RESULTS: COPD patients reported that there was no difference between the two cannulas ease of use and adjustment (A=9.2; B=9.7), comfort (A=8.5, B=8.8), stability (A=9.5, B=9.9), or water droplets forming in the cannula (A=8.9, B=9.8). Healthcare professionals reported that there was no difference between the two cannulas ease of use and adjustment (A=7.8; B=8.2), stability (A=9.2, B=9.3), instructions for use (A=8.7, B=8.3), or removing from the patient (A=8.9, B=9.8). Compared to Cannula B, Cannula A was reported to be slightly more noisy for both the patient and healthcare professional groups (scale point difference 1.2 and 1.7 respectively; p<0.01). In the patient group 20% preferred Cannula A, 70% preferred Cannula B and 10% had no overall preference. In the Healthcare professional group 38% preferred Cannula A, 54% preferred Cannula B and 8% had no preference.