Mecânica respiratória na doença pulmonar obstrutiva crônica: análise da complexidade e impedância ao longo do ciclo ventilatório

Abstract

Recently there has been a growing interest in the study of nonlinear dynamics as a methodology for further analysis to characterize the respiratory system. Chronic obstructive pulmonary disease (COPD) introduces pathophysiological changes that culminate in a complex behavior that is "silent" in its initial phases. We observed the need to obtain information that is more detailed by using the Forced Oscillations Technique (FOT) for better understanding of factors that contribute to the illness. The present thesis aimed to evaluate the contribution of the FOT in assessing changes in respiratory mechanics within the ventilatory cycle in patients with COPD, including an evaluation of the complexity of the respiratory system. A total of 207 patients were evaluated in this study. In the first phase 114 subjects were included, 20 healthy volunteers (CG) and 94 with COPD. These latter, we obtained a total of 5 groups: normal to the spirometric exam (Stage 0) group with 20 subjects, the mild group (Stage I) with n=14, the moderate group (Stage II) of n=20, the severe group (Stage III) n=20 and very severe group (Stage IV) consisting of 20 patients. The parameters analyzed were average respiratory system impedance (Zm), inspiratory and expiratory impedance (Zi and Ze, respectively), the impedance at the beginning of inspiration and expiration (Zii and Zie), the peak-to-peak impedance (Zpp) and the mean change in impedance (ΔZrs). In the second phase, the complexity of the respiratory system was analyzed by the variability of airflow and Zrs (SDV and SDZrs, respectively), the sample entropy of airflow and Zrs (EnAmV' and EnAmZrs, respectively) and the entropy density of the recurrence period of airflow and ZRS (RPDEV' and RPDEZrs, respectively). At this stage, after were analyzed in 88 subjects related to the complexity of airflow analysis. A total of 72 COPD patients was divided into the following groups: G0 (n = 13), GI (n = 11), GII (n = 18), GIII (n = 16), GIV (n = 14). The GC was composed of 16 individuals. The analysis related to the complexity of Zrs involved a total of 97 individuals. A total of 74 COPD patients were divided into following groups: G0 (n = 17), GI (n = 10), GII (n = 16), GIII (n = 16), GIV (n = 15). The GC was composed of 23 healthy individuals. Respiratory impedance was higher in COPD patients compared to the CG, an increase with the progression of bronchial obstruction: Zm (p<0.0001), Zi (p<0.0001), Ze (p<0.0001), Zii (p<0.0001), Zie (p<0.0001), Zpp (p<0.0001) and ΔZrs (p<0.01). It was observed a significant increase in SDV' (p< 0.002) and SDZrs (p<0.0001) with bronchial obstruction. Moreover, the complexity of respiratory decreased, as observed in SampEnV' (p< 0.002) and RPDEZrs (p<0.0001). The SampZrs and RPDEV' parameters showed no statistically significant differences between groups. Most parameters of the Zrs had adequate values (AUC>0.8). RPDEZrs values and SDZrs showed AUC>0.80 in most of the studied groups. We concluded that individuals with COPD at different levels of bronchial obstruction have higher impedance when compared to normal individuals. Higher impedances in the expiratory phase were observed in subjects with COPD, especially in individuals with severe and very severe obstruction component. COPD introduces a loss of complexity.