Tracheo-bronchial angles in the human fetus -- an anatomical, digital, and statistical study

Both the advancement of visual techniques and intensive progress in perinatal medicine result in performing airway management in the fetus and neonate affected by life-threatening malformations. This study aimed to examine the 3 tracheo-bronchial angles, including the right and left bronchial angles, and the interbronchial angle, in the fetus at various gestational ages.

Using methods of anatomical dissection, digital image analysis with an adequate program (NIS-Elements BR 3.0, Nikon), and statistics, values of the two bronchial angles and their sum as the interbronchial angle were semi-automatically measured in 73 human fetuses at the age of 14-25 weeks, derived from spontaneous abortions and stillbirths.

No male-female differences between the parameters studied were found. The 3 fetal tracheo-bronchial angles were found to be independent of age. The right bronchial angle ranged from 11.4° to 41.8°, and averaged 26.9±7.0° for the whole analyzed sample. The values of left bronchial angle varied from 24.8° to 64.8°, with the overall mean of 46.2±8.0°. As a consequence, the interbronchial angle totalled 36.2-96.6°, and averaged 73.1±12.7°.

The tracheo-bronchial angles change independently of sex and fetal age. The left bronchial angle is wider than the right one. Values of the 3 tracheo-bronchial angles are unpredictable since their regression curves of best fit with relation to fetal age cannot be modelled. Both of the 2 bronchial angles and the interbronchial angle are of great relevance in the location of inhaled foreign bodies, and in the diagnosis cardiac diseases and mediastinal abnormalities.