838 Not All Hypercapnia is COPD

Introduction Sleep breathing disorder related to isolated unilateral or bilateral diaphragmatic dysfunction (DD), in the absence of a generalized neuromuscular disorder, is not well understood and often under-recognized. There have been only a few cases reported of apneas and hypoponeas during REM sleep due to diaphragmatic dysfunction. We present here, a case of an 62 year-old man who developed acute hypercapnic respiratory failure with presumed COPD exacerbation requiring invasive ventilation. Report of case(s) A 62-year-old man was found on the sidewalk extremely short of breath and was intubated in the emergency department. Initial post-intubation arterial blood gas showed pH 7.1, pCO2 82, pO2 263, CO3 25.5. CXR showed no infiltrates. Echocardiography showed EFof 55%-65%. Long-term tobacco use supported the picture of COPD exacerbation. However, PFT was within normal limits. HSAT one year prior which showed severe OSA with AHI 52.6 event per hour. Patient had not pursued positive airway pressure (PAP) titration study afterward. In ICU, he was treated for presumed COPD exacerbation and successfully weaned off invasive ventilation. Inpatient PAP titration study recommended IPAP 12 and EPAP 8 cm H20. A fluoroscopy of the diaphragm was performed and showed that the right diaphragm had limited mobility. Electromyogram did not show generalized myopathy. Conclusion In conclusion, this case report describes the presentation of sleep disordered breathing seen in patients with unilateral diaphragmatic palsy. In these patients, the respiratory events seen are mainly hypopneas and desaturations, worse in REM sleep and supine position. This was an unusual presentation of a patient with untreated OSA and unilateral diaphragmatic palsy. A characteristic finding in these patients is worsening of the OSA in supine position. This has been reported in several studies and was seen in our case as well. This case underscores the need for critical thinking and diagnostic reasoning in the evaluation of a patient with hypercapnic respiratory failure and consider a wide differential and not only COPD exacerbation as the cause. Unilaterally diaphragmatic palsy is a rare cause of hypercapnic respiratory failure but must be considered when seen with obstructive sleep apnea with predominantly hypopneas and hypoxemia out of proportion of the respiratory events. Support (if any):