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ABSTRACT: We have recently proposed a novel CO index, namely pulse time reflection ratio (PTRR), which is extracted from photoplethysmogram and electrocardiogram and measurable from wearable devices, and proved that this index is potentially useful for dynamic CO monitoring in a preliminary study carried out on young, healthy subjects. In this study, we presented an evaluation of this technique against impedance cardiography on 64 subjects undergoing incremental maximal exercise testing, including 15 healthy elderly, 19 cardiovascular patients and 30 heart failure patients. Results showed significant intra-subject correlations (r) between PTRR and reference CO in all subjects (mean r: 0.93, p<0.05) and no significant differences on mean r among subject populations (one-way ANOVA, p=0.48). With further development and testing on mobile subjects, this technique can be applied for long-term CO monitoring at home or in other dynamic situations.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:1515-8.
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IEEE Transactions on Information Technology in Biomedicine 04/2011; · 1.68 Impact Factor
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ABSTRACT: P-Health, a future health model that can be described as a 6-P's paradigm, aims to provide low cost and high quality health care via redesigning care practice and networking information systems at different levels. To realise p-Health, a multi-level health information system has to be developed for the processing, storage, transmission, acquisition and retrieval (P-STAR) of health information that spans multiple temporal and spatial scales and consists of multi-modality. This paper uses wearable devices, which have to be miniaturised, integrated, networked, digitalised, smart and standardised (MINDSS), as examples to illustrate how two or more P-STAR technologies are integrated together to implement a specific health care application under p-Health. In particular, standardisation of MINDSS devices that required a new measurement principle, such as the calibration procedure of cuff-less blood pressure measurement devices, is discussed.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: Body sensor networks (BSNs) have emerged as a new technology for healthcare applications, but the security of communication in BSNs remains a formidable challenge yet to be resolved. The paper discusses the typical attacks faced by BSNs and proposes a fast biometric based approach to generate keys for ensuing confidentiality and authentication in BSN communications. The approach was tested on 900 segments of electrocardiogram. Each segment was 4 seconds long and used to generate a 128-bit key. The results of the study found that entropy of 96% of the keys were above 0.95 and 99% of the hamming distances calculated from any two keys were above 50 bits. Based on the randomness and distinctiveness of these keys, it is concluded that the fast biometric based approach has great potential to be used to secure communication in BSNs for health applications.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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IEEE transactions on information technology in biomedicine: a publication of the IEEE Engineering in Medicine and Biology Society 07/2010; 14(4):895-6. · 1.69 Impact Factor
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ABSTRACT: This paper reports a novel contactless monitoring method to record photoplethysmogram (PPG) on a mattress for the continuous measurement of heart rate (HR). PPGs were obtained from subjects' fingers and backs with and without making a direct contact between the PPG sensor and their skin when they rested in a supine position on the mattress. Electrocardiograms (ECGs) were measured from the subjects' limbs for reference. Clear PPG waveforms were obtained from the subjects' backs. Beat-to-beat HR derived from contactless PPG measurement was comparable to those measured from contact PPG and ECG measurements. Thus we found that contactless PPG could be captured from the subjects' backs and it was sufficient to provide accurate HR measurements. This contactless monitoring of PPG has the potential to reduce obstruction in sleep and provide clinical evaluation in sleep study.
Physiological Measurement 07/2010; 31(7):1065-74. · 1.68 Impact Factor
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ABSTRACT: Cardiac output (CO) monitoring is not only essential for critically ill patients in the hospital, but also for patients at home and those undergoing cardiopulmonary exercise testing. However, CO is difficult to monitor during daily activities and exercise. In this paper, we aim at developing a novel CO estimation method that can be used under these challenging conditions. The tube model was utilized to derive a CO index, namely the pulse time reflection ratio (PTRR) from an electrocardiogram and photoplethysmogram. After calibration, the PTRR can be used to estimate beat-to-beat CO. The proposed method was verified against CO measured by impedance cardiography on 19 healthy subjects in an incremental intensity exercise test. Results showed that there were strong correlations (r) between the PTRR and reference CO in 18 subjects (mean r: 0.88, n = 245 trials). Two calibration approaches reported in the literature were applied to the proposed method and the corresponding bias +/- precisions of estimation errors were 0 +/- 1.89 L min(-1) and -0.22 +/- 2.12 L min(-1), respectively. The percent errors were 21.94% and 24.90%, smaller than the clinical acceptance limit (30%). To conclude, after calibration, this method can be used to monitor CO on healthy subjects during incremental intensity exercise.
Physiological Measurement 05/2010; 31(5):715-26. · 1.68 Impact Factor
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ABSTRACT: P-Health, a future health model that can be described as a 6-P's paradigm, aims to provide low cost and high quality health care via redesigning care practice and networking information systems at different levels. To realise p-Health, a multi-level health information system has to be developed for the processing, storage, transmission, acquisition and retrieval (P-STAR) of health information that spans multiple temporal and spatial scales and consists of multi-modality. This paper uses wearable devices, which have to be miniaturised, integrated, networked, digitalised, smart and standardised (MINDSS), as examples to illustrate how two or more P-STAR technologies are integrated together to implement a specific health care application under p-Health. In particular, standardisation of MINDSS devices that required a new measurement principle, such as the calibration procedure of cuff-less blood pressure measurement devices, is discussed.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:1755-8.
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[show abstract]
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ABSTRACT: Body sensor networks (BSNs) have emerged as a new technology for healthcare applications, but the security of communication in BSNs remains a formidable challenge yet to be resolved. The paper discusses the typical attacks faced by BSNs and proposes a fast biometric based approach to generate keys for ensuing confidentiality and authentication in BSN communications. The approach was tested on 900 segments of electrocardiogram. Each segment was 4 seconds long and used to generate a 128-bit key. The results of the study found that entropy of 96% of the keys were above 0.95 and 99% of the hamming distances calculated from any two keys were above 50 bits. Based on the randomness and distinctiveness of these keys, it is concluded that the fast biometric based approach has great potential to be used to secure communication in BSNs for health applications.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:2034-6.
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ABSTRACT: Security and privacy are among the most crucial issues for data transmission in tele-healthcare applications. The paper proposes a biometrics based solution, combining encryption and authentication for wireless communication within a body sensor network (BSN), as well as between a BSN and a remote server (RS) of a tele-healthcare system. The method aims to use static and dynamic biometric traits to generate authentication and encryption keys respectively. Keys of 64 and 128 bits were generated from electrocardiogram and photoplethysmogram of 9 subjects and fingerprint images of 20 subjects. The entropy of the keys ranged from 0.662 to 1 and the hamming distances between them were all non-zero. The results of this study found that random and distinctive keys can be generated by a biometric approach for encrypting and authenticating data in tele-healthcare systems.
Applied Sciences in Biomedical and Communication Technologies, 2009. ISABEL 2009. 2nd International Symposium on; 12/2009
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ABSTRACT: Cardiac output (CO) monitoring is essential for indicating the perfusion status of the human cardiovascular system under different physiological conditions. However, it is currently limited to hospital use due to the need for either skilled operators or big, expensive measurement devices. Therefore, in this paper we devise a new CO indicator which can easily be incorporated into existing wearable devices. To this end, we propose an index, the inflection and harmonic area ratio (IHAR), from standard photoplethysmographic (PPG) signals, which can be used to continuously monitor CO. We evaluate the success of our index by testing on sixteen normotensive subjects before and after bicycle exercise. The results showed a strong intra-subject correlation between IHAR and CO<sub>imp</sub> measured by the bio-impedance method in fifteen subjects (mean r = 3D 0.82, p<0.01). After least squares linear regression, the precision between CO<sub>imp</sub> and CO estimated from IHAR (CO<sub>IHAR</sub>) was 1.40 L/min. The total percentage error of the results was 16.2%, which was well below the clinical acceptance limit of 30%. The results suggest that IHAR is a promising indicator for wearable and noninvasive CO monitoring.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: In this study, we have used impedance cardiography to determine blood pressure (BP) cufflessly and non-invasively. We have devised a new parameter, QdZ [the duration measured from the foot of electrocardiogram (ECG) Q wave to the peak of impedance cardiogram (ICG)], for this purpose. Twenty-two subjects performed four minutes of treadmill exercise such that systolic BP (SBP) was increased significantly. We found that SBP was closely correlated with QdZ (R<sup>2</sup> = 0.65) demonstrating the potential application of ICG to cuffless and non-invasive BP measurement.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: This paper reports a novel contactless monitoring method to record reflective mode photoplethysmogram (PPG) on a sleeping bed for heart rate (HR) estimation. The electrocardiogram (ECG) and pulse transit time (PTT) were also measured in this study. ECG was measured from subjects' limbs whilst PPG was obtained from their right index fingers and their backs with and without direct contact between the PPG sensor and the subjects' skin respectively. Clear PPG waveforms were obtained from the subjects' backs even though the sensor was not directly attached to their skin. Beat-to-beat HRs derived from the back PPGs were closely correlated with those measured from the finger PPGs and ECGs. Thus we found that contactless PPG could be captured from the subjects' backs to determine HR accurately.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: This paper proposes one of the unique requirements in the validation protocol of the IEEE P1708 standard in assessing wearable cuff-less blood pressure (BP) measuring devices. Based on principles that are different from that of the conventional cuff-based devices, the cuff-less BP measurement approaches often require an individual calibration procedure. In this study, we used data from an experiment carried out on 28 subjects with a total of 139 sets of BP measurements as an example to show that breakdown of the performance evaluation of cuff-less devices according to the change of BP from the point of calibration is crucial for understanding and interpreting the overall accuracy of the device.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: Security and privacy are among the most crucial issues for data transmission in telemedicine systems. This paper proposes a solution for securing wireless data transmission in telemedicine systems, i.e. within a body sensor network (BSN), between the BSN and server as well as between the server and professionals who have assess to the server. A unique feature of this solution is the generation of random keys by physiological data (i.e. a biometric approach) for securing communication at all 3 levels. In the performance analysis, inter-pulse interval of photoplethysmogram is used as an example to generate these biometric keys to protect wireless data transmission. The results of statistical analysis and computational complexity suggest that this type of key is random enough to make telemedicine systems resistant to attacks.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: Nighttime blood pressure (BP) is found to best predict the 5-year risk of cardiovascular death in comparison to daytime BP, BP measured over a 24-hour period and clinical BP. In view of this, a novel contactless system has been developed on a sleeping bed for the cuffless and continuous estimation of BP at night. Experiments were conducted on 11 subjects to evaluate the contactless system, particularly its performance compared to a contact system. The results of this study showed that the accuracy of the contactless system to estimate BP by a cuffless approach is comparable to that of the contact system when measured at the same posture. More studies have to be conducted in order to understand the difference of the cuffless BP estimation approach when measuring at supine and sitting postures.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: Terahertz pulsed imaging (TPI) is a non-ionizing and non-destructive imaging technique that has been recently used to study a wide range of biological materials. The severe attenuation of terahertz radiation in samples with high water content means that biological samples need to be very thin if they are to be measured in transmission geometry. To overcome this limitation, samples could be measured in reflection geometry and this is the most feasible way in which TPI could be performed in a clinical setting. In this study, we therefore used TPI in reflection geometry to characterize the terahertz properties of several organ samples freshly harvested from laboratory rats. We observed differences in the measured time domain responses and determined the frequency-dependent optical properties to characterize the samples further. We found statistically significant differences between the tissue types. These results show that TPI has the potential to accurately differentiate between tissue types non-invasively.
Physics in Medicine and Biology 02/2009; 54(1):149-60. · 2.83 Impact Factor
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ABSTRACT: In this study, we have used impedance cardiography to determine blood pressure (BP) cufflessly and non-invasively. We have devised a new parameter, QdZ [the duration measured from the foot of electrocardiogram (ECG) Q wave to the peak of impedance cardiogram (ICG)], for this purpose. Twenty-two subjects performed four minutes of treadmill exercise such that systolic BP (SBP) was increased significantly. We found that SBP was closely correlated with QdZ (R(2)=0.65) demonstrating the potential application of ICG to cuffless and non-invasive BP measurement.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:800-2.
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[show abstract]
[hide abstract]
ABSTRACT: Security and privacy are among the most crucial issues for data transmission in telemedicine systems. This paper proposes a solution for securing wireless data transmission in telemedicine systems, i.e. within a body sensor network (BSN), between the BSN and server as well as between the server and professionals who have assess to the server. A unique feature of this solution is the generation of random keys by physiological data (i.e. a biometric approach) for securing communication at all 3 levels. In the performance analysis, inter-pulse interval of photoplethysmogram is used as an example to generate these biometric keys to protect wireless data transmission. The results of statistical analysis and computational complexity suggest that this type of key is random enough to make telemedicine systems resistant to attacks.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:701-4.
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[show abstract]
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ABSTRACT: Cardiac output (CO) monitoring is essential for indicating the perfusion status of the human cardiovascular system under different physiological conditions. However, it is currently limited to hospital use due to the need for either skilled operators or big, expensive measurement devices. Therefore, in this paper we devise a new CO indicator which can easily be incorporated into existing wearable devices. To this end, we propose an index, the inflection and harmonic area ratio (IHAR), from standard photoplethysmographic (PPG) signals, which can be used to continuously monitor CO. We evaluate the success of our index by testing on sixteen normotensive subjects before and after bicycle exercise. The results showed a strong intra-subject correlation between IHAR and CO(imp) measured by the bio-impedance method in fifteen subjects (mean r = 0.82, p<0.01). After least squares linear regression, the precision between CO(imp) and CO estimated from IHAR (CO(IHAR)) was 1.40 L/min. The total percentage error of the results was 16.2%, which was well below the clinical acceptance limit of 30%. The results suggest that IHAR is a promising indicator for wearable and noninvasive CO monitoring.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:1746-9.
