Maurício Campelo Tavares

Removing harmonic power line interference from biopotential signals in low cost acquisition systems

This paper presents a new proposal of a very low cost and highly efficient interference canceller to be applied to biomedical signals. The power line reference is obtained from analog to digital conversion while higher harmonics are mathematically estimated by means of trigonometric relations. These signals are processed by an adaptive algorithm in order to suppress harmonic interference. Biomedical acquisition systems that incorporate a conventional adaptive canceller, whose reference signal is sampled from power line, can be easily modified to improve interference suppression without hardware modifications. Real application examples are supplied in order to demonstrate its usefulness in electroencephalographic, electrocardiographic and auditory evoked potential signals.

Validade da prova calórica monotermal em comparação à estimulação bitermal

BACKGROUND the use of monothermal caloric testing as a screening tool for vestibular asymmetry has been considered as an alternative to bithermal caloric testing. AIM to evaluate the effectiveness of monothermal stimulation when compared to bithermal stimulation in the diagnosis of labyrinth asymmetry. METHOD the results of 389 vectoelectronystagmography, performed between 1998 and 2007, were analyzed. Monothermal stimulation at 30°C and 44°C with unilateral weakness (UW) cut-off at 20% and 25% was compared to bithermal stimulation with cut-off at 25% (gold standard). The analysis was aimed at finding which kind of monothermal caloric test (30°C or 44°C) and which kind of cut-off (20% or 25%) presented the highest specificity and sensitivity values in comparison with bithermal caloric testing. RESULTS sensitivity and specificity of monothermal caloric tests were: 84% and 80%, at 30°C with UW at 20%; 78% and 90%, at 30°C with UW at 25%; 81% and 78%, at 44°C with UW at 20%; 76% and 85%, at 44°C with UW at 25%. CONCLUSION monothermal caloric testing with 30°C stimulus presented the highest sensibility and specificity values in comparison to the results obtained with bithermal stimulation. However, no significant difference was observed between such values and those obtained with 44°C stimulus. In all of the analyses, monothermal testing presented low sensitivity. Thus, the abnormal result of bithermal caloric testing might be seen as normal in monothermal stimulation. The use of monothermal testing as a screening tool is better recommended for individuals whose medical history suggests a low probability of vestibular disease.

Vestibular-Evoked Myogenic Potential (VEMP) in the Evaluation of Schistosomal Myeloradiculopathy

Schistosomal myeloradiculopathy (SMR) is the most severe and disabling form of schistosomiasis. The diagnosis is based on clinical, laboratory, and image data. Vestibular-evoked myogenic potential (VEMP) is a neurophysiologic test that assesses the vestibulospinal pathway through acoustic or galvanic stimuli. The aim of this study was to evaluate cervical spinal abnormalities in patients with SMR. Fifty-two subjects were evaluated, of whom 29 had SMR and 30 did not (normal control). Normal VEMP was observed in all volunteers without SMR. Abnormal VEMP was recorded in 34% of the group with SMR. After treatment, abnormal VEMP was found in 80% of those with persistent neurologic abnormalities. VEMP is a functional test, and the alteration may precede image abnormalities. This procedure may be useful for early diagnosis of schistosomal cervical spinal cord involvement.

Vestibular evoked myogenic potential (VEMP) with galvanic stimulation in normal subjects

INTRODUCTION The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. AIM To describe VEMP generated by GVS. METHODS In this cross-sectional clinical study, VEMP was generated by 2 mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. RESULTS SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. CONCLUSION The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.Introduction: The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. Aim: To describe VEMP generated by GVS. Methods: In this cross-sectional clinical study, VEMP was generated by 2mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. Results: SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. Conclusion: The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.

Potencial evocado miogênico vestibular (VEMP) com estímulo galvânico em indivíduos normais

INTRODUCTION The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. AIM To describe VEMP generated by GVS. METHODS In this cross-sectional clinical study, VEMP was generated by 2 mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. RESULTS SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. CONCLUSION The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.Introduction: The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. Aim: To describe VEMP generated by GVS. Methods: In this cross-sectional clinical study, VEMP was generated by 2mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. Results: SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. Conclusion: The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.

Vestibular evoked myogenic potential (VEMP) with galvanic stimulation in normal subjects✩✩Please cite this article as: Cunha LC, Labanca L, Tavares MC, Gonçalves DU. Vestibular evoked myogenic potential (VEMP) with galvanic stimulation in normal subjects. Braz J Otorhinolaryngol. 2014;80:48–53.

INTRODUCTION The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. AIM To describe VEMP generated by GVS. METHODS In this cross-sectional clinical study, VEMP was generated by 2 mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. RESULTS SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. CONCLUSION The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.Introduction: The vestibular evoked myogenic potential (VEMP) generated by galvanic vestibular stimulation (GVS) is related to the vestibulo-spinal pathway. The response recorded from soleus muscle is biphasic with onset of short latency (SL) component around 60 ms and medium latency (ML) component around 100 ms. The first component reflects otolith function (sacule and utricle) and the last deals with semicircular canals. Aim: To describe VEMP generated by GVS. Methods: In this cross-sectional clinical study, VEMP was generated by 2mA/400 ms binaural GVS, frequency of 5-6 ms that was recorded from soleus muscles of 13 healthy adults, mean age 56 years. The subjects remained standing, head turned contralateral to the GVS applied to the mastoid. Thirty GVS were applied to the mastoid in the position cathode right anode left, followed by 30 in inverted position. SL and ML were measured. Results: SL and ML components were recorded from both legs of all participants and were similar. The average of SL component was 54 ms and of ML was 112 ms. Conclusion: The components SL and ML of the VEMP response in soleus were reproducible and are useful measures of vestibular-spinal function.

Neurophysiologic and Cardiac Signals Simulator Based on Microconverter

This paper describes a microconverter-based electronic device developed to simulate auditory evoked potentials of short, middle and long latencies, ECG and electronystagmographic signals. The simulator reproduces real physiologic signals from sampled AEP and ECG waveforms instead of generating them based on equations. The main simulator part is the ADuC841 microconverter (single-cycle 20 MHz 8052 core, FLASH memory and two 12-bit DACs). Called SimPac I, the equipment is portable and easy to operate, being a worthy tool for calibration of AEP, ECG, ENG and VENG systems during manufacture and maintenance. It can also be used in the development and testing of DSP algorithms intended to filter and/or average the above mentioned signals. As result, examples of several waveforms generated by the SimPac I are shown.

Sistema para Ensaio de Funcionalidade de Incubadoras Neonatais

This work presents a prototype based on a microcomputer to assess the performance of newborn incubators in a semi-automatic way. It carries out the tests described by the Section 8 of the NBR IEC 601- 2-19/1999. The developed electronic circuit acquires data from the sensors using a microcontroller. A set of sensors are used: Five for temperature, one for humidity and one for air flow. The sampled data is sent to a PC via Bluetooth. The software running on the PC manages the data sampling, as well as guides the user through the test procedure by means of messages and sound alerts at the end of each stage. The acquired data is shown on the screen and also stored into a database that can be locally or remotely accessed. At the end, the results are presented on a graph where the measurements (temperature, humidity and air flow) performed during the whole test can be seen. The procedure to calibrate the sensors and the tests carried out with the developed system are presented.

Development of a DSC-based Rotary Chair for Oto-neurological Diagnosis

This paper describes the project, test and construction of an automatic rotary chair to be used as human vestibular system stimulator for clinical diagnosis in otorhinolaryngology (ORL). The hardware and software details of this digital signal controller based system are presented, including the software controller and the obtained results. The prototype was considered appropriate for the proposed application and five identical chairs are being used experimentally in Brazilian ORL services.