Biomedical subjects

J Rosell

Publications and source records attributed to J Rosell.

At least 37 records · Page 2Linked to original sources

PubMed1996

Electrical impedance tomography of the eye: in vitro measurements of the cornea and the lens.

This study was designed to perform multifrequency impedance measurements on the pig's eye. On one hand, impedance of the ocular tissues was measured from 10 kHz to 10 MHz. The aqueous and vitreous humours and the cornea showed no relaxation in this range of frequencies, whereas the lens and its parts (the cortex and the nucleus) did. On the other hand, multifrequency EIT and dynamic imaging were performed on the lens and on the whole eye. Data and images obtained after thermal and chemical injuries are presented and discussed.

Animals↗

PubMed1996

Homozygous myotonic dystrophy: clinical and molecular studies of three unrelated cases.

We report the clinical and molecular study of three unrelated homozygous myotonic dystrophy patients. In the first family, the homozygous patient shows the classical form of the disease with two DM alleles of very different expansion sizes (1000 and 60 repeats). In the second family, the homozygous patient is mildly affected and carries a minimally expanded allele (64 repeats) and a "normal" allele (38 repeats) that increases in size when transmitted. Such an intergenerational expansion of an allele in this range of repeats has not been reported to date. The third homozygous case has late onset bilateral cataracts as the only symptom. She has two minimally expanded alleles (51 and 120 repeats) that showed different intergenerational enlargement during transmission to the next generation.

Adult↗

PubMed1995

Acute otitis media in childhood: a study of 20,532 cases.

We present a study of acute otitis media among 20,532 Spanish children during a 6-month period from January through June 1991. The study was done by distributing a questionnaire to all Spanish pediatricians. Of the patients 51.7% were girls and 48.3% boys; 68.7% of all children were younger than 5 years. The most frequent symptoms were otalgia or irritability, 92.7%; fever, 63.5%; otorrhea, 24.9%; vomiting, 21.4%; and another concomitant upper respiratory tract infection, 65.5%. Otitis was bilateral in 45.6% of the cases. The most frequently used antibiotic was cefixime (38%), followed by amoxicillin-clavulanate (22.2%), amoxicillin (15.3%), 2nd-generation cephalosporins (13.5%) and macrolides (8.8%). In 11.8% of the patients, a change in the initial antibiotic therapy was required due to adverse effects. Resolution of symptoms occurred in 77.8% of the patients.

Acute Disease↗

PubMed1995

Multi-frequency static imaging in electrical impedance tomography: Part 1. Instrumentation requirements.

Static images of the human body using electrical impedance tomography techniques can be obtained by measuring at two or more different frequencies. The frequencies used depend on the application, and their selection depends on the frequency behaviour of the impedance for the target tissue. An analysis using available data and theoretical models for tissue impedance yields the expected impedance and boundary voltage changes, therefore setting the measurement instrument specifications. The instrument errors produced by different sources are analysed, and, from this analysis it is possible to determine the feasibility of building the instrument, the limit values for some parameters (or components) and indications on the most suitable design of critical parts. This analysis also shows what kinds of error can be expected in the reconstructed images. It is concluded that it is possible to build an instrument with limited errors, allowing static images to be obtained. An instrument has been built that meets some of the design requirements and fails in others because of technological problems. In vivo images obtained with this instrument will be presented in Part 2 of this work.

Electric Impedance↗

PubMed1995

Errors in prolonged electrical impedance measurements due to electrode repositioning and postural changes.

Long-term electrical impedance measurements are affected by specific errors. Electrode failure, changes in its impedance due to aging, and postural changes are among the most important. We analyse errors due to electrode replacement and body postural changes. Electrode replacement errors can cause impedance changes up to 5% of basal value. This is one of the most important factors in data reproducibility. Body postural changes also contribute to impedance variations. We have proposed the use of a reference position to carry out impedance measurements as the one that shows the smallest impedance sensitivity to postural changes. In general, we observed that this is achieved with arms and legs slightly separated from the body. We propose the use of a ratio of impedance at two different frequencies to discern the origin of impedance changes, whether from physiological phenomena or postural errors.

Adult↗

PubMed1995

A multifrequency multichannel electrical impedance data acquisition system for body fluid shift monitoring.

This paper discusses some important issues for the design of electrical impedance measurement systems intended for body fluid shift monitoring, in particular during dialysis treatments. We have studied two common signal generation systems: digital synthesis and carrier recovery. We have found that in prolonged measurement applications, digital synthesis yields the best performance. On the demodulation side, we balance the demodulator errors between the real and imaginary parts by rotating the demodulation axes. We use segmental multifrequency impedance measurements to estimate the values of intracellular and extracellular impedance by adjusting the parameters of a Cole-Cole model for each segment measured. We stress the need to perform segmental measurements in order to accurately measure the segments of interest, in particular the trunk during dialysis treatments. Our results show that there is a sharp disequilibrium between the intracellular and extracellular compartments in the very first dialysis period. This fact generates the need to continuously measure segmental impedance instead of comparing initial and final values.

Body Fluid Compartments↗

PubMed1995

Signal-to-motion artifact ratio versus frequency for impedance pneumography.

We measured transthoracic impedance between 12.5 and 185 kHz in nine adults. We used a system with two impedance channels, both simultaneously detecting the real part of impedance at two different frequencies. We used only two electrodes in the midaxillary line, connecting both channels in parallel. The amplitude relation between the two channels was measured for different maneuvers and frequencies. Results show for normal breathing an increase of the signal of 20% and a decrease in motion artifacts from 12.5 to 185 kHz. We conclude that, for the maneuvers studied, it is better to work at higher frequencies than the ones commonly used. Also, we suggest a method to further increase the signal-to-motion artifact ratio based on measurement at two frequencies.

Adult↗

PubMed1995

Reduction of motion artifacts using a two-frequency impedance plethysmograph and adaptive filtering.

We measured transthoracic impedance in nine presumed healthy adult subjects with a two-frequency plethysmograph at 57 kHz and 185 kHz. The measurement protocol included periods of normal breathing without motion and periods of motion without breathing. We analyzed the cross-correlation and the ratio between the signals at both frequencies for all the different maneuvers. The correlation coefficient was between 0.97 and 1 for breathing, the minimal cross-correlation (0.81) was for simulated obstructive apnea. We found that the amplitude ratio between the two-frequency signals was different for normal breathing and for motion. Based on these results, we designed and tested an adaptive filter to increase the signal-to-artifact ratio (SAR). The increase in SAR (mean +/- standard deviation) compared with the signal at 57 kHz was: 183% +/- 117% for arm movement, 133% +/- 93% for leg movement, and 34% +/- 62% for simulated obstructive apnea.

Adult↗

PubMed1995

Clinical, neuropathologic, and genetic studies of a large spinocerebellar ataxia type 1 (SCA1) kindred: (CAG)n expansion and early premonitory signs and symptoms.

We report the clinical, neuropathologic, and genetic studies of a large kindred (family M-ADCA1) with autosomal dominant spinocerebellar ataxia type 1 (SCA1), ascertained in 41 members, with clinical data available in twenty-two. The mean age of onset was 36.3 +/- 6.2 years (ages, 26 to 52), the mean duration of the disease was 15.8 +/- 6.5 years (range, 10 to 28 years), and the mean age at death was 54.1 +/- 9.5 years (ages, 39 to 72). Premonitory signs and symptoms appeared earlier than the usual onset symptoms in many of the clinically unaffected patients who inherited the mutated SCA1 gene. Anticipation was present when we compared the seventh and eighth generations. A more severe course of the disease occurred in offspring of affected males. Neuropathologic examination, performed on three patients, showed the usual findings of SCA1; Golgi and immunocytochemistry studies suggested primary damage of the Purkinje cells. We analyzed the CAG-repeat mutation responsible for the SCA1 phenotype in a total of 41 family members. There was expansion in 19 subjects (10 clinically affected, seven with early signs and symptoms, and two asymptomatic individuals), and all showed heterozygosity, with one allele between 41 and 59 repeats (SCA1 mutation) and the other in the range of 6 to 39 repeats (normal range). The clinical analysis of "at risk" patients with the SCA1 mutation showed that minor signs and symptoms begin before full clinical diagnosis, and these premonitory manifestations can herald full development of SCA1 by years.

Adult↗

PubMed1994

A wide-band AC-coupled current source for electrical impedance tomography.

A current source suitable for application in electrical impedance tomography (EIT) is described. The first stage of the commercially available current-feedback amplifier AD844 constitutes a current-conveyor implementation and allows the construction of wide-bandwidth current sources, thus avoiding the mismatching and temperature-induced problems that arise in discrete realizations. The lack in gain accuracy of this circuit is overcome by the inclusion of its input buffer in an operational amplifier (op amp) feedback loop. Saturation problems that appear when placing a DC-blocking capacitor between the source and the electrode are solved by a DC feedback that maintains DC voltage at the output near to 0 V without reducing the output impedance of the source. Two AC-coupled current sources, in both inverting and non-inverting configurations, are described and their possible applications to EIT are listed.

Amplifiers, Electronic↗

PubMed1993

Presymptomatic analysis of spinocerebellar ataxia type 1 (SCA1) via the expansion of the SCA1 CAG-repeat in a large pedigree displaying anticipation and parental male bias.

Autosomal dominant cerebellar ataxia type 1 (ADCA1) is a clinical and genetic heterogeneous neurodegenerative disorder which leads to progressive cerebellar ataxia. One defective gene responsible for the disease was first localised to 6p (SCA1, spinocerebellar ataxia type 1) and the mutation has been more recently characterised. We have analysed the CAG-repeat mutation responsible for the SCA1 phenotype in a large Spanish kindred with 41 affected members, in which positive linkage with D6S89 was previously shown. All (10) clinically affected members analysed were heterozygous with one disease allele being between 41 to 57 CAG repeats, and the other in the normal range, from 6 to 39 repeats. Nine clinically unaffected individuals who were between the ages of 18 and 40, were found to have expansions of the CAG repeat (41 to 59), and 22 other 'at risk' individuals were found to have inherited the SCA1 gene with copies of the CAG repeat in the normal range. We have also observed that affected fathers passed on the mutated SCA1 gene with larger increases in the number of CAG repeats than affected mothers did. In one case a decrease in the number of CAG repeats (51 to 50) was detected in the transmission from the affected mother, and in two cases no change was observed in the transmission of a 41 allele repeat by a mother. As in the other disorders in which knowledge of the mutation has been obtained, analysis of the repeat expansion dramatically changes diagnosis of SCA1.

Adolescent↗

PubMed1992

Common-mode feedback in electrical impedance tomography.

When a current is injected into a body, in addition to the voltage profile developed on the surface, a common-mode voltage (CMV) which produces errors in the measurement also appears. The great accuracy needed to reconstruct images in electrical impedance tomography (EIT) requires the use of differential amplifiers with a high common-mode rejection ratio (CMRR) to avoid this error. Nevertheless, the effective CMRR is lower than the differential amplifier ratio due to mismatches in the electrode impedances and other circuits in the measurement channel. The use of common-mode feedback (CMFB) is an alternative to reducing the error produced by the CMV. The stability of the feedback loop is analysed for a broadband system. Simulation and experimental results show that it is possible to obtain an improvement of 40 dB in the measurements at frequencies of up to 10 kHz.

Electric Conductivity↗

PubMed1992

A broadband system for multifrequency static imaging in electrical impedance tomography.

A widely accepted method for static imaging in electrical impedance tomography (EIT) is to measure at two frequencies. The choice of measurement frequencies is application-dependent because some different tissues cannot be distinguished when using two fixed frequencies. We have developed a system that generates signals from 8-10(3) kHz and applies two of these signals simultaneously to the body through a broadband current mirror. Great care has been taken in the design of the current injection multiplexer in order to keep the current source output capacitance as low as possible. Furthermore design of the layout of the patient interface board, in order to reduce feedthrough capacitances, also needs great care. Other parameters for driving and detection sections have been designed according to our results from FEM and circuit simulations including skin and electrode effects. Simulations using FEM with available tissue impedance data and preliminary measurements in a discrete phantom show that static imaging is possible for both the real and imaginary parts of the impedance.

Electric Conductivity↗

PubMed1992

Effects of growth hormone in patients receiving total parenteral nutrition following major gastrointestinal surgery.

The purpose of the present study was to determine whether the administration of a biosynthetic human growth hormone was capable of enhancing the efficacy of total parenteral nutrition. Patients (n = 38) who had undergone major gastrointestinal surgery were randomly divided into two groups. Group I (n = 20) treated only with PN, and Group II (n = 18) treated as in Group I plus human growth hormone (4 IU daily). Our study shows that the administration of human growth hormone produces a statistically significant increase in serum levels of growth hormone, somatomedin-C, transferrin, albumin and total proteins. It also causes a positive nitrogen balance from the first 24 hours onward. These findings suggest that the administration of human growth hormone produces an increase in protein synthesis, perhaps through somatomedin-C as mediator.

Adult↗

PubMed1992

[Effect of growth hormone and parenteral nutrition on the catabolic phase following major digestive surgery].

The purpose of the present study was to determine if the administration of a biosynthetic human growth hormone (bGH) was able to enhance the efficacy of total parenteral nutrition (PN). Patients (n = 38) who had undergone major gastrointestinal surgery were randomly divided in two groups. Group I (n = 20) treated only with PN and Group II (n = 18) treated as in Group I plus bGH (4 UI/daily). Our study shows that the administration of bGH produces a significant increase in serum levels of growth hormone and Somatomedin-C. It also caused a positive nitrogen balance from the first 24 hours on (p less than 0.01). In Group II on day 12 after operation a statistically significant increase in transferrin (p less than 0.05), albumin (p less than 0.01) and total proteins (p less than 0.02) was observed. Our study suggest that the administration of bGH produces, perhaps through Somatomedin-C as mediator, an increase in protein synthesis.

Adult↗

PubMed1991

[Echinococcosis of the spleen. Its conservative surgical treatment].

Echinococcosis cysts in the spleen are very rare, even in endemic areas. We report here on 4 patients (0.5% of the total number of cases of echinococcosis disease) who have been treated in the University Hospital Granada from 1970 to 1990. Formerly, splenectomy was for most surgeons the recommended surgical procedure. From 1980, however, most authors have rejected such a radical procedure and most now recommend conservative surgery of the spleen. We have always followed this conservative procedure, as of course in cases of liver echinococcus, that is: cyst enucleation and marcupialisation (Posadas-Dew method), if there are no cyst complications. And in cases of infected or suppurating cysts we used drainage-marsupialisation. We have obtained very good results: no mortality was recorded.

Adolescent↗

PubMed1990

[Intraoperative autotransfusion in massive hemorrhage following thoracic-abdominal trauma].

In the University Hospital of Granada (Spain), 359 surgical trauma patients underwent intraoperative autotransfusion. The patients were divided into 2 groups, according to their blood loss: group I (blood loss less than or equal to 2000 ml) and group II (blood loss greater than 2000 ml). Patients from group I did not require homologous blood transfusion. So the high risk involved in this type of transfusion was avoided. Macroscopic haemoglobinuria was only found in those patients where the Solcotrans, Viavae type of autotransfusion system was used; with the Bentley ATS system, no macroscopic haemoglobinuria was registered. With patients from group II, however, that is, those with a blood loss of more than 2000 ml, we had to fall back on homologous transfusion in addition to retransfusing autologous blood. When the transfusion exceeds 4000 ml there is increasing bleeding, which requires treatment with fresh frozen plasma, platelets and/or fibrinogen. The mortality rate of patients in group II was very high but the patients died from the severity of their injuries or from postoperative complications which were not due to autotransfusion in itself with the exception of 3 patients who underwent massive autotransfusion (12,000 to 25,000 ml) and died from acute renal failure. The main indication for intraoperative autotransfusion is without doubt abdominal and thoracic trauma which lead to high blood loss.

Abdominal Injuries↗

PubMed1990

Two-frequency impedance plethysmograph: real and imaginary parts.

A four-channel impedance plethysmograph has been designed. Impedance signals are obtained at two frequencies by measuring both real and imaginary parts. Particular attention has been paid to the sine wave generation circuits that provide system versatility. The required phase-sensitive demodulation is achieved by means of analogue multiplexers. Results show that there are significant variations in the thoracic equivalent capacitance related to respiration and that there is an increased sensitivity to cardiac activity at low frequencies.

Analog-Digital Conversion↗