Biomedical subjects

Jorge Silva

Publications and source records attributed to Jorge Silva.

4 recordsLinked to original sources

PubMed2005

A self-contained, mechanomyography-driven externally powered prosthesis.

The measurement of the low-frequency (5-50 Hz) "sounds" or vibrations produced by contracting muscles is termed mechanomyography (MMG). As a control signal for powered prostheses, MMG offers several advantages over conventional myoelectric control, including, nonspecific sensor placement, distal signal measurement, robustness to changing skin impedance, and reduced sensor costs. The objectives of this study were to demonstrate 2-function prosthesis control based on a triplet of distally recorded, normalized root mean square MMG signals and to identify necessary future research toward full clinical implementation of MMG signals in upper-limb externally powered prostheses. A novel self-contained MMG-driven prosthesis for below-elbow amputees was designed, implemented, and preliminarily tested on 2 subjects. This prosthesis was composed of specialized software and hardware modules that emulate a 2-site electromyography sensing system. Although the use of MMG signals for prosthesis control has been shown previously, we report, for the first time, successful control within a self-contained unit in unconstrained environments. Specifically, essential requirements for practical use, such as standardized sensor attachment, basic noise elimination, and miniaturization of the system, have been achieved. Both subjects were able to voluntarily open and close the prosthesis hand with no significant delays from intention to action (approximately 120 ms). Quantitative analyses revealed 88% and 71% control accuracy for subjects 1 and 2, respectively.

Adult↗

PubMed2005

A mathematical model for source separation of MMG signals recorded with a coupled microphone-accelerometer sensor pair.

Recent advances in sensor technology for muscle activity monitoring have resulted in the development of a coupled microphone-accelerometer sensor pair for physiological acousti signal recording. This sensor can be used to eliminate interfering sources in practical settings where the contamination of an acoustic signal by ambient noise confounds detection but cannot be easily removed [e.g., mechanomyography (MMG), swallowing sounds, respiration, and heart sounds]. This paper presents a mathematical model for the coupled microphone-accelerometer vibration sensor pair, specifically applied to muscle activity monitoring (i.e., MMG) and noise discrimination in externally powered prostheses for below-elbow amputees. While the model provides a simple and reliable source separation technique for MMG signals, it can also be easily adapted to other aplications where the recording of low-frequency (< 1 kHz) physiological vibration signals is required.

Acceleration↗

PubMed2004

[Management of gallbladder cancer with invasion of the muscular layer].

BACKGROUND: Gallbladder cancer is the leading cause of death of cancer among women in Chile. Detection of early forms of the disease during the pathological study of the cholecystectomy specimen is common. The management of these cases, specially those with invasion of the muscular layer is under discussion. AIM: To analyze the clinical features of patients with gallbladder cancer and muscular layer invasion and their prognosis after a simple cholecystectomy. PATIENTS AND METHODS: We studied a series of 46 patients with gallbladder cancer and invasion of the muscular layer. In the majority of cases diagnosis was performed at the moment of specimen study. Eleven patients underwent reoperation. Of these, ten underwent lymphadenectomy and liver resection while one patient underwent resection of the cystic duct stump. RESULTS: During follow up, five patients died as a consequence of gallbladder cancer. Overall survival was 78%, with no differences between patients subjected or not a new operation. CONCLUSIONS: Gallbladder cancer with muscular infiltration has a good prognosis, independent of the type of therapy.

Adult↗

PubMedDate not supplied

Management of common bile duct stones: the state of the art in 2000.

Biliary lithiasis is a widespread disease all over the world; one-third of the white population presents with stones in the biliary ducts. In Chile, it is present in 47% of adult females. The most common complications of this pathology are acute cholecystitis, choledocholithiasis, acute pancreatitis, retained common bile duct (CBD) stones, and gallbladder cancer; these constitute a serious health problem in Chile. The aim of this study was to update the information related to choledocholithiasis after 10 years of laparoscopic biliary surgery. To achieve this objective, we retrospectively analyzed the last 100 cases of choledocholithiasis admitted to the University of Chile Clinical Hospital in 2000. Prevalence by sex and age was determined. Clinical diagnosis was demonstrated to be effective in 92.3% of the cases; laboratory tests and ultrasound were effective in 81% and 90% of the cases, respectively. Diagnosis of cholelithiasis and choledocholithiasis as one unique entity corresponded to 53% of the sample; 47% of the remaining choledocholithiasis cases corresponded to retained CBD stones in patients previously cholecystectomized. Time of appearance of symptoms of this residual pathology was reviewed. All methods or procedures employed to treat this pathology were studied, and it was found that endoscopic cholangiography (ERCP) was the most frequently used procedure. Also, results of other alternative procedures, such as open surgery or ERCP combined with laparoscopic cholecystectomy, were considered. Finally, this study was complemented with a thorough bibliographic review of more than 100 publications on the subject that were published in high-impact surgical reviews, emphasizing the course of treatment followed during the last 7 years.

Cholangiopancreatography, Endoscopic Retrograde↗