Non-invasive Measurement Method Research Articles

Novel Blood Pressure Waveform Reconstruction from Photoplethysmography using Cycle Generative Adversarial Networks.

Continuous monitoring of blood pressure (BP) can help individuals manage their chronic diseases such as hypertension, requiring non-invasive measurement methods in free-living conditions. Recent approaches fuse Photoplethys-mograph (PPG) and electrocardiographic (ECG) signals using different machine and deep learning approaches to non-invasively estimate BP; however, they fail to reconstruct the complete signal, leading to less accurate models. In this paper, we propose a cycle generative adversarial network (CycleGAN) based approach to extract a BP signal known as ambulatory blood pressure (ABP) from a clean PPG signal. Our approach uses a cycle generative adversarial network that extends the GAN architecture for domain translation, and outperforms state-of-the-art approaches by up to 2× in BP estimation.

The use of PIV methods in the study of two-phase flows in small diameter channels

The PIV (Particle Image Velocimetry) method is one of the optical, non-invasive measurement methods for measuring fluid velocity and can be used in the study of two-phase gas-liquid flows to determine velocity fields. The velocity distribution of the liquid and gas phases influences the formation of two-phase flow structures and, consequently, the mechanisms of energy and moment exchange in the two-phase flow. The article concerns the application of the PIV method to the assessment of hydrodynamic phenomena occurring during two-phase flow realized in pipe minichannels with an internal diameter d > 2 mm. Fluorescent marker particles with a density close to that of water were used in the research. The preliminary tests were carried out on the adiabatic water-air mixture. The research aimed to check the applicability of PIV methods also in non-adiabatic flows. As a result of preliminary studies, velocity maps of the liquid phase, histograms and velocity profiles in the vertical section of the tested minichannel were obtained.

Experimental Study on the Transport and Alteration Behavior of Aerosols From Low Density Powders for Acute Inhalation Toxicology Studies.

Low density powders have a bulk density of less than 100 kg/m3 and are produced technically by flame pyrolysis of silicon tetrachloride (pyrogenic powders such as pyrogenic silica) or wet-chemically by sol-gel processes (e.g. silica-gel) or precipitation reactions using sodium silicate solution and a mineral acid. The transport and alteration behavior of aerosols from low density powders was investigated in a device for toxicological inhalation studies. The test conditions corresponded to those for acute toxicology studies according to OECD Guideline 436. The use of cascade impactors, required by guideline, has not proven successful for low density powders as the fragile agglomerate structures are destroyed during the measurement. As an alternative and non-invasive measurement method, laser diffraction spectroscopy has proved very successful in the present investigations. In particular, aerosols from pyrogenic powders of low density showed a distinctive tendency to re-agglomerate, especially at concentrations >500 mg/m3mm3. Investigation results indicate that aerosol particle size must be monitored over the entire acute inhalation test period for acute inhalation studies to be performed reliably.

Airspace Dimension Assessment with Nanoparticles (AiDA) in Comparison to Established Pulmonary Function Tests.

BackgroundAirspace Dimensions Assessment with nanoparticles (AiDA) is a new method for non-invasive measurement of pulmonary distal airspaces. The aim of this study was to compare AiDA measurements with other pulmonary function variables to better understand the potential of AiDA in a clinical context.MethodsAiDA measurements and pulmonary function tests were performed in 695 subjects as part of the Swedish CArdioPulmonary bioImage Study. The measurement protocol included spirometry, measurement of diffusing capacity of carbon monoxide, oscillometry and pulmonary computed tomography. AiDA indices were compared to all other pulmonary examination measurements using multivariate statistical analysis.ResultsOur results show that AiDA measurements were significantly correlated with other pulmonary function examination indices, although covariance was low. We found that AiDA variables explained variance in the data that other lung function variables only influenced to a minor extent.ConclusionWe conclude that the AiDA method provides information about the lung that is inaccessible with more conventional lung function techniques.

CENTRAL BLOOD PRESSURE MEASUREMENT IN CHILDREN AND ADOLESCENTS: SYSTEMATIC REVIEW

Objective: Central aortic blood pressure (BP) has attracted the researchers interest due to its potential to improving cardiovascular risk stratification. We reviewed the published data on central BP in children and adolescents excluding those with chronic heart, lung or kidney disease, congenital anomaly or syndrome, malignancy, and acute illness. Design and method: A systematic review of literature based on PubMed database was conducted by two independent researchers up to January 2021 in accordance with the PRISMA guidelines. Additional studies were identified from the reference lists of relevant articles. Results: A total of 56 eligible articles were identified (Table). The available literature advocates a positive association between male gender, age, height, African-American descent, preterm birth, hypertension and diabetes with central BP, whereas the association of birth weight and physical exercise with central BP was inverse. Regarding the relationship of central BP with indices of preclinical target organ damage, 11 studies showed a positive association with pulse wave velocity, 7 with left ventricular mass index, 5 with carotid intima-media thickness, and 4 with augmentation index. Two studies reported an inverse association with the equivalent of the central retinal artery. The studies testing non-invasive techniques for central BP estimation reported that they approach the invasive technique with adequate accuracy, with crucial impact of the calibration method. Tonometry remains the most studied non-invasive measurement method, followed by oscillometry. Two studies provided normalcy values using the oscillometric method. The evidence on 24-hour ambulatory central BP is limited. Conclusions: The evidence on central BP measurement in youth is limited and derived from non-invasive evaluation in static conditions using tonometry. Central BP in children and adolescents seems to be affected by multiple factors and is associated with preclinical target organ damage.

Two Dimensional and Stereo PIV Comparison for Port Applications

Fuel-air movements in-cylinder are one of the most critical diesel engine parameters to determine engine performance and emission. Swirling movement in the engine combustion chamber is investigated advanced experimental techniques to improve the air intake design.
 Honeycomb measurement method and PIV (particle image velocimetry) method are used to measure the swirling airflow. The honeycomb measurement method can directly measure the swirl. However, it does not give detail information about the flow field. On the other hand, the PIV technique is one of the non-invasive measurement methods for swirl measurement. PIV can directly measure the velocity vector of the cylinder section. 
 In this study, the honeycomb measurement method was performed to measure the swirl ratio of 13L and 9L engines. The uncertainty analysis was determined for the reliability ratio of the measurement. In addition, PIV measurements are performed to understand the velocity field of the cylinder section. This velocity field gives detailed information about the center of the swirl and the velocity index of the velocity field.

Application of Dual Frequency Comb Method as an Approach to Improve the Performance of Multi-Frequency Simultaneous Radiation Doppler Radar for High Temperature Plasma Diagnostics

A new Doppler radar using millimeter-waves in the Ka-band, named the “dual-comb Doppler reflectometer”, has been developed to measure the turbulence intensity and its velocity in high-temperature plasmas. For the realization of a fusion power generation, it is very important to know the spatial structure of turbulence, which is the cause of plasma confinement degradation. As a non-invasive and high spatial resolution measurement method for this purpose, we apply a multi-frequency Doppler radar especially with simultaneous multi-point measurement using a frequency comb. The newly developed method of synchronizing two frequency combs allows a lower intermediate frequency (IF) than the previously developed frequency comb radar, lowering the bandwidth of the data acquisition system and enabling low-cost, long-duration plasma measurements. In the current dual-comb radar system, IF bandwidth is less than 0.5 GHz; it used to be 8 GHz for the entire Ka-band probing. We applied this system to the high-temperature plasma experimental device, the Large Helical Device (LHD), and, to demonstrate this system, verified that it shows time variation similar to that of the existing Doppler radar measurements.

MO726: Skin Autofluorescence Profile in Tunisian Hemodialysis Patients with and Without Heart Failure

Abstract BACKGROUND AND AIMS Cardiovascular disease (CVD) is the main reason for morbidity and mortality of patients in hemodialyis. Skin autofluorescence (SAF), a noninvasive measurement method, reflects tissue accumulation of advanced glycation end products (AGEs) that have been implicated in CVD as a strong marker. The aim of this study was to evaluate the SAF profile in hemodialysis patients and to assess the association between SAF and heart failure. METHOD In a cross-sectional study, we included 60 hemodialysis (HD) patients who were divided into two groups: a HD group without heart failure (n = 42) and a HD group with heart failure (n = 18). Skin AGE accumulation was measured by the AGE reader device and clinical data was obtained. RESULTS HD patients showed an SAF value at 2.90 (2.40–3.60). HD patients with diabetes mellitus has an increased SAF levels compared with HD patients without diabetes [3.20 (2.90–3.95) versus 2.70 (2.30–3.30) AU, P = 0.021, respectively]. Furthermore, HD patients with heart failure showed a significant increased SAF levels compared with HD patients without heart failure [3.65 (2.90–4.12) versus 2.60 (2.30–3.20) AU; P < 0.001, respectively]. SAF was associated with age, gender and duration of dialysis. The ROC analysis indicated that SAF at 3.05 AU was the optimal cut-off point for the presence of heart failure (P < 0.001). CONCLUSION SAF might be a rapid and helpful tool in clinical practice as a potential marker for evaluating and screening heart failure in HD patients non-invasively and might be used as a predictor for clinicians.

Echocardiographic Evaluation of Initial Ambrisentan Plus Phosphodiesterase Type 5 Inhibitor on Right Ventricular Pulmonary Artery Coupling in Severe Pulmonary Arterial Hypertension Patients.

Introductionambrisentan and phosphodiesterase type 5 inhibitor (PDE5i) have been approved for treating patients with pulmonary arterial hypertension (PAH). Echocardiographic right ventricular pulmonary artery coupling (RVPAC) has been shown to be a valid non-invasive and alternative measurement method to assess the predicted outcomes in PAH patients. The aim of this study was to study the effect and clinical correlates of initial ambrisentan plus PDE5i combination therapy on RVPAC in patients with severe PAH.Method and ResultsWe retrospectively studied and analyzed comprehensive clinical data, hemodynamics, and echocardiography in 27 patients with severe PAH before and after 6 months of initial combination therapy. Compared with the baseline, significant improvements in RVPAC ratios were observed, including RVFAC/PASP (0.31 ± 0.10 vs. 0.44 ± 0.15%/mmHg, p < 0.001), TAPSE/PASP (0.15 ± 0.05 vs. 0.21 ± 0.06 mm/mmHg, p = 0.001), S’/PASP (0.10 ± 0.03 vs. 0.14 ± 0.05 cm/s∙mmHg, p = 0.001), and RVSV/RVESV (0.79 ± 0.22 vs. 1.02 ± 0.20, p < 0.001). Functional status indices [World Health Organization functional classifications (WHO-FC) and 6 min walk distance (6MWD) and N-terminal pro B-type natriuretic peptide (NT-proBNP) levels] showed significant improvements. Right heart catheterization (RHC) evaluations for hemodynamic measurements between baseline and the 6–12 month follow-up were sPAP (96 ± 22 vs. 86 ± 24 mmHg, p = 0.002), mPAP (64 ± 18 vs. 56 ± 17 mmHg, p < 0.001) and TPVR (17.3 ± 6.7 vs. 12.1 ± 5.4 WU, p = 0.001). Simultaneously, significant associations between RVPAC ratios and NT-proBNP levels and WHO-FC and 6MWD were observed.ConclusionAmbrisentan plus PDE-5i combination therapy resulted in a significant improvement in RVPAC in severe PAH. Importantly, RVPAC parameters correlated with known prognostic markers of PAH.

Estimating the total length of Mekong giant catfish, Pangasianodon gigas, in an aquarium via stereo-video shooting and direct linear transformation.

The Mekong giant catfish (MGC), Pangasianodon gigas, is one of the world's largest catfish species. Endemic to the Mekong River system, the MGC is critically endangered. Six MGC were transported from Thailand to the Gifu World Freshwater Aquarium (GWFA) in Japan in May 2004. The MGC have not been measured since they were introduced to the GWFA due to the challenges associated with their large size. Traditional methods, such as anesthesia and net-capture, could harm the fish, potentially reducing the population further. However, understanding the ecology of the species is essential to conservation efforts. Seasonal feeding rhythms and long-term fasting were previously observed in captive MGCs. To investigate the effect of long-term fasting on MGC growth, total length measurements are necessary. In this study, we applied a noncontact method to estimate the total length via image analysis. We shot a stereo-video of free-swimming MGC in the aquarium tank using two digital video cameras and analyzed the 3D images using the direct linear transformation method. We successfully estimated the total length of each MGC individual without contacting the fish. This accurate estimation method is versatile, simple, and useful in aquarium breeding and is also recommended from the viewpoint of animal welfare because it is a noninvasive method of measurement.

Elevated intra-abdominal pressure: A review of current knowledge.

Elevated intra-abdominal pressure (IAP) is a known cause of increased morbidity and mortality among critically ill patients. Intra-abdominal hypertension (IAH) and abdominal compartment syndrome can lead to rapid deterioration of organ function and the development of multiple organ failure. Raised IAP affects every system and main organ in the human body. Even marginally sustained IAH results in malperfusion and may disrupt the process of recovery. Yet, despite being so common, this potentially lethal condition often goes unnoticed. In 2004, the World Society of the Abdominal Compartment Syndrome, an international multidisciplinary consensus group, was formed to provide unified definitions, improve understanding and promote research in this field. Simple, reliable and nearly costless standardized methods of non-invasive measurement and monitoring of bladder pressure allow early recognition of IAH and timely optimized management. The correct, structured approach to treatment can have a striking effect and fully restore homeostasis. In recent years, significant progress has been made in this area with the contribution of surgeons, internal medicine specialists and anesthesiologists. Our review focuses on recent advances in order to present the complex underlying pathophysiology and guidelines concerning diagnosis, monitoring and treatment of this life-threatening condition.

A noninvasive method of temperature measurement using a noncontact handheld infrared thermometer fails to correlate with rectal temperature in dogs and cats.

To perform a retrospective, multicenter observational study that compares the agreement of rectal temperature with the temperature measured with noncontact infrared thermometer (NCIT) in a population of dogs and cats. 168 dogs and 61 cats. NCIT readings were taken in triplicate from the medial pinna, then rectal temperature was taken with a standard digital rectal thermometer (RT). Ambient room temperature, signalment, presence of icterus, skin and coat color, reason for presentation, and final diagnosis were recorded. In dogs, median (range) body temperature reflected by RT and NCIT measurements was 38.4 °C (33.4 to 40.3 °C) and 36.3 °C (30.8 to 40.0 °C), respectively. In cats, median (range) body temperature reflected by RT and NCIT measurements was 38.3 °C (36.2 to 40.0 °C) and 35.7 °C (31.8 to 38.0 °C), respectively. There was a weak positive correlation between body temperatures measured by NCIT and RT in dogs (Kendall tau = 0.154), but there was no correlation in cats (Kendall tau = -0.01). A significant, albeit weak, agreement was seen between temperature measured by NCIT and RT in dogs (Kappa value, 0.05), but not cats (Kappa value, -0.08). In both species, NCIT tended to underread body temperature, compared with RT (dogs: mean ± SD bias -2.2 ± 1.51 °C; cats: mean bias -2.7 ± 1.44 °C), with the degree of low measurements lessening as body temperature increased. Given both poor correlation and agreement in body temperature measured by NCIT and rectal thermometer, NCIT measurements cannot be recommended at the current time as a means to determine body temperature in dogs and cats.

Temperature measurement based on the magneto-optic Kerr effect in Ni nanofilms

Thermometry is essential in laboratory and industry settings. We propose a noninvasive temperature measurement method based on the superparamagnetic properties of nickel-plated films. When the nickel (Ni) film is uniformly heated from 100 K to 300 K, we observe that the polarization angle of the reflected polarized light decreases correspondingly. Compared with optical temperature measurement, this method introduces magnetic physical quantity, which increases the penetration of temperature measurement. Compared with magnetic temperature measurement, this method introduces optical physical quantity, which greatly increases the amount of information contained in the measurement channel. On this basis, we introduce the characteristic matrix of membrane system, and the improved the mean field theory which can interpret superparamagnetism. Our experiment has demonstrated that the above theoretical model is feasible from low temperature to normal temperature. The thin film sensor element provides the necessary temperature information for cryogenic wind tunnel design and hypersonic vehicle surface model design in real time

Zero retinal vein pulsation amplitude extrapolated model in non-invasive intracranial pressure estimation

Intracranial pressure (ICP) includes the brain, optic nerve, and spinal cord pressures; it influences blood flow to those structures. Pathological elevation in ICP results in structural damage through various mechanisms, which adversely affects outcomes in traumatic brain injury and stroke. Currently, invasive procedures which tap directly into the cerebrospinal fluid are required to measure this pressure. Recent fluidic engineering modelling analogous to the ocular vascular flow suggests that retinal venous pulse amplitudes are predictably influenced by downstream pressures, suggesting that ICP could be estimated by analysing this pulse signal. We used this modelling theory and our photoplethysmographic (PPG) retinal venous pulse amplitude measurement system to measure amplitudes in 30 subjects undergoing invasive ICP measurements by lumbar puncture (LP) or external ventricular drain (EVD). We estimated ICP from these amplitudes using this modelling and found it to be accurate with a mean absolute error of 3.0 mmHg and a slope of 1.00 (r = 0.91). Ninety-four percent of differences between the PPG and invasive method were between − 5.5 and + 4.0 mmHg, which compares favourably to comparisons between LP and EVD. This type of modelling may be useful for understanding retinal vessel pulsatile fluid dynamics and may provide a method for non-invasive ICP measurement.

Methods to assess tooth gingival thickness and diagnose gingival phenotypes: A systematic review.

Measurement of the periodontal soft tissue dimension is crucial for clinical decision-making and aesthetic prognosis. However, the effectiveness of different measuring methods remains unclear. This systematic review aimed to explore the diagnostic accuracy of two non-invasive methods (namely CBCT and ultrasound) for gingival thickness measurement at different tooth positions. A systematic search was performed using PubMed (including Medline), PubMed Central, OVID, Cochrane Library, LILACS and OpenGrey. Studies focusing on comparisons between CBCT, ultrasound and direct transgingival probing were included. The means, SDs and correlation coefficients with 95% confidence intervals were extracted and analyzed using Review Manager and R software. Twelve studies were selected. No significant difference was found between CBCT measurement and transgingival probing in the anterior and posterior dentition, and a moderate correlation was observed between these two methods (r=0.41). A weak correlation was found between ultrasound measurement and transgingival probing (r=0.32), and a slight but statistically significant difference was found when comparing ultrasonic devices and transgingival probing in the posterior area. CBCT can be considered a relatively reliable method for gingival thickness measurement in both the anterior and posterior areas compared with direct probing. Ultrasonic devices provide limited accuracy in the posterior area but are relatively comparable with direct clinical assessments in the anterior area. Measurement location may affect the diagnostic accuracy and repeatability of gingival thickness measurements. Appropriate method selection in different clinical scenarios is crucial to aesthetic outcome prediction and decision-making.

Increased skin autofluorescence of advanced glycation end-products (AGEs) in Tunisian hemodialysis patients with heart failure

Background: Cardiovascular disease (CVD) is the main reason for morbidity and mortality of patients in hemodialyis. Skin autofluorescence (SAF), a noninvasive measurement method, reflects tissue accumulation of advanced glycation end products (AGEs) that has been implicated in CVD as a strong marker. The aim of this study was to evaluate SAF profile in hemodialysis patients and to assess the association between SAF and heart failure. Methods: In a cross-sectional study, we included 60 hemodialysis (HD) patients who were subdivided in two groups: a HD group without heart failure (n=39) and a HD group with heart failure (n=21). Skin AGEs accumulation was measured by AGE Reader device and clinical data was obtained. Results: HD patients showed a SAF value at 2.90 (2.40-3.60). HD patients with diabetes mellitus have an increased SAF levels compared to HD patients without diabetes [3.20 (2.90-3.95) vs. 2.70 (2.30-3.30) AU, P = 0.021; respectively]. Furthermore, HD patients with heart failure showed a significant increased SAF levels compared to HD patients without heart failure [3.65 (2.90-4.12) vs. 2.60 (2.30-3.20) AU, P &lt;0.001; respectively]. SAF was associated with age, gender, and duration of dialysis. The ROC analysis indicated that SAF at 3.05 AU was optimal cut-off point for presence of heart failure (P &lt;0.001). Conclusion: SAF might be a rapid and helpful tool in clinical practice as a potential marker for evaluating and screening heart failure in HD patients non-invasively and might be used as predictor for clinicians. Keywords: skin autofluorescence; advanced glycation end products; hemodialysis; heart failure.

A Non-Invasive Measurement Method of Pipeline Flow Rate Based on Dual FBG Sensors

Combining fiber Bragg grating (FBG) sensors and finite element simulation analysis, an online monitoring method for non-invasive distributed flow velocity in pipelines has been proposed. A placement strategy has been proposed for the deployment of these FBG sensors to ensure effective sensing of strain. The cross-sensitivity problem of FBG sensors can be solved by differential FBG measurements. The principle of online monitoring of flow velocity based on the flow velocity function and finite element analysis is described and derived. Finite element analysis results show the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\varepsilon }_{1}- \boldsymbol {\varepsilon }_{2}$ </tex-math></inline-formula> at 45° of the elbow of the bend is quadratically proportional to the flow velocity. Meanwhile, the feasibility of the method is verified by experiments. The calibration results show a fitted correlation coefficient R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.9982 in the velocity range of 4.25-10.62m/s, fitted by least squares to the wavelength data. The repeatability error of the flow measurement of the proposed sensor is no more than 5.06%FS. Compared with the existing literature, the method proposed in this paper has a wider range of flow velocity measurement and applications, especially suitable for applications with strong electromagnetic interference capability and harsher environment, showing great potential for engineering applications, especially in the distributed detection of long-distance pipeline networks.

Neonatal Impedance Cardiography in Asphyxiated Piglets-A Feasibility Study.

ObjectivesImpedance cardiography (ICG) is a non-invasive method for continuous cardiac output measurement and has the potential to improve monitoring and treatment of sick neonates. PhysioFlow® is a signal-morphology ICG-system showing promising results in adults with low and high cardiac output, but no data from neonates or neonatal models exist. The aim of this study was to investigate PhysioFlow® feasibility in asphyxiated newborn piglets.MethodsFifteen piglets, under continuous arterial heart rate (HR) and blood pressure (BP) monitoring, were asphyxiated until asystole. Cardiopulmonary resuscitation was performed and the piglets monitored after return of spontaneous circulation (ROSC). Arterial lactate was measured at baseline, every 5 min throughout asphyxiation, at asystole, and at 10 min and later every 30 min after ROSC. PhysioFlow® measured cardiac stroke volume (SV) and HR, and calculated cardiac index (CI) (L/m2/min). Registrations with a signal quality < 75% were excluded, and registrations recorded for 30 min from start of asphyxia analyzed. Pearson correlations were calculated for CI; and HR, mean BP and blood lactate.ResultsThe piglets were asphyxiated for median (interquartile range) 30 (20–35) min and had a lactate at asystole of 15.0 (9.1–17.0) mmol/L. Out of a total of 20.991 registrations in all animals combined, there were 10.148 (48.3%) registrations with a signal quality ≥ 75%. Signal quality ≥ 75% varied in individual piglets from 7 to 82% of registrations. We analyzed 1.254 registrations recorded 30 min from initiation of asphyxia, i.e., in piglets with brief asphyxia times, this included cardiopulmonary resuscitation and post-ROSC observation. There was a positive correlation between CI and SVI (r = 0.90, p < 0.001), and between CI and HR (r = 0.446, p < 0.001). There was no correlation between CI, or mean BP or lactate (p = 0.98 and 0.51, respectively).ConclusionAbout half of ICG-registrations in asphyxiated piglets were of good quality. However, signal quality was highly variable between piglets. In total, there was a higher proportion of reliable ICG-registrations than reported from clinical delivery room studies using electrical velocimetry. Our data are physiologically plausible and supports further research evaluating PhysioFlow® for cardiac output monitoring in perinatal asphyxia. In particular, factors influencing inter-individual variations in signal quality should be explored.

Development of non-invasive blood glucose regression based on near-infrared spectroscopy combined with a deep-learning method

Extracting micro-scale spectral features from dynamic blood glucose concentrations is extremely difficult when using non-invasive measurement methods. This work proposes a new machine-learning method based on near-infrared spectroscopy, a deep belief network (DBN), and a support vector machine to improve prediction accuracy. First, the standard oral glucose tolerance test was used to collect near-infrared spectroscopy and actual blood glucose concentration values for specific wavelengths (1200, 1300, 1350, 1450, 1600, 1610, and 1650 nm); the blood glucose concentrations were within a clinical range of 70 ∼ 220 mg dl−1. Second, based on the DBN model, high-dimensional deep features of the non-invasive blood glucose spectrum were extracted. These were used to establish a support vector regression (SVR) model and to quantitatively analyze the influence of the spectral sample size and corresponding feature dimensions (i.e. DBN structure) on prediction accuracy. Finally, based on data from six volunteers, a comparative analysis of the SVR model’s prediction accuracy was performed both before and after using high-dimensional deep features. For volunteer 1, when the DBN-based high-dimensional deep features were used, the root mean square error of the SVR model was reduced by 71.67%, and the correlation coefficient (R 2) and the P value of the Clark grid analysis (P) were increased by 13.99% and 6.28%, respectively. Moreover, we had similar results when the proposed method was carried out on the data of other volunteers. The results show that the presented algorithm can play an important role in dynamic non-invasive blood glucose concentration prediction and can effectively improve the accuracy of the SVR model. Further, by applying the algorithm to six independent sets of data, this research also illustrates the high-precision regression and generalization capabilities of the DBN-SVR algorithm.

A Non-Invasive Heart Rate Measurement Method Is Improved by Placing the Electrodes on the Ventral Side Rather Than the Dorsal in Loggerhead Turtles.

Heart rate measurement is an essential method for evaluating the physiological status of air-breathing diving animals. However, owing to technical difficulties, many marine animals require an invasive approach to record an electrocardiogram (ECG) in water, limiting the application of this approach in a wide range of marine animals. Recently, a non-invasive system was reported to measure the ECG of hard-shelled sea turtles by pasting the electrodes on the dorsal side of the shell, although the ECG obtained from the moving turtle contains noise produced by muscle contraction. Here, we report that clear ECGs can be obtained by placing the electrodes on the ventral side rather than the dorsal side in loggerhead sea turtles. Using our method, clearer ECG signals were obtained with less electrical noise, even when turtles are swimming. According to the anatomical features, the electrode position on the ventral side is closer to the heart than the dorsal side, minimizing the effects of noise generated by the skeletal muscle. This new biologging technique will elucidate the functioning of the circulatory system of sea turtles during swimming and their adaptabilities to marine environments. This article is part of the theme issue “Methods and Applications in Physio-logging.”