9 Essential Questions about Blood Pressure – Answered

Healthcare professionals know that blood pressure is one of the most important measurements in medicine. It’s often the first metric tracked when a patient visits a physician’s office or hospital. But what makes blood pressure such a vital marker in one’s overall health picture? We’ve answered nine of your most common questions here.

 

With each heartbeat, blood is being pumped out into our arteries and throughout the body. Blood pressure is the force of this blood pushing against the walls of the arteries. 

 

Blood pressure is recorded with two numbers, such as 120/80 (which is read as “120 over 80”). The top number is the systolic pressure and the bottom number is the diastolic pressure. Systolic pressure measures the pressure on the arteries as the heart contracts and pumps blood, while the diastolic pressure is the pressure on the arteries when the heart is at rest in between heartbeats. Blood pressure readings are expressed in millimeters of mercury, abbreviated as mmHg. (Mercury was the liquid traditionally used in in blood pressure gauges.) 

 

The brachial artery is the major blood vessel that runs through the upper arm. When a blood pressure cuff is wrapped around a patient's upper arm and inflated, the brachial artery is occluded (i.e., blood flow through the artery is stopped). As the cuff is gradually deflated, blood flow resumes. This causes a tapping or thumping sound in the artery that can be detected with a stethoscope. The first of these audible tapping sounds marks the systolic pressure. When the tapping sounds cease, that signifies the diastolic pressure.

 

The tapping sounds that are heard when blood flow returns to the brachial artery are called Korotkoff sounds (or K-Sounds), named for Dr. Nikolai Korotkov, a Russian physician who discovered them in 1905. There are five phases: 

 

K-1 (Phase 1): The appearance of the clear tapping sounds as the cuff is gradually deflated. The first is defined as the systolic pressure. 

K-2 (Phase 2): The sounds in K-2 start to soften and are characterized by a swishing sound since the blood flow in the artery increases. 
K-3 (Phase 3): The sounds become crisper and louder in K-3, similar to the sounds heard in K-1. 
K-4 (Phase 4): As the blood flow becomes less turbulent, the sounds in K-4 are muffled and softer. Diastolic pressure is recorded at the end of Phase 4. 
K-5 (Phase 5): In K-5, the sounds disappear completely since the blood flow through the artery has returned to normal.