Use of the frequency spectrum of artifact in oscillometry

A method of processing oscillometric data for use in determining the blood pressure of a patient, the method comprising:

• receiving an oscillometric signal from a blood pressure cuff connected to the patient;
• receiving an indication of the heart rate of the patient;
• computing a fundamental frequency and at least one harmonic frequency of the heart rate;
• converting the oscillometric signal to the frequency domain;
• filtering the frequency domain signal with separate pass bands centered at the fundamental frequency and the at least one harmonic frequency;
• determining the energy of the frequency domain oscillometric signal in the pass bands;
• determining the energy of the frequency domain oscillometric signal in at least portions of the signal other than the pass bands;
• calculating a ratio of the energy of the frequency domain oscillometric signal outside the pass bands to the energy of the frequency domain oscillometric signal within the pass bands;
• reconstructing the oscillation signal from the filtered frequency domain signal in the pass bands when the calculated ratio is below a threshold;
• and
• computing an oscillometric envelope data point for the current pressure within the blood pressure cuff based upon the reconstructed oscillometric signal.

A system for processing oscillometric data for use in determining the blood pressure of a patient, the system comprising:

• a heart rate monitor connected to the patient, the heart rate monitor acquiring the patient heart rate;
• a blood pressure cuff positioned on the patient and deflatable in a series of pressure steps;
• 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 harmonic frequency calculator connected to the heart rate monitor, the harmonic frequency calculator deriving at least a heart rate fundamental frequency and at least one harmonic frequency;
• a first filter having a first pass band centered around the fundamental frequency;
• a second filter having a second pass band centered around the at least one harmonic frequency;
• a controller for calculating a ratio of the energy of the frequency domain signal outside each of the first and second pass bands to the energy of at least a portion of the frequency domain oscillometric signal within the first and second pass bands;
• and
• a blood pressure determination calculator that determines an oscillometric envelope data point when the calculator ratio is below a threshold.