Impulse Oscillometry Home A-Z Health Information Health Library A-Z Impulse Oscillometry Overview Impulse Oscillometry (IOS) is a non-invasive technique used for assessing lung function. It measures respiratory impedance, which includes both resistance and reactance in the airways, by applying small pressure oscillations to the respiratory system during normal breathing. This technique provides detailed information about the mechanical properties of the lungs and airways, making it particularly useful in diagnosing and monitoring conditions, such as asthma, COPD and other respiratory disorders. It is an excellent method to diagnose small airway obstruction, which can be missed by spirometry. Small airways are less than 2 mm in diameter and are usually affected first in obstructive airway disease; hence, IOS can be used to detect these diseases earlier (than by spirometry). IOS is non-invasive, easy to perform and requires minimal patient cooperation; therefore, it is suitable for a wide range of patients, including young children and older patients. Measurement Principle IOS uses sound waves or pressure impulses to create small oscillations in the airway. The patient's response to these oscillations is measured to determine respiratory impedance. Components of Impedance Resistance (R): Reflects the ease with which air flows through the airways. Increased resistance can indicate obstruction or narrowing of the airways.Reactance (X): Represents the elastic and inertive properties of the respiratory system. Changes in reactance can provide information about the stiffness or compliance of the lungs and chest wall. Clinical Applications Diagnosing and monitoring asthma, COPD and other obstructive lung diseases.Evaluating the effectiveness of bronchodilator therapy.Assessing respiratory function in patients with neuromuscular diseases or other conditions affecting breathing mechanics.