Pleth on the monitor refers to the pulse volume, suggesting heart rate and pulse intensity, the normal value of its parameters is generally 60-100 times / min, different hospitals, the reference value may vary, often with other items to jointly monitor the patient’s vital signs. The monitor uses photoelectric technology to record waveforms of blood volume changes in human tissues to clarify information about the patient’s heartbeat, blood circulation and vascular status, and the detection technology has many advantages such as non-invasive, continuous, stable and easy to operate, which is one of the most important means of collecting cardiovascular physiological and pathological information at present. Before using the monitor, patients need to clean the local skin, shave off body hair if necessary, regularly observe the skin at the electrode piece site, and change the electrode position to prevent breakage of the skin due to long-term stimulation. Also avoid interference from other electronic products to prevent affecting its data and waveform. For agitated patients, the electrodes and leads should be fixed to avoid electrode dislocation or lead folding, and the monitor should be closely observed and recorded to provide a basis for patient’s condition change, condition analysis and adjustment of treatment plan.