Systems and method for delivery of therapeutic gas to patients in need thereof using enhanced breathing circuit gas (BCG) flow measurement

1. A method of administering therapeutic gas to a patient, the method comprising:

measuring a flow direction of a breathing gas through and/or in fluid communication with a breathing circuit affiliated with a ventilator, wherein flow is in a forward direction when flowing from the ventilator towards the patient and in a reverse direction when flowing from the patient towards the ventilator;

determining the breathing gas flow is in the forward direction, opening a control valve in communication with a flow of a breathing gas, and delivering the therapeutic gas into the breathing gas;

determining the breathing gas flow is in the reverse direction, closing the control valve, and ceasing delivery of the therapeutic gas into the breathing gas;

determining a volume of reverse flow;

determining the breathing gas resumed flow in the forward direction

determining a volume of resumed forward flow; and

compensating for flow in the reverse direction by opening the control valve to resume delivery of the therapeutic gas into the breathing gas after the volume of forward flow is at least equal to the volume of reverse flow.

2. The method of claim 1 , wherein compensating for the flow in the reverse direction ensures that a desired dose of therapeutic gas is not over delivered, overdosed, under delivered, and/or under dosed.

3. The method of claim 1 , wherein compensating for the flow in the reverse direction comprises comparing the volume of the flow in the reverse direction to a dead space volume and not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling the lesser of (i) the reverse flow measured or (ii) the dead space volume.

4. The method of claim 3 , wherein the dead space volume is entered by a user and/or is communicated from the ventilator; and the method optionally further comprises providing instructions to a user to add a segment of breathing circuit between the patient and at least one bi-directional breathing circuit gas (BCG) flow sensor for measuring the flow of the breathing circuit gas.

5. The method of claim 1 , further comprising:

receiving information indicative of and/or determining a ventilator type.

6. The method of claim 5 , wherein receiving and/or determining the ventilator type comprises receiving and/or determining whether or not the ventilator is a BiPAP ventilator and/or affiliated with single limb breathing circuit; and compensating for at least a portion of the flow in the reverse direction is based on the receiving and/or determining whether or not the ventilator is a BiPAP ventilator and/or affiliated with single limb breathing circuit.

7. The method of claim 6 , wherein if the ventilator is a BiPAP ventilator and/or affiliated with single limb breathing circuit, compensating for at least a portion of the flow in the reverse direction comprises not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling at least a portion of the reverse flow measured; and

wherein if the ventilator is not a BiPAP ventilator and/or affiliated with a single limb breathing circuit, compensating for at least a portion of the flow in the reverse direction comprises not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling the reverse flow measured.

8. The method of claim 7 , wherein not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling at least a portion of the reverse flow measured comprises not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling the lesser of (i) the reverse flow measured or (ii) a dead space volume.

9. The method of claim 7 , wherein the flow measurement is from the ventilator.

10. The method of claim 1 , further comprising measuring carbon dioxide in at least a portion of the reverse flow measured, and wherein compensating for the flow in the reverse direction further comprises delivering therapeutic gas into the breathing circuit for the reverse flow measured that contains carbon dioxide and not delivering therapeutic gas into the breathing circuit for the reverse flow measured that does not contain carbon dioxide.

11. The method of claim 1 , wherein the flow of the breathing circuit gas through and/or in fluid communication with the breathing circuit affiliated with the ventilator is measured by at least one bi-directional breathing circuit gas (BCG) flow sensor, and the bi-directional BCG flow sensor one or more of (i) has an operating range for forward flow that is greater than an operating range for reverse flow and (ii) has separate calibration data sets and/or calibration routines for forward and reverse flow.

12. A nitric oxide delivery system comprising:

an injector module for delivering a therapeutic gas into a breathing gas in a breathing circuit, the injector module comprising:

an injector body having a first opening and a second opening, the first opening and the second opening being configured to couple the injector module to the breathing circuit;

a therapeutic gas inlet configured to receive the therapeutic gas and enable injection of the therapeutic gas into the breathing gas in the breathing circuit flowing through the injector module; and

at least one bi-directional BCG flow sensor capable of measuring breathing gas flow in a forward direction and in a reverse direction; and

a control valve in communication with the therapeutic gas inlet;

a control module for providing the therapeutic gas to the therapeutic gas inlet and determining a volume of forward flow and a volume of reverse flow, and the control module being in communication with the at least one bi-directional breathing circuit gas (BCG) flow sensor and the control valve,

wherein when the at least one bi-directional BCG flow sensor measures flow in the reverse direction, the control valve is closed and the therapeutic gas is not delivered into the breathing circuit via the therapeutic gas inlet,

wherein when the at least one bi-directional BCG flow sensor measures flow in the forward direction after the at least one bi-directional BCG flow sensor measures flow in the reverse direction, the therapeutic gas is delivered into the breathing circuit after compensating for the flow in the reverse direction by opening the control valve after the volume of resumed forward flow is at least equal to the volume of reverse flow, and

wherein the therapeutic gas comprises nitric oxide.

13. The nitric oxide delivery system of claim 12 , wherein compensating for the flow in the reverse direction comprises comparing the volume of the flow in the reverse direction to a dead space volume and not delivering therapeutic gas into the breathing circuit until after an amount of forward flow has been measured equaling the lesser of (i) the reverse flow measured or (ii) the dead space volume.

14. The nitric oxide delivery system of claim 12 , wherein information regarding the bi-directional BCG flow is used by the nitric oxide delivery system to ensure that a desired dose of NO is delivered into the injector module, and in turn into the breathing circuit.

15. The nitric oxide delivery system of claim 12 , wherein the compensation for flow in the reverse direction ensures that a desired dose of NO is not over delivered, overdosed, under delivered, and/or under dosed.

16. The nitric oxide delivery system of claim 12 , wherein the at least one bi-directional BCG flow sensor is a thermal mass flow meter.

17. The nitric oxide delivery system of claim 12 , wherein the at least one bi-directional BCG flow sensor measures flow without substantially interfering with flow in the patient breathing circuit.

18. The nitric oxide delivery system of claim 12 , wherein the at least one bi-directional BCG flow sensor has a substantially fast response time of less than about two milliseconds and provides a low resistance flow in the patient breathing circuit of less than about one hundred and fifty Pascals at about 60 standard liters per minute or about 1.5 cm H 2 O at about 60 standard liters per minute.

19. The nitric oxide delivery system of claim 12 , further comprising a carbon dioxide sensor that is one or more of (i) in fluid communication with the injector module and/or a connection between the breathing circuit and a sample line and (ii) is at and/or in the injector module and/or a connection between the breathing circuit and the sample line.

20. The nitric oxide delivery system of claim 19 , wherein compensating for the flow in the reverse direction further comprises delivering therapeutic gas into the breathing circuit for the reverse flow measured that contains carbon dioxide and not delivering therapeutic gas into the breathing circuit for the reverse flow measured that does not contain carbon dioxide.

21. The nitric oxide delivery system of claim 12 , wherein the bi-directional BCG flow sensor one or more of (i) has an operating range for forward flow that is greater than an operating range for reverse flow and (ii) has separate calibration data sets and/or calibration routines for forward and reverse flow.