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

Abstract

BackgroundBoth 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.Material/MethodsUsing 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.ResultsNo 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°.ConclusionsThe 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.

Airway dimensions from fetal life to adolescence—A literature overview

“…The 33 included anatomical studies are based on measurements from pediatric autopsy preparations between 1923 and 2013 and are summarized as Supplementary Appendix SI. With minimally seven and a maximum of 452 investigated specimens, the measured structures range from the thyroid to the two main bronchi.…”

“…With minimally seven and a maximum of 452 investigated specimens, the measured structures range from the thyroid to the two main bronchi. The measurements were carried out with manual or digital measuring slide or measuring strips, microscopes, spike circles, or computer‐assisted measuring methods . Sliders were the most frequently used instruments in the anatomical work, enabling the most precise measurements up to 0.01 mm …”

“…Twenty‐five studies were identified that represent airway dimensions in fetuses or premature infants, between 1923 and 2013 . The measured structures range from the thyroid to the two main bronchi and are summarized in Supplementary Appendix SI‐SIV under references superscripted as following numbers: 99 (MRI studies table), (anatomical studies table), 42 (X‐ray studies table), 101, 103, 106 (USG studies table). The scientific work by means of ultrasound only includes measurements of the diameter of the airways .…”

“…In some scientific works, the measurement is performed directly on the freshpreparations, while in other studies, frozen, or epoxy resin or formalin fixations were embedded. Eight studies do not discuss fixation. According to Too‐Chung, no significant shrinkage reaction is expected and Kahane on the other hand, mentions that shrinkage results from fixation by means of formalin, as well as from the freezing of the preparations.…”

“…An important exception to this, is the work by Griscom and colleagues, which was useful for comparisons in many subsequent studies . Furthermore, all these studies have a natural variation in ethnic and racial groups of patient selection, which ranges from American as in Griscom, to European as in Fayoux, Szpinda, and Weiss50, group, to Australian as in Masters group, to Middle East as in Wani group, to Asian as in Dalal, Harjeet, and other groups and hence the results cannot be generalized for the entire pediatric population. One recent multicentre study tried to overcome this problem and represented lower airway dimensions in a large pediatric population representing different racial and ethnic groups.…”