Patent ID: 11937906
Assignee: ALIO, INC.
Field: Medical technology (Instruments)
Classification: CPC A | IPC A

Claim 2:
3. A system for monitoring blood flow metrics comprising:
a patch of a flexible substrate configured to attach to an area of skin over a blood vessel;
a plurality of light emitting diodes (LEDs) arranged on the substrate to form a R×C matrix and a row of C photodetectors (PDs) disposed on the substrate substantially in parallel with R rows of LEDs extending to form C columns substantially co-linear with each photodetector;
an optical signal interface mounted on the substrate and configured to drive each LED for an on-period and to input an optical signal at one of the photodetectors during the on-period to receive an intensity measurement for an optical path, OPrc, formed by LEDs in rows r=1 to R in columns c=1 to C and the photodetector receiving the optical signal;
a processing system comprising a memory for storing program instructions for execution by the processing system to:
determine an AC component, Irc,AC, and a DC component, Irc,DC, as a function of a plurality of intensity measurements, Irc, for each optical path, OPrc, over a period of time;
determine an AC-to-DC component ratio,, R
    
     r
     ,
     c
    
   
   =
   
    
     I
     
      rc
      ,
      AC
     
    
    
     I
     
      rc
      ,
      DC
     
    
   
  
  ,, for each optical path;

determine a plurality of ratio-of-ratios, RoR values, by dividing a first plurality of selected AC-to-DC component ratios by a second plurality of selected AC to DC component ratios; and
using at least a subset of the RoR values to determine a biological metric;

where the plurality of LEDs is a plurality of infrared (IR) LEDs emitting infrared light;
the memory of the processing system includes program instructions for execution by the processing system using at least the subset of RoR values to determine the biological metric, the biological metric is hematocrit concentration, Hct, determined using:
Hct=F(RoR′), where F is a transfer function that correlates a range of RoR values to a range of hematocrit concentration values based on reference hematocrit concentrations determined from a plurality of reference RoR values measured using a reference hematocrit measurement system, and where RoR′ is at least a subset of RoR values.