Method and instrument for automated measurement of skin perfusion pressure

Abstract

An automatic skin perfusion measuring device automatically analyzes perfusion measurements to identify motion artifact and SPP values. Motion artifact is ignored. Perfusion measurements are designated as SPP values if various criteria are met. SPP value criteria pertain to factors including cuff pressure, perfusion, perfusion change percentages relative to previous and subsequent perfusion measurements, and whether perfusion measurements are increasing or decreasing relative to previous and subsequent perfusion measurements.

1 . An automated skin perfusion pressure measuring device comprising: 
 an inflatable cuff;    a first sensor in communication with the cuff;    a second sensor in communication with the cuff for reading pressure levels in the cuff;    a pressure instrument in fluid communication with the cuff for inflation and deflation thereof, the pressure instrument comprising:    a source of pressurized air;    a conduit connected to the source of pressurized air and the cuff, thereby placing the source of pressurized air in fluid communication with the cuff;    a microprocessor arranged to receive inputs from the first sensor and the second sensor, the microprocessor capable of controlling pressurized airflow to and from the cuff;    a computer program executable by the microprocessor such that when executed, the computer program causes the microprocessor to: 
 initiate an automatic inflation sequence resulting in a no flow condition;  
 initiate an automatic deflation sequence;  
 automatically qualify a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence.  
   
   
   
       2 . The automated skin perfusion pressure measuring device of  claim 1  wherein the first sensor is positioned underneath the cuff.  
   
   
       3 . The automated skin perfusion pressure measuring device of  claim 1  wherein the first sensor is positioned distal to the cuff.  
   
   
       4 . The automated skin perfusion pressure measuring device of  claim 1  wherein the first sensor is positioned inside a bladder within the cuff.  
   
   
       5 . The automated skin perfusion pressure measuring device of  claim 1  wherein the first sensor is selected from the group consisting of optical probe means, pulse oximeter means; optical plethemography means; motion detecting means; and laser Doppler means.  
   
   
       6 . The automated skin perfusion pressure measuring device of  claim 5  wherein the optical probe means comprises a laser transmitter fiber and a receiver photodiode.  
   
   
       7 . The automated skin perfusion pressure measuring device of  claim 5  wherein the optical probe means comprises a laser transmitter.  
   
   
       8 . The automated skin perfusion pressure measuring device of  claim 7  wherein the optical probe means further comprises a receiver photodiode.  
   
   
       9 . The automated skin perfusion pressure measuring device of  claim 5  wherein the optical probe means is connected to the pressure instrument via a fiber optic cable.  
   
   
       10 . The automated skin perfusion pressure measuring device of  claim 1  wherein said one or more conditions comprise the perfusion measurement being within 1 mmHg to approximately 150 mmHg.  
   
   
       11 . The automated skin perfusion pressure measuring device of  claim 10  wherein if said perfusion measurement is less than 0.20% and said cuff pressure is less than 100 mmHg, then said one or more conditions comprise a perfusion increase of from 10% to 50% from a previous perfusion measurement.  
   
   
       12 . The automated skin perfusion pressure measuring device of  claim 10  wherein if said perfusion measurement is greater than 0.02% and said cuff pressure is greater than or equal to 100 mmHg, the said one or more conditions comprise a perfusion increase of from about 20% to about 80%.  
   
   
       13 . The automated skin perfusion pressure measuring device of  claim 10  wherein if said perfusion measurement is from 0.15% to about 0.20% and said cuff pressure is any valid cuff pressure, the said one or more conditions comprise a perfusion increase of from about 25% to about 100%.  
   
   
       14 . The automated skin perfusion pressure measuring device of  claim 10  wherein if said perfusion measurement is less than 0.15% and said cuff pressure is any valid cuff pressure, the said one or more conditions comprise a perfusion increase of from about 50% to about 200%.  
   
   
       15 . The automated skin perfusion pressure measuring device of  claim 1  wherein the said one or more conditions comprises the perfusion measurement being from about 0.05% to about 0.2%.  
   
   
       16 . The automated skin perfusion pressure measuring device of  claim 1  wherein said one or more conditions comprise whether steps following the perfusion measurement being tested for as an SPP value are decreasing.  
   
   
       17 . The automated skin perfusion pressure measuring device of  claim 16  wherein if the cuff pressure is low, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is one.  
   
   
       18 . The automated skin perfusion pressure measuring device of  claim 16  wherein if the cuff pressure is at a medium range, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is two.  
   
   
       19 . The automated skin perfusion pressure measuring device of  claim 16  wherein if the cuff pressure is high, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is three.  
   
   
       20 . The automated skin perfusion pressure measuring device of  claim 16  wherein if the cuff pressure is very high, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is five.  
   
   
       21 . The automated skin perfusion pressure measuring device of  claim 1  wherein said one or more conditions comprise whether steps following the perfusion measurement being tested for as an SPP value are increasing.  
   
   
       22 . The automated skin perfusion pressure measuring device of  claim 21  wherein if the cuff pressure is low, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is one.  
   
   
       23 . The automated skin perfusion pressure measuring device of  claim 21  wherein if the cuff pressure is at a medium range, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is two.  
   
   
       24 . The automated skin perfusion pressure measuring device of  claim 21  wherein if the cuff pressure is high, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is three.  
   
   
       25 . The automated skin perfusion pressure measuring device of  claim 21  wherein if the cuff pressure is very high, the number of steps analyzed following the perfusion measurement being tested for as an SPP value is five.  
   
   
       26 . The automated skin perfusion pressure measuring device of  claim 1  further comprising a display monitor operably connected to the pressure instrument and capable of displaying data.  
   
   
       27 . The automated skin perfusion pressure measuring device of  claim 26  wherein the display monitor is capable of displaying data pertaining to microcirculation within an observation volume of tissue.  
   
   
       28 . The automated skin perfusion pressure measuring device of  claim 26  wherein the display monitor is further capable of displaying data pertaining to cuff pressure.  
   
   
       29 . The automated skin perfusion pressure measuring device of  claim 28  wherein the display monitor is further capable of graphically displaying cuff pressure versus microcirculation within an observation volume of tissue.  
   
   
       30 . The automated skin perfusion pressure measuring device of  claim 1  wherein the cuff comprises a transparent window useable to observe the perfusion sensor.  
   
   
       31 . A method of measuring skin perfusion pressure in a patient comprising: 
 providing an inflatable cuff in communication with a first sensor;    initiating an automatic inflation sequence resulting in a no flow condition;    initiating an automatic deflation sequence; and    automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence.    
   
   
       32 . The method of  claim 31  wherein initiating an automatic inflation sequence comprises: 
 inflating the cuff to a first pressure;    verifying the first sensor is detecting and measuring perfusion;    inflating the cuff to a second pressure;    verifying a no flow condition is achieved, otherwise:    increasing cuff pressure in predetermined increments until a no flow condition is achieved;    aborting the inflation sequence if the cuff pressure attains a predetermined maximum value before a no flow condition is achieved.    
   
   
       33 . The method of  claim 32  wherein inflating the cuff to a first pressure comprises inflating the cuff to 5 mmHg to 10 mmHg.  
   
   
       34 . The method of  claim 32  wherein inflating the cuff to a second pressure comprises inflating the cuff to approximately the patient's systolic pressure.  
   
   
       35 . The method of  claim 32  wherein increasing the cuff pressure in predetermined increments until a no flow condition is achieved comprises increasing the cuff pressure in predetermined increments of approximately 40 mmHg until a no flow condition is achieved.  
   
   
       36 . The method of  claim 31  wherein automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence further comprises identifying that the measured skin perfusion pressure is not the result of motion artifact.  
   
   
       37 . The method of  claim 31  wherein automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence comprises determining whether the perfusion measurement is within a valid range to qualify as an acceptable SPP value.  
   
   
       38 . The method of  claim 37  wherein determining whether the perfusion measurement is within a valid range to qualify as an acceptable SPP value comprises determining whether the perfusion measurement is within 1 mmHg to approximately 150 mmHg.  
   
   
       39 . The method of  claim 31  wherein automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence comprises determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value.  
   
   
       40 . The method of  claim 39  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether the perfusion increase is from 10% to 50% when the perfusion measurement is greater than 0.20% and the cuff pressure is less than 100 mmHg.  
   
   
       41 . The method of  claim 39  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether the perfusion increase is from 20% to 80% when the perfusion measurement is greater than 0.20% and the cuff pressure is greater than or equal to 100 mmHg.  
   
   
       42 . The method of  claim 39  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether the perfusion increase is from 25% to 100% when the perfusion measurement is from 0.15% to 0.20% and the cuff pressure is any valid cuff pressure.  
   
   
       43 . The method of  claim 39  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether the perfusion increase is from 50% to 200% when the perfusion measurement is less than 0.15% and the cuff pressure is any valid cuff pressure.  
   
   
       44 . The method of  claim 31  wherein automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence further comprises analyzing a number of subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing.  
   
   
       45 . The method of  claim 44  wherein analyzing a number of subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing comprises analyzing one subsequent perfusion measurement if the cuff pressure is from 0 to 20 mmHg.  
   
   
       46 . The method of  claim 44  wherein analyzing a number of subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing comprises analyzing two subsequent perfusion measurements if the cuff pressure is from 10 to 50 mmHg.  
   
   
       47 . The method of  claim 44  wherein analyzing a number of subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing comprises analyzing three subsequent perfusion measurements if the cuff pressure is from 40 to 120 mmHg.  
   
   
       48 . The method of  claim 44  wherein analyzing a number of subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing comprises analyzing five subsequent perfusion measurements if the cuff pressure is from 80 mmHg to 150 mmHg.  
   
   
       49 . The method of  claim 44  wherein automatically qualifying a perfusion measurement as an SPP value upon one or more conditions being met during the deflation sequence further comprises a condition selected from the group consisting of (i) when the cuff pressure is less than 15 mmHg and one subsequent perfusion measurement is increasing; (ii) when cuff pressure is from 15 to 20 mmHg and two subsequent perfusion measurements are increasing; (iii) when cuff pressure is from 50 to 100 mmHg and three subsequent perfusion measurements are increasing; (iv) when cuff pressure is 100 mmHg to 150 mmHg and five subsequent perfusion measurements are increasing.  
   
   
       50 . A device for measuring skin perfusion pressure in a patient comprising: 
 an inflatable cuff with perfusion sensing means for sensing perfusion in communication with said cuff;    means for automatically inflating the cuff, according to an automatic inflation sequence, to a pressure resulting in a no flow condition;    means for automatically deflating the cuff according to an automatic deflation sequence;    means for testing a perfusion measurement against a set of predetermined criteria to reject motion artifact and automatically qualify an SPP value.    
   
   
       51 . The device of  claim 50  wherein the automatic inflation sequence comprises: 
 inflating the cuff to a first pressure;    verifying the perfusion sensing means is detecting and measuring perfusion;    inflating the cuff to a second pressure;    verifying a no flow condition is achieved;    increasing cuff pressure in predetermined increments until a no flow condition is achieved;    aborting the inflation sequence if the cuff pressure attains a predetermined maximum value before a no flow condition is achieved.    
   
   
       52 . The device of  claim 50  wherein the automatic inflation sequence inflates the cuff to a first pressure of 5 mmHg to 10 mmHg.  
   
   
       53 . The device of  claim 50  wherein the automatic inflation sequence inflates the cuff to the patient's systolic pressure.  
   
   
       54 . The device of  claim 50  wherein the automatic inflation sequence increases the cuff pressure in predetermined increments of 40 mmHg until a no flow condition is achieved.  
   
   
       55 . The device of  claim 50  wherein the automatic deflation sequence comprises: 
 (a) releasing pressure from the cuff at a desired controlled rate;    (b) monitoring the deflation rate;    (c) aborting the deflation sequence if the deflation rate is not substantially equal to the desired controlled rate;    (d) analyzing whether a perfusion measurement qualifies as an SPP value using the testing means;    (e) determining whether at least one automatic stop criterion has been met;    (f) repeating steps (a)-(e) until at least one automatic stop criterion has been met;    (g) reporting the SPP value from step (d) if any.    
   
   
       56 . The device of  claim 55  wherein the automatic deflation sequence further comprises: 
 (h) after a predetermined number of repetitions of steps (a)-(e) in the absence of an acceptable SPP value, continuing to repeat steps (a)-(e) for a predetermined period of time;    (i) displaying perfusion measurements on a display for physician interpretation.    
   
   
       57 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies as an acceptable SPP value comprises identifying that the measured perfusion pressure is not the result of motion artifact.  
   
   
       58 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies an acceptable SPP value comprises determining whether the perfusion measurement is within a valid range of pressure to qualify as an acceptable SPP value.  
   
   
       59 . The device of  claim 58  wherein determining whether the perfusion measurement is within a valid range to qualify as an acceptable SPP value comprises determining whether the perfusion measurement is within 1 mmHg to approximately 150 mmHg.  
   
   
       60 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies an acceptable SPP value comprises determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value.  
   
   
       61 . The device of  claim 60  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether at least one of the following criteria is met: 
 a perfusion measurement greater than 0.20% when cuff pressure is less than 100 mmHg, and the perfusion increase is from 10% and 50%;    a perfusion measurement greater than 0.20% when cuff pressure or greater than or equal to 100 mmHg, and the perfusion increase is from 20% and 80%;    a perfusion measurement of from 0.15% to 0.20% when the cuff pressure is any valid cuff pressure, and the perfusion increase is from 25% to 100%;    a perfusion measurement is less than 0.15%, when the cuff pressure is any valid cuff pressure, and the perfusion increase is from 50% to 200%.    
   
   
       62 . The device of  claim 60  wherein determining whether a perfusion increase from a prior measurement is greater than a predetermined minimum increase value comprises determining whether one of the following criteria is met: 
 a perfusion measurement greater than 0.20% with a cuff pressure less than 100 mmHg, and the perfusion increase is 25%;    a perfusion measurement greater than 0.20% with a cuff pressure greater than or equal to 100 mmHg, and the perfusion increase is 40%;    a perfusion measurement equal to from 0.15% to 0.20% with any valid cuff pressure, and the perfusion increase is 50%;    a perfusion measurement less than 0.15% with any valid cuff pressure, and the perfusion increase is 100%.    
   
   
       63 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies as an acceptable SPP value comprises determining whether the perfusion measurement is from 0.05% to 0.2%.  
   
   
       64 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies an acceptable SPP value comprises: 
 comparing the perfusion measurement to subsequent perfusion measurements to determine whether the subsequent perfusion measurements are increasing or decreasing;    qualifying the perfusion measurement as an SPP value if one criteria is met selected from the group consisting of (i) a cuff pressure of from 0 to 20 mmHg and one subsequent perfusion measurement is increasing; (ii) a cuff pressure of from  10  to 50 mmHg and two subsequent perfusion measurements are increasing; (iii) a cuff pressure of from 40 to 120 mmHg and three subsequent perfusion measurements are increasing; (iv) a cuff pressure greater than 80 mmHg and five subsequent perfusion measurements are increasing.    
   
   
       65 . The device of  claim 64  wherein qualifying the perfusion measurement as an SPP value comprises qualifying the perfusion measurement as an SPP value if one criteria is met selected from the group consisting of (i) a cuff pressure less than 15 mmHg and one subsequent perfusion measurement is increasing; (ii) a cuff pressure from 15 to 20 mmHg and two subsequent perfusion measurements are increasing; (iii) a cuff pressure of from 50 to 1 00 mmHg and three subsequent perfusion measurements are increasing; (iv) a cuff pressure of from 100 mmHg to 150 mmHg and five subsequent perfusion measurements are increasing.  
   
   
       66 . The device of  claim 55  wherein analyzing whether a perfusion measurement qualifies as an SPP value comprises: 
 defining a perfusion change profile;    determining whether the perfusion measurement is one of a sequence of perfusion measurements that fits the perfusion change profile.    
   
   
       67 . The device of  claim 66  wherein defining a perfusion change profile comprises defining a profile in which a measured perfusion measurement meets the criteria selected from the group consisting of (i) when cuff pressure is from 0 to 20 mmHg, a next subsequent perfusion measurement is not decreasing; (ii) when cuff pressure is from 10 to 50 mmHg, two immediately subsequent perfusion measurements are not decreasing; (iii) when cuff pressure is from 40 to 120 mmHg, three immediately subsequent perfusion measurements are not decreasing; (iv) when cuff pressure is greater than 80 mmHg, five immediately subsequent perfusion measurements are not decreasing.  
   
   
       68 . The device of  claim 67  wherein defining a perfusion change profile comprises defining a profile in which a measured perfusion measurement meets the criteria selected from the group consisting of (i) when cuff pressure is less than 15 mmHg, a next subsequent perfusion measurement is not decreasing; (ii) when cuff pressure is from 15 to 20 mmHg, two immediately subsequent perfusion measurements are not decreasing; (iii) when cuff pressure is from 50 to 100 mmHg, three immediately subsequent perfusion measurements are not decreasing; (iv) when cuff pressure is from 100 mmHg to 150 mmHg, five immediately subsequent perfusion measurements are not decreasing.