Olsen E

Voluntary control of an ileal pouch by coordinated electrical stimulation. A pilot study in the dog.

Heal reservoirs were constructed in four dogs under general anesthesia and stimulated by means of a constant current generator that produced pulse trains at frequencies between 6 Hz and 1.67 kHz. Stimulation at 6 Hz with 50 ms pulses between amplitudes of 15 and 25 mA uniformly produced pouch contraction and reservoir emptying. Stimulation at other frequencies did not cause pouch emptying although pressure increases were sometimes observed. Such electrical stimulation may be useful for voluntary control of intestinal reservoirs when used as replacement for urinary bladder or colon. The mechanism by which the intestinal contraction is preduced appears to be different than that produced by slow wave pacing

Hemodynamic changes with posture in calves with total artificial heart

Hemodynamic changes with posture, sitting versus standing, were analyzed in five Holstein calves with the Cleveland Clinic-Nimbus TAH. This total artificial heart (TAH) has a left master alternate control mode that adjusts the pump rate and consequently pump flow proportional to the pulmonary venous return to the left pump (AUTO period). However, in this series of experiments, the pump reached its maximum beat rate within 1-5 days post operatively, after which pump flow could not increase (MAX period). Hemodynamic parameters (RAP, LAP, PAP, AoP, and pump flow) were obtained every 15-20 min throughout the experiments for as long as 120 days and averaged for each posture for each period. During the AUTO period, the flow while standing was significantly higher than that while sitting (standing: 8.7 +/- 0.2 L/min; sitting: 7.5 +/- 0.4 L/min; p < 0.05), and the systemic vascular resistance (SVR) was significantly lower (standing: 895 +/- 93 dyne.sec.m-5; sitting: 1,041 +/- 124 dyne.sec.m-5; p < 0.05). During the MAX period, the AoP and SVR standing were significantly lower than those sitting (AoP standing: 91 +/- 7 mmHg; AoP sitting: 98 +/- 7 mmHg; p < 0.05; SVR standing: 652 +/- 75 mmHg; SVR sitting: 730 +/- 96 mmHg; p < 0.05). The Cleveland Clinic-Nimbus TAH responded well to these changes in position, increasing pump flow and maintaining the AoP during the AUTO period.

A canine model for global control of the reimplanted larynx. A potential avenue for human laryngeal transplantation.

Previous attempts at laryngeal transplantation have failed because the grafted organ could not be dynamically rehabilitated. Nerve-muscle pedicles were used to reinnervate each of the principal intrinsic laryngeal muscles in 20 dogs after autotransplantation with conservation of the essential nutrient vessels. Afferent information obtained by sensors fixed to the chest (a strain gauge and transthoracic impedance electrode) was channeled to an electronic package for coordinated stimulation of pedicles reinnervating the posterior cricoartenoideus (opening), the cricothyroideus (elongation) and the thyroarytenoideus (closure of the vocal cords) by perineural electrodes. Corresponding vocal cord motion was videotaped on the same screen as sensor displacements and stimulating currents (approximately 2 V, 60 Hz, and 4 msec pulse width). Clear responses were recorded in all evaluable animals (n = 8), but contraction was stronger with longer reinnervation time (3-7 weeks). Based on this feasibility study, chronic experiments are planned that will set the ground work for possible future human laryngeal transplantation.