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Introduction The standard 6-minute walk test (6MWT) involves asking the participant to walk as far as they can around a straight flat course (usually a corridor) for 6 minutes whilst their oxygen saturation (SpO2), heart rate (HR) and total distance walked (6MWD) are recorded. Many patients will walk slower during their normal daily activity, and therefore may not be an accurate assessment for their requirement for ambulatory oxygen therapy (AOT). We aimed to identify any clinical differences between the standardised 6-minute walk test and a proposed normal-speed 6-minute walk test.Methods Two 6MWT were performed under the same conditions with instructions to either walk either as far as they can (M-6MWT, following international guidelines), or at their normal walking pace (N-6MWT) for 6 minutes. A wireless SpO2 probe and tablet were used to continuously measure SpO2, HR and a lap counter to record total distance. A modified BORG scale was used to assess perceived breathlessness and fatigue, as well as a standard activity questionnaire to assess normal daily activities. A minimum 10-minute rest period was provided between tests.Results There was a statistically significant increase in the 6MWD with the M-6MWT compared with the N-6MWT ( figure 1A: mean 6MWD 420 m vs. 352 m) with a corresponding small, yet statistically significant, decrease in the SpO2 nadir (figure 1B; mean SpO2 nadir 89.0% vs. 88.4%). The change in SpO2 nadir was more marked when only participants that met eligibility criteria for AOT (SpO2 nadir <90% and ≥4% decline from baseline) in the M-6MWT (n=41) were included in the analysis. Furthermore, within this group, 7 participants (17%) would not have met eligibility criteria for AOT on the N-6MWT.Abstract P39 Figure 1Differences in 6MWD and SpO2 nadir between the M-6MWT and N-6MWT. (A) paired data showing the 6MWD in meters (m) achieved for each participant in the M-6MWT (purple) and N-6MWT (teal) with the mean value indicated by the horizontal dashed line. The total number of participants that demonstrated an increase, decrease or identical 6MWD between the two tests are shown to the right (n=82); (B) SpO2 nadir between the M-6MWT (purple) and N-6MWT (blue) for each participant. The total number of participants that demonstrated an increase, decrease or identical SpO2 between the two tests are shown to the right (n=81). Statistical analysis was performed using a paired t-test. In all cases, p<0.05 was considered statistically significantConclusion These results suggest that the instructions given for the 6MWT may have clinical impact for the assessment of both functional capacity (6MWD) and for ambulatory oxygen requirements. These data highlight the importance of standardisation of testing to support robust clinical decision making. Further work is required to assess if the modified test provides a better indication for ambulatory oxygen, but the M-6MWT will show a better indication of true functional capacity from the 6MWD.