Growing interest had been focused on the involvement of the small airways in asthma. and impulse oscillometry (IOS) has been utilized as pulmonary functions for detecting large and small airways diseases separately. IOS can measure respiratory resistance and reactance at multiple frequencies. not available by spirometry or body plethysmography. https://www.roneverhart.com/Open-Box-Apple-Watch-Series-6-GPS-Cellular-40mm-Space-Gray-Aluminum-w-Black-Sport-Band/