Factors predicting progression of exercise training loads in people with interstitial lung disease

High intensity interval training versus moderate intensity continuous training for people with interstitial lung disease: protocol for a randomised controlled trial

Background

Interstitial lung disease is a debilitating condition associated with significant dyspnoea, fatigue, and poor exercise tolerance. Pulmonary rehabilitation is an effective and key intervention in people with interstitial lung disease. However, despite the best efforts of patients and clinicians, many of those who participate are not achieving clinically meaningful benefits. This assessor-blinded, multi-centre, randomised controlled trial aims to compare the clinical benefits of high intensity interval exercise training versus the standard pulmonary rehabilitation method of continuous training at moderate intensity in people with fibrotic interstitial lung disease.

Methods

Eligible participants will be randomised to either a standard pulmonary rehabilitation group using moderate intensity continuous exercise training or high intensity interval exercise training. Participants in both groups will undertake an 8-week pulmonary rehabilitation program of twice-weekly supervised exercise training including aerobic (cycling) and strengthening exercises. In addition, participants in both groups will be prescribed a home exercise program.

Outcomes will be assessed at baseline, upon completion of the intervention and at six months following the intervention by a blinded assessor. The primary outcome is endurance time on a constant work rate test. Secondary outcomes are functional capacity (6-min walk distance), health-related quality of life (Chronic Respiratory Disease Questionnaire (CRQ), St George’s Respiratory Questionnaire idiopathic pulmonary fibrosis specific version (SGRQ-I), breathlessness (Dyspnoea 12, Modified Medical Research Council Dyspnoea Scale), fatigue (fatigue severity scale), anxiety (Hospital Anxiety and Depression Scale), physical activity level (GeneActiv), skeletal muscle changes (ultrasonography) and completion and adherence to pulmonary rehabilitation.

Discussion

The standard exercise training strategies used in pulmonary rehabilitation may not provide an optimal exercise training stimulus for people with interstitial lung disease. This study will determine whether high intensity interval training can produce equivalent or even superior changes in exercise performance and symptoms. If high intensity interval training proves effective, it will provide an exercise training strategy that can readily be implemented into clinical practice for people with interstitial lung disease.

Trial registration ClinicalTrials.gov Registry (NCT03800914). Registered 11 January 2019, https://clinicaltrials.gov/ct2/show/NCT03800914

Australian New Zealand Clinical Trials Registry ACTRN12619000019101. Registered 9 January 2019, https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=376050&isReview=true

Oxygen supplementation during exercise improves leg muscle fatigue in chronic fibrotic interstitial lung disease

BACKGROUND

Exercise-induced hypoxaemia is a hallmark of chronic fibrotic interstitial lung disease (f-ILD). It remains unclear whether patients' severe hypoxaemia may exaggerate locomotor muscle fatigue and, if so, to what extent oxygen (O₂) supplementation can ameliorate these abnormalities.

METHODS

Fifteen patients (12 males, 9 with idiopathic pulmonary fibrosis) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) while breathing medical air. Fifteen age-matched and sex-matched controls cycled up to patients' Tlim. Patients repeated the exercise test on supplemental O₂ (42%±7%) for the same duration. Near-infrared spectroscopy assessed vastus lateralis oxyhaemoglobin concentration ((HbO₂)). Pre-exercise to postexercise variation in twitch force (∆Tw) induced by femoral nerve magnetic stimulation quantified muscle fatigue.

RESULTS

Patients showed severe hypoxaemia (lowest O₂ saturation by pulse oximetry=80.0%±7.6%) which was associated with a blunted increase in muscle (HbO₂₎ during exercise vs controls (+1.3±0.3 µmol vs +4.4±0.4 µmol, respectively; p<0.001). Despite exercising at work rates ∼ one-third lower than controls (42±13 W vs 66±13 W), ∆Tw was greater in patients (∆Tw/external work performed by the leg muscles=-0.59±0.21 %/kJ vs -0.25±0.19 %/kJ; p<0.001). Reversal of exertional hypoxaemia with supplemental O₂ was associated with a significant increase in muscle (HbO₂₎, leading to a reduced decrease in ∆Tw in patients (-0.33±0.19 %/kJ; p<0.001 vs air). Supplemental O₂ significantly improved leg discomfort (p=0.005).

CONCLUSION

O₂ supplementation during exercise improves leg muscle oxygenation and fatigue in f-ILD. Lessening peripheral muscle fatigue to enhance exercise tolerance is a neglected therapeutic target that deserves clinical attention in this patient population.