Search Results (16)

Oxygen therapy is a cornerstone in the treatment of critically ill patients. However, excess oxygen administration may promote oxidative cellular injury once hemoglobin is fully saturated and additional oxygen remains dissolved, enhancing reactive oxygen species formation. The combined impact of oxygen administration, pH, and respiratory failure on hyperoxemia across saturation ranges is not well understood. We conducted a retrospective study at a tertiary center to assess how these factors modify hyperoxemia frequency in adult ICU patients. Continuous S_pO₂ measurements were aligned with arterial blood gases (P_aO₂, pH, F_iO₂), and hyperoxemia was evaluated using predefined P_aO₂ thresholds (>120 mmHg and >150 mmHg). Among 21,406 patients with 717,064 paired measurements, prolonged hyperoxemia occurred in over half of mechanically ventilated patients, most commonly in those without or with mild-to-moderate respiratory failure. Acidotic states were associated with higher P_aO₂ values at comparable S_pO₂ levels, consistent with a rightward shift in the oxygen–hemoglobin dissociation curve. S_pO₂ values ≥ 98% were consistently associated with hyperoxemia, whereas 96–97% generally corresponded to P_aO₂ within physiological ranges. Higher F_iO₂ markedly increased hyperoxemia probability, allowing derivation of pH-stratified F_iO₂ exposure limits. Our findings highlight the importance of individualized oxygen therapy, considering pH and respiratory failure phenotype to guide safer oxygen management. Full article

Hemolysis rate is usually used as the acceptance criterion for stored red blood cells (RBCs) in clinical practice. However, there is a current lack of parameters for the characterization of hemoglobin quality. This study aimed to incorporate oxygen affinity, cooperativity, and the Bohr effect into a parameter system to monitor oxygen supply efficiency in stored RBCs, potentially serving as a basis for quality assessment. Han Chinese blood from plains, Tibetan blood from plateau, bovine hemoglobin (bHb), and a dextran–bovine hemoglobin conjugate (Dex20-bHb) were analyzed using the BLOODOX-2018. Oxygen affinity (P₅₀) was determined by oxygen dissociation curves (ODCs) at pH = 7.4. Cooperativity was assessed through the Hill coefficient, calculated from the fitting range of the Hill equation. The Bohr effect was evaluated by the acid-base sensitivity index (SI) under simulated pH conditions of the lungs (pH = 7.6) and tissues (pH = 7.2) to calculate corresponding P₅₀ values. Oxygen partial pressures (PO₂) simulating lungs (PO₂ = 100 mmHg for plains and 60 mmHg for plateau) and tissues (PO₂ = 40 mmHg for plains and 30 mmHg for plateau) were used to calculate theoretical oxygen-release capacities in both environments. Multiple regression analysis explored relationships among parameters, constructing a system to assess changes in rat RBCs during storage. Optimized test methods determined P₅₀, Hill coefficient, SI, and theoretical oxygen-release capacities for Han Chinese blood, Tibetan blood, bHb, and Dex20-bHb samples in various environments. We constructed a parameter system to characterize blood’s oxygen supply efficiency, revealing the significant influence of the Bohr effect. This influence varied with environmental changes in oxygen affinity. We validated the system using stored rat RBCs, finding consistent P₅₀ trends with predictions, and initial increases in Hill coefficient and SI followed by decreases. Theoretical oxygen-release capacities varied significantly between plateau and plain environments. These results support using oxygen supply efficiency to assess RBC storage quality for developing transfusion strategies. P₅₀, Hill coefficient, SI, and theoretical oxygen-release capacity in different environments can be incorporated into blood oxygen supply efficiency characterization systems to assess the quality changes in RBCs during storage. Full article

One of the major factors currently hindering the development of hemoglobin-based oxygen carriers (HBOCs) is the autoxidation of hemoglobin to inactive methemoglobin (MetHb). The effects of spermine on the stability, aggregation, structure, and function of adult hemoglobin (HbA) were studied. The interaction of spermine with HbA was elucidated by dynamic light scattering, colloid osmotic pressure measurements, thermal denaturation analysis, static light scattering, and oxygen dissociation assay. The antioxidant capacity of spermine was confirmed through UV–vis spectroscopic recordings, calculations of MetHb formation, and hydroxyl radical scavenging. The P50 value was determined by the oxygen dissociation curve to investigate the roles of spermine in increasing HbA’s oxygen affinity. The pH-dependent affinity between spermine and HbA was validated through surface plasmon resonance experiments. The transformation of HbA’s partial α-helix to a β-sheet structure induced by spermine was clarified using a microfluidic modulation spectrometer. The binding of spermine to βASP99, βGLU101, αTHR38, and αASN97 on HbA and the conformational shift in HbA towards the ‘R’ state were investigated via molecular docking and molecular dynamics simulations. In a word, spermine can enhance the oxygen affinity of HbA, effectively reduce autoxidation, and hold promise for applications in the research of HBOCs or hemoglobin modification. Full article

Background: Hemoglobin Rothschild (Hb Rothschild), NM_000518.5(HBB):c.112T>C, is an ultra-rare low-oxygen-affinity hemoglobin variant that persistently causes reduced peripheral oxygen saturation on pulse oximetry despite normal arterial oxygenation. Fewer than ten cases have been reported worldwide, and only one involved a child—an asymptomatic carrier identified incidentally. Methods: The patient underwent clinical examination, growth assessment, blood tests, hemoglobin electrophoresis, chest CT, abdominal ultrasound, echocardiography, and pulmonary perfusion scintigraphy. Whole genome sequencing (WGS) of the proband and parents was performed, followed by bioinformatic analysis and ACMG-based variant interpretation. A PRISMA-guided PubMed literature review was conducted. Results: We report on the first pediatric case exhibiting a symptomatic clinical course. A 4-year-old boy was referred for chronically low peripheral oxygen saturation (SpO₂), 78–86%, on pulse oximetry and recurrent lower respiratory tract infections. Early developmental history revealed episodes of apnea in infancy, perioral cyanosis, poor exercise tolerance, and low weight gain. Repeated cardiopulmonary assessments, chest computed tomography (CT), echocardiography, and pulmonary perfusion scintigraphy yielded unremarkable findings. Arterial blood gas analysis consistently showed normal arterial partial pressure of oxygen (PaO₂), excluding true hypoxemia. Hemoglobin electrophoresis revealed an abnormal HbD fraction; WGS identified a heterozygous variant NM_000518.5(HBB):c.112T>C inherited from the patient’s asymptomatic father. This variant increases the partial pressure of oxygen at which hemoglobin is 50% saturated (p50), thereby decreasing hemoglobin’s oxygen affinity and shifting the oxyhemoglobin dissociation curve to the right. These alterations explain the discordance between low peripheral oxygen saturation (SpO₂) and preserved oxygen delivery to tissues. Conclusions: This case expands the clinical spectrum of Hb Rothschild and demonstrates that symptomatic presentation may occur in early childhood. Awareness of low-affinity hemoglobin variants is essential to avoid misdiagnosis and unnecessary cardiopulmonary interventions. Early genetic testing facilitates accurate diagnosis and appropriate counseling. Full article

During the exposure of biological tissue to an external heat impulse (both controlled as in various types of thermotherapy and uncontrolled related to thermal burns), processes occur related to changes in its parameters, especially perfusion, and thus the transport of oxygen to the tissue. This paper presents a combined model of bioheat transfer and oxygen distribution in tissue. The latter was based on Krogh’s cylinder concept, taking into account the Hill oxygen dissociation curve. The variable value of the perfusion coefficient is shown to affect the value of blood velocity in the capillary and, therefore, the distribution of partial pressure in the tissue. A sensitivity analysis was performed for the oxygen distribution model using the direct method for seven parameters present in its mathematical description. The results show that a 10% change in the values of all parameters leads to changes in the partial oxygen pressure exceeding 8 mmHg, and for the reduced value of the oxygen inlet pressure, the largest changes in the partial oxygen pressure within the Krogh cylinder model occur near the outlet capillary. In the stage of numerical realization, the finite difference method and the shooting method were used. Full article

Background: The ability of hemoglobin to bind and dissociate oxygen is crucial in delivering oxygen to tissues and is influenced by a range of physiological states, compensatory mechanisms, and pathological conditions. This may be illustrated by the oxyhemoglobin dissociation curve (ODC). The key parameter for evaluating the oxygen affinity to hemoglobin is p50. The aim of this study was to evaluate the impact of hemodialysis on p50 in a group of patients with chronic kidney disease (CKD). An additional goal was to assess the correlation between p50 and the parameters of erythropoiesis, point-of-care testing (POCT), and other laboratory parameters. Methods: One hundred and eighty patients (106 male, 74 female), mean age 62.5 ± 17 years, with CKD stage G4 and G5 were enrolled in this cross-sectional study. Patients were divided into two groups, including 65 hemodialysis (HD) patients and 115 patients not receiving dialysis (non-HD). During the standard procedure of arteriovenous fistula creation, blood samples from the artery (A) and the vein (V) were taken for POCT. The causes of CKD, as well as demographic and comorbidity data, were obtained from medical records and direct interviews. Results: The weekly dose of erythropoietin was higher in HD patients than in non-HD patients (4914 ± 2253 UI vs. 403 ± 798 UI, p < 0.01), but hemoglobin levels did not differ between these groups. In the group of non-HD patients, more advanced metabolic acidosis (MA) was found, compared to the group with HD. In arterial and venosus blood samples, the non-HD group had significantly lower pH, pCO₂ and HCO₃⁻. This group had a higher proportion of individuals with MA with HCO₃⁻ < 22 mmol/L (42% vs. 24%, p < 0.01). The absolute difference of p50 in arterial and venous blood was determined using the formula Δp50 = (p50-A) − (p50-V). Δp50 was significantly higher in the HD group in comparison to non-HD (0.08 ± 2.05 mmHg vs. −0.66 ± 1.93 mmHg, p = 0,02). There was a negative correlation between pH and the p50 value in arterial (pH-A vs. p50-A, r = −0.56, p < 0.01) and venous blood (pH-V vs. p50-V, r = −0.45, p < 0.01). In non-HD patients, hemoglobin levels correlated negatively with p50 (r = −0.29, p < 0.01), whereas no significant relation was found in HD patients. Conclusions: The ODC in pre-dialysis CKD (non-HD) patients is shifted to the right due to MA, and this is an additional factor influencing erythropoiesis. Hemodialysis restores the natural differences in hemoglobin’s dissociation characteristics in the arterial and venous circulation. Full article

The energy transition from hydrocarbon-based energy sources to renewable and carbon-free energy sources such as wind, solar and hydrogen is facing increasing demands. The decarbonization of global transportation could come true via applying carbon-free fuel such as ammonia, especially for internal combustion engines (ICEs). Although ammonia has advantages of high hydrogen content, high octane number and safety in storage, it is uninflammable with low laminar burning velocity, thus limiting its direct usage in ICEs. The purpose of this review paper is to provide previous studies and current research on the current technical advances emerging in assisted combustion of ammonia. The limitation of ammonia utilization in ICEs, such as large minimum ignition energy, lower flame speed and more NO_x emission with unburned NH₃, could be solved by oxygen-enriched combustion, ammonia–hydrogen mixed combustion and plasma-assisted combustion (PAC). In dual-fuel or oxygen-enriched NH₃ combustion, accelerated flame propagation speeds are driven by abundant radicals such as H and OH; however, NOx emission should be paid special attention. Furthermore, dissociating NH₃ in situ hydrogen by non-noble metal catalysts or plasma has the potential to replace dual-fuel systems. PAC is able to change classical ignition and extinction S-curves to monotonic stretching, which makes low-temperature ignition possible while leading moderate NO_x emissions. In this review, the underlying fundamental mechanism under these technologies are introduced in detail, providing new insight into overcoming the bottleneck of applying ammonia in ICEs. Finally, the feasibility of ammonia processing as an ICE power source for transport and usage highlights it as an appealing choice for the link between carbon-free energy and power demand. Full article

According to Fick’s principle, the total uptake of (or release of) a substance by tissues is the product of blood flow and the difference between the arterial and the venous concentration of the substance. Therefore, the mixed or central venous minus arterial CO₂ content difference depends on cardiac output (CO). Assuming a linear relationship between CO₂ content and partial pressure, central or mixed venous minus arterial PCO₂ differences (P_cv-aCO₂ and P_mv-aCO₂) are directly related to CO. Nevertheless, this relationship is affected by alterations in the CO₂Hb dissociation curve induced by metabolic acidosis, hemodilution, the Haldane effect, and changes in CO₂ production (VCO₂). In addition, P_cv-aCO₂ and P_mv-aCO₂ are not interchangeable. Despite these confounders, CO is a main determinant of P_cv-aCO₂. Since in a study performed in septic shock patients, P_mv-aCO₂ was correlated with changes in sublingual microcirculation but not with those in CO, it has been proposed as a monitor for microcirculation. The respiratory quotient (RQ)—RQ = VCO₂/O₂ consumption—sharply increases in anaerobic situations induced by exercise or critical reductions in O₂ transport. This results from anaerobic VCO₂ secondary to bicarbonate buffering of anaerobically generated protons. The measurement of RQ requires expired gas analysis by a metabolic cart, which is not usually available. Thus, some studies have suggested that the ratio of P_cv-aCO₂ to arterial minus central venous O₂ content (P_cv-aCO₂/C_a-cvO₂) might be a surrogate for RQ and tissue oxygenation. In this review, we analyze the physiologic determinants of P_cv-aCO₂ and P_cv-aCO₂/C_a-cvO₂ and their potential usefulness and limitations for the monitoring of critically ill patients. We discuss compelling evidence showing that they are misleading surrogates for tissue perfusion and oxygenation, mainly because they are systemic variables that fail to track regional changes. In addition, they are strongly dependent on changes in the CO₂Hb dissociation curve, regardless of changes in systemic and microvascular perfusion and oxygenation. Full article

Oxygen binds to hemoglobin cooperatively, and a correct description of this binding is relevant not only for understanding the mechanisms of involved molecular processes but also for clinical purposes. Hill’s equation, derived over a hundred years ago, is still the simplest and most efficient way to perform this description. However, in terms of accuracy, it is inferior to Adair´s equation, which contains more parameters. We proposed to use a modified Hill equation and showed that it allows a more accurate description of the binding of oxygen to hemoglobin than Adair’s equation. At the same time, unlike Adair’s equation, our model retains the physical meaning given to the original Hill equation. We considered and analyzed the influence of the equation parameters on the course of the oxygenation curve and presented the relationship between the fitting parameters and other parameters derived from them in the form of a diagram-graph, which, in our opinion, simplifies the perception of these estimates and can be useful in solving a number of problems for which the traditional way of analyzing the degree of cooperative interaction was via the Hill equation. We suggest that the newly proposed parameter h_max introduced in our model should be regarded as crucial for a better description of the oxygenation curve. Full article

High oxygen affinity hemoglobin (HOAH) is the main cause of constitutional erythrocytosis. Mutations in the genes coding the alpha and beta globin chains (HBA1, HBA2 and HBB) strengthen the binding of oxygen to hemoglobin (Hb), bringing about tissue hypoxia and a secondary erythrocytosis. The diagnosis of HOAH is based upon the identification of a mutation in HBA1, HBA2 or HBB in specialized laboratories. Phenotypic studies of Hb are also useful, but electrophoretic analysis can be normal in 1/3 of cases. The establishment of the dissociation curve of Hb can be used as another screening test, a shift to the left indicating an increased affinity for Hb. The direct measurement of venous P50 using a Hemox Analyzer is of great importance, but due to specific analytic conditions, it is only available in a few specialized laboratories. Alternatively, an estimated measurement of the P50 can be obtained in most of the blood gas analyzers on venous blood. The aim of our study was therefore to determine whether a normal venous P50 value could rule out HOAH. We sequenced the HBB, HBA1 and HBA2 genes of 75 patients with idiopathic erythrocytosis. Patients had previously undergone an exhaustive medical check-up after which the venous P50 value was defined as normal. Surprisingly, sequencing detected HOAH in three patients (Hb Olympia in two patients, and Hb St Nazaire in another). A careful retrospective examination of their medical files revealed that (i) one of the P50 samples was arterial; (ii) there was some air in another sample; and (iii) the P50 measurement was not actually done in one of the patients. Our study shows that in real life conditions, due to pre-analytical contingencies, a venous P50 value that is classified as being normal may not be sufficient to rule out a diagnosis of HOAH. Therefore, we recommend the systematic sequencing of the HBB, HBA1 and HBA2 genes in the exploration of idiopathic erythrocytosis. Full article

5-Hydroxymethylfurfural (5-HMF) is known to increase hemoglobin oxygen affinity (Hb–O₂ affinity) and to induce a left shift of the oxygen dissociation curve (ODC). It is under investigation as a therapeutic agent in sickle cell anemia and in conditions where pulmonary oxygen uptake is deteriorated or limited (e.g., various clinical conditions or altitude exposure). The combination of 5-HMF and α-ketoglutaric acid (αKG) is commercially available as a nutritional supplement. To further elucidate dose effects, ODCs were measured in vitro in venous whole blood samples of 20 healthy volunteers (10 female and 10 male) after the addition of three different doses of 5-HMF, αKG and the combination of both. Linear regression analysis revealed a strong dose-dependent increase in Hb–O₂ affinity for 5-HMF (R² = 0.887; p < 0.001) and the commercially available combination with αKG (R² = 0.882; p < 0.001). αKG alone increased Hb–O₂ affinity as well but to a lower extent. Both the combination (5-HMF + αKG) and 5-HMF alone exerted different P50 and Hill coefficient responses overall and between sexes, with more pronounced effects in females. With increasing Hb–O₂ affinity, the sigmoidal shape of the ODC was better preserved by the combination of 5-HMF and αKG than by 5-HMF alone. Concerning the therapeutic effects of 5-HMF, this study emphasizes the importance of adequate dosing in various physiological and clinical conditions, where a left-shifted ODC might be beneficial. By preserving the sigmoidal shape of the ODC, the combination of 5-HMF and αKG at low (both sexes) and medium (males only) doses might be able to better maintain efficient oxygen transport, particularly by mitigating potentially deteriorated oxygen unloading in the tissue. However, expanding knowledge on the interaction between 5-HMF and Hb–O₂ affinity in vitro necessitates further investigations in vivo to additionally assess pharmacokinetic mechanisms. Full article

The role of ZrO₂ as different components in Ni-based catalysts for CO₂ reforming of methane (CRM) has been investigated. The 10 wt.% Ni supported catalysts were prepared with ZrO₂ as a support using a co-impregnation method. As a promoter (1 wt.% ZrO₂) and a coactive component (10 wt.% ZrO₂), the catalysts with ZrO₂ were synthesized using a co-impregnation method. To evaluate the effect of the interaction, the Ni catalyst with ZrO₂ as a coactive component was prepared by a sequential impregnation method. The results revealed that the activity, the selectivity, and the anti-coking ability of the catalyst depend upon the ZrO₂ content, the Ni-ZrO₂ interaction, basicity, and oxygen mobility of each catalyst resulting in different Ni dispersion and oxygen transfer pathway from ZrO₂ to Ni. According to the characterization and catalytic activation results, the Ni catalyst with low ZrO₂ content (as a promoter) presented highest selectivity toward CO owning to the high number of weak and moderate basic sites that enhance the CO₂ activation-dissociation. The lowest activity (CH₄ conversion ≈ 40% and CO₂ conversion ≈ 39%) with the relatively high quantity of total coke formation (the weight loss of the spent catalyst in TGA curve ≈ 22%) of the Ni catalyst with ZrO₂ as a support is ascribed to the lowest Ni dispersion due to the poor Ni-ZrO₂ interaction and less oxygen transfer from ZrO₂ to the deposited carbon on the Ni surface. The effect of a poor Ni-ZrO₂ interaction on the catalytic activity was deducted by decreasing ZrO₂ content to 10 wt.% (as a coactive component) and 1 wt.% (as a promoter). Although Ni catalysts with 1 wt.% and 10 wt.% ZrO₂ provided similar oxygen mobility, the lack of oxygen transfer to coke during CRM process on the Ni surface was still indicated by the growth of carbon filament when the catalyst was prepared by co-impregnation method. When the catalyst was prepared by a sequential impregnation, the intimate interaction of Ni and ZrO₂ for oxygen transfer was successfully developed through a ZrO₂-Al₂O₃ composite. The interaction in this catalyst enhanced the catalytic activity (CH₄ conversion ≈ 54% and CO₂ conversion ≈ 50%) and the oxygen transport for carbon oxidation (the weight loss of the spent catalyst in TGA curve ≈ 7%) for CRM process. The Ni supported catalysts with ZrO₂ as a promoter prepared by co-impregnation and with ZrO₂ as a coactive component prepared by a sequential impregnation were tested in combined steam and CO₂ reforming of methane (CSCRM). The results revealed that the ZrO₂ promoter provided a greater carbon resistance (coke = 1.213 mmol·g⁻¹) with the subtraction of CH₄ and CO₂ activities (CH₄ conversion ≈ 28% and CO₂ conversion ≈ %) due to the loss of active sites to the H₂O activation-dissociation. Thus, the H₂O activation-dissociation was promoted more efficiently on the basic sites than on the vacancy sites in CSCRM. Full article

The utility of measuring whole-animal performance to frame the metabolic response to environmental hypoxia is well established. Progressively reducing ambient oxygen (O₂) will initially limit maximum metabolic rate as a result of a hypoxemic state and ultimately lead to a time-limited, tolerance state supported by substrate-level phosphorylation when the O₂ supply can no longer meet basic needs (standard metabolic rate, SMR). The metabolic consequences of declining ambient O₂ were conceptually framed for fishes initially by Fry’s hypoxic performance curve, which characterizes the hypoxemic state and its consequences to absolute aerobic scope (AAS), and Hochachka’s concept of scope for hypoxic survival, which characterizes time-limited life when SMR cannot be supported by O₂ supply. Yet, despite these two conceptual frameworks, the toolbox to assess whole-animal metabolic performance remains rather limited. Here, we briefly review the ongoing debate concerning the need to standardize the most commonly used assessments of respiratory performance in hypoxic fishes, namely critical O₂ (the ambient O₂ level below which maintenance metabolism cannot be sustained) and the incipient lethal O₂ (the ambient O₂ level at which a fish loses the ability to maintain upright equilibrium), and then we advance the idea that the most useful addition to the toolbox will be the limiting-O₂ concentration (LOC) performance curve. Using Fry & Hart’s (1948) hypoxia performance curve concept, an LOC curve was subsequently developed as an eco-physiological framework by Neil et al. and derived for a group of fish during a progressive hypoxia trial by Claireaux and Lagardère (1999). In the present review, we show how only minor modifications to available respirometry tools and techniques are needed to generate an LOC curve for individual fish. This individual approach to the LOC curve determination then increases its statistical robustness and importantly opens up the possibility of examining individual variability. Moreover, if peak aerobic performance at a given ambient O₂ level of each individual is expressed as a percentage of its AAS, the water dissolved O₂ that supports 50% of the individual’s AAS (DO_AAS-50) can be interpolated much like the P₅₀ for an O₂ hemoglobin dissociation curve (when hemoglobin is 50% saturated with O₂). Thus, critical O₂, incipient lethal O₂, DO_AAS-50 and P₅₀ and can be directly compared within and across species. While an LOC curve for individual fish represents a start to an ongoing need to seamlessly integrate aerobic to anaerobic capacity assessments in a single, multiplexed respirometry trial, we close with a comparative exploration of some of the known whole-organism anaerobic and aerobic capacity traits to examine for correlations among them and guide the next steps. Full article

Continuous monitoring of arterial oxygen saturation by pulse oximetry (SpO2) is the main method to guide respiratory and oxygen support in neonates during postnatal stabilization and after admission to neonatal intensive care unit. The accuracy of these devices is therefore crucial. The presence of fetal hemoglobin (HbF) in neonatal blood might affect SpO2 readings. We performed a systematic qualitative review to investigate the impact of HbF on SpO2 accuracy in neonates. PubMed/Medline, Embase, Cumulative Index to Nursing & Allied Health database (CINAHL) and Cochrane library databases were searched from inception to January 2021 for human studies in the English language, which compared arterial oxygen saturations (SaO2) from neonatal blood with SpO2 readings and included HbF measurements in their reports. Ten observational studies were included. Eight studies reported SpO2-SaO2 bias that ranged from −3.6%, standard deviation (SD) 2.3%, to +4.2% (SD 2.4). However, it remains unclear to what extent this depends on HbF. Five studies showed that an increase in HbF changes the relation of partial oxygen pressure (paO2) to SpO2, which is physiologically explained by the leftward shift in oxygen dissociation curve. It is important to be aware of this shift when treating a neonate, especially for the lower SpO2 limits in preterm neonates to avoid undetected hypoxia. Full article

β-Carotene (β-Crt) can be dispersed in hydrophobic regions of the membrane of red blood cells (RBC). Its location, orientation and distribution strongly depend on carotenoid concentration. In the present pilot trial (six human subjects involved), it is demonstrated that incubation of RBCs with β-Crt (1.8 × 10⁷ β-Crt molecules per RBC, 50 μmol/L) results in expansion of the membrane of RBCs and slight elongation of the cell. The changes are of statistical significance, as verified by the Wilcoxon test at p < 0.05. They indicate (i) a highly random orientation and location of β-Crt inside the membrane and (ii) a tendency for its interaction with membrane skeleton proteins. The accompanying effect of decreased RBC resistance to lysis is possibly a result of the incorrect functioning of ion channels due to their modification/disruption. At higher β-Crt concentrations, its clustering inside membranes may occur, leading to further alterations in the shape and size of RBCs, with the most pronounced changes observed at 1.8 × 10⁸ β-Crt molecules per RBC (500 μmol/L). Due to the reduced permeability of ions, such membranes exhibit increased resistance to haemolysis. Finally, we show that interactions of β-Crt with the membrane of RBCs lead to an alteration in haemoglobin-oxygen affinity, shifting the oxyhaemoglobin dissociation curve toward higher oxygen partial pressures. If the impact of β-Crt on a curve course is confirmed in vivo, one may consider its role in the fine tuning of O₂ transportation to tissues. Hence, at low concentrations, providing unchanged elastic and functional properties of RBCs, it could serve as a beneficial agent in optimising heart performance and cardiovascular load. Full article