Biomedical subjects

Chu Sing Lim

Publications and source records attributed to Chu Sing Lim.

7 recordsLinked to original sources

PubMed2006

Phonocardiographic signal analysis method using a modified hidden Markov model.

Auscultation is an important diagnostic indicator for cardiovascular analysis. Heart sound classification and analysis play an important role in the auscultative diagnosis. This study uses a combination of Mel-frequency cepstral coefficient (MFCC) and hidden Markov model (HMM) to efficiently extract the features for pre-processed heart sound cycles for the purpose of classification. A system was developed for the interpretation of heart sounds acquired by phonocardiography using pattern recognition. The task of feature extraction was performed using three methods: time-domain feature, short-time Fourier transforms (STFT) and MFCC. The performances of these feature extraction methods were then compared. The results demonstrated that the proposed method using MFCC yielded improved interpretative information. Following the feature extraction, an automatic classification process was performed using HMM. Satisfactory classification results (sensitivity > or =0.952; specificity > or =0.953) were achieved for normal subjects and those with various murmur characteristics. These results were based on 1398 datasets obtained from 41 recruited subjects and downloaded from a public domain. Constituents characteristics of heart sounds were also evaluated using the proposed system. The findings herein suggest that the described system may have the potential to be used to assist doctors for a more objective diagnosis.

Data Interpretation, Statistical↗

PubMed2006

Authentication of traditional Chinese medicine using infrared spectroscopy: distinguishing between ginseng and its morphological fakes.

The quality of pharmaceutical products such as ginseng is important for ensuring consumer safety and efficacy. Ginseng is an expensive herb, and adulteration with other cheaper products may occur. Quality assurance of ginseng is needed since many of its commercial products now come in various formulations such as capsules, powder, softgels and tea. Thus traditional means of authentication via smell, taste or physical appearance are hardly reliable. Herbs like ginseng tend to exhibit characteristic infrared fingerprints due to their different chemical constituents. Here we report for the first time a rapid means of distinguishing American and Asian ginsengs from two morphological fakes--sawdust and Platycodon grandiflorum, via pattern differences and principal component analysis of their infrared spectra. Our results show that ginseng can be distinguished from both sawdust and Platycodon grandiflorum, hence there is a potential of using infrared spectroscopy as a novel analytical technique in the authentication of ginseng.

Drugs, Chinese Herbal↗

PubMed2006

Dual-channel photoplethysmography to monitor local changes in vascular stiffness.

OBJECTIVES: Monitoring arterial distensibility changes is important to understand the cardiovascular status of patient. Pulse transit time (PTT), which is an inverse equivalent of pulse wave velocity (PWV), has shown its potential in such studies. However, its methodological approach in using an electrocardiogram and a peripheral photoplethysmography (PPG) is limited due to the inclusion of pre-ejection period (PEP) in its computation. Previous studies have suggested the using the transit time difference between two peripheral measuring sites (PTT-D) instead. However, it requires two medical instruments and may not be efficient in terms of equipment utility, especially in prolonged clinical studies. METHODS: Postural changes are known to cause complex haemodynamics adaptation and thereby affecting transit time measurements. A customised dual-channel PPG system based on discrete electronic devices was constructed to evaluate against conventional peripheral-based PTT. 10 healthy adults (7 male; mean age 27.0 yr) were recruited to assess the differences observed in PTT and PTT-D during two postural change test activities. RESULTS: PTT-D derived from the customised PPG system registered 43.3+/- 5.6 ms and - 31.1+/- 3.8 ms relative changes for the two regulated activities while conventional PTT recorded 43.6+/- 10.3 ms and -31.0+/-m 6.5 ms respectively. The former may have similar results but have significantly lower variance (< 0.05). CONCLUSIONS: Findings herein suggest that PTT-D derived from the customised PPG system shows potential. It can be used as an alternative to conventional peripheral-based PTT and possibly as a direct assessment of arterial distensibility or PWV variations as it does not include PEP in its time-related computations.

Adult↗

PubMed2006

Evaluation of blood pressure changes using vascular transit time.

Imbalance of the human haemodynamic system can provide a prognosis of syncope, dizziness or hypertension. This can be assessed by monitoring its responses to postural change. Examining variations in blood pressure (BP) is deemed an effective means to identify symptoms of this associated condition. However, conventional methods do not promote prolonged monitoring due to the discomfort caused to patients. Established correlations between BP and pulse wave transmission have shown its usefulness in clinical applications. In this study, photoplethysmography and phonocardiography were used to estimate BP changes via observed variations in delay transmission or vascular transit time (VTT) at the upper limb. Thirty-one healthy adults (21 male) were recruited to perform three test activities, namely the arm held at heart level, fully raised up and held down. Association of the three BP indices and heart rate variations with transit time changes was then computed. The results showed that observed VTT changes were related to systolic BP (R(2) = 0.820; p < 0.05), diastolic BP (R(2) = 0.517; p < 0.05), mean arterial pressure (R(2) = 0.673; p < 0.05) and heart rate (R(2) = 0.000; p > 0.05). As systolic BP had the strongest correlation, a regression equation was formulated to associate the two parameters. The non-invasive measuring nature of VTT can be more accommodating to patients, especially during continual monitoring. Moreover, it has the added advantage that the pre-ejection period is not included in its time-related derivations.

Adult↗

PubMed2006

Pulse transit time based on piezoelectric technique at the radial artery.

OBJECTIVES: Pulse transit time (PTT) has shown its potential in relevant cardiovascular and cardiorespiratory studies. However, the use of photoplethysmography (PPG) in PTT measurement can be limited in events of poor peripheral perfusion. Uninterrupted PTT monitoring may also not be achievable when less cooperative patients distribute the PPG probe due to its prominent light source. Hence, there is a need for an alternative method to measure PTT in such incidents. METHODS: In this study, the piezoelectric (PIEZO) technique to detect pulsations from a human wrist above the radial artery to estimate PTT is presented. 17 healthy adults (11 male; age range of 21-33 years) were recruited to compare PTT and heart rate (HR) differences between the PPG and PIEZO methods. These time-related derivations were made with respect to an electrocardiogram (ECG). RESULTS: The timing consistency of the PIEZO transducer shows significant correlations (p < 0.01) to those derived from the ECG and a pulse oximeter. Particularly, there is a high level of agreement of < 1 beat per minute (bpm) difference in HR estimates observed when compared to the two commercial devices in the respective Bland-Altman plots. Comparison of PTT obtained from the PIEZO transducer against the PPG signal shows constantly lower values due to the shorter path length it requires to propagate. A regression equation was formulated to relate the PTT values acquired from both these signals. CONCLUSIONS: Preliminary findings herein suggest that the PIEZO technique can be useful as an alternative for PTT monitoring. This shows promise to be more accommodating for less cooperative patients or those with insufficient peripheral perfusion.

Adult↗

PubMed2006

Pulse transit time as an indirect marker for variations in cardiovascular related reactivity.

Study of cardiac functions has shown to be important in understanding the prognosis and pathogenesis of vascular diseases. A physiologic parameter termed pulse transit time (PTT) has been studied intensively to be used as an indirect marker of such pathologic conditions. It is defined as the time it takes a pressure pulsation to travel between two arterial sites. For convenience of measurement, the interval between the peak of the R-wave on the electrocardiogram and the onset of the corresponding pulse in the finger pad measured by photoplethysmography is usually used. In this review, its definition, current applications in cardiovascular related studies and issues are presented in turn. Investigational studies suggest that PTT did not meet the level of accuracy required for medical practice as a marker for beat-to-beat blood pressure (BP). However, documented evidences indicate that PTT has high correlations when it is utilised as a surrogate semi-quantitative monitor of abrupt BP changes. Present literature suggests that description of disease-specific cardiovascular reactivity pattern is possible with techniques based on PTT. The attraction of PTT due to its non-invasive nature and revealing properties can only increase. Hence, the use of this simple technique in a clinical setting is still to realise its full potential.

Arteries↗

PubMed2005

Overview on the analytical tools for quality control of natural product-based supplements: a case study of ginseng.

The quality of pharmaceutical products like ginseng is important for ensuring consumer safety and efficacy. Many ginseng products sold today are in various formulations such as powder, capsules, tablets, soft-gels, liquid extracts, and tea. This renders ginseng less identifiable by smell, taste, or physical appearance. Furthermore, as ginseng is expensive, adulteration with other cheaper products occurs. Hence quality assurance of ginseng is needed. This paper reviews the major techniques for ascertaining the level of ginsenosides, the primary active ingredients for ginseng, and covers high-performance liquid, gas, and thin-layer chromatographies, infrared and nuclear magnetic resonance spectroscopies, enzyme immunoassays, and other molecular methods. Supporting techniques such as ultraviolet, fluorescence, diode array and evaporative light scattering detections, and mass spectrometry will also be touched upon. This review also discusses the principles and applications of biosensors-in particular fiber optic-based sensors-and their feasibility in ginseng analysis based on preliminary studies. Despite their potential, there is currently no or limited commercial exploitation of fiber optic-based sensors to perform ginseng quality analysis. The opportunity for biosensors to be used for the rapid quality surveillance of ginseng is appealing, but several key issues still need to be addressed before they find widespread applications in the traditional Chinese medicine industry.

Biosensing Techniques↗