US 20070083161 A1
A method of performing minimally invasive cardiac surgery includes the step of creating an access aperture into a patient's chest cavity, the access aperture being considerably smaller than a traditional cardiac surgery incision. A cannula is provided that has an oval portion with a longer major axis and a shorter minor axis and the cannula is inserted into the chest cavity through the access aperture.
84. A cannula for use in conducting fluid to or from a body, comprising: a cannula body having a proximal end, a distal end, and a lumen extending between the proximal and distal ends; a first fluid aperture formed on the proximal end; a second fluid aperture formed adjacent the distal end; and a reinforcement integrally provided in the cannula body; wherein a cross section of a first portion of the cannula body is non-circular and has a major cross-sectional axis and a minor cross-sectional axis, the length of the major axis being greater than the length of the minor axis and wherein the lumen extending through the first portion of the cannula body has a substantially similar cross-sectional shape as the cross section of the first portion of the cannula body.
85. The cannula of
86. The cannula of
87. The cannula of
88. A cannula for use in conducting fluid to or from a body, comprising: a cannula body having a proximal end and a distal end, the cannula body having an outer surface; a lumen extending between the proximal and distal ends, the lumen defined by an inner surface of the cannula body; a first fluid aperture formed on the proximal end; and a second fluid aperture formed adjacent the distal end; wherein a first portion of the cannula body has a cross section of the outer surface that is non-circular and a cross section of the inner surface that is the same shape as the cross section of the outer surface.
89. The cannula of
90. The cannula of
91. The cannula of
92. The cannula of
93. A cannula for use in conducting fluid to or from a body, comprising: a cannula body having a proximal end with a circular cross section, a distal end with a circular cross section, and a lumen extending between the proximal and distal ends; a first fluid aperture formed on the proximal end; and a second fluid aperture formed adjacent the distal end; wherein a cross section of a first portion of the cannula body between the proximal end and the distal end is oval.
94. The cannula of
95. The cannula of
96. The cannula of
97. The cannula of
98. The cannula of
99. The cannula of
This application is a continuation of U.S. application Ser. No. 10/026,234, filed Dec. 21, 2001, which is a continuation of U.S. application Ser. No. 09/012,520 filed Jan. 23, 1998, U.S. Pat. No. 6,447,484, which is a continuation in part of U.S. application Ser. No. 08/780,995, filed Jan. 9, 1997, U.S. Pat. No. 5,817,071, all of which are incorporated herein by reference in their entirety.
1. Field of the Invention
This invention relates to cannulas and, more particularly, to a cannula which is oval-shaped in cross-section and therefore ideally suited for use in minimally invasive surgical procedures.
2. Description of the Related Art
Cannulas have a wide variety of applications during surgical procedures. For example, in coronary surgery, venous and arterial cannulas are used to conduct blood between the body and bypass equipment. Cannulas are used to conduct cardioplegia solution for both antigrade and retrograde solution administration, and cannulas are also used as vents, sumps, and for chest tube fluid suction. The structure for these known cannulas generally comprises a cannula body which is circular in cross-section and has at least one lumen extending therethrough which is similarly circular in cross-section. Examples of these structures are seen in U.S. Pat. Nos. 4,639,252, 4,129,129 and 5,395,330.
A recent trend in surgical procedures is to minimize the size of the access apertures formed in the chest cavity. These procedures include mini-sternotomy and minimally invasive cardiac surgery. In each of these procedures, the goal is to reduce the size of the aperture in the chest wall. One problem is achieving this goal is the size, geometry, and space requirements for the instruments, cannulas, and the like which most pass through the reduced size apertures.
The cannula according to the invention overcomes the problems of the prior art by providing a cannula having a prescribed geometry, which more efficiently occupies the space of the aperture without adversely affecting the fluid rate therethrough.
The invention relates to a method of performing minimally invasive cardiac surgery. The method includes the steps of creating an access aperture into a patient's chest cavity that is considerably smaller than a median sternotomy, providing a cannula having an oval portion with a longer major axis and a shorter minor axis, and inserting the cannula into the chest cavity through the access aperture.
The invention further relates to a method of forming a venous cannula. The method includes the step of providing a length of tubing having an outer circular cross-section and having a helically wound wire supporting the tubing wall, the length of tubing having a proximal end and a distal end. The method further includes the steps of forming a segment in the length of tubing, the segment having an outer oval cross-section, such that the proximal end and the distal end of the length of tubing remain with an outer circular cross-section, and providing a flow aperture on the distal end of the length of tubing.
Further still, the invention relates to a cannula for use in conducting fluid to or from a body. The cannula includes a cannula body having a proximal end, a distal end, and a lumen extending between the proximal and distal ends, a first fluid aperture formed on the proximal end, and a second fluid aperture formed adjacent the distal end. A cross-section of a first portion of the cannula body is non-circular and has a major cross-sectional axis and a minor cross-sectional axis, the length of the major axis being greater than the length of the minor axis. The lumen extending through the first portion of the cannula body has the same cross-sectional shape as the cross-section of the first portion of the cannula body.
Other advantages of the invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific embodiments are given by way of illustration only, since, from this detailed description, various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
The invention will now be described with reference to the drawings in which:
Turning now to the drawings and to
One unique feature of the cannula assembly according to the invention is that at least a portion of the cannula body 18 is non-circular. This first non-circular portion 32 is preferably oval in cross-section and is defined by a major cross-sectional axis 34 and a minor cross-sectional axis 36. As will be described further below, the incorporation of a non-circular portion 32 makes the cannula assembly according to the invention ideally suited for use in minimally invasive cardiac surgical procedures.
The obturator 16 comprises a proximal end 48 and a distal end 50. The obturator is adapted to be slidably, telescopically received inside the lumen 24 of the cannula 14. When the obturator is fully received inside the cannula lumen 24, the obturator substantially seals the second set of fluid apertures 30 so that the fluid cannot enter the lumen 24 from the first set of fluid apertures 28 and then egress into the operation field through these apertures.
The cannula assembly 12 described above is ideally suited for use as a venous cannula during a coronary surgical procedure similar to the cannula described in U.S. Pat. No. 4,129,129 which is expressly incorporated herein by reference. In use, the cannula 14, with the obturator 16 fully received therein, is inserted through an appropriate incision into the right atrium and the inferior vena cava. As the distal end 22 of the cannula 14 is inserted into the blood flow passing through the right atrium and inferior vena cava, blood will enter the first set of fluid apertures 28, but the obturator 16 will restrict the flow of blood through the lumen 24 to the second set of fluid apertures 30. Once the cannula 14 is properly positioned, the obturator 16 is removed from the cannula 14, and the luer connector 26 of the cannula 14 is connected to a conventional bypass system. With the cannula 14 in this position, blood enters the lumen 24 through both the first and second fluid apertures 28, 30 and is conducted to the bypass machine.
Traditional cardiac surgery is typically performed by a median sternography in which substantially the entire chest cavity is exposed by cutting the full length of the sternum and spreading back the sternum and ribs to expose the entire pericardium. However, a recent trend in cardiac surgery is to attempt to minimize the size of the access apertures formed in the patient's chest using techniques such as a right or left anterior thoracotomy, mini-sternotomy, and multi-port access apertures. In each of these procedures, the size of the access aperture formed in the patient's chest is considerably smaller than the traditional median sternotomy, thereby reducing the complications and possible side effects associated with such a massive wound. However, reducing the size of the access aperture raises a new set of problems not encountered in the conventional median sternotomy, namely, sufficient space for the receipt of all the instruments and equipment.
One limiting factor to reducing the size of the access aperture in any surgical procedure is the cross-sectional space requirements of the surgical tools which must be inserted through the access aperture. The cannula according to the invention is an improvement over the known cannulas because it more efficiently utilizes the limited space of the access aperture without adversely affecting the fluid flow characteristics through the cannula.
As seen in
While the preferred embodiment of the cannula 14 and cannula assembly 12 described above is a venous cannula, it is to be understood that the invention extends to any cannula inserted into the body through an access aperture including but not limited to an arterial cannula, a cardioplegia cannula (both retrograde and antigrade), a vent, a sump, or a suction tube. Similarly,
A second embodiment of the obturator 76 is shown in
The balloon is adapted for inflation from a retracted state as seen in
A third embodiment of the obturator 90 is shown in
In the third embodiment, the foam member 96 is formed from a soft, pliable foam which can easily be compressed by the opposite sidewalls of the cannula in the non-circular portion as the obturator 90 passes therethrough. Once the obturator 90 is fully received in the lumen 24, the foam member 96 expands outwardly a sufficient distance to substantially seal the fluid apertures 30. Similar to the earlier embodiments, once the cannula assembly 12 is properly positioned, then the obturator is telescopically removed from the lumen. As the obturator is being pulled through the non-circular portions, the opposed sidewalls of the lumen will compress the foam member a sufficient distance to permit passage of the foam member therethrough.
A fourth embodiment of the obturator 100 for a cannula 14 is shown generally in
The flexible disc 108 is formed from a durable material which is sufficiently flexible that the edges of the disc 108 bend, enabling the disc 108 to pass through the first non-circular portion 32 of the cannula body 18, as shown in
As shown in
The elongate member 106 of the obturator 100 may be a solid shaft or wire, or a hollow tube. It is preferred that the elongate member 106 and flexible disc 108 are integrally formed as a single piece, such as by injection molding. However, the elongate member 106 and flexible disc 108 may also be separate and distinct pieces, that are coupled together in a conventional manner.
As shown in
The obturator 100 preferably further includes a stop 114 and a collar or grip 116 as shown. The stop 114 is located on the elongate member 106, adjacent the proximal end 102, and limits the depth of insertion of the obturator 100 in the cannula lumen 24 to prevent damage to either the flexible disc 108 or the distal end 22 of the cannula 14. In the preferred embodiment of the obturator 100, the stop 114 is conical in shape and includes a flat surface 118 and an inclined surface 120. It should be noted, however, that other configurations for the stop 114 may be envisioned. The inclined surface 120 of the conical stop 114 extends toward the distal end 104 of the elongate member 106, while the flat surface 118 is located proximally of the inclined surface 120. When the obturator 100 is fully inserted in the cannula 14, the stop 114 abuts the proximal end 20 of the cannula 14, with a portion of the inclined surface 120 being received in the cannula lumen 24.
The grip 116 is provided at the proximal end 102 of the obturator 100 and is coupled to the elongate member 106. The grip 116 extends beyond the diameter of the elongate member 106 and enables a user to grasp the obturator 100 and remove it from the cannula 14. The grip 116, stop 114, elongate member 106 and flexible disc 108 of the obturator 100 are preferably injection molded as a single, integral piece. However, as discussed above, two or more pieces of the obturator 100 may be separate and distinct and may be coupled together in a conventional manner.
The flexible disc 108 of the obturator 100, the foam member 96 of the obturator 90, and the expandable balloon 78 of the obturator 76 are only three examples of expandable means provided on the obturator to permit passage of the distal end of the obturator through the confines of the lumen and still capable of restricting the flow of fluid through the lumen of the catheter. It is understood that any other means which accommodate the varying diameters fall within the scope of the invention.
The preferred method for forming the cannula 14 according to the invention comprises the steps of extruding a circular length of tubing. Preferably, tubing is formed from silicone or polyvinyl chloride. Depending upon the particular application, a helically wound spring may be received on the inside of the hollow tube and either be adhesively fastened therein or integrally molded therein. Next, the tubing is cut to the desired length, and then the non-circular portion is formed by positioning the length of the tube between two opposed platens and then compressing the two platens a sufficient distance to obtain the desired non-circular or oval-shaped configuration. Once the spring has been plastically deformed, it will retain the pliable cannula body in the oval or non-circular configuration. Finally, the luer connector and flow aperture member are mounted to the proximal and distal ends thereof. The cannula 14 can be compressed to create the non-circular configuration prior to or subsequent to mounting of the elements on the proximal and distal ends thereof. In the event that two different non-circular portions are formed along the length of the cannula, then the step of compressing the cannula body between two opposed platens is repeated, as necessary, for the additional non-circular sections.
With the rapid evolution of surgical procedures which minimize the size of the access aperture cut into the patient, the known, conventional, surgical tools such as cannulas, vents, sumps, or suction tubes must be adapted to accommodate such advances. The non-circular cannula according to the invention is one such modification which assists the surgeons in achieving the goal of minimizing the wound size for a variety of surgical procedures. This advantage is accomplished without adversely affecting the fluid flow rate through the tubing or otherwise adversely affecting the performance of the tubing.
Reasonable variation and modification are possible within the spirit of the foregoing specification and drawings without departing from the scope of the invention.