Drying and color in punamuña leaves (Satureja boliviana)

Drying allows water to be removed and food to be preserved, however, this operation can degrade color. Punamuña leaves are aromatic and used for medicinal purposes in the Peruvian Andes. This research aimed to determine and model the drying kinetics, the diffusivity coefficient (Def), the activation energy (Ea), and the color of punamuña leaves. A horizontal dryer was used at 40, 50, and 60 °C and airspeed of 1.0 and 0.5 m / s; drying kinetics was modeled with 10 models. Def was determined with the Fick equation, Ea with the Arrhenius equation; the color was determined in the L* a* b* space. It was found that the triple exponential model with six parameters better represented the drying kinetics (R2> 99.73 and E <3.04%); Def increased with temperature and air velocity. Ea was found between 43.62 to 44.52 kJ/mol for speeds of 1.0 to 0.5 m/s respectively; L* and a*/b* decreased, the color difference ΔE * increased with increasing temperature and lower air velocity

Increased FIO2 Influences SvO2 Interpretation and Accuracy of Fick-based Cardiac Output Assessment in Cardiac Surgery Patients

Background: The study aimed to reveal how the fraction of inspired oxygen (FIO2) affected the value of mixed venous oxygen saturation (SvO2) and the accuracy of Fick-equation-based cardiac output (Fick-CO). Methods: Forty-two adult patients who underwent elective cardiac surgery were enrolled and randomly divided into two groups: FIO2 <0.7 or >0.85. Under stable general anesthesia, thermodilution-derived cardiac output (TD-CO), SvO2, PvO2, hemoglobin, SaO2, PaO2, and blood pH levels were recorded before surgical incision. Results: Significant differences in FIO2 values were observed between the two groups (0.56 ±0.08 in the <70% group and 0.92 ±0.03 in the >0.85 group; p <0.0001). The increasing FIO2 values lead to increases in SvO2, PvO2, and PaO2, with little effects on cardiac output and hemoglobin levels. When comparing to TD-CO, the calculated Fick-CO in both groups had moderate Pearson correlations and similar linear regression results. Although the FIO2 <0.7 group presented a less mean bias and a smaller limits of agreement, neither group met the percentage error criteria of <30% in Bland-Altman analysis.Conclusions: Increased FIO2 may influence the interpretation of SvO2 and the exacerbation of Fick-CO estimation, which could affect clinical management. Trial Registration: ClinicalTrials.gov ID number: NCT04265924. Retrospectively registered (Date of registration: February 12, 2020).

Correlation between central venous and mixed venous oxygen saturation in the elective abdominal aortic aneurysm surgery

Background/Aim. The concept of utilizing central venous oxygen saturation (ScvO2) to calculate cardiac index (CI) remains controversial and neither precise nor generally applicable conclusion has been reached yet. We evaluated the relationship between ScvO2 and mixed venous oxygen saturation (SvO2) in elective surgery of the abdominal aorta. The adequacy of their interchangeability was tested by comparing cardiac indices (CI) calculated by two methods in patients that underwent major vascular surgery. The aim of this study was to test the correlation between ScvO2 and SvO2 in different time frames, in patients undergoing elective abdominal aortic aneurysm (AAA) surgery as well as to determine if the use of ScvO2 for calculating CI by the modified Fick equation, could be feasible and accurate surrogate for the values obtained by pulmonary artery catheter (PAC). Methods. This prospective observational study included 125 consecutive patients that underwent elective AAA surgery. The ScvO2 and SvO2 data, as well as CI values, were obtained and compared from samples taken in three different time frames: immediately after induction of general anesthesia (T0), immediately after admission in the intensive care unit (ICU; T1), and 8 h after admission in the ICU (T2). The Fick equation, used for CI estimation from ScvO2 (CI-F), for the purpose of this study, was simplified according to Walley. Results. There was good linear correlation between ScvO2 and SvO2 in all time frames and linear regression study revealed strongest coefficient of determination (R2 = 0.661) in T2 time-frame. There was no correlation between CI-F (i.e. CI calculated from ScvO2 by modified Fick equation) and CI (measured by PAC from SvO2) in any time-frame. Conclusion. The results of our study confirm that ScvO2 is a reliable substitute for SvO2 among patients undergoing elective surgery of the AAA. However, ScvO2 cannot be used as a surrogate to true SvO2 in the calculation of CI.

Development of Experimental Chamber for Testing High-Temperature Hydrogen Permeation through Metal Foils

This paper describes the methodology for conducting experiments to study hydrogen diffusion through metal membranes using a specially designed diffusion chamber of an automated gas reaction controller complex. This complex allows experiments to study hydrogen diffusion with the following parameters: the inlet hydrogen pressure is up to 50 atmospheres, and the temperature in the chamber is from 30 °C to 1000 °C. The size of the samples is limited to a diameter of 10 mm and a thickness of 100 μm. The method for calculating the diffusion coefficient based on the Fick equation is also described. When studying hydrogen diffusion through a sample of Zr–1Nb alloy with nickel film deposited at the temperature of 550 °C, it was noted that phase transformations can be observed on the diffusion curve.

Abstract 19722: Cardiac Output Estimation by Inert Gas Rebreathing is Accurate in Mechanically Ventilated Children With Heart Disease

Introduction: Real time estimates of pulmonary (Qp) and systemic blood flow (Qs) could improve pediatric cardiac care. Current generation inert gas rebreathing (IGR) devices are safe, portable, and easy to use; can estimate Qp and Qs rapidly at the bedside; and can now be adapted for use in intubated patients. We compared IGR and two types of Fick Qp estimates, those using measured (FickM) and assumed (FickA) oxygen consumption (VO2) values, in mechanically ventilated pediatric cardiac patients with no shunt lesion or exclusive right-to-left shunt. Secondarily, we compared measured VO2 with assumed values and values back-calculated from the Fick equation (using measured saturations, hemoglobin and IGR Qp). Methods: In 18 intubated patients in the pediatric catheterization laboratory, the modified ventilator-compatible InnocorTM device was used to measure IGR Qp and breath-by-breath VO2; assumed VO2 was taken from LaFarge tables. Sampled pulmonary arterial and venous saturations were used to calculate FickM and FickA. Bland-Altman agreement and Spearman correlation were assessed for IGR Qp with FickA Qp and FickM Qp. Secondarily, agreement was analyzed between measured VO2, assumed VO2, and VO2 calculated from the Fick equation. Results: Subjects were aged 4-23 years, with a range of cardiac diagnoses. The figure shows Bland-Altman plots for Qp. Compared with FickA, IGR Qp had mean bias -0.9 L/min, 95% limits of agreement (=±1.96 SD) -2.8 to +1.0 L/min, and r=0.75. Compared with FickM, IGR Qp had mean bias -0.2 L/min, 95% limits of agreement -1.3 to +1.0 L/min, and r=0.90. Agreement of assumed and measured VO2 was poor (bias +23%, ±55%); measured VO2 agreed better with Fick calculated VO2 than assumed VO2. Conclusions: IGR Qp estimates agree well with Fick Qp estimates. This agreement improves when VO2 is measured, as assumed VO2 agrees poorly with measured VO2. IGR is an attractive option for bedside monitoring of Qp in intubated children.

Noninvasive estimation of microvascular O2 provision during exercise on-transients in healthy young males

Two methods for estimating changes in microvascular O2 delivery during the on-transient of exercise were evaluated. They were tested to assess the role of the adjustment of the estimated microvascular O2 delivery in the speeding of V̇o2 kinetics during a Mod1-Hvy-Mod2 protocol (Mod, moderate-intensity exercise; Hvy, heavy-intensity “priming” exercise), in which Mod2 is preceded by a bout of Hvy. Mod pulmonary V̇o2 (V̇o2p) and deoxy-hemoglobin [HHb] data were collected in 12 males (23 ± 3 yr); response profiles were fit with a monoexponential. Signals were also 1) scaled to a relative % of the response (0–100%) to calculate the [HHb]/V̇o2 ratio for each individual and 2) rearranged in the Fick equation for estimation of capillary blood flow (Qcap). A transient [HHb]/V̇o2 “overshoot” observed in Mod1 (1.06 ± 0.05; P < 0.05) was absent during Mod2 (1.01 ± 0.06; P > 0.05); reductions in the [HHb]/V̇o2 ratio (Mod1 − Mod2) were related to reductions in phase II τV̇o2p ( r = 0.82; P < 0.05). For Qcap, a near-exponential response was observed in 8/12 subjects in Mod1 and only in 4/12 subjects in Mod2. The Qcap profile was shown to be highly dependent on the [HHb] baseline-to-amplitude ratio. Thus, accurate and physiologically consistent estimations of Qcap were not possible in most cases. This study confirmed that priming exercise results in an improved O2 delivery as shown by the decreased [HHb]/V̇o2 ratio that was related to the smaller τV̇o2 in Mod2. Additionally, this study suggested that Qcap analysis may not be valid and should be interpreted with caution when assessing microvascular delivery of O2.

How to help students understand physiology? Emphasize general models.

Students generally approach topics in physiology as a series of unrelated phenomena that share few underlying principles. In many students' view, the Fick equation for cardiac output is fundamentally different from a renal clearance equation. If, however, students recognize that these apparently different situations can be viewed as examples of the same general conceptual model (e.g., conservation of mass), they may gain a more unified understanding of physiological systems. An understanding of as few as seven general models can provide students with an initial conceptual framework for analyzing most physiological systems. The general models deal with control systems, conservation of mass, mass and heat flow, elastic properties of tissues, transport across membranes, cell-to-cell communication, and molecular interaction.