Journal of clinical monitoring and computing
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J Clin Monit Comput · Jun 2013
Clinical TrialThe analysis of transesophageal oxygen saturation photoplethysmography from different signal sources.
The photoplethysmography (PPG) signals detected by transesophageal oximetry sensor toward aorta arch (AA), descending aorta (DA), and left ventricle (LV) under the guidance of transesophageal echocardiography (TEE) were investigated, and the effects of filter application on PPG signals were evaluated. Eleven cardiac surgical patients were involved. After anesthesia was induced, the TEE probe with a modified pulse oximetry sensor was inserted. ⋯ The AC amplitude in LV PPG was significant larger than in AA and DA PPG, and both AC/DC and ventilation-induced AC variation in LV PPG were significantly higher than in AA PPG or DA PPG either. There were no significant differences of AC amplitude between filtered and ventilation off PPG signals. The AC amplitudes and AC/DC toward LV are significantly higher than transesophageal oximeter toward AA or DA, and the effect of mechanical ventilation on transesophageal PPG can be obviously reduced by filtering techniques.
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Heart rate variability (HRV) is a non-invasive method to measure cardiac autonomic function. Impairments in HRV have been proposed as independent risk factor for increased cardiac mortality and morbidity. Cardio protective phenomenon in females has been hypothesized to be due to differential autonomic tone. ⋯ Sympathetic tone predominates and vagal tone diminishes with aging process. Females showed greater vagal tone than male. This differential autonomic tone indicate age, gender related predisposition to cardiovascular disease.
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J Clin Monit Comput · Jun 2013
Heart rate variability analysis during central hypovolemia using wavelet transformation.
Detection of hypovolemia prior to overt hemodynamic decompensation remains an elusive goal in the treatment of critically injured patients in both civilian and combat settings. Monitoring of heart rate variability has been advocated as a potential means to monitor the rapid changes in the physiological state of hemorrhaging patients, with the most popular methods involving calculation of the R-R interval signal's power spectral density (PSD) or use of fractal dimensions (FD). However, the latter method poses technical challenges, while the former is best suited to stationary signals rather than the non-stationary R-R interval. ⋯ Results demonstrate that the proposed DWT-based model outperforms individual PSD and FD methods as well as the combination of these two traditional methods at both sample rates of 500 Hz (p value <0.0001) and 125 Hz (p value <0.0001) in detecting the degree of hypovolemia. These findings indicate the potential of the proposed DWT approach in monitoring the physiological changes caused by hemorrhage. The speed and relatively low computational costs in deriving these features may make it particularly suited for implementation in portable devices for remote monitoring.
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J Clin Monit Comput · Jun 2013
Reference values for volumetric capnography-derived non-invasive parameters in healthy individuals.
The aim of this study was to determine typical values for non-invasive volumetric capnography (VCap) parameters for healthy volunteers and anesthetized individuals. VCap was obtained by a capnograph connected to the airway opening. We prospectively studied 33 healthy volunteers 32 ± 6 years of age weighing 70 ± 13 kg at a height of 171 ± 11 cm in the supine position. ⋯ Volunteers showed better clearance of CO₂ compared to anesthetized patients as indicated by (median and interquartile range): (1) an increased elimination of CO₂ per mL of VT of 0.028 (0.005) in volunteers versus 0.023 (0.003) in anesthetized patients, p < 0.05; (2) a lower normalized slope of phase III of 0.26 (0.17) in volunteers versus 0.39 (0.38) in anesthetized patients, p < 0.05; and (3) a lower Bohr dead space ratio of 0.23 (0.05) in volunteers versus 0.28 (0.05) in anesthetized patients, p < 0.05. This study presents reference values for non-invasive volumetric capnography-derived parameters in healthy individuals. Mechanical ventilation and anesthesia altered these values significantly.
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J Clin Monit Comput · Jun 2013
Usefulness of perfusion index to detect the effect of brachial plexus block.
The traditional method to evaluate adequacy of the block for surgery is based on loss of sensory response to stimuli, which requires patient cooperation. Several methods have been described for objective assessment of the nerve block. The aim of the study was to investigate whether perfusion index (PI), a measure of peripheral perfusion from a pulse oximetry finger sensor, is a reliable and objective method for assessing the adequacy of infraclavicular blockade and to describe the time course of PI changes once peripheral nerve block has been achieved during surgery. ⋯ The perfusion index is a predictor of infraclavicular block success. The largest changes in PI occur 30 min after the block administration but significant changes in PI were detected 10 min after administration. Perfusion index monitoring may provide a highly valuable tool to quickly evaluate the success of regional anesthesia of the upper extremity in clinical practice.