• Fabien Maldonado and Mary Klecka.
• Chest. 2014 Mar 1;145(3 Suppl):267A.

Session TitlePleural CasesSESSION TYPE: Case ReportsPRESENTED ON: Sunday, March 23, 2014 at 09:00 AM - 10:00 AMINTRODUCTION: Patients with large pleural effusions often experience dramatic relief from dyspnea after thoracentesis. While this is well-recognized, the physiological basis for such relief remains poorly understood. One commonly held belief is that thoracentesis allows for lung reexpansion, ventilation of previously atelectatic lung, and improved ventilation-perfusion matching, subsequently leading to dyspnea relief. This contrasts with the concept of "length-tension inappropriateness," which posits chest wall mechanics best explain dyspnea relief.Case PresentationA 46-year-old man with fibrosing mediastinitis developed progressive dyspnea at rest despite treatment. Computed tomography (CT) revealed a pleural effusion occupying half the left hemithorax. Ultrasound revealed an inverted diaphragm (Fig 1). CT angiogram with venous protocol revealed complete obstruction of both left-sided pulmonary veins (Fig 2). A quantitative perfusion scan revealed negligible left lung perfusion. The patient reported dramatic improvement in his dyspnea post-thoracentesis such that he could perform strenuous exercise. As the effusion re-accumulated, his dyspnea at rest recurred. He ultimately underwent tunneled indwelling catheter placement with complete dyspnea relief.DiscussionThis is the first case to our knowledge to describe dramatic improvement of dyspnea after thoracentesis in a patient with absent perfusion to the affected lung. This patient's improvement cannot be attributed to improved gas exchange and suggests the primary physiologic basis for his relief is a change in respiratory system mechanics and/or work of breathing. Brown described dyspnea relief after thoracentesis despite lack of improvement in lung volumes or gas exchange1. Estenne reported altered pressure-volume curves after drainage, with inspiratory muscles generating more negative pressures at any lung volume. This was secondary to decreased thoracic cage volume2. It was hypothesized thoracentesis allowed previously stretched muscles to operate at more favorable portions of their length-tension curves. This may apply to the diaphragm, which is occasionally inverted in large effusions causing paradoxical motion, a finding associated with better symptomatic outcomes after thoracentesis3.ConclusionsOur case established that dyspnea relief after thoracentesis likely results from changes in chest wall mechanics and/or work of breathing. This observation has direct clinical implications and could inform therapeutic decisions.Reference #1: Brown NE et al. Changes in pulmonary mechanics and gas exchange following thoracentesis. Chest. 1978; 74: 540-42Reference #2: Estenne M et al. Mechanism of relief of dyspnea after thoracentesis in patients with large pleural effusions. Am J Med. 1983; 74(5):813-9Reference #3: Wang LM et al. Improved lung function after thoracentesis in patients with paradoxical movement of a hemidiaphragm secondary to a large pleural effusion. Respirology. 2007; 12(5):719-23DISCLOSURE: The following authors have nothing to disclose: Mary Klecka, Fabien MaldonadoNo Product/Research Disclosure Information.

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