# Impulse oscillometry in patients with pulmonary arterial hypertension: an exploratory study

## TL;DR

Impulse Oscillometry (IOS) reveals increased lung resistance and reactance in patients with pulmonary arterial hypertension, which correlates with standard lung function tests.

## Contribution

This study is the first to explore IOS in idiopathic pulmonary arterial hypertension and demonstrate its correlation with spirometric variables.

## Key findings

- Patients with PAH showed increased resistance and reactance compared to healthy individuals.
- IOS variables correlated moderately with spirometric measures like FVC and FEV1.
- Over half of PAH patients had elevated R5-R20 values, indicating airway obstruction.

## Abstract

•Impulse Oscillometry (IOS) can be used to analyze lung resistance and reactance in patients with PAH.•Patients with PAH show increased resistance and pulmonary reactance compared to healthy individuals.•The IOS findings showed a good correlation with the spirometric variables.

Impulse Oscillometry (IOS) can be used to analyze lung resistance and reactance in patients with PAH.

Patients with PAH show increased resistance and pulmonary reactance compared to healthy individuals.

The IOS findings showed a good correlation with the spirometric variables.

Studies suggest peripheral airway abnormalities in Pulmonary Arterial Hypertension (PAH). Impulse Oscillometry (IOS) is a noninvasive and sensitive technique for assessing the small airways. It evaluates the impedance of the respiratory system ‒ Resistance (R) and reactance (X) ‒ to a pulse of sound waves sent to the lungs, in a range of frequencies (5‒20 Hz).

Resistance variables: R5, R20, R5-R20 and reactance variables: AX (reactance area) and Fres (resonance frequency). The aim is to evaluate R and X in patients with idiopathic PAH (IPAH) and to investigate whether there is a correlation between IOS and spirometry.

Thirteen IPAH patients and 11 healthy subjects matched for sex and age underwent IOS and spirometry. IPAH patients had lower FVC and FEV1 values (p < 0.001), VEF1/CVF (p = 0.049) and FEF 25-75 (p = 0.006) than healthy patients. At IOS, IPAH patients showed lower tidal volumes and higher AX (p < 0.05) compared to healthy individuals, and 53.8 of patients had R5-R20 values ≥ 0.07 kPa/L/s. Correlation analysis: X5, AX, R5-R20 and Fres showed moderate correlation with FVC (p = 0.036 r = 0.585, p = 0.001 r = -0.687, p = 0.005 r = -0.726 and p = 0.027 r = -0.610); Fres (p = 0.012 r = -0.669) and AX (p = 0.006 r = -0.711) correlated with FEV1; [R5 and R20, (R5-R20)] also correlated with FEV1 (p < 0.001 r = -0.573, p = 0.020 r = -0.634 and p = 0.010 r = -0.683, respectively) in the IPAH group. There were also moderate correlations of FEF 25–75 % with Z5 (p = 0.041), R5 (p = 0.018), Fres (p = 0.043) and AX (p = 0.023).

Patients showed changes suggestive of increased resistance and reactance in the IOS compared to healthy individuals, and the IOS findings showed a good correlation with spirometry variables.