Is forced oscillation technique the next respiratory function test of choice in childhood asthma

Figure 1 Typical arrangement of the forced oscillatory impedance measurement, adapted from. Pao: Input pressure at the airway opening; V’ao: Output flow.

Figure 2 Demonstration of lung function measurements using FOT. On the left, a photograph of the FOT test being performed in a 5-year-old boy. The hands of the investigator support the cheeks and the floor of the mouth of the child. The nose is blocked using a nose clip. The lips are sealed around the mouthpiece. On the right, Different breathing patterns during FOT measurements are shown, as observed on the flow-time trace in L/s. A: Normal tidal breathing; B: Breath holding spells; C: An aberrant activity (e.g., coughing, swallowing, or noise); D: A leak around the mouthpiece. FOT: Forced oscillation technique.

Figure 3 Changes in resistance (Rrs) and reactance (Xrs) as function of oscillation frequency.