Body-worn pulse oximeter

Inventors

Moon, Jim • McCOMBIE, Devin • Dhillon, Marshal • Banet, Matthew

Assignees

Sotera Wireless Inc

Abstract

The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient's thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.

Core Innovation

A system for monitoring a patient is described that includes an oximetry sensor, an ECG system, an oscillometric blood pressure monitoring system, multiple motion sensors, and a processing unit worn on the patient’s body. The oximetry sensor includes a photodetector and first and second light sources, and the photodetector is configured to mate to a thumb at the base so that first and second signals are primarily measured from the princeps pollicis artery. The ECG system includes a differential amplifier circuit operably connected to at least two electrodes to generate an ECG signal and includes a first motion sensor to generate a first motion signal.

The oscillometric blood pressure monitoring system includes a pump and a cuff configured to be positioned on the patient’s upper arm to generate an oscillometric blood pressure signal. Additional motion sensors are configured to be positioned on the patient’s arm above the elbow and at the wrist to generate second and third motion signals. The processing unit is operably connected to the oximetry sensor, the ECG system, the oscillometric blood pressure monitoring system, the second motion sensor, and the third motion sensor, and processes signals to determine oxygen saturation, derive a blood pressure calibration value compensating for hydrostatic forces due to arm height, and determine torso orientation with respect to gravity.

The processing unit further uses the ECG signal, the oscillometric blood pressure signal, and at least one of the first and second signals to determine a patient specific relationship between mean arterial blood pressure and pulse transit time. Using the blood pressure calibration value, the patient’s torso orientation, the patient specific relationship, the ECG signal, and at least one of the first and second signals, the processing unit determines a blood pressure measurement for the patient. The overall approach supports continuous, noninvasive monitoring for ambulatory patients using motion-aware processing and sensor positioning concepts tied to the princeps pollicis artery and torso orientation.

Claims Coverage

Only one independent claim is provided (clm-00001). It includes a combination of oximetry, ECG, oscillometric blood pressure sensing, multiple motion sensors, and processing logic that jointly compute oxygen saturation and compensate for motion and physiological positioning to determine a patient-specific blood pressure measurement. The inventive features center on thumb-base oximetry primarily measuring from the princeps pollicis artery and using coordinated motion sensors plus torso orientation and an ECG/oscillometric-derived patient-specific mean arterial blood pressure versus pulse transit time relationship for blood pressure measurement.

The provided independent claim (clm-00001) covers a wearable patient monitoring system that combines thumb-base oximetry primarily measuring from the princeps pollicis artery with an ECG chest housing and an oscillometric upper-arm cuff system. It further relies on multiple motion sensors to compute oxygen saturation, compensate hydrostatic forces via arm-height-related calibration, determine torso orientation versus gravity, and establish a patient specific relationship between mean arterial blood pressure and pulse transit time using ECG and oscillometric blood pressure signals. The final blood pressure measurement is then determined using the calibration value, torso orientation, the patient-specific relationship, and the relevant signals.

Stated Advantages

Documented Applications

No documented applications found