Introduction: Pulmonary rehabilitation (PR) improves dyspnea and the quality of life of patients with interstitial lung diseases (ILD). Optimal assessment includes cardiopulmonary exercise testing (CPET), but its access is limited. Accuracy of field tests like the 6-minute stepper test (6MST) to personalize PR intensity in ILD have never been studied.
 
Aims and objectives: The aim of this retrospective bicentric study was to develop a prediction equation to set intensity in patients with ILD attending PR, based on the 6MST.
 
Methods: The following relationships were analyzed: mean heart rate (HR) during the first (HR1-3) and last (HR4-6) 3 minutes of the 6MST and HR at the ventilatory threshold (HRvt) from CPET, workload at 6MST (W6MST = Weight*step count at the end of 6MST) and at CPET maximal workload (Wmax).
 
Results: In the 21 patients included, we showed a strong correlation between HR1-3 and HR4-6 and HRvt(r=0.619 p=0.003 and r=0.814 p<0.0001 respectively). The prediction equations were HRvt = 0.5637× HR1-3 + 48.91 and HRvt = 0.7119 × HR4-6 + 27.60. Median absolute difference between HR1-3 or HR4-6 and HRvt was significantly lower for HR4-6 (5,76 (IC95% [3,08 ;12,61] vs 3,316 (IC95% [0,90 ;8,12]) p<0.05). A significant correlation was found between W6MST and Wmax (r=0.556 p=0.0088). The prediction equation was Wmax = 0.001139 × W6MST + 60.12. Mean absolute difference between Wmax and Wmax predicted from W6MST was 19,78 IC95% [13,63 ;25,94].

Conclusion: 6MST could be interesting to individualize aerobic training in patients with ILD. Our results need to be confirmed in a prospective validation cohort.