The development of a portable optical system for telemonitoring of skin blood oxygen level

Oxygen is one of the keys parameters required for tissues metabolism to ensure life sustainability. Without it, human’s health would suffer and eventually result in fatal. Cells consume oxygen to break down sugar to produce adenosine triphosphate (ATP) during cellular respiration [1]. ATPs are the main source of energy for metabolic functions [2] and every cell in the body, especially muscles cell, for its ability to store and use energy; muscle would not contract or relax without ATP. Cell is not able to function well under the condition of low oxygen level, thus it would lead to hypoxemia. If left untreated, severe hypoxemia can be fatal [3]

Empirical Analysis Based on Light Attenuation Gradient of Wavelength Pairs for the Prediction of Skin Oxygen Status

An empirical technique that allows noninvasive prediction of skin oxygen saturation (SO2) using the absorption coefï¬cients of the preprocessing stored wavelength pairs is proposed. The highest probable SO2 value is decided by selecting the bin containing wavelength pairs that produce the smallest variation in the distribution of the calculated attenuation gradient value. The performance this technique was evaluated using Monte Carlo simulated data. The simulation results revealed that this technique worked reasonably well even at low SO2 condition with an overall mean error of not more than 2 %. This shows that the proposed analytic technique can potentially be used for measurement of the blood oxygen level of individuals with respiratory disease or with oxygen deprivation conditions such as hypoxic-hypoxia

An assessment of a GTEM cell as a test environment using measurements and simulations

The Gigahertz Transverse Electromagnetic (GTEM) cell was developed about 20 years ago and the applications using GTEM cells for electromagnetic compatibility (EMC) measurements are continuously increasing. The research described in this Thesis proposes a new method for characterizing emissions from electrical appliances using a GTEM cell. The research adapts the method used in the Transverse Electromagnetic (TEM) cell where the measurements are done by using a two-port system which includes a phase measurement. This is a restriction in GTEM cells because only one port exists and normally only the magnitude reading can be performed. This requires the development and application of new techniques, which allow the description of emitters in terms of equivalent electric and magnetic dipoles measured using a GTEM cell with phase measurement. A full field 3D Transmission Line Model (TLM) model of a GTEM cell is generated. Further simulations based on this model were performed to assess the behaviour of the emitters and when the GTEM cell is under actual working conditions. The model is also used to validate results obtained from measurements. The assumption that the dipole moments from a general emitter are in phase is also studied and evidence is presented to assess the validity of this assumption. The impact of the phase variations within an EUT towards the total radiated power estimated according to IEC 61000-4-20 is discussed and a technique to measure phase using a GTEM cell is introduced

An assessment of a GTEM cell as a test environment using measurements and simulations

The Gigahertz Transverse Electromagnetic (GTEM) cell was developed about 20 years ago and the applications using GTEM cells for electromagnetic compatibility (EMC) measurements are continuously increasing. The research described in this Thesis proposes a new method for characterizing emissions from electrical appliances using a GTEM cell. The research adapts the method used in the Transverse Electromagnetic (TEM) cell where the measurements are done by using a two-port system which includes a phase measurement. This is a restriction in GTEM cells because only one port exists and normally only the magnitude reading can be performed. This requires the development and application of new techniques, which allow the description of emitters in terms of equivalent electric and magnetic dipoles measured using a GTEM cell with phase measurement. A full field 3D Transmission Line Model (TLM) model of a GTEM cell is generated. Further simulations based on this model were performed to assess the behaviour of the emitters and when the GTEM cell is under actual working conditions. The model is also used to validate results obtained from measurements. The assumption that the dipole moments from a general emitter are in phase is also studied and evidence is presented to assess the validity of this assumption. The impact of the phase variations within an EUT towards the total radiated power estimated according to IEC 61000-4-20 is discussed and a technique to measure phase using a GTEM cell is introduced

Soil moisture level prediction using optical technique and artificial neural network

This research describes the use of an optical system combined with artificial neural network (ANN) for wireless and nondestructive prediction of soil moisture level. The former system comprising of near infrared (NIR) emitters of wavelengths 1200 nm and 1450 nm, and a photodetector for near real time soil moisture measurement in loams and peats holding different amount of water. There were 63 and 90 sets of data from loams and peats, respectively, used in the development of the dual stage-multiclass ANN model, wherein measurement of light attenuation (from nondestructive system) was correlated with percent soil moisture (from destructive gold standard approach) in pre-measurement stage. The result revealed a relatively good performance in the training of the NN with regression, R, of 0.8817 and 0.8881, and satisfactory error performance of 0.7898 and 1.172, for loams and peats, respectively. The testing of the system on 50 new samples of loam and peat showed a considerably high mean accuracy of 92 % for loams while 82 % was observed for peats. This study attributes the poorer performance of the system used on peats to the detection resolution of percent soil moisture, and structure and properties of the corresponding soil. This work concluded that the developed technology may be feasible for use in the future design and improvement of agricultural soil management

Modified lambert beer for bilirubin concentration and blood oxygen saturation prediction

Noninvasive measurement of health parameters such as blood oxygen saturation and bilirubin concentration predicted via an appropriate light reflectance model based on the measured optical signals is of eminent interest in biomedical research. This is to replace the use of conventional invasive blood sampling approach. This study aims to investigate the feasibility of using Modified Lambert Beer model (MLB) in the prediction of one’s bilirubin concentration and blood oxygen saturation value, SO2. This quantification technique is based on a priori knowledge of extinction coefficients of bilirubin and hemoglobin derivatives in the wavelength range of 440 – 500 nm. The validity of the prediction was evaluated using light reflectance data from TracePro raytracing software for a single-layered skin model with varying bilirubin concentration. The results revealed some promising trends in the estimated bilirubin concentration with mean ± standard deviation (SD) error of 0.255 ± 0.025 g/l. Meanwhile, a remarkable low mean ± SD error of 9.11 ± 2.48 % was found for the predicted SO2 value. It was concluded that these errors are likely due to the insufficiency of the MLB at describing changes in the light attenuation with the underlying light absorption processes. In addition, this study also suggested the use of a linear regression model deduced from this work for an improved prediction of the required health parameter values

Natural Killer Cells Phenotype in Antiretroviral Naïve HIV-1 Infected People Living in Cameroon

The impact of antiretroviral naïve HIV-1 infection on the modulation of Natural Killer (NK) cells phenotype has not been fully assessed. This study aimed to define the phenotype of NK cell in the context of antiretroviral naïve HIV-1 infection. A total of 85 ARV naïve HIV-1 infected and 55 healthy individuals were included in the study. Purified NK cells alongside bulk Peripheral Blood Mononuclear Cells (PBMC) were surface stained with fluorochrome conjugated antibodies and samples were acquired using a BD FACS canto II flow cytometer. A down-regulation of CD56 + /CD16 - and CD56 + /CD16 + NK cells (p= 0.003), and a significant expansion (p= 0.03) of CD56 - /CD16 + NK cells subset was observed in ARV naïve HIV-1 infection. The high expression of both CD38 (p= 0.02) and HLA-DR (p=0.001) in the CD56-/CD16+ NK cells subset, shows the activation status of NK cells from HIV-1 infected people. A reduced expression of activating markers NKp44 and NKp30 and the down regulation of NKG2A was observed  in CD56+/CD16- and CD56+/CD16+ NK cells from HIV-1 infected people (p= 0.006, p= 0.009, respectively).  Antiretroviral naive HIV-1 infected people living in Cameroon show a differential modulation of NK cell phenotype relative to HIV negative controls

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Empirical Analysis Based on Light Attenuation Gradient of Wavelength Pairs for the Prediction of Skin Oxygen Status

An empirical technique that allows noninvasive prediction of skin oxygen saturation (SO2) using the absorption coefï¬cients of the preprocessing stored wavelength pairs is proposed. The highest probable SO2 value is decided by selecting the bin containing wavelength pairs that produce the smallest variation in the distribution of the calculated attenuation gradient value. The performance this technique was evaluated using Monte Carlo simulated data. The simulation results revealed that this technique worked reasonably well even at low SO2 condition with an overall mean error of not more than 2 %. This shows that the proposed analytic technique can potentially be used for measurement of the blood oxygen level of individuals with respiratory disease or with oxygen deprivation conditions such as hypoxic-hypoxia