Subcarinal Angle Research Articles

Analysis of airway structural parameters in Han Chinese adults: a prospective cross-sectional study

Introduction Establishing reference ranges for central airway parameters and exploring their influencing factors in Han Chinese non-smoking adults. Methods This prospective cross-sectional study was conducted on Han Chinese non-smoking adults who underwent chest CT scans at the Tongzhou Campus of Dongzhimen Hospital Affiliated with the Beijing University of Chinese Medicine between September 2022 and November 2022. The SYNAPSE 3D image analysis software was utilized, enabling the extraction of critical parameters such as central airway length, airway wall thickness (AWT), airway lumen area (ALA), and subcarinal angle (SCA). Pearson’s correlation coefficient analysis and multiple linear regression analysis methods were employed to evaluate the relationship between central airway parameters and age, sex, weight, and height. Results The study encompassed 888 Han Chinese non-smoking adults, comprising 456 females and 432 males. Significant sex differences were noted in central airway length, AWT, and ALA, with measurements in males exceeding those in females (p < 0.01) with no significant difference in SCA. Correlation analyses unveiled relationships between central airway parameters and age, sex, weight, and height. During multiple linear regression analyses, no conclusive evidence emerged to demonstrate the independent or combined explanatory or predictive capacity of the aforementioned variables for central airway length and SCA. Although sex has a significant impact on AWT and ALA, its capability in explanation or prediction remains limited. The conclusions drawn from the primary analysis receive reinforcement from the outcomes of sensitivity analyses. Conclusion Establishing the distribution range of central airway parameters in non-smoking Han Chinese adults. It observed significant sex differences in these parameters, except for the SCA. However, the study found that the predictive or explanatory power of age, sex, weight, and height for central airway parameters was either limited or non-significant.

Systematic literature study of trachea and bronchus morphology in children and adults.

Understanding the dimensions of the lower airway is critical for performing respiratory surgery, selecting and designing appropriate airway equipment, and removing aspirated foreign bodies via bronchoscopy, anaesthesia, and radiography. The purpose of this study was to analyse the trachea and bronchus morphologically in children and adults, as well as to standardise the data for these structures' measurements. Various databases were reviewed for studies on lower airway dimensions. The criteria for inclusion and exclusion were established. Finally, it was agreed to look into 28 studies that took place between 1984 and 2021. The length of the trachea, its anterior-posterior (AP) and transverse dimensions, the lengths and transverse diameters of the right and left major bronchus, and the subcarinal angle were also investigated in the study. In studies where measurements were performed with different methods and procedures. It was revealed that age and gender were effective in the difference in lower respiratory tract dimensions. The mean values of all parameters were greater in adults than in children, the AP diameter of the trachea in adults was greater than the transverse diameter. In children, it was observed that the transverse diameter was larger than the AP diameter on average, the left main bronchus was longer than the right main bronchus, and the transverse diameter was smaller than the right main bronchus in most of the studies. The articles reviewed for this study revealed that measurements were done using a variety of different procedures and approaches, and the resulting data were inconsistent and could not be standardized. The data collected will be beneficial both conceptually and clinically; we believe that additional comparison research involving children and adults in bigger groups are necessary.

Investigation of Subcarinal Angle and Tracheobronchial Morphology in Patients with COVID 19: A Retrospective Computed Tomography Study

Objective: Morphological features of the trachea are very important in choosing the correct endotracheal tube size for intubation. In this study, it was proposed to reveal the effect of SARS-CoV-2 on tracheobronchial morphology and subcarinal angle. &#x0D; Method: 56 (26 female, 30 male) COVID-19 and 48 (24 female, 24 male) healthy individuals aged 40 and over were included in the study. The mean age of female patients with COVID-19 was 51.30±12.78 years, while the women in the control group were 45.00±11.89 years. The mean age of male patients with COVID-19 was 48.73±13.99 years, while the mean age of men in the control group was 43.76±8.45 years. The trachea length (TL), proximal, middle and distal levels anteroposterior (AP) and transverse (TR) trachea diameters (TD), subcarinal angle (SA), proximal right main bronchus (RMB) and left main bronchus (LMB) diameters were also measured on computed tomography (CT) images. &#x0D; Results: The RMB angle was higher in men with COVID-19 than in the control group (p=0.005). TL was lower in women with COVID-19 than in the control group (p=0.030). Proximal AP-TD was higher in men with COVID-19 than in the control group (p=0.006). Proximal TR-TD was lower in men with COVID-19 than in the control group (p=0.029). TL, proximal, middle, and distal levels of AP and TR-TD,SA, RMB, and LMB angles, and proximal RMB and LMB diameters were found to be lower in women with COVID-19 than in men with COVID-19 (p=0.001). &#x0D; Conclusion: It was deduced that tracheobronchial morphology might change in patients infected with SARS-CoV-2.It is clinically important that this situation should not be overlooked, especially in the indication of endotracheal intubation.

COVID-19 disease may change subcarinal angle

Introduction: Evaluation of the severity of the disease in coronavirus disease 2019 (COVID-19) is important. Chest radiogram and computed tomography are suitable tools for inspecting structural changes in the lung parenchyma. The aim of this study was to evaluate the relationship between subcarinal angles (SCAs) of the left and the right main bronchi and tomography severity score (TSS) and changes in SCA after recovery, assessed with computed tomogra-phy among patients with COVID-19. Methods: This retrospective observational study was conducted between March 2020 and January 2021. A poly-merase chain reaction test was used to diagnose COVID-19. All participants were examined with thorax computed tomography both in acute disease episode and 6 months after recovery. SCA of right and left main bronchi and TSS and changes in SCA values after recovery were compared. Results: The mean of SCA measurements in COVID-19 acute episode was 74.76±12.94 degrees, while it was found to be increased to 82.83±14.09 degrees (p=0.011) 6 months after recovery. There was no association between SCAs of total, right, and left main bronchi and TSS (r=-0.046 and p=0.784, r=-0.024 and p=0.887, and r=-0.056 and p=0.739, respectively). While TSSs were similar between both genders, SCA values were found to be higher in females. The most frequently involved lung lobe was the right lower lobe. Discussion and Conclusion: SCA values were higher in patients at 6th month after recovery from COVID-19. Due to this finding, it may be proposed that parenchymal changes in lung tissue are long-lasting and may be persistent after recovery from COVID-19.

Morphometry of Adult Human Trachea and its Clinical Implications: A Cadaveric Study in Northern India

Introduction: There is a wide variation in different dimensions of trachea in same age group as well as in different age groups in both sexes. Besides anthropometry, the study of these morphometric variations is of profound clinical importance as it may help the pulmonologists to understand the aetiology of several pulmonary diseases like bronchitis, emphysema, pulmonary fibrosis and tuberculosis. Aim: To determine the variations in the dimensions of human trachea in the cadavers of age group 20-70 years in Northern India. Materials and Methods: This cross-sectional study was conducted in the Department of Anatomy, Sri Guru Ram Das Institute of Medical Sciences and Research, Amritsar, Punjab, India, during March 2019 to December 2021. A total of 40 tracheas were obtained from adult human cadavers which were included in present study by convenience sampling. The trachea was dissected with the larynx and principal bronchi and measurements were taken. Data collected was saved on Microsoft excel and was analysed by calculating percentages, mean and Standard Deviation (SD). Results: Mean length of trachea was 109.25 mm, mean subcarinal angle was 75.45°. Mean anteroposterior diameter, transverse diameter, mean height and distance between posterior ends of rings was 16.70 mm and 18.10 mm, 4.53 mm and 12.15 mm respectively and mean of inter-ring distance between 1st-2nd, 5th6th, 10th-11th, 15th-16th Tracheal rings was 1.12 mm. Conclusion: The present study revealed a wide variation in different dimensions viz. length, transverse and anteroposterior diameters, mean height, inter-tracheal ring distance and the subcarinal angle. Accurate anatomical knowledge of the variations is essential for understanding the pathophysiology and management of different airway disorders and in reconstructive surgery of tracheobronchial tree.

Measurement of the Sub-carinal Angle on the Normal Chest Radiograph of Adult at BPKIHS, Dharan, Nepal

Background: The sub-carinal angle is an angle formed between the main right bronchus and leftbronchus clearly seen in adequately exposed chest radiograph, normally at the level of 5th thoracicvertebrae.&#x0D; Objective: To measure sub-carinal angle in relationship to different age, sex and body mass index inthe adult.&#x0D; Methods: A cross-sectional study was carried out in the Department of Radio diagnosis and Imaging at BPKIHS, Dharan from 27th April to 6th August 2017. Sub-carinal angle was measured on the normal chest radiograph in 392 adult patients. The data were analyzed using SPSS Version 11.5 and descriptive statistics percentage, Mean, Standard Deviation were calculated. For inferential statistics, Independent ‘t’ test and Pearson’s correlation were applied.&#x0D; Results: The sub-carinal angle ranged from 39°- 81.1° with mean value 60.17°+7.81°. The mean subcarinalangle for the male was 59.17°+8.19° and for female was 60.62°+7.49°. The mean sub-carinalangle was wider in female than male in our study; however, the difference in sub-carinal angle between male and female was statistically not significant (p&gt; 0.05). There was negative correlationbetween sub-carinal angle and age (r= -0.168, p &lt;0.01). The sub-carinal angle was positivelycorrelated with BMI (r= 0.100, p&lt; 0.05).&#x0D; Conclusion: In our study, the mean sub-carinal angle was 60.17° ± 7.81°. The mean sub-carinal angle difference between male and female was statistically non-significant. There was negative correlation of sub-carinal angle with age and positive correlation with BMI. The reference value obtained from this study will be helpful to diagnose abnormal sub-carinal angle due to various pathologies.

Clinical and structural aspects of tracheal stenosis and a novel embryological hypothesis of left pulmonary artery sling.

To identify the imaging features peculiar to congenital tracheal stenosis (CTS) complicated with left pulmonary artery sling (LPAS) with the aim of presenting a hypothesis of tracheal stenosis embryology in LPAS. We retrospectively reviewed CTS patients (with complete cartilaginous rings) admitted between April 2010 and July 2018. All the patients were classified into the LPAS or non-LPAS group, and their clinical characteristics and qualitative variables on computed tomography (CT) imaging were compared. Of the 72 patients enrolled, 61 had bilateral lungs. Among the bilateral lung patients, 26 (43%) had LPAS. The tracheal bifurcation was significantly deeper, the stenotic region was longer, and the bronchial angle (especially in the right) was wider, in the LPAS group. The cut-off values for the thoracic vertebral level at the tracheal bifurcation (>4.8), subcarinal angle (>118.1), and right bronchial angle (>61.9) were useful for diagnosing suspected cases of LPAS. In the time-dependent course, LPAS complicated with a congenital heart defect was a statistically significant risk factor of respiratory symptoms (hazard ratio, 3.01; 95% confidence interval, 1.23-7.37; P = .02). The CT findings described here should immediately raise suspicion of LPAS on chest X-ray and also suggest tracheal "squeezing and milking" by the surrounding vessels in the embryo. Patients with LPAS complicated with a heart defect should be followed carefully to determine the optimal timing of intervention.

Measurement of Subcarinal Angle: A Cadaveric study

Introduction: The bifurcation of trachea into two primary bronchi at the level of fourth thoracic vertebra creates an angle at the bifurcation. This angle can be seen clearly in routine chest X-rays where the measurement can throw light on many medical conditions within the mediastinum. This study aimed at finding the subcarinal angle, which is the angle formed by inferior borders of two primary bronchi. Methods: The measurements were taken from photographs of tracheal specimen of 92 cadavers, 63 male and 29 female. Angle was measured by photographic software and analysis of subcarinal angle was done in the study population. Results: The mean subcarinal angle was found to be 41.090 with standard deviation of 17.140. This measurement was found to be significantly more in males (68.02± 15.720) than in females (60.14 ± 17.710). Conclusion: The subcarinal angles in the study population were seen to be different among sexes. Also, the mean subcarinal angles from other studies, radiological or on specimen were close to the observations made in this study.

Measurement of Subcarinal Angle: A Cadaveric study

Introduction: The bifurcation of trachea into two primary bronchi at the level of fourth thoracic vertebra creates an angle at the bifurcation. This angle can be seen clearly in routine chest X-rays where the measurement can throw light on many medical conditions within the mediastinum. This study aimed at finding the subcarinal angle, which is the angle formed by inferior borders of two primary bronchi.&#x0D; Methods: The measurements were taken from photographs of tracheal specimen of 92 cadavers, 63 male and 29 female. Angle was measured by photographic software and analysis of subcarinal angle was done in the study population.&#x0D; Results: The mean subcarinal angle was found to be 41.09° with standard deviation of 17.14°. This measurement was found to be significantly more in males (68.02± 15.72°) than in females (60.14 ± 17.71°).&#x0D; Conclusion: The subcarinal angles in the study population were seen to be different among sexes. Also, the mean subcarinal angles from other studies, radiological or on specimen were close to the observations made in this study.

ESTIMATION OF SUBCARINAL ANGLE USING MINIMUM INTENSITY PROJECTION IN COMPUTED TOMOGRAPHY

Objectives: The main objective of the study was to determine the normal subcarinal angle (SCA) in an adult patient, to compare the relationship of SCA with patient gender and age, and to correlate the SCA with body mass index (BMI).Methods: A total of 193 subjects (109 males and 85 females) in the age group of 20–60 years scheduled for computed tomography thorax at the Department of Radiodiagnosis and Imaging, Kasturba Hospital, Manipal, were included in the study. Plain images were reconstructed into 1.4 mm reformatted image and processed into minimum intensity projection, and measurement was taken using angle tool. Mean and standard deviation was used to determine normal SCA, and independent t-test was used to compare the relationship of SCA with patient’s age and gender. “Pearson correlation” was used to correlate SCA with BMI.Results- The mean SCA of the adult patient was 69.75±3.38°. The mean SCA in female was 69.90±4.07° and in male was 69.63±2.75°. In the age group of 20–40 years, the mean SCA was 70.38±3.85°, and in the age group of 41–60 years, it was 69.25±2.88°.Conclusion: There was no relationship between SCA and patient’s gender; however, the mean SCA of the age group 20–40 was found greater than that of 41–60 which was statistically significant. BMI has no significant correlation with SCA.

Dual-source computed tomography for quantitative assessment of tracheobronchial anomaly from type IIA pulmonary artery sling in pediatric patients

PurposeAs an extremely rare abnormity, type IIA pulmonary artery sling (PAS) tracheobronchial anomalies should be differentiated from normal airway for therapeutic decision-making. This study aimed to investigate the quantitative characteristics of type IIA PAS tracheobronchial anomalies using dual-source computed tomography (DSCT). Materials and methodsFrom January 2009 to December 2016, there were 11 type IIA PAS patients enrolled for analysis and compared with 32 controls. The areas of the trachea, right upper lobar bronchus, left main bronchus, right intermediate bronchus [bridging bronchus (BB) in patients], and subcarinal angle [subpseudocarinal angle in patients] were measured. Measurements other than that for the angle were standardized with body surface area. ResultsSignificant differences were found between the type IIA PAS patients and controls in terms of DSCT measurements in the trachea (0.51 ± 0.32 cm2/m2 vs. 0.92 ± 0.18 cm2/m2, P < 0.001); left main bronchus (0.29 ± 0.14 cm2/m2 vs. 0.43 ± 0.18 cm2/m2, P = 0.01); right intermediate bronchus [BB in patients] (0.36 ± 0.13 cm2/m2 vs. 0.47 ± 0.12 cm2/m2, P = 0.02); and subcarinal angle [subpseudocarinal angle in patients] (116.27 ± 16.45° vs. 79.41 ± 15.71°, P < 0.001). Receiver operating characteristic analysis further revealed that these parameters may be indicators to differentiate tracheobronchial anomalies due to type IIA PAS from controls (AUC, 0.88–0.98; sensitivity, 81.7%–100%; specificity, 91.7%–100%). ConclusionsDSCT is an alternative technique to detect tracheobronchial anomalies in pediatric patients with type IIA PAS. It can provide accurate anatomic details for surgeons to determine therapeutic strategies.

A morphometric study of human subcarinal angle in different age groups in both sexes and its clinical implications

To evaluate the interactions between the crude extracts of Cocos nucifera (C. nucifera) and six front line antibiotics (ampicillin sodium salt, penicillin G sodium, amoxicillin, chloramphenicol, ciprofloxacin and tetracycline hydrochloride), against some bacterial pathogens linked with human infection.The pulverized husk of C. nucifera was dissolved in 95% n-hexane and extracted using Soxhlet extraction method and sterile distilled water (aqueous). The antibacterial susceptibility of the crude extracts of C. nucifera was tested against environmental and clinical strains (6) obtained from the South African Bureau of Standards (SABS), Vibrio (6) and Listeria pathogens (6). The agar-well diffusion method was used for screening the extracts for their antibacterial activity. The minimum inhibitory concentration and minimum bactericidal concentration of the extracts were determined. Time-kill assay was used to evaluate bactericidal and/or bacteriostatic activity. The synergistic effect of the crude extracts and antibiotics was assessed and evaluated by adopting the checkerboard methods.With the time-kill assay, the highest bactericidal activity was observed on Vibrio fluvialis EL041 with a −5.6 ± 0.2 log10 CFU/mL decrease in cell density as a result of the combination of the extracts and chloramphenicol at two-fold minimum inhibitory concentrations. Synergisms using the time-kill assay constituted about 72%, while indifference constituted about 28%. The checkerboard method revealed synergistic interaction in 67% of the combinations, and indifference in 33%. There was no specificity in the observed synergy to a particular class of antibiotics.This investigation suggests the crude extracts of C. nucifera to be a potential broad spectrum antimicrobial compound. Therefore, further study is needed to isolate the pure compounds from these crude extracts.

Tracheobronchial Angle Measurements in Children: An Anthropometric Retrospective Study With Multislice Computed Tomography.

ObjectivesThe purpose of this study is to investigate if any change exists in the values of tracheal bifurcation angles (subcarinal angle [SCA] and interbronchial angle [IBA]), right and left bronchial angles (RBA and LBA) in different pediatric age groups.MethodsChest computed tomography (CT) images of children aged 18 years and younger were reviewed retrospectively by two radiologists who were blinded to each other’s measurements. One hundred and eighteen children were involved. RBA, LBA, SCA, and IBA were measured on coronal reformatted images. Subjects were classified into three groups according to their age. Measurement of IBA was done by measuring the angle between the lines drawn along the central axis of right and left main bronchi over their length. RBA and LBA were measured at the intersection points of the lines drawn along the inferior borders of the right and left main bronchi and the line passing through the longitudinal axis of trachea. Sums of RBA and LBA gave SCA. Interobserver agreement was also analyzed.ResultsSCA, IBA, and RBA values were statistically significant between children of ages less than 10 years and over 10 years P<0.01). Interobserver agreement was excellent with an intraclass correlation coefficient score of 0.87 (95% confidence interval) for RBA, SCA, and IBA measurements.Conclusion We concluded that tracheal bifurcation angles are wider in children of age 10 years and younger. As age increases values of SCA, IBA, and RBA decrease.

Measurement and analysis of the tracheobronchial tree in Chinese population using computed tomography.

ObjectiveTo ascertain accurate measurements of, and the relationships between, the normative parameters of the tracheobronchial trees in the Chinese population using multi-slice spiral computed tomography (CT) and multi-planar reconstruction (MPR).Materials and MethodsMeasurements were performed on 2107 patients who underwent thoracic CT scans in the PLA General Hospital. The lengths of the trachea and the main stem bronchi, and the sizes of the subcarinal angle were obtained through CT or MPR imaging. Multi-variance analyses were performed to detect potential correlations between obtained parameters.ResultsThe mean length of the trachea was 104.9 ± 13.4 mm (107.8 ± 13.2 mm for men and 101.4 ± 12.8 mm for women). The mean lengths of the right and left main stem bronchi were 13.6 ± 4.3 and 48.3 ± 6.5 mm, respectively. The right bronchus angle and the left bronchus angle were 34.9 and 42.5 degrees, respectively. Significant gender differences were found in all the parameters measured except for the angle of the right upper lobe bronchus. There are no statistically significant correlations among these parameters.ConclusionsThe normal reference values and the likely ranges of distribution of the tracheobronchial trees in the Chinese population have been established. Significant gender differences exist in the dimensions of the trachea, with the exception of the Right upper bronchial angle (RUA).

Determination of inter-bronchial and subcarinal angles in fetuses of different gestational age and their clinical implication

Introduction: The trachea-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 developmentaln changes of the respiratory passages.

Assessment of Subcarinal Angle and Factors Determining it by using CT Scan

The present study entitled Assessment of subcarinal angle and factors determining it by using CT scan was done at General Municipal Hospital, Mumbai.

The reliability of chest radiographs in predicting left atrial enlargement

Estimates of left atrial size in patients with suspected cardiac disease play an important role in predicting prognosis and events, as well as treatment decisions. Two methods are commonly used to estimate left atrial size: chest radiography and cardiac ultrasound. This study aims to determine the test characteristics by comparing the use of radiographs to cardiac ultrasound (the gold-standard test). Data from patients older than 18 years admitted to Steve Biko Academic Hospital during 2000-2003 who had both chest radiographs and cardiac ultrasound were included in this cross-sectional, retrospective analysis. Chest radiographs were classified into three quality classes, and the sub-carinal angle (SCA) and sub-angle distance (SAD) were measured twice in all available radiographs by two observers. Intra- and inter-observer variability (three methods) as well as the predictive value of the carinal angle and sub-angle distance measurements were determined using logistic regression (with left atrial enlargement - determined by ultrasound as comparator). Data for 159 patients were available (154 cardiac ultrasounds and 178 chest radiographs). Intra-observer variability for chest radiograph measurements was low with almost perfect concordance (p = 0.000). Inter-observer variability was higher for supine radiographs. Using logistic regression, a linear model was identified which was statistically significant only for erect radiographs. While goodness-of-fit analysis showed that the model fits the data, performance characteristics were poor, with high sensitivity and low specificity, and an area under the ROC curve of 0.62-0.63, depending on type of radiograph and measurement (SCA or SAD). Linearity in the logit of the dependent variable was assessed, and found to be present at the extremes of SCA measurements for the supine radiograph data and in the first three quartiles for erect radiograph data. A nonlinear model determined by fractional polynomial analysis did not perform significantly better than the original linear model. Cut-off values for the SCA of 72° and 84° (erect and supine radiographs, respectively) were found to give the best compromise between sensitivity and specificity. The corresponding cut-off values for SAD were 24.1 and 26.9 mm. Assessment of either SCA or SAD to determine left atrial size was equivalent and repeatable, both with the same observer and between two observers (less so for supine radiographs). While this measure was precise, it was found not to be very accurate. Therefore, chest radiographs are not reliable in predicting left atrial enlargement.

Digital radiographic measurement of the main bronchi: a pilot study

Conventional chest radiographs do not afford consistently good visualisation of the main bronchi and sub-carinal angle. Improved visualisation would facilitate accurate measurement of the airways, definition of normal radiographic anatomy and, possibly, earlier identification of extrinsic compression or displacement. The main objective of this study was to establish whether the paediatric main bronchi and sub-carinal angle could be measured consistently on AP supine chest images obtained using a specific digital radiographic system (DRS). The proximal bronchial diameters were measured on supine DRS chest images of 102 children between the ages of 6 months and 13 years. The left and right main bronchi could be seen clearly and measured in over 90% of cases, with intraclass correlation co-efficients of reliability indicating high intra- and inter-observer agreement. The sub-carinal angle had lower intra- and inter-observer agreement. Supine chest images acquired using DRS facilitate accurate measurement of the main bronchi and sub-carinal angle in children. Further work is required to establish population-specific age-related norms for bronchial dimensions. These could serve as reference standards for early detection of deviations from normal.

In vivo and in vitro morphometry of the human trachea

Most morphometric studies of the human trachea have relied on plain radiographs with their attendant limitations. Reports using computed tomography (CT) have focused on the growing trachea or one particular dimension. The aim of this study was to document the morphometry of the adult trachea in vivo using high-resolution chest CT scans, supplemented by data from cadavers. Sixty anonymised high-resolution chest CT scans (aged 22-88 years, 40 males) were analyzed. Scans were performed using a standardized breath-holding technique in patients with no distorting intrathoracic pathology. Standardized tracheal measurements included: length, maximum antero-posterior and transverse diameters, volume, subcarinal angle, and carinal position in relation to the tracheal midline. Measurements were also made in 10 cadaver tracheas (aged 68-101 years, 7 males). CT data showed that mean tracheal length (males 105.1 +/- 9.8 mm, females 98.3 +/- 8.7 mm), maximum antero-posterior and transverse diameters, and tracheal volume (males 35.6 +/- 6.8 cm3, females 24.7 +/- 6.1 cm3) were all significantly greater in men (P < or = 0.01). The subcarinal angle was very variable (mean 78 +/- 20 degrees , range 36-121 degrees ) and showed no correlation with age or gender. The carina was sited to the left of the tracheal midline in 49 (81%) patients. Cadaver tracheas had 14-19 tracheal rings and the posterior membranous trachea was wider in men (17.7 +/- 4.4 mm vs. 11.8 +/- 3.0 mm, P = 0.07). In conclusion, there is marked sexual dimorphism in the morphometry of the human trachea. The variation in adult tracheal dimensions in vivo is greater than in standard descriptions. These data may be valuable when interpreting chest CT scans and when calculating respiratory dead space.

CT assessment of tracheal carinal angle and its determinants

The aim of this study was to investigate the effect of body habitus, dimensions of the thoracic cavity, location of the carina within the mediastinum, and left atrial size on tracheal carinal angle using CT scan. The study population was drawn from the patients referred to CT scan for various indications. A total of 120 patients (65 men and 55 women; age range 17-85 years; mean age 56 years) who denied a history of prior thoracic surgery, and in whom CT scan excluded pulmonary fibrosis, moderate or severe emphysema, atelectasis, intrathoracic mass or adenopathy, pericardial or pleural effusion were prospectively enrolled. The interbronchial (IBA) and subcarinal (SCA) angles were measured on coronal reformatted images. The presternal and retrovertebral fat thickness, the anteroposterior and transverse diameters of the thorax, the distances from carina to the sternum and to the vertebral column were obtained at the level of carina. Three orthogonal dimensions and the volume of the left atrium were also assessed. The mean interbronchial angle was 77 degrees +/-13 degrees (range 49-109 degrees ) and subcarinal angle was 73 degrees +/-16 degrees (range 34-107 degrees ). IBA positively correlated with the female gender (r=0.25, p=0.007), body mass index (r=0.28, p=0.002), presternal (r=0.40, p=0.001) and retrovertebral fat thickness (r=0.31, p=0.001). The interbronchial angle was significantly greater in obese patients compared with lean patients (p=0.02). Both IBA and SCA were positively correlated with the left atrial volume (r=0.40, p=0.001 and r=0.34, p=0.001, respectively), and its transverse and craniocaudal dimensions. The carina-vertebral column distance inversely correlated with IBA (r=-0.42, p=0.001) and SCA (r=-0.41, p=0.001). The size of the thoracic cavity did not show significant relation to tracheal bifurcation angle. Tracheal bifurcation angle ranges widely in normal subjects, and absolute measurements of the carinal angle is of little diagnostic value. In addition to left atrial enlargement, female gender, obesity and close situs of carina relative to vertebral column are associated with greater tracheal bifurcation angle.