Oxygen Content Difference Research Articles

Persistent Exertional Intolerance After COVID-19: Insights From Invasive Cardiopulmonary Exercise Testing

BackgroundSome patients with COVID-19 who have recovered from the acute infection after experiencing only mild symptoms continue to exhibit persistent exertional limitation that often is unexplained by conventional investigative studies.Research QuestionWhat is the pathophysiologic mechanism of exercise intolerance that underlies the post-COVID-19 long-haul syndrome in patients without cardiopulmonary disease?Study Design and MethodsThis study examined the systemic and pulmonary hemodynamics, ventilation, and gas exchange in 10 patients who recovered from COVID-19 and were without cardiopulmonary disease during invasive cardiopulmonary exercise testing (iCPET) and compared the results with those from 10 age- and sex-matched control participants. These data then were used to define potential reasons for exertional limitation in the cohort of patients who had recovered from COVID-19.ResultsThe patients who had recovered from COVID-19 exhibited markedly reduced peak exercise aerobic capacity (oxygen consumption [VO2]) compared with control participants (70 ± 11% predicted vs 131 ± 45% predicted; P < .0001). This reduction in peak VO2 was associated with impaired systemic oxygen extraction (ie, narrow arterial-mixed venous oxygen content difference to arterial oxygen content ratio) compared with control participants (0.49 ± 0.1 vs 0.78 ± 0.1; P < .0001), despite a preserved peak cardiac index (7.8 ± 3.1 L/min vs 8.4±2.3 L/min; P > .05). Additionally, patients who had recovered from COVID-19 demonstrated greater ventilatory inefficiency (ie, abnormal ventilatory efficiency [VE/VCO2] slope: 35 ± 5 vs 27 ± 5; P = .01) compared with control participants without an increase in dead space ventilation.InterpretationPatients who have recovered from COVID-19 without cardiopulmonary disease demonstrate a marked reduction in peak VO2 from a peripheral rather than a central cardiac limit, along with an exaggerated hyperventilatory response during exercise.

YBa2Cu3O7 films grown onto SrTiO3 and YSZ substrates by chemical solution deposition of trifluoroacetates

We report the preparation and characterization of YBa2Cu3O7 (YBCO) films grown onto SrTiO3 and YSZ substrates by the trifluoroacetates chemical solution deposition method and following sintering with oxygen atmosphere at 860 °C. The X-ray diffraction (XRD) reveals (00ℓ) – oriented crystallites indicating epitaxial growth of the films in the c-direction. Despite granular morphology and the presence of Y2BaCuO5 and CuO as minor secondary phases, the technique shows the successful formation of the superconducting YBCO and preventing the formation of the unwanted BaCO3 phase. Rocking curve measurements of the (005) reflection for the YBCO/SrTiO3 was fitted with one Gaussian function with full width at the half maximum (FWHM) of 0.44° confirming that it consists of YBCO crystallites with different texture. For the sample grown on YSZ, the rocking curve was fitted with two Gaussian functions, one corresponding to the YBCO layer (FWHM = 0.4°) and another to the substrate (FWHM = 0.3°). The magnetic measurements taken in zero field cooling and field cooling modes confirm the formation of the superconducting YBCO with critical temperatures (TC) 91.8 and 85.7 K for the samples grown onto YSZ and SrTiO3, respectively. The critical current density (JC) curves indirectly calculated by using the Bean´s model from the M(T) loops were JC ~ 109 A/cm2 for the sample deposited onto YSZ and JC ~ 107A/cm2 for the YBCO deposited onto SrTiO3. Overall, the difference in TC and JC values between both samples could be related to their difference in oxygen content, porosity, hole concentration per Cu ion and the presence of secondary phases.

Carbon supply–consumption balance in plant roots: effects of carbon use efficiency and root anatomical plasticity

The growth and maintenance of the plant root system may consume more than 50% of all photosynthates, making the root system a major carbon sink (Lambers et al., 2002). Carbon is supplied to roots via sieve tubes that are located in the phloem of the root stele, and is consumed for anabolic and catabolic processes. In a recent paper, Kong et al., (2021) proposed a framework to assess the carbon supply-consumption balance in plant roots that bridges root anatomical structures and root functioning using 'structural allometric relationships'. Their framework highlights the pivotal role of root radius and associated anatomical properties such as sieve tube radius and the size and number of root cells for the carbon supply-consumption balance.

Utility of venous‐to‐arterial carbon dioxide changes to arteriovenous oxygen content ratios in the prognosis of severe sepsis and septic shock: A systematic review and meta‐analysis

Background:Sepsis patients with insufficient tissue perfusion and hypoxia should be identified and resuscitated immediately. Recently, venous‐to‐arterial carbon dioxide pressure changes and the arteriovenous oxygen content difference ratio (Pcv‐aCO2/Ca‐vO2) as a predictor of tissue perfusion recovery and poor prognosis.Objectives:Pcv‐aCO2/Ca‐vO2 is a substitute for respiratory entropy, the elevation of which indicates a lack of tissue perfusion. Pcv‐aCO2/Ca‐vO2 can be used as an indicator to predict the prognosis of patients with sepsis or septic shock, but its prognostic value has not been fully evaluated. Here, we have performed a meta‐analysis to assess its predictive value for mortality.Methods:Meta‐analysis of Observational Studies in Epidemiology group guidelines were followed for this meta‐analysis. We searched the comprehensive electronic databases of PubMed, EMBASE, Web of Science, and Cochrane libraries from inception to March 2019, using the terms including “venous‐arterial,” “carbon dioxide,” “Shock, Septic,” and related keywords. The Newcastle‐Ottawa scale was used for quality evaluation of the literature. A meta‐analysis was performed using RevMan 5.3 and Stata 14.0 software to evaluate the effects of Pcv‐aCO2/Ca‐vO2 on short‐term mortality, sequential organ failure assessment, and acute physiology and chronic health evaluation scores in patients with sepsis or septic shock.Results:The final analysis included 13 clinical studies involving a total of 940 subjects. The results of the meta‐analysis showed that non‐surviving patients had higher Pcv‐aCO2/Ca‐vO2 than survivors after fluid resuscitation (standardized mean difference = 0.68, 95% confidence interval = 0.24–1.12) and blood samples taken 6 h after resuscitation showed a greater risk of mortality (risk ratio = 1.89, 95% confidence interval = 1.48–2.41) and sequential organ failure assessment scores (mean difference = 1.58, 95% confidence interval = 0.88–2.28, P &lt; 0.01) in patients with high Pcv‐aCO2/Ca‐vO2. These differences were statistically significant.Conclusion:This meta‐analysis indicates that Pcv‐aCO2/Ca‐vO2 has predictive value for mortality in patients with sepsis or septic shock. Further studies are now required to determine the optimal threshold for predicting sepsis mortality.Prospero Registration:The protocol for this systematic review was registered on PROSPERO (CRD 42019128134).

Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia

The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas’ equation (ΔCCO2D) over ΔO2 ratio (ΔCCO2D/ΔO2) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO2/CO2 content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO2) was lowered in a stepwise manner to decrease it beyond critical DO2 (DO2crit) by lowering either arterial PO2 (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO2, oxygen consumption ({dot{text{V}}text{O}}_{2}), ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 were obtained every 15 min. Beyond DO2crit, {dot{text{V}}text{O}}_{2} decreased, indicating dysoxia. ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 increased significantly only after reaching DO2crit in both models. At DO2crit, ΔPCO2/ΔO2 was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO2crit, ΔCCO2D/ΔO2 was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO2/ΔO2 continued to increase significantly (higher in the HH-model), whereas ΔCCO2D/ΔO2 tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO2/CO2 content relationship, but not the Haldane effect. ΔPCO2/ΔO2 was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO2 values, ΔPCO2/ΔO2 did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO2–hemoglobin dissociation curve, and then it should be interpreted with caution.

The Ability of Carbon Dioxide–Derived Indices to Predict Adverse Outcome After Cardiac Surgery

The objective of this study was to assess whether the central venous-to-arterial carbon dioxide partial-pressure difference (ΔPCO2) and the ratio of the ΔPCO2 to the arterial-venous difference in oxygen content (ΔPCO2/Ca-vO2) predict postoperative complications (PC) after cardiac surgery. Prospective, observational, noninterventional study. The study comprised 60 patients undergoing cardiac surgery with cardiopulmonary bypass. The primary endpoint was the occurrence of PC. Data were first analyzed in two groups based on the occurrence of PC. Then, receiver operating characteristic curves of the ΔPCO2 and the ΔPCO2/Ca-vO2 ratio were analyzed for the prediction of PC. Among the study participants, 22 (36.7%) experienced PC. The death rate was 18.3%. The present study found that the ΔPCO2 and the ΔPCO2/Ca-vO2 ratio predicted the occurrence of PC with areas under the curve of 0.702 and 0.666, respectively. The best thresholds of these markers were 8.3 mmHg for the ΔPCO2 and 2.16 mmHg/mL for the ΔPCO2/Ca-vO2 ratio. A significant difference was found for these indicators between the groups with and without PC. The ΔPCO2 and the ΔPCO2/Ca-vO2 ratio were significantly correlated to EuroSCORE II, duration of aortic clamping, majority of prognostic scores the first two days postoperatively, and the lactate level. The ΔPCO2/Ca-vO2 ratio is predictive of hyperlactatemia >2 mmol/L, with an area under the curve of 0.787. The ΔPCO2 and the ΔPCO2/Ca-vO2 ratio predict the occurrence of complications in cardiac surgery.

Effect of Oxygen Concentration on Neisseria gonorrhoeae Susceptibility to Resazomycins

As pathogenic bacterial species are becoming more resistant to commonly used antibiotics, it is essential for new antibiotics to be developed. A family of resazurin (Rz)-based compounds, resazomycins, was discovered to be highly effective antimicrobials against Neisseria gonorrhoeae (Ng) in vitro. However, when these compounds were tested in a mouse model of gonorrhea, only one resazomycin, resorufin pentyl ether (RPE), exhibited any therapeutic effect. These differences between in vitro and in vivo therapeutic efficacy may be due to differences in oxygen concentration. Most mammalian tissues exist at oxygen concentrations well below atmospheric levels, typically 2-5% instead of 20%. We hypothesized that decreased oxygen levels may confer resistance to resazomycins. To test this, we cultivated clinical isolates of Ng under different oxygen conditions and then determined the minimal inhibitory concentration (MIC) of various resazomycins. The MIC of resazurin for the different Ng isolates were up to 4-fold higher under 2% oxygen than 20% oxygen suggesting oxygen levels affect susceptibility to resazomycins. No significant difference in the MIC of RPE was observed under the different oxygen concentrations consistent with RPE being the sole resazomycin having efficacy against N. gonorrhoeae. We also calculated the MIC of three non-resazomycin based antibiotics and saw that there was no significant difference in MIC at the two oxygen concentrations. Further investigation is needed to determine how Ng is becoming resistant to resazomycins under low oxygen conditions.

The impact of vatinoxan on medetomidine–ketamine–midazolam immobilization in Patagonian maras (Dolichotis patagonum)

ObjectiveTo compare cardiovascular and ventilatory effects, immobilization quality and effects on tissue perfusion of a medetomidine–ketamine–midazolam combination with or without vatinoxan (MK-467), a peripherally acting α2-adrenoceptor antagonist. Study designRandomized, blinded, crossover study. AnimalsA group of nine healthy Patagonian maras (Dolichotis patagonum). MethodsMaras were immobilized twice with: 1) medetomidine hydrochloride (0.1 mg kg–1) + ketamine (5 mg kg–1) + midazolam (0.1 mg kg–1) (MKM) + saline or 2) MKM + vatinoxan hydrochloride (0.8 mg kg–1), administered intramuscularly. Drugs were mixed in the same syringe. At 20, 30 and 40 minutes after injection, invasive blood pressure, heart rate, respiration rate, end-tidal CO2, haemoglobin oxygen saturation, and muscle oxygenation were measured, arteriovenous oxygen content difference was calculated. Muscle tone, jaw tone, spontaneous blinking and palpebral reflex were evaluated. Times to initial effect, recumbency, initial arousal and control of the head were recorded. Paired t test, Wilcoxon matched-pairs signed rank test and analysis of variance were used to compare protocols; (p < 0.05). ResultsVatinoxan significantly reduced systolic (p = 0.0002), mean (MAP; p < 0.0001) and diastolic (p < 0.0001) arterial blood pressures between 20 and 40 minutes. MAPs at 30 minutes (mean ± standard deviation) with MKM and MKM + vatinoxan were 105 ± 12 and 71 ± 14 mmHg, respectively. Without vatinoxan, four animals were hypertensive (MAP > 120 mmHg), whereas with vatinoxan, four animals were hypotensive (MAP < 60 mmHg). Muscle and jaw tone were significantly more frequently present with MKM (both p = 0.039). Other measurements did not significantly differ between protocols. Conclusions and clinical relevanceIn Patagonian maras, vatinoxan attenuated the increase in blood pressure induced by medetomidine. Muscle and jaw tone were more frequently present with MKM, indicating that quality of immobilization with vatinoxan was more profound.

Randomized blinded trial of automated REBOA during CPR in a porcine model of cardiac arrest

BackgroundResuscitative endovascular balloon occlusion of the aorta (REBOA) reportedly elevates arterial blood pressure (ABP) during non-traumatic cardiac arrest. ObjectivesThis randomized, blinded trial of cardiac arrest in pigs evaluated the effect of automated REBOA two minutes after balloon inflation on ABP (primary endpoint) as well as arterial blood gas values and markers of cerebral haemodynamics and metabolism. MethodsTwenty anesthetized pigs were randomized to REBOA inflation or sham-inflation (n = 10 in each group) followed by insertion of invasive monitoring and a novel, automated REBOA catheter (NEURESCUE® Catheter & NEURESCUE® Assistant). Cardiac arrest was induced by ventricular pacing. Cardiopulmonary resuscitation was initiated three min after cardiac arrest, and the automated REBOA was inflated or sham-inflated (blinded to the investigators) five min after cardiac arrest. ResultsIn the inflation compared to the sham group, mean ABP above the REBOA balloon after inflation was higher (inflation: 54 (95%CI: 43–65) mmHg; sham: 44 (33–55) mmHg; P = 0.06), and diastolic ABP was higher (inflation: 38 (29–47) mmHg; sham: 26 (20–33) mmHg; P = 0.02), and the arterial to jugular oxygen content difference was lower (P = 0.04). After return of spontaneous circulation, mean ABP (inflation: 111 (95%CI: 94–128) mmHg; sham: 94 (95%CI: 65–123) mmHg; P = 0.04), diastolic ABP (inflation: 95 (95%CI: 78−113) mmHg; sham: 78 (95%CI: 50−105) mmHg; P = 0.02), CPP (P = 0.01), and brain tissue oxygen tension (inflation: 315 (95%CI: 139−491)% of baseline; sham: 204 (95%CI: 75−333)%; P = 0.04) were higher in the inflation compared to the sham group. ConclusionInflation of REBOA in a porcine model of non-traumatic cardiac arrest improves central diastolic arterial pressure as a surrogate marker of coronary artery pressure, and cerebral perfusion. Institutional protocol number2017-15-0201-01371.

The increased oxygen content in tantalum leads to decreased bioactivity and osteogenic ability of tantalum implants.

Tantalum (Ta) implants fabricated by current processing techniques inevitably contain more or less oxygen impurities due to the extremely high melting point and high affinity of oxygen for Ta. Therefore, in this study we investigated whether oxygen impurities cause any effects on the bioactivity of Ta. EDS analysis demonstrated the surface oxygen content difference among different fabricated Ta samples, and the surface water contact angle (WCA) of Ta with high oxygen content (HO-Ta) was significantly higher than that of Ta with medium (MO-Ta) and low (LO-Ta) oxygen content. The in vitro cellular experiments showed that MC3T3-E1 cells on Ta with lower oxygen content exhibited better adhesion, growth, morphological development and in vitro osteogenic ability. Similarly, the in vivo animal experiments indicated the better bone regeneration and ingrowth performances of Ta with lower oxygen content. In addition, the highest ROS production was detected in the HO-Ta group, while the lowest in the LO-Ta group. This study suggests that the oxygen content within Ta, which occurs unavoidably due to technical limitations, negatively affects the bioactivity of Ta in a dose-dependent manner, indicating the need to develop techniques to produce orthopedic all-Ta implants.

Cerebral Oxygenation and Metabolism in Patients Undergoing Clipping of Cerebral Aneurysm: A Comparative Study between Propofol-based total intravenous anesthesia and Sevoflurane-based inhalational anesthesia.

ABSTRACT Background: Sevoflurane unfortunately increases the cranial blood flow, blood volume, and pressure changes cope with cerebral aneurysmal neuroanesthesia goals. Propofol decreases the brain metabolism, blood flow, preserve cerebral reactivity to carbon dioxide, creates neuroprotective effect during cerebral ischemia. Hypothesis: Propofol-based total intravenous anesthesia would be more appropriate than sevoflurane-based inhalational technique during surgical clipping of cerebral aneurysm. Methods: A prospective, randomized, comparative study on 50 patients subjected for elective clipping of cerebral aneurysm, randomly allocated into two equal groups of 25 patients each: propofol-dormicum total intravenous only group and sevoflurane based inhalational group. Results: Jugular oxygen saturation (primary outcome), cerebral blood flow equivalent, heart rate, mean arterial blood pressure, and end tidal carbon dioxide tension were statistically significantly decreased in propofol group compared to sevoflurane group at basal, just after dura opening, at 1,2,3 hours later, and after scalp closure. Arterio-Jugular oxygen content difference, cerebral extraction ratio of O2, estimated cerebral metabolic rate for O2, serum lactate (mg/dl) showed significant increase in propofol group compared to sevoflurane group at basal, 1, 2, 3 h, and after scalp closure. Duration of surgery, time of recovery, blood loss, blood transfusion, intraoperative complications, urine output, total midazolam consumption, surgeon satisfaction, intensive care unit stay time, and Ramsay sedation scale difference was not significant in between both studied groups during the early postoperative period. Conclusion: Propofol based total intravenous anesthesia has better cerebral oxygenation and neuro anesthesia profile compared to sevoflurane-based inhalational anesthesia during cerebral aneurysm clipping surgery with systemic hemodynamic stability.

Experimental investigation on hydrodynamics and mass transfer of a novel fission gas removal equipment for molten salt reactor

The separation of fission gases like 135-Xe and 85-Ke from the liquid nuclear fuel is a focused topic in the molten salt reactor (MSR) community. In this paper, a compact fission gas removal equipment with a serpentine tube as the gas-liquid contactor is introduced. The novel design is free of any moving or rotating components, bringing great convenience in the real-time fuel treatment. As crucial factors influencing the gas removal performance, the two-phase hydrodynamics and interfacial mass transfer characteristics in the vertical serpentine tube are investigated under a water-nitrogen-oxygen system. Both highspeed photographing and conductivity probe are employed to capture the evolution of bubbly flow inside the tubular contactor. The oxygen concentration differences between the inlet and outlet of the device are measured under various operating conditions, and the overall volumetric mass transfer coefficient kla is derived to evaluate the gas removal efficiency. Experiment results imply a periodic transition of volume fraction profile between the off-center distribution in the downward flow and the near-wall distribution in the upward flow due to the centripetal effect in the U-bends. Bimodal distributions of bubble equivalent diameter are observed because of the intensive bubble coalescence inside the elbow. The overall kla is found to be linearly proportional to the liquid Reynolds number and gas volume fraction. The dimensionless mass transfer correlation proposed in this work predicts well the overall volumetric mass transfer coefficient.

Abstract 17257: Stroke Volume Reserve Index in HFrEF: A Non-Invasive Predictor of Early Clinical Outcomes and Marker of Inotropic Reserve

Introduction: We investigated whether stroke volume reserve index (SVRI), a novel non-invasive measure of inotropic reserve at submaximal exercise, would predict 1-year mortality and need for advanced therapies in heart-failure with reduced ejection fraction (HFrEF) patients. Methods: We retrospectively studied a consecutive series of 245 ambulatory patients (57±11 years, 84% men) with HFrEF at a single center who underwent cardiopulmonary exercise testing (CPET) from January 2013 to December 2018. The primary outcome was defined as heart-transplantation, urgent left ventricular assist device (LVAD) implantation or death within 1 year of evaluation. SVRI was estimated at rest and at anaerobic threshold by VO 2 (oxygen consumption)/pulse and previously validated estimates of C[a-v]O 2 (arteriovenous difference in oxygen content). Multivariate regression selected the optimal predictors. Results: Among HFrEF patients studied, 82 (33.5%) deteriorated: 34 required heart-transplantation, 20 required LVADs and 28 died. SVRI of less than 130% was the best predictor of clinical deterioration (OR 3.98, p&lt;0.005), followed by cardiac index of less than 2 L/min/m 2 (OR 3.74, p&lt;0.005), and peak VO 2 below the International Society for Heart and Lung Transplantation (ISHLT) cut-off (OR 3.01, p=0.008). Kaplan-Meier curves showed that 1-year event-free survival was significantly better amongst patients with normal SVRI, compared to patients with impaired inotropic reserve. Notably, HFrEF patients with an abnormal SVRI had a poor 1-year prognosis regardless of their peak VO 2 . Conclusions: SVRI is a non-invasive measurement that provides a measure of inotropic reserve at submaximal exercise, provides valuable prognostic information independent of other known and validated CPET parameters, and may predict deterioration in HFrEF patients more accurately than currently recommended CPET predictors. SVRI and peak VO 2 provide complementary prognostic information.

Thermal runaway behavior of lithium‐ion batteries in different charging states under low pressure

SummaryTo investigate the thermal safety behavior of lithium‐ion batteries during the air transportation process, the batteries with different states of charge (SOC) are heated by heating coil under low pressure. The thermal runaway (TR) behaviors of the batteries are investigated by analyzing the differences in TR phenomenon, temperature, time, and voltage. The results show that the voltage drop time is earlier than the gas release time for all the batteries. The increase in the SOC shortens the voltage drop and TR time, and increases the TR temperature and intensity of the batteries under all pressures. In addition, the reduction of pressure leads to the delay of voltage drop time, the reduction of TR intensity and temperature, and the U‐shaped change of TR time. The influence of SOC on the TR behavior is attributed to the difference of lithium content in the anode which leads to the difference in the energy state and stability of the battery. The difference in TR behavior under different pressures is due to the difference in oxygen content and heat transfer efficiency, which affects the ignition time and combustion behavior of the battery.

Study on mechanism of differential concentration corrosion

The pipeline easily gets corroded in a seawater environment. The oxygen in the seawater is one of major parameters causing the corrosion. In practice, the corrosion due to the oxygen concentration difference, i.e. differential concentration corrosion (DCC), cannot be avoided. However, a one-dimensional DCC model cannot satisfactorily predict the corrosion because the oxygen distribution near the pipe wall is two-dimensional. In this regard, a two-dimensional DCC model was proposed in this study to numerically investigate the distribution of corrosion potential and current in the ionic conductive layer near the pipe wall as well as the overall corrosion current. The results show that DCC plays a significant role in determining the corrosion potential and current. Without considering DCC, a large corrosion potential and current exist at the location with high oxygen concentration near the pipe wall, whereas the occurrence of the low corrosion potential and current corresponds to the location with low oxygen concentration. However, as DCC is considered, at the location with high corrosion potential, cathodic polarization was produced and the corrosion rate decreases; at the location with low corrosion potential, anodic polarization was produced and the corrosion rate increases. In general, the corrosion potential can be homogenized in terms of DCC.

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

Regional venous\u2013arterial CO2 to arterial\u2013venous O2 content difference ratio in experimental circulatory shock and hypoxia

BackgroundVenous–arterial carbon dioxide (CO2) to arterial–venous oxygen (O2) content difference ratio (Cv-aCO2/Ca-vO2) > 1 is supposed to be both sensitive and specific for anaerobic metabolism. What regional hemodynamic and metabolic parameters determine the ratio has not been clarified.ObjectivesTo address determinants of systemic and renal, spleen, gut and liver Cv-aCO2/Ca-vO2.MethodsPost hoc analysis of original data from published experimental studies aimed to address effects of different fluid resuscitation strategies on oxygen transport, lactate metabolism and organ dysfunction in fecal peritonitis and endotoxin infusion, and from animals in cardiac tamponade or hypoxic hypoxia. Systemic and regional hemodynamics, blood flow, lactate uptake, carbon dioxide and oxygen-derived variables were determined. Generalized estimating equations (GEE) were fit to assess contributors to systemic and regional Cv-aCO2/Ca-vO2.ResultsMedian (range) of pooled systemic Cv-aCO2/Ca-vO2 in 64 pigs was 1.02 (0.02 to 3.84). While parameters reflecting regional lactate exchange were variably associated with the respective regional Cv-aCO2/Ca-vO2 ratios, only regional ratios were independently correlated with systemic ratio: renal Cv-aCO2 /Ca-vO2 (β = 0.148, 95% CI 0.062 to 0.234; p = 0.001), spleen Cv-aCO2/Ca-vO2 (β = 0.065, 95% CI 0.002 to 0.127; p = 0.042), gut Cv-aCO2/Ca-vO2 (β = 0.117, 95% CI 0.025 to 0.209; p = 0.013), liver Cv-aCO2/Ca-vO2 (β = − 0.159, 95% CI − 0.297 to − 0.022; p = 0.023), hepatosplanchnic Cv-aCO2/Ca-vO2 (β = 0.495, 95% CI 0.205 to 0.786; p = 0.001).ConclusionIn a mixed set of animals in different shock forms or during hypoxic injury, hepatosplanchnic Cv-aCO2/Ca-vO2 ratio had the strongest independent association with systemic Cv-aCO2/Ca-vO2, while no independent association was demonstrated for lactate or hemodynamic variables.

Inhaled Molgramostim Therapy in Autoimmune Pulmonary Alveolar Proteinosis

BackgroundAutoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease characterized by progressive surfactant accumulation and hypoxemia. It is caused by disruption of granulocyte–macrophage colony-stimulating factor (GM-CSF) signaling, which pulmonary alveolar macrophages require to clear surfactant. Recently, inhaled GM-CSF was shown to improve the partial pressure of arterial oxygen in patients with aPAP.MethodsIn a double-blind, placebo-controlled, three-group trial, we randomly assigned patients with aPAP to receive the recombinant GM-CSF molgramostim (300 μg once daily by inhalation), either continuously or intermittently (every other week), or matching placebo. The 24-week intervention period was followed by an open-label treatment-extension period. The primary end point was the change from baseline in the alveolar–arterial difference in oxygen concentration (A-aDo2) at week 24.ResultsIn total, 138 patients underwent randomization; 46 were assigned to receive continuous molgramostim, 45 to receive intermittent molgramostim, and 47 to receive placebo. Invalid A-aDo2 data for 4 patients (1 in each molgramostim group and 2 in the placebo group) who received nasal oxygen therapy during arterial blood gas measurement were replaced by means of imputation. For the primary end point — the change from baseline in the A-aDo2 at week 24 — improvement was greater among patients receiving continuous molgramostim than among those receiving placebo (−12.8 mm Hg vs. −6.6 mm Hg; estimated treatment difference, −6.2 mm Hg; P=0.03 by comparison of least-squares means). Patients receiving continuous molgramostim also had greater improvement than those receiving placebo for secondary end points, including the change from baseline in the St. George’s Respiratory Questionnaire total score at week 24 (−12.4 points vs. −5.1 points; estimated treatment difference, −7.4 points; P=0.01 by comparison of least-squares means). For multiple end points, improvement was greater with continuous molgramostim than with intermittent molgramostim. The percentages of patients with adverse events and serious adverse events were similar in the three groups, except for the percentage of patients with chest pain, which was higher in the continuous-molgramostim group.ConclusionsIn patients with aPAP, daily administration of inhaled molgramostim resulted in greater improvements in pulmonary gas transfer and functional health status than placebo, with similar rates of adverse events. (Funded by Savara Pharmaceuticals; IMPALA ClinicalTrials.gov number, NCT02702180.)

Paramètres dérivés du CO2 pour évaluer l’état hémodynamique chez le malade de réanimation

Le dioxyde de carbone (CO2) constitue le produit de dégradation final du métabolisme cellulaire. Plusieurs gradients de CO2, obtenus grâce à la mesure de la pression partielle de CO2 (PCO2) dans différents compartiments, sont utilisés afin d’évaluer l’état circulatoire des patients de réanimation. Au cours d’un état de choc, l’augmentation de la PCO2 veineuse et tissulaire est principalement la conséquence d’une hypoperfusion tissulaire et non d’une hypoxémie, reflétant ainsi une anomalie macro et/ou microcirculatoire. Un gradient veino-artériel de PCO2 (Pv-aCO2) ≥ 6 mmHg peut suggérer une inadéquation du débit cardiaque. À l’échelle locale, un gradient tissu-artériel en PCO2 (Pt-aCO2) élevé malgré un Pv-aCO2 normal (&lt; 6 mmHg) peut faire évoquer une atteinte de la microcirculation locale. Enfin, un indice combiné des paramètres dérivés du CO2 et de l’O2, comme le rapport entre le Pv-aCO2 et la différence des contenus artériel et veineux en oxygène (Pv-aCO2 / CaO2 – CvO2), suggère une hypoxie tissulaire lorsqu’il dépasse 1,4. Chez les patients de réanimation en insuffisance circulatoire, les paramètres dérivés du CO2 doivent toutefois s’intégrer dans une approche multiparamétrique (examen clinique, marqueurs biologiques, échocardiographie et autres outils hémodynamiques).

Hemodynamic monitoring with two blood gases: “a tool that does not go out of style”

Introduction. Hemodynamic monitoring of a critically ill patient is an indispensable tool both inside and outside intensive care; we currently have invasive, minimally invasive and non-invasive devices; however, no device has been shown to have a positive impact on the patient's evolution; arterial and venous blood gases provide information on the patient's actual microcirculatory and metabolic status and may be a hemodynamic monitoring tool.&#x0D; Objective. To carry out a non-systematic review of the literature of hemodynamic monitoring carried out through the variables obtained in arterial and venous blood gases.&#x0D; Material and methods. A non-systematic review of the literature was performed in the PubMed, OvidSP and ScienceDirect databases with selection of articles from 2000 to 2019.&#x0D; Results. It was found that there are variables obtained in arterial and venous blood gases such as central venous oxygen saturation (SvcO2), venous-to-arterial carbon dioxide pressure (∆pv-aCO2), venous-to-arterial carbon dioxide pressure/arteriovenous oxygen content difference (∆pv-aCO2/∆Ca-vO2) that are related to cellular oxygenation, cardiac output (CO), microcirculatory veno-arterial flow and anaerobic metabolism and allow to assess tissue perfusion status.&#x0D; Conclusion. The variables obtained by arterial and venous blood gases allow for non-invasive, accessible and affordable hemodynamic monitoring that can guide medical decision-making in critically ill patients.