These patients appear to respond best to permanent quadripolar lead placement but long-term results do not appear to be independently affected by the method of test stimulation. Loss of benefit over time is not common.
Patients with pulmonary insufficiency due to scleroderma have long been considered suboptimal candidates for lung transplantation. This has been supported by small single-center experiences that did not reflect the entire U.S. experience. We sought to evaluate the outcome of patients with scleroderma who underwent lung transplantation. We conducted a retrospective review of 47 patients with scleroderma who underwent lung transplantation at 23 U.S. centers between 1987 and 2004 and were reported to the United Network for Organ Sharing. Women constituted 57% of the patients. The mean age was 46 years. Twenty-seven patients received single lung transplants (57%), and the remaining received double lung transplants. The mean cold ischemia time was 4.1 hours. There were 7 early deaths (< or =30 days) and 17 late deaths (> 30 days). The causes of early death were primary graft failure and a cardiac event in two patients each and bacterial infection and stroke in one patient each. Late mortality was due to infection in seven patients, respiratory failure in three, malignancy in two, and multisystem organ failure, rejection, pulmonary hypertension, and a cardiac event in one patient each. The causes of early and late death were not recorded for two patients. One patient received a second transplant owing to graft failure of the first. Twenty-three patients (49%) were alive at a mean follow-up of 24 months. The Kaplan-Meier 1- and 3-year survival rates were 67.6% and 45.9% respectively, which are not significantly different from those of 10,070 patients given transplants for other lung conditions during the same period (75.5% and 58.8% respectively, P = 0.25). Donor gender, recipient's age, and type of transplant did not affect survival. In carefully selected patients with scleroderma who have end-stage lung disease, lung transplantation is a valid life-saving therapeutic option. Available data suggest acceptable short-term morbidity and mortality and a long-term survival similar to that of patients given transplants for other lung conditions.
In this paper, we report on the development of an implantable pressure sensing system that is powered by mechanical vibrations in the audible acoustic frequency range. This technique significantly enhances interrogation range, alleviates the misalignment issues commonly encountered with inductive powering, and simplifies the external receiver circuitry. The interrogation scheme consists of two phases: a mechanical vibration phase and an electrical radiation phase. During the first phase, a piezoelectric cantilever acts as an acoustic receiver and charges a capacitor by converting sound vibration harmonics occurring at its resonant frequency into electrical power. In the subsequent electrical phase, when the cantilever is not vibrating, the stored electric charge is discharged across an LC tank whose inductor is pressure sensitive; hence, when the LC tank oscillates at its natural resonant frequency, it radiates a high-frequency signal that is detectable using an external receiver and its frequency corresponds to the measured pressure. The pressure sensitive inductor consists of a planar coil (single loop of wire) with a ferrite core whose distance to the coil varies with applied pressure. A prototype of the implantable pressure sensor is fabricated and tested, both in vitro and in vivo (swine bladder). A pressure sensitivity of 1 kHz/cm H2O is achieved with minimal misalignment sensitivity (26% drop at 90° misalignment between the implanted device and acoustic source; 60% drop at 90° misalignment between the implanted device and RF receiver coil).
Sacral neuromodulation has had a tremendous impact on the treatment of urinary incontinence and lower urinary tract symptoms for patients with neurologic conditions. This stimulation does not use real-time data from the body or input from the patient. Incorporating this is the goal of those pursuing a neuroprosthesis to enhance bladder function for these patients. Investigators have demonstrated the effectiveness of conditional (also called closed-loop) feedback in animal models as well as limited human studies. Dorsal genital nerve, pudendal nerve, S3 afferent nerve roots, S1 and S2 ganglia have all been used as targets for stimulation. Most of these have also been used as sources of afferent nerve information using sophisticated nerve electrode arrays and filtering algorithms to detect significant bladder events and even to estimate the fullness of the bladder. There are problems with afferent nerve sensing, however. Some of these include sensor migration and low signal to noise ratios. Implantable pressure sensors have also been investigated that have their own unique challenges, such as erosion and sensor drift. As technology improves, an intelligent neuroprosthesis with the ability to sense significant bladder events and stimulate as needed will evolve.
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