| No direct BP measurement |
-
•
Cuffless devices estimate BP as a function of derived variables that rely on multiple sensors, proprietary algorithms, and regular calibration with cuff-based devices
-
•
In contrast, cuff-based devices make sphygmomanometer-based direct measurements in millimeters of mercury (mm Hg)
|
|
| No ideal referent standard |
-
•
Intra-arterial lines are not appropriate for ambulatory settings and physical activity
-
•
Office devices are only validated in resting states
-
•
ABPM’s reliance on oscillometry makes ABPM an indirect measure of SBP and DBP
|
|
| Static-state assumptions violated |
-
•
Calibration is performed in the seated, rested position, but the device is used in states of physical activity
-
•
BP estimates are subject to drift with time
|
|
| “Zero out” bias phenomenon |
-
•
Since postcalibration measurements vary around the calibrated, resting value, the mean of beat-to-beat measures may have a central tendency toward the calibrated, resting value
-
•
In beat-to-beat measurements, pseudo-precision occurs owing to repetition and the large number of measurements
|
|
| Applicability to heterogenous populations |
-
•
Radial artery may not be easily accessible in patients with obesity, large wrist circumference, or peripheral artery disease
-
•
Assumptions about transduction of PTT and PAT may not be generalizable to patients with obesity, high density of chest hair, or large breasts
-
•
The impact of skin pigmentation on device performance remains unclear
|
|
| Reliance on heart rate |
-
•
Unlike oscillometric devices, which measure MAP and extrapolate SBP and DBP, cuffless devices rely on HR to inform estimation in change of BP
-
•
Pulse-BP dissociation occurs in patients who are taking medications (eg, beta-blockers) or who have arrhythmias (eg, atrial fibrillation), and in healthy individuals during sleep
|
