A blood pressure test can be either an invasive procedure performed by a doctor or nurse, or a non-invasive procedure done either by a medical professional or a layman. An invasive blood pressure test typically involves the insertion of a needle directly into an arterial blood vessel, so that pressure may be measured there. The non-invasive type of blood pressure test typically involves the use of an arm or wrist cuff. This kind of test can be done in a doctor's office, though some retail locations, such as drug stores, may also have blood pressure machines available for self-testing. Both invasive and non-invasive tests are designed to determine the diastolic, or minimum blood pressure, and systolic, or maximum blood pressure.
Direct monitoring via an arterial line can provide the most accurate blood pressure test results. This invasive procedure allows a doctor or nurse to monitor blood pressure on a beat-by-beat basis, which can allow them to identify rapid changes in blood pressure. There are several possible complications from this kind of monitoring, such as infection or severe bleeding, so it is generally only used when precise measurements, over a period of time, are required. Some instances that may call for this blood pressure monitoring might involve patients in intensive care, or in instances of anesthesiology.
The simplest and least precise method of non-invasive blood pressure testing is simple palpitation. This involves simply feeling for radial, femoral, and carotid pulses, as lower blood pressure can cause a pulse not to be felt in radial or femoral locations. This type of method can only give a general idea of blood pressure, and is usually only used in emergency situations when an actual and more accurate test cannot be done.
The form of blood pressure testing most often used in clinical settings is called the auscultatory method. This involves the placement of an inflatable cuff around the patient's arm, which a medical professional inflates using a rubber bulb. The doctor or nurse then listens to the brachial artery before slowly releasing the pressure. He or she is then able to take the systolic pressure measurement when they first hear a rushing sound through their stethoscope, and the diastolic once the sound has ceased. This relatively accurate method of blood pressure testing often also uses a column of mercury to measure pressure.
The oscillometric method is the other non-invasive blood pressure test. This type also uses an inflated cuff, but involves the monitoring of oscillations in the cuff pressure. These changes are caused by the difference in systolic and diastolic blood pressure, and allow these two readings to be determined. This method may also use an electronic version of the device, where an electronic pressure sensor automatically measures the oscillations and the device displays the readings on a digital readout. Both mechanical and electronic oscillometric devices are available for home use, in order to allow people to monitor their blood pressure on a day-to-day basis.