Electrode Motion Artifacts in Electrical Impedance Pneumography

For electrical impedance pneumography, we measured electrode motion artifacts for four different electrode circuits (bipolar, tetrapolar, guarded bipolar, and guarded tetrapolar). Experiments used 10 different electrode configurations each with 4 different subject activities on 10 subjects. These show that 1) the common small-area bipolar electrode configuration is the worst in several measures of artifact sensitivity; 2) increasing the electrode area from 0.8 to 33 cm2 reduces the mean compliant, arm-motion and body-motion artifacts to 57, 45, and 32 percent, respectively, of normal; 3) changing the circuit from bipolar to tetrapolar without changing area changes these artifacts to 106, 65, and 65 percent of normal; 4) changing the circuit from bipolar to guarded bipolar without changing area reduces these artifacts to 87, 57, and 55 percent of normal; and 5) changing the circuit from guarded bipolar to guarded tetrapolar without changing area changes these artifacts to 106, 91, and 110 percent of normal. These results suggest that developers of apnea monitors use larger area electrodes and consider use of a tetrapolar or guarded bipolar circuit.