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

Infant bronchial tree simulator: Success of a built-from-scratch model for single lung isolation

BACKGROUND

One-lung ventilation in infants is a high-risk procedure. Complications include endotracheal tube occlusion, with grave consequences. Although there are commercially available bronchoscopy simulators, there are no realistic models of infant patients. This limits access to training opportunities that would ensure safe and efficient lung isolation. To bridge this gap, we developesd a realistic infant bronchial tree model for single lung intubation and evaluated preliminary validity evidence of its features and clinicians' ability to perform critical skills associated with pediatric one-lung ventilation.

METHODS

Using computed tomography imaging, a stereolithography file of an infant airway was generated to 3D print a model. This model was inserted into a commercially available airway trainer to allow lung isolation using standard bronchoscopy techniques. Ten experienced pediatric anesthesiologists independently evaluated the simulator's physical attributes, realism, value, and relevance using a 29-item paper survey and rated using 4-point rating scales (4 = highest). Participants' ability to complete 5 critical tasks was self-reported using 5-point rating scales (5 = too easy). Item and domain mean ratings were calculated, and comments reviewed.

RESULTS

Overall, reviews were positive, with mean scores indicating adequate realism and high value. Specific challenges were associated with right mainstem bronchus and upper lobe takeoff. Performance scores indicated that most tasks were "somewhat easy to perform," suggesting that the model's anatomy did not hinder physicians' ability to perform one-lung ventilation.

CONCLUSION

Preliminary findings indicate that the novel simulator holds promise for training in lung isolation techniques after refinement. Future research will target refinement, expanding evaluation, and developing a comprehensive curriculum and competency assessment program.

Error traps in pediatric one-lung ventilation

With the advent of thoracoscopic surgery, the benefits of lung isolation in children have been increasingly recognized. However, because of the small airway dimensions, equipment limitations in size and maneuverability, and limited respiratory reserve, one-lung ventilation in children remains challenging. This article highlights some of the most common error traps in the management of pediatric lung isolation and focuses on practical solutions for their management. The error traps discussed are as follows: (1) the failure to take into consideration relevant aspects of tracheobronchial anatomy when selecting the size of the lung isolation device, (2) failure to execute correct placement of the device chosen for lung isolation, (3) failure to maintain lung isolation related to surgical manipulation and isolation device movement, (4) failure to select appropriate ventilator strategies during one-lung ventilation, and (5) failure to appropriately manage and treat hypoxemia in the setting of one-lung ventilation.

Hypoxemia in Young Children Undergoing One-lung Ventilation: A Retrospective Cohort Study

BACKGROUND

One-lung ventilation in children remains a specialized practice with low case numbers even at tertiary centers, preventing an assessment of best practices. The authors hypothesized that certain case factors may be associated with a higher risk of intraprocedural hypoxemia in children undergoing thoracic surgery and one-lung ventilation.

METHODS

The Multicenter Perioperative Outcomes database and a local quality improvement database were queried for documentation of one-lung ventilation in children 2 months to 3 yr of age inclusive between 2010 and 2020. Patients undergoing vascular or other cardiac procedures were excluded. All records were reviewed electronically for the presence of hypoxemia, oxygen saturation measured by pulse oximetry (Spo2) less than 90% for 3 min or more continuously, and severe hypoxemia, Spo2 less than 90% for 5 min or more continuously during one-lung ventilation. Records were also assessed for hypercarbia, end-tidal CO2 greater than 60 mmHg for 5 min or more or a Paco2 greater than 60 on arterial blood gas. Covariates assessed for association with these outcomes included age, weight, American Society of Anesthesiologists (Schaumburg, Illinois) Physical Status 3 or greater, duration of one-lung ventilation, preoperative Spo2 less than 98%, bronchial blocker versus endobronchial intubation, left operative side, video-assisted thoracoscopic surgery, lower tidal volume ventilation (tidal volume less than or equal to 6 ml/kg plus positive end expiratory pressure greater than or equal to 4 cm H2O for more than 80% of the duration of one-lung ventilation), and type of procedure.

RESULTS

Three hundred six cases from 15 institutions were included for analysis. Hypoxemia and severe hypoxemia occurred in 81 of 306 (26%) patients and 56 of 306 (18%), respectively. Hypercarbia occurred in 153 of 306 (50%). Factors associated with lower risk of hypoxemia in multivariable analysis included left operative side (odds ratio, 0.45 [95% CI, 0.251 to 0.78]) and bronchial blocker use (odds ratio, 0.351 [95% CI, 0.177 to 0.67]). Additionally, use of a bronchial blocker was associated with a reduced risk of severe hypoxemia (odds ratio, 0.290 [95% CI, 0.125 to 0.62]).

CONCLUSIONS

Use of a bronchial blocker was associated with a lower risk of hypoxemia in young children undergoing one-lung ventilation.

EDITOR’S PERSPECTIVE

Endobronchial Intubation to Facilitate Extraluminal Bronchial Blocker Placement in Young Children: A Retrospective Case Series

OBJECTIVES

Extraluminal bronchial blocker placement has become a well-accepted approach to one-lung ventilation in young children. In some cases, technical issues with placement may require alternative approaches to correct bronchial blocker positioning. The primary aim of this study was to review the authors' experience with using endobronchial intubation to facilitate extraluminal bronchial blocker placement in young children.

DESIGN

Single-center case series of pediatric patients undergoing thoracic surgery and one-lung ventilation using a bronchial blocker.

SETTING

Tertiary academic medical center.

PARTICIPANTS

Pediatric patients < three years of age undergoing thoracic surgery and one-lung ventilation who underwent bronchial blocker placement using endobronchial intubation to facilitate blocker placement. In all patients, the bronchial blocker was inserted through a selectively mainstemmed endotracheal tube to facilitate blocker positioning.

INTERVENTIONS

No interventions were performed.

MEASUREMENTS AND MAIN RESULTS

Fifteen patients were identified after a query of the local electronic health record. There were five right-sided and ten left-sided placements in this cohort. Bronchial blocker placement was successful in 14 of 15 patients using endobronchial intubation to facilitate bronchial blocker placement. In one patient, the bronchial blocker was discovered in the nonsurgical bronchus, following placement with this technique. The bronchial blocker was repositioned manually into the desired mainstem bronchus prior to lateral positioning.

CONCLUSIONS

Mainstem intubation can be used to facilitate bronchial blocker placement in young children and represents an alternative approach to extraluminal bronchial blocker placement.

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.