High concentration oxygen in Chronic Obstructive Pulmonary Disease (COPD): Study 2

INTERVENTION: 50% oxygen administration for 30 minutes via a full‐face continuous positive airway pressure mask without positive airway pressure. Followed by a 30 minute washout period. CONDITION: COPD PRIMARY OUTCOME: Transcutaneous carbon dioxide level, as measured by a Sentec monitor. SECONDARY OUTCOME: Change in transcutaneous carbon dioxide greater than or equal to 4mmHg, as measured by the Sentec monitor. Alveolar minute ventilation, calculated using data from a flow sensor attached to the expiratory port of the participant's mask and volumetric capnography. Alveolar volume, calculated using data from a flow sensor attached to the expiratory port of the participant's mask and volumetric capnography. Capillary blood gas value, measured after completion of second washout while Sentec monitor is in place. Change in transcutaneous carbon dioxide greater than or equal to 10mmHg, as measured by the Sentec monitor. ; Effect of baseline transcutaneous carbon dioxide (measured via Sentec) and FEV1 (measured via spirometry) on outcomes. End tidal carbon dioxide, calculated using the capnography sensor attached to expiratory port of participant's mask. Evaluation of outcomes above in comparison to results from a study of similar design in patients with bronchiectasis (ACTRN12615000971538). Heart rate, measured from the Sentec. ; Minute ventilation, calculated using data from a flow sensor attached to the expiratory port of the participant's mask. Oxygen saturations, as recorded on the Sentec via continuous electronic recording data download. Respiratory rate, measured from capnography equipment. Tidal volume, calculated using data from a flow sensor attached to the expiratory port of the participant's mask and volumetric capnography. Transcutaneous carbon dioxide level as measured by Sentec and with drift correction by Sentec computer software Transcutaneous carbon dioxide level, as measured by a Sentec monitor. Transcutaneous carbon dioxide level, measured by Sentec during capillary blood gas measurement. Volume of dead space to tidal volume, calculated using data from a flow sensor attached to the expiratory port of the participant's mask and volumetric capnography. Volume of dead space, calculated using data from a flow sensor attached to the expiratory port of the participant's mask and volumetric capnography. INCLUSION CRITERIA: COPD, as diagnosed by a doctor.