Expiratory flow limitation relates to symptoms during COPD exacerbations requiring hospital admission.

Background: Expiratory flow limitation (EFL) is seen in some patients presenting with a COPD exacerbation; however, it is unclear how EFL relates to the clinical features of the exacerbation. We hypothesized that EFL when present contributes to symptoms and duration of recovery during a COPD exacerbation. Our aim was to compare changes in EFL with symptoms in subjects with and without flow-limited breathing admitted for a COPD exacerbation.

Changes in oscillatory impedance and nitrogen washout with combination fluticasone/salmeterol therapy in COPD.

Introduction: Combination inhaled corticosteroid/long-acting bronchodilator (ICS/LABA) therapy reduces the exacerbation rate and improves spirometry and quality of life in COPD. We hypothesized that ICS/LABA therapy also improves small airway function measured by FOT.

Methods: 14 subjects with COPD were commenced on combination fluticasone propionate/salmeterol therapy for 3 months.

The feasibility of home monitoring of impedance with the forced oscillation technique in chronic obstructive pulmonary disease subjects.

Respiratory system resistance (Rrs) and reactance (Xrs) measured by forced oscillation technique (FOT) can be potentially used for home monitoring in COPD. Our aims were to determine the technical acceptability, adherence and variability of unsupervised, home FOT measurements over ten consecutive days. Supervised spirometry and FOT measurements were made on ten clinically stable COPD subjects at their homes at the study initiation.

Day-to-day variability of oscillatory impedance and spirometry in asthma and COPD.

Variability in airway function may be a marker of disease activity in COPD and asthma. The aim was to determine the effects of repeatability and airway obstruction on day-to-day variability in respiratory system resistance (Rrs) and reactance (Xrs) measured by forced oscillation technique (FOT). Three groups of 10 subjects; normals, stable asthmatic and stable COPD subjects underwent daily FOT recordings for 7 days.

The relationship between airflow obstruction, emphysema extent, and small airways function in COPD.

Background: The severities of COPD (FEV(1) % predicted) and airflow obstruction (FEV(1)/FVC) are considered to be due to both emphysema and small airways disease. To our knowledge, this has not been previously confirmed by combined measurements of emphysema and of small airway function. We hypothesized that small airways disease and emphysema extent contribute independently to the severity of both COPD and airflow obstruction.

Improved respiratory system conductance following bronchodilator predicts reduced exertional dyspnoea.

Background: In COPD, improvements in lung mechanics following bronchodilator, measured using the forced oscillation technique (FOT), are more sensitive than spirometry at detecting improvement in lung function following bronchodilator. The relationship between these improvements in lung mechanics and improvements in functional outcomes, such as exertional dyspnoea, following bronchodilator, in COPD is unknown.

Methods: 17 COPD subjects were recruited into a double blind placebo controlled randomised cross over study.

Avoiding deep inspirations increases the maximal response to methacholine without altering sensitivity in non-asthmatics.

Airway hyperresponsiveness is characterised by a leftward shift of the dose-response curve (DRC) and an increase in the maximal response. Deep inspiration (DI) avoidance increases responsiveness in non-asthmatic, but not asthmatic, subjects. The aim was to determine the effect of DI avoidance on the sensitivity and maximal response of the FEV(1) DRC to methacholine.

Short-term variability of airway caliber-a marker of asthma?

Variability in airway caliber is a characteristic feature of asthma. Previous studies reported that the variability in respiratory system impedance (Zrs), measured by the forced oscillation technique during several minutes of tidal breathing, is increased in asthma and may be a marker of inherent instability of the airways. The aims of this study were to determine if short-term variability in impedance correlates with peak expiratory flow (PEF) variability or airway hyperresponsiveness (AHR).

A comparison of airway and serum matrix metalloproteinase-9 activity among normal subjects, asthmatic patients, and patients with asthmatic mucus hypersecretion.

Background: The rate of decline in lung function is increased in asthmatic patients, particularly in those with coexisting asthmatic mucus hypersecretion (AMH), in whom inflammation and the activity of matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinase (TIMP)-1 in serum and BAL fluid (BALF) may be increased.

Methods: Seven nonasthmatic subjects and 22 asthmatic subjects completed a questionnaire, and underwent lung function testing and bronchoscopy, during which AMH was diagnosed by the presence of mucus plugging. Subjects were classified as follows: mild/moderate asthma; severe asthma; and AMH.