Chart 1: Oxygen prescription for acutely hypoxaemic patients in hospital. Chart 1: Oxygen prescription for acutely hypoxaemic patients in hospital. ABG, arterial blood gas; COPD, chronic obstructive pulmonary disease; Fio2, fraction of inspired oxygen; ICU, intensive care unit; NIV, non-invasive ventilation; Pco2, carbon dioxide tension; Spo2, arterial oxygen saturation measured by pulse oximetry. B R O’Driscoll et al. Thorax 2008;63:vi1-vi68 Copyright © BMJ Publishing Group Ltd & British Thoracic Society. All rights reserved.