BACKGROUND: A study was carried out to determine whether rating of dyspnoea by means of a visual analogue scale during a progressive exercise test is affected by the subject's awareness of the progressive nature of the protocol. METHODS: Nineteen patients with chronic obstructive lung disease (FEV1 mean (SE) 1.06 (0.07) 1) were studied. A preliminary incremental test was carried out with a work rate increasing by 10 watts every minute until the subject could no longer exercise, to determine the maximum work load (Wmax) and to anchor the upper end of the visual analogue scale. This was followed by two exercise tests performed one day apart in randomised sequence, with two different protocols. One was a 12 minute protocol that included two sudden bursts of three minute high intensity exercise, up to the subject's Wmax, each preceded by three minutes of low level exercise. The other test was a conventional three minute incremental test lasting 12 minutes. On both study days the only information given to the subject about the temporal profile of load was that a change would be made every three minutes. The relation between dyspnoea, as assessed by the visual analogue scale, and ventilation, measured during high intensity or progressive exercise, was studied. RESULTS: The mean (SE) rates of increase of dyspnoea with increasing ventilation (% of line length 1(-1) min) obtained by linear regression analysis were similar for the two tests (2.86 (0.20) for progressive exercise and 2.87 (0.25) for high intensity exercise); it was 2.59 (0.25) for the initial burst of high intensity exercise when the data on this were analysed separately. In six subjects with stable disease studied again two months later the reproducibility of the rating of dyspnoea was reasonably good for both protocols. CONCLUSION: The results suggest that in most patients with chronic obstructive lung disease the assessment of exercise induced dyspnoea by means of a visual analogue scale during a progressive exercise test is not affected by the subject's awareness of the progressive increase in work intensity.
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