BackgroundMultiple breath washout (MBW) became a valuable research tool assessing ventilation heterogeneity. However, routine clinical application still faces several challenges. Deriving MBW parameters from three technically acceptable measurements according to current recommendations prolongs test times. We therefore aimed to evaluate reporting only duplicate measurements in healthy adults and pulmonary disease.MethodsOne hundred and fifty-three subjects prospectively underwent conventional lung function testing and closed-circuit SF6-MBW. Three technically acceptable MBW-measurements were obtained in 103 subjects.ResultsLung clearance index (LCI) differed significantly among 19 controls (7.4 ± 0.8), 19 patients with sarcoidosis (8.1 ± 1.2), 32 with bronchial asthma (9.2 ± 1.9) and 33 with COPD (10.8 ± 2.2, p < 0.001). Within-test repeatability was high (coefficient of variation between 2.5% in controls and 3.6% in COPD) and remained unchanged when only including the first two measurements. Likewise, LCI remained stable with mean absolute changes ranging from 0.9 ± 0.8% in controls to 1.5 ± 0.9% in COPD (p = 0.1). Mean test time reduction differed significantly between groups reaching 200 s in COPD (p = 0.01).ConclusionsDuplicate SF6-MBW-measurements are sufficient in adult patients with pulmonary disease and healthy controls. LCI values and intra-test repeatability are not affected reducing total test time statistically significant. Our findings have the potential to further facilitate application of MBW in research and clinical routine.Trial registration
NCT03176745, June 2, 2017 retrospectively registered.Electronic supplementary materialThe online version of this article (10.1186/s12890-017-0543-y) contains supplementary material, which is available to authorized users.
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.
Ventilation heterogeneity is frequent in bronchial asthma and can be assessed using multiple breath wash-out testing (MBW). Most data is available in paediatric patients and using nitrogen as a tracer gas. We aimed to evaluate sulphur hexafluoride (SF 6) MBW in adult asthmatics. Spirometry, wholebody plethysmography, impulse oscillometry and SF 6-MBW were prospectively performed. MBW parameters reflecting global (lung clearance index, LCI), acinar (S acin) and conductive (S cond) ventilation heterogeneity were derived from three consecutive wash-outs. LCI was calculated for the traditional 2.5% and an earlier 5% stopping point that has the potential to reduce wash-out times. 91 asthmatics (66%) and 47 non-asthmatic controls (34%) were included in final analysis. LCI 2.5 and Lci 5 were higher in asthmatics (p < 0.001). Likewise, S acin and S cond were elevated (p < 0.001 and p < 0.01). Coefficient of variation was 3.4% for LCI 2.5 and 3.5% for LCI 5 in asthmatics. Forty-one asthmatic patients had normal spirometry. ROC analysis revealed an AUC of 0.906 for the differentiation from non-asthmatic controls exceeding diagnostic performance of individual and conventional parameters (AUC = 0.819, p < 0.05). Sf 6-MBW is feasible and reproducible in adult asthmatics. Ventilation heterogeneity is increased as compared to non-asthmatic controls persisting in asthmatic patients with normal spirometry. Diagnostic performance is not affected using an earlier LCI stopping point while reducing wash-out duration considerably. Disease control is the primary goal of asthma therapy being linked to absence of symptoms and exacerbations 1. Regrettably, up to half of the patients are poorly controlled 2,3. Despite therapeutic advances, numbers remained fairly unaltered during the last decade. The clinical and pathophysiological explanations associated with poor disease control are heterogenous. In general, more severe disease is related to more frequent exacerbations, health care contacts 3 and symptoms 4. Lung function is also impaired in severe disease indicated by a lower forced expiratory volume in one second (FEV 1) and lower forced vital capacity (FVC) 3. Both parameters represent rather central sites of obstruction. However, involvement of peripheral airways is common in the majority of asthmatic patients 5. This holds true across the whole spectrum of severity 6 and may be a consequence of several influencing factors. These include inflammation, wall thickening, smooth muscle hypertrophy, and mucus 7-10. However, changes in the lung periphery are still often missed by commonly used techniques such as spirometry. Impulse oscillometry (IOS) is an inexpensive non-invasive technique to measure airway resistance. It was shown to identify small airway obstruction 11 , the related characteristics of disease control 12,13 and response to
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