Alterations in pulmonary mechanics and gas exchange during routine fiberoptic bronchoscopy.

Pulmonary function and arterial blood gases were measured in 35 patients undergoing routine diagnostic flexible fiberoptic bronchoscopy (FFB) either through an 8-mm endotracheal tube (ETT) or transnasally in order to investigate whether FFB changes lung function in a way which may explain why hypoxemia commonly occurs during this procedure. In these patients with moderate airway obstruction, functional residual capacity (FRC) increased significantly after inserting the ETT, after placing the FFB in the airway through the ETT, and after inserting the flexible bronchoscope transnasally. The mean increase in FRC was 30 percent in the intubated group before FFB insertion and 17 percent in the transnasal group. Removal of the FFB and ETT caused FRC to return toward the control value. Insertion of the ETT-FFB combination or transnasal FFB did not change PaO2 substantially, although following the examination, PaO2 was decreased significantly in the transnasal group but not in the intubated group. The PaO2 decreased significantly in both groups following removal of the ETT and transnasal FFB. These results suggest that placement of an FFB or ETT-FFB combination in the airway in spontaneously breathing subjects elevates FRC.