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G N C Kenny - One of the best experts on this subject based on the ideXlab platform.

  • prediction of movement at laryngeal mask airway insertion comparison of auditory evoked potential index bispectral index spectral edge Frequency and Median Frequency
    BJA: British Journal of Anaesthesia, 1999
    Co-Authors: Matsuyuki Doi, H. Mantzaridis, Roger Gajraj, G N C Kenny
    Abstract:

    We have studied 46 patients to compare the efficacy of the auditory evoked potential (AEP) index, bispectral index (BIS), 95% spectral edge Frequency (SEF) and Median Frequency (MF) in predicting movement in response to insertion of the laryngeal mask airway (LMA). Anaesthesia was induced with target-controlled infusions of propofol and alfentanil. After loss of eyelash reflex and adequate jaw relaxation, the LMA was inserted without the assistance of a laryngoscope or neuromuscular blocker. Patients who showed any visible spontaneous muscle movement within 1 min of LMA insertion were defined as movers. Values in movers and non-movers at 30 s before LMA insertion were analysed. Only AEP index discriminated between movers and non-movers with a prediction probability of 0.872. BIS, SEF and MF could not predict movement at LMA insertion. AEP index was the most reliable predictor of movement in response to LMA insertion.

  • relationship between calculated blood concentration of propofol and electrophysiological variables during emergence from anaesthesia comparison of bispectral index spectral edge Frequency Median Frequency and auditory evoked potential index
    BJA: British Journal of Anaesthesia, 1997
    Co-Authors: Roger Gajraj, H. Mantzaridis, G N C Kenny
    Abstract:

    We studied four electrophysiological variables (bispectral index (BIS), 95% spectral edge Frequency (SEF), Median Frequency (MF) and auditory evoked potential index (AEP index) in 10 patients during emergence from anaesthesia. We compared correlation of the signals with gradually decreasing calculated blood propofol concentrations, and evaluated the signal differences between preinduction and emergence from anaesthesia. Values of BIS, MF and SEF correlated with calculated blood concentrations of propofol during emergence from anaesthesia. The correlation was best with BIS, but was poor with MF and SEF at low calculated blood propofol concentrations. Although AEP index values did not correlate with calculated blood concentrations of propofol during emergence from anaesthesia, values after eye opening and before anaesthesia were well distinguished from those during emergence from anaesthesia. BIS correlated best with calculated blood concentrations of propofol. AEP index appeared to distinguish the awake from asleep state.

Emmanuel Tetteh - One of the best experts on this subject based on the ideXlab platform.

  • effect of surgical radiation personal protective equipment on emg based measures of back and shoulder muscle fatigue a laboratory study of novices
    Applied Ergonomics, 2020
    Co-Authors: Pramiti Sarker, Emmanuel Tetteh, Caleb Radley, Susan M Hallbeck, Gary A Mirka
    Abstract:

    Abstract Interventional radiologists are at increased risk for musculoskeletal discomfort/disorders and this has been linked to the use of radiation personal protective equipment (rPPE). This study examined the effects of rPPE on the development of fatigue of the erector spinae and trapezius muscles. Surface electromyography (EMG) was used to capture muscle activity, and both time domain (average rectified value) and Frequency domain (Median Frequency) measures were considered in the assessment of localized muscle fatigue. Sixteen participants performed a simulated surgical procedure requiring intermittent 30° flexed static trunk posture with and without rPPE on separate days. The results showed that the rPPE condition demonstrated significantly greater (p

Gary A Mirka - One of the best experts on this subject based on the ideXlab platform.

Serge H Roy - One of the best experts on this subject based on the ideXlab platform.

  • time Frequency parameters of the surface myoelectric signal for assessing muscle fatigue during cyclic dynamic contractions
    IEEE Transactions on Biomedical Engineering, 2001
    Co-Authors: Paolo Bonato, Serge H Roy, Marco Knaflitz, C J De Luca
    Abstract:

    The time-dependent shift in the spectral content of the surface myoelectric signal to lower frequencies has proven to be a useful tool for assessing localized muscle fatigue. Unfortunately, the technique has been restricted to constant-force, isometric contractions because of limitations in the processing methods used to obtain spectral estimates. A novel approach is proposed for calculating spectral parameters from the surface myoelectric signal during cyclic dynamic contractions. The procedure was developed using Cohen class time-Frequency transforms to define the instantaneous Median and mean Frequency during cyclic dynamic contractions. Changes in muscle length, force, and electrode position contribute to the nonstationarity of the surface myoelectric signal. These factors, unrelated to localized fatigue, can be constrained and isolated for cyclic dynamic contractions, where they are assumed to be constant for identical phases of each cycle. Estimation errors for the instantaneous Median and mean Frequency are calculated from synthesized signals. It is shown that the instantaneous Median Frequency is affected by an error slightly lower than that related to the instantaneous mean Frequency. In addition, the authors present a sample application to surface myoelectric signals recorded from the first dorsal interosseous muscle during repetitive abduction/adduction of the index finger against resistance. Results indicate that the variability of the instantaneous Median Frequency is related to the repeatability of the biomechanics of the exercise.

  • effects of muscle fiber type and size on emg Median Frequency and conduction velocity
    Journal of Applied Physiology, 1995
    Co-Authors: E Kupa, Serge H Roy, S C Kandarian, C J De Luca
    Abstract:

    This paper describes an in vitro method for comparing surface-detected electromyographic Median Frequency (MF) and conduction velocity (CV) parameters with histochemical measurements of muscle fiber type composition and cross-sectional area (CSA). Electromyographic signals were recorded during electrically elicited tetanic contractions from rat soleus, extensor digitorum longus, and diaphragm muscles placed in an oxygenated Krebs bath. Fibers were typed as slow oxidative, fast oxidative glycolytic, and fast glycolytic based on histochemical enzyme stains. Muscles with a greater percentage of fast glycolytic and fast oxidative glycolytic fibers exhibited greater initial values of MF and CV as well as a greater reduction in these variables over the course of the contraction. Regression indicated that fiber type composition could be predicted based on two MF parameters. A weighted measure of muscle fiber CSA was found to be linearly related to both initial MF and CV. The results of this study suggest that MF and CV parameters recorded during a muscular contraction are related to muscle fiber type composition and muscle fiber CSA.

  • spectral electromyographic assessment of back muscles in patients with low back pain undergoing rehabilitation
    Spine, 1995
    Co-Authors: Serge H Roy, M Emley, Carlo J De Luca, Rudi J C Buijs
    Abstract:

    STUDY DESIGN A surface electromyographic procedure for evaluating back muscle impairment was studied in patients undergoing rehabilitation for low back pain. OBJECTIVES The results were analyzed to determine whether the electromyographic procedure was able to: 1) distinguish muscle impairment between patients with low back pain and normal subjects, and 2) monitor changes in muscle function after low back pain rehabilitation. METHODS Patients with chronic low back pain (n = 85) were tested to measure the Median Frequency of the electromyographic signals from six lumbar electrode sites during sustained trunk extensions. A subset (n = 28) of these patients was re-tested after low back pain rehabilitation. A discriminant function for classifying subjects into "low back pain" and "normal" groups was formulated using the electromyographic data from a subset of the patients with low back pain (n = 28) and a normative sample (n = 42). Results for this "learning" sample were compared with results using the same function on the remaining "holdout" sample of patients (n = 57) and an additional normative sample (n = 6). Differences in electromyographic parameters before and after rehabilitation also were analyzed. RESULTS The discriminant function classified subjects into low back pain and normal groups, with 86% and 89% correct classification for the "learning" and "holdout" samples, respectively. These classification results were independent of trunk extensor strength. Changes in Median Frequency after the rehabilitation program were consistent with improvements in back muscle fatigability. CONCLUSION These findings demonstrate how electromyographic spectral measurements may be used to identify and monitor back muscle impairment in patients undergoing rehabilitation for low back pain.

Roger Gajraj - One of the best experts on this subject based on the ideXlab platform.

  • prediction of movement at laryngeal mask airway insertion comparison of auditory evoked potential index bispectral index spectral edge Frequency and Median Frequency
    BJA: British Journal of Anaesthesia, 1999
    Co-Authors: Matsuyuki Doi, H. Mantzaridis, Roger Gajraj, G N C Kenny
    Abstract:

    We have studied 46 patients to compare the efficacy of the auditory evoked potential (AEP) index, bispectral index (BIS), 95% spectral edge Frequency (SEF) and Median Frequency (MF) in predicting movement in response to insertion of the laryngeal mask airway (LMA). Anaesthesia was induced with target-controlled infusions of propofol and alfentanil. After loss of eyelash reflex and adequate jaw relaxation, the LMA was inserted without the assistance of a laryngoscope or neuromuscular blocker. Patients who showed any visible spontaneous muscle movement within 1 min of LMA insertion were defined as movers. Values in movers and non-movers at 30 s before LMA insertion were analysed. Only AEP index discriminated between movers and non-movers with a prediction probability of 0.872. BIS, SEF and MF could not predict movement at LMA insertion. AEP index was the most reliable predictor of movement in response to LMA insertion.

  • relationship between calculated blood concentration of propofol and electrophysiological variables during emergence from anaesthesia comparison of bispectral index spectral edge Frequency Median Frequency and auditory evoked potential index
    BJA: British Journal of Anaesthesia, 1997
    Co-Authors: Roger Gajraj, H. Mantzaridis, G N C Kenny
    Abstract:

    We studied four electrophysiological variables (bispectral index (BIS), 95% spectral edge Frequency (SEF), Median Frequency (MF) and auditory evoked potential index (AEP index) in 10 patients during emergence from anaesthesia. We compared correlation of the signals with gradually decreasing calculated blood propofol concentrations, and evaluated the signal differences between preinduction and emergence from anaesthesia. Values of BIS, MF and SEF correlated with calculated blood concentrations of propofol during emergence from anaesthesia. The correlation was best with BIS, but was poor with MF and SEF at low calculated blood propofol concentrations. Although AEP index values did not correlate with calculated blood concentrations of propofol during emergence from anaesthesia, values after eye opening and before anaesthesia were well distinguished from those during emergence from anaesthesia. BIS correlated best with calculated blood concentrations of propofol. AEP index appeared to distinguish the awake from asleep state.