Continuous Pressure Measurement Research Articles

Conforto e desconforto em cabines de aeronaves: um método baseado na análise da atividade

Resumo A literatura mostra que as poltronas aeronáuticas usualmente são avaliadas por métodos objetivos em experimentos estáticos e realizados fora do seu contexto de uso. O objetivo deste artigo é apresentar um método que utiliza medição contínua de pressão de interface ocupante-poltrona em conjunto com outras técnicas, como observação, relato pós-experimento e filmagem para avaliar o conforto e o desconforto de poltronas e cabines de aeronaves em suas fases de concepção e desenvolvimento. Na primeira etapa do método, os participantes avaliaram as condições para realizar as atividades de ler e repousar em ensaios de 40 minutos, realizados em um simulador de interior de cabine de aeronave. Na segunda etapa, foi realizada uma sessão de brainstorming para gerar ideias e captar oportunidades de melhoria para a poltrona e a cabine da aeronave avaliada. Na última etapa, uma solução sugerida no brainstorming foi prototipada e avaliada em condição de uso.

Extracellular Matrix Disarray as a Mechanism for Greater Abdominal Versus Thoracic Aortic Stiffness With Aging in Primates

Increased vascular stiffness is central to the pathophysiology of aging, hypertension, diabetes mellitus, and atherosclerosis. However, relatively few studies have examined vascular stiffness in both the thoracic and the abdominal aorta with aging, despite major differences in anatomy, embryological origin, and relation to aortic aneurysm. The 2 other unique features of this study were (1) to study young (9±1 years) and old (26±1 years) male monkeys and (2) to study direct and continuous measurements of aortic pressure and thoracic and abdominal aortic diameters in conscious monkeys. As expected, aortic stiffness, β, was increased P<0.05, 2- to 3-fold, in old versus young thoracic aorta and augmented further with superimposition of acute hypertension with phenylephrine. Surprisingly, stiffness was not greater in old thoracic aorta than in young abdominal aorta. These results can be explained, in part, by the collagen/elastin ratio, but more importantly, by disarray of collagen and elastin, which correlated best with vascular stiffness. However, vascular smooth muscle cell stiffness was not different in thoracic versus abdominal aorta in either young or old monkeys. Thus, aortic stiffness increases with aging as expected, but the most severe increases in aortic stiffness observed in the abdominal aorta is novel, where values in young monkeys equaled, or even exceeded, values of thoracic aortic stiffness in old monkeys. These results can be explained by alterations in collagen/elastin ratio, but even more importantly by collagen and elastin disarray.

Hydraulic Modeling of a Water Distribution Network in a Tourism Area with Highly Varying Characteristics

Hydraulic models are efficient decision support tools for effective management of water distribution networks (WDNs). This study presents an EPANET hydraulic model application at Old Town DMA (District Metered Area), a well-known tourism area in Antalya City, Turkey. Old Town DMA has highly variable WDN characteristics and it contains about 1400 active and inactive water subscribers, mostly related to tourism facilities. Daily and hourly water consumption profiles and water consumption rates by different subscribers in the DMA exhibit wide variations. The temporal and spatial variations of water consumptions and highly varying topographic levels of the DMA are taken into account to allocate nodal water demand in hydraulic modeling. Water pressure and flow rates are continuously monitored online at the SCADA station located at the entrance of the DMA. Additionally, continuous water pressure measurements are performed via portable pressure loggers at 4 different points located at different elevations of the DMA. The monthly water consumption of each water subscriber is recorded. Moreover, the daily and hourly water consumption rates of 13 different water subscribers were monitored for 5 days. The obtained data sets were used to prepare water consumption patterns for different water subscribers and to estimate nodal demands. The hydraulic model was calibrated for Hazen - Williams pipe roughness coefficient and the predicted pressure values were in good agreement with field measurements.

Continuous urethral pressure measurements; measurement techniques; pressure variations; clinical interpretations; and clinical relevance. A Systematic Literature Analysis.

The clinical relevance of urethral pressure variations (UPV) in the pathophysiology of over active bladder syndrome (OAB) has remained controversial to date. Some studies report an association with OAB and/or detrusor over activity (DO). Recently the International Consultation on Incontinence-Research Society recommended new clinical research to be performed on this subject. We provide a systematic review of the literature to specify this recommendation. Literature search was performed in PubMed, Embase, Web of Science, Cochrane, Central, Cinahl, Academic Science Premier, Science Direct, and Wiley Online using a sensitive search string combination. All authors independently reviewed and scored full text papers and consensus about methodological quality was obtained according to Oxford Level of Evidence (LoE). Four hundred eighty seven abstracts were screened, 25 papers met all predefined inclusion selection criteria. Incidence figures of UPV varied between 2% and 95%. Studies are of poor methodological quality with Oxford LoE scores of 3B and 4. Measurement methods and techniques show a large variety. The above mentioned association of DO/OAB with UPV is however frequently reported. There exists a phenomenon of UPV, apart from DO, which may be a separate entity within OAB syndrome. Large variation in measurement techniques and patient populations hinders fundamental research as well as clinical progress. Clinical relevance of UPV and consequences for treatment therefore are yet to be established. Future prospective research with well-defined patient population and standardised urodynamic measurement techniques is needed. Results of standardized and objective evaluations should be compared to clinical signs and symptoms by validated questionnaires. Neurourol. Urodynam. 36:51-56, 2017. © 2015 Wiley Periodicals, Inc.

Fluid management guided by a continuous non-invasive arterial pressure device is associated with decreased postoperative morbidity after total knee and hip replacement.

BackgroundThe use of goal directed fluid protocols in intermediate risk patients undergoing hip or knee replacement was studied in few trials using invasive monitoring. For this reason we have implemented two different fluid management protocols, both based on a novel totally non-invasive arterial pressure monitoring device and compared them to the standard (no-protocol) treatment applied before the transition in our academic institution.MethodsThree treatment groups were compared in this prospective study: the observational (CONTROL, N = 40) group before adoption of fluid protocols and two randomized groups after the transition to protocol fluid management with the use of the continuous non-invasive blood pressure monitoring (CNAP®) device. In the PRESSURE group (N = 40) standard variables were used for restrictive fluid therapy. Goal directed fluid therapy using pulse pressure variation was used in the GDFT arm (N = 40). The influence on the rate of postoperative complications, on the hospital length of stay and other parameters was assessed.ResultsBoth protocols were associated with decreased fluid administration and maintained hemodynamic stability. Reduced rate of postoperative infection and organ complications (22 (55 %) vs. 33 (83 %) patients; p = 0.016; relative risk 0.67 (0.49–0.91)) was observed in the GDFT group compared to CONTROL. Lower number of patients receiving transfusion (4 (10 %) in GDFT vs. 17 (43 %) in CONTROL; p = 0.005) might contribute to this observation. No significant differences were observed in other end-points.ConclusionIn our study, the use of the fluid protocol based on pulse pressure variation assessed using continuous non-invasive arterial pressure measurement seems to be associated with a reduction in postoperative complications and transfusion needs as compared to standard no-protocol treatment.Trial registrationACTRN12612001014842Electronic supplementary materialThe online version of this article (doi:10.1186/s12871-015-0131-8) contains supplementary material, which is available to authorized users.

ICP During Daily Life in Healthy Adults: What Does Microgravity Add to the Mix?

PURPOSEDue to visual changes seen in astronauts, the primary objective is to make the first direct, invasive measurements of intracranial pressure (ICP) during changes in hydrostatic gradients experienced during daily life and induced by simulated and real microgravity.METHODSSubjects are four healthy adults who previously had an Ommaya reservoir implanted, which allows continuous pressure measurements to be made. Central venous pressure (CVP) is measured by a peripherally inserted central catheter. Hemodynamics are obtained upright, supine, then after 5 min, 3 hrs and 24 hrs of 6° head‐down tilt (HDT). Measurements are repeated during real microgravity (parabolic flight).RESULTSICP increased by transitioning from the sitting to supine position (4±2 vs 15±2 mmHg); ICP increased further with HDT (17±3, Δ2 mmHg), but returned towards normal values after 3 hrs (16 mmHg) and 24 hrs (14 mmHg). In comparison to the supine position, CVP tended to decrease over time during HDT (5 min, Δ1 mmHg; 3 hrs, Δ2 mmHg; 24 hrs, Δ1 mmHg). ICP increased during the 1.8g (Gx) phase of the parabola (from supine 17±2 to 25±2). However, ICP fell dramatically during 0g (to 13±4, Δ12 mmHg). The magnitude of the reduction in ICP is the combination of removing the 1.8 Gx and the subsequent fall in CVP (1g, 5±4; 1.8g, 7±5; 0g, 4±3).imageConclusionsElevated ICP is unlikely to be the culprit for visual impairment in space. Alternatively, visual impairments may be simply due to consistently “elevated” ICP relative to the upright posture, due to the inability to “stand‐up” in space.

Continuous noninvasive arterial pressure measurement using the volume clamp method: an evaluation of the CNAP device in intensive care unit patients

The CNAP system allows continuous noninvasive arterial pressure measurement based on the volume clamp method using a finger cuff. We aimed to evaluate the agreement between arterial pressure measurements noninvasively obtained using the CNAP device and arterial catheter-derived arterial pressure measurements in intensive care unit patients. In 55 intensive care unit patients, we simultaneously recorded arterial pressure values obtained by an arterial catheter placed in the abdominal aorta through the femoral artery (criterion standard) and arterial pressure values determined noninvasively using CNAP. We performed Bland-Altman analysis and calculated the percentage error. The mean difference (±standard deviation, 95% limits of agreement, percentage error) between noninvasive (CNAP) and invasively assessed arterial pressure was for mean arterial pressure +1 mmHg (±9 mmHg, -16 to +19 mmHg, 22%), for systolic arterial pressure -10 mmHg (±16 mmHg, -42 to +21 mmHg, 27%), and for diastolic arterial pressure +7 mmHg (±9 mmHg, -10 to +24 mmHg, 28%). Our results indicate a reasonable accuracy and precision for the determination of mean and diastolic arterial pressure by noninvasive continuous arterial pressure measurements using the volume clamp method compared with the criterion standard (invasive arterial catheter). Systolic arterial pressure is determined less accurately and precisely.

Cerebral autoregulation in the microvasculature measured with near-infrared spectroscopy.

Cerebral autoregulation (CA) is the mechanism that allows the brain to maintain a stable blood flow despite changes in blood pressure. Dynamic CA can be quantified based on continuous measurements of systemic mean arterial pressure (MAP) and global cerebral blood flow. Here, we show that dynamic CA can be quantified also from local measurements that are sensitive to the microvasculature. We used near-infrared spectroscopy (NIRS) to measure temporal changes in oxy- and deoxy-hemoglobin concentrations in the prefrontal cortex of 11 human subjects. A novel hemodynamic model translates those changes into changes of cerebral blood volume and blood flow. The interplay between them is described by transfer function analysis, specifically by a high-pass filter whose cutoff frequency describes the autoregulation efficiency. We have used pneumatic thigh cuffs to induce MAP perturbation by a fast release during rest and during hyperventilation, which is known to enhance autoregulation. Based on our model, we found that the autoregulation cutoff frequency increased during hyperventilation in comparison to normal breathing in 10 out of 11 subjects, indicating a greater autoregulation efficiency. We have shown that autoregulation can reliably be measured noninvasively in the microvasculature, opening up the possibility of localized CA monitoring with NIRS.

Cuff pressure change during anterior cervical spine surgeries and its effects postoperatively

Background: Anterior cervical spine surgeries carry significant morbidity postoperatively due to dysphagia, vocal cord palsy, etc. Retraction of tissues of the neck causes a rise in endotracheal cuff pressure, which can be measured using pressure transducer. This prospective and observational study was done to detect the changes in cuff pressure on retraction of soft tissues of the neck and also to assess postoperative morbidity related to the airway. Materials and Methods: Forty patients scheduled for anterior cervical spine surgery of American Society of Anesthesiologists (ASA) grades I or II were studied. Continuous cuff pressure measurement was done using a pressure transducer attached to the pilot balloon of the endotracheal tube after induction of anesthesia and endotracheal intubation. Anesthesia was maintained with 50% O 2 in N 2 O and isoflurane with intermittent doses of atracurium. Changes in cuff pressure before retraction, during retraction, and after removal of retractors were measured. No adjustment of cuff pressure was done. Postoperatively, the patients were observed for sore throat, dysphagia, and hoarseness of voice for 3 days. Video laryngoscopy was planned in case of prolonged hoarseness of voice for more than 2 days. Results: Time-adjusted mean cuff pressure before retraction was 23.10 ± 7.51 mmHg, which increased significantly during retraction (50.69 ± 17.63 mmHg). After removal of retractors, cuff pressure decreased to 37.98 ± 15.04 mmHg. Postoperatively, the average duration of sore throat was 31.65 ± 22.48 h, that of dysphagia was 34.80 ± 20.66 h, and that of hoarseness of voice was 1.96 h. Conclusion: Endotracheal cuff pressure rises significantly during neck retraction in anterior cervical spine surgeries. There is consistent postoperative morbidity related to the airway in these patients, which is self-limiting.

Pulsatile cerebrospinal model with cardio-vascular coupling

In this paper we describe a model of the human intracranial space which is extended with the vascular system. We focus on a detailed modelling of the coupling between cerebral vessels and intracranial pressure (ICP). On the one hand, the model is based on a linearisation of the Navier-Stokes equation for the blood vessels and a subsequent geometric discretisation, leading to a distributed parameter approach of coupled ordinary differential equations. On the other hand, a concentrated parameter modelling approach is developed for the intracranial space which is subsequently extended by a production and resorption circuit for the craniospinal fluid. The intention of the model is to describe the transmission of pulsatile blood pressure waves from the cerebral vessels to the ICP, as it can be observed from clinical continuous intracranial pressure measurements. A good agreement of pulsatile ICP is shown in an in-silico study, compared to clinical continuous ICP measurements. An analysis of vascular impedance under variable intracranial compliance and for a non-symmetric Circle-of-Willis completes this study.

Continuous Intraocular Pressure Monitoring by Non-Invasive Wireless Pressure Sensor

This project presents that the glaucoma is the second leading cause of blindness and is most accurately defined as a collection of diseases that have in common, damage to the optic nerve and loss of visual field with increased intraocular pressure (IOP) being the primary risk factor. Though there are treatments available, there is a requirement to develop improved diagnostic and therapeutic techniques to overcome this disease. A continuous intraocular pressure measurement during the patients’ routine daily activity can provide a valuable insight. Here microcontroller is used to convert the analog signal to digital and which the sensor output through which the pressure of the eye is measured continuously and the monitored data can be send via wireless technology through ZigBee. The transmitted data can be viewed by the doctors through PC were it is received by the ZigBee transceiver.

J2410403 液体金属を用いたボールペン型圧力センサの開発

This paper demonstrates a ballpoint pen like pressure sensor for endoscopic palpation, which can conduct continuous pressure measurement at different locations while a metal ball on the tip rotates. This device is a capacitive-typed pressure sensor which obtains applying force or pressure data from capacitance changes. PDMS polymer is used for the sensor base and liquid metal is used for electrodes to form them on the cylindrical sides. This device has double cylinder and 4 electrodes on its sides surrounding the ball. These are arranged alternately to form 4 capacitors, which can detect the sizes and directions of the applying force vertically to the axis of the ballpoint pen. The device was fabricated and tested by using Micro Autograph and LCR meter, in which loads were applied to three different directions while the capacitance of the equipped capacitors were measured. As a result, it was observed that the only capacitance ratios of capacitor which was applied force increased and this device was verified to be able to detect the sizes and directions of applied force in all directions.

PS-264 Comparison Of Two Manual Ventilation Devices On The Paediatric Intensive Care: The Self-inflating Bag Versus The Flow-inflating Bag

Objective Different types of devices for manual (bag) ventilation are available. But which device is the best to use is still a matter of controversy. Most frequently used devices in Dutch PICU’s include the Self Inflating Bag (SIB) and the Flow Inflating Bag (FIB). The choice of the system seems to be subjective, and depend mostly on unit policy or personal preferences. Studies on manual ventilation in the paediatric population are scarce. We therefore conducted a prospective, observational study to compare both devices with regard to peak pressures generated and consequences on respiratory parameters during manual ventilation of intubated and mechanically ventilated children. Setting A paediatric intensive care unit of an university hospital. Patients Patients admitted to the PICU; intubated with tube size 3.0, 3.5 or 4 and mechanically ventilated were eligible for the study. Interventions Manual ventilation was performed with two devices, a Laerdal Silicone paediatric circuit and a Mapleson C cirucuit. After inclusion, a tap was placed at the end of the manual inflation bag tube allowing for continuous pressure measurements during manual ventilation. Subjects were blinded to pressure recording and no feedback was provided. From each measurement a maximum peak pressure, mean peak pressure (+SD), median peak pressure and a frequency was calculated. Main Results 412 measurements in 39 patients were performed (205/207). Both groups had significant higher peak pressures and median delivered pressure during manual ventilation (for both groups p = . 000) when compared to ventilator settings. Discussion This study demonstrates that in order to perform MH in a safe and effective manner the pressures and volumes generated have to be monitored.

Preliminary research on clinical value of localization of upper airway obstruction with nasopharyngeal airway combined with polysomnography

To investigate the clinical value of localization of upper airway obstructive site with the method of combination of nasopharyngeal airway and polysomnography (PSG). Forty-seven patients diagnosed as obstructive sleep apnea hypopnea syndrome (OSAHS) by PSG were enrolled. Each patient was examined by Somte PSG for the first night, underwent repeated PSG examination with the nasopharyngeal airway in place for the second night and received airway continuous pressure measurements (ApneaGraph) examination for the third night. The standard of treatment success was defined as apnea-hypopnea index (AHI) less than 20/h and a reduction of 50% or more. The patients were divided into success group and failure group. The PSG indices and ApneaGraph data of the two groups were compared. Correlations between AHI with nasopharyngeal airway in place by PSG and lower AHI and constituent ratio of lower obstruction by ApneaGraph were calculated. SPSS 17.0 software was used to analyze the data. Forty-two patients completal three-night examination. With the nasopharyngeal airway in place, AHI, the lowest oxyhemoglobin saturation (LSaO2), average oxyhemoglobin saturation, percent of sleep time with oxyhemoglobin saturation <0.90 (SaO2 < 0.90T%) were improved obviously (P < 0.001). Twenty-nine patients (69.0%) achieved treatment success. There were statistical differences (t = 2.670, P = 0.011; Z = -3.252, P = 0.001 and t = -4.556, P < 0.001) of LSaO2 by PSG, lower AHI and constituent ratio of lower obstruction by ApneaGraph compared success group with failure group. The correlations between AHI with nasopharyngeal airway in place by PSG and lower AHI and constituent ratio of lower obstruction by ApneaGraph were 0.616 (P < 0.001) and 0.526 (P < 0.001). The method of combination of nasopharyngeal airway with PSG is a reliable method of localization of upper airway obstructive site and can be used as a simple means to find out if there's any retroglossal obstruction.

Cardiovascular and thermoregulatory biomarkers of heat stroke severity in a conscious rat model.

Multiorgan failure is a catastrophic consequence of heat stroke (HS) and considered the underlying etiology of mortality. Identifying novel biomarkers capable of predicting the extent of HS-induced organ damage will enhance point-of-care triage and treatment. Conscious male F344 rats (n = 32) were radiotelemetered for continuous core temperature (Tc), heart rate, and arterial pressure measurement. Twenty-two animals were exposed to ambient temperature of 37°C to a maximum Tc of 41.9 ± 0.1°C. Rats were euthanized at 24 h of recovery for analysis of plasma biomarkers [cardiac troponin I (cTnI), blood urea nitrogen (BUN), alanine aminotransferase (ALT), albumin, glucose] and histology. Tc profiles observed during recovery stratified HS severity into Mild, Moderate, and Severe. Eleven (50%) animals exhibited an acute compensatory hemodynamic response to heat exposure and a monophasic Tc profile consisting of sustained hyperthermia (∼1°C). Five (23%) rats displayed hemodynamic challenge and a biphasic Tc profile with rapid return to baseline followed by rebound hyperthermia. All biomarkers were significantly altered from control values (P < 0.05). Four (18%) animals exhibited significant hemodynamic compromise during heat and a triphasic profile characterized by rapid cooling to baseline Tc, rebound hyperthermia, and subsequent hypothermia (∼35°C) through 24 h. cTnI showed a 40-fold increase over CON (P < 0.001) and correlated with BUN (r = 0.912) consistent with cardiorenal failure. Hypoglycemia correlated with ALT (r = 0.824) suggestive of liver dysfunction. Histology demonstrated myocardial infarction, renal tubular necrosis, and acute liver necrosis. Two (9%) animals succumbed during HS recovery. This study identified novel biomarkers that predict HS severity and organ damage during acute recovery that could provide clinical significance for identifying key biomarkers of HS pathogenesis.

Intradiscal pressure depends on recent loading and correlates with disc height and compressive stiffness

Intervertebral discs exhibit time-dependent deformation (creep), which could influence the relation between applied stress and intradiscal pressure. This study investigates the effect of prolonged dynamic loading on intradiscal pressure, disc height and compressive stiffness, and examines their mutual relationships. Fifteen caprine lumbar discs with 5 mm of vertebral bone on either side were compressed by 1 Hz sinusoidal load for 4.5 h. After preload, 'High' (130 ± 20 N) or 'Low' (50 ± 10 N) loads were alternated every half hour. Continuous intradiscal pressure measurement was performed with a pressure transducer needle. Each disc showed a linear relationship between axial compression and intradiscal pressure (R (2) > 0.91). The intercept of linear regression analysis declined over time, but the gradient remained constant. Disc height changes were correlated to intradiscal pressure changes (R (2) > 0.98): both decreased during High loading, and increased during Low loading. In contrast, compressive stiffness increased during High loading, and was inversely related to intradiscal pressure and disc height. Intradiscal pressure is influenced by recent loading due to fluid flow. The correlations found in this study suggest that intradiscal pressure is important for disc height and axial compliance. These findings are relevant for mechanobiology studies, nucleus replacements, finite element models, and ex vivo organ culture systems.

Continuous Blood Pressure Measurement Method Based on the Pulse Image Sensor and BP Neural Network

A continuous pressure measurement method is proposed based the pulse image sensor and BP neural network for continuous measurement of arterial blood pressure. The multi-information synchronous acquisition system is built to collect pulse image sequences, sphygmopalpation pressure, probe internal pressure, and blood pressure of subjects. The feature vector is formed from pulse image sequences, sphygmopalpation pressure, and probe internal pressure to predict continuous blood pressure by BP neural network. The results show that the mean difference (MD) and standard deviation (SD) of systolic blood pressure (SBP) and diastolic blood pressure (DBP) meet the standard of Association for the Advancement of Medical Instrumentation (AAMI). The method could be used to predict continuous blood pressure and provides a new method for arterial continuous blood pressure measurement.

Detection of Hypotension During Caesarean Section With Continuous Noninvasive Arterial Pressure Device or Intermittent Oscillometric Arterial Pressure Measurement

Detection of Hypotension During Caesarean Section With Continuous Noninvasive Arterial Pressure Device or Intermittent Oscillometric Arterial Pressure Measurement

Noninvasive Hemodynamic Monitoring Devices

Noninvasive Hemodynamic Monitoring Devices

Geometry dependent reaction response of Ta + Bi2O3 thermite powder filled linear cellular alloys

The impact initiated reaction response of a Ta + Bi2O3 thermite powder mixture encapsulated in two different maraging steel geometric structures was investigated. Experiments were performed on the Ta + Bi2O3 mixture initially compressed to ∼40% theoretical maximum density in a hollow cylinder and 9-Cell linear cellular alloy (LCA) structure, both of equivalent relative solid density. The powder filled structures were impacted against a rigid high-strength anvil over the velocity range of 60–204 m s−1. Reactions were observed in the powder mixture at velocities as low as 60 m s−1 in the 9-Cell LCA structure, and at 105 m s−1 for the hollow cylinder geometry. Three dimensional simulations of the powder filled structures impacting a rigid anvil were carried out at velocities near the reaction threshold conditions. Continuous measurements of pressure and strain were recorded in the simulation at several locations within the powder filler and solid walls of the maraging steel LCA structures. Comparison of calculated results with experimental findings suggested that reaction of the powder filler in both encapsulating geometries occurred at late times as a result of an activated microstructure and elevated temperatures.