Background Patients with Interstitial Lung Disease (ILD) are more frequently being referred to Pulmonary Rehabilitation (PR) where exercise capacity is measured, often by an Incremental Shuttle Walk Test (ISWT). These patients are frequently limited by severe dyspnoea and exertional desaturation. Available guidelines1 suggest two ISWTs are needed, however this can be time consuming.
Objective To investigate if a practice ISWT is needed for patients with ILD referred to PR.
Methods Patients with ILD recorded on our PR database, who attended a PR assessment and performed 2 ISWTs,1 were selected. Patients were included if they had 2 recorded ISWTs using the same oxygen prescription and mobility aid (if any) between tests and provided written consent. Hospital notes were retrieved, diagnosis confirmed and relevant data extracted and validated.
Results 43 patients (24 male) were included, 18 with Idiopathic Pulmonary Fibrosis. Participants were mean (SD) 72.17(10.54) years, Forced Vital Capacity was 2.28(0.87)l [77.24(25.46)% predicted], Transfer factor for the Lung for Carbon Monoxide 3.60(1.07)ml/mmHg [44.79(12.80)% predicted], median (inter-quartile range) Medical Research Council dyspnoea grade 3.5(3–4) and 29 used oxygen therapy.
Participants achieved 165.12(123.89)m on ISWT1 with post-SaO2 87.86(5.86)%, heart rate 97.03(14.71), Borg breathlessness 4(3–5) and Rated Perceived Exertion (RPE) 13(11.25–15). There was a change of 28.84(31.71)m between the two ISWTs (p < 0.001); 72.1% of patients walked further on their second ISWT. Backward linear regression only explained 42% of this variance (R2. 426).
For those who did not improve, ISWT1 was ≤210 m. Bland-Altman plot showed good agreement between the ISWTs, however the limits of agreement were wide. There was a significant difference in Endurance Shuttle Walk Test levels when calculated at 85% of VO2 peak as estimated from ISWT1 and ISWT2 (p < 0.001).
Conclusions For patients with ILD, we have shown that there are significant differences between the first and second ISWT and therefore a practice ISWT is needed in order to accurately assess exercise capacity, prescribe an exercise programme and ensure services and interventions are correctly evaluated. We were unable to predict those who did not need to complete 2 ISWTs.
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