A newly developed non-invasive cuff-less BP sensor, the TLT Sapphire monitor (Tarilian Laser Technologies, Welwyn Garden City, U.K.) enables high fidelity direct beat-to-beat measurement of BP in digital format using patented optoelectronic methods without need for calibration, compression or energy entering the body. The sensor's main components comprise a light emitting diode (LED) utilising a semiconductor light source, a waveguide, a photodiode and a flexible button which is placed on the skin over the radial artery all housed within a strap. We evaluated the accuracy of this device compared to an intra-arterial BP catheter according to the ISO-81060–2:2013 standard.
Design and method:
Patients were recruited from the elective cardiothoracic surgical patient group who were indicated to receive an invasive radial arterial BP catheter as a standard of clinical care. Non-invasive BP was measured with the Sapphire 9 Monitor which was applied in the post-operative period to the contralateral wrist to the radial arterial line. The reference BP ranges were determined from the recording of the invasive BP for a duration of at least 30 seconds that included the period of the determination of the device-under-test for which 10 BP determinations per patient were recorded.
In total 12 adult men and 6 women with mean age of 59 years, BMI < 35 kgm2 and in sinus rhythm were studied. For the 180 separate pairs of readings, the mean values of the errors of the determinations between the indwelling arterial line and the optoelectronic device-under-test were:
Systolic BP: -0.22 mmHg (SD 2.76), ISO standard requires ± 5 mmHg, SD < 8
Diastolic BP: +3.91 mmHg (SD 5.04), ISO standard requires ± 5 mmHg, SD < 8
See Figure A below.
This is the first instance in which a static optoelectronic BP sensor has been compared to the intra-arterial BP gold standard. The results obtained for both systolic and diastolic pressures using the ANSI/AAMI ISO-81060-2:2013 Standard Criterion for “Clinical Investigations with Reference Invasive Blood Pressure Monitoring” meets the criterion of the Standard and so the TLT-Sapphire device can be recommended for blood pressure measurement in an adult population.