Background: Bronchoscopic lung volume reduction (BLVR) improves lung function, exercise capacity, quality of life, and survival in selected individuals with severe emphysema and hyperinflation, but the impact of BLVR on the function of the small airways is largely unknown. Aims and objectives: We hypothesized endobronchial valve (EBV) implantation would lead to improvements in small airways function. Methods: Patients with severe emphysema, hyperinflation, and no collateral ventilation, underwent EBV placement. Clinical phenotyping at baseline and three months was performed: symptom scores (mMRC, SGRQ), exercise capacity (6MWD), radiological assessment, and lung function testing including impulse oscillometry (IOS) and multiple-breath nitrogen washout (MBN2W). Wilcoxon signed-rank tests were calculated (p<0.05). Results: 12 COPD patients (five female) were participants with a baseline median mMRC score 2.5 and SGRQ-total score 50.9, FEV1 28% and RV 225% predicted, and radiological emphysema. Three months post-procedure, with a radiologically verified median volume reduction of 730mls, improvements were observed for IOS reactance (X5Hz; p=0.013 and Xin5Hz-Xex5Hz; p=0.010), and for MBN2W indices of lung clearance index (LCI; p=0.006) and alveolar mixing efficiency (AME; p=0.001). These accompanied significant gains in spirometry, plethysmographic lung volumes, exercise capacity, and SGRQ-activity score. Four patients developed pulmonary infections; none pneumothoraces. Conclusions: BLVR using EBVs led to improvements in IOS and MBN2W measures reflecting reductions of airflow limitation in small airways and ventilation inhomogeneity. These data support the proposed beneficial impact of BLVR on peripheral lung function.
Background: While peak in- and expiratory flow rates offer valuable information for diagnosis and monitoring in respiratory disease, these indices are usually considered too variable to be routinely used for quantification in clinical practice. Objectives: The aim of the study was to obtain reproducible measurements of maximal inspiratory flow rates and to construct reference equations for peak in- and expiratory flows (PIF and PEF). Method: With coaching for maximal effort, 187 healthy Caucasian subjects (20–80 years) performed at least 3 combined forced inspiratory and expiratory manoeuvres, until at least 2 peak inspiratory flow measurements were within 10% of each other. The effect on PIF preceded by a slow expiration instead of a forced expiration and PIF repeatability over 3 different days was also investigated in subgroups. Reference values and limits of normal for PIF, mid-inspiratory flow, and PEF were obtained according to the Lambda-Mu-Sigma statistical method. Results: A valid PIF could be obtained within 3.3 ± 0.6(SD) attempts, resulting in an overall within-test PIF variability of 4.6 ± 3.2(SD)%. A slow instead of a forced expiration prior to forced inspiration resulted in a significant (p < 0.001) but small PIF increase (2.5% on average). Intraclass correlation coefficient for between-day PIF was 0.981 (95% CI: 0.960–0.992). Over the entire age range, inter-subject PIF variability was smaller than in previous reports, and PIF could be predicted based on its determinants gender, age, and height (r2 = 0.53). Conclusions: When adhering to similar criteria for the measurement of effort-dependent portions of inspiratory and expiratory flow-volume curves, performed according to current ATS/ERS standards, it is possible to obtain reproducible PIF and PEF values for use in routine clinical practice.
A new lung model that incorporates intra-acinar diffusion- and convection-dependent inhomogeneities (DCDI) and interregional and intraregional convection-dependent inhomogeneities (CDI) is described. The model is divided into two regions, each containing two subunits. Each of the four subunits in the model consists of a multi-branch-point structure, based on the anatomic data from Haefeli-Bleuer and Weibel (Anat. Record 220: 401-414, 1988). The subunit turnover (TO), i.e., the ratio of subunit tidal to resting volume, and the flow sequences (FS) between the subunits are used as model parameters. The model simulates the normalized alveolar slope (Sn), Fowler and Bohr dead space (VDF and VDB), and alveolar mixing efficiency (AME) as a function of breath number (n) during a multiple-breath N2 washout (MBNW). For the first breath of the MBNW, these indexes are poorly sensitive to the TO distribution or FS between the subunits. However, as the washout proceeds, the n dependence of both Sn and VDB becomes markedly distinct for simulations with different TO and FS. VDF increases only slightly with n during the MBNW for a large range of TO and FS combinations, and AME is independent of FS. Comparison of published experimental observations with model simulations gave a consistent picture of ventilation maldistribution in the human lung. MBNW simulations in conditions of weightlessness, which will be performed shortly in Spacelab, suggest that it will be possible to evaluate quantitatively the intraregional elastic inhomogeneities in the human lung.
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