Monitoring neonatal peripheral circulation by electrocardiogram-to-oximeter pulse velocity

The plethysmo time interval (PTI) is the time interval between the beginning of QRS complex on ECG and the upstroke of the pulse wave on the plethysmogram as measured by a pulse oximeter. We examined whether measuring the PTI has clinical value for evaluating neonatal peripheral circulation. We correlated PTI values and measured, from the hand and foot, height and body weight of 14 neonates. PTI was strongly correlated with height (R2 = 0.85) and body weight (R2 = 0.78). Height was especially highly correlated, because PTI is principally affected by the distance from the heart to the measured site. We also measured PTI on three clinical cases (patent ductus arteriosus, hypovolemia, and persistent pulmonary hypertension of the newborn). PTI was shortened in cases of peripheral circulatory impairments, because pulse wave velocities increased due to the contraction of arterioles. We conclude that the PTI can evaluate the peripheral circulatory status of the neonate by applying a new principle of pulse oximeter that is widely used in neonatal intensive care units.