THORACOTOMY INCREASES PERIPHERAL AIRWAY TONE AND REACTIVITY

Our goal was to investigate the extent to which thoracotomy for chroni c vascular instrumentation alters peripheral airway tone and reactivit y. Using the wedged bronchoscope technique to measure peripheral airwa y resistance (R(P)), pentobarbifal-fentanyl anesthetized, ventilated d ogs were studied before and (16 +/- 2 d) after a left thoracotomy for chronic implantation of instrumentation to measure the left pulmonary vascular pressure-flow relationship. A map of the airways was construc ted as bronchoscopes were advanced and wedged in the middle lobes of b oth the left and right lung. This allowed us to measure R(P) in the sa me sublobar region of the left and right lung both pre- and postoperat ively. At the time of postoperative experimentation, all dogs appeared fully recovered from the surgical procedure. Compared with preoperati ve values, baseline R(P) (cm H2O . ml(-1). s(-1)) was selectively incr eased (p < 0.03) postoperatively in the left (0.41 +/- 0.07 versus 1.2 7 +/- 0.36) but not in the right (0.29 +/- 0.06 versus 0.35 +/- 0.07) lung. Peripheral airway responses to acetylcholine, histamine, hypocap nia, and dry air challenges were all increased (p < 0.05) in both magn itude and duration in the left but not the right lung postoperatively. Total lung volume (helium dilution technique) was decreased (p < 0.01 ) by 10 +/- 3% postoperatively. However, similar reductions in lung vo lume were observed in the left and right lung. These results indicate that left thoracotomy for chronic instrumentation selectively increase s left lung peripheral airway tone and reactivity, but has no effect o n the right lung. These changes cannot be explained by the concomitant postoperative decrease in lung volume.