What does 1001 mean during cardiopulmonary resuscitation?

Cardiopulmonary resuscitation 1001 refers to a timing method used by medical staff to determine whether the patient has a pulse, such as the four-digit number "1001, 1002, 1003...", so that the time of each count is close to one seconds, the pulse check will be more accurate and will not time out. If the patient's pulse cannot be sensed within the specified time, cardiopulmonary resuscitation needs to be performed immediately.