A review of machine learning techniques in photoplethysmography for the non-invasive cuff-less measurement of blood pressure

Hypertension or high blood pressure is a leading cause of death throughout the world and a critical factor for increasing the risk of serious diseases, including cardiovascular diseases such as stroke and heart failure. Blood pressure is a primary vital sign that must be monitored regularly for the early detection, prevention and treatment of cardiovascular diseases. Traditional blood pressure measurement techniques are either invasive or cuff-based, which are impractical, intermittent, and uncomfortable for patients. Over the past few decades, several indirect approaches using photoplethysmogram (PPG) have been investigated, namely, pulse transit time, pulse wave velocity, pulse arrival time and pulse wave analysis, in an effort to utilise PPG for estimating blood pressure. Recent advancements in signal processing techniques, including machine learning and artificial intelligence, have also opened up exciting new horizons for PPG-based cuff less and continuous monitoring of blood pressure. Such a device will have a significant and transformative impact in monitoring patients’ vital signs, especially those at risk of cardiovascular disease. This paper provides a comprehensive review for non-invasive cuff-less blood pressure estimation using the PPG approach along with their challenges and limitations

Robot programming by demonstration through system identification

Increasingly, personalised robots — robots especially designed and programmed for an individual’s needs and preferences — are being used to support humans in their daily lives, most notably in the area of service robotics. Arguably, the closer the robot is programmed to the individual’s needs, the more useful it is, and we believe that giving people the opportunity to program their own robots, rather than programming robots for them, will push robotics research one step further in the personalised robotics field. However, traditional robot programming techniques require specialised technical skills from different disciplines and it is not reasonable to expect end-users to have these skills. In this paper, we therefore present a new method of obtaining robot control code — programming by demonstration through system identification which algorithmically and automatically transfers human behaviours into robot control code, using transparent, analysable mathematical functions. Besides providing a simple means of generating perception-action mappings, they have the additional advantage that can also be used to form hypotheses and theoretical analysis of robot behaviour. We demonstrate the viability of this approach by teaching a Scitos G5 mobile robot to achieve wall following and corridor passing behaviours

Learning by observation through system identification

In our previous works, we present a new method to program mobile robots —“code identification by demonstration”— based on algorithmically transferring human behaviours to robot control code using transparent mathematical functions. Our approach has three stages: i) first extracting the trajectory of the desired behaviour by observing the human, ii) making the robot follow the human trajectory blindly to log the robot’s own perception perceived along that trajectory, and finally iii) linking the robot’s perception to the desired behaviour to obtain a generalised, sensor-based model. So far we used an external, camera based motion tracking system to log the trajectory of the human demonstrator during his initial demonstration of the desired motion. Because such tracking systems are complicated to set up and expensive, we propose an alternative method to obtain trajectory information, using the robot’s own sensor perception. In this method, we train a mathematical polynomial using the NARMAX system identification methodology which maps the position of the “red jacket” worn by the demonstrator in the image captured by the robot’s camera, to the relative position of the demonstrator in the real world according to the robot. We demonstrate the viability of this approach by teaching a Scitos G5 mobile robot to achieve door traversal behaviour

Debts of Cyprus Households: Lessons from the First Cyprus Survey of Consumer Finances

This paper describes participation of Cyprus households in various debts using data from the first (1999) Cyprus Survey of Consumer Finances. It complements our previous paper that described household participation in various types of assets (Haliassos et al., 2001). Debts considered encompass personal unsecured loans, including credit card debt, and loans secured by housing collateral, mainly mortgage debt. Findings are of policy interest, as they show the extent of household participation in various loans, and the indebtedness of various demographic groups. We document considerable popularity of credit cards as borrowing instruments despite their recent introduction, and a continuing parallel presence of antiquated forms of borrowing (informal store credits). There is surprisingly limited use by the young of mortgages, despite very high homeownership rates, and of car loans, despite high car ownership rates. We find evidence of considerable reliance on family transfers for the financing of education, home acquisition, and car purchase by the young. Particularly problematic for equality of opportunities is the limited ability of the young to take student loans and the reliance on their parents to do so in order to finance their post-secondary education. Finally, we have noted a tendency of Cyprus business owners to take out large loans from their business for personal use.

Debts of Cyprus Households: Lessons from the First Cyprus Survey of Consumer Finances

This paper describes the participation of Cyprus households in various types of debt using data from the first (1999) Cyprus Survey of Consumer Finances. It complements the 2001 paper by Haliassos et al. The findings are of interest to policy makers, as they show the extent of household participation in various loans and the indebtedness of various demographic groups. We document the considerable popularity of credit cards as borrowing instruments and a continuing parallel presence of antiquated forms of borrowing. There is surprisingly limited use by the young of mortgages, despite very high home ownership rates, and of car loans, despite high car ownership rates. We find evidence of a strong reliance on family transfers for the financing of higher education, home acquisitions and car purchases by the young. Finally, we note a tendency for Cypriot entrepreneurs to take out large loans from their business for personal use.

Assets of Cyprus Households: Lessons from the first Cyprus Survey of Consumer Finances

This paper describes participation of Cyprus households in financial and real assets using new data from the 1999 Cyprus Survey of Consumer Finances, and compares Cyprus to the United States and four major European countries. Almost 9 out of 10 Cyprus households own some financial asset. After checking accounts, the most popular financial asset is government savings bonds. One in two households participated in stocks directly or indirectly in 1999, a year of stock market frenzy, reaching participation levels comparable only to the United States. Despite the absence of mutual funds, almost one third of households invest in managed portfolios linked to life insurance, and this exceeds direct stockholding even in 1999. Participation in direct stockholding is higher than in other countries, overall and for households below 50 years, and unusually high for the very young. Potential sources of concern include the limited number of stocks held by direct stockholders, and the presence of a significant contingent with limited background. Diversification across risk categories of financial assets is limited, but the majority of those holding few assets do not hold stocks directly. Those who do hold stocks directly are poorly diversified across different stocks. More than one in two households have some form of life insurance, but participation in individual retirement accounts is very low. Participation in risky assets, financial or real, far exceeds that in other countries. Yet, a strong contingent of households concentrates on risky real assets and abstains from risky financial assets, even during 1999. Rates of ownership of real assets are exceptionally high compared to the other countries. Homeownership rates far exceed those in the United States, and the majority of homeowners own their home fully. One quarter of Cyprus households own business equity, more than double the rate in the United States.

Cuffless and Continuous Blood Pressure Estimation from PPG Signals Using Recurrent Neural Networks

This paper proposes cuffless and continuous blood pressure estimation utilising Photoplethysmography (PPG) signals and state of the art recurrent network models, namely, Long Short Term Memory and Gated Recurrent Units. The models were validated on wide range of varying blood pressure and PPG signals acquired from the Multiparameter Intelligent Monitoring in Intensive Care database. Many features were extracted from the PPG waveform and several machine learning techniques were employed in an attempt to eliminate collinearity and reduce the size of input feature vector. Consequently, the most effective features for blood pressure estimation were selected. Experimental results show that the accuracy of the proposed methods outperform traditional models applied in the literature. The results satisfy the American National Standards of the Association for the Advancement of Medical Instrumentation

Assets of Cyprus Households: Lessons from the First Cyprus Survey of Consumer Finances

This paper describes participation of Cyprus households in financial and real assets using new data from the 1999 Cyprus Survey of Consumer Finances, and compares Cyprus to the United States and four major European countries. Almost 9 out of 10 Cyprus households own some financial asset. After checking accounts, the most popular financial asset is government savings bonds. One in two households participated in stocks directly or indirectly in 1999, a year of stock market frenzy, reaching participation levels comparable only to the United States. Despite the absence of mutual funds, almost one third of households invest in managed portfolios linked to life insurance, and this exceeds direct stockholding even in 1999. Participation in direct stockholding is higher than in other countries, overall and for households below 50 years, and unusually high for the very young. Potential sources of concern include the limited number of stocks held by direct stockholders, and the presence of a significant contingent with limited background. Diversification across risk categories of financial assets is limited, but the majority of those holding few assets do not hold stocks directly. Those who do hold stocks directly are poorly diversified across different stocks. More than one in two households have some form of life insurance, but participation in individual retirement accounts is very low. Participation in risky assets, financial or real, far exceeds that in other countries. Yet, a strong contingent of households concentrates on risky real assets and abstains from risky financial assets, even during 1999. Rates of ownership of real assets are exceptionally high compared to the other countries. Homeownership rates far exceed those in the United States, and the majority of homeowners own their home fully. One quarter of Cyprus households own business equity, more than double the rate in the United States.

Review of Protocols Used in Ultrasound Thrombolysis

Objectives: This paper focuses on the review of protocols used in thrombolysis studies with ultrasound. Materials and methods: Data from peer-review articles were acquired. Results: The protocols of several published reports are summarized in 3 tables (in vitro, in vivo, and clinical), providing detailed information concerning clot model, thrombolytic drug, treatment mode, sonication parameters, evaluation method, thrombolysis outcome, side effects, and conclusions. Conclusions: The aim of this review was to give an overview of the different protocols used so far in the field of sonothrombolysis and investigate the impact of several aspects involved on sonothrombolysis outcome