Efficient controlled cryogenic fluid delivery into a balloon catheter and other treatment devices
Devices, systems, and methods efficiently dilate and/or cool blood vessels and other body tissues. Controlled cooling with balloon catheters and other probes may be effected by a change in phase of a cryogenic fluid, often after measuring a minimum pulse width for actuating an individual solenoid valve along the cooling fluid path, with the measured pulse width allowing gradual inflation of a balloon without excessive venting of cooling fluid.
1. A system for cryogenic treatment of tissue, the system comprising:
a controller, the controller comprising:
a pulse width scan module, the pulse width scan module configured to implement a pulse width scan, the pulse width scan determining a command pulse width;
a treatment protocol module, the treatment protocol module configured to establish a treatment protocol based on the command pulse width received from the pulse width scan module;
a treatment implementation module, the treatment implementation module configured to effect a desired cryogenic tissue treatment, the treatment implementation module in communication with the treatment protocol module;
a fluid path, the fluid path extending from a reservoir of fluid to a balloon of a balloon catheter and then to an exhaust lumen;
a solenoid, the solenoid controlling flow of fluid along the fluid path from the reservoir of fluid to the balloon, the solenoid in communication with the controller; wherein the command pulse width comprises a minimum measured pulse width of the solenoid and
a pressure sensor, the pressure sensor monitoring pressure of the fluid in the exhaust lumen, the pressure sensor in communication with the controller.
2. The system of claim 1 , the controller further comprising a clock, the clock in communication with the treatment implementation module.
3. The system of claim 1 , the solenoid being in communication with the pulse width scan module of the controller and with the treatment protocol module of the controller.
4. The system of claim 1 , the pressure sensor being in communication with the pulse width scan module of the controller and with the treatment protocol module of the controller.
5. The system of claim 1 , wherein the controller includes a processor, the processor programmed with a set of instructions for the pulse width scan module, the set of instructions for the pulse width scan module comprising:
setting a first pulse width having an initial value;
measuring a starting pressure in the exhaust lumen with the pressure sensor;
delivering the first pulse width to the solenoid;
measuring an end exhaust pressure in the exhaust lumen resulting from the first pulse width with the pressure sensor;
comparing the end exhaust pressure to the starting exhaust pressure to determine if a threshold change in pressure has been produced.
6. The system of claim 5 , wherein the set of instructions for the pulse width scan module further comprises:
setting a second pulse width which is greater than the first pulse width if the threshold change was not produced;
measuring an exhaust pressure in the exhaust lumen with the pressure sensor;
delivering the second pulse width to the solenoid;
measuring an end exhaust pressure resulting from the second pulse width with the pressure sensor; and
comparing the end exhaust pressure to the starting exhaust pressure to determine if a threshold change in pressure has been produced.
7. The system of claim 5 , wherein the set of instructions for the pulse width scan module further comprises:
transmitting a command pulse width to the treatment protocol module if the threshold change was produced, the command pulse width being the first pulse width.
8. The system of claim 1 , the processor further programmed with a set of instructions for the treatment implementation module, the set of instructions for the treatment implementation module comprising:
transmitting the command pulse width to the solenoid;
measuring an exhaust pressure in the exhaust lumen with the pressure sensor;
comparing the measured exhaust pressure to a target pressure.
9. The system of claim 8 , the set of instructions for the treatment implementation module further comprising
transmitting the command pulse width to the solenoid if the target pressure was not reached;
measuring an exhaust pressure in the exhaust lumen with the pressure sensor;
comparing the measured exhaust pressure to the target pressure.
10. The system of claim 1 , wherein the treatment protocol module is configured to transmit a plurality of command pulse widths to the solenoid, each command pulse width causing the solenoid to open thereby allowing fluid from the reservoir of fluid to flow along the fluid path to the balloon.
11. The system of claim 1 , wherein the reservoir of fluid is maintained at a pressure greater than 650 psi.
12. The system of claim 1 , further comprising a housing, the housing comprising the controller, the fluid reservoir, the solenoid, and a portion of the fluid pathway.
13. The system of claim 12 , the housing engaged to the balloon catheter.
14. The system of claim 1 , the system further comprising a pressure control portion, the pressure control portion comprising the reservoir of fluid, the solenoid, the fluid path, the balloon, the exhaust lumen, a pressure relief valve and a vent valve;
the pressure relief valve configured to control the release of fluid from the exhaust lumen; and
the vent valve configured to limit the flow of fluid to the balloon.
15. The system of claim 1 , the system further comprising a fluid shut off portion, the fluid shut off portion comprising the solenoid, a vacuum switch, and a battery;
the vacuum switch being connected to the solenoid by a circuit powered by the battery.
16. The system of claim 1 , wherein the command pulse width is a measured characteristic of the solenoid in situ.
17. The system of claim 1 , wherein the pulse width scan comprises a plurality of sequential pulse widths beginning with an initial short pulse width and increasing by a step size.
18. The system of claim 1 , wherein the plurality of pulse widths successively increases from an initial short pulse width.
19. The system of claim 1 , wherein the command pulse width further comprises a small safety factor.
20. A system for cryogenic treatment of tissue, the system comprising:
a fluid path, the fluid path extending from a reservoir of fluid to a balloon of a balloon catheter and then to an exhaust lumen;
a solenoid, the solenoid controlling flow of fluid along the fluid path from the reservoir of fluid to the balloon;
a pressure sensor, the pressure sensor monitoring pressure of the fluid in the exhaust lumen;
a controller in communication with the solenoid and the pressure sensor, the controller comprising:
a pulse width scan module configured to determine a minimum electrical pulse for the solenoid in situ;
a treatment protocol module configured to establish a treatment protocol based on the minimum electrical pulse determined by the pulse width scan module;
a treatment implementation module to implement the treatment protocol, the treatment implementation module in communication with the treatment protocol module.