Abstract Cardio-pulmonary exercise testing (CPET) has been used to identify dynamic hyperinflation and other ventilatory limitations to exercise in patients with various forms of lung disease. However, little work has been published in characterizing trapped lung physiology on CPET. Here, we present a case of elevated ratio of tidal volume to inspiratory capacity (Vt/IC) on CPET indicative of trapped lung, determined to be the primary cause of a patient’s dyspnea. A 76 year old male with a past medical history of coronary artery disease, obstructive sleep apnea, and remote left-sided empyema presented with dyspnea on exertion. Chest imaging found a left-sided pleural effusion with moderate pleural thickening, not improved with subsequent thoracentesis. On pleural manometry, the patient was found to have trapped lung physiology with a pleural elastance of 1676 cmH2O/L. He underwent extensive other evaluation for dyspnea and was not found to have other obvious contributors. He was therefore referred for CPET. He reached VO2/kg of 16.3 ml/min/kg when normalized to ideal body weight. He did not appear to reach anaerobic threshold. Based on a calculated MVV of 70 L/min, his breathing reserve was 20.7 L/min (29.6%). Notably, he had an elevated Vt/IC of 88% attributed to known trapped lung physiology. In absence of other significant contributors to dyspnea, the patient underwent robotic-assisted thoracoscopic decortication to relieve his trapped lung and improve symptoms. Unfortunately, a bypass graft was disrupted during surgery, causing arterial hemorrhage which could not be repaired. He ultimately transitioned to comfort care and expired. Vt/IC is used to evaluate ventilation restriction related to dynamic hyperinflation in patients with obstructive disease, but fixed restrictive mechanical limitations to inspiratory capacity are rare and often overlooked. The fixed limitation prevents physiologically appropriate increases in tidal volume, causing sensations of dyspnea that can distress patients or even lead to significant exercise limitation. Early use of CPET may help elucidate this physiology, allowing for faster diagnosis and intervention. Treatment for trapped lung is typically surgical and requires extensive risk-benefit analysis. In this patient, despite a recorded peak VO2/kg suggesting appropriate cardiopulmonary fitness for surgery, a technical complication ultimately led to death, highlighting the risks of thoracic surgery. This abstract is funded by: none
Freije et al. (Fri,) studied this question.