This is a 54 year old male patient with an idiopathic pulmonary fibrosis, who called today with worsening dyspnea for 3 days. He had been in unusual state of good health at baseline respiratory status (using 4L nasal canula at rest and 6L with exertion) when 3 days prior to admission, he hugged his cousin who has rats for pets and also the heat came up from the basement of his house. He feels that with these two events, his breathing became acutely worse and he is concerned for allergen exposure. He denies any sick contacts, fevers, chills, rhinorrhea. He did receive flu and pneumovax vaccines.  He has had a recent admission last month with progressive dyspnea on exertion. The computed tomography revealed increased ground glass opacity in lower lobes superimposed on pulmonary fibrosis with elevated eosinophils peripherally (12%). A bronchoalveolar lavage was also positive for eosinophils. He was started on high dose steroids (prednisone 60mg) with plan for close outpatient follow up for eosinophilic lung disease. He was discharged on 2-3L nasal canula. He then represented to the emergency department for spontaneous pneumomediastinum of unclear etiology.  On day of current admission, the patient called his pulmonologist complaining of worsening shortness of breath since Saturday. Yesterday he was at pulmonary rehab and desaturated to the 70s on 6L with minimal exertion, and he is currently on 4L nasal canula at rest.  No sick contacts recently. He was asked to go to ED.  In the ED, initial vs were: 98.3, 96, 144/97, 24, 97% 6L NC.