A conservation device for oxygen therapy in COPD.

Patients with hypoxaemia secondary to chronic obstructive pulmonary disease (COPD) are frequently prescribed oxygen therapy for short- and long-term domiciliary use. Oxygen administered via nasal cannulae incorporating a small collapsible reservoir ("Oxymizer", Chad Therapeutics Inc., CA, USA) improves transcutaneous oxygen tensions in the short-term when compared to standard nasal cannulae. The effects of this device on arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions was assessed over 60 min in twelve patients with severe hypoxaemia (6.2 +/- 0.9 kPa, mean +/- SD) and hypercapnia (7.5 +/- 1.2 kPa). Following baseline measurements, oxygen was administered using standard nasal cannulae, and further measurements were made at 15 min intervals for at least 45 min. Patients were then changed to the "Oxymizer" and measurements continued at 15 min intervals for a further 60 min. Mean PaO2 increased by 1.1 +/- 0.78 kPa (p less than 0.001), using the "Oxymizer", but PaO2 was significantly greater after 15 min on the device than after 60 min (p less than 0.05). There was no change in PaCO2 (p greater than 0.05). The "Oxymizer" increases PaO2 compared with standard cannulae, but the effect may not be sustained.