TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: The diaphragm is the primary muscle of respiration. Patients with bilateral diaphragmatic paralysis can present with dyspnea on exertion and be misdiagnosed as acute heart failure. Thyroid myopathy can involve diaphragm and require a high index of suspicion in patients with symptoms of heart failure with negative workup. CASE PRESENTATION: A 47-year-old male with a past medical history of coronary artery bypass grafting, and heart failure presented with dyspnea on exertion and orthopnea for one month. He was recently admitted with the same complaints and was discharged on an increased dose of furosemide with no response. On presentation, physical exam revealed orthopnea and bilateral decreased air entry at the lung bases. Oxygen saturation was 86% on room air. Arterial blood gas results showed pH 7.31, PCO2 61 on 100% FIO2. Laboratory data, including complete blood count and comprehensive metabolic profile, were unremarkable. EKG showed normal sinus rhythm and transthoracic echocardiogram showed an ejection fraction of 62%. Chest x-ray showed elevation of right hemidiaphragm (figure-1). He was treated with intravenous Lasix and BiPAP, but symptoms didn't improve, which prompted further workup, including a fluoroscopic "sniff test," which showed the paradoxical motion of both hemidiaphragm consistent with diaphragmatic paralysis. TSH level came back 306.0 µIU/ml, free T4 level was 0.32 ng/dL. Pulmonary function tests depicted mild obstructive and moderate restrictive lung disease (figure-2). Pt was treated with levothyroxine and was discharged on levothyroxine and trilogy after symptoms started improving. He showed significant improvement at one month's follow-up. DISCUSSION: Bilateral diaphragmatic paralysis primarily presents with shortness of breath on exertion and orthopnea within minutes of recumbency. The diagnosis is challenging as symptoms can be misinterpreted as a sign of heart failure; hence it is prudent to rule out acute heart failure. Severe hypothyroidism presenting as bilateral diaphragmatic paralysis is rarely reported in the literature, which decreases the activity of acid maltase, causing thyroid myopathy. The diagnosis can be made by paradoxical motion of hemidiaphragm on "sniff test," however, the measurement of trans-diaphragmatic pressure is the gold standard. The treatment depends on etiology and severity. Hypothyroidism should be treated promptly, and the use of small portable ventilators such as trilogy are helpful to assist breathing. In patients with intact phrenic nerve with no myopathy, phrenic nerve pacing can also be considered. CONCLUSIONS: Signs and symptoms of diaphragmatic paralysis can mimic heart failure. Physicians should maintain a high index of suspicion to workup for hypothyroidism and paralysis of the diaphragm in patients with typical presentation in the absence of cardiac or pulmonary etiology, as early diagnosis and treatment have good outcomes. REFERENCE #1: Thulaseedharan NK, Geetha P, Arathi N, et al. An unusual cause of orthopnoea-hashimoto's thyroiditis presenting as bilateral diaphragmatic palsy. Respiratory Medicine Case Reports. 2017;21:132-134. doi:10.1016/j.rmcr.2017.04.016 DISCLOSURES: No relevant relationships by Shaji Baig, source=Web Response No relevant relationships by Aneeba FAROOQi, source=Web Response No relevant relationships by Hafiz Jeelani, source=Web Response