|Year : 2015 | Volume
| Issue : 2 | Page : 129-132
Determination of inter-bronchial and subcarinal angles in fetuses of different gestational age and their clinical implication
Anne Dsouza, Vrinda Hari Ankolekar, Aswin Das, Supriya Padmashali, Antony Sylvan Dsouza, Mamatha Hosapatna
Department of Anatomy, Kasturba Medical College, Manipal University, Manipal. Karnataka, India
|Date of Web Publication||13-Jul-2015|
Dr. Mamatha Hosapatna
Department of Anatomy, Kasturba Medical College, Manipal University, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction:The tracheo-bronchial angles in the human fetus are of increasing relevance in perinatal medicine to determine both normal and pathological criteria. The present study was undertaken to calculate the inter-bronchial angle using a novel method by an image analyzer at different gestational ages. Materials and Methods:The present study was carried out using 24 human fetuses in the department of Anatomy, Kasturba Medical College, Manipal. The right and left bronchial, inter-bronchial and subcarinal angles were calculated by using an image analyzer named Image J. Results:The right bronchial angle ranged from 21.99° to 43.96°. The left bronchial angle ranged from 29.48° to 56.21°. The inter-bronchial angle ranged from 60.53° to 100.86°. Student t test was applied to compare the means of bronchial angles between the second and third trimesters which did not show any statistical significance. The subcarinal angle ranged from 41.69° to 74.88° with an average of 61.15 ± 9.73°. Conclusion:The present study analyses the inter-bronchial and subcarinal angles in different GA, the knowledge of which would be essential to understand the developmental changes of the respiratory passages.
Keywords: Bronchial angle, inter-bronchial angle, Kolmogorov Smirnov test, subcarinal angle, tracheal bifurcation
|How to cite this article:|
Dsouza A, Ankolekar VH, Das A, Padmashali S, Dsouza AS, Hosapatna M. Determination of inter-bronchial and subcarinal angles in fetuses of different gestational age and their clinical implication. Muller J Med Sci Res 2015;6:129-32
|How to cite this URL:|
Dsouza A, Ankolekar VH, Das A, Padmashali S, Dsouza AS, Hosapatna M. Determination of inter-bronchial and subcarinal angles in fetuses of different gestational age and their clinical implication. Muller J Med Sci Res [serial online] 2015 [cited 2022 Jan 25];6:129-32. Available from: https://www.mjmsr.net/text.asp?2015/6/2/129/160680
| Introduction|| |
Advances in neonatal medicine have enabled early diagnosis and treatment of respiratory diseases. , The quantitative anatomy of the growing trachea in human fetuses is inadequate. Generally, in fetuses, intubations or interventions involving the airways are not performed before the gestational age of 24 weeks. Although in-utero surgery, being still experimental, is performed from 18 weeks. However, numerical data on fetal tracheas are relevant in prenatal surgery involving the tracheo-bronchial tree.  Previous observations on fetuses with laryngeal atresia proved that the tracheal diameter in affected fetuses was considerably increased as compared with that in normal fetuses at the same age. ,
Changes in the tracheal dimensions occur in a variety of conditions. Generalized widening is a characteristic feature of tracheobronchomegaly and tracheomalacia; generalized narrowing is seen in tracheobronchopathia osteochondroplastica and may be a feature of relapsing polychondritis. 
The advancement of visual techniques implemented in perinatal medical care enables surgeons and anesthesiologists to perform airway management and to detect, monitor, and surgically treat life-threatening anomalies of the fetal tracheo-bronchial tree. Thus, the tracheo-bronchial angles in the human fetus are of increasing relevance in perinatal medicine to determine both normal and pathological criteria. 
The medical literature on the tracheal bifurcation angle offers many discrepancies between reported values with relation to sex and age-dependent differences. ,,
The present study was undertaken using a novel method by an image analyzer named Image J to calculate the inter-bronchial and subcarinal angles of different gestational ages.
| Materials and Methods|| |
The present cross sectional study was carried out in the department of Anatomy, Kasturba Medical College, Manipal, India. The study was conducted on 24 human fetuses gestational age (GA) ranging from 12 to 36 weeks. Spontaneously aborted and stillborn fetuses were obtained from the department of Obstetrics and Gynecology, Kasturba Hospital, Manipal with informed consent. Ethical approval was obtained from the Institutional Ethics Committee (IEC).The fetuses with gross external deformity were excluded from the study.
The thorax was opened by sternotomy and the heart and the great vessels were dissected to expose the trachea. The soft tissue surrounding the trachea was dissected from the level of cricoid cartilage up to its bifurcation into the principle bronchi. Photographs of the trachea were taken in situ along with a millimeter scale and were transferred to a PowerPoint presentation. Three lines were drawn on the image along the central axes of trachea and the principle bronchi bilaterally as shown in [Figure 1]a and b. The images were saved in TIFF format and the angles were calculated using the image analyzer named Image J.
|Figure 1: The angles measured in the fetal trachea (a) Right bronchial angle (b) Left bronchial angle (c) Inter-bronchial angle (d) Subcarinal angle|
Click here to view
The angles calculated were:
- Right bronchial angle between the central axis of trachea and the central axis of right principle bronchus.
- Left bronchial angle between the central axis of trachea and the central axis of left principle bronchus.
- Interbronchial angle between the central axes of right and left principle bronchi.
- Subcarinal angle between the right and left principle bronchi at the carina.
The data was analyzed statistically using SPSS version 16. Kolmogorov Smirnov test was performed for the normality of distribution and Levene's test was performed for homogeneity of variance. The mean and standard deviations were calculated. Student t test and Pearson's correlation were applied accordingly.
| Results|| |
The study was carried out using 24 human fetuses GA ranging from 12 to 36 weeks. There were 2 fetuses of 12 weeks, 16 were of 16-24 weeks and 6 were of 28-36 weeks.
The right bronchial angle ranged from 21.99° to 43.96° with an average of 29.77 ± 6.27°. The left bronchial angle ranged from 29.48° to 56.21° with an average of 43.41 ± 8.04°. The right bronchial angle was 29.84 ± 6.23° at second trimester which decreased to 27.04 ± 5.17° in the third trimester. On the left side the bronchial angle was 57.92 ± 6.85° at second trimester which decreased to 44.93 ± 5.17° in the third trimester. Student t test was applied to compare the means of bronchial angles between the second and third trimesters which did not show any statistical significance.
The inter-bronchial angle ranged from 60.53° to 100.86° with an average of 73.78 ± 11.18°. A significant decrease in the inter-bronchial angle was observed in the third trimester when compared to the second trimester (P = 0.03) which was calculated using student t test.
The subcarinal angle ranged from 41.69° to 74.88° with an average of 61.15 ± 9.73°. There was a significant difference in the subcarinal angle between second and third trimesters (P = 0.05).
Pearson's correlation test was applied to correlate the bronchial and subcarinal angles with the GA. No significant correlation was found between the parameters. This may be due to the small sample size.
The bronchial angles were compared between first and second trimesters as the sample size was small in first trimester for statistical evaluation. Also the gender differences were not analysed due to the less number of female fetuses available.
| Discussion|| |
The lung bud during the end of 4 th week of development forms the trachea, and two lateral outpocketings called bronchial buds. At the beginning of 5 th week these buds enlarge to form right and left bronchi. 
The present study describes a cross-sectional interpretation of the tracheo-bronchial angles based on the evidence from using 24 human fetuses GA ranging from 12 to 36 weeks. There were 2 fetuses of 12 weeks, 16 were of 16-24 weeks and 6 were of 28-36 weeks.
A study done by Daroszewski et al. on 73 human fetuses of both sexes (39 males and 34 females) at the age of 14-25 weeks of GA revealed the morphometric right bronchial angle ranged from 11.4° to 41.8°, with its mean of 26.9 ± 7.0°. The left bronchial angle varied from 24.8° to 64.8°, and averaged 46.2 ± 8.0°. The inter-bronchial angle ranged from 36.2° to 96.6° with a mean of 73.1 ± 12°. In their study no male-female differences for the angles was observed. 
According to Harjeet et al. in the 3 groups of fetuses with CRL of 61-130 mm, 131-200 mm, and 201-270 mm, the left bronchial angles were 32.17 ± 6.98°, 33.79 ± 8.57°, and 34.74 ± 3.67° respectively and the right bronchial angles were 17.37 ± 7.77°, 19.75 ± 8.73°, and. 20.54 ± 1.86°, respectively. A radiographic study by the same author revealed an insignificant increase in the subcarinal angle with age from 49.53 ± 12.10° in fetuses with crown rump length (CRL) of 61-130 mm, through 53.54 ± 16.17° in fetuses with CRL of 131-200 mm, up to 55.27 ± 3.66° in fetuses with CRL of 201-270 mm. 
A neonatal study done by Harjeet et al. revealed the angle of right bronchus 23.13 ± 4.54°, left bronchus 39.84 ± 3.89 and the subcarinal angle 62.98 ± 8.03. 
As reported by Karabulut the 4 tracheo-bronchial angles (right and left bronchial, interbronchial and subcarinal) were significantly greater in females than males. The mean interbronchial angle was 77 ± 13° (range 49-109°) and subcarinal angle was 73 ± 16° (range 34-107°). Tracheal bifurcation angle ranged widely in normal subjects and absolute measurements of the carinal angle is of little diagnostic value. 
Similarly, according to Kamel et al. the subcarinal angle in adults ranged from 36° to 121° in men, and from 47° to 115° in women, with overall means of 76 ± 20°, and 81 ± 20° respectively, without any correlation with age. He also observed that the carina was situated on the left in up to 81.4% of individuals. 
Tahir et al. stated that in 66% of children, especially under age 1 year, the carina was positioned to the left of the midline of the trachea. 
According to Mrudula et al. the subcarinal angle varied between 50° and 130° and mean was 77.58°. Right main bronchus angle was 39.68° on average and ranged between 30° and 60°. Left main bronchus angle was 43.4°. The subcarinal angle varied between 50° and 130° and the mean was 77.58°. 
In the present study the right bronchial angle ranged from 21.99° to 43.96° whereas on the left side it ranged from 29.48° to 56.21°. The bronchial angles between the second and third trimesters did not show any statistical significance.
The inter-bronchial angle in the present study ranged from 60.53° to 100.86°. A significant decrease in the inter-bronchial angle was observed in the third trimester when compared to the second trimester (P = 0.03). The subcarinal angle ranged from 41.69° to 74.88°. There was a significant difference in the subcarinal angle between second and third trimesters (P = 0.05).
The subcarinal and inter-bronchial angles were found to correlate positively with the size of the left atrium of the heart.  The tracheal bifurcation angle may be widened due to cardiac disease (left atrial enlargement, cardiomegaly, and pericardial effusion) and mediastinal abnormalities (subcarinal masses).  There are also studies on the length of fetal trachea including prebifurcational and bifurcational lengths near the carina. 
| Conclusion|| |
The present study analyses the inter-bronchial and subcarinal angles in different GA, the knowledge of which would be essential to understand the developmental changes of the respiratory passages. The use of digital image analyser (ImageJ) which would provide more accurate values than the manual morphometric approaches. The assessment of these parameters is essential during various interventions involving the respiratory passages in neonates.
| References|| |
Harrison MR, Keller RL, Hawgood SB, Kitterman JA, Sandberg PL, Farmer DL, et al
. A randomized trial of fetal endoscopic tracheal occlusion for severe fetal congenital diaphragmatic hernia. N Engl J Med 2003;349:1916-24.
Jani J, Gratacós E, Greenough A, Pieró JL, Benachi A, Harrison M, et al
. Percutaneous fetal endoscopic tracheal occlusion (FETO) for severe left-sided congenital diaphragmatic hernia. Clin Obstet Gynecol 2005;48:910-22.
Kamel KS, Lau G, Stringer MD. In vivo
and in vitro
morphometry of the human trachea. Clin Anat 2009;22:571-9.
Kohl T, Hering R, Bauriedel G, Van de Vondel P, Heep A, Keiner S, et al
. Fetoscopic and ultrasound-guided decompression of the fetal trachea in a human fetus with Fraser syndrome and congenital high airway obstruction syndrome (CHAOS) from laryngeal atresia. Ultrasound Obstet Gynecol 2006;27:84-8.
Martínez JM, Prat J, Gómez O, Crispi F, Bennasar M, Puerto B, et al
. Decompression through tracheobronchial endoscopy of bronchial atresia presenting as massive pulmonary tumor: A new indication for fetoscopic surgery. Fetal Diagn Ther 2013;33:69-74.
Breatnach E, Abbott GC, Fraser RG. Dimensions of the normal human trachea. AJR Am J Roentgenol 1984;142:903-6.
Szpinda M, Daroszewski M, Woźniak A, Szpinda A, Mila-Kierzenkowska C. Tracheal dimensions in human fetuses: An anatomical, digital and statistical study. Surg Radiol Anat 2012;34:317-23.
Coppola V, Vallone G, Coscioni E, Coppola M, Maraziti G, Alfinito M, et al
. Normal value of the tracheal bifurcation angle and correlation with left atrial volume. Radiol Med 1998;95:461-5.
He WX, Han BQ, Liu M, Zhang P, Fan J, Song N, et al
. Tracheobronchial reconstructions with bronchoplastic closure: An alternative method in treatment of bronchogenic carcinoma involving the carina or tracheobronchial angle. J Thorac Cardiovasc Surg 2012;144:418-24.
Standring S. Gray′s Anatomy: The Anatomical Basis of Clinical Practice. 39 th
ed. Philadelphia: Churchill Livingstone; 2008. p. 1075-6.
Sadler TW. Langman′s Medical Embryology. 12 th
ed. Philadelphia: Lippincott Williams & Wilkins; 2012. p. 203.
Daroszewski M, Szpinda M, Flisiński M, Szpinda A, Woźniak A, Kosiński A, et al
. Tracheo-bronchial angles in the human fetus - an anatomical, digital, and statistical study. Med Sci Monit Basic Res 2013;19:194-200.
Harjeet, Sahni D, Batra YK, Rajeev S. Anatomical dimensions of trachea, main bronchi, subcarinal and bronchial angles in fetuses measured ex vivo
. Paediatr Anaesth 2008;18:1029-34.
Jit H, Jit I. Dimensions & shape of the trachea in the neonates, children & adults in northwest India. Indian J Med Res 2000;112:27-33.
Karabulut N. CT assessment of tracheal carinal angle and its determinants. Br J Radiol 2005;78:787-90.
Tahir N, Ramsden WH, Stringer MD. Tracheobronchial anatomy and the distribution of inhaled foreign bodies in children. Eur J Pediatr 2009;168:289-95.
Mrudula C, Krishnaiah M. The study of bronchial tree. Int J Pharma Bio Sci 2011;2:B166-72.
Goktalay T, Yaldiz S, Ozgen Alpaydin A, Goktan C, Celik P. An unusual presentation of bronchial rupture. Respir Care 2011;56:858-60.
Taskin V, Bates MC, Chillag SA. Tracheal carinal angle and left atrial size. Arch Intern Med 1991;151:307-8.
Dsouza A, Ankolekar VH, Hosapatna M, Dsouza AS. Dimensional changes of trachea in second and third trimester fetuses - an anatomical study. Int J Cur Res Rev 2013;5:126-31.