Photoplethysmography and its application in clinical physiological measurement

http://www.kresttechnology.com/krest-academic-projects/krest-major-projects/ECE/B-Tech%20Papers/67.pdf

ECG signal denoising and baseline wander correction based on the empirical mode decomposition

Oscillating-water-column wave energy converters and air turbines: A review

McDonaldʼs Blood Flow in Arteries

Photoplethysmography (PPG) is a noninvasive optical technique for detecting microvascular blood volume changes in tissues. Its ease of use, low cost and convenience make it an attractive area of research in the biomedical and clinical communities. Nevertheless, its single spot monitoring and the need to apply a PPG sensor directly to the skin limit its practicality in situations such as perfusion mapping and healing assessments or when free movement is required. The introduction of fast digital cameras into clinical imaging monitoring and diagnosis systems, the desire to reduce the physical restrictions, and the possible new insights that might come from perfusion imaging and mapping inspired the evolution of the conventional PPG technology to imaging PPG (IPPG). IPPG is a noncontact method that can detect heart-generated pulse waves by means of peripheral blood perfusion measurements. Since its inception, IPPG has attracted significant public interest and provided opportunities to improve personal healthcare. This study presents an overview of the wide range of IPPG systems currently being introduced along with examples of their application in various physiological assessments. We believe that the widespread acceptance of IPPG is happening, and it will dramatically accelerate the promotion of this healthcare model in the near future.

/pdf/photoplethysmography-revisited-from-contact-to-noncontact-2jla840amb.pdf

Photoplethysmography Revisited: From Contact to Noncontact, From Point to Imaging

This paper presents a novel inductive loop sensor which detects large (e.g., bus) as well as small (e.g., bicycle) vehicles and help a traffic control management system in optimizing the best use of existing roads. To accomplish the sensing of large as well as a small vehicle, a multiple loop inductive sensor system is proposed. The proposed sensor structure not only senses and segregates the vehicle type as bicycle or motor cycle or car or bus but also enables accurate counting of the number of vehicles that too in a mixed traffic flow condition. A prototype of the multiple loop sensing system has been developed using a virtual instrumentation scheme and tested. Field tests indicate that the prototype successfully detected all types of vehicles and counted, correctly, the number of each type of vehicles. Thus the suitability of the proposed multi loop sensor system for any type of traffic has been established.

A multiple loop vehicle detection system for heterogeneous and lane-less traffic

A high accuracy switched capacitor, triple slope digital converter suitable for differential capacitive sensors is presented. The proposed technique accepts differential capacitive sensors possessing either linear or inverse characteristics and provides a linear capacitance to digital conversion. The output is dependent only on a pair of d.c. reference voltages and the clock frequency. Detailed analysis of the proposed scheme establishes that the sensitivity of the scheme to parameter variations is minimal. A prototype implemented and tested for a typical differential capacitive transducer of full-scale ±250 pF gave a worst-case error less than 0.05%.

Switched capacitor triple slope capacitance to digital converter

A non-invasive method of ascertaining the hemoglobin content in blood is presented here. The method proposed here uses a couple of photo-plethysmo-graphic (PPG) signals obtained by illuminating an extremity such as a finger or earlobe with monochromatic light at two different wavelengths. An empirical equation for calculation of hemoglobin content in blood is derived using a model for attenuation of light through skin-bone-tissue-blood in that extremity, well known extinction coefficients of hemoglobin (with and without oxygen) and data collected from a clinical study. The availability of PPGs at two different wavelengths facilitates the computation of, apart from hemoglobin content, heart rate, heart rate variability and oxygen saturation in arterial blood (SpO
 2
) as well.

Non-invasive measurement of hemoglobin content in blood

Data processing of stress ECGs using discrete cosine transform

A direct digital converter that provides a digital output, proportional to the measurand being sensed by a single active element resistive sensor is presented in this paper. To accomplish this task, the structure and the switching sequence of a conventional dual slope, analog to digital converter (DSADC) is appropriately altered so that the altered DSADC accepts the resistance of the sensor as an integral part and provides a digital output that is linearly proportional to the physical quantity being sensed by the resistive sensor. Since the output of the dual slope resistance to digital converter (DSRDC) is dictated only by the magnitudes of a pair of DC reference voltages, a fixed value resistor and the transformation constant of the sensor, the error in the output is minimal. Hence, a high level of linearity and accuracy is achieved. Simulation studies establish the efficacy of the proposed scheme.

V. Jagadeesh Kumar

Papers

A multiple loop vehicle detection system for heterogeneous and lane-less traffic

Switched capacitor triple slope capacitance to digital converter

Non-invasive measurement of hemoglobin content in blood

Data processing of stress ECGs using discrete cosine transform

Direct digital converter for a single active element resistive sensor