Physiological measurement
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Physiological measurement · Sep 2008
Comparative StudyArterial flow measurements during reactive hyperemia using NIRS.
Non-invasive evaluation of peripheral perfusion may be useful in many contexts including clinical research. We validated a novel non-invasive spectroscopy technique to quantify forearm arterial inflow. This method, which is based on the measurement of tissular total hemoglobin variations after an ischemic period, was compared to strain gauge plethysmography (SGP). ⋯ Twenty-seven serial measurements were then made to evaluate flow variation during forearm reactive hyperemia. SGP and NIRS methods showed excellent reproducibility with the same intra-class correlation coefficients (0.98). In conclusion, the NIRS technique appears well suited for non-invasive evaluation of quantitative arterial forearm flow.
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Physiological measurement · Aug 2008
Non-invasive measurement of intra-abdominal pressure: a preliminary study.
The importance of measuring intra-abdominal pressure (IAP) has increased since the negative effects of sustained increased IAP, also known as intra-abdominal hypertension (IAH), have become known. The relation between IAP and abdominal wall tension has been included in several reports. We have developed a device to measure abdominal wall tension by measuring force and distance. ⋯ The points along the mid transverse plane appear to be more similar compared to more cranial and caudal points. We have assessed the feasibility of a device that non-invasively can track changes in IAP. Measurements performed with the device are preliminary results, and further investigation is needed.
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Physiological measurement · Jun 2008
Improvements in the image quality of ventilatory tomograms by electrical impedance tomography.
We present an improved approach to image ventilation in functional electrical impedance tomography (f-EIT). It combines the advantages of the two established procedures of calculating standard deviation as a functional parameter of ventilation (SD method) and the so-called filling capacity (FC method). The SD method quantifies the local impedance variation over a series of tomograms for each pixel; the FC method is based on the slope of a linear fit of regional versus the global impedance change. ⋯ The robustness with regard to noise of the VT method was similar to that of the FC method. The practical value of suppression of non-ventilatory impedance changes, artefacts and noise was tested by studying ten healthy subjects (four females, six males) during normal breathing. We found a highly significant improvement in the image quality (p < 0.001) of ventilation for this group of volunteers.
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Physiological measurement · Jun 2008
A bio-electromechanical imaging technique with combined electrical impedance and ultrasound tomography.
Electrical impedance tomography (EIT) seeks to image the electrical conductivity of an object using electrical impedance measurement data at its periphery. Ultrasound reflection tomography (URT) is an imaging modality that is able to generate images of mechanical properties of the object in terms of acoustic impedance changes. Both URT and EIT have the potential to be used in various medical applications. ⋯ A dual bio-electromechanical tomography system using ultrasound and electrical tomography is proposed in this paper to improve the detection of the small-size tumour. Data fusion techniques are implemented to combine the EIT/URT data. Based on simulations, we demonstrate the improvement of detection of small size anomalies and improved depth detection compared to single modality soft field tomography.
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Physiological measurement · May 2008
Robust electrocardiogram (ECG) beat classification using discrete wavelet transform.
This paper presents a robust technique for the classification of six types of heartbeats through an electrocardiogram (ECG). Features extracted from the QRS complex of the ECG using a wavelet transform along with the instantaneous RR-interval are used for beat classification. The wavelet transform utilized for feature extraction in this paper can also be employed for QRS delineation, leading to reduction in overall system complexity as no separate feature extraction stage would be required in the practical implementation of the system. ⋯ Another main advantage of this method is its robustness to noise, which is illustrated in this paper through experimental results. Furthermore, principal component analysis (PCA) has been used for feature reduction, which reduces the number of features from 11 to 6 while retaining the high beat classification accuracy. Due to reduction in computational complexity (using six features, the time required is approximately 4 ms per beat), a simple classifier and noise robustness (at 10 dB signal-to-noise ratio, accuracy is 95%), this method offers substantial advantages over previous techniques for implementation in a practical ECG analyzer.