Non-invasive Measurement Method Research Articles

ACNN-BiLSTM: A Deep Learning Approach for Continuous Noninvasive Blood Pressure Measurement Using Multi-Wavelength PPG Fusion.

As an essential physiological indicator within the human body, noninvasive continuous blood pressure (BP) measurement is critical in the prevention and treatment of cardiovascular disease. However, traditional methods of blood pressure prediction using a single-wavelength Photoplethysmographic (PPG) have bottlenecks in further improving BP prediction accuracy, which limits their development in clinical application and dissemination. To this end, this study proposed a method to fuse a four-wavelength PPG and a BP prediction model based on the attention mechanism of a convolutional neural network and bidirectional long- and short-term memory (ACNN-BiLSTM). The effectiveness of a multi-wavelength PPG fusion method for blood pressure prediction was evaluated by processing PPG signals from 162 volunteers. The study compared the performance of the PPG signals with different individual wavelengths and using a multi-wavelength PPG fusion method in blood pressure prediction, assessed using mean absolute error (MAE), root mean squared error (RMSE) and AAMI-related criteria. The experimental results showed that the ACNN-BiLSTM model achieved a better MAE ± RMSE for a systolic BP and diastolic BP of 1.67 ± 5.28 and 1.15 ± 2.53 mmHg, respectively, when using the multi-wavelength PPG fusion method. As a result, the ACNN-BiLSTM blood pressure model based on multi-wavelength PPG fusion could be considered a promising method for noninvasive continuous BP measurement.

Evaluation of the oscillometric method for noninvasive blood pressure measurement during cuff deflation and cuff inflation with reference to intra-arterial blood pressure.

There is little quantitative clinical data available to support blood pressure measurement accuracy during cuff inflation. In this study of 35 male and 5 female lightly anaesthetized subjects aged 64.1 ± 9.6 years, we evaluate and compare the performance of both the oscillometric ratio and gradient methods during cuff deflation and cuff inflation with reference to intra-arterial measurements. We show that the oscillometric waveform envelopes (OWE), which are key to both methods, exhibit significant variability in both shape and smoothness leading to at least 15% error in the determination of mean pressure (MP). We confirm the observation from our previous studies that K1 Korotkoff sounds underestimate systolic blood pressure (SBP) and note that this underestimation is increased during cuff inflation. The estimation of diastolic blood pressure (DBP) is generally accurate for both the ratio and the gradient method, with the latter showing a significant increase during inflation. Since the gradient method estimates SBP and DBP from points of maximum gradient on each OWE recorded, it may offer significant benefits over the ratio method. However, we have shown that the ratio method can be optimized for any data set to achieve either a minimum mean error (ME) of close to 0 mmHg or minimum root mean square error (RMSE) with standard deviation (SD) of <5.0 mmHg. We conclude that whilst cuff inflation may offer some advantages, these are neither significant nor substantial, leaving as the only benefit, the potential for more rapid measurement and less patient discomfort.

Development of long-range conductivity mechanisms in glass-like carbon

The conductivity mechanisms in glass-like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700–750 °C) utilising microwave dielectric spectroscopy techniques. Broadband measurements using an open-ended coaxial probe (BCP) are used to investigate the complex permittivity and conductivity as a function of frequency and show the development of long range conduction and sp2 carbon chain formation. Fixed frequency resonance measurements using microwave cavity perturbation (MCP) methods are shown as a way of measuring this transition and change in Q-factor without requiring contacts and therefore acting as a effective method for non-destructive and non-invasive measurements. Using these methods we show a clear change in the AC conductivity of glass-like carbon at a pyrolysis temperature of ∼730 °C and demonstrate how microwave cavity perturbation (MCP) can be used as a non-contact method of dielectric spectroscopy for determining the transition of conductivity mechanisms in glass-like carbon from short to long range and therefore as a method for non-destructive material quality control. We demonstrate that both BCP and MCP dielectric spectroscopy methods are effective at clearly detecting changes in the structure and conductivity mechanisms of glass-like carbon over a small pyrolysis temperature range.

Measurement the 3D temperature distribution in the combustion zone using acoustic tomography and nolinear wavefont tracing

A non-invasive temperature measurement method in three dimensions is proposed to reconstruct the three-dimensional temperature. It relies on the use of nonlinear acoustic travel-time tomography, which incorporates acoustic path tracing, Gaussian kernel function, and modified Tikhonov regularization. Sound signals can be distorted due to large average temperature gradients and oscillatory release of heat in the combustion region. The effective acoustic signal is extracted based on spectral subtraction to evaluate the sound propagation time under distorted signals. The analysis of experimental errors indicates that the proposed acoustic pyrometry method has an average relative error of less than 15% compared to the time-averaged temperature measured by thermocouples. This result verifies the efficacy of the method when it comes to accurately reconstructing the temperature field in the combustion area. The reduction in error is attributed to the consideration of acoustic ray tracing within the proposed method.

The Relationship between Lumbar Puncture Opening Pressure and Retinal Nerve Fiber Layer Thickness in the Diagnosis of Idiopathic Intracranial Hypertension: Is a Lumbar Puncture Always Necessary?

Idiopathic intracranial hypertension (IIH), is characterized by elevated intracranial pressure (ICP) without an identified cause. Today, lumbar puncture (LP) is the most common method used for diagnosis by measuring cerebrospinal fluid (CSF) pressure to reflect intracranial pressure. This invasive examination has significant disadvantages, such as complications and negative experiences for patients. Therefore, noninvasive methods for ICP measurement are desired. Optical coherence tomography (OCT) is widely used for the diagnosis and follow-up of IIH patients as it reflects papilledema. The aim of this study is to investigate the relationship between CSF pressure and OCT parameters and the ability of OCT in the diagnostic approach. In our study, patients who were followed up with a diagnosis of IIH with complete neuro-ophthalmological examinations, including visual acuity (VA), visual field, and OCT imaging within 24 hours before lumbar puncture, were retrospectively evaluated. CSF pressure, visual acuity LogMAR, mean deviation of visual fields, retinal nerve fiber layer (RNFL) thickness measured by OCT, and treatment protocols were obtained from our hospital data system. A total of 42 eyes of 21 patients were enrolled in the study. A statistically significant positive and moderate correlation was found between CSF pressure values and average RNFL thickness (r=0.507; P=0.001). The same relationship was demonstrated in all 4 quadrants: inferior, superior, nasal, and temporal. Increased peripapillary RNFL thickness in optic nerve head OCT may be correlated with increased ICP in IIH patients. A larger number of patients are needed to better understand the correlation between OCT parameters and CSF pressure in patients with IIH.

Comparative Analysis of Non-Invasive Measurement Methods for Optimizing Architectural Documentation

Architectural documentation not only plays a critical role in the conservation of historical structures, but also enables their detailed comprehension of the structure. This study aims to assess the most effective methods for drawing and modeling architectural structures and present their advantages and disadvantages. Measurements play a significant role in this context, and today's technology offers the potential to accelerate this process and enhance accuracy. However, the application of these technologies can impose additional burdens such as elevated expenses, the requisite for specialized personnel, and the management of substantial data volumes. Therefore, determining the appropriate measurement method in line with the quality of architectural documentation is essential. For this study, the Mosque of Kurşunlu Complex in Eskişehir was selected for its historical and topographical attributes which enabled all methods to be examined. The data produced via terrestrial laser scanning, aerial photogrammetry and terrestrial photogrammetry methods were examined in terms of the production of drawings and models for different analysis methods such as structure, daylight and building acoustics, as well as survey drawings required for the architectural documentation processes of the building. The study concluded that no single method could produce holistic data on its own, and the best results for comprehensive documentation were achieved by integrating terrestrial laser scanning and aerial photogrammetry. Furthermore, for products that do not require comprehensive data, photogrammetric methods were more efficient.

Innovative non-invasive ultrasound method for whisky cask liquid level measurement

Regular measurement and inspection of whisky casks are crucial for ensuring quality and effective inventory management. This process helps detect issues such as leaks, damage, and contamination that can harm the whisky’s condition. Additionally, monitoring the whisky level provides valuable insights into maturation progress, evaporation rates, and production planning to account for expected losses. Currently, the industry relies on dipsticks and pressure sensors to measure liquid levels in casks. Dipsticks require moving casks from high shelves, risking human safety, the utilisation of extensive resources and necessitating cask opening, which has inherent issues. Pressure sensors, installed inside casks, are sensitive to temperature, limiting their accuracy and suitability for warehouse testing. This paper presents a new non-invasive method using ultrasound to measure liquid levels in wooden casks. An external ultrasonic probe glides along the surface of the cask. By leveraging the distinct ultrasonic acoustic properties in the liquid and the air, the sensor can detect the upper boundary of the liquid, thereby indicating the whisky level. Since this new method only needs to access a small portion of the cask to measure the level, it enables distilleries to accurately monitor cask contents on-site, reducing the costs and risks associated with moving casks. The paper also includes quantitative data on ultrasonic properties such as moisture, velocity, and signal attenuation for various cask samples. The prototype system successfully demonstrated this approach on a retired Ex-Bourbon whisky cask, providing precise liquid level measurements on different surfaces and storage orientations without the need for cask opening. It achieved centimetre-level accuracy compared to dipstick reference readings.

Non-invasive methods for heart rate measurement in fish based on photoplethysmography.

Heart rate is a crucial physiological indicator for fish, but current measurement methods are often invasive or require delicate manipulation. In this study, we introduced two non-invasive and easy-to-operate methods based on photoplethysmography, namely reflectance-type photoplethysmography (PPG) and remote photoplethysmography (rPPG), which we applied to the large yellow croaker (Larimichthys crocea). PPG showed perfect synchronization with electrocardiogram (ECG), with a Pearson's correlation coefficient of 0.99999. For rPPG, the results showed good agreement with ECG. Under active provision of green light, the Pearson's correlation coefficient was 0.966, surpassing the value of 0.947 under natural light. Additionally, the root mean square error was 0.810, which was lower than the value of 1.30 under natural light, indicating not only that the rPPG method had relatively high accuracy but also that green light may have the potential to further improve its accuracy.

Features extraction from cardiac-related signals: comparison among different measurement methods

Heart Rate (HR), Heart Rate Variability (HRV), and cardiac time intervals are clinically relevant parameters, which can be assessed from the analysis of electrocardiogram (ECG). Some aspects of cardiac activity can be investigated also by means of different noninvasive and non-intrusive measurement methods, such as phonocardiograph (PCG), photoplethysmograph (PPG), and vibrocardiograph (VCG). However, the standard processing algorithms (i.e., Pan & Tompkins) do not allow to fully characterize waveforms different from ECG. In the past, some of the authors have already demonstrated the efficiency of a novel processing procedure for the precise HR measurement from the above-mentioned signals. In the present work, data processing procedure has been improved and deeply extended to assess HRV parameters and time intervals from all the signals acquired on an extended experimental campaign, involving 26 subjects, on whom ECG, PPG, PCG, and VCG signals were simultaneously measured. Results prove that this approach can overcome the drawbacks of standard algorithms and can be widely applied to signals of different nature to derive HR, HRV, and time intervals. As regards HR measurement, PPG proved to be the most accurate measurement method (±1.2 bpm), followed by VCG (±1.6 bpm) and PCG (±2.5 bpm). For HRV analysis in the time domain, the use of the proposed methodology allows to obtain clinically relevant parameters statistically comparable to the ECG ones. Finally, the measurement of QT interval by applying personal calibration lines allows to obtain results comparable to the gold standard technique, i.e., ECG (maximum percentage deviation reduced from 10.9% up to <4.3% in VCG).

Pore structure dynamic evolution of coal during hydraulic intrusion based on NMR

Low-field nuclear magnetic resonance (LF-NMR) technology is a non-invasive measurement method, that provides a fast, direct, and nondestructive tool for characterizing complex pore structure. To reveal the evolution law of pore structure and stress sensitivity during hydraulic intrusion, this paper adopts LF-NMR monitoring and in-situ hydraulic intrusion technology to carry out the hydraulic intrusion test on both pre-drilled and un-drilled coal. The quantitatively characterizes the variation patterns of pore structure, compressibility, and other parameters, revealing the dynamic mechanism of pore structure evolution Three dynamic evolution laws of pores were obtained through experimental data analysis. The mechanism of dynamic evolution of pore structure was determined from the perspective of pore compressibility and effective stress. Based on the measurement results, LF-NMR is an efficient non-destructive method for quantifying pore size distributions of the coal.

Quantitative analysis of age-related changes in vascular structure, oxygen saturation, and epidermal melanin structure using photoacoustic methods.

Vascular structure, blood oxygen saturation, and melanin status of the epidermis are chromophore factors related to light absorption. Therefore, they are likely to be related to skin appearance. Thus, it is important to measure these internal skin features and understand their characteristics. Thus, we aimed to analyze the individual differences and aging changes in the skin by measuring the internal skin characteristics, such as vascular structure, oxygen saturation, and the 3D distribution of melanin in the epidermis, using a noninvasive photoacoustic (PA) measurement method. A PA measurement device was used as a noninvasive measurement method. Eighty Japanese women aged between 20 and 60 years were enrolled. The target area was the buccal region of the face. The blood vessel structure showed a decrease in fine vessels with age, with a stronger tendency observed in the dermis layer, and the volume of blood vessels was larger in the dermis layer than in the dermal-subcutaneous fat boundary layer. Oxygen saturation showed a similar decreasing trend with age in all depths examined. Melanin condition as the torus-like pattern structure tended to increase with age. PA measurements revealed the characteristics of several chromophores, providing a new skin aging mechanism.

Experimental studies of a soft industrial exoskeleton in work-related activity for the evaluation of its operational efficiency

For conducting the experiment under laboratory conditions, a dedicated workplace was designed to simulate the activity of lifting / lowering a 20 kg load to a height of 0.7 m in the “Squat” and “Stoop” styles. To implement this study, the following methods were employed: “motion capture” to assess the mechanics of movements in the lumbar spine; a non-invasive method for measurement of the key biological indicators as a comprehensive assessment of the state of the cardiorespiratory system; electromyography (EMG) as the main method for assessing the bioelectrical activity of muscles; interviewing volunteers (on a 10-point scale) as a method of subjective assessment of their physical condition and performance. A study conducted as part of the work meant to determine the effectiveness and safety of using a soft industrial exoskeleton during work-related activity, including the elimination of the harm from stereotypic work movements, showed a decrease in the activity of the measured muscles when using a soft industrial exoskeleton, which also indicates a decrease in human fatigue that increases the effectiveness of its operation.

Non-Invasive Blood Pressure Tracking of Spontaneous Hypertension Rats Using an Electronic Nose.

Traditional noninvasive blood pressure measurement methods in experimental animals are time consuming and difficult to operate, particularly for large numbers of animals. In this study, the possibility of sensing fecal odor to estimate the blood pressure status of spontaneous hypertension rats (SHRs) was explored with the aim of establishing a new method for non-invasive monitoring of blood pressure. The body weight and blood pressure of SHRs kept increasing with growth, and the odor information monitored using an E-nose varied with the blood pressure status, particularly for sensors S6 and S7. The fecal information was analyzed using principal component analysis, canonical discriminant analysis and multilayer perception neural networks (MLP) to discriminate SHRs from normal ones, with a 100% correct classification rate. For better prediction of blood pressure, the model built using multiple linear regression analysis, partial least squares regression analysis and multilayer perceptron neural network analysis were used, with coefficients of determination (R2) ranging from 0.8036 to 0.9926. Moreover, the best prediction model for blood pressure was established using MLP analysis with an R2&not; higher than 0.91. Thus, changes in blood pressure levels can be tracked non-invasively, and normotension can be distinguished from hypertension or even at different hypertension levels based on the odor information of rat feces, providing a foundation for non-invasive health monitoring. This work might provide potential instructions for functional food research aimed at lowering blood pressure.

Real-time temperature monitoring technology for dynamic combustion processes using dual-probe femtosecond CARS

We propose a fast responsive and non-invasive optical temperature measurement method which can be used to monitor the temperature of air-fed flames in real time. This method is based on femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (fs-CARS). Two probe pulses with different wavelengths are employed in the CARS system to generate two CARS signals, and the intensity ratio of the two CARS signals has a definite numerical relationship with temperature and therefore can be used to rapidly measure the flame temperature. The temperature of methane/air swirl flames was monitored by the dual-probe fs-CARS thermometry with a sampling rate of 100 Hz. For the steady swirl flame, the measured average temperature in the inner recirculation zone is 1551 K with a standard deviation of 3.7%. While, at a higher methane/air equivalent ratio of 0.74, the flame cannot remain steady, and the temperature frequently jumps from around 1700 K to 2000 K, causing the vortex to expand and break. A significant advantage of the dual-probe fs-CARS thermometry is that the temperature of the flame can be obtained immediately during the measurement without any post-processing. Therefore, this method is a potential candidate for accurately monitoring the real-time temperature of turbulent combustion.

Cuff‐less blood pressure estimation using hetero‐core optical fibers

AbstractIn this study, we proposed a cuff‐less blood pressure measurement using a medical tape sensor with an embedded hetero‐core optical fiber. The tape sensor pasted on the skin can directly detect pulse wave signals with a simple measuring device. Pulse transit time (PTT) was obtained from the time difference between the two pulse waveforms at the neck and foot. Systolic blood pressure (SBP) was estimated from PTT and the regression equation. The result shows that the maximum prediction error was 3.8 mmHg in five healthy young subjects. The SBP data were evaluated using a Bland‐Altman method to assess the agreement of SBP data estimated by the proposed method with those measured by the cuff‐based electronic sphygmomanometer. The mean ± 1.96 standard deviation of the estimated SBP against the reference was −1.3 ± 5.1 mmHg. The results show that the proposed noninvasive blood pressure measurement method can measure blood pressure, and its accuracy is comparable to that of the cuff‐based electronic sphygmomanometer.

Comparison of analog and digitally evaluated volume of the female breast in reconstructive breast surgery. Validation of a noninvasive measurement method with 3D camera1.

Reconstructive surgery is established as a standard treatment option after mastectomy due to cancer. It is crucial to patients to achieve a natural and symmetric looking breast through reconstruction. Anthropometric measurements are used to assess the objective symmetry of the breast, which are prone to errors and difficult to reproduce. The aim of this work is to validate breast volumetry using three-dimensional surface imaging. We compared preoperatively analog and digitally evaluated volume of the breast with our gold standard, direct water displacement measurement of the mastectomy specimen. We examined 34 breast specimens in total. Each measurement method (Breast Sculptor, VAM, Breast-V) for breast volume/mass determination demonstrates acceptable agreement ranges when compared with resected volumes and masses. The strongest volumetry instrument is Breast Sculptor (digital), the weakest is Breast-V (analog). 3D surface imaging is a quick, effective, and convenient method to evaluate breast shape and volume. The accuracy, reproducibility, and reliability of 3D surface imaging were comparable with MRI in our study.This takes us a step closer to the long-term goal of establishing robust instruments to plan breast reconstructive surgery, achieve better surgical results, and contribute to quality assurance in breast surgery.

A joint evaluation method of dynamic spectrum extraction methods for non-invasive blood component measurement based on stability coefficient, data point adoption rate, and smoothness of the spectrum

Background and ObjectiveDynamic spectrum (DS) theory is a new non-invasive detection method of human blood components that can theoretically eliminate individual differences in static tissues and the influence of other measurement conditions to achieve blood component analysis with high precision. In order to obtain a high signal-to-noise ratio dynamic spectrum, researchers have proposed various dynamic spectrum extraction methods. MethodsIn this article, we propose three indexes: stability coefficient (SC), data point adoption rate (DAR), and smoothness of spectrum (SS). These solve the difficulty in evaluating different dynamic spectrum extraction methods without establishing mathematical models. ResultsIn this study, DS is extracted using different dynamic spectrum extraction methods from the experimental data of 677 volunteers. Then three indexes, SC, DAR, and SS, are calculated. The trends in the scatter plot of the relationship between the three indexes and modeling results of hemoglobin, red blood cell count, and white blood cell count and the related coefficients demonstrate that SC, DAR, and SS are feasible and effective for evaluation. The results show that the root mean square extraction performs best, while the peak-to-peak value and the fast Fourier transform extraction are the worst. ConclusionsThis study proposes feasible and effective indexes for evaluating dynamic spectrum extraction methods, providing a possibility for further research on high-precision dynamic spectrum extraction methods.

A Non-Invasive Technique for Long-Term Monitoring of Gastroesophageal Reflux—A Pilot Study

Many people suffer from gastric or gastroesophageal reflux disorder (GERD) due to a malfunction of the cardia, the valve between the esophagus and the stomach. GERD is a syndrome caused by the ascent of gastric juices and bile from the stomach. This article proposes a non-invasive impedance measurement method and demonstrates the correlation between GERD and impedance variation between appropriately chosen points on the patient’s chest. This method is presented as an alternative to the most widely accepted diagnostic techniques for reflux, such as pH-metry, pH-impedance measurement, and esophageal manometry, which are invasive because they use a probe that is inserted through a nostril and reaches down to the esophagus.

P045 Noxturnal cRIP: A Comparative Analysis of Sensors for the Identification of Respiratory Events in Polysomnography

Abstract Introduction AASM recommends the use of nasal pressure (NP), oronasal thermal flow (TF), and respiratory inductance plethysmography (RIP) for detecting and characterising respiratory events in polysomnography. The use of both NP and TF sensors is reported to be more accurate in respiratory event identification than either alone. However, these sensors can be unreliable if dislodged and cause discomfort. Noxturnal calibrated RIP flow (cRIPflow), derived from RIP, may provide a non-invasive alternative method for flow measurement in identification of respiratory events. Method Respiratory scoring was performed manually by a single experienced scorer on 10 diagnostic sleep studies under AASM standards. Scoring was repeated using three different measurements for each study: cRIPflow only, Thermistor (Th) only and both Th+NP (AASM recommendation). Apnoea hypopnoea index (AHI), central apnoea index (CAI), obstructive apnoea index (OAI), mixed apnoea index (MAI) and hypopnoea index (HI) were calculated and paired t-test analysis utilised for comparison between measurements. Results No statistical differences were identified in comparison of cRIPflow with Th or Th+NP in respiratory event identification: CAI (cRIPflow 3.2/hr±7.1, Th 3.9/hr±8.9, Th+NP 3.1/hr±7.5), OAI (cRIPflow 6.1/hr±6.8, Th 5.3/hr±8.2, Th+NP 6.7/hr±8.9), MAI (cRIPflow 5.2/hr±9.7, Th 4.3/hr±8.7, Th+NP 4.7/hr±9.2), or HI (cRIPflow 12.5/hr±13.9, Th 11.1/hr±10.5, Th+NP 10.4/hr±10.7). There was a statistical difference for AHI (cRIPflow 26.9/hr±26.6, Th 24.5/hr±26.4, Th+NP 25.0/hr±26.5). Discussion This study suggests cRIPflow may provide an alternative measurement in the detection and characterisation of respiratory events, however further analysis with larger sample size would provide more insight into sensitivity and specificity of this method.

Assessment of venous pressure by compression sonography of the internal jugular vein during 3days of bed rest.

Compression sonography has been proposed as a method for non-invasive measurement of venous pressures during spaceflight, but initial reports of venous pressure measured by compression ultrasound conflict with prior reports of invasively measured central venous pressure (CVP). The aim of this study is to determine the agreement of compression sonography of the internal jugular vein (IJVP) with invasive measures of CVP over a range of pressures relevant to microgravity exposure. Ten healthy volunteers (18-55years, five female) completed two 3-day sessions of supine bed rest to simulate microgravity. IJVP and CVP were measured in the seated position, and in the supine position throughout 3days of bed rest. The range of CVP recorded was in line with previous reports of CVP during changes in posture on Earth and in microgravity. The correlation between IJVP and CVP was poor when measured during spontaneous breathing (r=0.29; R2 =0.09; P=0.0002; standard error of the estimate (SEE)=3.0mmHg) or end-expiration CVP (CVPEE ; r=0.19; R2 =0.04; P=0.121; SEE=3.0mmHg). There was a modest correlation between the change in CVP and the change in IJVP for both spontaneous ΔCVP (r=0.49; R2 =0.24; P<0.0001) and ΔCVPEE (r=0.58; R2 =0.34; P<0.0001). Bland-Altman analysis of IJVP revealed a large positive bias compared to spontaneous breathing CVP (3.6mmHg; SD=4.0; CV=85%; P<0.0001) and CVPEE (3.6mmHg; SD=4.2; CV=84%; P<0.0001). Assessment of absolute IJVP via compression sonography correlated poorly with direct measurements of CVP by invasive catheterization over a range of venous pressures that are physiologically relevant to spaceflight. However, compression sonography showed modest utility for tracking changes in venous pressure over time. NEW FINDINGS: What is the central question of this study? Compression sonography has been proposed as a novel method for non-invasive measurement of venous pressures during spaceflight. However, the accuracy has not yet been confirmed in the range of CVP experienced by astronauts during spaceflight. What is the main finding and its importance? Our data show that compression sonography of the internal jugular vein correlates poorly with direct measurement of central venous pressures in a range that is physiologically relevant to spaceflight. However, compression sonography showed modest utility for tracking changes in venous pressure over time.