TITLE: COMPOSITE AORTIC CANULA [TECHNICAL FIELDS: This invention relates to the field of cardiac surgery requiring cardio-pulmonary bypass.
[BACKGROUND]To establish the circulation using a cardio-pulmonary bypass machine(heart-lung machine) and to keep the heart motionless during operation, surgeons usually require three gadgets applied to the Aorta (the large artery coming out of heart). These are (from cephalic or head-end, towards cardiac or the heartend side); aortic canula, cross-clamp and the antegrade cardiolegia line or the root-canula.
Aortic canula is a tubing of plastic or metal, positioned into the Aorta, a few inches above the heart, to deliver blood from the Heart-Lung machine to the patient. Cross-clamp is a metallic clamp placed across the Aorta, below theAortic canula and above the coronary arteries, so as to occlude the flow of blood into the coronary arteries. This occlusion is needed to keep the heart still while the surgeon operates upon it.
Besides the Aortic canula and the 'crosselamp', another tubing (called 'Root canula') is placed into theAorta, in between the crosselamp' and the coronary arteries. Through the rootcanula a special fluid (cardioplegia solution) is delivered into the coronas v arteries so that the heart remains paralysed with minimal energy requirement during the period when the cross-clamp is on.
The main problem with this present set-up is that in patients with heart disease, the Aorta, just like other arteries, has deposits of calcium in its inner lining. Application of the 'cross clamp' leads to rupture and dislodgement (embolism) of these calcium deposits to the patient's brain : this is a major cause of strokes following heart surgery.
Sometimes the crushing effect of the cross-clamp leads to partial or even complete rupture of the aortic wall. Furthermore, the two canulae and the cross-clamp produce crowding in a small operative area; also the holes for the two canulae need to be closed separately which is wasteful of the operating time.
[ESSENTIAL TECHNICAL FEATURES]According to the present invention there is provided a composite aortic canula serving the combined function of an aortic canula for cardiopulmonary bypass, an equivalent of the crossclamp in the form of an internally occluding balloon, shaped and position so as not to encroach upon the orifice of the arteries arising from the aortic arch, a means of controlled inflation and deflation of that balloon, an in built means for the delivery of antegrade cardioplegia, a means for protecting insertion of unwanted length of the canula into the aorta and a detachable lid at the surgeon's end of the canula.
[EXAMPLE]:A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 shows the composite canula with un-inflated balloon, it's inflation channel, the cardioplegia channel, the protective collar and the detachable lid.
Figure 2 shows the horizontal cross-section of the composite canula with un-inflated balloon.
Figure 3 shows the horizontal cross-section of the composite canula with distended balloon.
Figure 4 shows the composite canula positioned inside the Aorta with the balloon distended (shown in anatomically horizontal cross-section).
Figure 5 shows the crossection of the wall of the balloon with it's differential thickness.
Figure 6 shows the end-on view of the Aortic end of the composite canula with distended balloon.
DETAILED DESCRIPTIONReferring to the drawings the composite aortic canula consists of the following: C4N'L'L4; a plastic / metallic tubing with a bevelled, angled or straight end 10 (aortic-end), and the other circular end 11(surgeon's-end). It's body is colour marked for upper (cephalic or towards patient's head) and lower (cardiac or towardspatient's heart) surfaces. Diameter of the canula would vary according to the size of the patient.
b) INFLATABLE BALLOON with DlFFERENrL4L WALL THICAWESS; an inflatable balloon 12 around the lower partof the canula above the bevelled end. The balloon is set around the wall of the canula with a slant which is nearly parallel tothe slant of the bevel. The wall of the balloon has a differential thickness with thicker wall in it's upper half and more so inthe cephalic surface to give it a tear-drop or pearl shape upon inflation as shown in Figures 3-5. The size of the balloon variesaccording to the size of the canula.
b) LNFLA rloN cH4vvEL; A channel 13 in the cephalic or the shorter wall of the canula which leads into the balloon and opens 18 inside it. This channel comes out of the body of the canula as a separate tube near the surgeon's-end of the canula to end in a twoway tap to allow controlled inflation ad deflation of the balloon.
c) CARDIOPLECIA CH4NNEL; a second channel 14 for delivering cardioplegia, in the lower or the cardiac wall (towards patient's heart) of the canula, with the end of the channel opening out 19 above the edge of the distend balloon. Like the inflation channel 13 the cardioplegia channel 14 also leaves the body of the canula near the surgeon' send to end in a twoway tap.
d) PROTECfl1E' COLL4R; a circular rim 15 above the iflatable balloon. The distance of this rim from the end of thecanula varies according to the patient's size and hence the length of the canula.
e) DErACE4BLE LID; A detachable lid 16 closing the surgeon's end. It is joined by a plastic strip on one side to a plasticring around the canula at about 1 centimetre from the lid. The junction of the joining strip and the ring 17 is weak on one sidefrom which point the ring could be broken after opening the lid and the whole could be removed from the canula.
The composite canula would be inserted into the Aorta with it's balloon deflated by suction through the inflationchannel. Removing the detachable lid 16 at the surgeon's end would allow it to be connected to the tubings of the cardiopulmonary bypass machine. Once the heart needs to be stopped the balloon 12 would be distended with fluid or air viainflation channel 13 as illustrated in figures 2 and 3. This would allow uni':lirectioral flow of blood away from the heart. The special shape of the balloon with differential thickening of it's walls, as shown in figures 3-5 would prevent it from occluding the lumen of arteries arising from the arch of Aorta, as illustrated in figure 3. When required, cardioplegia solution would be delivered via cardioplegia channel 14. Protective collar 15 is to prevent over insertion of the canula into the Aorta.
Once the need for occluding the blood flow towards the heart is over, the balloon is deflated via it's channel 13, allowing blood to flow in both directions; towards and away from the heart. when the cardiopulmonary bypass is to be discontinued the composite canula is removed from the Aorta with its balloon deflated