In a blood pressure measurement of 110/70, the number 70 is the __. a. systolic pressure b. diastolic pressure c. pulse pressure d. mean arterial pressure
The correct answer and explanation is:
The correct answer is b. diastolic pressure.
Explanation:
In a blood pressure reading such as 110/70 mmHg, the two numbers represent different phases of the cardiac cycle:
- Systolic pressure (the top number): This is the pressure in the arteries when the heart contracts (systole) and pumps blood out into the arteries. It represents the maximum pressure exerted on the arterial walls during a heartbeat. In this example, the systolic pressure is 110 mmHg.
- Diastolic pressure (the bottom number): This is the pressure in the arteries when the heart is resting between beats (diastole), allowing the chambers to fill with blood. It represents the minimum pressure exerted on the arterial walls when the heart is relaxed. In this example, the diastolic pressure is 70 mmHg.
Why is the diastolic pressure important?
The diastolic pressure is crucial because it reflects the baseline pressure in the arteries and the resistance the blood vessels exert against blood flow when the heart is not actively pumping. It gives insight into the tone and elasticity of the arterial walls and overall cardiovascular health.
Other options:
- Pulse pressure (c) is the difference between systolic and diastolic pressure. It is calculated as: $$
\text{Pulse Pressure} = \text{Systolic} – \text{Diastolic} = 110 – 70 = 40 \text{ mmHg}
$$ - Mean arterial pressure (d) is the average pressure in the arteries during one cardiac cycle, often approximated by the formula: $$
\text{MAP} \approx \text{Diastolic Pressure} + \frac{1}{3}(\text{Pulse Pressure}) = 70 + \frac{1}{3}(40) = 83.3 \text{ mmHg}
$$
MAP is important because it represents the perfusion pressure seen by organs in the body.
Summary:
- 110 = systolic pressure (heart contracting)
- 70 = diastolic pressure (heart resting)
- The number 70 is the diastolic pressure, indicating arterial pressure when the heart relaxes.