Two quantitative indexes of thoraco-abdominal synchrony, measured via respiratory inductive plethysmography. A: Rib-cage motion, abdominal motion, and their sum signal, which represents the tidal volume (VT). The maximum compartmental amplitude(MCA) is calculated as maximum abdominal motion maximum rib-cage motion. MCA/VT approaches 1.0 with improving synchrony. B: Konno-Mead diagram of abdominal motion versus ribcage motion. The phase angle () is calculated according to the formula sin1(M/S), where M is the horizontal distance of the Konno-Mead diagram at halfway between the maximal and minimal
rib-cage excursion, and S is the maximal abdominal excursion.
Asynchrony produces a wide open loop. Synchronous ribcage/
abdominal motion has a phase angle of 0°, and paradoxical
motion has a phase angle of 180°.