Técnica de pressão expiratória negativa em indivíduos portadores de asma: mecânica ventilatória e efeito do broncodilatador

Abstract

Asthma is an obstructive disease of the lower airways. Pulmonary function tests that do not require effort are needed for diagnostic accuracy. The negative expiratory pressure technique (NEP) has been used to assess the expiratory flow limitation (EFL) in obstructive diseases. However, there are few studies describing the use of NEP in patients with asthma. In this context, the aim of this study was to evaluate new respiratory function parameters by NEP in patients with asthma. This was an analytical, observational, and cross-sectional controlled study involving two categorized groups according to the Asthma Control Scoring System (ACSS): a group of patients with controlled asthma (CA) and another group of patients with uncontrolled asthma (UA), as well a control group (CG). The modified Borg dyspnea scale and funcional tests of NEP, plethysmography and spirometry were performed in these three groups on the exposed sequence and in two stages: before and after bronchodilator (Bd) use. It was observed increased EFL% and reduced expiratory flow variations for those with more severe obstruction (UA group). The EFL% and Δ25-75% reflected the pathophysiological changes occurring in medium caliber bronchus in asthma, and moderately correlated with forced expiratory volume in first second (FEV1). There was no significant variation in NEP parameters after using the Bd in seated patients. The ACSS showed good to excellent correlation with spirometry, moderate correlation with body plethysmography, and reasonable correlation with NEP. Clinical data obtained from the modified Borg dyspnea scale were reasonably correlated with lung function tests. FEV1 was the best lung parameter that correlated with the modified Borg dyspnea scale (r = -0.46, p <0.01). The NEP was able to detect changes in respiratory function of patients with asthma correlating with traditional pulmonary function tests and clinical instruments used in this study (ACSS and modified Borg dyspnea scale), being considered a promising technique.