Smart oxygenation system employing automatic control using SpO2-to-FiO2 ratio
Inventors
Kinsky, Michael • Branson, Rich • Kramer, George • Khan, Muzna • Johanningman, Jay • Salinas, Jose • Liu, Nehemiah
Assignees
University of Cincinnati • University of Texas System • United States Department of the Army
Publication Number
US-10589045-B2
Publication Date
2020-03-17
Expiration Date
2037-10-04
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Abstract
A system for assessing lung function in a patient is enclosed. The oxygen delivery system in the system (e.g., a ventilator or portable standalone system) preferably includes an oximeter sensor for receiving SpO2 from a patient. The assessing lung function in a patient includes an FiO2 adjust algorithm operable in logic circuitry in the ventilator that can control an oxygen fraction FiO2 provided to the patient in a closed loop fashion. In a preferred example, the algorithm controls FiO2 using the SpO2, but also displays a ratio of SpO2-to FiO2 (S/CLCF) as a function of time. One or more S/CLCF ratio threshold may be used to allow the clinician and/or the algorithm to understand a degree of lung injury, and to allow the algorithm to adjust FiO2 appropriately. Preferably, the algorithm keeps SpO2 to a range of 88-95%.
Core Innovation
The invention disclosed is a system for assessing lung function in a patient by automatically controlling the fraction of inspired oxygen (FiO2) provided through an oxygen delivery system such as a ventilator or portable standalone device. The system includes an oximeter sensor to receive blood oxygen saturation (SpO2) and an algorithm operable in logic circuitry that uses SpO2 and the ratio of SpO2 to FiO2 (S/CLCF) to control FiO2 in a closed loop fashion. The display shows the S/CLCF ratio as a function of time along with SpO2 and optionally the rate of change of the S/CLCF ratio, assisting clinicians in managing oxygenation therapy.
The problem addressed by the invention arises from current ventilation practices that often maintain SpO2 at excessively high levels (above 95%), which can mask lung function changes because SpO2 plateaus beyond that range and does not accurately reflect arterial oxygen partial pressure (PaO2). Prior methods rely on invasive PaO2 measurements or use SpO2 alone without accounting for the ratio to FiO2 or its trends over time, limiting timely detection of lung injury severity or the need for adjustment in oxygen support.
This invention improves upon prior closed loop control systems by integrating the S/CLCF ratio and its rate of change with SpO2 to refine FiO2 adjustments, thus targeting a conservative SpO2 range (88-95%) that corresponds to a sensitive segment of the oxygen dissociation curve. The system is capable of issuing alerts when the S/CLCF ratio crosses predefined thresholds indicating severity of lung injury (normal to severe ARDS), enabling proactive and automated escalation or de-escalation of oxygen therapy and potentially other ventilation parameters.
Claims Coverage
The patent contains two independent claims covering a system for oxygenation control and a method for assessing lung function with adaptive FiO2 adjustment.
Closed loop FiO2 adjustment using SpO2 and S/CLCF ratio
A system that continually measures patient SpO2, calculates the SpO2-to-FiO2 ratio (S/CLCF), and uses an algorithm to adjust FiO2 in a closed loop manner to maintain SpO2 within a desired range while displaying the S/CLCF ratio over time.
Graphical display of oxygenation parameters over time
The system includes a display that shows the S/CLCF ratio as a function of time, and may also display measured SpO2 and the rate of change of the S/CLCF ratio, aiding clinicians in interpreting lung function and oxygenation status.
Automatic alert based on S/CLCF thresholds
The logic circuitry issues an alert when the S/CLCF ratio falls below a predetermined threshold (e.g., 250), signaling potential lung impairment requiring clinical attention or escalation.
Method for automated adjustment and monitoring of FiO2 using SpO2 and S/CLCF ratio
A method of providing oxygen to a patient that calculates and continuously monitors SpO2 and S/CLCF ratio, automatically adjusting FiO2 based on these values to maintain oxygen saturation in a target range and graphing these parameters over time for clinical use.
The inventive features disclose a system and method for closed loop oxygen delivery control that integrates SpO2, the SpO2-to-FiO2 ratio, and its rate of change to maintain oxygenation within a desired range, provide visual feedback on respiratory status, and generate alerts for lung injury severity, thus enhancing clinical management of respiratory support.
Stated Advantages
Enables automatic closed loop control of FiO2 to maintain SpO2 within a conservative and clinically recommended range (88-95%).
Provides real-time monitoring and display of S/CLCF ratio which serves as a non-invasive indicator of lung injury severity and respiratory function over time.
Allows earlier detection of deterioration or improvement in lung function compared to SpO2 alone, facilitating timely clinical decisions and intervention.
Reduces risks associated with excessive oxygen delivery such as hyperoxia by avoiding unnecessarily high FiO2 levels.
Supports escalation and de-escalation of oxygen therapy and ventilation parameters automatically or with clinician alerts, improving personalized patient care.
Documented Applications
Treatment and monitoring of patients with acute respiratory distress syndrome (ARDS).
Use for patients with chronic obstructive pulmonary disease (COPD).
Care of neonate patients requiring controlled oxygenation.
Management of patients suffering traumatic injury, including military field use or mass casualty situations.
Use in emergency triage settings such as emergency rooms.
Monitoring patients after extubation to detect extubation failure.
Post-anesthesia care unit (PACU) applications for anesthetized patients.
Use in portable oxygen delivery systems for home oxygen therapy.
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