Blood Pressure

• • Blood pressure is the force that pushes against the walls of blood vessels.

  • It is measured in millimetres of mercury (mmHg).

  • Blood pressure is generated by the contraction of the ventricles and it is therefore highest in the aorta and pulmonary artery. Blood pressure increases during ventricular systole and decreases during diastole.
• • The arterial pressure rises and falls as the heart goes through the cardiac cycle.

  • During ventricular systole the pressure in the aorta rises to a maximum e.g. 120mmHg.

  • During ventricular diastole it falls to a minimum e.g.70mmHg.

  • As blood flows round the body it is travelling through thin blood vessels which causes friction between the blood and the vessel walls.

  • This friction slows the blood down and by the time the blood reaches the right atrium the pressure is almost back to 0mmHg.
• • Blood pressure is found to vary considerably from person to person.

  • A typical reading for a healthy young adult would be a systolic pressure of 120mmHg and a diastolic pressure of 80mmHg.

  • This is written as 120/80mmHg.
• Sphygmomanometer


  Device used to measure systolic and diastolic blood pressure
• Measuring blood pressure

  1. Cuff is placed over the arm

  2. The cuff is inflated until the pressure stops blood flowing through the arm

  3. The cuff is allowed to deflate gradually until the pressure of blood in the artery is higher than the pressure of the cuff

  4. A pulse can now be felt and blood can be heard going through the artery using a stethoscope

  5. The pressure at which this first occurs is the SYSTOLIC pressure

  6. More air is released from the cuff until the sound of spurting blood disappears and a pulse is no longer detected

  7. The pressure at which this first occurs is the DIASTOLIC pressure
• Systolic pressure


  The pressure at which the pulse can first be felt and blood can be heard going through the artery using a stethoscope
• Diastolic pressure


  The pressure at which the sound of spurting blood disappears and a pulse is no longer detected
• Hypertension

  • Hypertension (high blood pressure) is the prolonged elevation of blood pressure when at rest.

  • It is normally indicated when systolic pressure is 140mmHg and diastolic is greater than 90mmHg.

  • It is fairly common in adults over the age of 35.

  • It is a MAJOR risk factor for many diseases such as CORONARY HEART DISEASE or STROKES.