Some of the difficulties encountered during transbronchial lung biopsy through a flexible bronchofiberscope are due to anatomical reasons, namely the branching angles of some subsegmental bronchi from their mother bronchi are large, and differences in branching angles during respiration may also be large. This makes insertion of forceps difficult. We have sometimes experienced difficulties reaching the target lesion during a transbronchial approach. Which subsegmental bronchi make transbronchial lung biopsy/brushing difficult, and are such difficulties due to anatomical reasons? To answer these questions, we firstly surveyed 10 bronchologists regarding which five subsegmental bronchi they considered to be the most difficult for transbronchial biopsy/brushing. We then measured the branching angles of subsegmental bronchi in 106 cadaver lungs. Finally, in six volunteers, we also measured differences in branching angles of the subsegmental bronchi between the point of forced inspiration and the point of forced expiration on CT images. According to the survey, left B1+2c was considered to be the most difficult for insertion by nine doctors, followed by bilateral B6a by seven, right B1a by five, left B3a by five and left B1+2a by four. The results of our dissections showed that a branching angle of over 60o was present in more than 10% of specimens in B3a, B6a and B6c in the right lung and in B1+2c, B3a, B6a and B6c in the left lung. In addition, three-dimensional reconstructed images revealed that the angles of some subsegmental bronchi changed during respiration. Inter-individual variations were present in most subsegmental bronchi. The direction of movement of each subsegmental bronchus during respiration varied. In addition, maximum degrees of difference in angles between volunteers were sometimes as much as 80°. In conclusion, branching angles of subsegmental bronchi from their mother bronchi are large in B3a, B6a and B6c in the right lung and in B1+2c, B3a, B6a and B6c in the left lung. Most of these correspond to those which many bronchologists felt to be difficult for insertion. In addition, changes in the angles of subsegmental bronchi during respiration are likely to partially account for difficulties encountered during transbronchial approaches.
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