How does the patient monitor measure breath?

There is no breathing module on the patient monitor, how does it monitor breathing?

The respiration on the monitor relies on the electrode pads of the electrocardiogram to sense the impedance changes of the thorax and display the waveform and data of the respiration.Because the electrodes on the lower left and upper right are breathing sensing electrodes, their sticking position is very important. The 2 electrodes should be placed as diagonally as possible for optimal respiration waves.

If the patient mainly breathes abdominally, the lower left electrode should be glued to the most obvious part of the left abdomen.