NEUROMODULATION CRYOTHERAPEUTIC DEVICES AND ASSOCIATED SYSTEMS AND METHODS

1 . A cryotherapeutic device, comprising:

a shaft having a distal portion, wherein the shaft is configured to locate the distal portion intravascularly at a treatment site at least proximate a renal artery or renal ostium;

a cooling assembly at the distal portion of the shaft, the cooling assembly including an expansion chamber having a rupture pressure and a threshold pressure below the rupture pressure;

pressure monitoring lumen along at least a portion the shaft, the pressure monitoring lumen having a first opening at the distal portion of the shaft and a second opening at the proximal portion of the shaft, wherein the first opening is in fluid communication with the expansion chamber; and

a pressure sensor configured to be located externally of the patient and operatively coupled to the pressure monitoring lumen, wherein the pressure monitoring lumen and pressure sensor are configured to provide a signal indicating a change of pressure within the expansion chamber.

2 . The cryotherapeutic device of claim 1 wherein:

the pressure monitoring lumen has a length at least equal to a length of the shaft; and

the pressure monitoring lumen is configured to provide a response time of at most 0.5 second from the expansion chamber to the pressure sensor.

3 . The cryotherapeutic device of claim 1 , further comprising:

a supply lumen along at least a portion of the shaft, the supply lumen being in fluid communication with the expansion chamber;

an exhaust lumen along at least a portion of the shaft, the exhaust lumen being in fluid communication with the expansion chamber;

a valve coupled to the supply lumen and to the pressure sensor; and

wherein—

the expansion chamber comprises a balloon,

the valve is configured to at least partially reduce refrigerant flow through the supply lumen when the pressure sensor measures a pressure within the expandable member above the threshold pressure,

the pressure monitoring lumen has an inner diameter configured to accurately gauge pressure within the expandable member and an outer diameter configured to have a negligible effect on outflow of refrigerant through the exhaust lumen, and

the pressure monitoring lumen is configured to provide a response time of less than 1 second from the expansion chamber to the pressure sensor.

4 . The cryotherapeutic device of claim 1 , further comprising:

a supply lumen along at least a portion of the shaft, the supply lumen being configured to receive at least a substantially liquid refrigerant;

an exhaust lumen along at least a portion of the shaft, the exhaust lumen being in fluid communication with the expansion chamber; and

wherein—

the exhaust lumen has an inner cross-sectional dimension,

the supply lumen and the pressure monitoring lumen together have an outer cross-sectional dimension at the distal portion of the shaft, and

the inner and outer cross-sectional dimensions have a ratio between 4:1 and 10:1.

5 . The cryotherapeutic device of claim 1 wherein:

the shaft has a first length; and

the pressure monitoring lumen has an inner diameter of approximately 0.010, an outer diameter of approximately 0.015 inch (0.381 mm), and a second length at least equal to the first length of the shaft.

6 . The cryotherapeutic device of claim 5 wherein the shaft is configured to fit within a 6 Fr guide sheath, the first length of the shaft being at least 120 cm.

7 . The cryotherapeutic device of claim 1 , further comprising a controller coupled to the shaft and to the pressure sensor, wherein the controller is configured to at least reduce refrigerant flow to the expansion chamber when the pressure sensor measures the threshold pressure or higher.

8 . The cryotherapeutic device of claim 1 , further comprising an adapter having a channel between the pressure sensor and the pressure monitoring lumen, wherein the channel has a volume of no more than 0.1 cc.

9 . The cryotherapeutic device of claim 1 wherein the expansion chamber comprises a compliant material having a rupture pressure of at least 300 psi.

10 . The cryotherapeutic device of claim 1 wherein the expansion chamber comprises a compliant material having a rupture pressure of at most 200 psi.

11 . The cryotherapeutic device of claim 1 wherein:

the shaft is configured to fit within a 6 Fr guide sheath; and

the cooling assembly includes an expandable member having a delivery state and an expanded state, at least a portion of the expandable member defining the expansion chamber, wherein the expandable member has an outer diameter from approximately 3 mm to approximately 10 mm in the expanded state.

12 . A cryotherapeutic device comprising:

a shaft having a proximal portion and a distal portion;

a cooling assembly at the distal portion of the shaft, wherein the cooling assembly includes an expansion chamber in fluid communication with the distal portion of the shaft; and

a pressure sensor at the proximal portion of the shaft and in fluid communication with the expansion chamber such that a time delay between a change in pressure in the expansion chamber and a measured pressure at the pressure sensor is within a response time that prevents rupture of the expansion chamber.

13 . The cryotherapeutic device of claim 12 wherein the response time is less than 0.01 second.

14 . The cryotherapeutic device of claim 12 , further comprising a pressure monitoring lumen having a proximal end portion coupled to the pressure sensor and a distal end portion in fluid communication with the expansion chamber.

15 . The cryotherapeutic device of claim 14 wherein the pressure monitoring lumen has an inner diameter of no greater than 0.030 inch (0.762 mm) and an outer diameter of no greater than 0.060 inch (1.52 mm).

16 . The cryotherapeutic device of claim 14 wherein the pressure monitoring lumen has a length of at least 48 inches (122 cm).

17 . The cryotherapeutic device of claim 14 , further comprising an adaptor coupled between the pressure sensor and the pressure monitoring lumen, wherein the adaptor has an internal volume of less than 0.1 cc.

18 . The cryotherapeutic device of claim 12 wherein:

the response time is less than 0.1 second; and

the cryotherapeutic device further comprises a pressure monitoring lumen having a proximal end portion coupled to the pressure sensor and a distal end portion in fluid communication with the expansion chamber, the pressure monitoring lumen having a length of at least 120 cm.

19 . The cryotherapeutic device of claim 12 wherein:

the shaft is configured to fit with in 6 Fr guide sheath; and

the cooling assembly includes an expandable member having a delivery state and an expanded state, at least a portion of the expandable member defining the expansion chamber, wherein the expandable member has a maximum outer diameter of 10 mm in the expanded state and a length of at most 10 mm.

20 . A method for treating a patient, the method comprising:

positioning a cooling assembly at a distal portion of a shaft at least proximate a peripheral blood vessel, wherein the cooling assembly includes an expansion chamber having a threshold pressure;

expanding a refrigerant in the expansion chamber;

applying therapeutic cooling with the cooling assembly to nerves proximate the peripheral blood vessel;

measuring a pressure within the expansion chamber with an external pressure sensor, wherein the external pressure sensor is coupled to a pressure monitoring lumen in fluid communication with the expansion chamber; and

indicating when the measured pressure within the expansion chamber is at least the threshold pressure.

21 . The method of claim 20 wherein measuring a pressure within the expansion chamber with an external pressure sensor comprises measuring a pressure within the expansion chamber such that a time delay between a change in pressure within the expansion chamber and the measure pressure at the external pressure sensor is less than 1 second.

22 . The method of claim 20 wherein indicating when the measured pressure within the expansion chamber is at least at the threshold pressure comprises indicating when the measured pressure is close to a rupture pressure of the expansion chamber.

23 . The method of claim 20 , further comprising coupling the external pressure sensor to the pressure monitoring lumen with an adaptor having an internal volume of no more than 0.1 cc.

24 . The method of claim 20 wherein:

positioning the cooling assembly at the distal portion of the shaft at least proximate the peripheral blood vessel comprises positioning the cooling assembly at the distal end of the shaft at least proximate a renal artery;

measuring a pressure within the expansion chamber with the external pressure sensor comprises measuring a pressure within the expansion chamber via a pressure monitoring lumen having a length of at least 120 cm; and

indicating when the measured pressure within the expansion chamber is at least the threshold pressure comprises indicating the measured pressure within a response time that prevents rupture of the expansion chamber.

25 . A method for treating a patient, the method comprising:

intravascularly positioning an expansion chamber proximate post-ganglionic neural fibers that innervate a kidney of the patient;

cryomodulating at least a portion of the neural fibers proximate the expansion chamber; and

measuring a pressure within the expansion chamber with an external pressure sensor, wherein the external pressure sensor is in fluid communication with the expansion chamber.

26 . The method of claim 24 wherein measuring a pressure within the expansion chamber with an external pressure sensor comprises coupling the external pressure sensor to a pressure monitoring lumen extending from a distal portion of a shaft to a proximal portion of the shaft, the expansion chamber being at the distal portion of the shaft.

27 . The method of claim 26 wherein measuring a pressure includes measuring a pressure with the external pressure sensor via the pressure monitoring lumen within 0.1 second of a change in pressure at the expansion chamber.

28 . The method of claim 27 wherein measuring a pressure includes using a pressure monitoring lumen having a length of at least 120 mm and an inner diameter of no more than 0.762 mm.