Lower airway dimensions in pediatric patients-A computed tomography study

Exchange rates of second generation Microcuff® pediatric endotracheal tubes in children weighing more than 3 kg : A retrospective audit

BACKGROUND

Cuffed endotracheal tubes (cETT) pose the potential advantage of an infrequent need for reintubation in pediatric patients compared to uncuffed tubes. The aim of this study was to investigate tube exchange rates using second generation Microcuff® pediatric endotracheal tubes (PET) with an adapted sizing recommendation in a large single institution cohort of children and to identify potential variables associated with an elevated risk of tube exchange.

METHODS

Patient data obtained from the electronic patient data management system of the Department of Anesthesia, University Children's Hospital Zurich, Switzerland, were retrospectively assessed for demographic and anthropometric information, size of the internal tube diameter used for positive pressure ventilation and divergence from the size recommendation chart.

RESULTS

Data from 14,188 children younger than 16 years (median 5.3 years) and weighing at least 3 kg who underwent oral or nasal tracheal intubation using second generation Microcuff® PET between 2009 and 2015 were included. Of 13,219 oral tracheal intubations 12,049 (84.9%) were performed according to the manufacturer's size recommendation and 1170 with divergent endotracheal tubes. The odds ratio (OR) of oral reintubation was 0.13% (95% confidence interval 0.08-0.22%) for cases using the manufacture's size recommendation correctly and 22.74% (95% confidence interval 20.42-25.23%) for patients intubated with a not recommended tube (p < 0.0001).

CONCLUSION

These findings indicate that the second generation Microcuff® PETs can be reliably used with low tube exchange rates across the entire pediatric age range when the tube size is selected according to the manufacturer's size recommendation chart. Adherence to the manufacturer's tube size recommendation is urgently advised.

Computed tomography morphological assessments of central airways in interstitial lung abnormalities and idiopathic pulmonary fibrosis

BACKGROUND

Little is known about whether central airway morphological changes beyond traction bronchiectasis develop and affect clinical outcomes in patients with idiopathic pulmonary fibrosis (IPF). This study aimed to compare central airway structure comprehensively between patients with IPF, subjects with interstitial lung abnormality (ILA), and those without ILA (control) using computed tomography (CT). We further examined the prognostic impact of IPF-specific CT airway parameters in patients with IPF.

METHODS

This retrospective study included male patients with IPF, and male health checkup subjects divided into those with ILA and control based on lung cancer screening CT. Using an artificial intelligence-based segmentation technique, the extent of fibrotic regions in the lung was quantified. After airway tree segmentation, CT parameters for central airway morphology, including the lumen area of the extrapulmonary airways (LAextra), wall and lumen area of the segmental/subsegmental intrapulmonary airways (WAintra and LAintra), tracheal distortion (tortuosity and curvature) and bifurcation angle of the main carina, were calculated.

RESULTS

There were 106 patients with IPF, 53 subjects with ILA, and 1295 controls. Multivariable models adjusted for age, height and smoking history revealed that LAintra and WAintra were larger in both ILA and IPF, and that tracheal tortuosity and curvature were higher in IPF, but not in ILA, than in the control, whereas the bifurcation angle did not differ between the 3 groups. According to multivariable Cox proportional hazards models including only patients with IPF, increased WAintra was significantly associated with greater mortality (standardized hazard ratio [95% confidence interval] = 1.58 [1.17, 2.14]), independent of the volume of fibrotic regions, normal-appearing regions, or the whole airway tree in the lung.

CONCLUSION

Increased lumen area and wall thickening of the central airways may be involved in the pathogenesis of ILA and IPF, and wall thickening may affect the prognosis of patients with IPF.

Developmental respiratory physiology

Various developmental aspects of respiratory physiology put infants and young children at an increased risk of respiratory failure, which is associated with a higher rate of critical incidents during anesthesia. The immaturity of control of breathing in infants is reflected by prolonged central apneas and periodic breathing, and an increased risk of apneas after anesthesia. The physiology of the pediatric upper and lower airways is characterized by a higher flow resistance and airway collapsibility. The increased chest wall compliance and reduced gas exchange surface of the lungs reduce the pulmonary oxygen reserve vis-à-vis a higher metabolic oxygen demand, which causes more rapid oxygen desaturation when ventilation is compromised. This review describes the various developmental aspects of respiratory physiology and summarizes anesthetic implications.

Dimensional compatibility of rigid ventilating bronchoscopes with pediatric airway anatomy using different recommendations for age-related sizing-A bench study

BACKGROUND

Appropriate size selection of pediatric rigid bronchoscopes is fundamental to avoidance of airway trauma and to a high success rate with the first intubation attempt. The aim of the present study was to compare the outer diameters of pediatric rigid bronchoscopes with the anatomical data on the pediatric airway.

METHODS

Outer diameters (OD) of pediatric rigid ventilating bronchoscopes as given by the manufacturer were compared with published computed tomography internal diameters (ID) of the cricoid outlet, the trachea as well as the left and right proximal mainstem bronchus, using six published recommendations for age-related size selection. The ratios between a specific OD and ID were calculated and given as percentage values (%) for lower and upper age ranges.

RESULTS

Nominal sized 2.5, 3, 3.5, 3.7, 4, 4.5, 5, and 6 rigid bronchoscopes were included. In five recommendations, the rigid bronchoscopes' OD was larger than the internal cricoid diameter in the upper age range, whereas in one recommendation the ratio (OD rigid bronchoscope to ID of cricoid) ranged between 77% and 90% for the upper age and between 95% and 109% for the lower age range. In only one of the six recommendations was the rigid bronchoscope OD larger than the tracheal ID. Ratios for the left and right proximal mainstem bronchus ranged from 70% to 146% for the upper and from 78% to 156% for the lower age range, with the highest ratios for the left proximal mainstem bronchus.

CONCLUSION

Based on this in vitro study, most of the recommendations analyzed result in a balanced fit of rigid bronchoscopes within the cricoid. Since the left mainstem bronchus is considerably smaller than the cricoid, any insertion on this level will require careful endoscopic guidance to avoid damage to the left mainstem bronchus.

Mainstem Bronchial Diameters and Dimensions in Infants and Children: A Systematic Review of the Literature

Anatomic measurements of the right (RMB) and left mainstem bronchi (LMB) in infants and children have been accomplished using various modalities. The objective of the present review was to determine whether enough data were available to provide standardized lower airway dimensions in the pediatric population. For the present study, 12 studies with data of the lower pediatric airway dimensions of 1,611 children published from 1923-2020 were reviewed and analyzed. The eligible criteria included studies measuring lower airway dimensions in the pediatric population. Various techniques were used for airway measurement, with computed tomography studies being most abundant. There was a progressive increase in the size of RMB and LMB with age, with a close approximation of the LMB-to-RMB ratio across all studies. In children younger than 1 year old, the RMB and LMB diameters were between 4 and 5 mm and 3 and 5 mm, respectively. Overall, there was significant variation in the methods and modality used to obtain measurements, and therefore it was difficult to establish standardized lower airway dimensions in the pediatric population. Additional homogeneous data with standardized measurement techniques and modalities across different pediatric age groups are needed to define these dimensions further. Such data may be helpful in designing airway equipment, lung isolation devices, and airway stents.

Determining normal values for lower trachea and bronchi size in children by computed tomography (CT)

BACKGROUND

Normative data for central airway dimensions are a prerequisite to objectively assess large airway pathologies. Studies with computed tomography (CT) measurements of normal trachea and bronchi size in children are scarce.

OBJECTIVE

The purpose of this study is to establish normal values of central airway dimensions in children by CT.

METHODS

The study included chest CT studies from children aged 0-18 years. Any condition that predisposed the patient to have an abnormal tracheal or bronchial size was excluded. Airway diameters and cross-sectional area (CSA) were measured using double oblique reconstructions at five levels: proximal trachea, mid-trachea, distal trachea, right main bronchus, and left main bronchus.

RESULTS

The inclusion criteria were met by 110 subjects (mean age, 10.8 years; SD, 5.2 years). Various regression models that considered the relationship between patient demographics and anteroposterior (AP) diameter, transverse diameter, and CSA at each of the five levels were assessed. R² was utilized to select the best model. Multiple formulae (using patient age) were developed to calculate expected normal dimensions for five levels in the central airways on the natural log scale. Finally, z-scores were obtained for central airway dimensions at these five levels.

CONCLUSION

Normative data in pediatric central airways are crucial to identify large airway pathologies. We propose using the formulae devised in our study to calculate the predicted dimensions of central airways and their z-scores in pediatric patients. Normative data from our study will aid in objective quantification of central airways, increase clinician confidence, and provide appropriate patient care.

Tracheal narrowing in children and adults with mucopolysaccharidosis type IVA: evaluation with computed tomography angiography

BACKGROUND

Mucopolysaccharidosis type IVA (MPS IVA) is characterized by progressive skeletal dysplasia and respiratory issues with difficult airway management during anesthesia.

OBJECTIVE

To characterize tracheal abnormalities in children and adults with MPS IVA including interplay of the trachea, vasculature, bones and thyroid at the thoracic inlet.

MATERIALS AND METHODS

Computed tomography (CT) angiograms of the chest were analyzed for trachea shape, narrowing and deviation at the thoracic inlet, course of vasculature, bone alignment and thyroid location. The tracheal cross-sectional area was measured at the cervical, thoracic inlet and intrathoracic levels.

RESULTS

Thirty-seven patients (mean age: 18.1 years) were included. The mean tracheal cross-sectional area narrowing at the thoracic inlet was 63.9% (range: -2.1-96%), with a trend for increased tracheal narrowing in older children. The trachea was commonly deviated rightward posterior (22/37, 59%). T- or W-shaped tracheas had two times greater tracheal narrowing than D- or U-shaped tracheas (P<0.05). The brachiocephalic artery was tortuous in 35/37 (95%) with direct impingement on the trachea in 24/37 (65%). No correlation was observed between bony thoracic inlet diameter and tracheal narrowing. The thyroid was located in the thoracic inlet in 28/37 (76%) cases, significantly associated with tracheal narrowing (P=0.016).

CONCLUSION

Narrowing, deviation and abnormal shape of the trachea at the thoracic inlet are common in children and adults with MPS IVA, with a trend toward increased narrowing with advancing age in children. A W- or T-shaped trachea is associated with focal tracheal narrowing. Crowding of the thoracic inlet, due to vascular tortuosity and thyroid position, appears to play a major role.

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.

Inflation volume-balloon diameter and inflation pressure-balloon diameter characteristics of commonly used bronchial blocker balloons for single-lung ventilation in children

BACKGROUND

Balloon-tipped bronchial blocker catheters are widely used in pediatric thoracic anesthesia to establish single-lung ventilation. In clinical practice, their balloons demonstrate sudden expansion when inflated with air. In addition, there are concerns related to the high inflation pressures required to expand the balloons.

METHODS

This in vitro study assessed inflation volume- and inflation pressure-balloon diameter characteristics of the Fogarty arterial embolectomy catheters and Arndt endobronchial blockers. Balloon diameters were photographically assessed during unrestricted volume- and pressure-guided inflation, using air up to the maximum allowed inflation volume as indicated by the manufacturers. Inflation pressures required to open the blocker balloons and inflation pressures needed to expand them to maximum indicated diameter were measured.

RESULTS

Volume-guided inflation demonstrated a late acute rise in diameter in Fogarty blocker balloons, whereas in the Arndt endobronchial blocker balloons almost linear inflation volume-to-diameter characteristics were observed. Pressure-guided inflation on the other hand demonstrated low-volume, high-pressure characteristics in the Fogarty blocker balloons, with inflation pressures required to expand the balloons to maximum diameters ranging from (mean (SD)) 636 (75) to 947 (152) cmH₂ O. The inflation pressures required to open the Fogarty blocker balloons were even >1000 cmH₂ O. Inflation pressures required to expand the 5 F, 7 F, and 9 F Arndt endobronchial blocker balloons to maximum indicated diameter were much lower, namely at 218 (15), 252 (28), and 163 (8) cmH₂ O.

CONCLUSION

Based on these study findings, the balloons of Fogarty arterial embolectomy catheters represent high-pressure devices and do not permit stepwise controlled bronchial blockage. The Arndt endobronchial blockers have some advantages over the Fogarty blocker devices, but also represent high-pressure equipment and must be used with caution and limited duration. Manufacturers are asked to design pediatric endobronchial blocker catheters with truly high-volume, low-pressure balloons in accordance to age-related pediatric airway dimensions.

Simulated dimensional compatibility of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children

BACKGROUND

Cuffed tracheal tubes have recently been recommended for selective endobronchial intubation to establish single-lung ventilation even in smaller children. This implies that, compared with uncuffed tracheal tubes, the cuffed tracheal tubes selected will be smaller and therefore have a shorter length. We hypothesized that cuffed tracheal tubes might be of insufficient length for selective endobronchial intubation if the tube cuff were fully immersed in the left or right mainstem bronchus.

METHODS

The distance from the proximal end of the tracheal tube to the upper border of the cuff in cuffed tracheal tubes and to the upper margin of the Murphy eye in uncuffed tracheal tubes, respectively, was assessed in sizes 3.0-7.0 mm internal diameter. The raw data sets of two previously performed studies obtained from 337 children aged from birth to 16 years, including the distances "teeth to tracheal tube tip" and "tracheal tube tip to carina," were used to calculate age-, weight-, and height-related data for the distance from "teeth to carina." Tracheal tube dimensions were compared with age-related distances from "teeth to carina," applying published recommendations for the selection of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children.

RESULTS

The differences between the length of the age-related tracheal tube and the tracheal tube insertion length required to guarantee full insertion of the tracheal tube cuff or the Murphy eye within the mainstem bronchus ranged from -3.5 to 52.6 mm in cuffed tracheal tubes and from 42.3 to 83.3 mm in uncuffed tracheal tubes.

CONCLUSIONS

For many age groups of patients requiring selective endobronchial intubation, the lengths of cuffed tracheal tubes, in contrast to those of uncuffed tracheal tubes, were revealed to be critically short for safe taping outside the oral cavity with the cuff placed completely within the right or left mainstem bronchus.

Rabbit training model for establishing an emergency front of neck airway in children

BACKGROUND

A 'cannot intubate, cannot oxygenate' (CICO) situation is rare in paediatric anaesthesia, but can always occur in children under certain emergency situations. There is a paucity of literature on specific procedures for securing an emergency invasive airway in children younger than 6 yr. A modified emergency front of neck access (eFONA) technique using a rabbit cadaver model was developed to teach invasive airway protection in a CICO situation in children.

METHODS

After watching an instructional video of our eFONA technique (tracheotomy, intubation with Frova catheter over which a tracheal tube is inserted), 29 anaesthesiologists performed two separate attempts on rabbit cadavers. The primary outcome was the success rate and the performance time overall and in subgroups of trained and untrained participants.

RESULTS

The overall success rate across 58 tracheotomies was 95% and the median performance time was 67 s (95% confidence interval [CI], 56-76). Performance time decreased from the first to the second attempt from 72 s (95% CI, 57-81) to 61 s (95% CI, 50-81). Performance time was 59 s (95% CI, 49-79) for untrained participants and 72 s (95% CI, 62-81) for trained participants. Clinical experience and age of the participants was not correlated with performance time, whereas the length of the tracheotomy incision showed a significant correlation (P=0.006).

CONCLUSION

This eFONA training model for children facilitates rapid skill acquisition under realistic anatomical conditions to perform an emergency invasive airway in children younger than 2 yr.

The effect of airway motion and breathing phase during imaging on CFD simulations of respiratory airflow

RATIONALE

Computational fluid dynamics (CFD) simulations of respiratory airflow can quantify clinically useful information that cannot be obtained directly, such as the work of breathing (WOB), resistance to airflow, and pressure loss. However, patient-specific CFD simulations are often based on medical imaging that does not capture airway motion and thus may not represent true physiology, directly affecting those measurements.

OBJECTIVES

To quantify the variation of respiratory airflow metrics obtained from static models of airway anatomy at several respiratory phases, temporally averaged airway anatomies, and dynamic models that incorporate physiological motion.

METHODS

Neonatal airway images were acquired during free-breathing using 3D high-resolution MRI and reconstructed at several respiratory phases in two healthy subjects and two with airway disease (tracheomalacia). For each subject, five static (end expiration, peak inspiration, end inspiration, peak expiration, averaged) and one dynamic CFD simulations were performed. WOB, airway resistance, and pressure loss across the trachea were obtained for each static simulation and compared with the dynamic simulation results.

RESULTS

Large differences were found in the airflow variables between the static simulations at various respiratory phases and the dynamic simulation. Depending on the static airway model used, WOB, resistance, and pressure loss varied up to 237%, 200%, and 94% compared to the dynamic simulation respectively.

CONCLUSIONS

Changes in tracheal size and shape throughout the breathing cycle directly affect respiratory airflow dynamics and breathing effort. Simulations incorporating realistic airway wall dynamics most closely represent airway physiology; if limited to static simulations, the airway geometry must be obtained during the respiratory phase of interest for a given pathology.

Dimensional compatibility of balloon-tipped bronchial blockers with the pediatric airway anatomy using different recommendations for age-related size selection

BACKGROUND

Age-related recommendations for size selection of bronchial blocker devices are based on a few dated anatomical autopsy and radiological studies determining lower airway dimensions in children. These recommendations are based on anterior-posterior internal bronchial diameters, which are smaller than the more relevant lateral internal bronchial diameters.

METHODS

Outer diameters of bronchial blocker balloons inflated with the maximum recommended volume of air were compared to age-related lateral internal bronchial diameters of left and right proximal mainstem bronchi using five different recommendations for age-related size selection of bronchial blocker equipment in children published in the literature.

RESULTS

The ratio of outer bronchial blocker diameters inflated with the maximal recommended volume of air to the median lateral internal diameters of the proximal mainstem bronchus ranged from 71.4% to 181.8% for the left side and from 61.7% to 162.6% for the right side. There were many settings where the blocker diameters did not reach the median lateral internal diameters of the proximal mainstem bronchus. This was more often observed for the right than for the left side (37 vs 22 settings).

CONCLUSION

This analysis demonstrates that irrespective of the recommendation for size selection used, neither the two balloon-tipped vascular catheters included nor the Arndt endobronchial blockers are ideal for lung isolation in children are compared with the age-related relevant dimensions of pediatric airway anatomy. A redesign of bronchial blocker equipment with age-related anatomically based high-volume, low-pressure blocker balloons made from ultrathin membranes and with smaller catheters would be desirable.

A Retrospective Evaluation of Airway Anatomy in Young Children and Implications for One-Lung Ventilation

OBJECTIVE

One-lung ventilation (OLV) in children remains a niche practice with few studies to guide best practices. The objective of this study was to describe lower airway anatomy relevant to establishment of OLV in young children.

DESIGN

Retrospective, observational study using pre-existing studies in the electronic health record.

SETTING

Single institution, academic medical center, tertiary-care hospital.

PARTICIPANTS

Pediatric patients <8 years old.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Chest computed tomographic scans of 111 children 4 days to 8 years of age were reviewed. Measurements were taken from the thyroid isthmus to the carina, carina to first lobar branch on the left and right, diameter of the trachea at the carina, and diameter of the left and right mainstem bronchi. Dimensions were correlated with the outer diameter of endotracheal tubes and bronchial blockers. The left mainstem bronchus is consistently smaller than the right. Lung isolation using a mainstem technique on the left should use an endotracheal tube a half size smaller than would be used for tracheal intubation. The length from the carina to the first lobar branch on the left is consistently 3 times longer than on the right. Further, age-delineated bronchial diameters suggest that the clinician should transition from a 5F to a 7F Arndt bronchial blocker at 3-to-4 years of age.

CONCLUSION

A more detailed and accurate understanding of pediatric lower airway anatomy may assist the clinician in successfully performing OLV in young children.

Cuffed pediatric endotracheal tubes-Outer cuff diameters compared to age-related airway dimensions

BACKGROUND

Reliable sealing of the pediatric airway requires appropriately sized tracheal tube cuffs. The aim of this study was to compare residual cuff diameters of pediatric tracheal tubes with pediatric airway dimensions.

METHODS

Cuff diameters of five different brands of locally marketed pediatric cuffed tracheal tubes with internal diameters of 3.0-7.0 mm were measured at a cuff pressure of 20 cm H₂ O and compared with cuff diameters indicated by their manufacturers. The latter values were compared to tracheal dimensions using the Motoyama and Khine formulas for cuffed tracheal tube size selection.

RESULTS

There is considerable heterogeneity in cuff diameters among pediatric tracheal tube brands, except for two brands from different manufacturers (Halyard and Parker Medical) which were identically designed. Cuffs made from polyurethane revealed fewer differences (91%-118%) between measured and manufacturer-indicated values for outer cuff diameters than did those made from polyvinylchloride (91%-146%). Particularly in smaller sized tracheal tubes, cuffs did not reach 100% of the tracheal lateral diameter, while others were oversized in larger tracheal tubes, independent of the two formulas used for cuffed tracheal tube size selection. Cuff diameters indicated by the manufacturer corresponded to 86%-188% of the median and 68%-157% of the maximum mid-tracheal lateral diameter of the corresponding upper age range.

CONCLUSION

Our findings show that many of the cuff diameters of currently marketed tracheal tube brands lack an age-related anatomical rationale. A proposal for age-related anatomically based cuff diameters is provided for both recommendations for cuffed tracheal tube size selection in children.

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.

Comparisons and Refinements of Neonatal Oro-Tracheal Intubation Length Estimation Methods in Taiwanese Neonates

Objective: This study aimed to evaluate the efficacy of Tochen's formula [TF, body weight (kg) plus 6 cm], nasal septum to ear tragus length (NTL) + 1 cm, and Neonatal Resuscitation Program gestational age (NRP-GA) and body weight (NRP-BW)-based intubation table in estimating the oro-tracheal intubation length, and to improve the estimation efficacy using anthropometric measurements in Taiwanese neonates. Study design: This was a prospective observational study conducted at a neonatal intensive care unit in Taipei, Taiwan. One hundred intubated neonates were enrolled. The estimated intubation depth was defined as being mid-tracheal concordant if it placed the endotracheal tip between the upper border of the first and the lower border of the second thoracic vertebra. A linear regression model was used to analyze the relationships between mid-tracheal depth and body weight (BW), NTL and gestational age (GA), and to revise the NRP intubation tables using our results. Results: Overall, 56% of the neonates were born at a GA ≤ 28 weeks and 48% had a BW ≤ 1,000 g. The overall mid-tracheal concordance rates for TF, NTL + 1 cm, NRP-GA, and NRP-BW estimations were 51.0, 57.0, 15.0, and 14.0%, and in the infants with a BW ≤ 1,000 g 56.3, 56.3, 8.3, and 8.3%, respectively. Our revisions of the NRP intubation tables based on the anthropometric measurements of our participants improved the efficacy of BW, GA, and NTL estimations to 63, 44, and 61%, respectively. Conclusion: TF and NTL + 1 cm were more reliable than NRP intubation tables in predicting the neonatal mid-tracheal length in neonates of all BW and GA. Considering morphological differences secondary to ethnicity, we recommend using these tailored recommendations during neonatal resuscitation in Asian neonates.

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.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

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

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.