Systems and Methods for Compensating Long Term Sensitivity Drift of Electrochemical Gas Sensors Exposed to Nitric Oxide

Patent metadata

Field	Value
Publication number	US-2017014591-A1
Application number	US-201615277253-A
Country	US
Kind code	A1
Filing date	Sep 28, 2016
Priority date	Feb 19, 2014
Publication date	Jan 19, 2017
Grant 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. In at least some instances, the long term sensitivity drift of catalytic type electrochemical gas sensors can 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 reduce the amount of times the sensor goes offline. Systems and methods described may factor in in actions occurring at the delivery system and/or aspects of the surrounding environment, prior to performing a baseline calibration, and may postpone the calibration and/or rejected using the sensor's output for the calibration.

First claim

What is claimed is:

1 . A method for compensating for sensor drift in a sensor, the method comprising:
monitoring a patient intake of therapeutic gas with a sensor; storing in memory a baseline calibration value, a slope associated with the baseline calibration value, and a calibration schedule, wherein the slope represents a plurality of correlated values of therapeutic gas dosage concentrations to values output from the sensor; delivering, via a therapeutic gas delivery device, a predetermined dosage of therapeutic gas to the patient; measuring a concentration of therapeutic gas from the delivered predetermined dosage; retrieving, from memory, the baseline calibration value and slope; performing a calibration according to the calibration schedule, wherein the calibration includes exposing the sensor to a zero concentration of the therapeutic gas and adjusting the baseline calibration value according to a sensor output value during the calibration; determining an actual concentration of therapeutic gas delivered in the predetermined dosage to compensate for sensor drift by adjusting the value of the measured concentration based on the adjusted baseline value and the slope.

2 . The method of claim 1 wherein the therapeutic gas is nitric oxide.

3 . The method of claim 2 wherein the calibrating the sensor to a zero concentration of therapeutic gas includes exposing the sensor to ambient air for a predetermined amount of time.

4 . The method of claim 3 wherein the predetermined amount of time is 3-5 minutes.

5 . The method of claim 1 wherein the sensor is re-calibrated according to the calibration schedule.

6 . The method of claim 5 wherein the calibration schedule is postponed in response to a current alarm condition.

7 . The method of claim 5 wherein the calibration schedule is postponed if an alarm condition occurs within a predetermined period of time before the scheduled calibration.

8 . The method of claim 5 wherein the calibration schedule includes a first calibration at a first time interval and a second calibration at a second interval.

9 . A method for compensating for sensor drift in a sensor, the method comprising:
monitoring a patient intake of therapeutic gas with a sensor, the monitoring including a determination of therapeutic gas concentration being delivered to the patient through a breathing circuit; storing in memory:
a baseline calibration value corresponding to a known output concentration of therapeutic gas at a specified output current,
a slope associated with the baseline calibration value, the slope corresponding to a correlation between measured output current at specific output concentrations, and
a calibration schedule;
delivering, via a therapeutic gas delivery device, a predetermined dosage of therapeutic gas to the patient; measuring a concentration of therapeutic gas from the delivered predetermined dosage, wherein the measuring includes determining the output current of delivered therapeutic gas; retrieving, from memory, the baseline calibration value and slope; and performing a calibration according to the calibration schedule, wherein the calibration includes exposing the sensor to a zero concentration of the therapeutic gas and adjusting the baseline calibration value according to a sensor output value during the calibration; determining an actual concentration of therapeutic gas delivered in the predetermined dosage to compensate for sensor drift by adjusting the value of the measured concentration based on the adjusted baseline value and the slope.

10 . The method of claim 9 wherein the therapeutic gas is nitric oxide.

11 . The method of claim 10 wherein the measuring comprises continuous measuring of therapeutic gas concentration.

12 . The method of claim 11 wherein the calibration schedule comprises a set of values representing intended intervals between interruptions of continuous measuring of therapeutic gas concentrations.

13 . The method of claim 12 , wherein the calibration schedule includes at least two variable intervals.

14 . The method of claim 13 , wherein in response to change in the concentration of the delivered predetermined dosage of nitric oxide, the calibration schedule adjusts from a first interval to a second interval.

15 . The method of claim 9 wherein the adjusting the value of the measured concentration based on the adjusted baseline value and the slope further comprises generating a calibration line based on the slope and the adjusted baseline value.

16 . The method of claim 15 wherein the calibration line corresponds to a plurality of actual output concentration values of therapeutic gas at a specified output current.

17 . A method for compensating for sensor drift in a sensor, the method comprising:
monitoring a patient intake of therapeutic gas with a sensor, the monitoring including a determination of therapeutic gas concentration being delivered to the patient through a breathing circuit; storing in memory:
a baseline calibration value corresponding to a known output concentration of therapeutic gas at a specified output current,
a slope associated with the baseline calibration value, the slope corresponding to a correlation between measured output current at specific output concentrations, and
a calibration schedule;
delivering, via a therapeutic gas delivery device, a first predetermined dosage of therapeutic gas to the patient; measuring a concentration of therapeutic gas from the delivered first predetermined dosage, wherein the measuring includes determining the output current of delivered therapeutic gas; retrieving, from memory, the baseline calibration value and slope; performing a calibration according to the calibration schedule, wherein the calibration includes exposing the sensor to a zero concentration of the therapeutic gas and adjusting the baseline calibration value according to a sensor output value during the calibration; determining an actual concentration of therapeutic gas delivered in the predetermined dosage to compensate for sensor drift by adjusting the value of the measured concentration based on the adjusted baseline value and the slope; stopping delivery of the first predetermined dosage of therapeutic gas; delivering a second predetermined dosage of therapeutic gas, the second predetermined dosage different from the first predetermined dosage; and in response to the delivering of the second predetermined dosage, adjusting the calibration schedule to perform the calibration.

18 . The method of claim 17 wherein the therapeutic gas is nitric oxide.

19 . The method of claim 17 wherein the calibration schedule is adjusted to perform the calibration after a period of 3 hours, 6 hours and 12 hours after delivering the second predetermined dosage.

20 . The method of claim 17 wherein the calibration is adjusted in response to an alarm condition.

Assignees

• Mallinckrodt Hospital Products Ip Ltd

Inventors

• Tolmie Craig R
• Milsap Jeff
• Acker Jaron M

Classifications

• A61M2202/0275

  Nitric oxide [NO] · CPC title

• A61M2205/33

  Controlling, regulating or measuring · CPC title

• A61M16/024

  including calculation means, e.g. using a processor · CPC title

• A61M2205/502

  User interfaces, e.g. screens or keyboards · CPC title

• A61M16/085

  Gas sampling · CPC title