| abstract |
A piezoelectric transducer clamped onto the fingertip with a fixed pressure yields an indirect continuous blood pressure waveform that can be used to monitor a patient's blood pressure characteristics over extended periods of time and during most normal daily activities. There are two modes that this invention can operate in: absolute and relative pressure modes. In the absolute mode, a patient-calibrated clamping pressure is applied to hold the transducer in place and to cancel artifact. The systolic and diastolic blood pressure are taken directly from the measured waveforms. The systolic pressure equals the maximum peak pressure minus the clamping pressure. The diastolic pressure equals the minimum pressure minus the clamping pressure. In the relative mode, if patient motion artifact is not expected to be a problem, a patient-calibrated clamping pressure is not needed, because only a clamping pressure high enough to hold the transducer in place and low enough so as not to cause waveform distortion is needed. Since only relative pressures are measured with this mode the initially known systolic and diastolic pressures are used to calibrate the apparatus for subsequent pressure readings. The measured waveform systolic pressure and the measured diastolic waveform pressure corresponds to the initially known diastolic pressure. |