Pathlength enhancement of optical measurement of physiological blood parameters

Abstract

Systems and methods for measuring a physiological parameter of tissue in a patient are provided herein. In a first example, a method of measuring a physiological parameter of blood in a patient is provided. The method includes emitting at least two optical signals for propagation through tissue of the patient, detecting the optical signals after propagation, identifying propagation pathlengths of the optical signals, and identifying detected intensities of the optical signals. The method also includes processing at least the propagation pathlengths to scale the detected intensities for determination of a value of the physiological parameter.

What is claimed is: 
     
         1 . A method of operating a system for measuring a physiological parameter of blood in a patient, the method comprising:
 emitting at least one optical signal for propagation into tissue of the patient via a tissue interface assembly;   receiving the at least one optical signal after propagation;   identifying a propagation pathlength of the at least one optical signal; and   processing at least the propagation pathlength to determine a state of the tissue interface assembly on the tissue.   
     
     
         2 . The method of  claim 1 , wherein processing at least the propagation pathlength to determine the state of the tissue interface assembly on the tissue comprises comparing the propagation pathlength of the at least one optical signal to a pathlength range to determine an invalid application of the tissue interface assembly. 
     
     
         3 . The method of  claim 2 , wherein the invalid application of the tissue interface assembly comprises a gap between the tissue and the tissue interface assembly. 
     
     
         4 . The method of  claim 2 , wherein the invalid application of the tissue interface assembly comprises an application of the tissue interface assembly onto tissue perfused by blood below a perfusion threshold. 
     
     
         5 . The method of  claim 1 , wherein identifying the propagation pathlength of the at least one optical signal comprises determining a phase delay of the at least one optical signal and processing the phase delay with a propagation speed through the tissue for the at least one optical signal. 
     
     
         6 . The method of  claim 1 , wherein emitting the at least one optical signal for propagation into tissue of the patient via the tissue interface assembly comprises emitting the at least one optical signal through at least a gap between the tissue interface assembly and the tissue; and
 wherein processing at least the propagation pathlength to determine the state of the tissue interface assembly on the tissue comprises determining the state of the tissue interface assembly as including the gap between the tissue interface assembly and the tissue.   
     
     
         7 . The method of  claim 1 , wherein receiving the at least one optical signal after propagation comprises receiving the at least one optical signal after propagation through at least a gap between the tissue interface assembly and the tissue; and
 wherein processing at least the propagation pathlength to determine the state of the tissue interface assembly on the tissue comprises determining the state of the tissue interface assembly as including the gap between the tissue interface assembly and the tissue.   
     
     
         8 . The method of  claim 1 , further comprising:
 processing at least the propagation pathlength of the at least one optical signal and a detected intensity of the at least one optical signal to determine of a value of the physiological parameter when the state of the tissue interface assembly on the tissue indicates a proper application of the tissue interface assembly.   
     
     
         9 . A system for measuring a physiological parameter of blood in a patient, comprising:
 a tissue interface assembly configured to emit at least one optical signal for propagation into tissue of the patient and receive the at least one optical signal after propagation; and   a measurement system configured to identify a propagation pathlength of the at least one optical signal, and process at least the propagation pathlength to determine a state of the tissue interface assembly on the tissue.   
     
     
         10 . The system of  claim 9 , wherein the measurement system is configured to compare the propagation pathlength of the at least one optical signal to a pathlength range to determine an invalid application of the tissue interface assembly as the state of the tissue interface assembly on the tissue. 
     
     
         11 . The system of  claim 10 , wherein the invalid application of the tissue interface assembly comprises a gap between the tissue and the tissue interface assembly. 
     
     
         12 . The system of  claim 9 , wherein the tissue interface assembly is configured to emit the at least one optical signal through at least a gap between the tissue interface assembly and the tissue, and wherein the measurement system is configured to process at least the propagation pathlength to determine the state of the tissue interface assembly on the tissue as including the gap between the tissue interface assembly and the tissue. 
     
     
         13 . The system of  claim 9 , wherein the tissue interface assembly is configured to receive the at least one optical signal after propagation through at least a gap between the tissue interface assembly and the tissue, and wherein the measurement system is configured to process at least the propagation pathlength to determine the state of the tissue interface assembly on the tissue as including the gap between the tissue interface assembly and the tissue. 
     
     
         14 . The system of  claim 9 , comprising:
 the measurement system configured to process at least the propagation pathlength of the at least one optical signal and a detected intensity of the at least one optical signal to determine of a value of the physiological parameter when the state of the tissue interface assembly on the tissue indicates a proper application of the tissue interface assembly.