Blood pressure is a measurement reflecting the force exerted by circulating blood against the walls of the body’s arteries. Monitoring blood pressure offers valuable insights into cardiovascular health and can help identify potential issues early. While digital devices are widely used for convenience, the manual, auditory method of blood pressure measurement remains a foundational and accurate technique.
Essential Equipment
Manually listening to blood pressure requires two primary tools: a sphygmomanometer and a stethoscope. The sphygmomanometer consists of an inflatable cuff, a pressure gauge, and a bulb for inflation. This device works by temporarily occluding blood flow in an artery, typically the brachial artery in the upper arm. The stethoscope amplifies the sounds of blood flow as pressure is released from the cuff. Proper cuff sizing is important for accurate readings.
The Sounds of Blood Pressure
The sounds heard when manually measuring blood pressure are known as Korotkoff sounds. These sounds are generated by turbulent blood flow through the artery as the pressure in the cuff is gradually released. When the cuff pressure is high enough to completely stop blood flow, no sounds are heard. As the cuff pressure decreases, blood begins to flow in spurts, creating vibrations that produce the Korotkoff sounds.
There are five distinct phases of Korotkoff sounds. Phase I is characterized by the first appearance of faint, clear tapping sounds, which indicates the systolic blood pressure. As the cuff continues to deflate, the sounds may soften and acquire a swishing quality in Phase II. Phase III involves the return of sharper, crisper sounds, sometimes more intense than Phase I. In Phase IV, the sounds become muffled and softer, with Phase V marking the complete disappearance of all sounds, which corresponds to the diastolic blood pressure.
Step-by-Step Listening Technique
The individual should be seated quietly with their arm supported at heart level. The bare arm is preferred for accurate readings. The blood pressure cuff is then placed snugly around the upper arm, with the lower edge of the cuff positioned approximately one inch above the elbow crease. The stethoscope’s diaphragm is placed over the brachial artery, located in the antecubital fossa, which is the crease of the elbow.
The cuff is inflated rapidly to a pressure about 20-30 mmHg above the point where the pulse disappears. After inflation, the cuff is deflated slowly and steadily at a rate of about 2-3 mmHg per second. As the pressure drops, the first Korotkoff sound heard through the stethoscope indicates the systolic pressure. Listening carefully, the point at which the sounds completely disappear marks the diastolic pressure. Taking multiple readings, with a brief pause between each, can help ensure accuracy.
Interpreting the Numbers
Blood pressure readings are expressed as two numbers: systolic over diastolic. The systolic number represents the pressure in the arteries when the heart beats and pumps blood. The diastolic number reflects the pressure in the arteries when the heart rests between beats. Both numbers provide important information about cardiovascular function.
According to the American Heart Association (AHA) guidelines, a normal blood pressure reading is less than 120/80 mmHg. Blood pressure is considered elevated when the systolic pressure is between 120-129 mmHg and the diastolic pressure is less than 80 mmHg. High blood pressure, or hypertension, is categorized into stages: Stage 1 is indicated by a systolic pressure between 130-139 mmHg or a diastolic pressure between 80-89 mmHg, while Stage 2 is defined by a systolic pressure of 140 mmHg or higher or a diastolic pressure of 90 mmHg or higher. These ranges serve as guidelines, and any concerns about blood pressure readings should always be discussed with a healthcare professional.