Relationship between the difference of slow and forced vital capacity and physical activity in daily life in patients with Chronic Obstructive Pulmonary Disease

ABSTRACT The aim of this study was to correlate the difference of vital capacity (VC) and forced vital capacity (FVC) (VC-FVC) with physical activity in daily life (PADL) in patients with chronic obstructive pulmonary disease (COPD); and investigate the differences in PADL in individuals with VC smaller or greater than FVC. Twenty-eight patients with COPD (18 men, 67±8 years; FEV1: 40±13% predicted) had their lung function assessed by spirometry and were divided into two groups: VC>FVC (n=17) and VC≤CVF (n=11). Furthermore, they had their PADL evaluated by a validated activity monitor which measures, among other variables, time spent/day walking, standing, sitting and lying. There were no correlations between VC-FVC and the variables of PADL in the general group. In the group VC>FVC there was statistically significant correlation between VC-FVC and the time spent/day standing (r=−0.56) and sitting (r=0.75). In the group VC≤CVF , VC-FVC was significantly correlated with time spent/day standing (r=0.57) and lying (r=−0.62). When comparing the groups, there was no statistically significant difference for any variable of PADL (p>0.05 for all). In conclusion, in patients with VC greater than FVC there was high correlation with time spent/day sitting, but not with time spent/day walking. Therefore, individuals with greater airflow obstruction according to the VC-FVC difference tend to spend more time in activities of lower energy expenditure, which do not involve walking.