Currently, when doctors wish to continuously monitor a patient's blood pressure, they surgically insert a catheter into one of the individual's arteries. There could soon be a safer, much less invasive alternative, however, and it was inspired by the tuning of guitar strings.
While the existing "arterial catheterization" technique does provide accurate, continuous blood pressure readings, it's also time-consuming to initially set up and calibrate. More importantly, due to the fact that the catheter may stay in the artery for days at a time, patients may experience pain, infections, hemorrhaging, or ischemia (restricted blood flow).
For these reasons, the technique is typically limited to use on patients in acute care settings.
Less critical patients may instead be hooked up to machines that repeatedly perform traditional inflatable-arm-cuff-type blood pressure readings. These devices might miss blood pressure fluctuations that occur between readings, however, plus all of that arm-squeezing can become painful after a while.
Seeking a less problematic alternative, scientists from Caltech and California-based startup Esperto Medical looked to guitar strings.
When tuning a guitar, you adjust the tension of each string until it resonates at the desired tone/frequency when plucked. You could also reverse that process (sort of), in that you could analyze the plucked string's resonant frequency to determine the current tension of that string.
That's essentially how the Caltech/Esperto team's "resonance sonomanometry" system works.
Utilizing an external transducer, ultrasound pulses are sent down through the patient's skin and tissue to acoustically excite an underlying artery. By analyzing the echoes of those pulses, which are reflected off the artery and back up to the transducer, it's possible to see how the artery's dimensions subtly change as it vibrates.
Those telltale changes can in turn be used to determine the blood pressure in that artery.
Unlike some other experimental systems that utilize ultrasound to measure blood pressure, the resonance sonomanometry system requires no recalibration after its initial use on a given patient. It can also be used on any major artery, across a wide patient demographic.
The technology has already been tested on the carotid, axillary, brachial, and femoral arteries of human test subjects, with readings falling in line with those obtained through more traditional methods. And while a handheld ultrasound transducer is currently being used, the scientists state that it could be replaced with a much smaller device that could be worn on the patient's body at all times.
A paper on the research, which is being led by Esperto Medical's Raymond Jimenez, was recently published in the journal PNAS Nexus.
Source: PNAS Nexus via EurekAlert
