Blood pressure suddenly can not be measured, to observe the patient’s state, if the patient has no discomfort complaints, to observe whether the blood pressure measuring instrument failure, if the patient sweating, irritability, or even loss of consciousness, may be shock and other possibilities. If the patient has no discomfort and the blood pressure measurement does not produce data, observe whether the battery is dead, whether the contact between the cuff and the blood pressure instrument is good, and replace the blood pressure instrument to measure again. If the patient’s upper arm on the side where the blood pressure is measured is in severe pain, the skin temperature is lowered, and the skin is pale, it may be an acute thrombotic occlusion of the arteries of the upper extremity blood vessels, and the blood flow can not pass through, so the blood pressure can not be measured. Immediate medical attention is required. If the patient is pale, sweaty, diaphoretic incontinence, or even loss of consciousness, it is considered to be a state of shock, and the blood pressure has disappeared, such as anaphylactic shock, hemorrhagic shock, or the occurrence of ventricular tachycardia, cardiac arrest and other malignant cardiac arrhythmia, and the blood pressure may not be measured out at this time. Active resuscitation is needed. If the blood pressure suddenly fails to come out, it is recommended to seek immediate medical treatment after ruling out the problem of the blood pressure measuring instrument.