The OEM board for pulse wave analysis (PWA module) is intended for the non-invasive estimation of central blood pressure (systolic and diastolic value) and vascular conditions (augmentation pressure, augmentation index, and pulse wave velocity) in combination with a blood pressure measurement device that determines the blood pressure on the upper arm and fulfils the accuracy requirements of the ISO 81060-2.
The PWA module is an electronic board developed for health care medicine and designed to be integrated into a host system that have to be a medical device. In this case the PWA module is a subsystem of the superordinate medical device (see PHYSIO-PORT AS) and is connected to power supply, control lines, serial interface and the analog output of a pressure sensor. The control of the board is done by commands via the serial interface. The results of the measurement and other information are transmitted via this serial interface.
The PWA module has to be built in the host system that has to fulfil the general requirements for basic safety and essential performance of medical electrical equipment (IEC 60601-1) and the particular requirements for the basic safety and essential performance of automated non-invasive sphygmomanometers (IEC 80601-2-30).
The intended patient populations are adults and children with an age of at least 12 years. The PWA module is not intended to be used on neonates. The arm circumference of the patient has to be in the range of the employed cuffs.
The medical device with the integrated PWA module has to be intended for use following the consultation and instruction by a physician (family doctor, specialist or hospital). It can be used, if the physical condition of the patient allows an automatic, non-invasive blood pressure measurement. The PWA module is not intended to be used in intensive care medicine or for alarming of life-threatening conditions. Contraindications for the usage of the PWA module are arrhythmias, femoral artery stenosis, and pregnancy.
A measurement with PWA module can be combined with other measurements and medical examinations at the patient that do not affect the blood flow in the upper arm during the pulse wave analysis.
Description of the measurement procedure
The inflation of an external blood pressure cuff up to a defined pressure near the mean arterial pressure level of the patient is the basis of the measurement procedure. The module is a slave device that is controlled by the host system. The pressure control for the cuff and the time management has to be done by the host system (see PHYSIO-PORT AS). The PWA module merely controls the timing of his internal processes.
The host system has to provide the analog pressure signal without any preprocessing (filtering and amplification) to the analog input (PWA pin) of the module. The complete analog preprocessing is done by the module. The pressure level for the record of the pulse waves should be constant and the leakage should be less than 3 mmHg/min during the measurement procedure.
The PWA module records the pulse waves over a period of 15 seconds after a received start command. The recorded pulses are provided online for the host system and are stored internally on the PWA module for a later evaluation (see Figure).
Figure: Digitalized analog pressure signal provided by the PWA module
The raw data will be preprocessed by the module after the record phase. Afterwarde the pulswave analysis is conducted.
- Supporting non-invasive pulse wave analysis on mean arterial pressure level in the blood pressure cuff (see arterial stiffness)
- Recording and storage of an analog pressure signal derived from the upper arm
- Preprocessing with artifact elimination of the analog pressure signal
- Reconstruction of the central pulse contour
- Estimation of central blood pressure (systolic, and diastolic value)
- Decomposition of the central pulse wave into antegrade and retrograde pulse wave
- Supporting the estimation of vascular conditions with the pulse wave velocity
- Supporting spot and long-term pulse wave analysis up to 24 hours
- Multiple communication interfaces like TWI and UART
- Storage capacity for up to 100 measurements
- Bootloader for system updates in the field
- Operating voltage of 3.3 V with an maximal operating current of 60.0 mA
- Low power consumption of under 8.0 mA during sleep mode