Blood pressure:
1. Blood pressure is the force exerted by blood on artery walls.
2. Systolic blood pressure is during ventricular contraction, averaging 120 mmHg in a healthy adult.
3. Diastolic blood pressure is during ventricular relaxation, averaging 80 mmHg.
4. Represented as a ratio like 120/80 mmHg, indicating systolic over diastolic pressure.
5. Pulse pressure, the difference between systolic and diastolic pressure, is typically 40 mmHg.
Measurement of blood pressure:
1. Blood pressure is measured using a sphygmomanometer.
2. The instrument includes an inflatable cuff, connected to a mercury manometer and rubber bulb.
3. During measurement, the person lies down, and the cuff is tightly wrapped around the upper arm.
4. The cuff is inflated until the brachial artery is blocked, then slowly lowered to detect pulsatile sounds (Korotkoff sounds).
5. The systolic pressure is noted when the first pulsatile sound is heard, and the diastolic pressure is recorded when no pulsatile sound is heard. An optimal blood pressure is around 120/80 mmHg.
Factors affecting blood pressure:
1. Cardiac output: Normal cardiac output is 5 liters/min, and an increase in cardiac output elevates systolic pressure.
2. Peripheral resistance: It depends on the diameter of blood vessels. A decrease in arteriolar and capillary diameter due to vasopressin increases peripheral resistance, leading to higher blood pressure.
3. Blood volume: Loss of blood in accidents reduces blood volume, resulting in decreased blood pressure.
4. Viscosity of blood: Blood pressure is directly proportional to blood viscosity.
5. Age: Blood pressure tends to increase with age due to the growing inelasticity of blood vessels.
6. Venous return: The amount of blood returned to the heart through veins per unit time is the venous return, and it’s directly proportional to blood pressure.
7. Length and diameter of blood vessels: Blood pressure is directly proportional to the total length of blood vessels and can be affected by vasoconstriction or vasodilation.
8. Gender: Females generally have slightly lower blood pressure than males before menopause, but the risk of high blood pressure increases in females after menopause.