EVALUATION OF A MOVEMENT DETECTOR TO MEASURE DAILY ACTIVITY IN PATIENTS WITH CHRONIC LUNG-DISEASE

This study was designed to evaluate the performance of movement detect ors (pedometers) in measuring daily activity of patients with chronic lung disease, Three groups of subjects were studied: group 1: 25 patie nts with stable nonhypercapnic chronic obstructive pulmonary-disease ( COPD) (forced expiratory) volume in one second (FEV1) = 47+/-9% predic ted) studied twice, one month apart; group 2: 25 patients with chronic respiratory failure studied before and three months after nasal noctu rnal mechanical ventilation; and group 3: 25 normal healthy subjects s tudied once, The median level of activity in the healthy subjects (gro up 3) was three times greater than in either group of patients (groups I and 2). Activity levels were not correlated with age, sex or employ ment status, The repeatability of the activity counts in the nonhyperc apnic COPD patients was high (intraclass correlation coefficient=0.94) and in these patients activity correlated significantly with FEV1 (r= 0.54, p=0.006). In the respiratory failure patients, daytime arterial carbon dioxide pressure (Pa,CO2) improved following nasal nocturnal me chanical ventilation (NMV) (pre NMV: 85+/-1.2 kPa; post NMV: 6.2+/-0.5 kPa), health status improved (p<0.004) and daily movement count doubl ed (p<0.0001). This increase correlated with change in Pa,CO2 (r-0.53, p=0.006), but not with improved health status. We conclude that motio n detectors may provide repeatable measures of daily activity that are related to physiological impairment and improvement following treatme nt, Activity counts appear to be complementer to estimates of exercise limitation obtained using health questionnaires.