Figure 3. Step driven flow depends on ventilatory phase.

(A) Variation in the magnitude of step-driven flows is apparent, particularly during low frequency breathing, as shown here during 3∶1 (strides per breath) coupling. Note the reversal in flow in late expiration (asterisk). Dashed vertical lines indicate footstrike events (data from subject 3). (B) Average step-driven flow (means ±95%CI) for a representative subjective at four points in the ventilatory cycle: 1) early expiration, high lung volume (90% V_max), 2) late expiration, low lung volume (10% V_max), 3) early inspiration, low lung volume (10% V_max) and 4) late inspiration, high lung volume (90% V_max).