Blood flow measuring apparatus and method

Claim 1

A portable apparatus for determining the rate of blood flow in a limb comprising, in combination: a. first occluding means mountable on the limb for occluding blood flow to the extremity of the limb distal to where said first occluding means is mounted; b. second occluding means mountable on the limb proximal of said first occluding means for occluding venous outflow from the limb distal to where said second occluding means is mounted while allowing arterial inflow to continue substantially unimpeded; c. occluding control means connected to said first and second occluding means and adapted to cause said occluding means to occlude in the manner stated; d. measuring means mountable on the limb between said first and second occluding means and productive of an electrical signal responsive to the change in circumference of said limb between said occluding means when so mounted and when said occluding means are occluding in the respective manner stated; e. electrical analyzing circuit means connected to said measuring means, said analyzing circuit means including logic circuit means for receiving and performing arithmetic operations upon electrical signal inputs, said analyzing circuit means further including means to generate and transmit to said logic circuit means electrical signal inputs representative of the circumference of the limb at the point of application of said measuring means, and representative of a change in circumference of known amount, said logic circuit being adapted to receive and combine said electrical signal from said measuring means over a predetermined time period with said electrical inputs and to convert said electrical signal and inputs to a numerical form representing the rate of blood flow required to produce such change in such period of time; and f. portable housing means mounting said analyzing circuit and occluding control means and mounting connecting means for connecting said first and second occluding means and said measuring means to the appropriate said analyzing circuit and occluding control means.

Claim 7

The method of obtaining rate of blood flow in a limb, comprising the steps: a. with the limb circulation occluded, occlude the venous outflow from the said limb; b. electrically measure over a specified time the change in limb circumference occasioned by said venous occlusion; c. electrically combine the signal representative of the percentage change in circumference with a signal representative of a change in circumference of known amount and with a signal representative of the resting circumference of the limb; and d. electrically convert said combined signals to the percentage change in volume per minute to obtain a measure of limb blood flow.

Claim 8

The method of obtaining rate of blood flow in a limb, comprising the steps: a. with the limb circulation occluded, occlude the venous outflow from the said limb; b. electrically measure over a specified time the change in limb circumference occasioned by said venous occlusion; c. electrically combine the signal representative of the percentage change in circumference with a signal representative of a change in circumference of known amount and with a signal representative of the resting circumference of the limb; and d. electrically convert said combined signals to the percentage change in volume per minute to obtain a measure of limb blood flow.