US Patent No. 5,551,020 August 27, 1996
The present invention is a method of processing and writing data to a database wherein the method comprises four broad steps: 1) manipulating data files into a more compact and efficient bite encoded form and preparing the files to receive additional data to link the files; 2) linking the files with pointers to form an overall data structure; 3) determining the potential physical memory address for the files’ data by optimizing available memory space for a given memory media wherein the files are partitioned into blocks of data which are sufficiently inclusive to permit retrieval of all required data with a single memory media read, yet small enough to allow all of the physical memory space to be fully utilized; and 4) generating reference tables to be interspersed with the data blocks wherein the reference tables track the physical location of related data, obviating the need for additional disk reads. The invention further comprises a system wherein said method is performed on a database contained on a first computer system so that the database can be written to a memory media of fixed size which can be used with a second computer system, such that memory access speed is enhanced, the density of information stored on the memory media is increased, yet the computational power needed to retrieve such information is reduced.
US Patent No. 5,680,868 October 28, 1997
A method and apparatus is provided for detecting blood pressure sounds produced by the opening snap of an artery in a patient in the presence of significant noise using the phase information contained in two microphone signals. The two microphones are placed on a patient along the axis of an artery with their centers separated by a distance such that blood pressure sounds picked up by the microphones will be out of phase. Pressure is applied to the artery such that the artery opens and closes during each heart cycle, the opening snap of the artery producing blood pressure sounds. The two microphone signals are filtered, preferably using band pass filters having pass bands corresponding to the frequency of the blood pressure sounds. The filtered microphone signals are sampled and multiplied together or convolved in the frequency domain to generate a microphone signal product. If the microphone signal product is negative, the detection of a valid blood pressure signal for that sampling time is indicated. In an alternative embodiment the slope of the two microphone signals at the sample time is also determined, A valid blood pressure signal is indicated when the microphone signal product is negative and either the two microphone signal slopes have inverse signs or are both less than a selected slope threshold. A selected number of consecutive valid blood pressure signal detection indicates the detection of a blood pressure sound. The detection of blood pressure sounds at a range of cuff pressures is used to determine the systolic and diastolic blood pressure levels of the patient.
US Patent No. 5,772,600 June 30, 1998
A method and apparatus for automatically recognizing meaningful patterns in non-stationary periodic data is provided. The invention may be used in making measurements of physiological phenomena, such as arterial blood pressure, wherein data of interest is undergoing small changes in timing and magnitude in succeeding cycles, and wherein noise artifacts are detected along with the data of interest. Data points of interest are identified by grouping all received data points into family groups of multi-dimensional data points wherein each data point in the family group has dimensional values similar to at least one other data point in the family. The present invention may preferably be employed for the determination of a patient’s systolic and diastolic blood pressure levels. For this application, the data points include a time dimension value corresponding to the delay time between an ECG signal and the detection of a potential blood pressure sound by a microphone placed in an inflatable cuff on the arm of a patient, and a magnitude dimension value corresponding to the cuff pressure at the time of the potential blood pressure sound detection. Data points are collected for a series of cuff pressures ranging from above the systolic blood pressure level of the patient to below the diastolic blood pressure level of the patient. The highest and lowest pressures of data points in the family containing the largest number of data points are used to derive the systolic and diastolic blood pressure levels of the patient, respectively.
A method and apparatus is provided for distinguishing blood pressure sounds from noise in an automatic blood pressure monitoring system using the information contained in two microphone signals. Two microphones are placed on a patient along an axis of an artery to pick up blood pressure sounds. Pressure is applied to the artery such that the artery opens and closes during each heart cycle, the opening snap of the artery producing a blood pressure sound. The two microphone signals are sampled, filtered, and multiplied together to produce a microphone signal product. The microphone signal product is wave width filtered to remove therefrom portions of the signal having a wave width which is less than a selected minimum wave width value. A blood pressure sound is indicated as being detected when an amplitude of this wave width filtered microphone signal product exceeds a noise signal threshold level. The microphone signal product is also wave width filtered to remove therefrom portions of the signal having a wave width which is greater than a selected maximum wave width value. The amplitude of the resulting noise amplitude signal is used to adjust dynamically the noise signal threshold level in response to changing noise conditions. The detection of blood pressure sounds at a range of applied pressure levels is used to determine the systolic and diastolic blood pressure levels of the patient.
A signal processing method, preferably for extracting a fundamental period from a noisy, low-frequency signal, is disclosed. The signal processing method generally comp rises calculating a numerical transform for a number of selected periods by multiplying signal data by discrete points of a sine and a cosine wave of varying period and summing the results. The period of the sine and cosine waves are preferably selected to have a period substantially equivalent to the period of interest when performing the transform.