Continuous Measurement Of Pressure Research Articles

Effect of continuous measurement and adjustment of endotracheal tube cuff pressure on postoperative sore throat in patients undergoing gynecological laparoscopic surgery: a randomized controlled trial.

Postoperative sore throat (POST) is a common complication following endotracheal tube removal, and effective preventive strategies remain elusive. This trial aimed to determine whether actively regulating intraoperative cuff pressure below the tracheal capillary perfusion pressure threshold could effectively reduce POST incidence in patients undergoing gynecological laparoscopic procedures. This single-center, randomized controlled superiority trial allocated 60 patients scheduled for elective gynecological laparoscopic procedures into two groups: one designated for cuff pressure measurement and adjustment (CPMA) group, and a control group where only cuff pressure measurement was conducted without any subsequent adjustments. The primary outcome was POST incidence at rest within 24h post-extubation. Secondary outcomes included cough, hoarseness, postoperative nausea and vomiting (PONV) incidence, and post-extubation pain severity. The incidence of sore throat at rest within 24h after extubation in the CPMA group was lower than in the control group, meeting the criteria for statistically significant superiority based on a one-sided test (3.3% vs. 26.7%, P < 0.025). No statistically significant differences were observed in cough, hoarseness, or pain scores within 24h post-extubation between the two groups. However, the CPMA group had a higher incidence of PONV compared to the control group. Additionally, the control group reported higher sore throat severity scores within 24h post-extubation. Continuous monitoring and maintenance of tracheal tube cuff pressure at 18 mmHg were superior to merely monitoring without adjustment, effectively reducing the incidence of POST during quiet within 24h after tracheal tube removal in gynecological laparoscopic surgery patients. The study was registered at www.chictr.org.cn (ChiCTR2200064792) on 18/10/2022.

Pressure estimation via measurement of reduced light scattering coefficient by oblique laser incident reflectometry

Continuous measurement of pressure is vital in many fields of industry, medicine, and science. Of particular interest is the ability to measure pressure in a noninvasive and contact-free manner. This work presents the potential of oblique incident reflectometry (OIR) to monitor variation in pressure via the reduced scattering parameter (μs′). Pressure deforms the geometry of the medium and causes distortion of its internal structure and the spatial distribution of optical properties. Light scattering is related to the morphology (size, density, distribution, etc.) and refractive index distributions of the medium, and applied pressure will influence directly these parameters. Therefore, we assume that pressure can be quantitatively assessed through monitoring the reduced scattering coefficient. For this purpose, the technique of OIR to evaluate the scattering parameter during pressure variations was utilized. OIR is a simple noninvasive and contact-free imaging technique able to quantify both absorption and scattering properties of a sample. In our setup, the medium is illuminated obliquely by a narrow laser beam, and the diffuse reflectance light is captured by a CCD camera. In offline processing, the shift (δ) of the diffuse light center from the incident point is mathematically analyzed and μs′ coefficient (μs′∼δ−1) is extracted. We present here confirmation of the validity of this assumption through results of a series of experiments performed on turbid liquid and artery occlusion of a human subject under different pressure levels. Thus, μs′ has the potential to serve as a good indicator for the monitoring of pressure.

Nonclassical Growth Mechanism of Double-Walled Metal-Oxide Nanotubes Implying Transient Single-Walled Structures.

The formation of imogolite nanotubes is reported to be a kinetic process involving intermediate roof-tile nanostructures. Here, the structural evolution occurring during the synthesis of aluminogermanate double-walled imogolite nanotubes is in situ monitored, thanks to an instrumented autoclave allowing the control of the temperature, the continuous measurement of pH and pressure, and the regular sampling of gas and solution. Chemical analyses confirm the completion of the precursor's conversion with the release of CO2, ethanol, and dioxane as main side products. The combination of microscopic observations, infrared, and absorption spectroscopies with small and wide-angle X-ray scattering experiments unravel a unique growth mechanism implying transient single-walled nanotubes instead of the self-assembly of stacked proto-imogolite tiles. The growth formation of these transient nanotubes is followed at the molecular level by Quick-X-ray absoprtion specotrscopy experiments. Multivariate data analysis evidences that the near neighboring atomic environment of Ge evolves from monotonous to a more complex one as the reaction progresses. The following transformation into a double-walled nanotube takes place at a nearly constant mean radius, as demonstrated by the simulation of X-ray scattering diagrams. Overall, transient nanotubes appear to serve for the anchoring of a new wall, corresponding to a mechanism radically different from that proposed in the literature.

Real-Time Measurements ofOral Mucosal Carbon Dioxide (POMCO2) Reveals an Inverse Correlation With Blood Pressure ina Porcine Model ofCoagulopathic Junctional Hemorrhage.

Shock states that occur during, for example, profound hemorrhage can cause global tissue hypoperfusion leading to organ failure. There is an unmet need for a reliable marker of tissue perfusion during hemorrhage that can be followed longitudinally. Herein, we investigated whether longitudinal POMCO2 tracks changes in hemodynamics in a swine model of coagulopathic uncontrolled junctional hemorrhage. Female Yorkshire-crossbreed swine (n = 7, 68.1 ± 0.7 kg) were anesthetized and instrumented for continuous measurement of mean arterial pressure (MAP). Coagulopathy was induced by the exchange of 50 to 60% of blood volume with 6% Hetastarch over 30 minutes to target a hematocrit of <15%. A 4.5-mm arteriotomy was made in the right common femoral artery with 30 seconds of free bleeding. POMCO2 was continuously measured from baseline through hemodilution, hemorrhage, and a subsequent 3-h intensive care unit period. Rotational thromboelastometry and blood gases were measured. POMCO2 and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, POMCO2 increased because of the uncontrolled hemorrhage by 11.3 ± 3.1 mmHg and was inversely correlated with the drop (17.9 ± 5.9 mmHg) in MAP (Y = -0.4122*X + 2.649, P = .02, r2 = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or POMCO2 (P = .37). Despite the logical appeal of measuring noninvasive tissue CO2 measurement as a surrogate for gastrointestinal perfusion, prior studies have only reported snapshots of this readout. The present investigation shows real-time longitudinal measurement of POMCO2 to confirm that MAP inversely correlates to POMCO2 in the face of coagulopathy. The simplicity of measuring POMCO2 in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.

An Implantable Wireless System for Remote Hemodynamic Monitoring of Heart Failure Patients.

This article presents an implantable wireless system for remote hemodynamic monitoring, which enables direct, continuous (24/7), and simultaneous measurement of pulmonary arterial pressure (PAP) and cross-sectional area (CSA) of the artery. The implantable device, which measures 3.2 mm × 2 mm × 10 mm, comprises a piezoresistive pressure sensor, an ASIC implemented in 180-nm CMOS, a piezoelectric ultrasound (US) transducer, and a nitinol anchoring loop. An energy-efficient pressure monitoring system, which employs duty-cycling and spinning excitation technique, achieves 0.44 mmHg resolution in a pressure range from -135 mmHg to +135 mmHg and consumes 1.1 nJ conversion energy. The artery diameter monitoring system utilizes the inductive characteristic of the implant's anchoring loop and achieves 0.24 mm resolution within a diameter range of 20 mm to 30 mm, four times higher than echocardiography lateral resolution. The wireless US power and data platform enables simultaneous power and data transfer employing a single piezoelectric transducer in the implant. The system is characterized with an 8.5 cm tissue phantom and achieves a US link efficiency of 1.8%. The uplink data is transmitted by using an ASK modulation scheme parallel to the power transfer and achieves a modulation index of 26%. The implantable system is tested in an in-vitro experimental setup, which emulates the arterial blood flow, and accurately detects fast pressure peaks for systolic and diastolic pressure changes at both 1.28 MHz and 1.6 MHz US powering frequencies, with corresponding uplink data rates of 40 kbps and 50 kbps.

Online continuous measurement of arterial pulse pressure and pressure waveform using ultrasound

Noninvasive measurement of local pulse pressure (PP) and blood pressure waveforms, especially in central arteries, is crucial for diagnosing and preventing cardiovascular diseases (CVDs). This work presents an ultrasound system that uses a low-computational method to evaluate local pulse wave velocity (PWV) and diameter waveforms online, enabling continuous and noninvasive measurement of PP and blood pressure waveforms without calibration. The system was validated both in vitro and in vivo, demonstrating high accuracy in PP and blood pressure waveform measurements in cardiovascular phantom experiments. In human carotid experiments, the system was compared to an arterial tonometer, showing excellent accuracy in PP and pressure waveform similarity. Comparative experiments with the volume clamp device further demonstrated the system's ability to accurately trace blood pressure changes induced by deep breathing. Thus, the developed system holds promise for noninvasively measuring arterial PP and blood pressure waveforms continuously, facilitating the diagnosis and prevention of CVDs.

Effect of continuous measurement and adjustment of endotracheal tube cuff pressure on postoperative sore throat in patients undergoing gynecological laparoscopic surgery: study protocol for a randomized controlled trial

BackgroundPostoperative sore throat (POST) is a common postoperative complication after endotracheal tube removal. There are still no effective preventive methods for POST. The aim of this trial is to confirm whether maintaining intraoperative cuff pressure below the tracheal capillary perfusion pressure could effectively reduce the incidence of POST among patients undergoing gynecological laparoscopic surgery.MethodsThis study is a single-center, randomized, parallel-controlled, superiority trial with a 1:1 allocation ratio. Sixty patients whose age is between 18 and 65 years and scheduled for gynecological laparoscopic surgery will be randomized to the cuff pressure measurement and adjustment (CPMA) group and the only cuff pressure measurement without adjustment group (control group). The primary endpoint is the incidence of sore throat at rest within 24 h after extubation. The secondary endpoints include the incidence of cough, the incidence of hoarseness, the incidence of postoperative nausea and vomiting (PONV), POST, and pain intensity within 24 h after extubation. Blocked randomization will be conducted with a computer-generated central randomization online service. The blind method will be applied to subjects, data collectors, outcome evaluators, and statisticians. Outcome assessments will be performed at 0 h and 24 h post-extubation.DiscussionThis randomized controlled study hypothesizes that cuff pressure is the primary influencing factor of POST. By continuous monitoring of endotracheal tube cuff pressure and maintaining it within the range of 18–22 mmHg compared with only continuous measurement without adjustment, it aims to prove that continuous measurement and adjustment of endotracheal tube cuff pressure could be effective in reducing the incidence of POST in gynecological laparoscopic surgery patients. The result of this study could be used as a reference for future multicenter studies to confirm the effect of cuff pressure on POST and provides a scientific theoretical basis for preventing POST to further support comfort medicine.Trial registrationChinese Clinical Trial Registry ChiCTR2200064792. Registered on 18 October 2022. This protocol (version 1.0, 16 March 2022) was approved by the Ethics Committee of Beijing Chaoyang Hospital.

Wireless, multimodal sensors for continuous measurement of pressure, temperature, and hydration of patients in wheelchair

Individuals who are unable to walk independently spend most of the day in a wheelchair. This population is at high risk for developing pressure injuries caused by sitting. However, early diagnosis and prevention of these injuries still remain challenging. Herein, we introduce battery-free, wireless, multimodal sensors and a movable system for continuous measurement of pressure, temperature, and hydration at skin interfaces. The device design includes a crack-activated pressure sensor with nanoscale encapsulations for enhanced sensitivity, a temperature sensor for measuring skin temperature, and a galvanic skin response sensor for measuring skin hydration levels. The movable system enables power harvesting, and data communication to multiple wireless devices mounted at skin-cushion interfaces of wheelchair users over full body coverage. Experimental evaluations and numerical simulations of the devices, together with clinical trials for wheelchair patients, demonstrate the feasibility and stability of the sensor system for preventing pressure injuries caused by sitting.

Prediction of Increased Intracranial Pressure in Traumatic Brain Injury Using Quantitative Electroencephalogram in a Porcine Experimental Model.

Continuous and non-invasive measurement of intracranial pressure (ICP) in traumatic brain injury (TBI) is important to recognize increased ICP (IICP), which can reduce treatment delays. The purpose of this study was to develop an electroencephalogram (EEG)-based prediction model for IICP in a porcine TBI model. Thirty swine were anaesthetized and underwent IICP by inflating a Foley catheter in the intracranial space. Single-channel EEG data were collected every 6 min in 10 mmHg increments in the ICP from baseline to 50 mmHg. We developed EEG-based models to predict the IICP (equal or over 25 mmHg) using four algorithms: logistic regression (LR), naive Bayes (NB), support vector machine (SVM), and random forest (RF). We assessed the performance of each model based on the accuracy, sensitivity, specificity, and AUC values. The accuracy of each prediction model for IICP was 0.773 for SVM, 0.749 for NB, 0.746 for RF, and 0.706 for LR. The AUC of each model was 0.860 for SVM, 0.824 for NB, 0.802 for RF, and 0.748 for LR. We developed a machine learning prediction model for IICP using single-channel EEG signals in a swine TBI experimental model. The SVM model showed good predictive power with the highest AUC value.

Preservation of Right Ventricular Contractility After Transient Phenylephrine‐Induced Pressure Overload in Swine

ObjectiveWe have previously demonstrated that a transient phenylephrine (PE)‐induced rise in systemic arterial blood pressure leads to reversible left ventricular (LV) systolic dysfunction in the absence of ischemia (i.e., “stretch‐induced stunning”). However, the extent to which this phenomenon occurs in the right ventricle (RV) is unclear. Accordingly, the present study was designed to assess changes in pulmonary artery (PA) pressure and RV function during and after systemic administration of PE in swine.MethodsClosed‐chest propofol‐anesthetized swine (n=5) were instrumented with a Swan‐Ganz catheter and an admittance catheter for continuous measurement of PA pressure, RV pressure, and RV volume (ADV500; Transonic SciSense, Inc.). Ventricular end‐diastolic and end‐systolic volumes were assessed by multi‐detector computed tomography with iodinated contrast (1 mL/kg at 4 mL/s) before, during, and 30‐minutes after transient pressure overload elicited by a 1‐hour intravenous infusion of PE (18 mg/hour). Load‐independent RV systolic function was derived from RV pressure‐volume loops collected during inferior vena cava occlusion at baseline and 30 min after PE.ResultsPE elicited a significant rise in PA pressure (27±1/14±1 to 43±1/23±31mmHg; p&lt;0.05) and RV pressure (25±2/3±1 to 44±2/8±2 mmHg; p&lt;0.05) that normalized 30‐minutes after the end of the infusion period (PA: 28±1/11±1 mmHg; RV: 29±5/4±2 mmHg). This was accompanied by a significant increase in RV end‐diastolic and end‐systolic volumes and decrease in RV ejection fraction that tended to persist 30‐minutes after cessation of PE (Table; top panel). However, load‐dependent (dP/dtmax) and load‐independent (ESPVR and PRSW) parameters of RV systolic function were preserved after PE‐induced TPO (Table; bottom panel).ConclusionsDespite causing a significant rise in RV preload volume and pressure, transient PE‐induced pressure overload is not associated with RV contractile dysfunction during the post‐infusion period. The absence of stretch‐induced stunning in the RV may be linked to inherent differences in compliance relative to the LV as well as a diminished pressor response to PE in the pulmonary vs. systemic circulation.

Preliminary experience with continuous right ventricular pressure and transesophageal echocardiography monitoring in orthotopic liver transplantation.

BackgroundDespite increasing attention in the cardiac anesthesiology literature, continuous measurement of right ventricular pressure using a pulmonary artery catheter has not been described in orthotopic liver transplantation, despite similarities in the anesthetic approach to the two populations. We describe our preliminary experience with this technique in orthotopic liver transplantation, and by combining various derived measures with trans-esophageal echocardiography, make some early observations regarding the response of these measures of right ventricular function during the procedure.MethodsIn this case series, ten patients (five men and five women) undergoing orthotopic liver transplantation in our institution had their surgeries performed while monitored with a pulmonary artery catheter with continuous right ventricular port transduction and trans-esophageal echocardiography. We recorded various right ventricular waveform (early-to-end diastolic pressure difference, right ventricular outflow tract gradient, right ventricular dP/dT and right ventricular end-diastolic pressure) and echocardiographic (right ventricular fractional area change, tricuspid annular plane systolic excursion, right ventricular lateral wall strain) and described their change relative to baseline at timepoints five minutes before and after portal vein reperfusion, immediately after hepatic artery reperfusion and on abdominal closure.ResultsExcept for tricuspid annular plane systolic excursion at five minutes prior to reperfusion (mean −0.8 cm; 95% CI−1.4, –0.3; p = 0.007), no echocardiographic metric was statistically significantly different at any timepoint relative to baseline. In contrast, changes in right ventricular outflow tract gradient and right ventricular dP/dt were highly significant at multiple timepoints, generally peaking immediately before or after reperfusion before reducing, but not returning to baseline in the neohepatic phase. Nine of 10 participants in this series demonstrated a degree of dynamic right ventricular outflow tract obstruction, which met criteria for hemodynamic significance (> 25 mmHg) in two participants. These changes were not materially affected by cardiac index.ConclusionsDynamic right ventricular outflow tract obstruction of varying severity appears common in patients undergoing orthotopic liver transplantation. These results are hypothesis generating and will form the basis of future prospective research.

Feasibility of Transcutaneous Method for Carbon Dioxide Monitoring in an Intensive Care Unit

Background: Transcutaneous partial pressure of carbon dioxide (PtCO2) monitorization provides a continuous and non-invasive measurement of partial pressure of carbon dioxide (pCO2). In addition, peripheral oxygen saturation (SpO2) can also be measured and followed by this method. However, data regarding the correlation between PtCO2 and arterial pCO2 (PaCO2) measurements acquired from peripheric arterial blood gas is controversial. Objective: We aimed to determine the reliability of PtCO2 with PaCO2 based on its advantages, like non-invasiveness and continuous applicability. Methods: Thirty-five adult patients with hypercapnic respiratory failure admitted to our tertiary medical intensive care unit (ICU) were included. Then we compared PtCO2 and PaCO2 and both SpO2 measurements simultaneously. Thirty measurements from the deltoid zone and 26 measurements from the cheek zone were applied. Results: PtCO2 could not be measured from the deltoid region in 5 (14%) patients. SpO2 and pulse rate could not be detected at 8 (26.7%) of the deltoid zone measurements. Correlation coefficients between PtCO2 and PaCO2 from deltoid and the cheek region were r: 0,915 and r: 0,946 (p = 0,0001). In comparison with the Bland-Altman test, difference in deltoid measurements was -1,38 ± 1,18 mmHg (p = 0.252) and in cheek measurements it was -5,12 ± 0,92 mmHg (p = 0,0001). There was no statistically significant difference between SpO2 measurements in each region. Conclusion: Our results suggest that PtCO2 and SpO2 measurements from the deltoid region are reliable compared to the arterial blood gas analysis in hypercapnic ICU patients. More randomized controlled studies investigating the effects of different measurement areas, hemodynamic parameters, and hemoglobin levels are needed.

Blood Pressure Estimation from Photoplethysmography with Motion Artifacts Using Long Short Term Memory Network

Continuous measurement of the Blood Pressure (BP) is important in hypertensive patientsand elderly population. Traditional cuff based methods are difficult to use since it is uncomfortable towear a cuff throughout the day. A more suitable method is to estimate the BP using the Photoplethysmography(PPG) signal. However, it is difficult to estimate a BP when the PPG is corrupted withMotion Artifacts (MAs). In this paper, Long Short Term Memory (LSTM) an extension of RecurrentNeural Networks (RNN) is used used to improve the accuracy of the estimation of the BP from thecorrupted PPG. It shows that an accuracy of 97.86 is achieved.

Characterising the dynamics of cerebral metabolic dysfunction following traumatic brain injury: A microdialysis study in 619 patients.

Traumatic brain injury (TBI) is a major cause of death and disability, particularly amongst young people. Current intensive care management of TBI patients is targeted at maintaining normal brain physiology and preventing secondary injury. Microdialysis is an invasive monitor that permits real-time assessment of derangements in cerebral metabolism and responses to treatment. We examined the prognostic value of microdialysis parameters, and the inter-relationships with other neuromonitoring modalities to identify interventions that improve metabolism. This was an analysis of prospective data in 619 adult TBI patients requiring intensive care treatment and invasive neuromonitoring at a tertiary UK neurosciences unit. Patients had continuous measurement of intracranial pressure (ICP), arterial blood pressure (ABP), brain tissue oxygenation (PbtO2), and cerebral metabolism and were managed according to a standardized therapeutic protocol. Microdialysate was assayed hourly for metabolites including glucose, pyruvate, and lactate. Cerebral perfusion pressure (CPP) and cerebral autoregulation (PRx) were derived from the ICP and ABP. Outcome was assessed with the Glasgow Outcome Score (GOS) at 6 months. Relationships between monitoring variables was examined with generalized additive mixed models (GAMM). Lactate/Pyruvate Ratio (LPR) over the first 3 to 7 days following injury was elevated amongst patients with poor outcome and was an independent predictor of ordinal GOS (p<0.05). Significant non-linear associations were observed between LPR and cerebral glucose, CPP, and PRx (p<0.001 to p<0.05). GAMM models suggested improved cerebral metabolism (i.e. reduced LPR with CPP >70mmHg, PRx <0.1, PbtO2 >18mmHg, and brain glucose >1mM. Deranged cerebral metabolism is an important determinant of patient outcome following TBI. Variations in cerebral perfusion, oxygenation and glucose supply are associated with changes in cerebral LPR and suggest therapeutic interventions to improve cerebral metabolism. Future prospective studies are required to determine the efficacy of these strategies.

Tonometric Condition of Cellular Polypropylene Film Sensors in Measuring Arterial Pressure Waveform.

Tonometric continuous measurement of arterial pressure becomes feasible using a cellular polypropylene (Cellular PP) film sensor. A pulsatile arterial vascular phantom model was used to find the range of optimal tonometric conditions and the responsiveness to dynamic pressure changes. The optimal tonometric condition was assessed by the correlation coefficient between the hydraulic pressure and the Cellular PP output using two different types of tubes (the latex tube and the hydrogel tube) to simulate arteries. With a setting of the normal blood pressure range, the output of Cellular PP correlated strongly with the level of hydraulic pressure, 0.998 and 0.989 in the latex tube and the hydrogel tube, respectively. For maintaining the optimal tonometric condition, the depressed depths of the latex and the hydrogel tube were less than 1.2 and 0.6 mm, respectively. The phantom model also demonstrated that the Cellular PP sensor followed changes in a hydraulic pressure dynamically under the optimal tonometric conditions. The present results demonstrated the Cellular PP film sensor is applicable to the arterial tonometry in measuring the instantaneous blood pressure while the sensor is adjusted to maintain the minimal flatness of the underlying arterial wall.Clinical Relevance- To understand the physiological characteristics of blood pressure and arterial system, the instantaneous measurement of blood pressure is necessary. The present study suggests that Cellular PP films are applicable to peripheral arteries tonometrically to obtain simultaneously the respective blood pressure waveforms.

Examination of the frequency of upward and downward fluctuations in the pressure obtained from the cuff pressure-time curve by continuous measurement of endotracheal tube cuff pressure during thyroid surgery: a case series

BackgroundFew studies examined time-to-time changes of cuff pressure of an endotracheal tube during surgery. We retrospectively analyzed the changes of cuff pressure during thyroid surgery and examined its relationships with postoperative airway complications.Case presentationCuff pressure was initially adjusted at 26 cmH2O and continuously measured in 61 patients. The cuff pressure-time curve dynamically fluctuated, and exceeded 30 cmH2O in all patients, whereas decreased to ≤ 20 cmH20 in 42 (69%) patients. Ratio of the period with such an increase and decrease of cuff pressure to the total duration of surgery were 40% (28–66%) and 9% (0–21%), respectively (median, interquartile range). No patients showed symptoms of airway stenosis requiring treatment except one who developed recurrent laryngeal nerve palsy. No patients had lower respiratory tract infection.ConclusionsCuff pressure dynamically fluctuated during thyroid surgery. Preventing an increase as well as decrease of cuff pressure is required.

Minimally invasive measurement of orbital compartment pressure and implications for orbital compartment syndrome: a pilot study.

Diagnosis of orbital compartment syndrome is mainly based on clinical findings, such as intraocular pressure and proptosis, which try to estimate the orbital compartment pressure. However, the reliability of these surrogates is unclear. Current techniques for the direct measurement of orbital compartment pressure are widely experimental and impractical in the clinical setting. Our aim was to explore the feasibility of minimally invasive needle manometry for direct measurement of orbital compartment pressure under reproducible conditions in an in vivo model of orbital congestion. We further sought to evaluate intraocular pressure and proptosis as indicators for elevated orbital compartment pressure. A total of 7 ml of mepivacaine 2% solution was injected into the orbital compartment in 20 patients undergoing cataract surgery under local anesthesia. A commercially available single-use manometer device was inserted between the syringe and the injection needle to measure the orbital compartment pressure for each milliliter of intraorbital volume increment. Additionally, intraocular pressure (subgroup A; n = 10) or axial globe position (subgroup B; n = 10) were measured. Needle manometry allowed for rapid and continuous measurement of orbital compartment pressure. Overall mean orbital compartment pressure increased from 2.5 mmHg pre- to 12.8 mmHg post-interventionally. Both, intraocular pressure (Spearman's correlation coefficient rs = 0.637, p < 0.0001) and proptosis (rs = 0.675, p < 0.0001) correlated strongly with the orbital compartment pressure. Needle manometry appears to be a feasible minimally invasive instrument to directly measure orbital compartment pressure, showing promises for a more routine application in managing orbital compartment syndrome. The results further suggest that both elevated intraocular pressure and proptosis are valuable indicators for orbital compartment syndrome.

Convection Influence on Redox Potential Measurements at Hot Platinum Electrodes

Introduction The equilibrium of redox reactions between H2O and H2, CO and CO2 or water gas can be determined potentiometrically at high temperatures with a solid electrolyte cell (SEC) by establishing defined partial pressures of both partners of the redox couples according to Nernst equation [1]. The dependency of the potential on temperature allows to calculate thermodynamic parameters of the reaction from the equilibrium constant K p. The thermodynamic relations reveal that the measured cell voltage depends on partial pressures of the redox active gas components, cell temperature and the oxygen partial pressure in the reference gas.In this work, the results of experimental studies on the impact of gas convection on the equilibrium potential are presented and possible reasons for this behavior are discussed. Experimental The experimental setup is given schematically in Fig. 1. The flow rate of the redox gas is adjusted between 0 and 50 standard cm³ (sccm) by MFC. The purpose-built humidifier for establishing a constant water vapor partial pressure consists of six horizontally positioned glass tubes of around 10 cm length and 3 cm diameter sequentially connected with each other. The tubes are half filled with distilled and sterilized water and thermostated to 22.00 ± 0.01 K in a stirred water bath. The test gas pass the tubes in a laminar flow above the water filling and is saturated with water vapor avoiding aerosol formation. A downstream capacitive dew point sensor was used to verify the accuracy of the humidification.Over a wide temperature and concentration range, the water vapor dissociation is negligible so that the H2/H2O ratio set at room temperature remains practically unchanged in the heated solid electrolyte cell [2].Different self-developed and commercial YSZ cells equipped with Pt electrodes of different morphologies were investigated by measuring redox potentials in H2/H2O and CO/CO2 mixtures with various dilution. The oxygen partial pressure of the reference gas air was monitored by continuous measurement of dew point and total pressure. Results The redox equilibrium in H2/H2O mixtures is established at catalytically highly active Pt electrodes in YSZ cells already at relatively low temperatures below 600 °C [3]. In Figure 2a the course of the cell voltage measured in such a mixture is given for different temperatures. At the adjusted H2/H2O partial pressure ratio near 1 and absolute values of component partial pressures around 3000 Pa, small oxygen leakages will not influence the measured potential [2]. The most influencing deviations on the measured voltages are related to temperature measurement and control of the YSZ cell. These are assumed to be responsible mainly for the noise visible in the curve in Fig. 2a. The systematic deviation known from thermocouple application probably causes the small difference of the measured cell voltage from values, which are expected from thermodynamic data (NIST). If the complete voltage difference Δ in Fig 2b is attributed to temperature deviation of the used thermocouple (type B), this parameter amounts to around 11 K higher than it is indicated by the set point value of the controller.Other sources of deviations can arise from asymmetric potentials of the YSZ cell resulting in measurable voltages at equal oxygen partial pressures on both sides of the cell. In order to obtain indications of such deviations, the flow rate and the dilution of the redox mixtures were varied. The curves in Fig. 3 show that especially the flow rate has surprisingly high influence on the cell voltage. After switching off the gas flow the cell voltage decreases abruptly to values 6-10 mV lower than measured in the constant gas flow. The following drift continues this decrease. Immediately after switching on the flow, the cell voltage jumps back to values before switch-off. At flow rates below 10 sccm, this switch-off shift decreases significantly. At all investigated cells, the switch-off shift increases with decreasing dilution of the redox mixture and increasing temperature, reaching its maximum in pure H2/H2O mixtures at the investigated temperature maximum.In the contribution, the signal influencing processes like gas flow cooling of the electrode, flow induced pressure increase, convective diffusion in pores and oxygen exchange between electrode/electrolyte and gas [4] will be discussed and different scenarios will be compared.Literature R. Hartung, H.-H. Möbius, Potentiometrische Bestimmung des Wasserdampf Dissoziationsgleichgewichtes zwischen 1000 und 1300 K mit einer Festelektrolytzelle, Chemie Ingenieur Technik 40 (12), 592–600 (1968); DOI: 10.1002/cite.330401209.H.-H. Möbius, Solid-state electrochemical potentiometric sensors for gas analysis, In: Göpel, W. Hesse, J. Zemel, J.N.: Sensors. A Comprehensive Survey, Volume 3: Chemical and Biochemical Sensors Part II. Weinheim, New York: VCH-Wiley, 1104–1154 (1995).R. Hartung, H.-H. Möbius, Zur unteren Begrenzung der Arbeitstemperatur galvanischer Sauerstoff-Meßzellen mit Zirconiumdioxid-Festelektrolyten Z. Chem. 9, 197-198 (1969).M. Schelter, J. Zosel, V. Vashook, U. Guth, M. Mertig, Electrolyte related parameters of coulometric solid state devices, Solid State Ionics 288, S. 266–270 (2016); DOI: 10.1016/j.ssi.2016.01.020. Figure 1

Velocity-pressure loops can estimate intrinsic and pharmacologically induced changes in cardiac afterload during non-cardiac surgery. An observational study.

Continuous measurement of aortic pressure and aortic flow velocity signals in the operating theatre allows us to draw velocity-pressure (Vel-Pre) loops. The global afterload angle (GALA), derived from the Vel-Pre loops, has been linked to cardiac afterload indicators. As age is the major determinant of constitutive arterial stiffness, we aimed to describe (1) the evolution of the GALA according to age in a large cohort of anesthetized patients and (2) GALA variations induced by haemodynamic interventions. We included patients for whom continuous monitoring of arterial pressure and cardiac output were indicated. Fluid challenges or vasopressors were administered to treat intra-operative hypotension. The primary endpoint was the comparison of the GALA values between young and old patients. The secondary endpoint was the difference in the GALA values before and after haemodynamic interventions. We included 133 anaesthetized patients: 66 old and 67 young patients. At baseline, the GALA was higher in the old patients than in young patients (38 ± 6 vs. 25 ± 4 degrees; p < 0.001). The GALA was positively associated with age (p < 0.001), but the mean arterial pressure (MAP) and cardiac output were not. The GALA did not change after volume expansion, regardless of the fluid response, but it did increase after vasopressor administration. Furthermore, while a vasopressor bolus led to a similar increase in MAP, phenylephrine induced a more substantial increase in the GALA than noradrenaline (+ 12 ± 5° vs. + 8 ± 5°; p = 0.01). In non-cardiac surgery, the GALA seems to be associated with both intrinsic rigidity (reflected by age) and pharmacologically induced vasoconstriction changes (by vasopressors). In addition, the GALA can discriminate the differential effects of phenylephrine and noradrenaline. These results should be confirmed in a prospective, ideally randomized, trial.

Application of a continuous pressure metric for Australian football

ABSTRACT Pressure is an important constraint on sports performance and is typically measured through manual notational analysis. A continuous representation of pressure, along with semi-automated measurement, would serve to improve the efficiency of practice design and analysis, as well as provide additional context to player competition performance. Using spatiotemporal data collected from wearable tracking devices, the present study applied Kernel Density Estimation to estimate the density of players, relative to the ball carrier, at point of skill execution during elite Australian Football training. Two environmental constraints were measured (area per player and number of players) to determine the relationship between these training design manipulations and density. Density was also compared with existing notational analysis measurements of pressure. Results indicated that a higher density on skills was associated with successful skill executions. The opposite relationship was found between notational analysis pressure measurement and skill effectiveness. A strong inverse relationship was found between environmental constraint manipulation and density, whereby increasing field size and playing number decreased the density on skill involvements. The findings offer insight into the continuous measurement of pressure and encourage practitioners to utilize training design manipulations to influence density as a constraint on skills.