Intrabronchial Airway Pressures in Intubated Patients During Bronchoscopy

• Changes in ventilation, airway pressures and blood gases after bronchoscope insertion. [ Time Frame: 2 minutes after bronchoscope insertion/ mode change ] [ Designated as safety issue: Yes ]
  paO2, paCO2 (kPa), airway and ventilator pressures (cmH2O)
  
  

Mechanically ventilated patients often need bronchoscopy as a diagnostic procedure or for visually directed elimination of secretions. Partial endotracheal tube occlusion by the bronchoscope increases airflow resistance. Inhibition of inspiratory flow may be compensated for by augmented inspiratory pressure. Reduced expiratory flow however, cannot be compensated for by most ventilators and could lead to higher airway - and intrathoracic pressures that are not detected by pressure transducers in the ventilator tubing. In this study we compare changes in ventilation, airway pressures, ventilator pressures and blood gases during bronchoscopy of intubated patients in both volume controlled and pressure controlled ventilation. Our hypothesis are that 1) increased resistance in the tube during bronchoscopy leads to high intrabronchial airway pressures when the ventilator is in volume controlled mode, and 2) when the ventilator is in pressure controlled mode, increased resistance in the tube during bronchoscopy leads to reduced Tidal Volume and moderately increased paCO2.