Oscillometry – The future of estimating pulmonary functions

The prevalence of asthma is increasing rapidly, worldwide, due to changing gene-environment interactions. The rate of rise is more in resource poor nations due to lack of knowledge and non-availability of expertise. Monitoring of lung functions is mandatory for diagnosis and further management of asthmatic patients. Spirometry, the widely available investigation, is the gold standard test used for mapping pulmonary dynamicity. It has got its own limitations in the form of operational difficulties in children, the elderly, and in those with neuromuscular or behavioral issues. In the current era of COVID-19 pandemic, the utility of spirometry has been further restricted to selected cohort only, due to potential risk of viral transmission during the procedure. Oscillometry technique has been used previously, to monitor lung functions, with promising results. Ultrasonic waves of various frequencies accompany the tidal breath of patients and respiratory impedance is calculated by measured pressure and flow signals from exhaled breath. The results are interpreted in the form of resistance, reactance, resonant frequency, and reactance area. Various manufacturers have developed different mechanical models with slight variation in impulse pattern till date. There are certain distinct advantages of oscillometry over spirometry. Being tidal breath-based maneuver, it is more child friendly. People with neuromuscular weakness, cognitive limitations, and the elderly can easily perform it with only minor understanding and effort. Oscillometry is more sensitive than spirometry in detecting peripheral airway diseases. Post-bronchodilator reversibility can be evaluated by comparing with the baseline respiratory characteristics. Their utility in restrictive diseases and vocal cord dysfunction has also been explored. Less aerosol generation during the normal tidal breath is another advantage of oscillometry, over spirometry needing forceful efforts, which makes it more suitable for use in viral pandemic situations for monitoring patients with both asthma and pneumonia. More research is needed, in various geographic locations and heterogeneous populations, to devise the normative data of oscillometric parameters. Simultaneously, there is an urgent need for standardization of available machines at global platform.