LAUSR

Multichannel patient monitors apparently display the electrocardiogram, intra-arterial blood pressure, and pulse oximetry waveforms in synchrony during sinus cardiac rhythm. We recorded 20 events of a premature cardiac contraction on multichannel monitors from 10 patients. Interestingly, during premature cardiac contraction, the low-amplitude arterial trace was aligned with the premature electrocardiogram, but the low-amplitude pulse oximetry plethysmograph was aligned with the next normal electrocardiogram and arterial tracing. In conclusion, the pulse oximetry plethysmograph tracing is offset by 1 ventricular depolarization on the electrocardiogram (QRS) and the arterial tracing on multichannel monitors.