Adaptive frequency domain filtering for improved non-invasive blood pressure estimation

A system for processing an oscillometric signal from a plurality of pressure steps of a blood pressure cuff to determine the blood pressure of a patient, the oscillometric signal having at least one artifact due to the acquisition of the oscillometric signal with the blood pressure cuff, the system comprising:

• a heart rate monitor connected to the patient, wherein the heart rate monitor is a separate modality from the blood pressure cuff, the heart rate monitor acquires the patient's heart rate at each pressure step;
• a time-to-frequency domain converter that receives the oscillometric signal acquired at each pressure step and converts the oscillometric data into the frequency domain:
• a fundamental frequency computer connected to the heart rate monitor, the fundamental frequency computer deriving a fundamental frequency of the heart rate at each pressure step;
• a fundamental frequency filter connected to the time-to-frequency domain converter and the fundamental frequency computer, the fundamental frequency filter comprising a pass band centered at the fundamental frequency of the heart rate at each pressure step, the fundamental frequency filter producing a harmonic frequency filter frequency domain oscillometric signal;
• a harmonic frequency computer connected to the heart rate monitor, the harmonic frequency computer deriving at least a harmonic frequency of the heart rate at each pressure step;
• a harmonic frequency filter connected to the time-to-frequency domain converter and the harmonic frequency computer, the harmonic frequency filter comprising at least one pass band centered at the harmonic frequency of the heart rate at each pressure step, the harmonic frequency filter producing a harmonic frequency filtered frequency domain oscillometric signal;
• a reconstruction calculator that receives the fundamental frequency filtered frequency domain oscillometric signal and the harmonic frequency filtered frequency domain oscillometric signal and reconstructs a time domain oscillometric signal without the at least one artifact from the received filtered frequency domain oscillometric signals;
• an oscillometric envelope calculator that processes the time domain oscillometric signal at each pressure step to produce an oscillometric envelope from envelope data points corresponding to each pressure step;
• and
• a blood pressure determination calculator connected to the oscillometric envelope calculator, the blood pressure determination calculator analyzes the oscillometric envelope to determine the blood pressure of the patient.

A method of determining a blood pressure of a patient, the method comprising:

• operating a blood pressure cuff through a plurality of pressure steps;
• acquiring oscillometric signals at each of the a plurality of pressure steps, the oscillometric signals having at least one artifact due to the acquisition of the oscillometric signals with the blood pressure cuff;
• acquiring a heart rate of the patient at each pressure step with a heart rate monitor of a separate modality from the blood pressure cuff, each acquired heart rate associated to an oscillometric signal acquired at a same pressure step;
• computing the fundamental frequency of each of the acquired heart rates with a fundamental frequency computer operating on a processing unit;
• computing at least one harmonic frequency of each of the acquired heart rates with a harmonic frequency computer operating on the processing unit;
• converting each of the oscillometric signals to a frequency domain oscillometric signal with a time to frequency converter;
• removing acquisition artifacts from each oscillometric signal by:
• filtering, with the processing unit, the frequency domain oscillometric signal with a band pass filter centered on the fundamental frequency of the associated heart rate to produce a first filtered frequency domain signal consisting of frequency domain oscillometric data centered at the fundamental frequency of the associated heart rate;
• filtering, with the processing unit, the frequency domain oscillometric signal with at least one band pass filter centered on at least one harmonic frequency of the associated heart rate to produce a second filtered frequency domain signal consisting of frequency domain oscillometric data centered at the at least one harmonic frequency of the associated bean rate;
• and
• reconstructing the oscillometric signal in the time domain from the first and second filtered frequency domain signals with an oscillometric waveform reconstructor operating on the processing unit to produce a reconstructed oscillometric signal;
• computing at least one data point from each of the reconstructed oscillometric signals;
• computing an oscillometric envelope from the computed data points;
• and
• determining at least one of mean arterial pressure, systolic pressure, and diastolic pressure from the oscillometric envelope.