Changes in breathing patterns after lung operations.

To assess the effects of thoracic surgery on breathing patterns without conscious intervention, we analyzed and compared the breathing patterns observed immediately before and after surgical procedure while anesthesia was maintained with enflurane and nitrous oxide at a constant level in 15 patients undergoing thoracic surgery. Our results showed that immediately after the surgical procedure, respiratory frequency (f) was significantly higher and tidal volume (V(T)) was significantly smaller than those observed immediately before the surgical procedure. The increased f during the period immediately after the surgical procedure was due to shortening of both inspiratory time (T(I)) and expiratory time (T(E)) without changing the ratio of T(I) to the total breath time (T(tot)). Despite the significant decrease in V(T) observed immediately after the surgical procedure, the value of negative pressure during the occluded inspiration (P(max)) was significantly higher than that observed immediately before the surgical procedure. These results indicate that a rapid, shallow type of breathing pattern can occur after thoracic surgery without conscious intervention.