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Biomedical subjects

R Navarro

Publications and source records attributed to R Navarro.

116 records · Page 7Linked to original sources
PubMedDate not supplied

Study of heat dissipation to the lung from a thermal ventricular assist system.

The thermally powered left ventricular assist system (LVAS) requires that heat be dissipated to surrounding lung tissue and blood. This acute study was conducted in three anesthetized calves (weighing 84.3 +/- 14.3 kg) to evaluate the mechanisms involved in the dissipation of heat to the lung tissue. The heaters were placed in contact with the left lung surface and skeletal muscle tissue. Compared to the muscle tissue, heat flux to the lung was approximately three times higher for the same surface temperatures. For a constant heat flux, lung interface temperature tended to vary inversely with the cardiac output and ventilatory flow. This preliminary study demonstrated that the level of heat generated by the thermal LVAS can be effectively dissipated to the lung, with the convection mechanisms of airflow and blood flow playing a major role.

Animals↗
PubMedDate not supplied

Objective quantification method for measuring in vivo accumulated dental plaque.

Dental plaque was collected, dried, and weighed on a gold insert that fit into the buccal aspect of a posterior crown. The plaque weight was determined by calculating the difference between the postcollection insert weight and the precollection insert weight. This system for measurement of the dry weight of in vivo accumulated dental plaque was found to be a practical means of plaque quantification.

Adult↗
PubMedDate not supplied

The results of conservative management of juvenile osteochondritis dissecans using joint scintigraphy. A prospective study.

A prospective clinical study used joint scintigraphy to investigate conservative treatment of juvenile osteochondritis dissecans (JOCD) of the femoral condyle. The predictive value of scintigraphic evaluation and various parameters (age at onset, sex, location and size of lesion) were analyzed. Over a 10 year period, the senior author followed 92 knees in 76 patients, 60 of whom were male and 16 female (11 and 5 bilaterals, respectively). All patients were participants in athletics or exercise programs. All patients had orthopaedic assessment, roentgenographic studies (AP, lateral, and tunnel views), 99m-Technetium phosphate compound joint scintigraphy, and instruction in a symptom-free existence (with all athletic activity proscribed). Patients were reevaluated and scanned every 8 weeks. No casts or braces were used, although crutches were sometimes necessary to maintain symptom-free levels. Based on specific indications for failure of conservative treatment, 50% of these patients failed and underwent surgery. Of the 92 knees, 52 were successfully treated conservatively, while 40 failed. Average followup was 4.2 years. Average age at onset was 12.5 years; the success group averaged 12.1 years and the failure group 13.0 years. The average lesion size was 363.2 mm2, with 309.5 mm2 in the success group and 436.0 mm2 in the failure group. Parameters of location, sex, and scan classification were not statistically significant as predictive factors. This study found no predictors for the success or failure of treatment beyond a moderate correlation of larger lesion size with failed conservative treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

An intrathoracic left ventricular assist system: utilization of results from a development program.

An intrathoracic, electrohydraulically actuated, left ventricular assist system (LVAS) was subjected to formal device readiness testing. Endurance testing was initiated on eight systems before testing was halted due to failure of four of the systems. Three failed due to environmental leakage. Solutions were straightforward, involving gasket changes and o-ring resizing. The fourth failure involved a magnetic coupling piston swelling and seizing. The failure was attributed, after long investigation, to hydrogen adsorption by the samarium-cobalt magnets. An unknown number of coupling magnets were affected in this fashion, necessitating complete replacement of magnets to resolve the problem. However, this was beyond the scope of the program, and no further endurance testing was accomplished. The test experience of the Nimbus/CCF LVAS has demonstrated all functional aspects of the complete LVAS, both in vitro and in vivo, and the endurance and reliability potential is indicated as well. Although the LVAS program is currently inactive, its legacy of technical innovations continue to drive the development of other medical devices.

Animals↗
PubMedDate not supplied

Flow visualization in an artificial heart using diffuse and planar laser lighting.

The purpose of the study was to characterize flow properties within a clinical pusher plate type artificial heart. Dual camera video tape and synchronized still photographs were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was turned into a plane of light with a thickness varying from 0.1 to 10 mm, and magnesium oxide and Amberlite particles were used as tracers. Qualitative and quantitative analyses were performed by the examination and digitization of flow patterns. Inflow, outflow, pneumatic drive and after-load pressure, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. Trajectories were then digitized, and velocities, turbulence, and shear stresses were calculated. As the result of these experiments, disturbed, recirculating, and stagnation zones were identified and global and local turbulence values were determined. Simultaneous turbulence, stasis, recirculation, and laminar flow patterns were observed during most phases of the pumping cycle. Velocities obtained varied from 2 cm/sec to 145 cm/sec; total local shear stresses of 12 to 897 dynes/cm2 were seen.

Blood Flow Velocity↗