Técnica de oscilações forçadas na análise da resposta broncodilatadora em voluntários sadios e indivíduos portadores de asma brônquica com resposta positiva Using the forced oscillation technique to evaluate bronchodilator response in healthy volunteers and in asthma patients presenting a verified positive response

OBJETIVO: Analisar, através da técnica de oscilações forçadas, pacientes asmáticos com resposta broncodilatadora positiva pelo laudo espirométrico e comparar esses resultados com os obtidos em indivíduos sadios. MÉTODOS: Foram analisados 53 indivíduos não tabagistas, sendo 24 sadios sem história de doença pulmonar e 29 asmáticos com resposta broncodilatadora positiva segundo o laudo espirométrico. Todos foram submetidos à técnica de oscilações forçadas e a espirometria antes e após vinte minutos da administração de salbutamol spray (300 g). Os parâmetros derivados da técnica de oscilações forçadas foram: resistência total, reatância total, resistência extrapolada para o eixo y, coeficiente angular da reta de resistência e complacência dinâmica. Na espirometria, os parâmetros utilizados foram o volume expiratório forçado no primeiro segundo e a capacidade vital forçada. RESULTADOS: No grupo controle, a utilização do broncodilatador produziu alteração significativa na resistência extrapolada para o eixo y (p < 0,001), embora o coeficiente angular da reta de resistência e a complacência dinâmica não tenham apresentado diferenças estatisticamente significativas. A análise dos asmáticos mostrou que a diferença entre as medidas pré e pós-broncodilatador foi significativa, tanto para os parâmetros espirométricos quanto para os de técnica de oscilações forçadas. Valores de p < 0,001 foram obtidos em todas as comparações relacionadas aos asmáticos. CONCLUSÃO: As alterações nos parâmetros obtidos a partir da técnica de oscilações forçadas mostraram-se em estreita concordância com a fisiopatologia da resposta broncodilatadora em asmáticos, indicando que a técnica de oscilações forçadas pode ser útil como análise complementar à espirometria nesses pacientes.<br>OBJECTIVE: To use the forced oscillation technique to evaluate asthma patients presenting positive bronchodilator responses (confirmed through spirometry) and compare the results with those obtained in healthy individuals. METHODS: The study sample consisted of 53 non-smoking volunteers: 24 healthy subjects with no history of pulmonary disease and 29 asthmatics presenting positive bronchodilator response, as determined through analysis of spirometry findings. All of the subjects were submitted to forced oscillation technique and spirometry immediately before and 20 minutes after the administration of salbutamol spray (300 g). The parameters derived from the forced oscillation technique were total respiratory resistance, total respiratory reactance, resistance extrapolated to the y axis, the slope of resistance, and dynamic compliance. The parameters measured in the spirometry evaluation tests were forced expiratory volume in one second and forced vital capacity. RESULTS: In the control group, bronchodilator use produced a significant alteration in the resistance extrapolated to the y axis (p < 0.001), although no significant differences were observed in the slope of resistance or in dynamic compliance. Analysis of the asthma patients revealed significant differences between the prebronchodilator and postbronchodilator values for all spirometry and forced oscillation technique parameters. Values of p < 0.001 were obtained for all comparisons between the two groups. CONCLUSION: The modifications provoked by use of the forced oscillation technique were in direct concordance with the pathophysiology of the bronchodilator response in asthma patients, indicating that the forced oscillation technique could be useful as a complement to spirometry in these patients

Advances in the diagnosis of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) describes the post exercise phenomenon of acute airway narrowing in association with physical activity. A high prevalence of EIB is reported in both athletic and recreationally active populations. Without treatment, EIB has the potential to impact upon both health and performance. It is now acknowledged that clinical assessment alone is insufficient as a sole means of diagnosing airway dysfunction due to the poor predictive value of symptoms. Furthermore, a broad differential diagnosis has been established for EIB, prompting the requirement of objective evidence of airway narrowing to secure an accurate diagnosis. This article provides an appraisal of recent advances in available methodologies, with the principle aim of optimising diagnostic assessment, treatment and overall clinical care