Postural balance evaluation in patients with chronic obstructive pulmonary disease

Background: The risk of falling in patients with chronic obstructive pulmonary disease (COPD) is higher than healthy people, imposing a great financial burden on patients due to clinical diagnosis and treatment. This study aimed to compare static balance between two groups of healthy people and COPD patients, based on cognitive tasks and vision tests, using linear and non-linear analyses. Materials and Methods: A total of 15 patients with COPD and 14 age-and gender-matched healthy individuals were recruited in this study. Variations in the center of pressure were recorded in both medial-lateral (ML) and anterior-posterior (AP) directions by implementing visual feedback and cognitive tasks, with the subject standing on a force plate. Data related to the center of pressure were analyzed in the AP and ML directions by linear methods (i.e., standard deviation of displacement, standard deviation of maximum velocity, average velocity, and phase plane). Also, the nonlinear method (Lyapunov exponents) was used in both directions. Results: The cognitive tasks improved the center of pressure variables in both groups. In association with the vision tests, only lack of vision had a significant effect on the patients. The results of the linear analysis in the ML direction were significantly higher in the COPD group as compared to the healthy group; however, the results were not significant in the AP direction. Also, the nonlinear analysis showed significant differences between the groups. Conclusion: Use of both linear and non-linear analyses is necessary for evaluating the balance of patients with breathing difficulties. Balance disorders in COPD patients were mostly in the ML direction; therefore, postural deformities might be one of the reasons for balance problems in the AP direction.