Home monitoring of asthma using oscillometry: seeking the signal in the noise

Asthma is defined physiologically as airways hyperresponsiveness that results in variable airflow obstruction. Usually, these physiological features are assessed by spirometry, but spirometry is typically performed in the pulmonary function laboratory or office as a one-time procedure and cannot capture the variability in obstruction over time. While spirometry can be done at more regular intervals at home, it takes significant training and consistent technique to produce reliable results. An appealing alternative is oscillometry, which can also be done at home, is much easier to do and provides even more detail about airflow obstruction than spirometry. Various methods have been used to measure and monitor variability of airflow obstruction over time. Studies have shown that peak flow (PEF) variability is increased during a period of loss of asthma control characterised by worse symptoms and lung function.1 2 This increased variability is also seen preceding a clinical exacerbation, leading to the idea of monitoring PEF variability to detect an increase that may signal an impending loss of asthma control.3 4 But measuring PEF reliably can be difficult, as can measuring spirometry, since both are effort dependent. However, variability in lung function is easily measured by oscillometry5 6 and may allow early prediction of an exacerbation of disease.7 8 In this issue …