ECG, Respiration and SpO2 tracings

ECG, Respiration and SpO2 tracings

Most modern cardiac monitors incorporate monitoring of pulse oximetry,  and the respiratory rate in addition to ECG. The respiratory rate is shown as 20/minute, heart rate as 73/minute and oxygen saturation as 95%. Respiratory rate is measured using the cyclical change in thoracic impedance with inspiration and expiration. A small current is passed between a pair of ECG monitoring electrodes to measure the thoracic impedance. Please note that ECG and pulse oximetry are shown on the same time scale while respiration is not. Generally, the ratio between heart rate and respiration is around 4:1.

ECG is monitored using multiple electrodes, but often only one channel is displayed on the monitor. If needed the monitor display settings can be altered to display more than one lead at a time. Simultaneous display of multiple leads is useful while analyzing arrhythmias on screen.

Pulse oximetry is measured using a probe kept usually on the finger or sometimes on the ear lobe. Infrared and red light beams are transmitted through a thin region like finger or earlobe and the absorption of the signal measured in the distal sensor. From this the saturation of hemoglobin with oxygen can be measured, as oxyhemoglobin and deoxyhemoglobin have different absorption patterns. Pulsatile value will correspond to arterial oxygen saturation.