Linear airway dimensions in children: including those from cleft palate

New Formula for Depth of Insertion of Endotracheal Tube in Children: A Prospective Observational Study

OBJECTIVES

To assess the correct placement of endotracheal tube (ETT) by confirming it with a flexible fiberoptic bronchoscope (FOB), to propose a new formula that would be suitable for Indian children, and to assess the movement of the ETT tip during neck flexion and extension.

METHODS

A total of 76 patients were included in the study between the age of 2 and 10 y. Depth of ETT insertion was assessed using FOB. ETT migration due to changes in head and neck position was also assessed.

RESULTS

It was observed that 6 out of 76 children had endobronchial/at carina position of ETT after the initial insertion as per the black line guidance in the neutral position. While the incidence was 23, 36, and 36, respectively as per Cole, weight-, and height-based formula.

CONCLUSION

The existing formulae are not suitable for Indian children as their physical stature is different from other ethnic populations. Therefore, the authors suggest a new formula [(Age/2) + 10 cm] for depth of ETT insertion for children of the authors' geographical area.

TRIAL REGISTRATION

CTRI/2015/06/005871.

Recommendations for endotracheal tube insertion depths in children

BACKGROUND

Endotracheal tube (ETT) malposition is frequent in paediatric intubation. The current recommendations for ETT insertion depths are based on formulae that hold various limitations. This study aimed to develop age-based, weight-based and height-based curve charts and tables for ETT insertion depth recommendations in children.

METHODS

In this retrospective single-centre study, we determined the individual optimal ETT insertion depths in paediatric patients by evaluating postintubation radiographic images. Age-based, weight-based and height-based ETT insertion depth recommendations were developed using regression analysis. We compared the insertion depths predicted by the models with previously published formulae.

RESULTS

Intubations of 167 children (0-17.9 years) were analysed. Best-fit curves generated with logistic regression analysis revealed R2 values between 0.784 and 0.880. The insertion depths predicted by the models corresponded well with published age-based and height-based formulae. However, they demonstrated the unsuitability of weight-related linear formulae to predict ETT depth in children.

CONCLUSION

The recommendations developed in this study facilitate a fast and accurate determination of recommended ETT insertion depths in children. Our recommendations provide greater accuracy than previously published formulae and demonstrate that weight-related linear formulae are unsuitable for predicting ETT depth in children.

A new formula based on height for determining endotracheal intubation depth in pediatrics: A prospective study

STUDY OBJECTIVE

The main objective was to devise an endotracheal intubation formula based on pediatric patients' strongly correlated growth parameters. The secondary objective was to compare the accuracy of the new formula to the age-based formula from Advanced Pediatric Life Support Course (APLS formula) and the middle finger length-based formula (MFL-based formula).

DESIGN

A prospective, observational study.

SETTING

Operation.

PATIENTS

111 subjects age 4-12 years old undergoing elective surgeries with general orotracheal anesthesia.

INTERVENTIONS AND MEASUREMENTS

Growth parameters, including age, gender, height, weight, BMI, middle finger length, nasal-tragus length, and sternum length, were measured before surgeries. Tracheal length and the optimal endotracheal intubation depth (D) were measured and calculated by Disposcope. Regression analysis were used to establish a new formula for predicting the intubation depth. A self-controlled paired design was used to compare the accuracy of the intubation depth between the new formula, APLS formula, and MFL-based formula.

MAIN RESULTS

Height (R = 0.897, P < 0.001) was strongly correlated to tracheal length and the endotracheal intubation depth in pediatric patients. New formulae basing on height were established, including new formula 1: D (cm) = 4 + 0.1 × Height (cm) and new formula 2: D (cm) = 3 + 0.1 × Height (cm). Via Bland-Altman analysis, the mean differences for new formula 1, new formula 2, APLS formula and MFL-based formula were - 0.354 cm (95% LOA, -1.289 to 1.998 cm), 1.354 cm (95% LOA, -0.289 to 2.998 cm), 1.154 cm (95% LOA, -1.002 to 3.311 cm), -0.619 cm (95% LOA, -2.960 to 1.723 cm), respectively. The rate of optimal intubation for new formula 1 (84.69%) was higher than for new formula 2 (55.86%), APLS formula (61.26%), and MFL-based formula. (69.37%).

CONCLUSIONS

The prediction accuracy for intubation depth of the new formula 1 was higher than the other formulae. The new formula based on height: D (cm) = 4 + 0.1 × Height (cm) was preferable to APLS formula and MFL-based formula with a high incidence of appropriate endotracheal tube position.

Predicting the risk of inappropriate depth of endotracheal intubation in pediatric patients using machine learning approaches

Endotracheal tube (ET) misplacement is common in pediatric patients, which can lead to the serious complication. It would be helpful if there is an easy-to-use tool to predict the optimal ET depth considering in each patient's characteristics. Therefore, we plan to develop a novel machine learning (ML) model to predict the appropriate ET depth in pediatric patients. This study retrospectively collected data from 1436 pediatric patients aged < 7 years who underwent chest x-ray examination in an intubated state. Patient data including age, sex, height weight, the internal diameter (ID) of the ET, and ET depth were collected from electronic medical records and chest x-ray. Among these, 1436 data were divided into training (70%, n = 1007) and testing (30%, n = 429) datasets. The training dataset was used to build the appropriate ET depth estimation model, while the test dataset was used to compare the model performance with the formula-based methods such as age-based method, height-based method and tube-ID method. The rate of inappropriate ET location was significantly lower in our ML model (17.9%) compared to formula-based methods (35.7%, 62.2%, and 46.6%). The relative risk [95% confidence interval, CI] of an inappropriate ET location compared to ML model in the age-based, height-based, and tube ID-based method were 1.99 [1.56-2.52], 3.47 [2.80-4.30], and 2.60 [2.07-3.26], respectively. In addition, compared to ML model, the relative risk of shallow intubation tended to be higher in the age-based method, whereas the risk of the deep or endobronchial intubation tended to be higher in the height-based and the tube ID-based method. The use of our ML model was able to predict optimal ET depth for pediatric patients only with basic patient information and reduce the risk of inappropriate ET placement. It will be helpful to clinicians unfamiliar with pediatric tracheal intubation to determine the appropriate ET depth.

Ideal Depth of Endotracheal Intubation at the Vocal Cord Level in Pediatric Patients Considering Racial Differences in Tracheal Length

Numerous formulas that can predict endotracheal intubation depth at the corner of the mouth or the nasal wing of patients have been reported, even though the oral and nasal cavity anatomies differ among patients. Therefore, the purpose of this study was to derive a simple and reliable formula to predict the ideal endotracheal tube insertion depth at the vocal cord level in pediatric patients. The current study was conducted as a retrospective observational study, involving 425 and 335 cardiac pediatric patients in Germany and Japan, respectively, and aimed to determine a formula for predicting tracheal length and ideal depth of endotracheal intubation at the vocal cord level in pediatric patients. The distance between the vocal cords and the carina tracheae was defined as the tracheal length, and was measured on preoperative chest radiographs obtained in the supine position. The tracheal length in cardiac pediatric patients ranged from 6 to 10% of the body height in Germany and from 7 to 11% in Japan. This study revealed racial differences in the tracheal length, that is, in the ideal depth of endotracheal intubation at the vocal cord level. This study suggests that an adequate endotracheal intubation depth can be achieved by inserting endotracheal tubes at the vocal cord level with the minimum tracheal length of each racial group in pediatric patients, for example, 6% and 7% of the body height in Europeans and Asians, respectively. If the endotracheal tube inserted with this method appears to be shallow on chest radiographs, this does not represent an increased risk of accidental extubation, due to an excessively short intubation depth, because the minimum tracheal length for each racial group is considered. That is, it is not due to the endotracheal tube insertion length, but is likely due to the tracheal length of the patient, who has a relatively long tracheal length in the racial group.

Effect of head position changes on the depth of tracheal intubation in pediatric patients: A prospective, observational study

PURPOSE

The purpose of this study was to investigate the effect of changing head position on the endotracheal tube (ETT) depth and to assess the risk of inadvertent extubation and bronchial intubation in pediatric patients.

METHODS

Subjects aged 4-12 years old with orotracheal intubation undergoing elective surgeries were enrolled. After induction, the distances between "the ETT tip and the trachea carina" (T-C) were measured using a Disposcope flexible endoscope in head neutral position, 45° extension and flexion, 60° right and left rotation. The distance of the ETT tip movement relative to the neutral position (ΔT-C) was calculated after changing the head positions. The direction of the ETT tip displacement and the adverse events including endobronchial intubation, accidental tracheal extubation, hoarseness and sore throat were recorded.

RESULTS

The ETT tip moved toward the carina by 0.5 ± 0.4 cm (P < 0.001) when the head was flexed. After extending the head, the ETT tip moved toward the vocal cord by 0.9 ± 0.4 cm (P < 0.001). Right rotation resulted that the ETT tip moved toward the vocal cord direction by 0.6 ± 0.4 cm (P < 0.001). Moreover, there was no displacement with the head on left rotation (P = 0.126). Subjects with the reinforced ETT had less ETT displacement after changing head position than the taper guard ETT.

CONCLUSION

The changes of head position can influence the depth of the ETT especially in head extension. We recommend using the reinforced ETT to reduce the ETT displacement in pediatrics to avoid intubation complications.

CLINICAL TRIAL REGISTRATION

[www.ClinicalTrials.gov], identifier, [ChiCTR2100042648].

Accuracy of predictive equations in guiding tracheal intubation depth in children: A prospective study

BACKGROUND

Accurate insertion depth of endotracheal tube (ETT) in children has been predicted using the demographic variables, such as age, weight, and height. Middle finger length showed good correlation with ETT depth measurement in children aged 4-14 years.

AIMS

The primary objective was to correlate the actual ETT insertion depth with the depth derived from middle finger length, age, weight, and height formulae in children aged 1-4 years. The secondary objective was to find the most accurate formula for prediction of ETT insertion depth.

METHODS

This prospective parallel group study was done in 50 american society of anesthesiologists 1 or 2 children aged 1-4 years undergoing elective surgery under general anesthesia. Children with difficult airway, finger anomalies, or syndromic associations were excluded. Age, weight, height, and middle finger length of all children were measured. Depth of orally inserted uncuffed ETT and tracheal length was measured by fiberoptic bronchoscopy. The actual ETT depth was correlated with the depth calculated from different formulae.

RESULTS

The mean middle finger length was 4.42 ± 0.50 cm, age was 2.64 ± 1.07 years, weight was 12.28 ± 2.84 kg, and height was 82.89 ± 16.23 cm. The mean tracheal length was 6.42 ± 0.96 cm. The mean depth of ETT was actual depth (12.89 ± 1.09 cm), middle finger depth (13.23 ± 1.53cm; p = .001; 95%CI 0.12-0.50), age-based depth 1(3.31 ± 0.53 cm; 95%CI 0.37-1.44; p = .001), weight-based depth (14.14 ± 1.42 cm; 95% CI 0.10-0.51; p = .004), and height-based depth (13.73 ± 0.94 cm; 95% CI 0.15-0.77; p = .004). Middle finger length and age-based formulae showed higher number of accurate placements (58% each). Weight- (74%) and height (64%)-derived formulae gave a higher number of distal ETT placements.

CONCLUSION

Formulas based on the demographic variables and middle finger length showed good correlation with the actual ETT depth in children aged 1-4 years. The percentage of accurate ETT depth placements was higher with middle finger length and age-based formulae.

Endotracheal tube cuff position in relation to the cricoid in children: A retrospective computed tomography-based analysis

Background:

The use of cuffed endotracheal tubes (ETT) has become the standard of care in pediatric practice. The rationale for the use of a cuffed ETT is to minimize pressure around the cricoid while providing an effective airway seal. However, safe care requires that the cuff lie distal to the cricoid ring following endotracheal intubation. The current study demonstrates the capability of computed tomography (CT) imaging in identifying the position of the cuff of the ETT in intubated patients.

Methods:

In this retrospective study, the ETT cuff position was examined on the sagittal plane images of neck and chest CT scans of 44 children. The position of the proximal and the distal aspect of the ETT cuff inside the trachea was recorded in relation to the vertebral levels. The vertebral levels were used to estimate the location of the cricoid ring and its relationship to the cuff.

Results:

The vertebrae were used as the primary landmarks to define the position of the cricoid and its relationship to the cuff of the ETT. Correlating vertebral levels with the cricoid for different age groups, the proximal (cephalad) edge of the ETT cuff was below the cricoid in 41 of 44 patients (93%). The ETT cuff was deep in 6 patients, below the 1^st thoracic vertebra, with 2 ETTs in the right mainstem bronchus.

Conclusion:

This is the first study demonstrating that the cuff of the ETT and its position in the trachea can be identified on CT imaging in children. The ETT cuff was below the level of the cricoid in the majority of patients irrespective of the patient's age as well as the size, make, and type of ETT.

Machine learning model for predicting the optimal depth of tracheal tube insertion in pediatric patients: A retrospective cohort study

Objective

To construct a prediction model for optimal tracheal tube depth in pediatric patients using machine learning.

Methods

Pediatric patients aged <7 years who received post-operative ventilation after undergoing surgery between January 2015 and December 2018 were investigated in this retrospective study. The optimal location of the tracheal tube was defined as the median of the distance between the upper margin of the first thoracic(T1) vertebral body and the lower margin of the third thoracic(T3) vertebral body. We applied four machine learning models: random forest, elastic net, support vector machine, and artificial neural network and compared their prediction accuracy to three formula-based methods, which were based on age, height, and tracheal tube internal diameter(ID).

Results

For each method, the percentage with optimal tracheal tube depth predictions in the test set was calculated as follows: 79.0 (95% confidence interval [CI], 73.5 to 83.6) for random forest, 77.4 (95% CI, 71.8 to 82.2; P = 0.719) for elastic net, 77.0 (95% CI, 71.4 to 81.8; P = 0.486) for support vector machine, 76.6 (95% CI, 71.0 to 81.5; P = 1.0) for artificial neural network, 66.9 (95% CI, 60.9 to 72.5; P < 0.001) for the age-based formula, 58.5 (95% CI, 52.3 to 64.4; P< 0.001) for the tube ID-based formula, and 44.4 (95% CI, 38.3 to 50.6; P < 0.001) for the height-based formula.

Conclusions

In this study, the machine learning models predicted the optimal tracheal tube tip location for pediatric patients more accurately than the formula-based methods. Machine learning models using biometric variables may help clinicians make decisions regarding optimal tracheal tube depth in pediatric patients.

Length of the Cricoid and Trachea in Children: Predicting Intubation Depth to Prevent Subglottic Stenosis

OBJECTIVE

Define the length of the subglottis and trachea in children to predict a safe intubation depth.

METHODS

Patients <18 years undergoing rigid bronchoscopy from 2013 to 2020 were included. The carina and inferior borders of the cricoid and true vocal folds were marked on a bronchoscope and distances were measured. Patient age, weight, height, and chest height were recorded. Four styles of cuffed pediatric endotracheal tubes (ETT) were measured and potential positions of each cuff and tip were calculated within each trachea using five depth of intubation scenarios. Multivariate linear regression was performed to identify predictors of subglottic and tracheal length.

RESULTS

Measurements were obtained from 210 children (141 male, 69 female), mean (SD) age 3.21 (3.66) years. Patient height was the best predictor of subglottic length (R² : 0.418): Length_sg (mm) = 0.058 * height (cm) + 2.8, and tracheal length (R² : 0.733): Length_t (mm) = 0.485 * height (cm) + 21.3. None of the depth of intubation scenarios maintained a cuff-free subglottis for all ETT styles investigated. A formula for depth of intubation: Length_di (mm) = 0.06 * height (cm) + 8.8 found that no ETT cuffs would be in the subglottis and all tips would be above the carina.

CONCLUSION

Current strategies for determining appropriate depth of intubation pose a high risk of subglottic ETT cuff placement. Placing the inferior border of the vocal cords 0.06 * height (cm) + 8.8 from the superior border of the inflated ETT cuff may prevent subglottic cuff placement and endobronchial intubation.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

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.

Does the endotracheal tube insertion depth predicted by formulas in children have a good concordance with the ideal position observed by X-ray?

Objective

To evaluate the effectiveness of the different formulas for estimating the insertion depth of an endotracheal tube in children.

Methods

This was an observational and cross-sectional study that included children between 29 days and 2 years of age who were hospitalized in a pediatric intensive care unit and mechanically ventilated. The formulas based on height [(height/10) + 5], the inner diameter of the tube (endotracheal tube × 3), and weight (weight + 6) were evaluated to determine which of them showed better concordance with the ideal insertion depth of the endotracheal tube as evaluated by X-ray.

Results

The correlation between the height-based calculation and the ideal depth observed on X-ray was strong, with r = 0.88, p < 0.05, and a concordance correlation coefficient of 0.88; the correlation between the weight-based calculation and depth on X-ray was r = 0.75, p < 0.05, and concordance correlation coefficient 0.43; and the correlation between endotracheal tube diameter-based calculation and depth on X-ray was r = 0.80, p < 0.05, and concordance correlation coefficient 0.78. Lin’s concordance correlation analysis indicated that the measurements showed weak concordance (< 0.90).

Conclusion

The formulas that estimate the insertion depth of the endotracheal tube in children were not accurate and were discordant with the gold-standard method of X-ray evaluation. There is a need for a new method based on anthropometric variables (weight and height) and age that is effective in guiding health professionals of pediatric intensive care units at the time of intubation.

Choosing endotracheal tube size in children: Which formula is best?

OBJECTIVES

Various formulae have been suggested to calculate the appropriate sized endotracheal tube in children. The current study prospectively compares three commonly used formulae for selection of cuffed endotracheal tubes in children.

METHODS

Patients were randomized to one of three formulae (Duracher, Cole, or Khine) to determine the size of the cuffed endotracheal tube for endotracheal intubation. The fit of the tube was noted and intracuff pressure was measured using a manometer. The postoperative incidence of stridor, throat pain/soreness, and hoarseness was noted in the post-anesthesia care unit at 2, 4 and 24 h after the procedure.

RESULTS

The study cohort included 135 patients less than or equal to 8 years, equally divided into three groups based on age, weight, and gender. There was no difference in the intracuff pressure, the volume required to seal the airway, or the number of times in which the intracuff pressure was greater than or equal to 20 or 30 cm H₂O among the three groups. Six tube changes were required in the Cole group while no tube changes were required in the Duracher group (p < 0.05). The postoperative incidence of adverse events (throat pain, hoarseness, and stridor) at 0-2 h, 2-4 h, and 24 h was higher in the Cole group when compared to the Duracher group.

CONCLUSION

When using an endotracheal tube with a polyurethane cuff, the Duracher formula provided the best estimate for choosing the correct size.

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.

New decision formulas for predicting endotracheal tube depth in children: analysis of neck CT images

INTRODUCTION

The purpose of this study was to construct a prediction model for endotracheal tube depth using neck CT images.

METHODS

A retrospective image review was conducted that included patients who had undergone neck CT. Using sagittal neck CT images, we calculated the length between upper incisor and mid-trachea and then derived the model via regression analysis. The model was validated externally using chest radiographs of patients who had undergone endotracheal intubation. We compared performance of our model with that of other methods (Broselow tape and APLS formula) via Bland-Altman analysis and the percentage of estimations within 10% of the measured values.

RESULTS

A total of 1111 children were included in this study. The tube depth obtained from CT images was linearly related to body weight (tube depth (cm)=5.5+0.5×body wt (kg)) in children younger than 1 year and to height (tube depth (cm)=3+0.1×height (cm)) in children older than 1 year. External validation demonstrated that our new model showed better agreement with the desired tube depth than Broselow tape and APLS formula. The mean differences in children younger than 1 year were 0.61 cm and -1.24 cm for our formula and Broselow tape, respectively. The mean differences in children older than 1 year were -0.43 cm, -1.98 and -1.64 cm for our formula, Broselow tape and APLS formula, respectively. The percentages of estimates within 10% of the measured values were 52.7% and 35.8% for our formula and Broselow tape in children younger than 1 year, respectively, and 54.3%, 33.8% and 37.2% for our formula, Broselow tape and APLS formula in children older than 1 year, respectively (P<0.01).

CONCLUSION

Our new formula is useful and more accurate than the currently available methods.

The Tracheal Accordion and the Position of the Endotracheal Tube

The purpose of this review is to, first, determine the static factors that affect the length of the human trachea across different populations and, second, to investigate whether or not there are dynamic factors that cause the length of the human trachea to vary within the same individual. We also investigated whether these changes in tracheal length within the same individual are significant enough to increase the risk of endobronchial intubation or accidental extubation. A PubMed/MEDLINE and a Web of Science database English-language literature search was conducted in May 2016 with relevant keywords and MeSH terms when available. We found that gender, extremes of age, patient height, postsurgical changes and co-existing disease are static patient factors that affect the length of the human trachea. Dynamic clinical changes that occur under anaesthesia, including Trendelenburg position, head and neck flexion and extension, paralysis of the diaphragm and pneumoperitoneum, cause the trachea to act as an accordion, decreasing and increasing its length. The length of the human trachea in both awake and anaesthetised and paralysed patients is a critical consideration in preventing both endobronchial intubation and tracheal extubation. It is clear from the literature that tracheal length varies widely across populations and, additionally, with the dynamic clinical changes that occur under anaesthesia, the trachea acts as an accordion decreasing and increasing its length within the same individual. Knowledge of the magnitude of the change in tracheal dimensions in response to these factors is an important clinical consideration.

Accuracy of a Chest X-Ray-Based Method for Predicting the Depth of Insertion of Endotracheal Tubes in Pediatric Patients Undergoing Cardiac Surgery

OBJECTIVES

The incidence of endotracheal tube (ETT) malposition in children with various described methods is 15% to 30%. Chest x-ray (CXR) is the gold standard for confirming appropriate ETT position. The aim of this study was to measure the accuracy of a preoperative CXR-based method in determining depth of insertion of ETTs and to compare it with methods based on the intubation depth mark or formulae (age, height, and ETT internal diameter) in children undergoing cardiac surgery.

DESIGN

Prospective observational study.

SETTING

University-affiliated tertiary care hospital.

PARTICIPANTS

Sixty-six consecutive children scheduled for elective pediatric cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The distance from carina to mid-trachea was measured for each child preoperatively on the CXR displayed as a computed radiography image in a picture archival and communications system computer. Following intubation, ETTs deliberately were pushed endobronchially and then pulled back to the carina; they were further withdrawn by the previously measured carina to mid-tracheal distance and secured. CXRs postoperatively were repeated to confirm ETT position. The ETT position was measured with other methods using the picture archival and communications system ruler on the postoperative CXR and compared with the CXR method. The proportion of appropriate ETT position with the CXR method was 98.5% (p≤0.001 v other methods). In children younger than 3 years, the appropriate proportion was 97.4%.

CONCLUSION

The appropriate positioning of ETTs in the trachea by the CXR method is superior to other methods.

Nares-to-carina distance in children: does a 'modified Morgan formula' give useful guidance during nasal intubation?

BACKGROUND

Knowledge of the normal nares-to-carina (NC) distance might prevent accidental bronchial intubation and be helpful when designing preformed endotracheal tubes (ETT).

OBJECTIVE

The aim was to measure NC distance and to examine whether a height/length-based 'modified Morgan formula' would give useful guidance for nasotracheal ETT depth positioning.

METHODS

Two groups were studied. A younger group consisted of nasally intubated postoperative patients. In these, NC distance was obtained as the sum of ETT length and the distance from the ETT tip to the carina, as measured from an anteroposterior chest X-ray. An older group consisted of children who had undergone computerized tomography (CT) examination including head, neck, and chest. In these, NC was measured directly from the CT image. The modified Morgan formula was derived from the NC vs height/length relationship.

RESULTS

Nares-to-carina distance was best predicted by a linear equation based on patient height. The equation in the younger group (1 day-8 years, n = 57) was: NC (cm) = 0.14 × height + 5.8, R(2) = 0.90, and in the older group (2.1-20 years, n = 45): NC (cm) = 0.15 × height + 3.4, R(2) = 0.93. The equation for the groups combined (n = 102) was: NC (cm) = 0.14 × height + 6.2, R(2) = 0.97. Based on the latter equation, a modified Morgan formula was identified as: ETT position at nares in cm = 0.12 × height + 5. If the ETT had been placed as calculated by this formula, the ETT tip would have been at 85 + 5% (mean ± sd) of NC distance, and the ETT tip-to-carina distance would have been 3.1 ± 1.1 cm (range 0-6.6). Bronchial intubation would not have occurred in any child, but a comparison to tracheal length measurements indicates that ETT tip position could be too proximal in some children.

CONCLUSION

The study confirms previous reports: NC distance can be well predicted from height/length. A modified Morgan formula might decrease the risk for accidental endobronchial intubation in infants and children, but ETT position need to be confirmed by auscultation or other verification.

Three-finger tracheal palpation to guide endotracheal tube depth in children

BACKGROUND

Accurate endotracheal tube (ETT) depth is critical, especially in children. The current tools used to guide appropriate ETT depth have significant limitations.

OBJECTIVES

To evaluate the utility of tracheal palpation in the neck to guide appropriate ETT placement in children.

METHODS

A prospective observational study with a convenience sample of 50 children was conducted. During intubation, an investigator palpated the trachea with three fingertips side-by-side extending upward from the suprasternal notch. The anesthesiologist advanced the ETT slowly until palpated at the sternal notch. The investigator stated ETT palpation certainty as 'strongly felt', 'weakly felt', or 'not felt.' Final ETT position was determined by bronchoscopy and categorized as 'ETT too shallow' (tip in proximal ¼ of trachea), 'ETT too deep' (tip in distal ¼ of trachea), or 'ETT placement satisfactory' (between those extremes).

RESULTS

Thirty boys and 20 girls undergoing dental surgery with nasal intubation were recruited (median age 4.4 years; range 2.0-10.8). The ETT (all ≥4 mm ID) was palpable at the sternal notch in all patients: 46 of 50 strongly palpable and 4 of 50 weakly palpable. The experimental methods led to satisfactory ETT placement in 49 of 50 patients, too deep in 1 of 50 patients. Compared with the Pediatrics Advanced Life Support (PALS) predictive formula, satisfactory placement would have been 41 of 50 patients (P < 0.008). Number needed to treat is 6.3 for improvement over the PALS method.

CONCLUSIONS

The use of tracheal palpation to guide ETT placement has excellent clinical performance and better guides appropriate ETT depth than the PALS formula in our study population.

Assessment of airway length of Korean adults and children for otolaryngology and ophthalmic surgery using a fiberoptic bronchoscope

Background

Knowledge regarding normal upper airway anatomy is essential for airway management and is required to prevent malpositioning of endotracheal tubes. We evaluated the length of the upper airway in Korean children and adults who had no abnormality of the upper airway using a fiberoptic bronchoscope.

Methods

Eighty seven patients aged 5 to 81 years undergoing noninvasive elective surgery were included in this study. After induction of anesthesia was complete, we measured the distance from the upper incisor to various components of the upper airway by fiberoptic bronchoscopy.

Results

In adults, the mean length between the upper incisor and midtrachea was found to be 21.8 ± 1.8 cm in males and 19.9 ± 1.3 cm in females, while the mean length of the trachea was 10.1 ± 1.3 cm in males and 10.3 ± 1.6 cm in females. The length between the upper incisor and midtrachea (IT) were correlated with height both in children (IT [cm] = 2.531 + 0.109 × height [cm]) and adults (IT [cm] = 0.167 + 0.127 × height [cm]), which shows that they differ from the western standard (length of tube [cm] = 5 + 0.1 × height [cm]).

Conclusions

In adults and children, the length from the incisor to the midtrachea was significantly different when compared with western standards. Therefore, re-evaluation of the proper and precise depth of endotracheal tube in Koreans should be considered.

Pediatric laryngoscope blade size selection using facial landmarks

OBJECTIVES

The study evaluates whether facial landmarks can be used to estimate an appropriate laryngoscope blade length for oral endotracheal intubation in children. We tested the hypothesis that the laryngoscope blade measuring 10 mm or less distal or proximal to the angle of the mandible (when the flat portion of the blade follows the facial contour from the upper incisor teeth to the angle of the mandible) will demonstrate greater success and ease of oral tracheal intubation.

METHODS

We performed an observational study that prospectively evaluated a convenience sample of children 8 years old or younger and who were undergoing direct laryngoscopy for oral endotracheal intubation in the operating room, outpatient surgery center, emergency department, or pediatric intensive care unit of a tertiary referral medical center. Ease and success of oral tracheal intubation were compared with distance measurements from the angle of the mandible to the tip of the laryngoscope blade.

RESULTS

Blade lengths considered too short (blade lengths >10 mm proximal to the angle of the mandible) were more likely to be associated with more than 1 attempt at intubation. Only 57.1% (12/21; 95% confidence interval [CI], 36.5-75.5) of the intubations using the shorter blade were performed on the first attempt as compared with 89.7% (26/29; 95% CI, 73.6-96.4) of the intubations using the recommended length or 85.7% (6/7; 95% CI, 48.7-97.4) of the intubations using blades extending longer than 10 mm past the angle of the mandible.

CONCLUSIONS

The distance from the upper incisor teeth to the angle of the jaw seems to be an excellent clinical landmark for laryngoscope blade length selection for pediatric intubations. When the blade (excluding the handle insertion block) is placed at the upper midline incisor teeth and the tip is located within 1 cm proximal or distal to the angle of the mandible, oral tracheal intubations are more consistently accomplished on the first attempt. Our observations suggest that facial landmarks can be used to estimate an appropriate laryngoscope blade length for oral endotracheal intubation in children.

Prospective assessment of guidelines for determining appropriate depth of endotracheal tube placement in children

OBJECTIVE

To determine whether multiplying the internal diameter of the endotracheal tube (ETT) by 3 (3x ETT size) is a reliable method for determining correct depth of oral ETT placement in the pediatric population.

DESIGN

Prospective, observational.

SETTING

University-affiliated, 12-bed pediatric intensive care unit.

PATIENTS

Orally intubated pediatric intensive care unit patients of < or =12 yrs of age.

INTERVENTIONS

Demographics, ETT size, and depth of ETT placement measured from the lip were obtained. Correct placement, defined as the tip of the ETT below the thoracic inlet and > or =0.5 cm above the carina, was determined by chest radiograph.

MEASUREMENTS AND MAIN RESULTS

Suggested ETT size based on the Pediatric Advanced Life Support (PALS) age-based formula and the Broselow tape-length-based guidelines were determined. A total of 174 of 226 ETTs (77%) were correctly positioned. If practitioners utilized the 3x ETT size for the actual tubes chosen, 170 of 226 (75%) would have been accurately placed. More accurate were the 3x PALS-based ETT size (81%) and 3x Broselow-suggested ETT size (85%). The use of the Broselow ETTs to determine the depth would have led to a significantly improved ETT position (p = .009) compared with the actual ETT.

CONCLUSION

The commonly used formula of 3x tube size for ETT depth in children results in 15-25% malpositioned tubes. Practitioners can improve the reliability of this formula by utilizing the recommended ETT size as suggested by the Broselow tape. A more reliable method is necessary to avoid ETT malposition.

Prediction of tracheostomy tube size for paediatric long-term ventilation: an audit of children with spinal cord injury

BACKGROUND

There are no published data to predict tracheostomy tube size as growth proceeds in children requiring long-term ventilation.

METHODS

A retrospective audit was undertaken of children having long-term ventilation, managed from the Southport spinal injuries unit. The dates of step-up in size of tracheostomy tube were noted together with the tube inside and outside diameters (ID and OD) and the lateral tracheal diameter. The data were aggregated for each increment in tube size to calculate the Pearson correlation coefficients for age and weight of the children. Linear regression was then used to generate predictive equations based on age and weight.

RESULTS

Out of 12 children, data from seven boys and two girls, with a mean age of 5.9 (range 1.5-13.75) yr, were obtained. Average length of follow-up was 7 yr, with an average of 3.5 tube changes per patient equating to a larger tube every 2 yr. The inside and outside tracheal tube diameters, as well as the lateral tracheal diameter, correlated significantly with age and weight (P<0.01). The appropriate tracheostomy tube internal diameter is conveniently expressed by the formula: ID mm=age yr/3 + 3.5

CONCLUSIONS

The step-up in size of the tracheostomy tube as growth proceeds should be undertaken as a planned procedure at least every 2 yr to avoid nocturnal desaturation. Age appears to be a convenient and reliable predictor.

Effect of head posture on tracheal tube position in children

Changes in the tracheal tube tip to carina distance were measured by radiographic screening following various head postures in 45 children undergoing cardiac catheterisation under general anaesthesia who were intubated via nasal and oral routes. Extension of the head moved the tracheal tube away from the carina and flexion moved it towards the carina in both routes. Endobronchial intubation was noted during neck flexion in a significant proportion of children intubated orally but none occurred during nasal intubation. Extension produced greater upward movement of the tracheal tube tip in the oral route than the nasal route. In contrast, flexion produced greater downward movement in the nasal route in some patients. The direction of movement with lateral rotation and use of a shoulder roll was inconsistent.

The airway in patients with craniofacial abnormalities

Airway management for patients with craniofacial disorders poses many challenges. The anaesthesiologist must be familiar with the normal bony and soft-tissue anatomy in the airway and how anatomy is altered by various congenital disorders. Specific areas to assess include the oral cavity, anterior mandibular space, maxilla, temporomandibular joint and vertebral column. Congenital conditions that may alter normal anatomy and therefore anaesthetic management include cleft lip and palate with or without Pierre Robin syndrome, craniofacial dysostosis, mandibulofacial dysostosis/Treacher Collins syndrome, hemifacial microsomia, Klippel-Feil syndrome, Beckwith-Wiedemann syndrome, trisomy 21/Down's syndrome, Freeman-Sheldon/whistling face syndrome/craniocarpotarsal dysplasia, fibrodysplasia ossificans progressiva, mucopolysaccharidosis and vascular malformations.

The intubation depth marker: the confusion of the black line

BACKGROUND

Estimation of the correct depth of insertion of a tracheal tube (TT) in children is extremely important. Insertion of an excessive length may result in endobronchial intubation while an inadequate length of insertion may lead to accidental extubation.

METHODS

We reviewed TTs commonly used in paediatric practice and also reviewed recommended guidelines for correct depth of insertion.

RESULTS

Amongst the different brands of TTs used, there was a wide discrepancy in the placement of the intubation depth marker. This is important as the intubation depth marker is often used as a guideline for intubation.

CONCLUSIONS

For optimal placement we can rely on various formulae and manufacturers' markings on the TTs. Clinical judgement, however, remains the cornerstone of optimal placement.

Tracheal length of infants under three months old

The measurement of tracheal length in infants is difficult to perform in vivo. In adults, tracheal length may be consistent with age, but in infants, tracheal length may vary much more with age and other factors. This study used video rigid ventilation bronchoscopy to evaluate the length of the airway, concentrating on the population younger than 3 months old. There were 34 infants in this study: 14 boys and 20 girls. The mean length from the superior border of the vocal fold to the carina was 5.04 cm, and the mean tracheal length (from the ridge of the first tracheal ring to the carina) was 4.12 cm. There was no significant difference between boys and girls in the length from the vocal fold to the carina or in the tracheal length. The length from the vocal fold to the carina is best correlated to body weight, followed by body height and age.

Reduction in tracheal lumen due to endotracheal intubation and its calculated clinical significance

BACKGROUND

The flow in the human trachea is turbulent. Thus, the tracheal resistance (R) and the pressure gradient (DeltaP) required to maintain a given flow across the trachea is inversely related to its radius raised to the fifth power. If the caliber reduction ratio (X) after endotracheal intubation is calculated as X = radius of the endotracheal tube (rETT)/radius of the trachea (rT), then DeltaP and/or R will be increased by (1/X)(5).

STUDY OBJECTIVES

To measure the actual ratio between rETT and rT following endotracheal intubation of pediatric patients with respiratory failure and to calculate the resulting increase in the tracheal R and DeltaP for a given inspiratory flow rate.

DESIGN

Retrospective chart review.

SETTING

Pediatric ICU in a tertiary-care teaching children's medical center. PATIENT ENROLLMENT: Twenty consecutive pediatric patients (mean [+/- SD] age, 6.4 +/- 7.2 years) whose tracheas had been intubated for various causes of respiratory failure, and who had received a CT scan, were included in our study. All patients received an endotracheal tube the size of which was derived from the following formula: (age in years/4) + 4.

MEASUREMENTS AND MAIN RESULTS

rT and rETT were measured from CT scan sections at and around the level of the thoracic inlet, and the average values were used to calculate X. These values ranged from 0.33 to 0.65 (mean, 0. 55 +/- 0.8). The factor (1/X)(5) was calculated for each patient and then was multiplied by the known normal value for tracheal R for adolescents and adults (0.07 cm H(2)O/L/s) to obtain the value of R resulting from the artificial airway, (1/X)(5) x 0.07. Our results showed that tracheal R increased due to caliber reduction of the trachea after endotracheal intubation by 33.9 +/- 52.5-fold (range, 8.6- to 255.5-fold). In order to maintain an inspiratory flow of 1 L/s, the value of P for the intubated trachea would increase from 0. 07 cm H(2)O to a mean of 2.4 +/- 3.7 cm H(2)O (range, 0.6 to 18 cm H(2)O). In two of our patients, the rT/rETT ratios were < 0.5 (0.33 and 0.44, respectively); this translated into a more significant increase in the calculated DeltaPs, 18 and 4.2 cm H(2)O, respectively.

CONCLUSIONS

: The common value of X due to endotracheal intubation is between 0.5 and 0.6, which in and of itself results in an increase in R across the intubated trachea up to 32-fold. The calculated increase in P as a result of this is between 2 and 3 cm H(2)O for adolescents or young adults. The addition of pressure support of at least 3 cm H(2)O during spontaneous ventilation via an endotracheal tube, which is common practice in pediatric critical care, should alleviate any respiratory distress emanating from the increased R. However, a value for X < 0.5, which was found in 10% of our patients (2 of 20 patients), results in a much higher calculated increase in the pressure gradient and, therefore, a higher level of pressure support is required to overcome this increase.

Dimensions of the trachea to age 6 years related to height

In an effort to establish normal values for both investigational and patient care purposes, computed tomography was used to determine the length, diameters, cross-sectional area, and volume of the tracheas of 34 children up to the age of 6 years. The measurements were taken when patients were asleep or resting quietly during tidal breathing, at perhaps 30-60% of total lung capacity. The results were related to body height (in infancy, to body length). There was virtually no difference between boys and girls. Each mean diameter correlated well with mean cross-sectional area. Tracheal diameters and area were reasonably constant over the length of individual tracheas. The slopes of the functions relating height to tracheal dimensions in these 34 infants and young children were slightly less steep than those previously measured near total lung capacity in 90 older children and adolescents.

Fundamentals of infant anaesthesia

Far from being more difficult, infants should be less difficult to anaesthetize . Generally the major organ systems, although not necessarily fully mature, are unsullied by smoking, alcohol consumption, atherosclerosis, assorted other pathology or simple wear and tear. Cardiac output is linked to heart rate and volume replacement, while oxygenation is controlled by lung expansion, FIO2 and perhaps PEEP. Admittedly, the rewards for poor technique are frightening and sudden, but the goal of this review has been to point out the anticipatory nature of paediatric anaesthesia, such that the actual anaesthetic becomes nearly an anti-climax. The rewards for this approach are usually brief procedures that frequently definitively repair isolated pathology, coupled with a sense of precise accomplishment that makes the planning and number- crunching worthwhile.