Related Experiment Video
Updated: Jun 13, 2026

Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship
Published on: January 8, 2019
Random variation of inspiratory lung function parameters in patients with COPD: a diagnostic accuracy study
Frank J Visser1, Sunil Ramlal, Ben Pelzer
1Department of Pulmonology, Canisius Wilhelmina Hospital, Nijmegen, 6532 SZ, the Netherlands. f.visser@cwz.nl
Inspiratory parameters like forced inspiratory volume in 1 second (FIV1) and inspiratory capacity (IC) show more consistent variability in chronic obstructive pulmonary disease (COPD) patients when expressed as percentage changes. This helps in accurately assessing bronchodilator response.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Chronic obstructive pulmonary disease (COPD) exhibits weak bronchodilator response in forced expiratory volume in 1 second (FEV1).
- Inspiratory parameters, including forced inspiratory volume in 1 second (FIV1) and inspiratory capacity (IC), may offer better responsiveness to bronchodilators.
- Accurate assessment of bronchodilator response in COPD requires understanding the random variation of these parameters, ideally with homoscedastic scatter.
Purpose of the Study:
- To investigate the random variation, including type and quantity, of key inspiratory parameters in stable COPD patients.
- To determine if percentage changes or absolute changes in inspiratory parameters provide a more homoscedastic scatter for assessing bronchodilator response.
Main Methods:
- Spirometry was performed on 79 stable COPD patients, measuring FIV1, IC, maximal inspiratory flow at 50% (MIF50), and peak inspiratory flow (PIF) multiple times.
- Measurements were taken within one hour, within one day, and between two different days to assess repeatability.
- Coefficient of repeatability (CR) and linear regression were used to analyze the data for scatter type (homo- or heteroscedastic).
Main Results:
- All measured parameters exhibited heteroscedastic scatter when differences were expressed as absolute values.
- Expressing differences as a percentage change from initial values resulted in more homoscedastic scatter for all parameters.
- The coefficient of repeatability (CR) within one hour for percentage changes was: IC (19%), FIV1 (14%), PIF (18%), and MEF50 (21%).
Conclusions:
- Percentage changes in FIV1, IC, and MIF50 are more suitable than absolute changes for achieving homoscedastic scatter in COPD patients.
- A significant bronchodilator improvement in an individual COPD patient must exceed the calculated coefficient of repeatability for the respective parameter.
More Related Videos
08:44Dual Test Gas Pulmonary Diffusing Capacity Measurement During Exercise in Humans Using the Single-Breath Method
Published on: February 2, 2024
06:22Machine Learning-Based Cough Tone Classification: Diagnostic Exploration of Chronic Obstructive Pulmonary Disease and Respiratory Tract Infections
Published on: September 19, 2025
Related Concept Videos
Chronic Obstructive Pulmonary Disease-IV: Assessement and Diagnostic Studies
Medical History
Chronic Obstructive Pulmonary Disease-I: Introduction
Pulmonary Function Tests
Pulmonary Function Tests are crucial diagnostic tools for assessing respiratory function, particularly in patients with chronic respiratory disorders. They comprehensively evaluate lung volumes, ventilatory function, breathing mechanics, diffusion, and gas exchange. These tests help diagnose pulmonary diseases and play a significant role in monitoring disease progression, evaluating disability, and assessing response to therapy.
PFTs involve using a spirometer, a...
Factors Affecting Pulmonary Ventilation
Alveolar Surface Tension
The alveolar fluid lines the luminal surface of the alveoli and exerts a force called surface tension. This force is caused by the polar water molecules in the liquid being more strongly attracted to each...
Respiratory Volumes
Tidal Volume (TV) Tidal volume (TV) is the air inhaled or exhaled in a...
Respiratory System Abnormal Finding I: Inspection and Percussion
Inspection Findings
During an inspection, several findings may suggest the presence of respiratory distress or disease. Pursed-lip breathing, where exhalation is slowed by...