Técnica de oscilações forçadas monofrequência na análise em tempo real das alterações mecânicas ao longo do ciclo respiratório de asmáticos com diferentes níveis de obstrução ao fluxo aéreo

• Autor(a) principal: Cavalcanti, Juliana Veiga
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/12587
• topic: Respiratory mechanics; Asthma; Forced oscillations; Respiratory impedance; Diagnostic; Entropy; Complexity; Mecânica respiratória; Asma; Oscilações Forçadas; Impedância respiratória; Diagnóstico; Entropia; Complexidade; CNPQ::CIENCIAS BIOLOGICAS::FISIOLOGIA::FISIOLOGIA DE ORGAOS E SISTEMAS::FISIOLOGIA DA RESPIRACAO

The analysis of respiratory mechanics in real time by Monofrequency FOT is of great interest in clinical and diagnosis studies of respiratory diseases. However, the use of this technique for the analysis of patients with asthma is still limited. The present study evaluates the contribution of the Monofrequency FOT in the analysis of changes in respiratory mechanics during the breathing cycle and the dynamics of the respiratory system of asthmatics. In the first phase of the study, 14 healthy volunteers (CG) and 70 asthmatics were included. Among them, 13 patients with asthma had normal spirometry (NE), and the others showed mild obstruction (n=26), moderate (n = 18) and severe (n=13). The parameters analyzed through FOT were the total impedance of the respiratory system (Zt), the inspiratory and expiratory impedance (Zi and Ze) and the impedance at the beginning of inspiration and expiration (Zii and Zie). The impedance peak-to-peak (Zii - Zie) and the mean of impedance (Zi - Ze) were also evaluated. In the second phase, the respiratory system dynamics was analyzed through the impedance variability, reflected by the standard deviation of Zrs (sdZrs), and the standard deviation of the Zrs logarithm (sdlnZrs), and an impedance complexity was analyzed through the approximated entropy of the Zrs (ApEnZ). 62 patients with asthma were analyzed, divided into NE (n=12), mild (n=20), moderate (n=18) and severe (n=12). The CG was composed by 12 volunteers. Tests of differences between means, correlations between the FOT parameters, spirometry, and ROC curves, were used to evaluate the potential of Monofrequency FOT in the detection of asthma mechanical changes in real-time. The respiratory impedance was higher in asthmatics than in CG, being progressively bigger among asthmatics according to obstruction degree: Zt (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<0.0001). The dynamics of the respiratory system suffered significant differences in asthmatics. There was a significant increase in sdZrs with the bronchial obstruction degree in asthma (p<0.0001), while the complexity of the system decreased (ApEnZ, p<0.002). Excellent correlations occurred between FEV1/FVC and Zt (r=-0.76), Ze (r=-0.77) and Zie (r=-0.78), while reasonable correlations were found between spirometric parameters with sdZrs and ApEnZ. The best parameters to be used in asthma diagnosis were Zt, Zi, Ze, Zii Zie with adequate AUC to identify mild obstruction and high accuracy in identifying moderate and severe obstructions. The sdZrs was adequated to identify moderate and severe obstruction. These results are in close agreement with the pathophysiologic basis of asthma. The Monofrequency FOT allows a noninvasive analysis of the asthmatics respiratory system in the different phases. The respiratory impedance, especially during inspiration, reflects on the mechanical changes in asthma. The respiratory system dynamics is altered in asthma, with greater variability and less complexity of the respiratory impedance signal, characterizing a system with less adaptability to conditions of greater metabolic demand on the daily life. These results confirm the high potential of clinical and scientific use of this methodology to evaluate patients with asthma.