Subcutaneous hemodynamic monitoring devices, systems and methods
An implantable sensor system using one or more sensor implants comprised of micro-electrical mechanical system (MEMS) sensors for the accurate and continuous measurement of physiological hemodynamic signals such as diastolic and systolic blood pressure. Sensor implants are configured to be subcutaneously injected to a placement site adjacent a blood vessel. In some embodiments, sensors comprise micromachined ultrasonic transducers.
1 . A hemodynamic sensor system, comprising:
a sensor implant comprising a housing configured along a housing axis to be positioned subcutaneously in tissue adjacent a target blood vessel in a patient, the sensor implant further comprising within the housing at least two ultrasound transducers positioned along said housing axis with a known distance between the ultrasound sensor transducers, said ultrasound transducers configured to produce signals indicative of a change in diameter of the target blood vessel at spaced apart locations in response to pulsations of the cardiac cycle; and
at least one processor and at least one memory in operative communication with the at least one processor, the memory containing an instruction set comprising machine-executable instructions that, when executed by the at least one processor determine a pulse wave velocity for the target blood vessel based in part on said signals indicative of changes in diameter at the spaced apart locations, the known distance between the ultrasound transducers and a time difference between said signals indicative of a change in diameter of the target blood vessel.
2 . The system of claim 1 , wherein the instruction set contained in the at least one memory further comprises machine-executable instructions that, when executed by the at least one processor determine patient blood pressure based on the determined pulse wave velocity.
3 . The system of claim 2 , wherein the signals produced by the ultrasound transducers comprise signals indicative of:
signals representing the target blood vessel near wall outer surface, near wall inner surface, far wall inner surface, and far wall outer surface
a change in diameter of the target blood vessel in response to a cardiac pulse at a first of said at least two ultrasound transducers; and
a change in diameter of the target blood vessel in response to the cardiac pulse at a second of said at least two ultrasound transducers.
4 . The system of claim 3 , wherein said instruction set further comprise machine-executable instructions that, when executed by the at least one processor determine target blood vessel wall thickness or stiffness.
5 . The system of claim 2 , further comprising:
a communication module communicating with the at least one sensor to transmit one or more signals comprising signals representative of detected physiological parameters to an external receiver; and
an external, local controller configured to (1) wirelessly receive signals transmitted by the communication module, and (2) at least one of further process said signals or relay said signals to a network.
6 . The system of claim 5 , wherein said at least one processor, said at least one memory and instruction set resides at least in part in a network-based computing network.
7 . The system of claim 5 , wherein said at least one processor, said at least one memory and instruction set resides at least in part in the local control module.
8 . The system of claim 5 , wherein said at least one processor, said at least one memory and instruction set resides at least in part within the sensor implant housing.
9 . The system of claim 1 , wherein said housing further comprises ultrasound transmissive portions aligned with each said ultrasound transducer.
10 . The system of claim 1 , wherein the sensor implant further comprises:
at least one accelerometer disposed in the housing configured to detect movement or changes in position of the patient and produce signals representative of said movement or changes in position, and wherein said at least one processor comprises a controller disposed in the housing configured to detect timing of and process the signals from the ultrasound transducers and the at least one accelerometer to produce a data stream from which pulse wave velocity for the target blood vessel and patient blood pressure can be calculated;
a communication module disposed in the housing configured to transmit said data stream to an external receiver; and
a power source disposed in the housing operatively connected to power the sensor implant.
11 . The system of claim 10 , wherein said ultrasound transducers are configured to focus ultrasound signals on the target blood vessel at a detection distance of about 2 mm to about 50 mm from said blood vessel.
12 . The system of claim 10 , further comprising an external controller configured to (1) wirelessly receive the data stream transmitted by the communications module and (2) at least one of calculate pulse wave velocity and patient blood pressure based on the data stream or transmit the data stream to networked computing device configured to calculate the pulse wave velocity and patient blood pressure based on said data stream.
13 . The system of claim 1 , wherein the sensor implant and at least two transducers are configured to be positioned within tissue adjacent to the target blood vessel at a distance from the target blood vessel.
14 . The system of claim 13 , wherein the sensor implant and at least two transducers are configured to be positioned within tissue adjacent to the target blood vessel at a distance of about 2 mm to about 50 mm from the outer wall of the target blood vessel.
15 . The system of claim 1 , wherein said at least two ultrasound transducers comprise sensor elements of a single array.
16 . The system of claim 1 , wherein said at least two ultrasound transducers comprise sensor elements in at least two sensor arrays.
17 . A hemodynamic sensor system, comprising:
a sensor implant comprising a housing configured along a housing axis to be positioned subcutaneously in tissue adjacent a target blood vessel in a patient, the sensor implant further comprising within the housing at least two ultrasound transducers positioned along said housing axis with a known distance between the ultrasound sensor transducers, said ultrasound transducers configured to focus ultrasound signals on the target blood vessel at a detection distance of about 2 mm to about 50 mm from said blood vessel and to produce signals indicative of a change in diameter of the target blood vessel at spaced apart locations in response to pulsations of the cardiac cycle;
a controller disposed in the housing configured to detect timing of and process the signals from the ultrasound transducers and to produce a data stream based on said signals from which pulse wave velocity for the target blood vessel and patient blood pressure can be calculated;
a transceiver disposed in the housing configured to transmit said data stream to an external receiver; and
a power source disposed in the housing operatively connected to power the sensor implant.
18 . The system of claim 17 , further comprising an external controller configured to (1) wirelessly receive the data stream transmitted by the communications module and (2) at least one of calculate pulse wave velocity and patient blood pressure based on the data stream or transmit the data stream to networked computing device configured to calculate the pulse wave velocity and patient blood pressure based on said data stream.
19 . The system of claim 18 , wherein at least one of the external controller or networked computing device comprises at least one processor and at least one memory in operative communication with the at least one processor, wherein the memory contains an instruction set comprising machine-executable instructions that, when executed by the at least one processor determine a pulse wave velocity for the target blood vessel based on the received data stream.
20 . The system of claim 17 , further comprising at least one accelerometer disposed in the housing configured to detect movement or changes in position of the patient and produce accelerometer signals representative of said movement or changes in position, and wherein said controller is further configured to process said accelerometer signals as a part of the produced data stream.