Small Airway Disease in Pulmonary Hypertension-Additional Diagnostic Value of Multiple Breath Washout and Impulse Oscillometry.

Frederik Trinkmann,Joshua Gawlitza,Christina Dösch,Ksenija Stach,Joachim Saur,Michele Schroeter,Julia Schäfer,Monique Künstler,Martin Borggrefe,Ibrahim Akin,Julia Michels

doi:10.3390/jcm7120532

Abstract

Airways obstruction is frequent in patients with pulmonary hypertension (PH). Small airway disease (SAD) was identified as a major contributor to resistance and symptoms. However, it is easily missed using current diagnostic approaches. We aimed to evaluate more elaborate diagnostic tests such as impulse oscillometry (IOS) and SF6-multiple-breath-washout (MBW) for the assessment of SAD in PH. Twenty-five PH patients undergoing body-plethysmography, IOS and MBW testing were prospectively included and equally matched to pulmonary healthy and non-healthy controls. Lung clearance index (LCI) and acinar ventilation heterogeneity (Sacin) differed significantly between PH, healthy and non-healthy controls. Likewise, differences were found for all IOS parameters between PH and healthy, but not non-healthy controls. Transfer factor corrected for ventilated alveolar volume (TLCO/VA), frequency dependency of resistance (D5-20), resonance frequency (Fres) and Sacin allowed complete differentiation between PH and healthy controls (AUC (area under the curve) = 1.0). Likewise, PH patients were separated from non-healthy controls (AUC 0.762) by D5-20, LCI and conductive ventilation heterogeneity (Scond). Maximal expiratory flow (MEF) values were not associated with additional diagnostic values. MBW and IOS are feasible in PH patients both providing additional information. This can be used to discriminate PH from healthy and non-healthy controls. Therefore, further research targeting SAD in PH and evaluation of therapeutic implications is justified.

Highlights

Pulmonary hypertension (PH) is most frequently associated with left heart (Nizza Group 2) or pulmonary disease (Group 3)
Reversibility testing was performed in 12 patients (48%) with PH and 9 non-healthy controls (36%) with details given in Table S1 (Supplementary)
FEV1: Forced expiratory volume in one second, vital capacity (VC): Vital capacity, TLC: Total lung capacity, RV: Residual volume, FRCpleth/: Functional residual capacity by body plethysmography, FRCMBW: Functional residual capacity by multiple breath washout, TLCO/VA: Transfer factor corrected for ventilated alveolar volume, D5-20: Frequency dependence of resistance, Fres: Resonance frequency, AX: Area under reactance curve, LCI: Lung clearance index, Sacin: Acinar ventilation heterogeneity, Sacin: Conductive ventilation heterogeneity, %pred: percent of predicted. # Student’s t-test as compared to the PH group. * Statistically significant p < 0.05

Summary

Introduction

Pulmonary hypertension (PH) is most frequently associated with left heart (Nizza Group 2) or pulmonary disease (Group 3). Restrictive ventilation disorders are frequently described in Group 2 PH [8], obstruction patterns are common in patients with left heart failure [9] These airway abnormalities may often be viewed as mild at rest, they were shown to induce dynamic hyperinflation [10]. Lung clearance index (LCI) is already elevated even in the absence of spirometric obstruction [16] Both techniques may provide additional information when assessing lung function impairment in patients with PH. It is still unknown whether bronchodilator therapy can improve symptoms in this setting [13,17]. The aim of the present study, was to prospectively evaluate novel lung function tests for assessment of small airway disease in patients with PH

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Conclusion