Some patients with severe chronic obstructive pulmonary disease (COPD) exhibit significant dynamic expiratory collapse of the airways. This abnormality is sometimes seen during flexible fiberoptic bronchoscopy. We attempted to determine a physiologic abnormality characteristic of this finding.
We prospectively investigated ten subjects with visible dynamic collapse of the airways beyond the main carina identified at the time of bronchoscopy. All ten subjects were recorded on video. All subjects underwent forced expiratory maneuvers with recording of forced expiratory vital capacity (FVC), forced inspiratory vital capacity (FIVC), expiratory flows and flow volume loops with associated normal tidal volume inspiratory and expiratory loops. Maximum voluntary ventilation (MVV) maneuvers were recorded. An obstructive pattern was defined as an FEV1/FVC% less than 70%. The results obtained for the different parameters were compared to accepted normal values.
When the data from the flow volume loops were evaluated, eight of ten subjects showed an obstructive pattern (FEV1/FVC% < 70%, range 52 to 68%). MVV (percent predicted) ranged from 24% to 102% (obstructed) and from 85 to 95% (non-obstructed). FIVC was less than the FVC in nine out of ten. The most characteristic finding was that the expiratory limb of the tidal volume tracing occurred at some point on the maximum expiratory curve of the flow volume loop. No abnormalities were observed in the inspiratory limb of the flow volume loop.
1. All subjects with demonstrable collapse identified at fiberoptic bronchoscopy showed that the expiratory limb of the normal tidal volume tracing occurred at some point on the maximum expiratory flow volume envelope. 2. Eight of ten subjects with dynamic collapse showed an obstuctive pattern. 3. Nine out of ten subjects showed an FIVC less than the FVC. 4. The two non-obstructed subjects did not show concave upward appearance of the flow volume loop.
The presence of significant expiratory dynamic airways collapse and its accompanying flow volume loop changes do not necessarily indicate obstructive airways disease.
M. Ora, None.