Device and method for noninvasive continuous determination of physiologic characteristics

• US 6,921,367 B2
• Filed: 02/06/2004
• Issued: 07/26/2005
• Est. Priority Date: 10/07/1999
• Status: Expired due to Fees

• Current Assignee: Woolsthorpe Technologies Corporation
• Original Assignee: Woolsthorpe Technologies, LLC
• Inventors: Mills, Alexander K.
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US10/773,596
• Publication Number:
  US 20040162493A1
• Time in Patent Office: 536 Days
• Field of Search: 600/310, 600/481, 600500-508, 600/526, 600322-324
• US Class Current: 600/481
• CPC Class Codes: A61B 2560/0261 using hydrostatic pressure
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

The invention comprises devices for noninvasively monitoring physiological characteristics of a patient'"'"'s blood. Generally, probes having radiation emitters and detectors are used to determine absorbance of blood within the patient'"'"'s tissue to determine various blood parameters. The device also has either a position sensor for determining the position of the probe with respect to the patient'"'"'s heart or a movement generator for altering the position of the probe with respect to the patient'"'"'s heart. The invention also comprises methods for noninvasively monitoring the physiological characteristics. In one embodiemnt, induced positional changes create differential hydrostatic pressures to facilitate measurement of blood parameters by absorbance. In a second embodiment, delays in pulse arrival times in coupled organs or members on opposite sides of the body are measured to determine cardiac output. The two methods are such that they can advantageously be used together.

Claims

1. A method for noninvasively determining a physiological characteristic of a patient'"'"'s blood, comprising the steps of:

providing a tissue probe having a first radiation emitter with a first wavelength and a first radiation detector configured to receive the first wavelength after absorbance through the patient'"'"'s blood;

placing said tissue probe proximate an extremity of the patient;

placing said extremity at an initial position whereby said tissue probe is positioned at a first probe position relative to a level corresponding to the patient'"'"'s heart;

measuring absorbance of the patient'"'"'s blood at said first probe position by emitting a first radiation through the patient'"'"'s blood and detecting the radiation after passage through the patient'"'"'s blood;

computing a blood parameter at said first probe position based on said first probe position absorbance;

moving said extremity to at least a second extremity probe position relative to said first probe position;

measuring absorbance of the patient'"'"'s blood at said second extremity position;

comparing the rate of change of absorbance at said second extremity position with said first probe position absorbance to determine at least a first rate of change of absorbance value; and

determining central venous drainage from said rate of change of absorbance value.

2. The method of claim 1, further comprising the steps of determining the hydrostatic pressure difference between the position of said tissue probe corresponding to said central venous drainage and said first probe position and calculating the central venous pressure from said hydrostatic pressure difference.

3. A method for noninvasively determining a patient'"'"'s cardiac output, comprising the steps of:

providing a first tissue probe having a first radiation emitter and a first radiation detector, said first radiation emitter being adapted to emit first radiation having at least a first wavelength, said first radiation detector being adapted to receive said first radiation after absorbance through the patient'"'"'s blood;

providing a second tissue probe having a second radiation emitter and a second radiation detector, said second radiation emitter being adapted to emit second radiation having at least a second wavelength, said second radiation emitter being adapted to receive said second radiation after absorbance through the patient'"'"'s blood,

placing said first tissue probe proximate a first extremity of the patient;

placing said second tissue probe proximate a second, opposing extremity of the patient;

positioning said first extremity at a first extremity position whereby said first probe is positioned substantially coincident with a level corresponding to the patient'"'"'s heart;

positioning said second extremity at a second extremity initial position whereby said second tissue probe is positioned below said first tissue probe;

raising said second extremity to a plurality of second extremity levels;

measuring absorbance of the patient'"'"'s blood in said first extremity by emitting said first radiation through the patient'"'"'s blood and detecting said first radiation after passage through the patient'"'"'s blood;

substantially continuously measuring absorbance of the patient'"'"'s blood in said second extremity during said raising of said second extremity by emitting said second radiation through the patient'"'"'s blood and detecting said second radiation after passage through the patient'"'"'s blood;

determining the rate of change of second extremity absorbance at each of said second extremity levels relative to said first extremity absorbance to determine a plurality of rate of change of absorbance values; and

determining central venous drainage from said rate of change of absorbance values.

4. The method of claim 3, further comprising the steps of determining the hydrostatic pressure difference between the position of said second tissue probe corresponding to said central venous drainage and said first probe position and calculating central venous pressure from said hydrostatic pressure difference.