Impulse oscillometry in the assessment of patients with idiopathic arterial hypertension: a pilot study.

Studies suggest peripheral airway involvement in pulmonary arterial hypertension (PAH). Impulse oscillometry (IOS) is a noninvasive and sensitive technique for assessing the small airways. The IOS evaluates the impedance of the respiratory system – resistance (R) and reactance (X) – to an impulse of sound waves sent to the lungs at a specific frequency range (5-30 Hz). Representative variables for resistance: R5, R20, and for reactance: AX (reactance area) and Fres (resonance frequency). Objective: to evaluate R and X in patients with PAH; to investigate whether there is a correlation between IOS and spirometry. Methods: exploratory cross-sectional study; 13 patients with idiopathic PAH (IPAH) and 11 healthy individuals matched for sex and age underwent IOS and spirometry. Results: IPAH: 92.3% women, mean age = 44.85 years, non-smokers, no history of asthma. Spirometry: IPAH showed lower values in FVC and FEV1 (p < 0.001) and in FEV1/FVC ratio (p < 0.05). IOS: IPAH showed lower tidal volume (TV) and higher AX than healthy individuals (p < 0.05), results indicating an increase in reactance in the peripheral airways without a change in resistance. The correlation coefficient (Spearman) showed correlations only in the group PAH: reactance variables (X5, AX and Fres) correlated with FVC (p = 0.036, p = 0.001 and p = 0.027, respectively). Fres (p = 0.012) and AX (p = 0.006) correlated with FEV1, which in turn correlated with R5 and R20 (p < 0.001 and p = 0.019, respectively). Conclusions: PAH patients showed differences in IOS compared to healthy individuals, and the results correlated with spirometry.