9-2 
 
 
Lead I     Lead II 
 
9.3.1 Optimizing Lead Placement for Resp 
If you want to measure Resp when you are measuring ECG, you may need to optimize the 
placement of the two electrodes between which Resp will be measured. Repositioning ECG 
electrodes from standard positions results in changes in the ECG waveform and may 
influence ST and arrhythmia interpretation. 
 
 
9.3.2 Cardiac Overlay 
Cardiac activity that affects the Resp waveform is called cardiac overlay. It happens when the 
Resp electrodes pick up impedance changes caused by the rhythmic blood flow. Correct 
electrodes placement can help to reduce cardiac overlay: avoid the liver area and the 
ventricles of the heart in the line between the respiratory electrodes. This is particularly 
important for neonates. 
 
 
9.3.3 Abdominal Breathing 
Some patients with restricted movement breathe mainly abdominally. In these cases, you may 
need to place the left leg electrode on the left abdomen at the point of maximum abdominal 
expansion to optimize the respiratory wave.