In medicine, the ratio of physiologic dead space over tidal volume<unk>  is a routine measurement, expressing the ratio of dead-space ventilation <unk>  to tidal ventilation <unk> , as in physiologic research or the care of patients with respiratory disease.
VD/VT
T wave alternans
High frequency QRS
J wave
Spike-and-wave
Delta wave
OPQRST
Cannon A waves