Surgery – Instruments – Cyrogenic application
Patent
1996-11-01
1998-06-02
Kamm, William E.
Surgery
Instruments
Cyrogenic application
607 96, 607104, 607107, 606 23, A61B 1736
Patent
active
057591822
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to cryosurgical probes.
Cryosurgical probes employing a cooling element disposed at a distal end of a flexible catheter are used in the treatment of internal bodily organs such as the heart.
An example of a cryosurgical probe is disclosed in the British published patent application number GB-A-2 226 497. This probe comprises a handle portion. a flexible catheter and a probe head. The probe head may be cooled by the expansion of a refrigerant fluid within a cavity of the probe head.
In use, the probe head and catheter are inserted into, for example, a patient's blood vessel such as the femoral vein. and art steered so that the probe head occupies a position within the heart. High pressure refrigerant gas is then supplied through the catheter to the probe head to cause cryosurgical necrosis of small areas of the cardiac tissue which are responsible for malfunctions such as cardiac arrhythmias.
In contrast to, for example, rigid cryosurgical probes such as the probes described in GB-B-1457981 and GB-B-1108905, there are very severe constraints on the size of the probe head and the flexible catheter linking the probe head to the handle. These constraints tend to limit the maximum refrigerant flow to the probe head, and so the cooling efficiency of the probe head is particularly important.
The cooling efficiency of the probe head in this type of device is dependent on a number of factors, including the initial temperature of the high pressure refrigerant gas. For this reason, the probe head in GE-A-2 226 497 employs a heat exchanger comprising a spirally wound section of a gas delivery tube, to allow the exhaust (expanded) gas to cool the high pressure refrigerant. However, due to the size limitations of the probe head, this arrangement provides inefficient cooling of the refrigerant gas. The arrangement also leads to an undesirably bulky probe head. The size of the probe head limits the minimum vein diameter in which the probe can be used.
SUMMARY OF THE INVENTION
It is an aim of this invention to improve the cooling efficiency of a cryosurgical probe using a flexible catheter.
This invention provides a cryosurgical probe comprising: a probe head operable to be cooled by the expansion of a refrigerant fluid within the probe head; a probe handle having means for precooling the refrigerant fluid; and a flexible catheter linking the probe handle and the probe head, the catheter defining a channel for carrying precooled refrigerant fluid from the probe handle to the probe head.
The invention addresses the above problems by providing precooling of the refrigerant fluid (e.g. a gas) at the probe handle, rather than at the probe head. This allows a much more powerful precooling arrangement (e.g. a dedicated refrigeration apparatus rather than merely a heat exchanger for heat transfer with the exhaust gases) to be used, since the limits on the size of the probe handle are much less stringent than those relating to the probe head. The probe head and the flexible catheter can be made smaller, because there is no need to employ a heat exchanger at the probe head and because the increased efficiency of the probe head (using the pre-cooled refrigerant fluid) means that a lower fluid flow is required to the probe head. This allows the probe to be used in narrower veins or in younger patients. Also, a heat insulating and flexible material (such as a plastics material) can be used (in place of commonly used stainless steel) to transport the high pressure refrigerant in the catheter and probe head, since heat exchange at these points is no longer required.
In other words, this invention provides a cryosurgical catheter using a two-stage cooling process. The incoming refrigerant fluid is first pre-cooled by a relatively bulky but high-capacity refrigeration apparatus in the probe handle. This in turn makes the second stage of cooling, namely the expansion of the fluid in the probe head, more efficient.
Although various different precooling arrangements could be used. such a
REFERENCES:
patent: 3630203 (1971-12-01), Sellinger
patent: 5108390 (1992-04-01), Potocky et al.
patent: 5254116 (1993-10-01), Baust et al.
patent: 5275595 (1994-01-01), Dobak, III
patent: 5281213 (1994-01-01), Milder et al.
patent: 5328467 (1994-07-01), Edwards et al.
patent: 5403309 (1995-04-01), Coleman et al.
patent: 5522870 (1996-06-01), Ben-Zion
Reeves Simon Richard
Varney Kelvin John
Kamm William E.
Layno Carl H.
Spembly Medical Limited
LandOfFree
Cryosurgical probe with pre-cooling feature does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cryosurgical probe with pre-cooling feature, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cryosurgical probe with pre-cooling feature will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1454047