Saber-sheath trachea constitutes a morphologic-functional disorder of the intrathoracic segment, characterized by an abnormal configuration of the tracheal cartilages, where the coronal diameter represents less than 2/3 of the sagittal, with narrowing of the front bow and collapse of the side wall during coughing and stressed expiration. Just as it happens in the case of semilunar configuration of the thacheal expiratory collapse syndrome, it is more common in patients with COPD, when the clinicradiologic appearance usually masks the seriousness of the functional disorder. The authors demonstrate the clinic-tomographic-endoscopic-functional correlation in the case of a 43-year-old female patient suffering from severe chronic obstructive respiratory failure whose clinic-radiologic condition masked the seriousness of the dysfunction, emphasizing the need for systematic investigation of the tracheal dynamics in this type of case.

Community-acquired pneumonia continues to be the acute infectious disease that has the greatest medical and social impact regarding morbidity and treatment costs. Children and the elderly are more susceptible to severe complications, thereby justifying the fact that the prevention measures adopted have focused on these age brackets. Despite the advances in the knowledge of etiology and physiopathology, as well as the improvement in preliminary clinical and therapeutic methods, various questions merit further investigation. This is due to the clinical, social, demographical and structural diversity, which cannot be fully predicted. Consequently, guidelines are published in order to compile the most recent knowledge in a systematic way and to promote the rational use of that knowledge in medical practice. Therefore, guidelines are not a rigid set of rules that must be followed, but first and foremost a tool to be used in a critical way, bearing in mind the variability of biological and human responses within their individual and social contexts. This document represents the conclusion of a detailed discussion among the members of the Scientific Board and Respiratory Infection Committee of the Brazilian Thoracic Association. The objective of the work group was to present relevant topics in order to update the previous guidelines. We attempted to avoid the repetition of consensual concepts. The principal objective of creating this document was to present a compilation of the recent advances published in the literature and, consequently, to contribute to improving the quality of the medical care provided to immunocompetent adult patients with community-acquired pneumonia.

Keywords: Pneumonia; Diagnosis; Epidemiology; Practice guideline; Primary prevention.