Matti Huotari

Blowfly olfactory biosensor's sensitivity and specificity

In this article we introduce an insect (blowfly Calliphora vicina) olfactory biosensor. This biosensor has proved sensitive to the vapour of biogenic amines, and especially to 1,4-diaminobutane. According to our electrophysiological experiments the blowfly olfactory biosensor was sensitive to the 1,4-diaminobutane odour (<1 ng in stimulus air pulse), but less sensitive to 1,3-diaminopropane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane and ammoniac odour (<100 μg on stimulus cartridge). Based on time to voltage conversion and visual inspection we have determined the action potential rate as the response value. Also according to our behavioural tests the odour of 1,4-diaminobutane attracted clearly the blowflies.

Monitoring arterial pulse waves with synchronous body sensor network.

A wireless body sensor network for arterial pulse wave (PW) measurements is presented and tested with ten subjects. The system is capable of recording both mechanical PW contours with sensors made of a low-cost polypropylene-based material called electromechanical film (EMFi) and volume pulse signal with photoplethysmographic transducers. By using both types of sensors, the PW contours can be recorded from various locations. The system combined with automatic analysis methods enables to easily analyze the PW contours in order to obtain a more comprehensive view on the vascular health. To demonstrate this, two parameters used in literature, reflection index and radial augmentation index were calculated for the test subjects as a function of time. The results show that these parameter values may vary more than 20% in a period of 100 s, which suggests that a large number of PWs should be analyzed before making conclusions based on the calculated indices. In addition, the effects of the static bias force to the mechanical PW signal recorded with the EMFi sensors were studied. The PW signal with the maximum amplitude is obtained when the pressure caused by the static bias force corresponds to the contact pressure between typical systolic and diastolic blood pressures. The EMFi sensors used in the proposed system are a potential low-cost alternative for tonometric sensors in collecting data in the PW analysis for arterial screening.

Combining finger and toe photoplethysmograms for the detection of atherosclerosis

In this study, we propose and analyze a noninvasive method for detecting the atherosclerotic changes of vasculature based on the analysis of photoplethysmographic (PPG) signals. METHODS the proposed method is called finger-toe (FT)-plot analysis that utilizes both finger and toe PPG signals. For the features extracted from the FT-plots, we implemented different linear discriminant analysis based classifiers and analyzed seven promising ones in detail. We used the signals recorded from altogether 75 test subjects (categorized as 27 atherosclerotic patients and 48 control subjects based on ankle brachial pressure index, symptoms and disease history) in the training, and testing of the method. Besides leave one out cross validation, we tested the method by using training data independent signals recorded with two different PPG devices. The performance of the FT-plot is compared with other indicators related to the risk of cardiovascular diseases. RESULTS we found an average area under ROC (receiver operating characteristic) curve of [Formula: see text] (mean  ±  standard deviation based on different datasets), sensitivity of [Formula: see text], specificity of [Formula: see text], accuracy of [Formula: see text], performance of [Formula: see text] and positive and negative predictive values of [Formula: see text] and [Formula: see text], respectively, for the different tested classifiers. CONCLUSIONS the study shows that the FT-plot analysis could be a useful additional tool for detecting atherosclerotic changes. Our findings provide evidence for the utility of multi-channel pulse wave measurements and analysis for the detection of atherosclerosis. This may facilitate development of novel early diagnostic approaches and preventive strategies.

Arterial pulse wave analysis based on PPG and EMFi measurements

Photoplethysmography (PPG) is an optical measurement technique either in reflective or transmission mode over the skin. PPG amplitudes depend on light wavelength which is typically in near infrared region. Eletromechanical film (EMFi) is an excellent sensor material for low-current long-term applications, e.g., arterial pulse wave recordings. EMFi measures extremely very small movements of the arterial wall and the tissue around the artery on the skin whereas PPG measures very low light absorption, transmission, and scattering caused by oxihemoglobin. Both PPG and EMFi sense elastic wave recoil, impact, and reflection caused by left ventricular contraction. Each type of pulse waves can be analysed in different ways, but they are extensively synergetic. Analysis type (PSD, PDF, NPWD, SDPPG, SDEMFi) shows different information.

Radial artery pulse wave measurement by photoplethysmograpy and compound pulse wave decomposition

Cardiovascular diseases are the worlds largest killers, claiming 17.1 million lives a year (WHO 2009). Most countries face high and increasing rates of cardiovascular disease. High arterial stiffness is a symptom and increases the risk of cardiovascular diseases. Arteries stiffen normally as a consequence of age, but also because of arteriosclerosis. Age related stiffness occurs when the elastic fibers within the arterial walls begin to weaken due to age, but diseases as arteriosclerosis accelerate this process.

Infrared and red PPG signals analysis of the healthy subjects and clinical patients

A lab-made photoplethysmographic (PPG) device was applied to measure PPG signals of healthy cohorts and selected patients by medical doctors for arterial elasticity assessment. The off-line analysis on vascular health was done afterwards using a commercial software. The received information is repeatable and reproducible, however, sometimes not unambiguous. Temporal parameters of the signal components were studied in order to define the invariants by means of optimal envelope construction. After PPG pulse series normalization the series were twice differentiated and the maxima (A) and minima (B) of the second order derivative PPGs (SDPPG) were determined. The constructed graphs of the ratios B/A as a function of time were produced for the healthy compared with the vascular patients. Also principal component analysis (PCA) was used in decomposing the PPG signal for finding functional relationships between components. The 30-points moving averages were calculated for B/A value series of each SDPPG signals which is presented as the result. The B/A index shows higher values for the finger arteries compared the toe arteries. The infrared based B/A index values were higher than the red based B/A index values, and finger B/A index values were higher than toe B/A index values. The main goal for this study the noninvasive method for arterial elasticity assessment based on clinical and volunteer measurements with PPG & SDPPG means.

Photoplethysmographic Measurements of Finger/Toe Arterial Pulse Waveforms and Their Compound Time Domain Analysis

Optical methods, especially, photoplethysmography (PPG) is an interesting and valuable method in studying human circulatory physiology. This novel model makes it possible to estimate very accurately mechanical properties of arteries. This estimation is based on the analysis of the arterial pulse waveforms and their compound decomposition analysis derived from photoplethysmographic measurements.

Arterial stiffness estimation based photoplethysmographic pulse wave analysis

Arterial stiffness is one of the indices of vascular healthiness. It is based on pulse wave analysis. In the case we decompose the pulse waveform for the estimation and determination of arterial elasticity. Firstly, optically measured with photoplethysmograph and then investigating means by four lognormal pulse waveforms for which we can find very good fit between the original and summed decomposed pulse wave. Several studies have demonstrated that these kinds of measures predict cardiovascular events. While dynamic factors, e.g., arterial stiffness, depend on fixed structural features of the vascular wall. Arterial stiffness is estimated based on pulse wave decomposition analysis in the radial and tibial arteries. Elucidation of the precise relationship between endothelial function and vascular stiffness awaits still further study.

Photoplethysmographic Measurements on Clinical Patients (>65 y) and Healthy Cohorts Between Ages of 18–75 y

The biomedical information on different indexes like arterial elasticity index (AEI), arterial age (AA) is used in many cases. However, they applicability for diseases earlier prediction like arteriosclerosis (AS) is seldom applied. Many illnesses are becoming common, especially cardiovascular disorders (CVD) among elderly people, and in females. It is predicted that the negative impacts of AS on young people can be greater than on the elderly people in the long run because of sedentary lifestyle. Degenerative changes in the arteries have many causes in addition to the lifestyle. Arterial elasticity (AE) would provide a direct indicator for cardiovascular healthiness and predict AS. AE can be challenging in the cases of elderly, but also in the case of the young persons whose endothelial functions have been earlier very good. The vessel properties would be important to know for characterization of both arterial diseases and the development of reliable devices. Photoplethysmography (PPG), and especially its response pulse wave decomposition, envelope analysis, and its second order derivative (SDPPG) open the new health information for clinics. PPG signals are correlated with the alterations in blood pressure, blood flow, arterial elasticity, and health indexes. Exposure of human to physical exercise has been shown to improve endothelial function in patients with risk factors and heart failure. Exercise has been shown to be protective to cardiovascular disease. In addition according to this study, the exact mathematical solution for the pulse wave analysis has be replaced by numerical analysis method. In addition, a probability density function and a coherence function suits well to the inherent resting PPG process, and giving some intrinsic properties of the arterial pulsation phenomena.

Short-term stability of combined finger and toe photoplethysmogram analysis

Arterial pulse waves (PWs) provide information on the vascular health and could be utilized in the early detection of atherosclerosis. The aim of the study is to characterize the short-term repeatability of combined finger and toe photoplethysmographic (PPG) signal analysis method which we call finger-toe plot (FT-plot) and compare it with other methods proposed for vascular characterization. PPG signals were recorded from 24 atherosclerotic and 47 control subjects from finger and toe. The repeatability of the method was analyzed by means of intra-class correlation coefficients (ICC) and free-marginal multirater \(\kappa \) agreement. The metrics were computed for individual PWs as well as for averages based on 10–100 PWs. The ICCs increased with number of PWs utilized — ICCs and \(\kappa \) agreements higher than \(\ge 0.90\) were widely achieved based on the averages of \(\ge 20\) PWs, depending on the parameter or study group. Based on the present results, the FT-plot based detection of atherosclerotic changes has at least equal repeatability compared with a current clinical standard, ankle-to-brachial pressure index. However, further studies should validate the findings before the method is ready for the screening of atherosclerotic changes.