Arterial Blood Pressure
Arterial Blood Pressure-
The pressure is exerted when blood flows through the arteries. Generally, the term ‘blood pressure’ refers to arterial blood pressure.
Arterial blood pressure is expressed in four different terms-
- Systolic blood pressure
- Diastolic blood pressure
- Pulse pressure
- Mean arterial blood pressure.
Systolic blood pressure-
Systolic blood pressure (systolic pressure) is defined as the maximum pressure exerted in the arteries during systole of heart. Normal systolic pressure: 120 mm Hg (110 mm Hg to 140 mm Hg).
Diastolic blood pressure –
Diastolic blood pressure (diastolic pressure) is defined as the minimum pressure exerted in the arteries during diastole of heart.
Normal diastolic pressure: 80 mm Hg (60 mm Hg to 80 mm Hg).
Graded 1,2,3 According to systolic BP values in the ranges indicated-
| Category | Systolic BP, mmHg | Diastolic BP, mmHg | ||
| Optimal | < 120 | < 80 | ||
| Normal | 120–129 | 80–84 | ||
| High normal | 130–139 | 85–89 | ||
| Grade 1 hypertension |
|
90–99 | ||
| Grade 2 hypertension | 160–179 | 100–109 | ||
| Grade 3 hypertension | ≥ 180 | ≥ 110 | ||
| Isolated systolic hypertension | ≥ 140 | < 90 |
Systolic pressure and Diastolic pressure in Different Age-
| Age | Systolic pressure | Diastolic pressure |
| Newborn | 70 mm Hg | 40 mm Hg |
| After 1 month | 85 mm Hg | 45 mm Hg |
| After 6 month | 90 mm Hg | 50 mm Hg |
| After 1 year | 95 mm Hg | 55 mm Hg |
Pulse pressure-
Pulse pressure is the difference between the systolic pressure and diastolic pressure.
Normal pulse pressure: 40 mm Hg (120 – 80 = 40).
Mean arterial blood pressure-
Mean arterial blood pressure is the average pressure existing in the arteries. It is not the arithmetic mean of systolic and diastolic pressures. It is the diastolic pressure plus one third of pulse pressure. To determine the mean pressure, diastolic pressure is considered than the systolic pressure. It is because, the diastolic period of cardiac cycle is longer (0.53 second) than the systolic period (0.27 second).
Normal mean arterial pressure= 93 mm Hg (80 + 13 = 93).
Formula to calculate mean arterial blood pressure-
Mean arterial blood pressure = Diastolic pressure + 1/3 of pulse pressure
=80+ 40 ÷3 = 93.3 mm Hg