System for monitoring therapy during calibration

• US 5,752,504 A
• Filed: 12/13/1996
• Issued: 05/19/1998
• Est. Priority Date: 12/13/1996
• Status: Expired due to Term

• Current Assignee: Mallinckrodt Critical Care Finance Inc (Mallinckrodt plc), Mallinckrodt Pharma Ip Trading DAC (Mallinckrodt plc), Therakos, Inc (Mallinckrodt plc)
• Original Assignee: Ohmeda, Inc. (Linde Plc)
• Inventors: Bathe, Duncan P. L.
• Primary Examiner(s): Millin, Vincent
• Assistant Examiner(s): SRIVASTAVA, VIRENDRA KUMAR
• Application Number:
  US08/764,569
• Time in Patent Office: 522 Days
• Field of Search: 128/203.12, 128/203.14, 128/203.25, 128/204.21, 128/205.23, 128/202.22, 128/719, 128/203.24
• US Class Current: 128/203.12
• CPC Class Codes: A61M 16/12 by mixing different gases
• CPC Class Codes: A61M 2016/102 Measuring a parameter of the content of the delivered gas
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2202/0275 Nitric oxide [NO]

Abstract

A system for continuing the monitoring of certain gases delivered to a patient during the administration of nitric oxide to provide therapy to the patient. The nitric oxide is controlled by a electrically operated valve that is operated by means of an electrical signal from a CPU. At times when the various gas monitors are being calibrated, the normal alarms based upon those gas monitors are conventionally disabled during that calibration time. With the present invention, the electrical signal to the electrically operated valve is detected at the time the system goes into a calibration cycle and that detected electrical signal is used to establish limits such as a upper limit and a lower limit. Therefore, when the electrical signal to the valve is thereafter monitored and its value exceeds either of those limits, the overall nitric oxide delivery system will activate an alarm to alert the user of an abnormal condition. Thus an alarm system is present even when the various gas monitors are otherwise taken out of the system during their calibration.

Claims

1. A system for providing nitric oxide therapy to a patient, said system having a source of NO containing gas, a source of O₂ containing gas, at least one gas concentration monitor and an electrically operated valve for controlling the amount of NO containing gas administered to the patient, a therapy CPU providing an electrical signal for controlling the position of said electrically operated valve and for continuously monitoring the value of the electrical signal provided to said electrically operated valve, the improvement comprising a calibration system to effect the calibration of said at least one gas monitor, means to activate said calibration system whereby said at least one gas concentration monitor is inactivated from monitoring a gas, said means to activate said calibration system providing a signal to said therapy CPU to cause said CPU to detect the value of the electrical signal then being provided to said electrically operated valve by said therapy CPU, means to determine limits of change of said electrical signal with respect to said detected electrical signal value and means to continuously monitor said electrical signal to said electrically operated valve and to provide an alarm signal wherever said monitored electrical signal exceeds said determined limit.

2. A system for providing nitric oxide therapy to a patient as defined in claim 1, wherein said electrical signal is current.

3. A system for providing nitric oxide therapy to a patient as defined in claim 2 wherein said means to monitor said electrical signal monitors the average current over a predetermined period of time.

4. A system for providing nitric oxide therapy to a patient as defined in claim 1 wherein said means to determine said limits is a CPU.

5. A system for providing nitric oxide therapy to a patient as defined in claim 1 wherein said at least one gas monitor monitors NO.

6. A system for providing nitric oxide therapy to a patient as defined in claim 5 said at least one gas monitor monitors NO, O₂ and NO₂.

7. A system for providing nitric oxide therapy to a patient as defined in claim 1 wherein said limits are set as a high limit above said detected electrical signal and a low limit below said detected electrical signal.

8. A system for providing nitric oxide therapy to a patient as defined in claim 7 wherein said limits are set at about sixty percent above and below said detected electrical signal.

9. A method of providing nitric oxide therapy to a patient, said method comprising the steps of:

providing a source of NO containing gas and a source of O₂ containing gas,

providing at least one gas monitor for monitoring the concentration of a gas being provided to the patient

providing an electrically operated valve for controlling the mixing of NO and O2 to provide a predetermined amount of NO containing gas administered to the patient,

providing a therapy CPU having a controllable electrical signal output and communicating the electrical signal to said electrically operated valve,

controlling the position of said electrically operated valve by controlling the electrical signal output of the therapy CPU to said electrically operated valve,

continuously monitoring the value of the electrical signal output from the therapy CPU to said electrically operated valve

calibrating, at selected times, the said at least one gas monitor by inactivating the said at least one gas monitor and passing a calibration gas therethrough,

detecting the value of the electrical signal then being provided to the electrically operated valve by said therapy CPU when said at least one gas monitor is selected for calibration,

determining limits of change of the electrical signal with respect to the detected value of the electrical signal and continuously monitoring the electrical signal from the therapy CPU to the electrically operated valve, and

activating an alarm wherever the value of the electrical signal from the therapy CPU to the electrically operated valve exceeds the limits of change determined in the previous step.

10. A method of providing nitric oxide therapy to a patient as defined in claim 9 wherein said step of determining limits of change determines both a maximum positive change and a negative signal change with respect to the detected signal value.

11. A method of providing nitric oxide therapy to a patient as defined in claim 9 wherein said step of continuously monitoring the electrical signal value monitors current.

12. A method of providing nitric oxide therapy to a patient as defined in claim 11 wherein said step of continuously monitoring the electrical signal value monitors the average current over a predetermined period of time.