342 Cardiorespiratory fitness and systemic vascular resistance: oxygen pressure as a novel marker of peripheral vascular response during cardiopulmonary exercise testing

Aims The key role of systemic vascular resistance (SVR) in cardiovascular performance during exercise has been invasively demonstrated, however no data have been non-invasively obtained by analysing SVR response using cardiopulmonary exercise testing (CPET). To investigate the relationship between SVR at peak, maximum oxygen uptake (VO2 peak), and its determinants using CPET. Methods and results 1130 consecutive subjects were enrolled; according to physiology, SVR was determined as the ratio between mean arterial pressure (MAP) and cardiac output (CO). A novel parameter, named oxygen pressure (MAP peak/VO2 peak) was also created. Mean age was 61 ± 12 years and male gender was prevalent (61%); 66% of patients had arterial hypertension, 74% dyslipidaemia, 19% diabetes, 20% had smoking habit, and 26% previous history of cardiovascular (CV) disease. Significant inverse correlations between SVR peak and VO2/kg peak (P < 0.001), oxygen pulse (P < 0.001), CV efficiency (P < 0.001), chronotropic response (P < 0.001), and oxygen uptake exaction slope (P < 0.001) were found. Moreover, positive correlation between SVR peak and VE/VCO2 slope (P < 0.001) was observed. After multivariate analysis, the inverse correlation between peak SVR and peak VO2 remained significant (P < 0.001). Similar results were found considering oxygen pressure. Conclusions Low values of SVR at peak exercise, non-invasively evaluated with CPET, are associated with high levels of cardiorespiratory fitness. Oxygen pressure may represent a novel and simple CPET marker of peripheral vascular response to exercise, thereby representing a promising field of research in exercise medicine.

The clinical characteristics of patients with pulmonary hypertension combined with obstructive sleep apnoea

Objective Obstructive sleep apnoea (OSA) is one cause of pulmonary hypertension (PH) and can also emerge along with PH. The clinical diagnosis and treatment of OSA in patients with PH are still controversial. The purpose of this clinical observation study was to observe and summarize the incidence and clinical characteristics of OSA in patients with PH and to explore possible predictors of PH combined with OSA. Methods Patients with PH diagnosed by right heart catheterization who underwent overnight cardiorespiratory monitoring from December 2018 to December 2020 were enrolled. OSA was defined as an apnoea–hypopnoea index of ≥ 5/h with ≥ 50% of apnoeic events being obstructive. Baseline clinical characteristics and parameters were collected to compare PH patients with and without OSA. Logistic regression analysis was run to determine the risk factors for OSA in PH patients. Results A total of 35 (25%) of 140 patients had OSA. OSA is relatively frequent in patients with PH, especially in patients with chronic thromboembolic pulmonary hypertension and patients with lung disease– or hypoxia-associated PH. The patients who had OSA were mostly male and had a higher age and a lower daytime arterial oxygen pressure. Logistic regression analysis found that older age, male sex, and lower daytime arterial blood oxygen pressure correlated with OSA in PH patients. Conclusion OSA is common in patients with PH. Lower daytime arterial oxygen pressure is a risk factor for OSA in older male patients with PH.

Electronic structure of thermally oxidized tungsten

The electronic structure of thermally oxidized tungsten used as an emitter in thermal ionization of organic molecules is studied. Tungsten foil was thermally oxidized at oxygen pressure 1 Torr and temperature 950 K. The photoemission spectra from the valence band and O 2s and W 4f core levels are studied under synchrotron excitation with the photon energies 100 ÷ 600 eV. It is shown that thermal oxidation of tungsten leads to the formation in the W near-surface region various tungsten oxides with an oxidation state from 6+ to 4+. In this case, mainly tungsten oxides with an oxidation state of 6+ are formed on the surface, the proportion of which gradually decreases with distance from the surface with an increase in tungsten oxides with an oxidation state of 4+.

Optimal Cerebral Perfusion Pressure Guided by Brain Oxygen Pressure Measurement

Background: Although increasing cerebral perfusion pressure (CPP) is commonly accepted to improve brain tissue oxygen pressure (PbtO2), it remains unclear whether recommended CPP targets (i. e., >60 mmHg) would result in adequate brain oxygenation in brain injured patients. The aim of this study was to identify the target of CPP associated with normal brain oxygenation.Methods: Prospectively collected data including patients suffering from acute brain injury and monitored with PbtO2, in whom daily CPP challenge using vasopressors was performed. Initial CPP target was >60 mmHg; norepinephrine infusion was modified to have an increase in CPP of at least 10 mmHg at two different steps above the baseline values. Whenever possible, the same CPP challenge was performed for the following days, for a maximum of 5 days. CPP “responders” were patients with a relative increase in PbtO2 from baseline values > 20%.Results: A total of 53 patients were included. On the first day of assessment, CPP was progressively increased from 73 (70–76) to 83 (80–86), and 92 (90–96) mmHg, which resulted into a significant PbtO2 increase [from 20 (17–23) mmHg to 22 (20–24) mmHg and 24 (22–26) mmHg, respectively; p < 0.001]. Median CPP value corresponding to PbtO2 values > 20 mmHg was 79 (74–87) mmHg, with 2 (4%) patients who never achieved such target. Similar results of CPP targets were observed the following days. A total of 25 (47%) were PbtO2 responders during the CPP challenge on day 1, in particular if low PbtO2 was observed at baseline.Conclusions: PbtO2 monitoring can be an effective way to individualize CPP values to avoid tissue hypoxia. Low PbtO2 values at baseline can identify the responders to the CPP challenge.

Application of Intelligent Monitoring of Percutaneous Partial Oxygen Pressure in Evaluating the Evolution of Scar Hyperplasia

The study aimed to investigate the dynamic changes of percutaneous partial oxygen pressure during the development and evolution of a hypertrophic scar. Twenty cases of hypertrophic scar patients at different stages were selected. A percutaneous oxygen monitor was used to measure oxygen partial pressure in the scar and normal skin tissue at 14, 30, 60, and 90 days after surgery. The changes of oxygen partial pressure, tissue structure, HIF-1α, and VEGF expression in the scar tissue were observed, and the correlation was analyzed. In the scar maturation process, with the prolongation of time, the partial oxygen pressure in the tissue increased gradually. The expression intensity of HIF-1α and VEGF decreased gradually, HIF-1α was positively correlated with VEGF (r = 0.98, P < 0.01 ), there was a negative correlation between oxygen partial pressure and HIF-1 α expression (r = −0.92, P < 0.01 ), and it was negatively correlated with VEGF (r = −0.88, P < 0.01 ). TcPO2 measurement can be used to assess scar maturity; HIF-1 α and VEGF may play an essential role in regulating partial oxygen pressure in the scar tissue.

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Granular films containing Fe50Co50Zr10 alloy nanoparticles inside Pb0,81Sr0,04(Na0,5Bi0,5)0,15(Zr0,575Ti0,425)O3 (PZT) ferroelectric matrix possess a combination of functional magnetic and electrical properties which can be efficiently controlled by means of external electric or magnetic fields. The formation of the required granular structure in PZT matrix is only possible if synthesis is carried out in an oxygen-containing atmosphere leading to substantial oxidation of metallic nanoparticles. Thus an important task is to study the oxidation degree of metallic nanoparticles depending on synthesis conditions and the effect of forming phases on the electrical properties of the films. The relationship between the structural and phase state and electrical properties of granular FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%) synthesized in an oxygen-containing atmosphere at the oxygen pressure PO in a range of (2.4–5.0) · 10–3 Pa has been studied using X-ray diffraction, EXAFS and four-probe electrical resistivity measurement. Integrated comparative analysis of the structural and phase composition and local atomic order in (FeCoZr)x (PZT)100-x films has for the first time shown the fundamental role of oxygen pressure PO during synthesis on nanoparticle oxidation and phase composition. We show that the oxygen pressure being within PO = 3.2 · 10–3 Pa an increase in x leads to a transition from nanoparticles of Fe(Co,Zr)O complex oxides to a superposition of complex oxides and a-FeCo(Zr,O) ferromagnetic nanoparticles (or their agglomerations). At higher oxygen pressures РО = 5.0 · 10–3 Pa the nanoparticles undergo complete oxidation with the formation of the (FexCo1-x)1-δO complex oxide having a Wurtzite structure. The forming structural and phase composition allows one to explain the observed temperature dependences of the electrical resistivity of granular films. These dependences are distinguished by a negative temperature coefficient of electrical resistivity over the whole range of film compositions at a high oxygen pressure (РО = 5.0 · 10–3 Pa) and a transition to a positive temperature coefficient of electrical resistivity at a lower oxygen pressure (РО = 3.2 · 10–3 Pa) in the synthesis atmosphere and x &gt; 69 at.% in the films. The transition from a negative to a positive temperature coefficient of electrical resistivity which suggests the presence of a metallic contribution to the conductivity is in full agreement with the X-ray diffraction and EXAFS data indicating the persistence of unoxidized a-FeCo(Zr,O) ferromagnetic nanoparticles or their agglomerations.