Dual pressure sensor continuous positive airway pressure (CPAP) therapy
Inventors
Ahmad, Samir S. • Baloa Welzien, Leonardo Alberto • Brambilla, Enrico
Assignees
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Publication Number
US-11191914-B2
Publication Date
2021-12-07
Expiration Date
Abstract
A continuous positive airway pressure (CPAP) apparatus for respiratory assistance of a patient is disclosed. There is a blower having an output connectible to a ventilation mask wearable by the patient. A first pressure sensor measures blower pressure at the output of the blower, and a second pressure sensor that is connectible to the ventilation mask measures mask pressure therein. A pressure controller is connected to the first pressure sensor and the second pressure sensor, and a patient inspiratory phase and a patient expiratory phase is be detectable by the pressure controller to regulate therapeutic airflow delivered to the patient based upon pressure differentials between the mask pressure and the blower pressure.
Core Innovation
The disclosed invention is a respiratory assistance device that includes a patient ventilation interface with a ventilation mask and a piloted exhalation valve, and a ventilation source coupled to the patient ventilation interface via a first conduit. The device measures a source pressure at the output of the ventilation source with a first pressure sensor and measures a patient interface pressure in the patient ventilation interface with a second pressure sensor. A pressure controller compares a pressure difference ΔP between the source pressure and the patient interface pressure to determine patient inspiratory and expiratory phases.
To detect the patient respiratory state, the pressure controller defines a trigger limit as an average of the pressure difference ΔP plus a trigger constant, and defines a cycle limit as a maximum of the pressure difference ΔP multiplied by a cycle constant. Therapeutic airflow is delivered to the patient during the detected patient inspiratory phase, and exhausted through the piloted exhalation valve during the detected patient expiratory phase. The corresponding apparatus and method perform respiratory assistance by evaluating a patient respiratory state as an inspiration state or an expiration state using the same ΔP-based trigger limit and cycle limit definitions.
The disclosed system further relates the piloted exhalation valve operation to the ΔP behavior, including valve opening behavior to ambient pressure when ΔP is lower than a predefined threshold, and valve open conditions tied to an approximately zero-to-negative pressure difference. Leak compensation is represented through a leak constant defined as an average of the pressure difference ΔP over one or more patient breathing cycles, and the trigger and cycle limits are parameterized using the leak constant along with trigger and cycle constants. Closed-loop control is described using inner and outer PID controllers in communication with source-pressure and patient-interface pressure targets, including multi-loop control for maintaining a clinician-set CPAP pressure with phase-dependent targets.
Claims Coverage
The independent claims are 1, 12, and 16. Each independent claim includes a ΔP-based respiratory phase detection using trigger and cycle limits derived from average and maximum of ΔP, and delivery of therapeutic airflow selectively in response to the detected inspiration/expiration state (and in claim 1 explicitly tied to exhausting through a piloted exhalation valve).
ΔP-based inspiratory/expiratory phase detection with trigger and cycle limits
A pressure controller detects a patient inspiratory phase and a patient expiratory phase by comparing a pressure difference ΔP between a source pressure and a patient interface pressure to a trigger limit defined as an average of the pressure difference ΔP plus a trigger constant and a cycle limit defined as a maximum of the pressure difference ΔP multiplied by a cycle constant.
Therapeutic airflow delivery during inspiration and exhaust through a piloted exhalation valve during expiration
Therapeutic airflow is delivered to the patient during the detected patient inspiratory phase and exhausted through the piloted exhalation valve during the detected patient expiratory phase.
Trigger-limit and cycle-limit respiratory-state evaluation to selectively apply therapeutic gas flow
A method evaluates a patient respiratory state by comparing a pressure difference ΔP to a trigger limit defined as an average of the pressure difference ΔP plus a trigger constant and a cycle limit defined as a maximum of the pressure difference ΔP multiplied by a cycle constant, the patient respiratory state being one of an inspiration state and an expiration state.
Selective application of therapeutic gas flow based on the evaluated respiratory state
The method selectively applies a quantity of the therapeutic gas flow through the first conduit to the patient ventilation interface in response to the evaluated patient respiratory state, the quantity corresponding to a received first therapeutic pressure value.
Across independent claims, the core inventive coverage centers on computing a ΔP between source pressure and patient interface pressure, deriving a trigger limit from an average of ΔP plus a trigger constant and a cycle limit from a maximum of ΔP multiplied by a cycle constant, evaluating inspiration/expiration, and applying therapeutic airflow accordingly, with claim 1 also explicitly exhausting via the piloted exhalation valve during expiration.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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