RESULTS: 496 patients were included of which 96.7 % were male with mean age 74.0 years. 459/496 (92%) of patient were started on oxygen based on O2 saturation less than 88%, 36/496(7.25%) based on nocturnal pulse oximetry, one patient for cluster headache. 336/496 (67%) patients were given o2 therapy for 18-24hr, 54/496 (10%) for exertion, 62/496 (12.5%) for nocturnal hypoxia and 45/496 (9%) for unclear duration. Majority of home o2 therapy was initiated in an outpatient setting (343/496 69.2%). 103 patients (20.7%) had their home oxygen discontinued at 3 months as they no longer needed it. Discontinuation rate at 3 months was significantly higher (33%) in patient started on oxygen as inpatients compared to those started as outpatients (15%) (p < 0.0001, Fishers exact test). In those patients in whom oxygen was continued at 3 months, 353/378(93.4%) had a diagnosis for hypoxia. Pulmonary diagnoses were primarily responsible for oxygen prescriptions 310/353 (82.0%). Obstructive lung disease was the most common diagnosis (228/353 64.58%) followed by sleep apnea with nocturnal hypoxia despite CPAP (45/353), ILD (16/353), malignancy (12/353) and miscellaneous (12/343). Of the patients with pulmonary diagnosis 215/310 (69.35%) had pulmonary function testing. Among patients with obstructive lung disease 167/228 (73.24%) had pulmonary function testing out of which 135/167 (80.83%) had evidence of obstruction on spirometry.