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Electrical Noise (electrical + noise)

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Medical Sciences50%

Selected Abstracts

Electrical and optical low frequency noises in multimodal vertical cavity surface emitting lasers

LASER PHYSICS LETTERS, Issue 10 2006
F. Principato
Abstract Experimental investigations of the low frequency noise of multimode 780 nm vertical cavity surface emitting lasers are reported. Electrical noise, optical noise and their correlation have been measured in the frequency range 1 Hz,95 kHz. The results show that the main contribution to the electrical noise is located in the distributed Bragg reflector layers of the laser. The optical power and pump current noise sources are strongly correlated below and around the threshold, while are weakly correlated above threshold. It is argued that the noise in the optical power is due to both free injection carrier noise and optical gain fluctuations. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Feasibility of electromyography (sEMG) in measuring muscular activity during spinal anaesthesia in patients undergoing knee arthroplasty

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2005
L. Niemi-Murola
Background:, Bromage scale (0,3) is used to measure the degree of motor block during spinal anaesthesia. However, an estimation of motor block is difficult during surgery. The purpose of this study was to evaluate the feasibility of surface EMG describing spontaneous muscular activity in the lower extremities during spinal anaesthesia. Methods:, In part I of the study, 13 patients undergoing day case surgery were studied. They received 10 mg hyperbaric bupivacaine at interspace L3,4. EMG, sensory and muscular block were measured at 5-min intervals during the first 30 min and then every 15 min until the patient was able to flex the knee. In part II of the study, 16 patients undergoing knee arthroplasty received 10 mg bupivacaine through spinal catheter at interspace L3,4 (Group CSA). An additional bolus of 2.5 mg was administered using EMG-guidance, if needed. Another group, 15 patients, received a single bolus of bupivacaine (15,20 mg) at L3,4 (Group Bolus). EMG, muscular and sensory block were monitored as described above. The epidural catheter was used as rescue. Results:, Part I: EMG compared to modified Bromage scale showed a significant correlation (P < 0.01, Spearman rank correlation). Part II: The amount of bupivacaine was significantly reduced with EMG guidance when compared with the single bolus group (14.0 mg vs. 17.0 mg) (P < 0.05 Mann,Whitney U). Motor block started to recover before the sensory block in 7/15 CSA patients vs. 1/15 Bolus patient. Conclusion:, Stable maximal sensory block does not necessarily correlate with adequate motor block in patients receiving spinal anaesthesia induced with small bolus doses. In spite of electrical noise, EMG-guided administration of spinal anaesthesia significantly reduced the amount of bupivacaine compared to the hospital routine. Further studies are needed to develop the method. [source]

Influence of Mobile Magnetic Resonance Imaging on Implanted Pacemakers

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003
RYOJI KISHI
KISHI, R., et al.: Influence of Mobile Magnetic Resonance Imaging on Implanted Pacemakers.Purpose: Mobile magnetic resonance imaging (MRI) systems will be widely used in Japan. When traveling, mobile MRI generate alternating electromagnetic waves which may cause electromagnetic interference (EMI). This study was designed to determine whether this may influence the function of implanted pacemakers (PM). Methods and Results: The influence of the static magnetic fields was tested in the first method using a PM-human model (Phantom). Magnetic force was simultaneously measured. The PM was switched to the magnet mode within 90 cm from the vehicle, where the magnetic force was = 2 mT. In the second method, six phantoms were placed on the side of the road, facing in three different directions in X-Y-Z axis orientations, at 1.3 m and 2.0 m above the ground. The mobile MRI passed by at a distance of 1 m from the phantoms at the speed of 20 or 40 km/h. In these experiments, magnet mode switch of the PM was observed for 2 seconds when the vehicle passed close to the phantoms, though no electrical noise was recorded. Conclusion: Mobile MRI vehicles can switch a PM to magnet mode when the distance between patient and vehicle is <90 cm, regardless of whether the vehicle is moving or at a stop. Patients with implanted PM should not approach within <1 m of a mobile MRI. No other EMI-induced PM dysfunction was detected. (PACE 2003; 26[Pt. II]:527,529) [source]