الفهرس 
Embryology and Anatomy of Tracheobronchial TreeOnly 14 pages are availabe for public view
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Abstract
Expiratory central airway collapse is defined as more than 50% reduction of the horizontal cross-sectional area at expiration and is due to pure tracheobronchomalacia (TBM) or excessive dynamic airway collapse (EDAC). The airway in pediatrics can be affected by both congenital and acquired lesions that result in fixed or dynamic airway narrowing. One of the more difficult conditions to diagnose is dynamic airway narrowing but advances in diagnostic modalities including flexible bronchoscopy and dynamic radiographic studies allow increased recognition and differentiation of dynamic and fixed airway abnormalities. The most frequent symptoms of tracheal collapse are cough, wheezing, stridor, dyspnea and recurrent chest infections. This complicates diagnosis, as it mimics other and more common lung diseases. The gold standard for diagnosing excessive tracheal collapse is still evaluation of the cross-sectional area of the trachea before and at forced expiration or cough during flexible bronchoscopy. However, it is not always feasible and cine CT scan is an alternative diagnostic tool. The aim of this work was to: Determine the prevalence of expiratory central airway collapse (ECAC) in children undergoing flexible fiberoptic bronchoscopy; determine the role of dynamic inspiratory–expiratory imaging with CT in patients with suspected expiratory central airway collapse and, to assess FEMOS classification in pediatric patients for assessing patients with ECAC and monitoring different diagnostic modalities in children with ECAC. This study showed that not all airway collapse represents tracheomalacia. Inspection of the trachea in tracheomalacia should reveal abnormal cartilaginous structure. Airway collapse however may also occur simply as a result of laxity of the posterior membrane. Thus, we try to emphasize a new entity, referred to here as excessive dynamic airway collapse (EDAC) in which the tracheal collapse is entirely the result of the laxity of the posterior membranous portion of the trachea with structurally intact tracheal cartilage. Patients and Methods: This study was carried out on 113 patients below the age of 16 years who have symptoms and signs suggestive of ECAC in order to assess the accuracy of dynamic expiratory CT for detecting ECAC using bronchoscopy as the diagnostic “gold standard”. Thirty eight patients (20 male and 18 female) were diagnosed with ECAC by flexible fiberoptic bronchoscopy. They underwent cine CT chest within 2 weeks of diagnosis. Patients who weren’t diagnosed as ECAC by bronchoscopy didn’t proceed any further investigations in the study. On bronchoscopy bowing of the cartilage wall as well as excessive invagination of the posterior wall of the trachea and bronchi to the point where the bronchoscope cannot be advanced any further were observed and the percentage of collapse was registered in order to be classified into mild, moderate and severe according to FEMOS classification. End-inspiratory and dynamic expiratory cross-sectional airway areas at aorta, carina and bronchus intermedius were recorded in order to assess the degree of dynamic airway collapse by cine CT in 23 of the 38 patients included in the study. The percentage of luminal collapse (LC) was calculated according to the method proposed by Lee et al: LC= (IA-EA)/IA x 100. ECAC was diagnosed if LC was 50% or greater. All patients were subjected to thorough medical history and clinical examination with special emphasis on chest examination. Statistical analysis of the data was done using SPSS, using Kolmogorov-Smirnov test, Shapiro-Wilk test and D’Agstino test, also Histogram and QQ plot were used for normality. Mean and standard deviation for continuous variables with normal distribution, median and interquartile range for continuous variables with non-normal distributions and as proportions (percentages) for categorical variables. Results: Thirty eight patients (20 male and 18 female; mean age, 13 months with range, 3 months to 3.25 years) were actually diagnosed with ECAC, indicating a prevalence of 33.6% of the disease. The most common presenting symptoms were recurrent chest infection in 14 patients (36.8%), stridor in 13 patients (34.2%), rattling and recurrent wheeze each in 6patients (15.8%), aspiration and wet cough each in 5 patients (13.2%) , barking cough 4patients (10.5), persistent wheeze in 3 patients (7.9%) and the least symptom was cyanosis in 1 patient (2.6%). CT correctly diagnosed ECAC in 32 of 38 patients, indicating a sensitivity of 84.2% ; 16 (50%) patients was diagnosed as EDAC, 14 (43.8%) patients as tracheomalacia, 1 (3.1%) patient as tracheobronchomalacia and 1 (3.1%) patient as bronchomalacia. Comparing between the degree of airway collapse at the levels of aorta, carina and bronchus intermedius, we found that the degree of airway collapse was higher at the level of carina in comparison to that at the aortic and bronchus intermedius level.