The purpose of this study is to examine changes in ventilation and airway pressures during conventional bronchoscopy of intubated patients.

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.

Inclusion Criteria:

• ARDS/ALI patients on mechanical ventilation
• endotracheal tube size 7-9mm
• age > 18 years
• therapeutic or diagnostic bronchoscopy requested by staff physician

Exclusion Criteria:

• SpO2 < 90%
• unstable BP
• pneumothorax
• acute cardiovascular disease
• cerebrovascular or other condition that requires stable BP and saturation

ARDS/ALI patients on mechanical ventilation where a therapeutic or diagnostic bronchoscopy has been requested by the staff physician.