The effects of flexible bronchoscopy on mechanical ventilation in a pediatric lung model.
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 >or= 20 cm H(2)O 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.
Hsia
Danny
D
Department of Pediatrics, University of Washington School of Medicine, Seattle, WA. Electronic address: dhsia@mail.cho.org.
DiBlasi
Robert M
RM
Department of Respiratory Care, Center for Developmental Therapeutics, Seattle Children's Hospital Research Institute, Seattle, WA.
Richardson
Peter
P
Department of Pediatrics, University of Washington School of Medicine, Seattle, WA.
Crotwell
David
D
Department of Respiratory Care, Center for Developmental Therapeutics, Seattle Children's Hospital Research Institute, Seattle, WA.
Debley
Jason
J
Department of Pediatrics, University of Washington School of Medicine, Seattle, WA.
Carter
Edward
E
Department of Pediatrics, University of Washington School of Medicine, Seattle, WA.
D049628:Body Size; D020680:Bronchoscopes; D001999:Bronchoscopy; D002648:Child; D002675:Child, Preschool; D004867:Equipment Design; D006801:Humans; D007223:Infant; D007321:Inspiratory Reserve Volume; D007442:Intubation, Intratracheal; D008171:Lung Diseases / Q000503:physiopathology*; D008954:Models, Biological; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume