Review of measurement methods and clinical validation studies of noninvasive blood pressure monitors

Abstract

Existing standardized protocols for clinical validation of noninvasive blood pressure (BP) monitors do not have specific provisions for monitors that require patient-specific calibration by a secondary method or device before use. This article seeks to identify accuracy requirements and protocol considerations for such monitors. Measurement methods that require patient-specific calibration were reviewed to identify their clinical accuracy requirements. Validation studies of monitors that use these methods were reviewed to identify limitations in their protocols. For a monitor that requires patient-specific calibration, inadequate adaptation of existing protocols can fail to validate the accuracy of the monitor for its intended use. A protocol for such a monitor must have provisions to assess the monitor's accuracy in tracking intrapatient BP changes, from the calibrated level, after a calibration or between calibrations. Performing a patient-specific calibration with a patient at rest and immediately evaluating the monitor against a reference method with the patient also at rest will not assess this accuracy, because changes in BP at rest and over a short time are generally small compared with those that occur over 24 h. For validation purposes, intrapatient BP changes can be achieved by validating the monitor over an extended period or induced by means of physical maneuvers or pharmacological interventions. The secondary method or device used for the calibration must be accurate. The protocol must also have provisions to assess the monitor's ability to correct for changes in hydrostatic pressure, reject or correct for motion artefacts, and correct for other factors that affect measurement accuracy during use. There is a need to establish protocol provisions to ensure that noninvasive BP monitors that require patient-specific calibration are properly validated for their intended use before they are placed on the market or introduced into clinical use.

Impact of heart disease and calibration interval on accuracy of pulse transit time–based blood pressure estimation

“…The PTT-based BP technique requires individual-specific calibration by a secondary method of device before use. Thus, the accuracy depends not only on the accuracy of the calibration method or device but also on the accuracy of the method used to track intraindividual BP changes from the calibration level, after a specific calibration (Ng 2011). The present study of different calibration intervals implies that the accuracy of BP estimation decreases as the calibration interval increases, which is consistent with findings of previous studies (Cattivelli andGarudadri 2009, McCarthy et al 2013) and our earlier work (Poon et al 2008); the calibration interval in this study lasted for approximately one month, which was far longer than similar studies (Choi et al 2013).…”

Noninvasive continuous hemodynamic monitoring

“…Measurements with the Nexfin are performed without the need for an external calibration whereas other devices using finger cuff technology such as the Finometer [17, 60] and the CNAP require extra measurements with an upper arm cuff [61]. A recent overview of noninvasive BP monitors and clinical validation studies focused specifically on the need for calibration by a separate method [62]. …”

A Novel Modular Tonometry-Based Device to Measure Pulse Pressure Waveforms in Radial Artery

“…The sensor housing holds the sensor and is typically used to flatten the artery. In the process of arterial compression, the housing design can create additional stresses on the surface leading to errors in reading [19]. Sensor centering over the artery is achieved by either manual location for maximum palpations or manual location combined with automatic feedback algorithms for improved sensitivity [20].…”

“…Device parameters such as the amount of wrist flexion and the selection of HDP mostly remain similar across different patient groups. Devices in some cases become bulky due to the incorporation of pneumatic chambers [19] and/or stepper motors [20] for automatic centering. Finally, most devices are expensive, which limits their availability in low-and medium-income countries.…”