Obtaining cardiovascular parameters using arterioles related transient time

Abstract

Methods, systems and apparatus for monitoring equivalent inner diameter of arteriole-like blood vessels and related cardiovascular parameters, where by measuring a time difference between signals from larger blood vessels, like arteries (excluding arterioles), and smaller blood vessels, similar to arterioles by their physiologic properties, also taking concurrent heart rate value into account. In case the signal from larger blood vessels is measured geometrically relatively far from such a signal from smaller, arteriole-like blood vessels, said measured time difference may be evaluated by several ways in order to separate a PWTT component of time differences, obtained from said measured signals, from transient time component, including information about changes of diameter in arteriole-like vessels. It also may be effective defining more correctly the role of blood viscosity in monitored vascular condition of patient.

What is claimed is: 
     
         1 . A method for estimation of inner diameter of arterioles beneath the skin of measured body part, the method comprising:
 obtaining a first pressure wave signal from a first tissue volume beneath the skin of a part of a subject's body, containing blood vessels; wherein contribution in the first signal from artery-like blood vessels predominates over contribution from arteriole-like blood vessels;   obtaining a second pressure wave signal from a second tissue volume beneath the skin of the part of the subject's body, containing blood vessels; wherein contribution in the second signal from arteriole-like blood vessels predominates over contribution from artery-like blood vessels;   obtaining at least one concurrent heart rate value;   finding time delay values between the first signal and the second signal; and   using said at least one value of the time delay values and said at least one heart rate value to calculate an equivalent inner diameter of said arterioles.   
     
     
         2 . The method according to  claim 1 , further comprising assessing the presence or degree of damage to arterioles beneath the skin of measured body part:
 obtaining a first equivalent inner diameter of arterioles beneath the skin of a first part of a subject's body, containing possibly damaged blood vessels;   obtaining a second equivalent inner diameter of arterioles beneath the skin of a second part of a subject's body, containing possibly undamaged blood vessels;   comparing between the first and the second equivalent inner diameters in order to assess the presence or degree of damage to arterioles beneath the skin of said first part of said subject's body.   
     
     
         3 . The method according to  claim 1 , further comprising assessing the presence or degree of damage to arterioles beneath the skin of measured body part:
 obtaining a first equivalent inner diameter of arterioles beneath the skin of a first part of a subject's body, containing possibly damaged blood vessels;   obtaining a second equivalent inner diameter of arterioles beneath the skin of a second part of a subject's body, containing possibly less damaged blood vessels;   comparing between the first and the second equivalent inner diameters in order to assess the presence or degree of damage to arterioles beneath the skin of said first part of said subject's body.   
     
     
         4 . The method according to  claim 2 , wherein obtaining equivalent inner diameter of said arterioles from the subject's foot. 
     
     
         5 . The method according to  claim 3 , wherein obtaining equivalent inner diameter of said arterioles from the subject's foot. 
     
     
         6 . The method according to  claim 1 , wherein obtaining said first signal is from characteristic depth of more than 5 mm under the skin of the subject's body. 
     
     
         7 . The method according to  claim 1 , wherein obtaining said second is from characteristic depth of less than 5 mm under the skin of the subject's body. 
     
     
         8 . The method according to  claim 2 , wherein said first and second equivalent inner diameter of said arterioles are related to the same peripheral body part. 
     
     
         9 . The method according to  claim 2 , wherein assessing the presence or degree of damage beneath the skin of measured body part comprises one or more of a measure of damage to arterioles due to a pathological condition, a change in damage to arterioles over time, due to a pathological condition, and a difference in damage to arterioles in different parts of the body. 
     
     
         10 . The method according to  claim 2 , wherein assessing the presence or degree of damageto arterioles beneath the skin of measured body part comprises a difference in damage to arterioles in different parts of the body, and the method also includes assessing damage due to diabetes, from the difference in damage to arterioles between a part of the body damaged by diabetes, and an undamaged part of the body. 
     
     
         11 . The method according to  claim 1 , wherein a characteristic depth of said first tissue volume beneath the skin is at least 2 times as great as a characteristic depth of said second tissue volume beneath the skin. 
     
     
         12 . The method according to  claim 2 , also comprising:
 obtaining information about at least one physiologically influencing to subject over time parameter;   finding correlation between changes over time of said at least one parameter and changes over time in said assessing the presence or degree of damage of said arterioles.   
     
     
         13 . The method according to  claim 12 , wherein said parameter represents a substance entering to subject body. 
     
     
         14 . The method according to  claim 13 , wherein said substance is a pharmaceutical substance. 
     
     
         15 . The method according to  claim 12 , wherein said parameter is a behavioral parameter of the subject. 
     
     
         16 . The method according to  claim 15 , wherein said behavioral parameter represents a subject's activity. 
     
     
         17 . The method according to  claim 2 , wherein assessing the presence or degree of damage to arterioles beneath the skin of measured body part is further comprising:
 comparing an obtained value of equivalent inner diameter of arterioles to predefined threshold value;   indicating when said obtained diameter value is below or above said threshold value.   
     
     
         18 . The method s according to  claim 2 , wherein multiple assessings the presence or degree of damage to arterioles beneath the skin are done at once over a general part of the subject's body. 
     
     
         19 . The method according to  claim 18 , wherein said general part of the subject's body is a foot. 
     
     
         20 . The method according to  claim 1 , wherein:
 obtaining said first signal is done by a first light source and first detector, adapted to be placed a first distance apart on the skin of the subject's body, light from the first light source scattering from beneath the skin to the first detector to generate said first signal; and   obtaining said second signal is done by a second light source and a second light detector, one or both of them different respectively from the first light source and the first light detector, adapted to be placed a second distance apart, smaller than the first distance, light from the second light source scattering from beneath the skin to the second detector to generate the second signal.   
     
     
         21 . The method according to  claim 20 , wherein said distance between said first light source and detector is more than 5 mm. 
     
     
         22 . The method according to  claim 20 , wherein said distance between said second light source and detector is less than 5 mm.