The Effects of Endotracheal Tube Size During Bronchoscopy in Simulated Models of Intubated Patients

The aim is to use a simulation lung model to assess the possibility of performing bronchoscopy through endotracheal tubes (ETT) less than 8.0-mm while appropriately ventilating patients with normal and ARDS lungs in the setting of SARS-CoV-2.

Five SHERIDAN® ETTs were used to ventilate SimMan® 3G under respiratory compliance levels representing normal and severe ARDS lungs. Baseline measurements of peak pressure, plateau pressure, and auto-positive end expiratory pressure (auto-PEEP) were recorded at four different inspiratory times (Ti). Three different-sized disposable bronchoscopes were inserted, and all measurements were repeated.

Normal lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures <30 cm H₂ O, and increasing Ti to minimize peak pressure resulted in low auto-PEEP. Regular bronchoscopes in 7.0-mm ETTs had similar results. Large bronchoscopes in 7.5-mm ETTs generated plateau pressures ranging from 28 to 35 cm H₂ O with modest auto-PEEP. Severe ARDS lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures of 46 and an auto-PEEP of 5 cm H₂ O. Regular bronchoscopes in 7.0-mm ETTs generated similar results. Large bronchoscopes in 8.0-mm ETTs displayed plateau pressures of 44 and an auto-PEEP of 2 cm H₂ O.

To mitigate risk of laryngeal injury, larger ETTs during bronchoscopy should be avoided. Our data show bronchoscopy with any ETT causes auto-PEEP and high plateau pressures, especially in lungs with poor compliance; however, ETT less than 7.5 mm can be used when considering several factors. Our data also suggest similar studies in patients with varying degrees of ARDS would be informative.

NA Laryngoscope, 133:147-153, 2023.