Trapped Lung and Pneumothorax ex Vacuo Presenting as Refractory Hypercapnic Respiratory Failure in a Hemodialysis Patient: A Case Report

Abstract

Trapped lung is a form of non-expandable lung caused by fibrotic restriction of the visceral pleura, failing lung re-expansion despite adequate pleural drainage. Pneumothorax ex vacuo may occur following fluid evacuation and should be distinguished from conventional pneumothorax. We report a 69-year-old man with end-stage renal disease on maintenance hemodialysis, diabetes mellitus, peripheral vascular disease, and multiple comorbidities who presented with progressive dyspnea, altered mental status, and severe hypercapnic respiratory failure. Arterial blood gas analysis showed a pH of 7.15, PaCO₂ of 81 mmHg, and HCO₃⁻ of 13 mmol/L. BiPAP resulted in initial improvement in hypercapnia and mental status; however, the patient remained ventilator-dependent. A right-sided chest tube subsequently drained approximately 2300 mL of transudative pleural fluid, without significant lung re-expansion. Chest CT demonstrated pneumothorax ex vacuo, thickened visceral pleura, and chronically collapsed right lung, supporting the diagnosis of trapped lung. Despite continued ventilatory support, the patient developed progressive respiratory fatigue and required invasive mechanical ventilation. Thoracic surgery deemed decortication inappropriate because of his poor physiological reserve and advanced comorbidities. The patient subsequently developed refractory cardiorespiratory failure and died. This case highlights trapped lung with pneumothorax ex vacuo as an under-recognized cause of refractory hypercapnic respiratory failure. It emphasizes that failure of lung re-expansion after pleural drainage should prompt consideration of non-expandable lung physiology, even when the pleural effusion is transudative.