TPR BP is an abbreviation that stands for “total peripheral resistance blood pressure”. It refers to a measurement that is used to assess the status of a person’s cardiovascular system.
What is Total Peripheral Resistance?
Total peripheral resistance (TPR) is a measurement of the resistance that the heart must overcome to pump blood through the circulatory system. It indicates how hard the heart has to work to push blood through the blood vessels and get it circulating around the body.
Peripheral resistance occurs because blood has to squeeze through narrow blood vessels. The main factors that contribute to peripheral resistance are:
- Blood vessel diameter – narrower blood vessels create more resistance to blood flow
- Blood viscosity – thicker, more viscous blood is harder to push through blood vessels
- Vessel length – longer blood vessels increase resistance
Total peripheral resistance is the sum of all the resistance present throughout the entire systemic circulatory system, excluding the pulmonary (lung) circulation. It represents the cumulative effect of all these factors that oppose blood flow and make the heart work harder.
How is Total Peripheral Resistance Calculated?
Total peripheral resistance is calculated using the following formula:
TPR = (Mean Arterial Pressure) / (Cardiac Output)
Where:
- Mean Arterial Pressure (MAP) is the average pressure in arteries during one cardiac cycle
- Cardiac Output (CO) is the volume of blood pumped by the heart per minute
So in simple terms:
TPR = Resistance to Blood Flow
A higher TPR indicates more resistance to blood flow, while a lower TPR indicates less resistance.
What is Blood Pressure?
Blood pressure is the force exerted by circulating blood against the walls of blood vessels. It is measured using two numbers:
- Systolic pressure – the pressure in the arteries when the heart contracts
- Diastolic pressure – the pressure in the arteries when the heart relaxes between beats
Blood pressure is typically expressed like this:
117/76 mmHg
Where 117 is the systolic pressure and 76 is the diastolic pressure. The unit of measurement mmHg means millimeters of mercury.
Normal blood pressure is considered to be below 120/80 mmHg. High blood pressure (hypertension) is diagnosed when blood pressure is consistently above 130/80 mmHg.
What is TPR Blood Pressure?
TPR blood pressure refers to the mean arterial pressure (MAP) component that is used to calculate total peripheral resistance. As mentioned earlier:
TPR = MAP / CO
So the TPR blood pressure is the MAP – the average blood pressure in the arteries during one cardiac cycle.
Measuring TPR blood pressure along with cardiac output provides key information about peripheral resistance and cardiovascular dynamics that can help assess health status.
Why Measure TPR Blood Pressure?
Measuring TPR blood pressure, along with cardiac output, can provide insight into how hard the heart is working to pump blood and overcome total peripheral resistance. This helps assess the status of the cardiovascular system.
Some key reasons TPR blood pressure is measured include:
- Monitor cardiovascular function and circulatory status
- Evaluate response to medications and interventions that affect blood pressure and circulation
- Identify changes in peripheral resistance that may be abnormal
- Guide treatment in critically ill patients or those with conditions like shock or heart failure
- Research purposes in physiology and circulation studies
Having both TPR blood pressure and cardiac output data allows more complete evaluation of cardiovascular status than blood pressure alone. It provides extra information about whether issues relate to the heart’s pumping ability, vascular resistance, or both.
Normal TPR Blood Pressure Range
Normal TPR blood pressure ranges are generally considered to be:
- 70 – 110 mmHg for young, healthy adults
- 90 – 150 mmHg for middle-aged or elderly adults
However, the normal TPR can vary substantially depending on age, fitness level, health conditions, and measurement method.
Significantly high or low TPR blood pressure may indicate problems like:
- High TPR – increased peripheral resistance, peripheral artery disease
- Low TPR – sepsis, anaphylaxis, spinal shock
But it must be interpreted in context of the clinical picture and other measurements.
How is TPR Blood Pressure Measured?
There are invasive and non-invasive methods to measure TPR blood pressure and calculate total peripheral resistance:
Invasive Methods
- Arterial catheter – involves inserting a thin tube into an artery, allowing direct arterial blood pressure monitoring.
- Thermodilution technique – a catheter with a thermistor at the tip is used to inject cold saline into the heart and measure blood flow changes to determine cardiac output.
Non-Invasive Methods
- Sphygmomanometry – uses an inflatable cuff around the arm and stethoscope or doppler probe to measure systolic and diastolic blood pressure.
- Finometers – portable finger cuff devices that can continuously estimate blood pressure.
- Echocardiography – uses ultrasound to visualize the heart’s structure and function and estimate cardiac output.
- Bioimpedance – uses resistance to small electrical currents passed through the body to estimate cardiac output.
Invasive arterial catheter monitoring tends to be the most direct and accurate method. But non-invasive methods allow broader use while still providing valuable information in many cases.
What Affects TPR Blood Pressure?
Many physiological and pathological factors can affect TPR blood pressure by altering peripheral resistance and cardiac output:
| Factor | Effect on TPR BP |
|---|---|
| Exercise | Decreases – improves CO, dilates vessels |
| Anxiety, stress | Increases – raises HR, constricts vessels |
| Hypovolemia | Increases – decreases blood volume/CO |
| Medications (e.g. vasodilators) | Decreases – dilates vessels, reduces resistance |
| Sepsis | Decreases – vasodilation, increased CO |
| Obesity | Increases – raises resistance |
| Pregnancy | Decreases – vasodilation present |
Conclusion
In summary, TPR blood pressure refers to the mean arterial pressure component used to calculate total peripheral resistance in the cardiovascular system. Measuring TPR helps evaluate circulatory status and peripheral resistance issues that impact blood pressure and blood flow. It provides key information alongside cardiac output to better understand cardiovascular dynamics in health and disease.