Oxygen can relieve dyspnoea in mildly and non-hypoxaemic people with COPD who would not otherwise qualify for home oxygen therapy. Given the significant heterogeneity among the included studies, clinicians should continue to evaluate patients on an individual basis until supporting data from ongoing, large randomised controlled trials are available.
Evaluation of pulsed dose oxygen delivery during exercise in patients with severe chronic obstructive pulmonary disease.
Oxygen conserving devices may lead to substantial increases in the duration of oxygen provided. A study was undertaken to compare the performance of a pulsed dose oxygen delivery (PDOD) system with continuous flow oxygen or air during a maximal walking test.
                Fourteen patients with chronic obstructive pulmonary disease (COPD) and arterial oxygen desaturation on exercise (mean (SD) forced expiratory volume in one second (FEV1) 0.83 (0.28) 1, arterial oxygen pressure (PaO2) 8.38 (1.24) kPa, arterial carbon dioxide pressure (PaCO2) 5.95 (0.86) kPa) were randomised to perform a walking test using air administered via a cylinder or continuous flow oxygen at 2 l/min or by a PDOD system.
                There was no significant difference in the mean arterial oxygen saturation (SaO2) using the PDOD system or with continuous flow oxygen (p = 0.33). Patients showed greatest desaturation whilst walking with the air cylinder (SaO2 79.2 (8.59)%) which was significantly different from the desaturation with both continuous flow oxygen (87.6 (5.85)%, p = 0.001) and PDOD (85.6 (7.36)%, p = 0.004). There was no significant difference between the distance walked using oxygen delivered at 2 l/min by continuous flow or via the PDOD (p = 0.72; CI 0.34 to 1.08). The mean (SD) distance walked on continuous flow oxygen (203.6 (106.1) m) and PDOD (207.9 (109.8) m) was significantly greater than the distance walked with the air cylinder (188.6 (110.02) m); (1.12 fold increase in distance, CI 1.01 to 1.23, p = 0.02, and 1.14 fold increase in distance, CI 1.01 to 1.28, p = 0.03, respectively).
                These findings suggest that the pulsed dose oxygen conserving device was as effective as continuous flow oxygen in maintaining arterial oxygen saturation and that the use of this device was associated with similar improvements in exercise tolerance to patients taking continuous flow oxygen therapy.