Recognizing pulsus paradoxus requires the ability to measure systolic blood pressure while the patient is inhaling and exhaling. It can be done with a sphygmomanometer (the device that your healthcare provider uses to measure your blood pressure) but it is best to use an arterial line. An arterial line is a catheter inserted into an artery. It can be used to take blood samples of oxygenated blood or to measure the blood pressure in the arteries continuously and directly.
One of the reasons to regularly measure blood pressure at consistent intervals is to identify trends. A typical question caregivers get from both patients and newer care providers is why the blood pressure will fluctuate. It is a dynamic, organic process that has many factors affecting it. That’s why an arterial line is so much better as a blood pressure monitoring device of sick patients if it is available.