Non-invasive Pressure Measurement Research Articles

COMPARISON OF BLOOD PRESSURE PARAMETERS WITH LEFT VENTRICULAR MASS IN YOUNGER MEN WITH GRADE 1 HYPERTENSION

Objective: Non-invasive measurement of central aortic systolic pressure (CASP) has been claimed to confer advantage over conventional clinic blood pressure (BP) in predicting cardiovascular risk, particularly in younger patients where amplification is variable. This study aimed to compare relationships between clinic BP, CASP and ambulatory BP (ABPM) with left ventricular (LV) mass in younger men with grade 1 hypertension and low cardiovascular risk. Design and method: 155 men aged < 55 years with grade 1 hypertension confirmed by ABPM, underwent a cardiac magnetic resonance imaging (cMRI) scan. BP was assessed by clinic and 24-hour ABPM. CASP was evaluated using a high fidelity tonometer (BProâ) to capture radial artery waveforms calibrated to clinic systolic and diastolic or mean and diastolic (fixed form factor) and processed using a n-point moving average. LV mass indexed to body surface area (LVMI), was assessed by manual segmentation of the LV image stack acquired using a 1.5T cMRI scanner. Linear regression and receiver operator curve (ROC) analysis was used to evaluate the relationship between LVMI and BP measurement mode and whether relationships between CASP and LVMI were influenced by calibration mode. Results: In 155 men recruited from the general community (mean age 45 years) with grade 1 hypertension and low cardiovascular risk (10-year QRISKâ 5.4%), increasing BP was positively associated with LVMI. Relationships with LVMI was similar between BP measurement modes (clinic systolic BP r = 0.27, p < 0.001, 24-hour ABPM systolic BP r = 0.28 p < 0.001). The relationship of LVMI with CASP differed little for pressure waves calibrated using systolic and diastolic BP (r = 0.25, p < 0.001) or mean and diastolic BP at a form factor of 0.33 (r = 0.30, p < 0.001). ROC analysis for high LV mass detection (highest 20%), showed similar predictive value between BP modes. Conclusions: Carefully measured clinic BP confirmed by ABPM, is as good at predicting LVMI as 24-hour ABPM or CASP, irrespective of the calibration mode in younger men with grade 1 hypertension where amplification is variable. Furthermore recalibration of radial waveforms to mean and diastolic BP at a commonly used form factor (0.33) does not significantly improve this relationship.

Noninvasive Assessment of Neuromechanical Coupling and Mechanical Efficiency of Parasternal Intercostal Muscle during Inspiratory Threshold Loading.

This study aims to investigate noninvasive indices of neuromechanical coupling (NMC) and mechanical efficiency (MEff) of parasternal intercostal muscles. Gold standard assessment of diaphragm NMC requires using invasive techniques, limiting the utility of this procedure. Noninvasive NMC indices of parasternal intercostal muscles can be calculated using surface mechanomyography (sMMGpara) and electromyography (sEMGpara). However, the use of sMMGpara as an inspiratory muscle mechanical output measure, and the relationships between sMMGpara, sEMGpara, and simultaneous invasive and noninvasive pressure measurements have not previously been evaluated. sEMGpara, sMMGpara, and both invasive and noninvasive measurements of pressures were recorded in twelve healthy subjects during an inspiratory loading protocol. The ratios of sMMGpara to sEMGpara, which provided muscle-specific noninvasive NMC indices of parasternal intercostal muscles, showed nonsignificant changes with increasing load, since the relationships between sMMGpara and sEMGpara were linear (R2 = 0.85 (0.75–0.9)). The ratios of mouth pressure (Pmo) to sEMGpara and sMMGpara were also proposed as noninvasive indices of parasternal intercostal muscle NMC and MEff, respectively. These indices, similar to the analogous indices calculated using invasive transdiaphragmatic and esophageal pressures, showed nonsignificant changes during threshold loading, since the relationships between Pmo and both sEMGpara (R2 = 0.84 (0.77–0.93)) and sMMGpara (R2 = 0.89 (0.85–0.91)) were linear. The proposed noninvasive NMC and MEff indices of parasternal intercostal muscles may be of potential clinical value, particularly for the regular assessment of patients with disordered respiratory mechanics using noninvasive wearable and wireless devices.

Pen type compression device and vein extraction method for non-invasive venous pressure measurement

Pen type compression device and vein extraction method for non-invasive venous pressure measurement

Non-invasive measurement of leaf water content and pressure\u2013volume curves using terahertz radiation

In this paper we describe a non-invasive method of measuring leaf water content using THz radiation and combine this with psychrometry for determination of leaf pressure–volume relationships. In contrast to prior investigations using THz radiation to measure plant water status, the reported method exploits the differential absorption characteristic of THz radiation at multiple frequencies within plant leaves to determine absolute water content in real-time. By combining the THz system with a psychrometer, pressure–volume curves were generated in a completely automated fashion for the determination of leaf tissue water relations parameters including water potential at turgor loss, osmotic potential at full turgor and the relative water content at the turgor loss point. This novel methodology provides for repeated, non-destructive measurement of leaf water content and greatly increased efficiency in generation of leaf PV curves by reducing user handling time.

Noninvasive estimation of aortic hemodynamics and cardiac contractility using machine learning

Cardiac and aortic characteristics are crucial for cardiovascular disease detection. However, noninvasive estimation of aortic hemodynamics and cardiac contractility is still challenging. This paper investigated the potential of estimating aortic systolic pressure (aSBP), cardiac output (CO), and end-systolic elastance (Ees) from cuff-pressure and pulse wave velocity (PWV) using regression analysis. The importance of incorporating ejection fraction (EF) as additional input for estimating Ees was also assessed. The models, including Random Forest, Support Vector Regressor, Ridge, Gradient Boosting, were trained/validated using synthetic data (n = 4,018) from an in-silico model. When cuff-pressure and PWV were used as inputs, the normalized-RMSEs/correlations for aSBP, CO, and Ees (best-performing models) were 3.36 ± 0.74%/0.99, 7.60 ± 0.68%/0.96, and 16.96 ± 0.64%/0.37, respectively. Using EF as additional input for estimating Ees significantly improved the predictions (7.00 ± 0.78%/0.92). Results showed that the use of noninvasive pressure measurements allows estimating aSBP and CO with acceptable accuracy. In contrast, Ees cannot be predicted from pressure signals alone. Addition of the EF information greatly improves the estimated Ees. Accuracy of the model-derived aSBP compared to in-vivo aSBP (n = 783) was very satisfactory (5.26 ± 2.30%/0.97). Future in-vivo evaluation of CO and Ees estimations remains to be conducted. This novel methodology has potential to improve the noninvasive monitoring of aortic hemodynamics and cardiac contractility.

Feasibility of Non-invasive Pulse Pressure Measurement Using the Phased-Tracking Method

Phased tracking (PT) is a high-precision ultrasonic technology that enables measurements of pulse pressure (PP). The aim of this study was to verify the accuracy of estimated PP using PT. Estimated PPs were compared with measured PPs in three sheep fetuses that were connected to an artificial placenta system. Similarly, estimated and measured PPs of 30 human neonates were compared. PP was calculated using the Water–Hammer equation (PP = ρ × PWV (pulse wave velocity) × ΔU). PWV was estimated by measuring the transit times of pulse waves at two sites along the aorta using the PT method, and ΔU was obtained by subtracting end-diastolic velocity from peak systolic velocity. The correlation between the estimated and measured PPs of the sheep fetuses was strong (r = 0.95, p ˂ 0.01), as was the case with the human neonates (r = 0.88, p ˂ 0.05). It can be concluded from the results of this study that PT may be a non-invasive alternative method used to predict PP.

Peritoneal Dialysis for Acute Kidney Injury Treatment in the United States: Brought to You by the COVID-19 Pandemic.

The coronavirus disease 2019 (COVID-19) pandemic has created unprecedented strain on health care resources in the United States. Initial reports of AKI rates from Wuhan, China ranged between 3% and 9%, although rates as high as 15% have been reported (1,2). For AKI requiring RRT, intermittent hemodialysis (HD) and continuous RRT (CRRT) have been mainstays of therapy in the United States. However, shortages in supplies, staffing, and available equipment among critically ill patients with COVID-19, particularly in the New York City area, have demanded alternative strategies such as acute peritoneal dialysis treatment for AKI (AKI-PD) that are being implemented. Here, we will review the rationale for the use of AKI-PD and describe potential advantages, criteria for patient selection, and practical considerations on the basis of initial experiences to consider when prescribing and delivering peritoneal dialysis (PD). PD was routine for AKI treatment worldwide well into the 1980s. However, by the 1990s with the development of the central venous catheter for HD and the advent of CRRT, PD became rarely used in higher-resource countries to treat adult patients with AKI (3). The utility and efficacy of PD to treat patients with AKI were re-examined after the publication of a series of articles from Brazil, including a randomized trial, demonstrating that PD provided acceptable care, was not inferior to daily HD in treating acutely ill patients with AKI in terms of patient mortality, and was associated with a shorter duration of AKI and need for RRT (4,5). These findings were confirmed in a randomized trial from Saudi Arabia comparing PD with hemodiafiltration (6). AKI-PD expanded dramatically in lower-resource countries with the advent of the Saving Young Lives Program in 2012, which promoted the use of PD because of minimal infrastructural requirements, including a lack of need for water …

Covert sleep-related biological processes are revealed by probabilistic analysis in Drosophila

Sleep pressure and sleep depth are key regulators of wake and sleep. Current methods of measuring these parameters in Drosophila melanogaster have low temporal resolution and/or require disrupting sleep. Here we report analysis tools for high-resolution, noninvasive measurement of sleep pressure and depth from movement data. Probability of initiating activity, P(Wake), measures sleep depth while probability of ceasing activity, P(Doze), measures sleep pressure. In vivo and computational analyses show that P(Wake) and P(Doze) are largely independent and control the amount of total sleep. We also develop a Hidden Markov Model that allows visualization of distinct sleep/wake substates. These hidden states have a predictable relationship with P(Doze) and P(Wake), suggesting that the methods capture the same behaviors. Importantly, we demonstrate that both the Doze/Wake probabilities and the sleep/wake substates are tied to specific biological processes. These metrics provide greater mechanistic insight into behavior than measuring the amount of sleep alone.

Noninvasive Fluorine-19 Magnetic Resonance Relaxometry Measurement of the Partial Pressure of Oxygen in Acellular Perfluorochemical-loaded Alginate Microcapsules Implanted in the Peritoneal Cavity of Nonhuman Primates.

We have utilized a noninvasive technique for measuring the partial pressure of oxygen (pO2) in alginate microcapsules implanted intraperitoneally in healthy nonhuman primates (NHPs). Average pO2 is important for determining if a transplant site and capsules with certain passive diffusion characteristics can support the islet viability, metabolic activity, and dose necessary to reverse diabetes. Perfluoro-15-crown-5-ether alginate capsules were infused intraperitoneally into 3 healthy NHPs. Peritoneal pO2 levels were measured on days 0 and 7 using fluorine-19 magnetic resonance relaxometry and a fiber-optic probe. Fluorine-19 MRI was used to determine the locations of capsules within the peritoneal space on days 0 and 7. Gross and histologic evaluations of the capsules were used to assess their biocompatibility postmortem. At day 0 immediately after infusion of capsules equilibrated to room air, capsules were concentrated near the infusion site, and the pO2 measurement using magnetic resonance relaxometry was 147 ± 9 mm Hg. On day 7 after capsules were dispersed throughout the peritoneal cavity, the pO2 level was 61 ± 11 mm Hg. Measurements using the fiber-optic oxygen sensor were 132 ± 7.5 mm Hg (day 0) and 89 ± 6.1 mm Hg (day 7). Perfluoro-15-crown-5-ether capsules retrieved on day 7 were intact and free-floating without host cell attachment, although the numbers of peritoneal CD20 B cells, CD4 and CD8 T cells, and CD14 macrophages increased consistent with a mild foreign body reaction. The peritoneal pO2 of normal NHPs is relatively low and we predict would decrease further when encapsulated islets are transplanted intraperitoneally.

Central arterial and peripheral arterial blood pressure in patients with chronic kidney disease undergoing versus not undergoing hemodialysis.

ObjectiveWe assessed the consistency of noninvasive and invasive measurements of central arterial pressure (CAP) and the difference between peripheral brachial artery pressure and CAP in patients with chronic kidney disease (CKD) undergoing versus not undergoing hemodialysis.MethodsThis single-center cross-sectional study was performed from May to December 2018. The patients were divided into a control group (n = 50), CKD group (stages 3–5, n = 50), and dialysis group (n = 20), and all underwent measurement of peripheral humeral arterial pressure and noninvasive and invasive measurement of CAP. Group differences and correlations between CAP and peripheral arterial pressure were assessed.ResultsThe consistency between noninvasive and invasive CAP was better in the control and CKD groups than in the dialysis group. In the dialysis group, the noninvasive equipment underestimated the actual CAP. The CAP was close to the peripheral brachial artery pressure in the dialysis group, while the CAP was significantly lower than the peripheral brachial artery pressure in the control and CKD groups.ConclusionNoninvasive equipment underestimates the actual CAP in patients undergoing dialysis and should be used with caution. The difference between the peripheral arterial pressure and CAP was smaller in patients undergoing dialysis than in patients with CKD and controls.

Identifying and treating high blood pressure in men under 55 years with grade 1 hypertension: the TREAT CASP study and RCT

Background There is uncertainty regarding whether or not younger (i.e. aged < 55 years), low-risk patients with grade 1 hypertension (i.e. a clinic blood pressure of 140–159/90–99 mmHg) should be treated with blood pressure-lowering medication. This is a heterogeneous group of patients because of variation in systolic/pulse pressure amplification from the central aorta to the brachial artery. It is hypothesised that within grade 1 hypertension, patients can be divided into those with high central aortic systolic pressure and those with low central aortic systolic pressure. Objectives The aims of this study were to (1) evaluate whether or not non-invasive central aortic systolic pressure measurement can better identify younger patients with grade 1 hypertension, who are more likely to have an increased left ventricular mass index; and (2) determine whether or not blood pressure lowering regresses early cardiac structural change in patients with high central aortic systolic pressure. Setting A university hospital with satellite primary care recruitment sites. Participants A total of 726 men (aged 18 to < 55 years) were screened to identify 162 men with grade 1 hypertension and low or high central aortic systolic pressure. Blood pressure status was classified according to seated clinic blood pressure, central aortic systolic pressure and 24-hour ambulatory blood pressure. Design (1) Evaluating the strength of the correlation between central aortic systolic pressure, clinic blood pressure and 24-hour ambulatory blood pressure with left ventricular mass index in 162 patients; (2) a 12-month randomised controlled trial in patients with grade 1 hypertension and high central aortic systolic pressure (i.e. a central aortic systolic pressure of ≥ 125 mmHg) (n = 105), using a prospective, open, blinded, end-point design; and (3) a 12-month observational study in 57 patients with grade 1 hypertension and low central aortic systolic pressure (i.e. a central aortic systolic pressure of < 125 mmHg). Interventions Randomised controlled trial – patients with high central aortic systolic pressure randomised to blood pressure lowering medication (50–100 mg of losartan ± 5–10 mg of amlodipine once daily) versus usual care (no treatment) for 12 months. Main outcomes Randomised controlled trial primary end point – change in left ventricular mass index as measured by cardiac magnetic resonance imaging, comparing treatment with no treatment. Results (1) At baseline, left ventricular mass index was higher in men with high central aortic systolic pressure than in those with low central aortic systolic pressure (mean ± standard deviation 67.9 ± 8.8 g/m2 vs. 64.0 ± 8.5 g/m2; difference 4.0 g/m2, 95% confidence interval 1.1 to 6.9 g/m2; p < 0.01). Central aortic systolic pressure was not superior to clinic blood pressure as a determinant of left ventricular mass index. Univariate analysis, regression coefficients and slopes for left ventricular mass index were similar for clinic systolic blood pressure, ambulatory systolic blood pressure and central aortic systolic pressure. (2) In the randomised controlled trial, blood pressure-lowering treatment reduced central aortic systolic pressure (–21.1 mmHg, 95% confidence interval – 24.4 to –17.9 mmHg; p < 0.001) and clinic systolic blood pressure (–20.0 mmHg, 95% confidence interval – 23.3 to –16.6 mmHg; p < 0.001) versus no treatment. Treatment was well tolerated and associated with a greater change (i.e. from baseline to study closeout) in left ventricular mass index versus no treatment [–3.3 g/m2 (95% confidence interval –4.5 to –2.2 g/m2) vs. –0.9 g/m2 (95% confidence interval –1.7 to –0.2 g/m2); p < 0.01], with a medium-to-large effect size (Cohen’s d statistic –0.74). (3) Patients with low central aortic systolic pressure had no significant change in left ventricular mass index after 12 months (mean change –0.5 g/m2, 95% confidence interval –1.2 to 0.2 g/m2; p = 0.18). Conclusions Men with grade 1 hypertension and high central aortic systolic pressure tended to have higher clinic blood pressure and more hypertension-mediated cardiac structural change than those with low central aortic systolic pressure. Central aortic systolic pressure was not superior to clinic blood pressure or ambulatory blood pressure at stratifying risk of increased left ventricular mass index. Blood pressure-lowering treatment led to a regression of left ventricular mass index in men with grade 1 hypertension and high central aortic systolic pressure compared with no treatment. Limitations The study was limited to a moderate sample of men and there was a low prevalence of very high amplification. Future work Evaluating effects of blood pressure lowering on cardiac function. Trial registration Current Controlled Trials ISRCTN09502665. Funding This project was funded by the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health Research (NIHR) partnership and will be published in full in Efficacy and Mechanism Evaluation; Vol. 6, No. 13. See the NIHR Journals Library website for further project information.

Pre-hospital use of capnography during emergency sedation analgesia

Background: Providing optimal patient care in the challenging, uncontrolled, and sometimes hostile pre-hospital environment may require the use of potent analgesics and sedatives. During pre-hospital emergencies, narcotics or sedatives administered for sedation, anxiolysis, or analgesia to allow the patient to tolerate unpleasant procedures, such as traction splint application, can result in cardiovascular and respiratory adverse events.1 Early recognition of poor oxygenation may prevent unnecessary patient hypoxia. The European Society of Anaesthesiology and the American Society of Anaesthesiologist mandate continuous capnography, in addition to standard monitoring which include pulse oximetry, 4-lead ECG, blood pressure, and heart rate measurements.1,2 Capnography refers to the non-invasive measurement of the partial pressure of carbon dioxide (CO2) in exhaled breath. Monitoring respiratory status provides early warning, thereby allowing clinicians to intervene before the onset of respiratory depression, potentially leading to bradypnoea, apnoea, hypoxia, and death.3 In addition, late identification of respiratory failure may lead to unnecessary endotracheal intubation and mechanical ventilation, increasing risk of protracted hospital stay and associated hospital-acquired infections.Oxygenation and ventilation must be measured in both intubated and spontaneously breathing patients. While clinical indicators like chest rise or the plethysmography-derived respiratory rate can be used, monitoring the capnographic waveform for hypopnoeic and bradypnoeic patterns provides the clinician with a quick, accurate indication of acute adverse respiratory events.4 In two randomized trials, patients monitored with capnography in addition to standard of care, experienced significantly fewer episodes of hypoxia than those monitored without capnography.3,5 Hamad Medical Corporation Ambulance Service (HMCAS) in Qatar introduced a new clinical practice guideline (CPG) for safe sedation and monitoring in August 2017, mandating the routine use of capnography for all sedated patients. Safe sedation is achieved when the patient's oxygenation, ventilation, or haemodynamic status is not negatively impacted by the sedation procedure. Methods: The study aimed to describe trends in the use of capnography and other monitoring modalities for patients receiving Ketamine, Fentanyl, or Midazolam. Retrospective quantitative analysis of an existing HMCAS medical records database linked to a Business Intelligence (BI) tool enabled direct analysis on the tool and via a linked Microsoft Excel® spreadsheet, reviewing all emergency cases from 1st January 2017 to 31st December 2018. Frequency analysis and measures of central tendency was applied to the relevant clinical variables. All patient and practitioner identifiable data fields were redacted and not reported on. Results: Oxygen saturation (SpO2) and blood pressure monitoring was used on all patients (n = 5157, 100%), 4-lead ECG was placed on 3710 (72%) patients, while capnography was used on 4096 patients (79%, range = 39% to 99%). Capnography usage steadily improved over the 24-month period, especially for patients receiving Fentanyl (Figure 1). Conclusion: There was a significant improvement in the use of capnography during monitoring of patients that received Fentanyl, Ketamine, or Midazolam, with the most significant improvement for patients receiving Fentanyl alone. Further studies are required to determine the impact of this improvement on actual adverse event frequency.

Impact of hydrostatic pressure on phase-change contrast agent activation by pulsed ultrasound.

A phase-change contrast agent (PCCA) can be activated from a liquid (nanodroplet) state using pulsed ultrasound (US) energy to form a larger highly echogenic microbubble (MB). PCCA activation is dependent on the ambient pressure of the surrounding media, so any increase in hydrostatic pressure demands higher US energies to phase transition. In this paper, the authors explore this basic relationship as a potential direction for noninvasive pressure measurement and foundation of a unique technology the authors are developing termed tumor interstitial pressure estimation using ultrasound (TIPE-US). TIPE-US was developed using a programmable US research scanner. A custom scan sequence interleaved pulsed US transmissions for both PCCA activation and detection. An automated US pressure sweep was applied, and US images were acquired at each increment. Various hydrostatic pressures were applied to PCCA samples. Pressurized samples were imaged using the TIPE-US system. The activation threshold required to convert PCCA from the liquid to gaseous state was recorded for various US and PCCA conditions. Given the relationship between the hydrostatic pressure applied to the PCCA and US energy needed for activation, phase transition can be used as a surrogate of hydrostatic pressure. Consistent with theoretical predictions, the PCCA activation threshold was lowered with increasing sample temperature and by decreasing the frequency of US exposure, but it was not impacted by PCCA concentration.

Diagnostic value of noninvasive pulse pressure measurements in Warmblood horses with aortic regurgitation.

BackgroundNoninvasive blood pressures (NIBP) and pulse pressures (PP) have not been published in horses with aortic and mitral regurgitation (AR or MR).ObjectivesTo investigate NIBP and PP in healthy Warmblood horses and horses with AR and MR and propose PP cutoffs to identify and stage AR severity.AnimalsSeventy‐three Warmblood horses (healthy, 10; AR, 31; MR, 32).MethodsRetrospective study. All horses had NIBP and an echocardiogram recorded. Cases were categorized based on severity of regurgitation. Pulse pressures were compared among healthy, MR, and AR groups and among AR severity groups. Cutoffs were determined by receiver operating characteristic curve analyses.ResultsHorses with AR had higher PP than horses with MR (mean difference [95% confidence interval (CI)], +17 [9‐26] mm Hg, P < .001) and controls (+17 [5‐30] mm Hg; P =.004). Horses with severe AR had higher PP compared those with mild (+38 [20‐54] mm Hg; P < 0.001) and moderate AR (+33 [18‐47] mm Hg; P < .001). The PP cutoffs to distinguish AR from MR and controls were 38 mm Hg (sensitivity [Sn], 100%; specificity [Sp], 19%) for maximal Sn and 61 mm Hg (Sn, 43%; Sp, 100%) for maximal Sp. The PP cutoffs to distinguish severe AR from mild and moderate AR were 57 mm Hg (Sn, 100%; Sp, 70%) for maximal Sn and 77 mm Hg (Sn, 75%; Sp, 100%) for maximal Sp.Conclusions and Clinical ImportanceHorses with AR have increased PP. Noninvasive PP measurements interpreted with provided cutoffs may aid clinicians in diagnosing and staging severity of AR in horses.

Bidirectional Ultrasound Elastographic Imaging Framework for Non-invasive Assessment of the Non-linear Behavior of a Physiologically Pressurized Artery

Studies of non-destructive bidirectional ultrasound assessment of non-linear mechanical behavior of the artery are scarce in the literature. We hereby propose derivation of a strain–shear modulus relationship as a new graphical diagnostic index using an ultrasound elastographic imaging framework, which encompasses our in-house bidirectional vascular guided wave imaging (VGWI) and ultrasound strain imaging (USI). This framework is used to assess arterial non-linearity in two orthogonal (i.e., longitudinal and circumferential) directions in the absence of non-invasive pressure measurement. Bidirectional VGWI estimates longitudinal (μL) and transverse (μT) shear moduli, whereas USI estimates radial strain (ɛr). Vessel-mimicking phantoms (with and without longitudinal pre-stretch) and in vitro porcine aortas under static and/or dynamic physiologic intraluminal pressure loads were examined. ɛr was found to be a suitable alternative to intraluminal pressure for representation of cyclic loading on the artery wall. Results revealed that μT values of all samples examined increased non-linearly with εr magnitude and more drastically than μL, whereas μL values of only the pre-stretched phantoms and aortas increased with ɛr magnitude. As a new graphical representation of arterial non-linearity and function, strain–shear modulus loops derived by the proposed framework over two consecutive dynamic loading cycles differentiated sample pre-conditions and corroborated direction-dependent non-linear mechanical behaviors of the aorta with high estimation repeatability.

Total thyroidectomy in patient with McArdle's syndrome: Anaesthetic management

McArdle disease or type V glycogenosis is a rare metabolic myopathy consisting of muscle loss and weakness. These patients have risks associated with anaesthesia. They can present with hypoglycaemia, rhabdomyolysis, acute renal failure, and electrolyte changes. It has also been associated with a higher incidence of malignant hyperthermia during the anaesthetic procedure. Intermittent compression due to the measurement of non-invasive pressure, postures on the operating table that may cause muscle contractures, or tremor caused by hypothermia or anaesthesia itself, may trigger rhabdomyolysis in these patients. In this article we present our experience in submitting a patient with McArdle's syndrome to general anaesthesia for total thyroidectomy due to multinodular euthyroid goitre.

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage.

Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications. To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study. The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes. A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered. This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Measurement of the Local Sound Pressure on a Bias-Flow Liner Using High-Speed Holography and Tomographic Reconstruction

Bias-flow liners (BFL) are used as part of the cooling mechanism in airplane turbines and they also enable the reduction of noise emission. The attenuating principle is based on the interaction between sound waves and air flow. This turbulent aeroacoustic interaction occurs on a microscopic level and under harsh conditions. Therefore, in order to investigate local aeroacoustic phenomena, the distribution of the local sound field impedance, defined as sound pressure over acoustic particle velocity, is measured non-invasively. This work focuses on the non-invasive measurement of the local sound pressure. A fast camera-based holographic measurement system for the two dimensional tomographic measurement of the local sound pressure with high spatial resolution is presented. It features a spatial resolution of 52 μm with a simultaneous acquisition of up to 1600 measuring points. This enables the observation of sub-mm aeroacoustic effects, which are expected in the near field over the BFL's surface, while reducing the measurement duration by three orders of magnitude compared to single point measurement systems. An experimental validation of the camera-based tomographic system is carried out by reference measurements. The system was applied at an acoustical model and an aeroacoustic model. The measured local sound pressure variations are discussed for both models. This work seeks to enable the non-invasive investigation of sound pressure, in order to further understand aeroacoustic effects, their sound attenuating properties and increase the attenuation capability of a BFL without degrading the overall performance of turbines.

Intraocular pressure remote photonic biomonitoring based on temporally encoded external sound wave stimulation.

Continuous noninvasive measurement of intraocular pressure (IOP) is an important tool in the evaluation process for glaucoma. We present a methodology enabling high-precision, noncontact, reproducible, and continuous monitoring of IOP based on the value of the damping factor of transitional oscillations obtained at the surface of the eye after terminating its stimulation by a sound wave. The proposed configuration includes projection of a laser beam and usage of a fast camera for analyzing the temporal-spatial variations of the speckle patterns backscattered from the iris or the sclera following the above-mentioned sound waves external stimulation. The methodology was tested on an artificial eye and a carp fish eye under varying pressure as well as on human eyes.

Advanced imaging in pulmonary hypertension: emerging techniques and applications.

Pulmonary hypertension (PH) is a pathophysiological disorder defined by an increase in pulmonary arterial pressure which can occur in multiple clinical conditions. Irrespective of etiology, PH entails a negative impact on exercise capacity and quality of life, and is associated with high mortality particularly in pulmonary arterial hypertension. Noninvasive imaging techniques play an important role in suggesting the presence of PH, providing noninvasive pulmonary pressure measurements, classifying the group of PH, identifying a possibly underlying disease, providing prognostic information and assessing response to treatment. While echocardiography, computed tomography (CT) and ventilation/perfusion scans are an integral part of routine work-up of patients with suspected PH according to current guidelines and across centers, innovative new techniques and applications in the field of PH such as 3D echocardiography, dual-energy CT, 4D flow magnetic resonance imaging (MRI), T1 and extracellular volume fraction mapping, non-contrast-enhanced MRI sequences for perfusion and ventilation assessment, and molecular-targeted positron emission tomography are emerging. This review discusses advanced and emerging imaging techniques in diagnosis, prognostic evaluation and follow-up of patients with PH.