UBC Theses and Dissertations
Optical and physical heart stabilization for cardiac surgery Gilhuly, Terence
Cardiopulmonary bypass (CPB) machines impose a great deal of harm to the patient during cardiac surgeries demanding their use. The damage they cause ranges from inflammation of the immune response and other chemical imbalances to mechanical problems such as the destruction of platelets and red blood cells by the pump's rollers as the blood cycles through the pump. If this damage is eliminated, patient recovery time both in and out of the hospital could be reduced at great savings to patients, taxpayers and hospitals alike. This thesis proposes, details and evaluates surgical devices and techniques that would permit operation on a beating heart toxiccur without the use of a C P B machine. Specifically designed for Coronary Artery Bypass Grafting (CABG) surgery, but applicable to other surgeries as well, these devices and techniques concentrate on stabilizing, or making apparent the stabilization, of anastomosis sites on the heart so that surgery may proceed unimpeded. Optical strobing devices are presented first. Theoretically, by strobing the heart according to the patient's E K G signal, the surgeon will only see the heart at a certain time in the cardiac cycle making the heart seem frozen in that position. Thus, with this frozen image, the surgeon will be able to suture to the heart as if it were still. The devices presented here trigger off of a patient's E K G R-wave, producing a pulse of light that is both adjustable in delay to start and length of time on. The adjustments allow the timing of the light so that it can be turned on at any point in the cardiac cycle and left on for as much time as the surgeon desires. Typically these are set so that the strobing occurs at the end of the diastolic period when the heart is nearly filled with blood, for a length of time that is short enough to maintain a frozen image of the heart, yet long enough to allow the surgeon to make their stitch. A physical method of stabilizing the immediate section of the heart where the graft would take place is also put forward here. This stabilizing device consists of a rigid platform that fixates to the heart with vacuum pressure and is then rigidly connected to the patient at their retractor with a surgical arm newly developed for this purpose and also presented in this document. The stabilization device is a "C"- shaped ring. Its vacuum is provided in a continuous field to permit greater hold at lower pressures with a smaller sized device than could occur while using discrete suction cups. The arm is a seven link, nine DOF redundant serial linkage. It features a lightweight, quick to activate, highly dextrous, unobtrusive design relying on pneumatic pressure for fixation. It mounts to the retractor to couple its motion to the patients should they cough or otherwise move during the surgery. This mounting eliminates the danger of injury from this source and is unobtrusive relative to floor or table-mount designs. A number of other novel stabilization devices and surgical arms are presented, as well. In designing the stabilizing device and surgical arm, required end effector force and torque estimates were determined by scaling force and torque measurements taken from pigs to representative force and torque values for large humans.
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