Clinical experience with intraaortic balloon pumps.
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Aged↗
Biomedical subjects
H Thoma
Publications and source records attributed to H Thoma.
Multichannel stimulation of phrenic nerves by epineural electrodes. Clinical experience and future developments.
Between 1983 and 1992, 23 patients with complete ventilatory insufficiency of differing etiologies were treated with an eight channel implant (Medimplant Inc., Vienna) for fatigue free stimulation of both phrenic nerves. Data for 15 patients with high spinal cord lesions (ages: 9-51 years) are summarized: 1) level of lesion: C0, 3 patients; C1/C2, 4; C2/C3, 8; 2) time between incident and implantation: 3-14 months; 3) diaphragm training: 1-22 months; 4) chronic pacing: 5-83 months; 5) tracheostomy closed: 7 patients; 6) living permanently at home: 13 patients; 7) respiratory rate per minute: 12-17; 8) duration of inspiration: 1.0-1.3 sec; 9) tidal volume: 7-20 ml/kg body weight; 10) volume per minute: 121-198 ml/kg body weight; 11) pH: 7.39-7.42; 12) pCO2: 22.9-38.6 mmHg; 13) pO2: 81.2-104.5 mmHg; and 14) died by December 1992, 4 patients. All currently available implants for phrenic pacing need an external power supply and radio control. The authors have developed and tested the first fully implantable device. Features of this implant include an electronic circuit based on the microcontroller MC68HC705C8; surface mounted technology (SMD); eight channels; constant current source adjustable to 5 mA in 256 steps, impulse duration: 100-1000 musec, stimulation frequency: 1-33 Hz; and minimum lifetime: 3 years. The implant is programmed via bidirectional radio transmission using an IBM compatible computer. The dimensions, including battery, eight electrode connectors, and antenna, are 67 x 48 x 13 mm. The implant weights 58 g. This new device may improve patients' safety and quality of life in the near future.
Adolescent↗
Artificial heart driven by an automatic driving system.
Thrombi formation within artificial ventricles is caused by the effects of biomaterials, stagnation areas, and major turbulences. During systolic and diastolic cycles, stagnation area increase in hearts that are properly designed. Stagnation areas may also occur in properly designed artificial hearts that are not working with a maximum stroke volume. The ellipsoid heart avoids stagnation areas and major turbulences because all the inside surfaces have an adequate washout with blood. The optimum washout of these surfaces is obtained by driving the heart with a constant maximum stroke volume. The cardiac output is regulated according to Starling's law by adjusting the frequency according to the venous return.
Animals↗
The Windkesselventricle with guiding balloon as a new approach for assisted circulation.
A simple method was developed to aid the patient with low cardiac output syndrome following cardiac surgery. The concept was shown to be feasible in electric circulatory analog studies and verified in 20 dog experiments. A Dacron graft (end-to-side) through the right second intercostal space connects the ascending aorta to the subcutaneously implanted, ellipsoidal-shaped artifical ventricle. A spherical polyurethane balloon is positioned in the aorta distal to the Dacron graft via the femoral artery. The ventricle and balloon are pneumatically driven synchronously with the ECG. In natural systole the balloon is inflated, occluding the aorta, and the artificial ventricle sucks the entire stroke volume. In natural diastole the balloon deflates and the artificial ventricle ejects the blood into the peripheral arteries. With this system it is possible to maintain a normal systemic pressure and have high hemodynamic efficiency. The left ventricular systolic pressure is 85 percent unloaded. The systolic wave is turned 180 degrees to the natural. After treatment, the device can be removed without thoracotomy.
Animals↗