Development; Feasibility/Safety and Validation of the Alfred Step Test Exercise Protocol (A-STEP) Developed for Adults With Cystic Fibrosis:

Detailed Summary

Exercise testing has become clinically important in the management and ongoing evaluation of patients with Cystic Fibrosis (CF) with higher rates of exercise tolerance and participation previously linked to lower mortality risk (1). Lower exercise capacity generally correlates with more severe lung disease (2,3) and landmark studies suggest that low exercise capacity as measured by peak oxygen capacity (VO2peak) and rate of decline in lung function (FEV1) are strong predictors of mortality (1,4). However not all studies have found pulmonary function tests (PFTs) to be reliable predictors of maximal exercise capacity (5), especially in relatively well preserved lung function (6,7). The wide distribution in physical capacity between fit individuals and end stage disease adds to complexity of assessment. Independent factors of age, genetics, habitual exercise, nutritional status and musculoskeletal conditions are all known to influence physical capacity in patients with CF (8,9). Maximal exercise testing places additional stress on cardiovascular, respiratory and peripheral systems providing more information around multiple influences on disease progression including degree of limitation in these major systems (10,11) and is useful for assessment of exercise desaturation, more common (but not always present) in advanced lung disease (5,12). With prediction of exercise performance and functional capacity from PFTs unreliable and the understanding that health status correlates better with exercise tolerance there has been an increase in maximal exercise testing for patient management (13). Many international centers now regard exercise testing as highly important with many assessing maximal exercise capacity annually to monitor disease progression, identify physical status and drive changes in medical, physiotherapy or nutritional management (14,15). The main vision is to develop a standardized incremental step test protocol suitable for adults with Cystic Fibrosis (CF), all ages, levels of fitness and disease state that is in line with current exercise testing recommendations (15). To develop a more useful field test to assess exercise tolerance and a more "user friendly" test than the currently available laboratory exercise test to allow for early detection of decline in physical function in the day-to-day clinical setting. To date no studies have been published in adults with CF where an incremental exercise step test has been investigated to assess exercise tolerance or determine maximum oxygen uptake (VO2max).

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