A patient monitor is the screen beside a hospital bed that shows a patient's vital signs, such as heartbeat, blood pressure and blood oxygen, and raises an alarm when a reading crosses a limit. It is also called a bedside monitor or a vital signs monitor. Vital signs are the basic measurements that show how the body is doing.
The monitor takes its readings from sensors on the patient. Three or five stickers on the chest, called electrodes, pick up the heart's electrical signals for the ECG, the electrocardiogram. A clip on a finger, called a pulse oximeter, shines red and infrared light through the finger and measures the oxygen in the blood. This reading is shown as SpO2. A cuff on the arm inflates by itself, for example every 15 minutes, to measure blood pressure. In the ICU, a thin tube in an artery may also measure the blood pressure with every beat.
The screen shows two kinds of information. Waveforms are moving lines, such as the shape of each heartbeat. Numbers show the current values, such as a heart rate of 82. Each reading is stored with its time, as a time series, so a nurse can scroll back through the last few hours.
Here is a typical case. In the ICU of a hospital in Jaipur, a 55-year-old man is recovering after an abdominal operation. The nurse has set his SpO2 alarm at 90%. Over ten minutes, his SpO2 falls from 97% to 89%. The monitor sounds a medium-priority alarm and shows the reading in yellow. The same alarm appears on the central station, a screen at the nurses' desk that shows every bed in the unit. When the reading falls to 85%, the alarm becomes high priority, and turns red. The nurse reaches the bed within a minute.
Most alarms do not need any action. A loose sticker or a moving arm can set one off. When nurses hear hundreds of alarms a day, they begin to ignore some of them. This problem is called alarm fatigue. Monitor software tries to reduce it, for example by waiting a few seconds to confirm a reading before it sounds an alarm.
The monitor also sends its readings onward. ICU device integration software collects them from every bed, calculates early warning scores and charts them in the hospital EHR. ECGs can be sent for remote ECG interpretation. The hospital's biomedical engineers check each monitor's accuracy with biomedical test equipment. For a patient who is walking about, a Holter monitor records the heart instead.