Fick Principle Research Articles

Cardiac output estimation based on arterial and venous blood gas analysis: proposal of amonitoring method.

Hemodynamic optimization is vital in high risk surgical patients or in high risk surgical procedures. The main objective of hemodynamic management is to maintain tissue perfusion and preserve aerobic metabolism through acardiac output coupled with the metabolic demand. The technologies used for cardiac output monitoring use special techniques (e.g. lithium dilution or transpulmonary thermodilution) or implementation of dedicated devices with considerable rates of potential complications (pulmonary artery catheter). Thus, we propose anovel method to estimate cardiac output through the analysis of arteriovenous blood gases which could be an alternative to more expensive methods (minimally invasive devices, pulmonary artery catheter). Areview of several formulas described in the literature to compute the variables needed to calculate cardiac output with the Fick principle was carried out. These formulas estimate the oxygen consumption using the O2 sensor integrated in the anesthesia workstation. The other variables in the Fick equation are derived from the arterial and venous blood gas analysis and parameters obtained from mechanical ventilators. By integrating the data gathered from the publications found, the authors created acomprehensive formula for calculation of cardiac output and the cardiac index using the parameters obtained from blood gas analysis. The presented method provides amore accessible and affordable way to monitor cardiac output in surgical high-risk patients in an environment with limited resources.

Preservation of Aloe vera and soybean flour fortified Granny Smith apple through optimised quartz–halogen radiated vacuum drying: kinetics and quality evaluation

Granny Smith (GS) apple has low protein content and poor antimicrobial properties; hence it has been blended with Aloe vera (AV; high ascorbic acid, antimicrobial and antioxidant properties) and soybean flour (SF; rich in phenols, flavonoids, ascorbic acid, total antioxidant and protein) in different proportions to obtain fortified GS, i.e. GSAVSF. Moreover, GS being a perishable fruit, its moisture content should be reduced to enhance shelf life. Accordingly, this GSAVSF was osmotically pre-dehydrated and finally dried through energy-efficient quartz-halogen radiation (QHR) assisted vacuum-drying (QHRVD) to produce dried GSAVSF i.e. (DGSAVSF) under optimized conditions. The optimally dehydrated DGSAVSF product resulted in minimum moisture (4.85% w/w) and maximum protein (6.24 g kg-1 ) content. The application of osmotic dehydration and QHRVD afforded acceptable colour of DGSAVSF compared to GSAVSF (ΔEI * = 10.07 ± 0.21). A parametric drying model was formulated that corroborated well with Fick's equation. QHRVD rendered high moisture diffusivity (1.49 × 10-8 m2 s-1 ) and low activation energy (27.64 kJ mol-1 K-1 ). Appreciable quality improvements with respect to fresh GS concerning ascorbic acid (176.05%), total phenolic (579.07%), total flavonoid (333.33%) contents and 2,2'-diphenyl-1-picrylhydrazyl radical scavenging activity (446.71%) could be achieved. The product demonstrated satisfactory shelf life (1 × 104 CFU g-1 : aerobic mesophilic; 1 × 104 CFU g-1 : mould and yeast) and high rehydration ratio (4.25 ± 0.1). The enrichment of GS with AV and SF along with optimal drying protocols could provide a quality fortified DGSAVSF through an energy-proficient sustainable process. The highly nutritious product with suitable colour, microbial stability and rehydration ratio also satisfied a 9-point hedonic scale, thus confirming consumer acceptability. © 2020 Society of Chemical Industry.

NITROGENING HYDRAULIC CYLINDER RODS

The paper considers the method of ion-plasma nitriding of polished rods of hydraulic cylinders. With ion nitriding, the surface hardening of parts is most pronounced. This is due to the fact that the surface layer of the part does not exceed 20 nm, that is, it is a nanostructure. In this nanostructure, nitrogen diffusion processes are significantly different from bulk ones. The size effects in the nanostructure lead to the fact that the “classical” Fick equations do not work in the layer, and the diffusion of nitrogen in this layer depends logarithmically on the properties of the steel. It was theoretically found that diffusion in a nanoplate depends both on the material of the plate through the diffusion coefficient of the bulk sample D0 and on the size factor α. In the classical case, there is no such dependence.

152 Impact of chorionic somatomammotropin RNA interference on uterine blood flow and placental glucose uptake in the absence of intrauterine growth restriction

Abstract Chorionic somatomammotropin (CSH) is one of the most abundant hormones produced by the sheep placenta, yet the exact function of CSH has been elusive. Previously we reported the use of in vivo RNA interference (RNAi) to assess the impact of CSH deficiency on placental and fetal growth in sheep. Near-term (135 dGA), there are two distinct CSH RNAi phenotypes: 1) pregnancies with intrauterine growth restriction (IUGR), and 2) pregnancies with normal fetal and placental weights. This study describes physiological changes in the latter phenotype. To generate the CSH RNAi pregnancies, the trophectoderm of hatched blastocysts (9 dGA) were infected with lentiviral-constructs expressing either a scrambled control (NTS) or CSH-specific shRNA (CSH RNAi), prior to transfer into synchronized recipient ewes. At 120 dGA, 6 NTS and 6 CSH RNAi pregnancies were fitted with maternal and fetal catheters. Uterine and umbilical blood flows were measured utilizing the 3H2O transplacental diffusion technique at 132 dGA, and nutrient uptakes were calculated by the Fick principle. Resulting data were analyzed by Student’s t-test and significance was set at P ≤ 0.05. CSH RNAi tended (P ≤ 0.10) to reduce placentome weight with no effect on fetal weight. Absolute (ml/min) and relative (ml/min/kg fetus) uterine blood flows were reduced (P ≤ 0.05) in CSH RNAi pregnancies, but umbilical flows were not impacted. The uterine artery-to-vein glucose gradient (mmol/l) was significantly (P ≤ 0.05) increased, whereas the gradients for taurine and glycine were reduced (P ≤ 0.05). Uteroplacental glucose uptake (mmol/min/kg placenta) was increased 27% (P ≤ 0.05), whereas umbilical glucose uptake (mmol/min/kg fetus) was reduced 13%. This cohort demonstrates that even in the absence of IUGR, CSH deficiency has significant physiological ramifications, and the investigation of CSH RNAi pregnancies exhibiting both IUGR and non-IUGR phenotypes may help determine the direct effects of CSH and its potential impact on fetal programming. Supported by NIH R01 HD093701.

The modified Fick principle in the management of patients with a single ventricle

Structural and functional cardiovascular abnormalities associated with single ventricle physiology are particularly challenging in terms of perioperative management. The modified Fick principle is considered to be one of the most effective tools for evaluating a patient’s clinical status as well as the parameters of respiratory and hemodynamic support.

Abstract 14433: High Intensity Exercise Training Safely Increases Cardiorespiratory Fitness in Patients With Hypertrophic Cardiomyopathy

Introduction: Patients with hypertrophic cardiomyopathy (HCM) are excluded from high intensity activities due to perceived fear of sudden cardiac death. Observational data from athletes with HCM suggest that engaging in high intensity exercise (HIE) may be safe and is associated with higher cardiorespiratory fitness. Whether HIE can safely elicit a superior increase in fitness compared to moderate intensity exercise in patients with HCM is unclear. Methods: Nine HCM patients (49 ± 7 years, 3 female) were assessed for maximal oxygen uptake (VO 2 max, Douglas Bag method), cardiac output (Q c , acetylene rebreathing), and peripheral oxygen extraction (av-O 2 diff, Fick equation) before randomization and after 5 months of MIE or HIE training. Patients completed 3-4 sessions of MIE each week, while the HIE group also incorporated 1-2 supervised high intensity interval training sessions/week from month 3 onwards. Arrhythmias were monitored via pre-existing implantable cardiac defibrillators or implantable loop recorders placed prior to training. Results: Five months of MIE increased absolute VO 2 max by 3% and relative VO 2 max by 4%, while HIE consistently increased absolute VO 2 max by 6% and relative VO 2 max by 5% (Figure). Maximal Q c did not change after MIE but increased in all HIE patients (+1.2L/min, 95% CI -1.4 to 3.9), while maximal av-O 2 diff remained stable in both groups. Training compliance was 84 ± 15% in HIE and 93 ± 11% in MIE. There were no serious exercise-related adverse events in either group though two HIE subjects had arrhythmias at rest: 1) 14-beat run of wide complex tachycardia of uncertain mechanism given underlying conduction disease prior to a training session, and 2) 11 beats of non-sustained ventricular tachycardia prior to post exercise testing. Conclusions: Preliminary findings show that five months of HIE safely and consistently increased cardiorespiratory fitness in patients with HCM, though overall the improvements were comparable to MIE.

Influence of different temperatures on brining kinetics, salt concentration and texture properties of Chinese cabbage (Brassica rapa L. ssp. pekinensis) during brining with ultrasonic treatment.

The effects of ultrasound treatment at different temperatures (4, 10, and 25 ℃) on the brining process of Chinese cabbage were investigated based on their salt diffusion coefficients and texture profiles. Salt weight increased significantly, but water weight decreased in Chinese cabbage treated with ultrasound at increasing temperatures. According to Fick's second equation, the effective diffusion coefficient of Chinese cabbage showed a notable increase as temperature was increased. High temperature caused unfavorable texture properties, and among these, hardness showed the most significant decrease when brining temperature was set at 25 °C. Consequently, results from the texture profile analysis and brining kinetics modeling suggest that optimal brining conditions could be achieved at 10 °C. At this temperature, the diffusion coefficient of Chinese cabbage is higher, the brining time is reduced, and the preferred qualities of kimchi are preserved. PRACTICAL APPLICATION: Ultrasonication is an effective technology that can be utilized in kimchi manufacturing. It presents the advantage of reducing brining time while maintaining the acceptable textural properties of kimchi. This study investigated the impact of different temperatures on the texture properties and brining times of Chinese cabbage during brining and reveal a practical application worthy of further study in food industries and provide valuable information for improving the quality of kimchi.

Prediction of Service Life in Concrete Structures based on Diffusion Model in a Marine Environment Using Mesh Free, FEM and FDM Approaches

Chloride-induced corrosion is a key factor in the premature corrosion of concrete structures exposed to a marine environment. Fick's second law of diffusion is the dominant equation to model diffusion of chloride ions. This equation is traditionally solved by Finite Element Method (FEM) and Finite Difference Method (FDM). Although these methods are robust and efficient, they may face some numerical issues due to discretization process. This study solves the Fick's equation using the Element-Free Galerkin (EFG) method as well as traditional FEM and FDM. The results of these numerical methods are compared together, and validated with the analytical solution in special cases. The results show that the EFG method predicts the service life of the concrete structures, more accurately than the other methods, and exhibits the lowest displacement error and energy error for a constant diffusion coefficient problem. FDM can be performed very efficiently for simple models, and the displacement errors produced by this method do not differ considerably from the EFG results. Therefore, FDM could compete with the EFG method in simple geometries. FEM can be used with a sufficient number of elements while the convergence of the results should be controlled. However, in complicated models, FEM and especially the EFG method are much more flexible than FDM.

Pulmonary vascular resistance and pulmonary artery compliance in a large cohort of patients with sinus venosus septal defect

Abstract Background Left-to-right shunt in patients with sinus venosus septal defect (SVSD) may affect resistive (pulmonary vascular resistance – PVR) and elastic (pulmonary artery compliance-PAC) properties of the pulmonary arteries. This study aimed at evaluating (1) changes in hemodynamics over time and (2) the relationship between PVR and PAC in a large cohort of patients with SVSD. Methods Data of 136 patients with SVSD (median age at diagnosis 14 (IQR 5–48) years, 47% male) were included. Catheterization data was available in 87 patients. Pressures were measured and cardiac output evaluated using the Fick principle. PVR (mean pulmonary artery pressure (mPAP)-wedge pressure/cardiac output) and PAC (stroke volume/pulse pressure) were calculated and indexed for body surface area. Results Ninety percent had abnormal pulmonary venous connection. Median shunt ratio was 2.5 (IQR 2.0–2.9). Repair was performed in 128 (94%) at a median age of 13 (IQR 5–43) years. During a median follow-up time of 31 (IQR 17–55) years, 12 (9%) patients died, 13 (10%) developed heart failure, 19 (14%) atrial arrhythmia, 6 (4%) sick sinus syndrome and 7 (5%) required pacemaker implantation. PVR indexed and PAC indexed was 3.5 (IQR 2.4–7.5) WU·m2 and 1.8 (IQR 1.3–2.5) mL/mmHg·m2. There was an inverse, hyperbolic relationship between PVR and PAC with an RC time of 6.6 (IQR 4.4–8.9) sec. When comparing patients with age at catheterization <10 years, 10–50 years and >50 years, shunt ratio (2.5±0.6 vs 2.5±0.8 vs 2.5±0.6; p=0.836) and PVR indexed (2.9 (2.3–3.4) vs 3.1 (2.0–9.0) vs 6.6 (3.6–8.8) WU·m2; p=0.132) were not statistically different, whereas mPAP (19 (16–22) vs 21 (16–24) vs 28 (22–34) mmHg; p=0.002); wedge (6 (4–8) vs 13 (8–16)vs 14 (10–19) mmHg; p<0.0001) and PAC indexed (2.2 (1.5–2.9) vs 2.0 (1.4–2.8) vs 1.3 (0.9–1.7) mL/mmHg·m2; p=0.002) differed significantly. Conclusion SVSD is associated with late morbidity and mortality. In SVSD, PVR and PAC are inversely related. Over time, the changes in elastic resistance (PAC or pulsatile load) are more profound than changes in resistive (PVR – steady load). Figure 1 Funding Acknowledgement Type of funding source: None

Increased oxygen uptake and utilization in the peripheral muscles, rather than cardiac function reserve, may be determinants of increased peak VO2 by cardiac rehabilitation in heart failure

Abstract Background Peak oxygen consumption (peak VO2) is a major prognostic parameter in heart failure (HF). Previous studies have shown a relationship between peak VO2 and impaired oxygen uptake and utilization in the peripheral muscles. The purpose of this study was to clarify the determinant of increased peak VO2 by cardiac rehabilitation (CR) in patients with HF. Methods We performed echocardiography during upright ramp bicycle cardiopulmonary exercise test in 30 HF patients (61±1 years of age, 80% male) before and 6 months after CR. HR reserve was determined as the change in HR from rest to peak exercise, expressed as a percentage of the predicted maximal HR reserve. Elastance index (EAI) and LV end-systolic elastance index (ELVI) were derived as the ratio of end-systolic pressure to stroke volume index and end-systolic volume index, respectively. End-systolic pressure was estimated from the equation 0.9 × brachial systolic blood pressure. Ventriculo-arterial coupling (VAC) was calculated as the quotient of EAI and ELVI. The ratio of LDEDVI to E/e' mean was used to evaluate LV diastolic compliance. Systemic vascular resistance index was calculated as mean arterial pressure divided by echocardiography calculated cardiac index and multiplied by 80. The arterial venous oxygen content difference (C (A-V) O2 gradient) was calculated by using the Fick equation as: VO2/echocardiography calculated cardiac output. Results Peak VO2 and C (A-V) O2 gradient were increased by CR. However, heart rate reserve, systolic reserve, VAC, diastolic reserve and vasodilation reserve were unchanged by CR (Table 1). Conclusions Increased oxygen uptake and utilization in the peripheral muscles, rather than cardiac function reserve, may be determinants of increased peak VO2 by CR in HF. Table 1 Funding Acknowledgement Type of funding source: None

Pulmonary arterial hypertension modeling with synthetic stable thromboxane A2 analogue (U46619) in porcine: dose adjustment and acute hemodynamic reactions

Abstract Introduction Survival in PAH is strongly associated with adaptation of the RV to pressure overload. Purpose To investigate acute hemodynamic reactions during infusion of the stable thromboxane A2 (TXA2) analogue U46619 in a porcine model. Materials and methods The study comprised 9 male Landrace pigs (32.7±3.8 kg) under GA. After heparinization, PAH was induced by continuous and stepwise increasing infusion of U46619 (10 mg/ml; Tocris, USA) according to a pre-specified protocol. The target mPAP was 40 mmHg. Hemodynamics was assessed, cardiac output (CO) was calculated using the Fick equation before and during U46619 infusion. Results U46619 infusion at a previously published rate 0.1, 0.2 μg kg–1 min–1 in pig 1 resulted in rapid hemodynamic deterioration. Two-time reduced U46619 dose infusione resulted in a target mPAP but severe mBP drop in 1, 3, 4 pigs and required cathecholamine support. The U46619 dosage was reduced up to ¼ (0.025, 0.05, 0.075, 0.1, 0.12, 0.15, 0.175 μg kg–1 min–1). In animals on 1/4 dosage U46619 infusion, heart rate (HR), mBP, mPAP, RAP and PVR reliably increased and BP was stable (Table 1). There was a positive correlation between the mPAP and heart rate (HR) on U46619 infusion (r=0.66; t=2.38; p=0.048) and between CO and mBP (r=0.66; t=2.36; p=0.04). Low CO was associated with high PVR (r=−0.98; t=−14.3; p<0,001). Positive correlation between PVR and SVR was revealed (r=0.96; p=0.00002). In 3 pigs with severe mBP drop and PAH right ventricle subendocardial hemorrhage was revealed on autopsy study. Conclusions High dose U46619 infusion was associated with acute RV decompensation due to pressure overload accompanied with systemic BP drop and low CO. Lower dosages of U46619 infusion were characterized by stable target mean PAP. HR acceleration and mean systemic BP are of compensation mechanisms for cardiac output maintenance in PAH. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): RFBR grant 18-315-20050

Evaluation of hydrogen permeation characteristics in rubbery polymers

To find suitable sealing material with low permeability against hydrogen, the elaborated evaluation techniques for hydrogen transport properties are necessary. We developed two techniques determining the permeability of hydrogen including software for diffusion behavior analysis. The techniques contain gas chromatography and volumetric collection of hydrogen gas. By measuring the hydrogen released from polymer samples with respect to the elapsed time after being decompressed from the high pressure, total amount of adsorption and diffusivity (D) of hydrogen are evaluated with self-developed program of Fick's diffusion equation specified to a sample shape. The solubility (S) and permeability (P) of the polymers are determined through Henry's law and a relation ofP=SD, respectively. Developed techniques were applied to three kinds of spherical-shaped sealing rubbers, NBR, EPDM, and FKM. The D, S and P have been measured as function of pressure. The permeability obtained by both methods are discussed with Comsol simulation.

Heat and mass transport analysis of the drying of freshwater fishes by a forced convective air‐dryer

AbstractThe drying behavior of different freshwater fishes (with/without scales) is investigated using a simple convective heated air dryer. Drying processes are analyzed to study the kinetics of drying, shrinkage dependent variable effective diffusivity, convective heat and mass transport, and the energy aspect of drying. Among the drying kinetic models, Hasibuan–Daud and Haghi–Angiz‐I models produce the best fit for fishes with scales and Hii model produces the best fit for fish without scales. Diffusion analysis performed based on simplified solution of Fick's diffusion equation shows higher effective diffusivity for fish without scales, proving additional barrier from scales (for fish with scales) that need to be considered during dryer design. Calculated instantaneous heat and mass transfer coefficients (different for fish with or without scales) also agree with this observation, accentuating the difference based on scales. Drying process for all fishes obeys the heat‐mass transfer correlation. Estimated parameters such as effective diffusivity (0.2–1 × 10−9 m2/s) and convective heat and mass transfer coefficients (7–14 W/m2/K and 2.8–4.5 × 10−6 m/s, respectively) can be utilized in designing different fish drying systems. Average and instantaneous total energy consumption, specific moisture extraction ratio, and specific energy consumption are evaluated in order to provide a comprehensive picture of the drying process.Practical ApplicationsFresh‐ and salt‐water fishes account for major sources of protein‐rich food for substantial parts of the population in underdeveloped and developing nations. To circumvent the wastage associated with microbial contaminations during prolific seasons, fish drying has been widely employed as a way of preserving this perishable food. Convective drying of agricultural products as well as marine foods is a commonly employed drying method for food preservation. This study investigates the drying behavior of three different freshwater fishes using an in‐house constructed forced convective air dryer. The experimental drying characteristics and estimated parameters by model fitting during fish drying will be particularly applicable in the wide field of fish drying. The outcome of this study can also be utilized for more effectively designing and evaluating low‐cost convective fish dryers.

Role of Nitroglycerin administration through inhalation route as Nitric oxide donor in decreasing pulmonary hypertension as consequence of non-cyanotic congenital heart defects in children candidate for diagnostic cardiac catheterization

ABSTRACT Background: This work aimed to study nitroglycerin effect through inhalation route on pulmonary hemodynamics in children complaining from pulmonary hypertension associated withs noncyanotic congenital heart defects candidate for diagnostic cardiac catheterization. Methods: This prospective study had been carried out in Cardiac Catheterization Centre at El-Shatby Pediatric Alexandria University Hospital after approval of the medical ethical committee. Each parent had received verbal and plain language written explanation of the research protocol and informed consent had been taken from their parents. Eighteen children below twelve years old complaining noncyanotic congenital heart defects and left to right shunt with pulmonary hypertension who required diagnostic cardiac catheterization had participated prospectively in this research. After induction of anaesthesa, systemic and pulmonary pressures had been recorded for all patients invasively. Where pulmonary vascular resistance index and systemic vascular resistance index had been determined using standard formula based on Fick's principle through computerized program. Then patients received 2.5 µg/kg/min nitroglycerin through inhalation for 30 min. After that all measurements had been recorded again. Results: After nitroglycerin inhalational, mean, diastolic and systolic pulmonary pressures reduced significantly in comparison with their baseline data. Also, the PVRI had diminished from baseline data. No significate changes were recorded for systemic pressures and SVRI. Conclusion: Nitroglycerin inhalation decreased pulmonary pressures as well as pulmonary vascular resistance index, with no effect on systemic haemodynamics nor systemic vascular resistance index in kids with pulmonary hypertension as a consequence of noncyanotic congenital heart defects.

A Continuous Noninvasive Method to Assess Mixed Venous Oxygen Saturation: A Proof-of-Concept Study in Pigs.

Mixed venous oxygen saturation (Svo2) is important when evaluating the balance between oxygen delivery and whole-body oxygen consumption. Monitoring Svo2 has so far required blood samples from a pulmonary artery catheter. By combining volumetric capnography, for measurement of effective pulmonary blood flow, with the Fick principle for oxygen consumption, we have developed a continuous noninvasive method, capnodynamic Svo2, for assessment of Svo2. The objective of this study was to validate this new technique against the gold standard cardiac output (CO)-oximetry Svo2 measurement of blood samples obtained from a pulmonary artery catheter and to assess the potential influence of intrapulmonary shunting. Eight anesthetized mechanically ventilated domestic-breed piglets of both sexes (median weight 23.9 kg) were exposed to a series of interventions intended to reduce as well as increase Svo2. Simultaneous recordings of capnodynamic and CO-oximetry Svo2 as well as shunt fraction, using the Berggren formula, were performed throughout the protocol. Agreement of absolute values for capnodynamic and CO-oximetry Svo2 and the ability for capnodynamic Svo2 to detect change were assessed using Bland-Altman plot and concordance analysis. Overall bias for capnodynamic versus CO-oximetry Svo2 was -1 percentage point (limits of agreement -13 to +11 percentage points), a mean percentage error of 22%, and a concordance rate of 100%. Shunt fraction varied between 13% at baseline and 22% at the end of the study and was associated with only minor alterations in agreement between the tested methods. In the current experimental setting, capnodynamic assessment of Svo2 generates absolute values very close to the reference method CO-oximetry and is associated with 100% trending ability.

Novel noninvasive estimation of mixed venous oxygen saturation by echocardiography and expired gas analysis.

Mixed venous oxygen (O2) saturation ([Formula: see text]) is an important measure for evaluating the sufficiency of cardiac output (CO) relative to whole body O2 consumption (V̇o2), while clinical use is limited to the required invasive catheterization. According to Fick's equation, V̇o2 (mL/min) = CO (L/min) × Hb (g/dL) × 1.36 (mL/g) × ([Formula: see text] - [Formula: see text])/10 (Hb = hemoglobin concentration, [Formula: see text] = arterial blood O2 saturation). Because V̇o2, CO, Hb, and [Formula: see text] can be measured noninvasively with expired gas analysis, echocardiography, a simple blood test, and percutaneous O2 saturation, respectively, [Formula: see text] can be calculated noninvasively. We hypothesized that noninvasively calculated [Formula: see text] shows a significant correlation and agrees well with invasively measured [Formula: see text]. In 47 patients (29 men; mean age, 70 ± 12 yr) who underwent right heart catheterization, [Formula: see text] was directly measured by sampling pulmonary artery blood. Noninvasively calculated [Formula: see text] was also obtained by the method described above. The calculated [Formula: see text] was significantly correlated with the measured [Formula: see text] (r = 0.79, P < 0.001) and was significantly smaller than the measured [Formula: see text] (70 ± 5.1 vs. 72.1 ± 4.9%, P < 0.001). Bias at [Formula: see text] was -2.2% (95% confidence interval, -3.2 to -1.1%) with limits of agreement from -9.5 to 5.2%, demonstrating acceptable agreement. The optimal cutoff value of calculated [Formula: see text] was 69% for reduced measured [Formula: see text] < 70% with an area under the curve of 0.94. Reduced calculated [Formula: see text] < 69% indicated a sensitivity of 92.9% and a specificity of 90.9% for reduced measured [Formula: see text] < 70%. Noninvasive [Formula: see text] calculated from echocardiography, expired gas analysis, percutaneous arterial blood O2 saturation, and hemoglobin level significantly correlated and agreed well with direct [Formula: see text] measured by catheterization. This novel method allows for practical evaluation of [Formula: see text] to assess the sufficiency of CO according to whole body metabolism.NEW & NOTEWORTHY Clinical use of mixed venous oxygen saturation ([Formula: see text]) is limited to the required invasive procedure. With Fick's equation, expired gas analysis, echocardiography, simple blood tests, and percutaneous oxygen saturation, [Formula: see text] can be calculated noninvasively. We hypothesized that noninvasively calculated [Formula: see text] shows a significant correlation and agrees well with invasively measured [Formula: see text]. The present study examined the relationship between measured [Formula: see text] and calculated [Formula: see text] in patients who underwent right heart catheterization and demonstrated acceptable agreement. This novel method can expand the indication of evaluating [Formula: see text].

Vascular ATP-sensitive K+ channels support maximal aerobic capacity and critical speed via convective and diffusive O2 transport.

Oral sulphonylureas, widely prescribed for diabetes, inhibit pancreatic ATP-sensitive K+ (KATP ) channels to increase insulin release. However, KATP channels are also located within vascular (endothelium and smooth muscle) and muscle (cardiac and skeletal) tissue. We evaluated left ventricular function at rest, maximal aerobic capacity ( O2 max) and submaximal exercise tolerance (i.e. speed-duration relationship) during treadmill running in rats, before and after systemic KATP channel inhibition via glibenclamide. Glibenclamide impaired critical speed proportionally more than O2 max but did not alter resting cardiac output. Vascular KATP channel function (topical glibenclamide superfused onto hindlimb skeletal muscle) resolved a decreased blood flow and interstitial PO2 during twitch contractions reflecting impaired O2 delivery-to-utilization matching. Our findings demonstrate that systemic KATP channel inhibition reduces O2 max and critical speed during treadmill running in rats due, in part, to impaired convective and diffusive O2 delivery, and thus O2 , especially within fast-twitch oxidative skeletal muscle. Vascular ATP-sensitive K+ (KATP ) channels support skeletal muscle blood flow and microvascular oxygen delivery-to-utilization matching during exercise. However, oral sulphonylurea treatment for diabetes inhibits pancreatic KATP channels to enhance insulin release. Herein we tested the hypotheses that: i) systemic KATP channel inhibition via glibenclamide (GLI; 10 mg kg-1 i.p.) would decrease cardiac output at rest (echocardiography), maximal aerobic capacity ( O2 max) and the speed-duration relationship (i.e. lower critical speed (CS)) during treadmill running; and ii) local KATP channel inhibition (5 mg kg-1 GLI superfusion) would decrease blood flow (15 µm microspheres), interstitial space oxygen pressures (PO2 is; phosphorescence quenching) and convective and diffusive O2 transport ( O2 and DO2 , respectively; Fick Principle and Law of Diffusion) in contracting fast-twitch oxidative mixed gastrocnemius muscle (MG: 9% type I+IIa fibres). At rest, GLI slowed left ventricular relaxation (2.11 ± 0.59 vs. 1.70 ± 0.23 cm s-1 ) and decreased heart rate (321 ± 23 vs. 304 ± 22 bpm, both P < 0.05) while cardiac output remained unaltered (219 ± 64 vs. 197 ± 39 ml min-1 , P > 0.05). During exercise, GLI reduced O2 max (71.5 ± 3.1 vs. 67.9 ± 4.8 ml kg-1 min-1 ) and CS (35.9 ± 2.4 vs. 31.9 ± 3.1 m min-1 , both P < 0.05). Local KATP channel inhibition decreased MG blood flow (52 ± 25 vs. 34 ± 13 ml min-1 100 g tissue-1 ) and PO2 isnadir (5.9 ± 0.9 vs. 4.7 ± 1.1 mmHg) during twitch contractions. Furthermore, MG O2 was reduced via impaired O2 and DO2 (P < 0.05 for each). Collectively, these data support that vascular KATP channels help sustain submaximal exercise tolerance in healthy rats. For patients taking sulfonylureas, KATP channel inhibition may exacerbate exercise intolerance.

Adolf Eugen Fick (1829-1901) – The Man Behind the Cardiac Output Equation

Adolf Fick was a German physiologist, born in Kassel in 1829, who studied medicine at the University of Marburg and graduated in 1851. He worked first in Zurich and then in Wurzburg. Most of his studies were based on physics and mathematics, and deep analysis, and only later were proven by experiments. Fick's name in physics is associated to the laws of diffusion of solutions, and in medicine to the principle of cardiac output calculation. In 1855, he proposed Fick's laws on gas diffusion. In 1870, he devised Fick's principle, which allows the measurement of cardiac output and calculations of intracardiac shunts from the arteriovenous oxygen difference. The method was later generalized to the Fick principle, according to which the flow of an indicator taken up or released by an organ corresponds to the difference between the indicator flows in the inflow and outflow tracts. Fick invented several devices most of them aimed to improve precision in his physiologic experiments. In 1868, he invented the plethysmograph, for recording the speed of blood in the human artery. In 1888, the tonometer for measuring from outside the hydrostatic pressure inside the eyeball. After 3 decades as Professor in Wurzburg, he retired. Fick died at Blankenberge, Belgium in 1901 age 71 years old.

Hygroelasticity analysis of an elastically restrained functionally graded porous metamaterial circular plate resting on an auxetic material circular plate

The main objective of this research is to investigate the hygroelastic behavior of a non-homogeneous circular plate made up of porous metamaterial resting on an auxetic material plate. The mechanical properties of the main plate, as well as moisture concentration, vary as an exponential function in the transverse direction. Poisson’s ratio is constant. The elastic supporting medium is developed by considering the structure-structure coupling. Based on the linear hygroelasticity theory, the governing state equations in terms of displacements and moisture concentration are acquired. At first, the Fickian equation is solved to compute the nonlinear distribution of moisture through the plate thickness, and then the state equations are semi-analytically solved using the state-space (SS) method and the differential quadrature (DQ) rule to predict the elastic field quantities. A comprehensive parametric analysis is accomplished to elucidate the effects of key parameters on the steady-state response of the plate under the mechanical and hygral loads.

Evaluation methodology of diffusion coefficient of guest substances associated with angstrom-scale open spaces in materials by slow positron beam.

The knowledge of elemental migration associated with angstrom-scale open spaces is a prerequisite for sophisticated material design with respect to nanodispersion as well as a better understanding of molecular migration in a geological environment. Here, we show the methodology for evaluating the diffusion coefficient of guest substances focusing on angstrom-scale open spaces, where the depth-variation of open spaces caused by elemental diffusion in the micrometer-scale surface region is examined by the variable-energy slow positron beam. The present methodology determines a low diffusion coefficient of ∼10-14 cm2 s-1 for potassium at 533 K in SiO2 glass within the framework of Fick's principle providing the evidence that ∼2.5 Å open spaces intrinsically present in the glass matrix govern the diffusion process.