Systems and methods for compensating long term sensitivity drift of electrochemical gas sensors exposed to nitric oxide
Inventors
Tolmie, Craig R. • Milsap, Jeff • Acker, Jaron M.
Assignees
Mallinckrodt Pharma IP Trading DAC • Therakos Inc • INO Therapeutics LLC • Mallinckrodt Critical Care Finance Inc
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Publication Number
US-9974910-B2
Publication Date
2018-05-22
Expiration Date
Abstract
Described are systems and methods for compensating long term sensitivity drift of catalytic type electrochemical gas sensors used in systems for delivering therapeutic nitric oxide (NO) gas to a patient by compensating for drift that may be specific to the sensors atypical use in systems for delivering therapeutic nitric oxide gas to a patient. The long term sensitivity drift of catalytic type electrochemical gas sensors may be addressed using calibration schedules, which can factor in the absolute change in set dose of NO being delivered to the patient that can drive one or more baseline calibrations. The calibration schedules can be used to reduce the amount of times the sensor goes offline.
Core Innovation
The disclosed invention compensates nitric oxide (NO) sensor drift associated with a nitric oxide delivery system by using a calibration line correlated to nitric oxide concentrations and a calibration schedule providing times for performing baseline calibrations. The calibration line and schedule are stored in a non-transitory computer-readable memory of a nitric oxide delivery system or a system controller. Baseline calibrations are performed in response to a change in set dose and include exposing the nitric oxide sensor to a zero concentration of nitric oxide, or to a gas having a zero concentration of nitric oxide.
During operation, nitric oxide is supplied to an inspiratory flow of a patient breathing circuit according to a set dosage, and output values or measurements from the nitric oxide sensor are monitored and/or continuously collected as representing therapeutic gas concentration in the inspiratory flow. The method determines an actual output value during a baseline calibration performed according to the calibration schedule, and then augments expected values correlated to nitric oxide concentrations to include the difference between the actual output value and the expected output value. In related claim language, a calibration line is adjusted according to a detected drift between a baseline and the concentration measured during exposure to a zero concentration of nitric oxide.
The disclosure further addresses when and how calibration is performed by identifying that a calibration should be performed according to the calibration schedule, while postponing or delaying baseline calibration under alarm/user interaction conditions and when an interfering gas is detected or when sensor output is out of a threshold range. Alternative baseline exposure is described as exposing the nitric oxide sensor to ambient air as a gas having a zero concentration of nitric oxide, and the calibration line is then adjusted based on the measured concentration during that exposure. The disclosed approach resumes continuous collecting after performing the calibration.
Claims Coverage
The provided material includes three independent claims. Each independent claim centers on using a stored calibration schedule and calibration line, exposing the nitric oxide sensor to a zero concentration of nitric oxide during scheduled calibration, and adjusting the calibration line or adjusted measurements to compensate detected drift, with claim-dependent refinements adding conditional postponement and/or specified zero-reference gas sources.
Scheduled baseline calibrations in response to set dose change with zero nitric oxide exposure and drift-based augmentation
Storing a calibration line correlating expected output values from a nitric oxide sensor to nitric oxide concentrations and a calibration schedule providing times for performing a plurality of baseline calibrations, the baseline calibrations being performed in response to a set dose change and including exposing the nitric oxide sensor to a zero concentration of nitric oxide; supplying nitric oxide according to a set dosage into an inspiratory flow of a patient breathing circuit; monitoring output values; determining an actual output value during a baseline calibration in accordance with the calibration schedule; and augmenting the expected values correlated to nitric oxide concentrations to include the difference between the actual output value and the expected output value.
Calibration schedule identification with zero concentration gas exposure and adjustment of calibration line based on detected drift
Storing a calibration schedule and a calibration line in a non-transitory computer-readable memory of a system controller; supplying nitric oxide to a patient breathing circuit according to a set dosage; continuously monitoring output values correlated to concentration of nitric oxide in the breathing circuit; identifying that a nitric oxide sensor calibration should be performed according to the calibration schedule; exposing the nitric oxide sensor to a flow of a gas having a zero concentration of nitric oxide; measuring the concentration detected during exposure; and adjusting the calibration line according to a detected drift between a baseline and the concentration measured when exposed to the gas having a zero concentration of nitric oxide.
Adjusted measurements presentation using a stored calibration line and zero-reference exposure at scheduled calibration
Storing a calibration schedule and a calibration line in a non-transitory computer-readable memory of a system controller, wherein the calibration line has a baseline associated with a zero concentration of nitric oxide; receiving and delivering nitric oxide according to a set dosage to a breathing circuit; continuously collecting nitric oxide sensor measurements of concentration in the breathing circuit; adjusting the measurements according to the calibration line and presenting a representation of the adjusted measurements on a display; identifying that a calibration should be performed according to the calibration schedule; performing a calibration by exposing the sensor to a gas having a zero concentration of nitric oxide; measuring the detected concentration during exposure; and adjusting the calibration line according to the difference between the baseline and the measured concentration when exposed.
Across the independent claims, the central inventive coverage is compensating nitric oxide sensor drift by combining stored calibration schedule and calibration line information with scheduled baseline calibrations that expose the sensor to a zero concentration of nitric oxide and then update expected values, the calibration line, or adjusted measurements based on detected differences between baseline or expected values and measured zero-reference sensor output. Additional coverage includes conditions for performing or postponing calibration and specifying a zero-reference exposure source such as ambient air.
Stated Advantages
Compensates nitric oxide sensor drift in a nitric oxide delivery system.
Augments expected values correlated to nitric oxide concentrations to include detected differences between actual and expected output during baseline calibration.
Adjusts calibration line and/or continuously collected measurements to present a representation of adjusted measurements on a display.
Uses a calibration schedule providing times for performing baseline calibrations in response to a set dose change.
Performs or delays calibration based on identified conditions such as alarm conditions and interfering gas detection.
Documented Applications
Nitric oxide delivery using a patient breathing circuit in which NO sensor drift is compensated via calibration schedules and baseline calibration exposures.
Presenting adjusted nitric oxide sensor measurements on a display in a nitric oxide delivery system during continuous collecting and scheduled calibration.
Interested in licensing this patent?