EComment. The effect of postoperative change in bronchial angle on postoperative pulmonary function after upper lobectomy in lung cancer patients

Abstract

Seok et al. present a novel and important topic of immediate clinical importance [1], however their work raises a number of questions. In our large clinical experience of performing bronchoscopies on patients after upper lobectomy, both left and right, we have never identified bronchial narrowing secondary to an increased bronchial angle [2-4]. However this clinical observation needs to be qualified by the fact that all the patients were under a general anaesthetic. Secondly we have not seen bronchial compression on CT scanning after upper lobectomy in the absence of a technical error. Dichotomizing the bronchial angle into greater than preoperative or not, provides no calibration to the hypothesis, and is potentially a source of error in analysis. An increased angle of less than 20 degrees is highly unlikely to be clinically significant. Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) are known to represent small airway disease, hence their clinical use [5]. Peak flow, and flow volume loops are thought to be better markers of large airway obstruction, hence their use in acute and chronic asthma and tracheal stenosis [5]. The use of FEV1 postoperatively is clearly confounded by additional variables as it improved in over 60% of patients, contrary to clinical experience. Tracheal stenosis can be very severe (<6.5 mm2) before symptoms become apparent [5]. We speculate that bronchial angle is a surrogate marker for how large the lobe removed was compared to the residual lobe(s). Thoracic surgeons are all aware that the relative sizes of the pulmonary lobes are quite variable between individuals, partially explaining the inaccuracy of the rule of 19. Upper lobectomy involves angulation of the lower lobe upwards to fill in the resultant space. This makes the bronchial angle increase, however the finding by Seok et al., that it may increase in some and decrease in other seems counterintuitive. We speculate that mediastinal tethering of the main bronchus may explain this observation, and could be an issue in some patients. If this speculation is true a decreased bronchial angle if excessive could also be a significant factor. In the series presented 23 patients had an increased angle with worse symptoms, and 36 had an increased angle but improved, P = 0.4, ie no significant effect of angulation on symptoms. Without a multivariate analysis it is difficult to be sure if bronchial angle is a significant factor or not. Measuring the bronchial angle between the main bronchus and lower lobe bronchus fails to take into account movement of the main bronchus relative the carina, a potential source of error. This may be more important on the left than the right. Conflict of interest: none declared.