Chest
Volume 135, Issue 1, January 2009, Pages 33-40
Journal home page for Chest

Original Research
Interventional Pulmonology
The Effects of Flexible Bronchoscopy on Mechanical Ventilation in a Pediatric Lung Model

https://doi.org/10.1378/chest.08-1000Get rights and content

Background

Flexible bronchoscopy performed through endotracheal tubes (ETTs) in children receiving mechanical ventilation can significantly impact ventilation, but the magnitude of this impact has not been established. We used a lung model to simulate mechanical ventilation in a range of child sizes in order to determine how the insertion of pediatric flexible bronchoscopes into ETTs alters ventilatory parameters, especially tidal volume (Vt) and peak inspiratory pressure (PIP), in both healthy and diseased lungs.

Methods

We simulated five child sizes based on weight, and evaluated 22 bronchoscope/ETT combinations, first in pressure control (PC) ventilation mode and then in volume control (VC) ventilation mode. The combinations ranged from the 2.2-mm (bronchoscope outer diameter)/3.0-mm (ETT inner diameter) to 5.0-mm bronchoscope/8.0-mm ETT. The primary outcome measures were decrease in Vt after bronchoscope insertion during PC ventilation and increase in PIP during VC ventilation.

Results

In the PC ventilator mode, Vt decreased by > 50% with nine of the combinations, while during VC ventilation, PIP increased by ≥ 20 cm H2O with seven combinations. The 2.2-mm bronchoscope/3.0-mm ETT, 2.8-mm bronchoscope/5.0-mm ETT, and 3.6-mm bronchoscope/5.0-mm ETT combinations severely impaired ventilation, while the 3.6-mm bronchoscope/4.5-mm ETT, 5.0-mm bronchoscope/6.5-mm ETT, and 5.0-mm bronchoscope/7.0-mm ETT combinations were incompatible with adequate ventilation.

Conclusions

The insertion of bronchoscopes into ETTs can lead to clinically relevant decreases in Vt when in the PC ventilator mode and large increases in PIP during VC ventilation. The minimum bronchoscope/ETT diameter difference required to maintain adequate ventilation increases with child size.

Section snippets

The Lung Model

We used a digitally controlled, high-fidelity breathing simulator (ASL 5000; IngMar Medical; Pittsburgh, PA) to simulate respiratory mechanics in children of sizes ranging from infant through young adult. We designed five models with different lung sizes based on weight (4, 15, 30, 50, and 70 kg). We selected lung compliance and airway resistance values that corresponded to “healthy” lungs5, 6 (Table 1). In addition, we assessed the effects of flexible bronchoscopy in obstructive and

Results

A total of 22 bronchoscope/ETT combinations were evaluated (Table 3). For all sets of measurements, the CV for values obtained from 10 consecutive breaths was < 5%; therefore, the values were averaged. In addition, reinserting the bronchoscope did not change the values by > 10% between any of the three runs. As expected, resistance across the ETT increased, often dramatically, after bronchoscope insertion (Table 3).

Discussion

We used a sophisticated lung model to evaluate the effects of bronchoscope insertion during mechanical ventilation of children with normal and abnormal respiratory mechanics. We found that insertion of bronchoscopes through ETTs significantly decreased Vt when in the PC mode of ventilation, and that when in the VC mode, Vt could be maintained in most cases. However, as the bronchoscope-ETT diameter difference decreased, PIP often increased to > 40 cm H2O, and auto-PEEP was generated. As a

Cited by (29)

  • Airway evaluation: Bronchoscopy, laryngoscopy, and tracheal aspirates

    2022, Goldsmith's Assisted Ventilation of the Neonate: An Evidence-Based Approach to Newborn Respiratory Care, Seventh Edition
  • Ultrashort Echo-Time MRI for the Assessment of Tracheomalacia in Neonates

    2020, Chest
    Citation Excerpt :

    Currently, bronchoscopy relies on a semi-quantitative assessment of airway collapse during spontaneous breathing; unfortunately, bronchoscopy does not take the depth of sedation into account nor the transmural airway pressure, which may alter airway dynamics. The presence of a bronchoscope itself can also alter respiratory mechanics, and it is not clear what effect this may have on tracheal dynamics.29,30 Furthermore, the lack of a standardized definition also allows for interrater variability when interpreting TM based on bronchoscopy, although we achieved very good interrater agreement with agreed upon definitions and extensive training cases.

  • Percutaneous dilatational tracheostomy with a double-lumen endotracheal tube: A comparison of feasibility, gas exchange, and airway pressures

    2015, Chest
    Citation Excerpt :

    MV and Vt decreased more in the conventional ETT group than in the DLET group during PDT. Other studies have also documented a reduction in MV from 35% to 73% due to different ETT and FFB combinations during PDT.24,25 In the present study, the use of a 5-mm external diameter FFB decreased the MV by 40% in the conventional ETT group and only 19% in the DLET group, whereas the Vt was reduced 34% (ETT) and 7% (DLET).

View all citing articles on Scopus

This article was presented in part at the 2007 International Conference of the American Thoracic Society, San Francisco, CA, May 18–23, 2007.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

View full text