Complexity of the Airflow in COPD
Complexity of the Airflow in COPD
Recently, there has been a growing interest in the study of nonlinear dynamics as a
 methodology for complementary analysis to characterize the respiratory pattern. These methods
 are well established in studies of heart rate. The analyzes evaluate complex signals,
 including large-scale fractal correlations and distributions in time series, and can provide
 relevant clinical information.

 Measures such as approximate entropy and sample entropy have shown great potential in the
 evaluation of the complexity of the respiratory system, providing information relevant to the
 understanding of physiological and pathophysiological processes. These measures are based on
 the concept of non-linearity in the presence of a high number of interconnections, resulting
 in the complex behavior exhibited by physiological systems.

 The approximate entropy (ApEn) is related to the amount of clutter, complexity or
 unpredictability of a data series over time. In a complementary way, the sample entropy
 (SampEn), is a far more elaborate than the ApEn, to reduce possible biased estimates due to
 self-similarity.

 A study conducted by our group in asthma patients with different levels of bronchial
 obstruction demonstrated a significant reduction in airflow approximate entropy (ApEnV´) in
 asthmatic subjects. Investigators believe that in COPD, similar to that which occurs in
 asthma disorders that are associated with complex changes in the pathophysiology triggering
 breath control, possibly resulting in changes in air flow (V´).

 Considering the development "silent" changes of mechanical ventilation in COPD patients and
 its clinical relevance, as well as the difficulty of identifying such changes through
 conventional methods, we observed the need to obtain more detailed information, including the
 complexity of the system breathing for better understanding of factors that contribute to the
 illness.

 In this context, the objectives of this study were: (1) analyze the influence of airway
 obstruction in the complexity of the patterns of airflow in patients with COPD, (2) evaluate
 the diagnostic power of the test in identifying the changes caused by COPD.
Inclusion Criteria:

 -  volunteers with COPD for Patients Group;

 -  volunteers without any respiratory disease for the control group.

 Exclusion Criteria:

 -  individuals with history of tuberculosis or other lung disease,

 -  heart disease in general and

 -  disability in the exams.