatomy, particularly relating to the cricoid. We demonstrated that laryngeal, tracheal, and bronchial parameters correlate better to age and have three different growth phases.

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.

Neonatal Airway Management

Safe and effective airway management of neonates requires unique knowledge and clinical skills. Practitioners should have an understanding of neonatal airway anatomy and respiratory physiology and their clinical implications related to airway management. It is vital to recognize the potential sequelae of prematurity. Clinicians should be familiar with the skills and techniques available for managing normal neonatal airways. This review provides stepwise considerations for managing the neonatal airway: specific considerations for neonatal airway management, assessment and preparation, induction and premedication, and techniques and strategies for airway management in patients with normal anatomy and in patients who are difficult to intubate.

Pediatric airway dimensions-A summary and presentation of existing data

BACKGROUND

Age-related pediatric airway dimension reference values for cricoid, tracheal, and bronchial diameters as well as tracheal and bronchial lengths are essential for distinguishing normal from pathological airway findings and for manufacturing and selecting appropriately sized airway equipment.

AIM

The aim of this work was to summarize and present existing pediatric airway dimension data for the larynx, trachea, and main stem bronchi from fetus to adolescence.

METHODS

A systematic literature search was carried out using PubMed, Scopus, Embase, and Google Scholar. Publications containing original data on pediatric airway dimensions as mean or median in tabular form and spanning narrow age groups of 1 or 2 years were included in our study. Original data such as diameters, lengths, and cross-sectional areas of trachea, cricoid, left and right main bronchi in fetuses and children were collected and presented as figures.

RESULTS

Pediatric airway dimension data were gathered and compiled from 15 studies fulfilling the inclusion criteria. Data were obtained from different measurement methods such as autopsy, chest X-ray, computed tomography, magnetic resonance imaging, rigid and flexible bronchoscopy as well as ultrasound examinations. There was considerable variation among age-related data due to biologic heterogeneity, different presentation of data, different definitions, and various measurement techniques.

CONCLUSION

This investigation revealed heterogeneous data on pediatric airway dimensions, making it impossible to compile them into standard reference values for airway dimensions. New studies with structured and standardized measurements and data presentation in large populations of children are required to provide more valid pediatric airway dimension data.

The influence of premature birth on laryngeal development for phonation

INTRODUCTION

Dysphonia is a known consequence of premature birth, and is usually associated with endotracheal intubation in the neonatal period or surgical ligation of persistent patent ductus arteriosus. Recently, cases of dysphonia, in the absence of these causative factors, have been reported.

OBJECTIVES

This review seeks to identify literature pertaining to those aspects of laryngeal development that may potentially be disrupted by premature birth. The purpose of the review is to determine whether there is any possible anatomical or physiological explanation for dysphonia to arose solely from premature birth.

METHODS

This scoping review was conducted in accordance with the guidelines prescribed by Arskey and O'Malley (2005). Fifteen relevant papers were identified. Results were categorized into age-related categories, to identify changes in the developmental trajectory. Based on the results of the literature search, a further category of unphonated larynges was added.

RESULTS

Potential differences in the laryngeal framework (e.g., the development of the cricoid cartilage and the shape of the glottis) and vocal fold histology, depending on gestational age and post-natal phonation were identified. Much literature focused on the macula flavae, however, the layers of the lamina propria were also discussed.

DISCUSSION

It is unclear whether the process of differentiation of the layers of the lamina propria, which commences in the second to third months of life in term-born infants, is disrupted by prematurity. Further, development of the macula flavae continues until at least 28 weeks' gestation. Preterm children may not phonate immediately after birth, which may also affect laryngeal development.

Accuracy of ultrasound in measurement of the pediatric cricothyroid membrane

BACKGROUND

Emergency front of neck airway is a recommended airway rescue strategy in children over 1 year old. Surgical tracheostomy is advocated as the first-line technique, but in the absence of an ear, nose and throat surgeon cricothyroidotomy or tracheostomy is proposed. Recent research shows that clinical identification of the cricothyroid membrane is frequently inaccurate in older children and adults and has prompted investigation of ultrasound as a potential clinical tool for emergency front of neck airway. Advance knowledge of the dimensions of the pediatric cricothyroid membrane may assist clinicians in determining the feasibility of emergency front of neck airway, optimum technique, and equipment.

AIMS

The aim of this study was to assess the accuracy of ultrasound-assisted pediatric cricothyroid membrane localization and dimension measurement using magnetic resonance imaging as the reference standard.

METHODS

After structured training, two pediatric anesthesiology trainees used ultrasound to identify and measure the dimensions of the cricothyroid membrane in pediatric patients undergoing elective magnetic resonance imaging of the head and neck under general anesthesia. A pediatric radiologist reviewed the corresponding magnetic resonance imaging scans and measured the height of the cricothyroid membrane. The accuracy of the cricothyroid membrane height as measured by ultrasound was compared to that measured by magnetic resonance imaging.

RESULTS

Twenty-two patients were included in the study. The cricothyroid membrane was accurately identified by ultrasound in all cases. The correlation coefficient for cricothyroid membrane height measured by ultrasound and that measured by magnetic resonance imaging was 0.98 (95% C.I 0.95-0.99, P < 0.0001). The bias was -0.16 mm and the precision was 0.19 mm. All differences were within the a priori limits of agreement. The 95% limits of agreement were -0.54 to 0.22 mm.

CONCLUSION

Ultrasound can be used to accurately identify and measure cricothyroid membrane height in pediatric patients. This approach could have clinical and research utility.

The pediatric airway: Historical concepts, new findings, and what matters

New observations from novel imaging techniques regarding the anatomy, dimensions, and shape of the pediatric airway have emerged and provide insight for potential changes in the clinical management of the airway in infants and children. These new findings are challenging the historical concepts of a funnel-shaped upper airway with the cricoid ring as the narrowest dimension. Although these tenets have been accepted and used to guide clinical practice in airway management, there are limited clinical investigations in children to support the validity of these concepts. Imaging modalities such as magnetic resonance imaging, computed tomography (CT) scanning, multi-detector CT imaging, and videobronchoscopy suggest the need to revisit the historical view of the pediatric airway. This manuscript reviews the historical evolution of pediatric airway studies, summarizes important scientific observations from recent investigations relevant to our clinical understanding of pediatric airway anatomy, and discusses the importance of these findings for pediatric airway management.

Detailed computational analysis of flow dynamics in an extended respiratory airway model

BACKGROUND

Understanding respiratory physiology can aid clinicians in diagnosing the cause of respiratory symptoms or shed light on drug delivery inhaler device optimisation. However, the sheer complexity of the human lung prohibits a full-scale study.

METHODS

In this study, a realistic respiratory airway model including large-to-small conducting airways was built. This airway model consists of subject-specific upper and lower airways, extending from nasal and oral openings to terminal bronchioles (up to the 15th generation). Based on the subject-specific airway model, topological information was extracted and a digital reference model that exhibits strong asymmetry and multi-fractal properties was provided. Inhalation flow rates 18 L/min and 50 L/min were adopted to understand inspiratory conditions subjecting to resting and light exercise inhalation modes. Regional airflow in terms of axial velocity and secondary flow vortices along the lung airway model was extracted.

FINDINGS

Obvious secondary flow currents were seen in the larynx-trachea segment and left main bronchus, while for the terminal conducting airway in the right lower lobe, the airflow tends to be much smoother with no secondary flow currents.

INTERPRETATION

This paper provides insights on respiratory physiology, especially in the lower lung airways, and will be potentially useful for diagnosis of lower airway diseases.

Uncuffed Endotracheal Tubes: Not Appropriate for Pediatric Critical Care Transport

OBJECTIVE

The effect of using uncuffed endotracheal tubes in children during interfacility critical care transport has not yet been assessed. We hypothesized that many children with uncuffed endotracheal tubes experience complications leading to replacement with a cuffed tube after arrival at a tertiary pediatric care facility.

METHODS

We conducted a retrospective case review of all intubated patients transported by our dedicated pediatric critical care transport team to our pediatric intensive care unit over a 3-year period. The incidence of urgent reintubation was studied.

RESULTS

A total of 213 children were referred for transport with an endotracheal tube in place, with 55 of those with an uncuffed endotracheal tube (25.8% of all intubated patients). Of those with uncuffed tubes, 24 patients needed their tubes replaced on an urgent basis by the medical team because of issues with ineffective ventilation (43.6% of patients with uncuffed tubes or 11.3% of all intubated patients). No cuffed tubes required replacement.

CONCLUSION

Placing an uncuffed endotracheal tube in the critically ill child who is referred to tertiary pediatric care results in a significant number of these patients undergoing a repeat laryngoscopy, with all associated risks, to replace the uncuffed tube with a cuffed tube.

Airway dimensions from fetal life to adolescence-A literature overview

BACKGROUND

Data on airway dimensions in pediatric patients are important for proper selection of pediatric airway equipment such as endotracheal tubes, double-lumen tubes, bronchial blockers, or stents. The aim of the present work was to provide a synopsis of the available data on pediatric airway dimensions.

METHODS

A systematic literature search was carried out in the PubMed database, Scopus, Embase, Web of Science, Prisma, and Google Scholar and secondarily completed by a reference search. Based on inclusion and exclusion criteria, a final selection of 109 studies with data on pediatric airway dimensions published from 1923 to 2018 were further analyzed.

RESULTS

Six different airway measurement methods were identified. They included anatomical examinations, chest X-ray, computed tomography, magnetic resonance tomography, bronchoscopy, and ultrasound. Anatomical studies were more abundant compared to other methods. Data provided were very heterogeneously presented and powered. In addition, due to different study conditions, they are hardly comparable. Among all, anatomical and computer tomography studies are thought to provide the most reliable data. Ultrasound is an upcoming technique to estimate airway parameters of fetus and premature infants. There was, in general, a lack of comprehensive studies providing a complete range of airway dimensions in larger groups of patients from birth to adolescence.

CONCLUSIONS

This work revealed a large heterogeneity of studies providing data on pediatric airway dimensions, making it impossible to compare, or assemble them to normograms for clinical use. Comprehensive studies in large population of children are needed to provide full range nomograms on pediatric airway dimensions.