Power requirements for vibrotactile piezo-electric and electromechanical transducers.

Human-machine information transfer through tactile excitation has addressed new applications in virtual reality, robotics, telesurgery, sensory substitution and rehabilitation for the handicapped in the past few years. Power consumption is an important factor in the design of vibrotactile displays, because it affects energy needs and the size, weight, heat dissipation and cost of the associated electronics. An experimental study is presented on the power required to reach tactile thresholds in electromechanical and piezo-electric transducers. Three different waveforms are considered, with an excitatory period formed by a burst of rectangular 50% duty cycle pulses (R50), rectangular low duty cycle pulses (RLO) and sinusoidal pulses (SIN). Ten different pulse repetition periods (RPs) were considered in the range 1/550-1/25 s. The voltage and current waveforms applied to the transducers at sensation thresholds in a group of 12 healthy subjects were sampled and stored in a digital oscilloscope. The average power was determined for each subject, and differences of two orders of magnitude were measured between the electromechanical and the piezo-electric transducer power consumption. Results show that, for the electromechanical transducer, a smaller power consumption of 25 microW was determined for RP = 1/25 s and the RLO waveform. In the case of the piezo-electric transducer, power of 0.21 microW was determined for SIN excitation and RP = 1/250 s. These results show the advantages of reducing power requirements for vibrotactile displays, which can be optimised by the choice of appropriate types of transducer, excitatory waveforms and pulse repetition periods.

Thoracoabdominal wall repair with glutaraldehyde-preserved bovine pericardium.

Glutaraldehyde-preserved bovine pericardium (GPBP) is evaluated as a bioprosthesis for the reconstruction of surgical defects in the thoracoabdominal wall. The mechanical properties of bovine pericardium preserved at different concentrations of glutaraldehyde were studied. Samples preserved in 0.5% glutaraldehyde showed a significantly higher tensile strength (11.7 +/- 0.8 N/mm2) than samples preserved in 2.5, 5, or 10% (similar to pericardium preserved in normal saline). The percentage of elongation was significantly lower than samples preserved in 1, 2.5, and 5% glutaraldehyde. GPBP at 0.5% was used to repair experimentally induced defects of the abdominal wall (n = 9), chest wall (n = 6), diaphragm (n = 6), and sternum (n = 7). All animals presented adequate tolerance to the material used and no case of infection or rejection of the material was seen in any of the animals. Finally, 0.5% GPBP was used clinically in a series of 40 patients: postincisional abdominal hernia (n = 30), inguinal hernia (n = 8), diaphragmatic hernia (n = 1), and congenital pelvic defect with prolapse of abdominal organs (n = 1). Surgical use showed that GPBP was a very manageable material and long-term results were good in 37 patients with a mean follow up of 18 months (range 5-35 months). Six patients presented seroma formation (all abdominal hernia patients), three of which eventually developed infection and had the GPBP patch removed at 3, 5, and 7 months postoperatively. The rest of the patients presented good scar formation with adequate resistance at the area of implantation. GPBP is a biological material with sufficient resistance to be used surgically in the repair of thoracoabdominal defects. Ideal concentration of glutaraldehyde to be used in the preparation-preservation of the material is 0.5% since higher concentration negatively affect its tensile rupture strength and elongation.

Anatomía quirúrgica de la distribución arterial en el mesocolon transverso / Surgical anatomy of the arterial distribution in the transverse mesocolon

Se presenta la distribución arterial en el mesocolon transverso encontrado en la disección de 58 fetos frescos de ambos sexos a los cuales se les inyectó vía aorta látex coloreado para la visualización. Se resume la descripción de los textos anatómicos clásicos, se compara con nuestro trabajo y se comunican algunas diferencias y hallazgos entre los que se analiza como algo nuevo la presencia de arterias accesorias de la zona pancreática que no se describen en los textos clásicos

Effect of high-dose cimetidine on pulmonary extravascular water after acute smoke inhalation injury.

An animal model utilizing gamma imaging was used to examine pulmonary edema of an inhalation injury model. Tests were conducted using radiolabeled tracers and a dual indicator dilution technique as well as gravimetric analysis of excised lungs to determine extravascular water formation. The effect of cimetidine (Tagamet, an H2 receptor antagonist) was investigated as a potential agent for reduction of pulmonary edema following inhalation injury. Control groups included no treatment; smoke only; fluids only; and smoke and fluids. These were compared with identical groups given the same treatments but with the addition of cimetidine (100-150 mg/kg body weight intravenously). Fluids administered were 5% body weight intravenous infusions of lactated Ringer's solution over two hours. Results show that pulmonary edema was evidenced in animals given an inhalation injury, and was markedly worsened by fluid resuscitation. Treatment with cimetidine at high doses, either before or after inhalation injury, did not protect the animals from formation of pulmonary edema.

Early detection of extravascular lung water in an inhalation injury animal model.

A rabbit inhalation injury model using a dual tracer radioactive isotope technique (Rowland et al., 1986), has been utilized with small- and medium-sized molecular weight tracers. There is oedema formation at 2 h after smoke inhalation or fluid resuscitation and especially with the combination of inhalation injury and fluid resuscitation [corrected]. This oedema appears to have decreased by 24 h post-injury. There does not appear to be any difference between the small- and medium-sized tracers in the transit times of tracer in the lung vascular compartment. The increases in extravascular water volume have been confirmed by gravimetric analyses of the lungs. Thus the pulmonary oedema in the rabbit animal model is detectable within 2 h post-injury, with a return towards normal values some time within 24 h if fluid challenged for short periods. Fluid resuscitation exacerbates the amount of oedema that developed. The onset of pulmonary oedema may therefore be earlier than previously seen clinically, and fluid resuscitation modifications may be of benefit in smoke inhalation injury.

Smoke inhalation model for lung permeability studies.

The purpose of this project was the development of a small animal model and the use of external gamma imaging for the study of acute post-inhalation permeability changes. New Zealand white rabbits were anesthetized with ketamine and acepromazine IM, intubated, and a catheter placed in an ear artery. Smoke was produced by burning absorbent cotton in a combustion chamber supplied with 10 liters/min of air. Smoke was delivered to a holding chamber, allowed to cool to room temperature, and immediately delivered to the animals via endotracheal tube. Animals were allowed to inhale smoke for 3 sessions of 2 to 3 minutes. Blood samples were collected for the measurement of PO2, PCO2, and COHb. Lungs were removed at 3 to 4 days postinjury and subjected to microscopic histologic analysis. The results of six animal experiments showed a significant inhalation injury. The mean COHb level was 48% (range, 36%-58%). The change in the pre- and post-injury PO2 and PCO2 values were not significant (mean PO2, 66 mm Hg; mean PCO2, 32 mm Hg). Histologic evaluation of the lungs of three animals at 24 hrs postinjury revealed extensive loss of tracheal epithelium extended to many terminal bronchi. Inflammation of surrounding tissue, including edema and increased migration of polymorphonuclear cells, was also present. Analysis of tissue obtained at 10 to 14 days showed reparative reepithelialization of trachea and major bronchi but acute inflammation and loss of intralobar bronchi. Inflammatory exudate extended to adjacent alveoli. In conjunction with the above model we have developed a method for the noninvasive measurement of lung permeability changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mesocolon transverso: estudio preliminar / Transversal mesocolon: preliminary study

1. Trabajo realizado en la disección de 83 cadáveres adultos recién fallecidos. 2. Se estudia la forma que presenta. 3. Se efectúan mediciones en sus diámetros transversal y anteroposterior central. 4. Se analizan su grosor y recargo adiposo. 5. Se analizan su origen y su implantación colónica. 6. Se describe su proyección frente a la columna vertebral. 7. Se compara nuestro trabajo con textos clásicos el cual es muy pobre ya que no describen los parámetros que a nosotros nos interesan. 8. Se analiza la importancia de sus dimensiones en relación a las colostomías transversas. 9. No se incluye el estudio de la vascularización arterial venosa y linfática ni la inervación lo que será motivo de un estudio posterior