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The variation in the conformations of hemoglobin heme and globin in response to different oxygen partial pressures (pO2) has been studied by Raman spectroscopy inside erythrocytes and in hemoglobin dissolved in incubation medium. The spectra of hemoglobin inside erythrocytes and in the medium show that several characteristic bands in the range from 1000 to 1700 cm–1 (stretching vibrations in the heme group) and in the high-frequency range from 2800 to 3000 cm–1 (stretching vibrations in globin amino acids) vary with pO2 levels. The curve of hemoglobin saturation with oxygen (sO2) obtained from the Raman-scattering data displays sigmoidal behavior only in hemoglobin inside erythrocytes. It has been shown that differences in heme conformation at different pO2 levels affect the ability of hemoglobin to form complexes with nitric oxide. As the pO2 level increases, the conformational changes of hemoglobin heme in the cell entail an increase in the contribution of vibrations of lateral –CH3 groups in pyrrole half-rings and group vibrations of bonds inside pyrrole half-rings, whereas the globin conformation is associated with a higher contribution of vibrations from H-methine groups and symmetrical terminal methylene groups in amino acids. [ABSTRACT FROM AUTHOR]

We investigate theoretically the main aspects of the formation of cadmium oxide thin films (by metal evaporation) relative to non-stoichiometry and partial pressure of oxygen. As a matter of fact, mathematical relationships are obtained from that the Cd and CdO phases coexist when the corresponding chemical reaction begins. In fact, the Cd pressure (equal to the CdO one) is found to be proportional to the oxygen absolute temperature which, in turn, equals the Cd (or CdO) absolute temperature. Moreover, the electron drift-mobility in CdO is obtained as a function of the above temperature and as a function of the oxygen partial pressure. We emphasize that chemical kinetics is studied quantitatively by taking into account that a part of cadmium does not combine with oxygen, that is, stoichiometry vanishes. This means that, initially, CdO is still amorphous. This state occurs when the partial pressure of oxygen is smaller than the so-called optimum value of pressure which, by definition, is the value of the oxygen partial pressure at which the optical transmittance of CdO is maximum. These issues are investigated (by means of theoretical considerations) accurately in consistency with experimental data. [ABSTRACT FROM AUTHOR]

Portable clinical analysers are gradually being involved in on-site assessment of haematic parameters in fish. The purpose of this study was to evaluate the i-STAT portable clinical analyser (i-STAT PCA) for accuracy and reliability of measuring blood pH, partial pressure of oxygen (pO2), haematocrit, haemoglobin, sodium, potassium and calcium in Atlantic cod (Gadus morhua). Haematological parameters detected with the i-STAT PCA were compared with conventional laboratory techniques (CLTs). Two types of disposable cartridges were used (CHEM8+ and CG4+) with the i-STAT PCA, and experiments were performed at two different temperature regimes (5 °C and 15 °C) and four different carbon dioxide (CO2) levels (0%, 0.1%, 0.5% and 1%). All blood parameters measured with the i-STAT PCA showed heterogeneous inaccuracy under the tested conditions, but the highest discrepancies were registered in blood pO2. The i-STAT PCA systematically overestimated the pO2 measurements. Our research suggests that i-STAT PCA is not an appropriate tool for pO2 measurements especially in coldwater fish species. The i-STAT PCA consistently underestimated the pH and haematocrit values especially at a lower temperature, although those parameters indicate significant high correlation at 15 °C. Furthermore, the analysed ions showed overestimation of sodium and underestimation of potassium and calcium. [ABSTRACT FROM AUTHOR]

Simple and accurate expressions describing the PaO2-FiO2 relationship in mechanically ventilated patients are lacking. The current study aims to validate a novel mathematical expression for accurate prediction of the fraction of inspired oxygen that will result in a targeted arterial oxygen tension in non-smoking and smoking patients receiving mechanical ventilation following open heart surgeries. One hundred PaO2-FiO2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of FiO2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred PaO2-FiO2 data pairs were obtained from 25 smoking patients mechanically ventilated following open heart surgeries. The utility of the new mathematical expression in accurately describing the PaO2-FiO2 relationship in these patients was assessed by the regression and Bland-Altman analyses. Significant correlations were seen between the true and estimated FiO2 values in non-smoking (r2 = 0.9424; p < 0.05) and smoking (r2 = 0.9466; p < 0.05) patients. Tight biases between the true and estimated FiO2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated PaO2/FiO2 ratios in non-smoking (r2 = 0.9530; p < 0.05) and smoking (r2 = 0.9675; p < 0.05) patients. Tight biases between the true and estimated PaO2/FiO2 ratios for non-smoking (-18 mmHg) and smoking (-16 mmHg) patients were also observed. The new mathematical expression for the description of the PaO2-FiO2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery. [ABSTRACT FROM AUTHOR]

Background: Apnea testing is an essential step in the clinical diagnosis of brain death. Current international guidelines recommend placement of an oxygen (O2) insufflation catheter into the endotracheal tube to prevent hypoxemia, but use of a continuous positive airway pressure (CPAP) valve may be more effective at limiting arterial partial pressure of O2 (PO2) reduction.Methods: We performed a multicenter study assessing consecutive apnea tests in 14 intensive care units (ICUs) in two cities utilizing differing protocols. In one city, O2 catheters are placed and arterial blood gases (ABGs) performed at intervals determined by the attending physician. In the other city, a resuscitation bag with CPAP valve is attached to the endotracheal tube, and ABGs performed every 3-5 min. We assessed arterial PO2, partial pressure of carbon dioxide (PCO2), pH, and blood pressure at the beginning and termination of each apnea test.Results: Thirty-six apnea tests were performed using an O2 catheter and 50 with a CPAP valve. One test per group was aborted because of physiological instability. There were no significant differences in the degree of PO2 reduction (-59 vs. -32 mmHg, p = 0.72), rate of PCO2 rise (3.2 vs. 3.9 mmHg per min, p = 0.22), or pH decline (-0.02 vs. -0.03 per min, p = 0.06). Performance of ABGs at regular intervals was associated with shorter test duration (10 vs. 7 min, p < 0.0001), smaller PCO2 rise (30 vs. 26 mmHg, p = 0.0007), and less pH reduction (-0.20 vs. -0.17, p = 0.0012). Lower pH at completion of the apnea test was associated with greater blood pressure decline (p = 0.006).Conclusion: Both methods of O2 supplementation are associated with similar changes in arterial PO2 and PCO2. Performance of ABGs at regular intervals shortens apnea test duration and may avoid excessive pH reduction and consequent hemodynamic effects. [ABSTRACT FROM AUTHOR]

Introduction: Donor PO levels are used for assessing organs for lung transplantation (LTx), but survival implications of PO levels in adult cystic fibrosis (CF) patients receiving LTx are unclear. Methods: UNOS registry data spanning 2005-2013 were used to test for associations of donor PO with patient survival and bronchiolitis obliterans syndrome (BOS) in adult (age ≥ 18 years) first-time LTx recipients diagnosed with CF. Results: The analysis included 1587 patients, of whom 1420 had complete data for multivariable Cox models. No statistically significant differences among donor PO categories of ≤200, 201-300, 301-400, or >400 mmHg were found in univariate survival analysis (log-rank test p = 0.290). BOS onset did not significantly differ across donor PO categories (Chi-square p = 0.480). Multivariable Cox models of patient survival supported the lack of difference across donor PO categories. Interaction analysis found a modest difference in survival between the two top categories of donor PO when examining patients with body mass index (BMI) in the lowest decile (≤16.5 kg/m). Conclusions: Donor PO was not associated with survival or BOS onset in adult CF patients undergoing LTx. Notwithstanding statistically significant interactions between donor PO and BMI, there was no evidence of post-LTx survival risk associated with donor PO below conventional thresholds in any subgroup of adults with CF. [ABSTRACT FROM AUTHOR]

Abstract: We investigate diffusivity and conductivity in the context of electronic transport in crystalline cadmium oxide by knowing the electron concentration in CdO as a function of the partial pressure of oxygen in the deposition process of the material in question. From the chemical kinetics of the reaction by which CdO is formed, first we consider an approximate relationship for the electron concentration in terms of the above pressure. In fact, by taking into account this relationship and other issues, we determine the product diffusivityconductivity in crystalline CdO. This product can be considered as a significant figure of merit. [ABSTRACT FROM AUTHOR]

Special features of carbooxidation of titanium in the process of saturation by a gas (gas-phase) method from powders are studied. The effects of various process factors, i.e., the temperature and time parameters of the saturation, the composition of the gas component of the saturating medium (the partial pressure of oxygen), its dynamics, the method of feeding into the reaction space of the furnace, and the composition and fineness of the powder carbon-containing component of the medium, are determined. [ABSTRACT FROM AUTHOR]

Atlantic cod, Gadus morhua, were exposed to a progressive stepwise decline in water oxygen pressure (19.9, 13.2, 10.5, 8.4, 6.2 and 4.3 kPa PO2). Fish swimming speed and indicators of primary and secondary stress (e.g. blood cortisol and lactate) were measured to assess whether a severe shift in physiological homeostasis (i.e. stress) preceded any change in behaviour or vice versa. Swimming speed increased by 18% when PO2 was reduced rapidly from 19.9 kPa to 13.2 kPa and was interpreted as an initial avoidance response. However, swimming speed was reduced by 21% at a moderate level of steady PO2 (8.4 kPa) and continued to drop by 41% under progressively deep hypoxia (4.3 kPa). Elevations in plasma cortisol and blood lactate indicated major physiological stress but only at 4.3 kPa, which corresponds to the critical oxygen tension of this species. We propose that the drop in speed during hypoxia aids to offset major stress and is adaptive for the survival of cod in extensive areas of low oxygen. [ABSTRACT FROM AUTHOR]

Transcutaneous PO (tcPO) has been shown to closely approximate arterial PO (PaO) in infants with normal oxygenation (PaO 60-100 mm Hg). During hypoxemia (PaO<60 mm Hg), or administration of vasoactive drugs, such as tolazoline, correlation is frequently so poor that tcPO monitoring is of little value. We examined the relationship of tcPO to PaO among 6 infants with cyanotic congenital heart disease who were receiving prostaglandin E (PGE). Close, linear correlation was found, even during hypoxemia. We conclude that tcPO monitoring has potential clinical value in such patients. [ABSTRACT FROM AUTHOR]