Blood pressure is one of the major vital signs of our body that help indicate our overall health, which is why people with high blood pressure or those who are diagnosed with hypertension are encouraged to monitor their blood pressure regularly. While most of us are accustomed to the non-invasive approach of BP monitoring, with the use of sphygmomanometers and home blood pressure monitors, there is another technique in measuring blood pressure levels.

The invasive approach

An invasive blood pressure monitoring involves the direct measurement of the patient’s blood pressure by creating an arterial line. By inserting a cannula needle in an artery and connecting it through a fluid-filled system into an electronic patient monitor, healthcare providers can closely and constantly monitor the patient’s blood pressure beat by beat, expressed by a waveform graph. Because of its aggressive approach, an intra-arterial blood pressure monitoring is not performed on just any patient.

Candidates for intra-arterial BP measurement

An intra-arterial blood pressure measurement is known to provide more accurate results than the non-invasive approach, which is why it is especially recommended for patients in critical care settings. Through an arterial line, doctors are provided rapid recognition of blood pressure changes, which is a benefit for patients under continuous infusions of certain vasoactive drugs. Moreover, it is also much easier for the healthcare team to draw repeated blood gas samples through arterial cannulation, minimizing injury to the patient.

Particularly, an arterial line placement is indicated for patients who need continuous direct monitoring, which is deemed impossible through non-invasive means, especially in individuals who are very thin, morbidly obese, have extremely low blood pressures, and have severe burns in the extremities. Aside from those needing frequent blood sampling, an arterial line also minimizes complications brought by repeated arterial puncture.

How intra-arterial BP monitoring works

While we already have a gist of blood pressure monitoring through intra-arterial means, there is still a lot to learn about its mechanism and how it works. Generally, there are three main parts of an intra-arterial monitoring system. The monitor comes in a variety of types, depending on its application, including single pressure, dual pressure, or the multi-parameter type. Meanwhile, the measuring apparatus includes the arterial cannula, which is connected to tubing that contains the continuous flow of saline solution that will then provide pressure that leads to the IBP transducer in a flushing system.

Obtaining accurate results

Although the intra-arterial method in acquiring measurement provides the most accurate results, there are still several conditions that need to be ensured to promote accuracy. For one, the cannula should be properly placed in the unobstructed artery and should not be obstructed or kinked. Clotting in the arterial catheter is known to tamper with the accuracy of the results. Healthcare providers need to ensure that there are no air bubbles in the transducer or tubing, as this is a common cause of error during an invasive blood pressure measurement. Furthermore, it is best to check that the monitor is calibrated accurately before proceeding with the monitoring.

Other than blood pressure, there are other health parameters that can be obtained through an arterial line, which includes the patient’s pulse rate and rhythm, continuous cardiac output with the use of pulse contour analysis, pulse pressure variation, ECG lead disconnection, and a lot more.

There are pros and cons to every medical procedure, and an intra-arterial blood pressure monitoring also has its fair share of them as compared to the non-invasive approach. Your doctor will have better knowledge and judgment in deciding which method to use depending on your case.