vital signs Flashcards
A fairly good indication of the efficiency of a person’s circulatory system can be obtained by taking
arterial pulse and blood pressure measurements. These measurements, along with those of respiratory rate and body temperature, are referred to collectively as vital signs in clinical settings.
Arterial Pulse
The alternating expansion and recoil of an artery that occurs with each beat of the left ventricle creates a pressure wave—a pulse—that travels through the entire arterial system. Normally the pulse rate (pressure surges per minute) equals the heart rate (beats per minute). The pulse averages 70 to 76 beats per minute in a healthy resting person. It is influenced by activity, postural changes, and emotions.
What are arterial pulse points, and how can they be used in emergencies?
Arterial pulse points are areas where arteries are close to the surface of the body, making it easy to feel the pulse by compressing the artery against firm tissue. The radial pulse at the wrist is commonly used to measure heart rate. Other clinically important pulse points include the carotid, brachial, femoral, and popliteal pulses. These points are also known as pressure points because they can be compressed to stop blood flow to distal tissues during significant blood loss or hemorrhage, such as in a severe injury where the brachial artery can be compressed to help stop bleeding in the hand.
What is blood pressure, and how does it work in the circulatory system?
Blood pressure is the force that the blood exerts against the inner walls of the blood vessels. It is the pressure created by the heart pumping blood through the body’s circulatory system. Blood pressure ensures that blood continues to circulate, even between heartbeats. It is particularly important in the large systemic arteries near the heart, where the pressure is highest. Blood pressure is essential for maintaining continuous blood flow and delivering oxygen and nutrients to tissues.
Blood Pressure Gradient
When the ventricles contract, they force blood into large, thick-walled elastic arteries close to the heart that expand as the blood is pushed into them.
How is blood flow driven in the circulatory system, and how is it similar to filtration?
Blood flow in the circulatory system is driven by pressure differences—similar to the process of filtration. In filtration, substances move from areas of high pressure to areas of low pressure through a filter. Similarly, blood flows from areas of high pressure (like the heart and arteries) to areas of low pressure (like veins and capillaries) without the need for a filter. This pressure difference is what drives the continuous movement of blood throughout the body.
How does blood flow through the circulatory system, and why is there a pressure difference between arteries and veins?
Blood flows through the circulatory system along a pressure gradient, from areas of high pressure to areas of low pressure. The pressure is highest in the large arteries closest to the heart and gradually drops as blood moves through smaller arteries, arterioles, capillaries, venules, and veins, ultimately reaching zero in the right atrium. The valves in veins, the milking action of skeletal muscles, and pressure changes in the thorax help ensure blood flows back to the heart. When an artery is cut, blood spurts out due to high pressure, while a vein cut causes steady blood flow due to lower pressure. This pressure drop is also seen in the pulmonary circulation.
Why is the elasticity of arteries important for continuous blood flow, and what happens when it is lost?
The elasticity of larger arteries is crucial for continuous blood flow because it allows the arteries to stretch when the heart pumps blood into them and recoil to maintain pressure on the blood as it moves through the vascular system. This is similar to how a garden hose with stiff walls would stop water flow if the faucet is turned off abruptly. When arteries lose their elasticity, as seen in arteriosclerosis (or “hardening of the arteries”), they can’t recoil properly, causing a drop in pressure and inefficient blood flow. The early stage of arteriosclerosis, atherosclerosis, is when plaques build up in the arteries, further reducing elasticity and causing complications
What are systolic and diastolic blood pressures, and how are they measured?
Systolic pressure is the pressure in the arteries at the peak of ventricular contraction, when the heart pumps blood. Diastolic pressure is the pressure in the arteries when the ventricles are relaxing. Blood pressure is measured in millimeters of mercury (mm Hg), with the systolic pressure listed first (e.g., 120/80 means a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg). Blood pressure is commonly measured using the auscultatory method, which involves listening to blood flow sounds in the brachial artery using a stethoscope and a sphygmomanometer (blood pressure cuff).
How is arterial blood pressure related to cardiac output and peripheral resistance?
Arterial blood pressure (BP) is directly related to cardiac output (CO) and peripheral resistance (PR). The relationship can be expressed by the equation:
BP = CO × PR
Cardiac output (CO) is the amount of blood pumped out of the left ventricle per minute.
Peripheral resistance (PR) is the resistance to blood flow in the arteries and smaller vessels.
We’ve already discussed regulation of cardiac output, but here, we focus on how peripheral resistance affects blood pressure.
What factors influence peripheral resistance, and how do they affect blood pressure?
Peripheral resistance (PR) is the friction or resistance to blood flow as it moves through blood vessels. The most significant factors that increase peripheral resistance include:
Vasoconstriction (narrowing of blood vessels), particularly arterioles, due to sympathetic nervous system activity or atherosclerosis (plaque buildup in arteries).
Increased blood volume or increased blood viscosity (thickness).
Any factor that increases either cardiac output (CO) or peripheral resistance (PR) leads to an immediate rise in blood pressure. Factors like age, weight, time of day, exercise, body position, emotional state, and various drugs can all influence blood pressure.
