Physiological measurement
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Physiological measurement · Apr 2009
Randomized Controlled TrialPoincaré analysis of an overnight arterial oxygen saturation signal applied to the diagnosis of sleep apnea hypopnea syndrome.
The analysis of oxygen desaturations is a basic variable in polysomnographic studies for the diagnosis of sleep apnea. Several algorithms operating in the time domain already exist for sleep apnea detection via pulse oximetry, but in a disadvantageous way--they achieve either a high sensitivity or a high specificity. The aim of this study was to assess whether an alternative analysis of arterial oxygen saturation (SaO2) signals from overnight pulse oximetry could yield essential information on the diagnosis of sleep apnea hypopnea syndrome (SAHS). ⋯ Results showed that the presence of apnea events in SAHS patients caused an increase in the SD1 Poincaré parameter. This conclusion was assessed prospectively using the test dataset. 90.9% sensitivity and 84.0% specificity were obtained in the test group. We conclude that Poincaré analysis could be useful in the study of SAHS, contributing to reduce the demand for polysomnographic studies in SAHS screening.
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Physiological measurement · Mar 2009
Identification of the cuff transfer function increases indirect blood pressure measurement accuracy.
At present, oscillometric blood pressure meters are among the most commonly used medical devices in the world. While substantial effort has been invested in developing more reliable evaluation algorithms, the actual hardware setup-an inflatable cuff and a pressure transducer connected to it-remained basically unchanged since the mid 19th century. Our research work has concentrated on developing an experimental test set-up to determine the transfer function of cuffs. ⋯ The placement of the bladder (tight, loose, upside down, over a shirtsleeve) remarkably affects the estimated systolic and diastolic pressures. Based on the reported research work it is possible to identify an improperly applied cuff that would result in a misleading BP measurement. Distortion caused by miscuffing is rather patient specific.
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Physiological measurement · Feb 2009
Fetal heart rate variability reveals differential dynamics in the intrauterine development of the sympathetic and parasympathetic branches of the autonomic nervous system.
The aim of this study was to investigate the hypothesis that fetal beat-to-beat heart rate variability (fHRV) displays the different time scales of sympatho-vagal development prior to and after 32 weeks of gestation (wks GA). Ninety-two magnetocardiograms of singletons with normal courses of pregnancy between 24 + 1 and 41 + 6 wks GA were studied. Heart rate patterns were either quiet/non-accelerative (fHRP I) or active/accelerative (fHRP II) and recording quality sufficient for fHRV. ⋯ Non-accelerative fHRP are indicative of parasympathetic dominance >32 wks GA. In contrast, the sympathetic accentuation during accelerative fHRP is displayed in the interrelations between mHR, SDNN and SDNN/RMSSD. Prior to 32 wks GA, fHRV reveals the increasing activity of the respective branches of the autonomic nervous system differentiating the types of fHRP.
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Physiological measurement · Dec 2008
Adaptive singular value cancelation of ventricular activity in single-lead atrial fibrillation electrocardiograms.
The proper analysis and characterization of atrial fibrillation (AF) from surface electrocardiographic (ECG) recordings requires to cancel out the ventricular activity (VA), which is composed of the QRS complex and the T wave. Historically, for single-lead ECGs, the averaged beat subtraction (ABS) has been the most widely used technique. However, this method is very sensitive to QRST wave variations and, moreover, high-quality cancelation templates may be difficult to obtain when only short length and single-lead recordings are available. ⋯ Thus, ASVC provides a more accurate beat-to-beat ventricular QRST representation than traditional techniques. As a consequence, VA cancelation is optimized and the AA can be extracted more precisely. Finally, the study has proven that optimal VA cancelation is achieved when a number between 20 and 30 complexes is selected following a correlation-based strategy.
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Physiological measurement · Sep 2008
Comment LetterComment on 'Abnormal autonomic cardiac response to transient hypoxia in sickle cell anemia'.
Our recent results support the suggestions made by Sangkatumvong et al regarding autonomic dysfunction in sickle cell anemia.