Gerusa Marítimo da Costa

Broncodilatação na DPOC: muito além do VEF1-efeito do salbutamol nas propriedades resistivas e reativas do sistema respiratório

OBJECTIVE Current debates on the bronchodilator response in COPD patients and whether the variation in FEV1 can be considered as an indicator of complete reversibility in such patients motivated us to conduct this study. The objective of the study was to determine the effect of albuterol on the resistive and reactive properties of the respiratory system in COPD patients. METHODS We evaluated 70 patients with COPD, divided into two groups based on spirometry findings: bronchodilator (BD)-negative (n = 39); and BD-positive (n = 31). We used the forced oscillation technique (FOT) to evaluate the following parameters: resistance at the intercept (R0), associated with the total resistance of the respiratory system; mean resistance (Rm), associated with central airway resistance; dynamic compliance (Cdyn); and the slope of resistance (S) and mean reactance (Xm), both of which are associated with the homogeneity of the respiratory system. RESULTS The use of albuterol resulted in significant reductions in (p < 0.00002) and Rm (p < 0.0002). There were also significant increases in S (p < 0.0001), Cdyn (p < 0.0001) R0 and Xm (p < 0.00004).These modifications occurred in both groups, the changes in FOT parameters being greater than those observed for spirometric parameters. CONCLUSIONS The use of albuterol improved the resistive and reactive properties of the respiratory system of the COPD patients under study. These changes occurred regardless of the FEV1-based classification, thereby indicating that the use of this parameter in isolation might not suffice to identify the physiological effects involved.OBJETIVO: Atualmente existem importantes debates na literatura sobre a resposta broncodilatadora em pacientes com DPOC e se a variacao do VEF1 pode ser considerada uma indicacao completa de reversibilidade neste caso particular. O objetivo deste estudo foi investigar o efeito do salbutamol nas propriedades resistivas e elasticas do sistema respiratorio de portadores de DPOC. METODOS: Foram avaliados 70 individuos com DPOC, classificados atraves da espirometria em dois grupos: broncodilatador (BD)-negativo (n = 39); e BD-positivo (n = 31). Utilizou-se a tecnica de oscilacoes forcadas (TOF) para avaliar os seguintes parâmetros: a resistencia no intercepto (R0), associada a resistencia total do sistema respiratorio; a resistencia media (Rm), relacionada a resistencia de vias aereas centrais; e a complacencia dinâmica (Cdyn); assim como o coeficiente angular da resistencia (S) e a reatância media (Xm), relacionados com a homogeneidade do sistema respiratorio. RESULTADOS: O uso do salbutamol resultou em reducoes significativas de R0 (p < 0,00002) e Rm (p < 0,0002). Foram tambem observadas elevacoes significativas em S (p < 0,0001), Cdyn (p < 0,0001) e Xm (p < 0,00004). Estas alteracoes ocorreram tanto nos dois grupos, tendo sido observadas maiores modificacoes nos parâmetros da TOF do que nos parâmetros da espirometria. CONCLUSOES: O uso de salbutamol melhorou o comportamento dos componentes resistivos e reativos do sistema respiratorio dos pacientes com DPOC estudados. Estas mudancas ocorreram independentemente da classificacao do exame empregando o VEF1, o que indica que a utilizacao deste parâmetro isoladamente pode nao ser suficiente para identificar completamente os efeitos fisiologicos envolvidos.

Respiratory Impedance and Response to Salbutamol in Healthy Individuals and Patients with COPD

Background: Recent studies suggested that the bronchodilator response depends on airway obstruction. The forced oscillation technique (FOT) may help improve our understanding of the changes in respiratory mechanics that occur after the application of a bronchodilator. Objectives: We aimed to (1) assess the response to salbutamol and to compare the impedance changes in healthy individuals and COPD patients, (2) investigate the effects of airway obstruction on this response and (3) evaluate the utility of the FOT as a complementary measurement to assess the response to the bronchodilator. Methods: Twenty-five healthy individuals and 82 patients with COPD were assessed with the FOT followed by spirometry before and after the use of salbutamol. Results: The changes exhibited by the COPD subgroups were greater than in the healthy individuals (p < 0.05). Increased obstruction resulted in decreased reductions in mean resistance and increased improvements in mean reactance (p < 0.001). In addition, the bronchodilation reduced the ventilation heterogeneity and the impedance modulus in all COPD stages (p < 0.05). The correlation coefficients for the spirometric and FOT changes were low (0.21-0.38). Conclusions: In the initial phases of COPD (stage I), the effects of bronchodilation are greater than in healthy volunteers. The bronchodilator use improved the oscillatory mechanics in all of the studied groups of COPD patients. These improvements are reduced in more advanced phases of airway obstruction (II, III and IV). The FOT provides information that complements the data supplied by spirometry, contributing to an improvement in the evaluation of the bronchodilator response in COPD.

Efeito do uso de Broncodilatadores nas Propriedades Resistivas e Reativas do Sistema Respiratório de Indivíduos Saudáveis e com Doença Pulmonar Obstrutiva Crônica

In Chronic Obstructive Pulmonary Disease (COPD) the response to inhaled bronchodilators by means of spirometry is controversial. The objective of this study was to determine the effect acute of salbutamol on the resistive and reactive properties of the respiratory system in COPD patients. A total of 38 subjects were analyzed, 10 healthy control e 28 with COPD, We used the forced oscillation technique (FOT) before and after inhalation of 300 ug salbutamol. Impedance data were interpreted using the total respiratory system resistance (R0); the dynamic compliance (Cdyn); and the slope of the resistance (S), both of which are associated with the homogeneity of the respiratory system. All groups show significant differences between the prebronchodilator and postbronchodilator, except of the healthy subjects in FOT parameters. Values of p < 0.001 were obtained for R0 and S in comparisons between all groups. In all groups Δ%R0, Δ%S e Δ%Cdin was inversely related with the classification of the disease. We conclude that the use of salbutamol improved the resistive properties of the respiratory system of COPD patients proportionally to the degree of airway obstruction. The FOT provide parameters that could be helpful in the analysis of bronchodilation in COPD.