Airway hyperresponsiveness (AHR) is a key feature of asthma. However, detecting it can be challenging, especially in patients with mild disease, intermittent symptoms, or difficulty performing conventional lung function tests. Respiratory oscillometry offers a complementary approach to evaluating airway function and may reveal changes in respiratory mechanics during bronchial challenge testing.
The possible sensitivity advantage is protocol- and threshold-dependent; it does not establish that oscillometry is diagnostically superior to spirometry.
What is respiratory oscillometry?
Respiratory oscillometry evaluates how the respiratory system responds to small pressure oscillations applied at the mouth. Unlike spirometry, which requires forced respiratory maneuvers, oscillometry measures respiratory impedance during normal tidal breathing.
This difference matters when evaluating patients who cannot consistently perform forced expiratory maneuvers. Young children, for example, may struggle to produce reliable spirometry results. Oscillometry allows clinicians to investigate respiratory mechanics without requiring maximal respiratory effort. However, improved feasibility does not by itself validate oscillometry as a replacement for spirometry.
Understanding resistance and reactance
Oscillometry measures respiratory impedance through two principal components:
- Resistance (R): Describes opposition to airflow within the respiratory system.
- Reactance (X): Reflects the combined effects of the elastic and inertial properties of the respiratory system.
Changes in these parameters can provide information about respiratory mechanics and their response to bronchial challenge agents or bronchodilators. Depending on the protocol and measurement frequency, oscillometry may also help characterize differences in the mechanical behavior of the respiratory system. Oscillometry assesses the mechanics of the respiratory system as a whole, including the airways, lung tissue, and chest wall; its measurements therefore do not represent airway calibre alone.
The European Respiratory Society’s technical standards emphasize standardized procedures, quality control, and consistent reporting. These measures help clinicians obtain reliable results and interpret oscillometry data appropriately.
Oscillometry vs. spirometry for detecting airway hyperresponsiveness
Spirometry remains a fundamental test for evaluating airflow limitation and bronchodilator responsiveness. However, it depends on the patient’s ability to perform acceptable forced respiratory maneuvers. Oscillometry offers a different perspective by measuring respiratory mechanics during quiet breathing.
The two methods may therefore detect different physiological consequences of bronchial narrowing, rather than functioning as interchangeable tests.
Why tidal breathing may matter during bronchial challenge
Bronchial challenge testing helps clinicians investigate suspected airway hyperresponsiveness when symptoms or initial lung function results do not provide a clear answer.
During a challenge test, a patient inhales a substance that can provoke airway narrowing. Clinicians then evaluate changes in respiratory function. Oscillometry can track changes in resistance and reactance without requiring repeated forced expiratory maneuvers. This approach may be particularly valuable in patients who have difficulty performing spirometry. Forced maneuvers and deep inspirations can also influence airway mechanics, so measuring during tidal breathing offers a complementary way to observe the respiratory response. This potential advantage is biologically plausible because deep inspirations may have variable bronchodilator or bronchoprotective effects in asthma. However, the European Respiratory Society standards state that further studies are needed to establish whether this results in greater clinical sensitivity.
Nevertheless, oscillometry does not replace spirometry in every clinical situation. Each technique provides different information, and clinicians should select and interpret tests according to the patient’s characteristics and diagnostic needs.
What does the evidence say about oscillometry and asthma?
A systematic review2 published in 2026 examined oscillometry for asthma diagnosis in children and young people. It included 11 studies investigating responses to bronchodilators or methacholine challenge tests. The review included children and young people aged 2–18 years, so its findings should not automatically be extrapolated to adults.
Because spirometric tests were used as the reference standards, the review primarily assessed how oscillometry compared with established physiological tests. It did not prove that oscillometry identifies clinically confirmed asthma more accurately than spirometry.
The review highlighted an important limitation: currently recommended oscillometry thresholds for bronchodilator responsiveness may have low sensitivity in this population. Therefore, promising physiological measurements do not automatically translate into a definitive asthma diagnosis. This limitation applies specifically to the currently recommended European Respiratory Society (ERS) bronchodilator-response thresholds in the included studies and should not be generalized to every oscillometry parameter or every bronchial-challenge protocol.2
Further research must establish reliable diagnostic thresholds and clarify how oscillometry findings relate to clinical symptoms, spirometry, and bronchial challenge results. The review could not perform a meta-analysis because of substantial heterogeneity in the oscillometry parameters, thresholds, and methods reported across studies.
For healthcare professionals, the practical takeaway is clear: oscillometry can complement established pulmonary function tests, but clinicians must interpret results within the broader clinical context.
A complementary approach to evaluating airway hyperresponsiveness
Respiratory oscillometry offers a valuable complement to spirometry and bronchial challenge testing, particularly when evaluating patients who have difficulty performing forced respiratory maneuvers. Although further research must establish optimal diagnostic thresholds, oscillometry provides additional insight into respiratory mechanics during tidal breathing. Combining appropriate pulmonary function tests with clinical findings can help healthcare professionals make better-informed decisions when investigating suspected asthma and airway hyperresponsiveness.
Integrating bronchial challenge testing into pulmonary function assessment
Understanding airway hyperresponsiveness often requires more than a single test. Combining bronchial challenge testing with pulmonary function measurements can provide complementary insights into airway behavior.
Provo X: efficient and reproducible bronchial provocation testing
The ProvoX*, by SCHILLER-GANSHORN, is a software-controlled dosimeter designed to perform inhalation bronchial provocation tests quickly and with reproducible results. It can operate as a standalone device or be integrated into a pulmonary function laboratory, in a devices such as the PowerCube Body+ body box.
By incorporating bronchial provocation into an appropriate diagnostic protocol, laboratories can evaluate airway responses alongside measurements from oscillometry and spirometry, helping clinicians build a more complete picture of respiratory function.
Interested in adding bronchial provocation testing to your laboratory? Contact us to learn more about ProvoX and request a personalized demonstration of its capabilities.
* Product availability is subject to local regulatory requirements. To confirm whether ProvoX is offered in your country, please contact your local SCHILLER distributor.
References
FAQ about respiratory oscillometry and bronchial challenge testing.
What is respiratory oscillometry, and how does it help evaluate airway hyperresponsiveness?
Respiratory oscillometry is a noninvasive pulmonary function test that measures respiratory impedance—including resistance and reactance—during normal tidal breathing. During bronchial challenge testing, changes in these parameters after exposure to a bronchoconstrictor may help detect airway hyperresponsiveness and airway narrowing. However, the most appropriate parameters and diagnostic thresholds vary according to the patient population, device, and testing protocol; therefore, oscillometry complements rather than universally replaces spirometry.
How does oscillometry differ from spirometry in asthma evaluation?
Spirometry measures expiratory airflow and volumes, particularly the forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC), during coordinated respiratory maneuvers that include forced expiration. It does not directly measure all lung volumes. Respiratory oscillometry measures respiratory resistance and reactance during quiet tidal breathing and requires minimal patient effort. Because the two tests assess different physiological properties, they can provide complementary information in the evaluation of suspected asthma.
Can respiratory oscillometry be useful for diagnosing asthma in children?
Respiratory oscillometry may be particularly useful in young children who cannot perform reliable forced spirometry maneuvers. It can provide information about respiratory mechanics and small-airway function, including in some children with normal spirometric results. Nevertheless, oscillometry alone does not establish an asthma diagnosis. The systematic review by Seneviratne et al. (European Respiratory Review, 2026) found substantial heterogeneity among studies and concluded that its diagnostic accuracy in children has not yet been definitively established. Results should therefore be interpreted together with symptoms, clinical history, bronchodilator response, spirometry when feasible, and other relevant investigations.
What is the role of oscillometry during bronchial challenge testing?
During bronchial challenge testing, oscillometry can measure changes in respiratory resistance and reactance after administration of a bronchoconstrictor such as methacholine, while the patient continues to breathe normally. It may detect bronchoconstriction that is not evident from changes in FEV₁ and can sometimes increase the sensitivity of the test, particularly in children or patients who have difficulty performing forced maneuvers. However, proposed thresholds vary widely, and interpretation should account for the patient’s age, the device, the protocol, and local reference values. In children, upper-airway shunting may also lead to underestimation of the pulmonary response.
What equipment is used for bronchial challenge testing?
Bronchial challenge testing requires a calibrated nebulizer or dosimeter capable of delivering a bronchoconstrictor agent according to a standardized protocol. The patient’s airway response is usually assessed with spirometry, particularly by measuring the forced expiratory volume in one second (FEV₁), although respiratory oscillometry may also be used in selected protocols.
ProvoX by SCHILLER-GANSHORN is a software-controlled dosimeter designed to perform inhalation bronchial provocation tests quickly and with reproducible results. It can operate as a standalone device or be integrated into a pulmonary function laboratory.