Bronchodilator Response in COPD and Asthma: Correlation Between Spirometry, IOS Indices, and Dyspnea Relief

January 23, 2026 updated by: Allergi- og Lungeklinikken, Elsinore

A bronchodilator reversibility test is widely used in the diagnosis and management of obstructive lung diseases.

Bronchodilators relieve symptoms in asthma and COPD. Traditionally, their effectiveness has been assessed using spirometric indices, particularly FEV₁. However, changes in FEV₁ often do not correlate well with patients' subjective experience of dyspnoea relief or with changes in small airway function.

Impulse oscillometry (IOS) provides an effort-independent assessment of respiratory mechanics during tidal breathing and is more sensitive to small airway dysfunction than spirometry. Despite this, the clinical utility of IOS in routine COPD and asthma assessment remains underexplored, and its relationship to both spirometric response and symptom relief is not fully established, and the Minimal Clinically Important Difference (MCID) for IOS parameters has not been firmly established. Determining the MCID is essential for interpreting individual patient responses in a clinically meaningful way and for guiding treatment decisions in both research and practice.

Hypothesis & Aims

In patients with either asthma or COPD baseline values and bronchodilator responses are compared. More specifically, this study aims to:

  1. assess baseline correlations: Evaluate the correlation between ΔX5-baseline (EFL expiratory flow limitation=small airway collapse during expiration), RV/TLC-baseline, X5-average at baseline, FEV1-baseline, VAS-dyspnea at baseline, and ACQ-6-baseline.
  2. compare bronchodilator responses across methods: Examine the correlation between bronchodilator-induced changes in FEV₁ and IOS parameters (including both average and delta values) and explore their relationship with short-term changes in dyspnea.
  3. establish clinical relevance: Determine the MCID for key IOS variables using both anchor-based and distribution-based approaches, anchored to perceived changes in lung symptoms.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Introduction and aims: see brief summary.

Method and Patients This is a real-life, cross-sectional analysis of a single-centered, observational study on 60 adult patients with clinical diagnosed asthma and 60 COPD patients, consecutively recruited between February 1, 2026, and June 30, 2027, and followed at least 6 months for diagnostic clarification.

Inclusion Criteria:

Both asthma and COPD patients:

  1. Written informed consent.
  2. FEV1/Forced Vital Capacity (FVC) <0.7 at baseline )
  3. Visual Analog Scale (VAS) dyspnea score ≥10 (0-100, 100 max).

Asthma: Doctor diagnosed asthma 1. less than 10 packyears.

COPD: Doctor diagnosed COPD with FEV1/FVC <0.7 post-bronchodilation

1. Smokers or ex-smokers with ≥10 packyears

Exclusion Criteria:

  • Patients aged less than 18 years old.
  • Not able to perform spirometry or impulse oscillometry.
  • Cognitive disorders and not able to answer Asthma Control Questionnaire (ACQ), VAS dyspnea score, and COPD Assessment Test (CAT) score.
  • Short-acting beta-agonists 6 h, long-acting beta-agonists 2 days, short-acting anti-muscarinic agent 12 h, Long-acting anti-muscarinic agents 2 days.
  • Comorbidities with significant influence on dyspnea eg. bronchiectasis, ILS, mb. Cordis, lung resection, anemia, and active malignant disease
  • BMI ≥40 kg/m2.

It is a real-life study where most patients are followed up within 6 months. The diagnosis - asthma, COPD, or other condition - may change after follow-up (maximum 6 months after the index examination).

Minimal Clinical Important Difference

Anchor-Based Methods:

  1. The receiver operating characteristic (ROC) curve-based method determines the minimum clinically important difference (MCID) by identifying the value that maximizes the Youden Index. This index is calculated as the maximum sum of sensitivity and specificity. Using data from patients who rate themselves "a little better" and patients who rate themselves "no change"
  2. The social comparison approach provides the MCID as the mean of two differences: the difference of mean score between patients who rate themselves as "a little worse" and patients who rate themselves "no change".
  3. Within-patients score change MCID is the mean delta score of patients who rate themselves "a little better".
  4. The methods of 95% limits of upper agreement: MCID is the mean delta score -1.96 standard error of the delta score of the patients who answered "no change"

Distribution-Based Methods:

  1. MCID defined as standard error of measurement (SEM) evaluated on the baseline values from patients who rated themselves "no change".
  2. MCID defined as 0.5 SD of delta score from patients who answered "a little better"
  3. MCID is defined as 1.96 × √2 × SEM, assessed on baseline values from patients who reported "no change", which represents the smallest change in a measurement that can be considered a "real" change, rather than just random measurement error.

Brochodilator test and order of test To avoid or minimize the effect of deep inhalation on IOS, IOS was performed at least 15 minutes after spirometry and body box.

Patients were administered 4 doses of 0.1 mg Ventoline (salbutamol) via pressurized metered-dose inhaler and spacer (Aero Champer). Post-IOS and post-spirometry were performed 15-20 minutes after the bronchodilator inhalation

Study Type

Observational

Enrollment (Estimated)

120

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

referred to Allergy and Lung Clinic Elsinore, Denmark for evaluation of Asthma and COPD (obstructive lung disease)

Description

Inclusion Criteria:

  • Both asthma and COPD patients:

    1. Written informed consent.
    2. FEV1/Forced Vital Capacity (FVC) <0.7 at baseline (7)
    3. Visual Analog Scale (VAS) dyspnea score ≥10 (0-100, 100 max) (25,26).

  • Asthma: Doctor diagnosed asthma

    1. less than 10 packyears.

  • COPD: Doctor diagnosed COPD with FEV1/FVC <0.7 post-bronchodilation 1. Smokers or ex-smokers with ≥10 packyears

Exclusion Criteria:

  • Patients aged less than 18 years old.
  • Not able to perform spirometry or impulse oscillometry.
  • Cognitive disorders and not able to answer Asthma Control Questionnaire (ACQ), VAS dyspnea score, and COPD Assessment Test (CAT) score (25-28).
  • Short-acting beta-agonists 6 h, long-acting beta-agonists 2 days, short-acting anti-muscarinic agent 12 h, Long-acting anti-muscarinic agents 2 days.
  • Comorbidities with significant influence on dyspnea eg. bronchiectasis, ILS, mb. Cordis, lung resection, anemia, and active malignant disease
  • BMI ≥40 kg/m2.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Asthma

FEV1/Forced Vital Capacity (FVC) <0.7 at baseline (7) Visual Analog Scale (VAS) dyspnea score ≥10 (0-100, 100 max) (25,26). Doctor diagnosed asthma Less than 10 packyears.

Exclusion Criteria:

  • Patients aged less than 18 years old.
  • Not able to perform spirometry or impulse oscillometry.
  • Cognitive disorders and not able to answer Asthma Control Questionnaire (ACQ), VAS dyspnea score, and COPD Assessment Test (CAT) score (25-28).
  • Short-acting beta-agonists 6 h, long-acting beta-agonists 2 days, short-acting anti-muscarinic agent 12 h, Long-acting anti-muscarinic agents 2 days.
  • Comorbidities with significant influence on dyspnea eg. bronchiectasis, ILS, mb. Cordis, lung resection, anemia, and active malignant disease
  • BMI ≥40 kg/m2.
Diagnostic test: Bronchodilator
Classic beta-2-reversibility test
COPD

FEV1/Forced Vital Capacity (FVC) <0.7 at baseline (7) Visual Analog Scale (VAS) dyspnea score ≥10 (0-100, 100 max) (25,26).

Doctor diagnosed COPD Smokers or ex-smokers with ≥10 packyears

Exclusion Criteria:

  • Patients aged less than 18 years old.
  • Not able to perform spirometry or impulse oscillometry.
  • Cognitive disorders and not able to answer Asthma Control Questionnaire (ACQ), VAS dyspnea score, and COPD Assessment Test (CAT) score (25-28).
  • Short-acting beta-agonists 6 h, long-acting beta-agonists 2 days, short-acting anti-muscarinic agent 12 h, Long-acting anti-muscarinic agents 2 days.
  • Comorbidities with significant influence on dyspnea eg. bronchiectasis, ILS, mb. Cordis, lung resection, anemia, and active malignant disease
  • BMI ≥40 kg/m2.
Diagnostic test: Bronchodilator
Classic beta-2-reversibility test

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
FEV1
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Forced expiratory volumen in one second, L and % predicted
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
X5
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Reactance at 5 Hz; kPa/L/s
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Dyspnoea
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Visual analog scale (0-100); 0 means no dyspnoea, and 100 means maximum dyspnoea
Before and 20 minuttes after inhaled Salbutamol 0.4 mg

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
FEV1/FVC-ratio
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
FEV1/forced expiratory capacity (FVC)
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
R5
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Resistance at 5 Hz, kPa/L/s and % predicted
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
R5-R20
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Resistance in small airways, kPa/L/s
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Fres
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Resonant frequency (stiffness), Hz
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
AX
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Area of reactance, kPa/L
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Delta-X5
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Inspiratory - expiratory difference in X5, kPa/L/s
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Delta R5
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Inspiratory - expiratory difference in R5 (total resitance), kPa/L/s
Before and 20 minuttes after inhaled Salbutamol 0.4 mg
FEF 25-75
Time Frame: Before and 20 minuttes after inhaled Salbutamol 0.4 mg
Expiratory Flow at 25% to 75% during spirometry, L and % predicted
Before and 20 minuttes after inhaled Salbutamol 0.4 mg

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Allergi- og Lungeklinikken, Elsinore

Investigators

  • Principal Investigator: Thomas J Ringbæk, MSci, Allergi og Lungeklinikken Helsingør

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 1, 2026

Primary Completion (Estimated)

December 31, 2027

Study Completion (Estimated)

December 31, 2027

Study Registration Dates

First Submitted

January 16, 2026

First Submitted That Met QC Criteria

January 16, 2026

First Posted (Actual)

January 23, 2026

Study Record Updates

Last Update Posted (Actual)

January 26, 2026

Last Update Submitted That Met QC Criteria

January 23, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • F-25059703

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

I have not applied for permission to share data with others.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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