Respiratory Gas Research Articles

Relationship between Longitudinal Upper Body Rotation and Energy Cost of Running in Junior Elite Long-Distance Runners.

Running is a basic form of human locomotion and one of the most popular sports worldwide. While the leg biomechanics of running have been studied extensively, few studies have focused on upper-body movement. However, an effective arm swing and longitudinal rotation of the shoulders play an important role in running efficiency as they must compensate for the longitudinal torques generated by the legs. The aim of this study is to assess the upper-body rotation using wearable inertial sensors and to elucidate its relation to energy expenditure. Eighty-six junior elite middle- and long-distance runners (37 female, 49 male) performed an incremental treadmill test with sensors attached on both shoulders, tibiae and the sacrum. The mean and total horizontal shoulder and pelvis rotations per stride were derived while energy costs were determined using respiratory gas analysis and blood sampling. Results show that shoulder and pelvis rotations increase with running speed. While shoulder rotation is more pronounced in female than in male runners, there is no sex difference for pelvis rotation. The energy cost of running and upper trunk rotation prove to be slightly negatively correlated. In conclusion, upper body rotation appears to be an individual characteristic influenced by a sex-specific body mass distribution.

Experimental investigation of effect of ventilation strategies on the performance of cold storage

AbstractFresh fruits and vegetables are living organisms that require fresh air to survive while being stored. Respiratory gases can build up and damage produce if there is not enough ventilation during storage. Ventilation is required to prevent an excessive build‐up of respiratory gases and to maintain the freshness of produce. In hot and dry areas, air ventilation of refrigerated storage can have a negative impact on food produce quality and affect storage performance. An indoor experimental study was carried out to investigate the air ventilation of the cold room during various modes of air supply. The energy recovery device (ERD) with and without evaporative cooling arrangement is used in the air supply and the performance enhancement is compared. The ERD reduces the air ventilation load by more than 50% compared to direct ventilation of the cold room and consequently, it reduces the total power consumption of air ventilation. Furthermore, the overall cooling performance of the system is improved by up to 45.7% when the ERDs are used compared to the direct supply of fresh air during air change mode and the use of energy‐saving equipment has also proven improvements in the desired air conditions for food production.

Effects of unpredictable chronic mild stress on the cellular redox state and mitochondrial energy homeostasis in rat adipose tissue: A comprehensive metabolic study.

Unpredictable chronic mild stress (UCMS) leads to variable metabolic effects. Oxidative stress (OS) of adipose tissue (AT) and mitochondrial energy homeostasis is little investigated. This work studied the effects of UCMS on OS and the antioxidant/redox status in AT and mitochondrial energy homeostasis in rats. Twenty-four male Wistar rats (180-220 g) were divided into two equal groups; the normal control (NC) group and the UCMS group which were exposed to various stresses for 28 days. An indirect calorimetry machine was used to measure volumes of respiratory gases (VO2 & VCO2 ), total energy expenditure (TEE), and food intake (FI). The AT depots were collected, weighed, and used for measuring activities and gene expression of key antioxidant enzymes (GPx1, SOD, CAT, GR, GCL, and GS), OS marker levels including superoxide anion (SA), peroxynitrite radical (PON), nitric oxide (NO), hydrogen peroxide (H2 O2 ), lipid peroxides (LPO), t-protein carbonyl content (PCC), and reduced/oxidized glutathione levels (GSH, GSSG). Additionally, AT mitochondrial fractions were used to determine the activities of the tricarboxylic acid cycle (TCA) cycle enzymes (CS, α-KGDH, ICDH, SDH, MDH), respiratory chain complexes I-III, II-III, IV, the nicotinamide coenzymes NAD+ , NADH, and ATP/ADP levels. Compared with the NC group, the UCMS group showed very significantly increased OS marker levels, lowered antioxidant enzyme activities and gene expression, as well as lowered TCA cycle and respiratory chain activity and NAD+ , NADH, and ATP levels (p < .001 for all comparisons). Besides, the UCMS group had lowered TEE and insignificant FI and weight gain. In conclusion, AT of the UCMS-subjected rats showed a state of disturbed redox balance linked to disrupted energy homeostasis producing augmentation of AT.

Feasibility of predicting maximal oxygen uptake by using the efficiency factor in healthy men

Conventionally, efficiency is indirectly estimated through a respiratory gas analyser (oxygen, carbon dioxide), which is a complex and rather costly calculation method that is difficult to perform in many situations. Therefore, the present study proposed a modified definition of efficiency, called the efficiency factor (EF) (i.e., the ratio of work to the corresponding exercise intensity), and evaluated the relation between the EF and maximal oxygen uptake ({dot{text{V}}text{O}}_{2max }), as well as compared the prediction models established based on the EF. The heart rate (maximal heart rate: 186 ± 6 beats min−1), rating of perceived exertion (19 ± 1), and {dot{text{V}}text{O}}_{2max } (39.0 ± 7.1 mL kg−1 min−1) of 150 healthy men (age: 20 ± 2 years; height: 175.0 ± 6.0 cm; weight: 73.6 ± 10.7 kg; body mass index [BMI]: 24.0 ± 3.0 kg m−2; percent body fat [PBF]: 17.0 ± 5.7%) were measured during the cardiopulmonary exercise test (CPET). Through multiple linear regression analysis, we established the BMI model using age and BMI as parameters. Additionally, we created the PBF modelHRR utilizing weight, PBF, and heart rate reserve (HRR) and developed PBF modelEF6 and PBF modelEF7 by incorporating EF6 from the exercise stage 6 and EF7 from the exercise stage 7 during the CPET, respectively. EF6 (r = 0.32, p = 0.001) and EF7 (r = 0.31, p = 0.002) were significantly related to {dot{text{V}}text{O}}_{2max }. Among the models, the PBF modelEF6 showed the highest accuracy, which could explain 62.6% of the variance in the {dot{text{V}}text{O}}_{2max } at with a standard error of estimate (SEE) of 4.39 mL kg−1 min−1 (%SEE = 11.25%, p < 0.001). These results indicated that the EF is a significant predictor of {dot{text{V}}text{O}}_{2max }, and compared to the other models, the PBF modelEF6 is the best model for estimating {dot{text{V}}text{O}}_{2max }.

Do air-breathing fish suffer branchial oxygen loss in hypoxic water?

In hypoxia, air-breathing fish obtain O2 from the air but continue to excrete CO2 into the water. Consequently, it is believed that some O2 obtained by air-breathing is lost at the gills in hypoxic water. Pangasionodon hypophthalmus is an air-breathing catfish with very large gills from the Mekong River basin where it is cultured in hypoxic ponds. To understand how P. hypophthalmus can maintain high growth in hypoxia with the presumed O2 loss, we quantified respiratory gas exchange in air and water. In severe hypoxia (PO2: ≈ 1.5 mmHg), it lost a mere 4.9% of its aerial O2 uptake, while maintaining aquatic CO2 excretion at 91% of the total. Further, even small elevations in water PO2 rapidly reduced this minor loss. Charting the cardiovascular bauplan across the branchial basket showed four ventral aortas leaving the bulbus arteriosus, with the first and second gill arches draining into the dorsal aorta while the third and fourth gill arches drain into the coeliacomesenteric artery supplying the gut and the highly trabeculated respiratory swim-bladder. Substantial flow changes across these two arterial systems from normoxic to hypoxic water were not found. We conclude that the proposed branchial oxygen loss in air-breathing fish is likely only a minor inefficiency.

Capnometry in the intensive care unit (literature review)

Capnometry/capnography is a method of measuring and displaying the concentration of carbon dioxide (CO2) in respiratory gases. Most often, this term involves measuring the partial pressure of carbon dioxide (PCO2) at the end of exhalation (end-tidal CO2, ETCO2). The curve formed during capnography is called a capnogram, where the inspiratory and expiratory segments are distinguished. The main determinants of ETCO2 are CO2 production, cardiac output, pulmonary perfusion, and alveolar ventilation. Normally, ETCO2 is 2–5 mm Hg lower than arterial blood PCO2. This gradient increases when the ventilation-perfusion ratio is impaired, for example, in pulmonary embolism or pulmonary hypoperfusion during cardiac arrest. The shape of the capnogram, in turn, depends on the concentration of CO2 in the alveoli and the pattern of their emptying, as well as on cardiac output. This allows the use of capnography to register bronchospasm, CO2 circulation in the circuit, spontaneous breathing attempts, etc. In Ukraine, capnometry and capnography are routinely used in the anesthesia during laparoscopic surgeries, which require strict control of ETCO2 due to the insufflation of CO2 into the abdominal cavity and its absorption by the peritoneum. However, the spectrum of capnometry application is actually much wider than just laparoscopic surgery. In the intensive care unit, it includes but is not limited to the following indications: confirmation of the endotracheal tube position during tracheal intubation; monitoring the respiratory circuit integrity, including while turning and transporting a patient; evaluation of the cardiopulmonary resuscitation effectiveness; evaluation of the mask ventilation effectiveness; breathing monitoring during procedural sedation; monitoring during mechanical ventilation; auxiliary monitoring of hemodynamics. This literature review discusses the advantages, disadvantages and methods of using capnometry/capnography for each of the listed indications in detail.

Effects of Inspiratory Muscle Training on Physiological Performance Variables in Women's Handball.

Inspiratory muscle training (IMT) has been used in different sports, although there is no consensus on its benefits. We investigated the effects of eight weeks of IMT in women's handball. Twenty-four players were randomly distributed into experimental (EXP; n = 13) and control (CON; n = 11) groups. Only the EXP group performed IMT using the POWERBreathe device, following indications of the manufacturers. Before and after the intervention, spirometric variables were evaluated at rest and during a graded test using direct analysis of respiratory gases. Perception of exertion at submaximal intensity was also determined. No significant differences were observed post- vs. pre-intervention (p ≥ 0.05) regarding forced vital capacity (FVC), forced expiratory volume in the 1st second (VEF1), FVC/VEF1, maximal expiratory flow at 50% of FVC or peak inspiratory flow. Post-intervention, only the CON group increased their absolute and relative VO2max (2.1 ± 0.2 L/min pre vs. 2.2 ± 0.3 L/min post; 33.6 ± 3.6 ml/kg∙min pre vs. 34.5 ± 3.2 ml/kg∙min post, respectively). No significant improvements (p ≥ 0.05) were observed in VO2 associated with ventilatory threshold 1 (VT1), nor in the intensity associated with VO2max and VT1. However, there was a tendency for the mentioned variables to decrease in the CON group, while in the EXP group the trend was to maintain or increase previous values. IMT did not determine an improvement in the perception of exertion at submaximal intensity. The use of POWERBreathe, as described in the present study, is feasible in terms of time and effort, although its benefits may not be significant.

Features of Mechanical Lung Ventilation During Robot-Assisted Radical Prostatectomy in Patients with Different Body Mass Index

The aim of the study. To evaluate effects of carboxyperitoneum and steep Trendenburg position on respiratory biomechanics and gas exchange indicators in patients with different body mass index (BMI) during robotic-assisted radical prostatectomy (RRP). To develop an algorithm for choosing the optimal mechanical lung ventilation (MLV) regimen. Materials and methods. The study included 141 patients with verified prostate cancer who were candidates for RPR. Participants were divided into 2 groups based on BMI: group I included 88 patients with BMI30 kg/m2, group II — 53 patients with BMI30 kg/m2. Indicators of respiratory biomechanics and gas exchange during ventilation in various modes (Volume Controlled Ventilation (VCV), Pressure Controlled Ventilation (PCV), Pressure Controlled– Inverse Ratio Ventilation (PC-IRV) were analyzed in each group at 5 consecutive stages of the procedure.Results. The key parameters evidencing the effectiveness and safety of MLV during RRP procedure did not vary significantly under various ventilation regimens in the group of patients with a BMI30 kg/m2. Whilst in obese patients the use of VCV mode resulted in a significant increase of airway peak pressure (Ppeak) already at the stage of placing them into a steep Trendelenburg position (35°), thus endangering with the development of ventilator-induced lung injury. Increased Ppeak was also accompanied by the drop in oxygen saturation and significantly lower SpO₂ values, starting from the stage of applying carboxyperitoneum and until the end of surgical intervention.Conclusion. In non-obese patients, there’s no particular ventilator regimen that is crucial for achieving the safety and effectiveness of RRP anesthesia management, all regimens can be used. In patients with BMI30 kg/m2 PCV regimen and PC-IRV with inhalation/exhalation ratio of 1.5:1 can be considered as the optimal strategy for MLV during anesthesia for RRP surgery.

Highly Strain-Stable Intrinsically Stretchable Olfactory Sensors for Imperceptible Health Monitoring.

Intrinsically stretchable gas sensors possess outstanding advantages in seamless conformability and high-comfort wearability for real-time detection toward skin/respiration gases, making them promising candidates for health monitoring and non-invasive disease diagnosis and therapy. However, the strain-induced deformation of the sensitive semiconductor layers possibly causes the sensing signal drift, resulting in failure in achievement of the reliable gas detection. Herein, a surprising result that the stretchable organic polymers present a universal strain-insensitive gas sensing property is shown. All the stretchable polymers with different degrees of crystallinity, including indacenodithiophene-benzothiadiazole (PIDTBT), diketo-pyrrolo-pyrrole bithiophene thienothiophene (DPPT-TT) and poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiad-iazolo [3,4-c] pyridine] (PCDTPT), show almost unchanged gas response signals in the different stretching states. This outstanding advantage enables the intrinsically stretchable devices to imperceptibly adhere on human skin and well conform to the versatile deformations such as bending, twisting, and stretching, with the highly strain-stable gas sensing property. The intrinsically stretchable PIDTBT sensor also demonstrates the excellent selectivity toward the skin-emitted trimethylamine (TMA) gas, with a theoretical limit of detection as low as 0.3ppb. The work provides new insights into the preparation of the reliable skin-like gas sensors and highlights the potential applications in the real-time detection of skin gas and respiration gas for non-invasive medical treatment and disease diagnosis.

Efficient remediation of PAHs contaminated site soil using the novel slow-release oxidant material

The eco-friendly slow-release material for persulfate (PS) using chitosan (CS) and urea (U) composite as frame structure (CS-U@PS) was firstly used to remediate the site soil contaminated by polycyclic aromatic hydrocarbons (PAHs) from Hefei city, China. The influences of glutaraldehyde dosage and urea dosage on the slow released properties of CS-U@PS was investigated and a longer release time of 190.0 d to 591.0 d was achieved, indicating the promising tunability according to the contents of pollutants in site soil. The effects of various factors (cross-linking agent dosage, initial PAHs concentration, CS-U@PS dosage, hydrogen peroxide dosage, etc.) on the degradation of soil spiked with PAHs (80 and 8 mg·kg−1) by CS-U@PS were studied, and the degradation pathway of PAHs was speculated. According to the EPR results, urea played an important role in promoting the 1O2 generation, which was the main reactive oxidative species. Finally, the long-term remediation of the industrial site soil with total PAHs of 553.2 mg·kg−1 was performed using 50 mg·g−1soil CS-U@PS and 90.22% removal rate was obtained after nine months. Moreover, the monitoring results of soil respiration gas show that, in addition to CO2, there is no additional greenhouse gas generated in the process of soil remediation, suggesting that the remediation of site soil using CS-U@PS has an excellent application prospect.

Influence of Anti-Coccidial Compounds and Phytogenic Saponin Extracts on In Vitro and In Vivo Ruminal Fermentation and Methane Production of Cattle.

Four experiments were conducted to evaluate sources of anti-coccidial compounds and phytogenic saponin extracts on in vitro and in vivo ruminal fermentation and CH4 production at multiple inclusion levels. In experiment 1, eight steers were fed either a finishing diet or a finishing diet supplemented with 0.5 mg/kg BW decoquinate (DCQ) and 3.33 mg/kg BW Yucca schidigera extract (YSE), and respiratory gas exchange was measured. In experiment 2, four ruminally-cannulated steers were fed the same treatments as experiment 1, and ruminal fermentation was evaluated. Anti-coccidial sources (experiment 3; monensin, DCQ, amprolium) and saponin sources (experiment 4; YSE, Quillaja saponaria extract) and levels were evaluated for effects on in vitro ruminal fermentation and CH4 production. DCQ + YSE supplementation did not influence (p ≥ 0.24) in vivo respiratory gas consumption/production, in situ DM degradation, or liquid passage kinetics. Ruminal propionate proportion tended to increase (p = 0.09) with DCQ + YSE. Monensin decreased (p ≤ 0.04) in vitro acetate:propionate and CH4 production; saponin supplementation linearly increased (p < 0.01) propionate proportion but did not influence (p ≥ 0.38) in vitro CH4 production. Saponins and non-antibiotic anti-coccidials did not influence in vitro or in vivo CH4 production with finishing diets.

Physiological and Energetic Demands During Still-Rings Routines of Elite Artistic Gymnasts.

The aim of the study was to analyze physiological and energetic demands of elite gymnasts during still-rings routines (SRRs). Eleven male gymnasts (mean [SD] 23.6 [3.9]y, 65.9 [5.6]kg, 171.1 [6.7]cm) performed a maximal graded exercise test and an individual SRR, during which respiratory gas and heart rate (HR) were measured using a mobile spiroergometer and a paired HR sensor. Metabolic energy and the energy contribution in terms of aerobic, anaerobic lactic, and anaerobic alactic were determined by oxygen uptake (VO2) during exercise, net lactate production, and the fast component of postexercise VO2 kinetics. Mean routine duration of the SRRs was 48.3 (4.5)seconds. VO2 and HR during SRRs were shown to be 86.9% (5.9%) and 91.0% (3.3%), respectively, of the maximal values measured during the graded exercise test. The anaerobic alactic, aerobic, and anaerobic lactic systems provided 50.9% (6.6%), 28.6% (4.8%), and 20.5% (5.2%), respectively, of the total energy required during SRRs. The energy contribution of the anaerobic lactic system correlated negatively with individual anaerobic threshold (r = -.715) and maximal VO2 (r = -.682). The anaerobic alactic system is the predominant energy source for ATP resynthesis during SRRs. The high relative VO2 and HR values reached during SRRs showthat these routines strongly stress the cardiovascular system.

Adaptations for gas exchange enabled the elongation of lepidopteran proboscises.

The extensive biodiversification of butterflies and moths (Lepidoptera) is partly attributed to their unique mouthparts (proboscis [Pr]) that can span in length from less than 1mm to over 280mm in Darwin's sphinx moths. Lepidoptera, similar to other insects, are believed to inhale and exhale respiratory gases only through valve-like spiracles on their thorax and abdomen, making gas exchange through the narrow tracheae (Tr) challenging for the elongated Pr. How Lepidoptera overcome distance effects for gas transport to the Pr is an open question that is important to understanding how the Pr elongated over evolutionary time. Here, we show with scanning electron microscopy and X-ray imaging that distance effects on gas exchange are overcome by previously unreported micropores on the Pr surface and by superhydrophobic Tr that prevent water loss and entry. We find that the density of micropores decreases monotonically along the Pr length with the maxima proportional to the Pr length and that micropore diameters produce a Knudsen number at the boundary between the slip and transition flow regimes. By numerical estimation, we further show that the respiratory gas exchange for the Pr predominantly occurs via diffusion through the micropores. These adaptations are key innovations vital to Prelongation, which likely facilitated lepidopteran biodiversification and the radiation of angiosperms by coevolutionaryprocesses.

The biophysical modelling of the diffusion in the living systems

The transport phenomena mean the variation in time and space of generalized forces when they generate flows for which conservation laws apply. According to the general definition, the diffusion is a mass transportation under the action of a generalising force, which can be the concentration gradient, the pressure gradient, etc. The diffusion is explained on the basis of the spontaneous movement of the molecules which have the tendency to spread in equal numbers in each subspace tendency which arises from the concentration gradient. The diffusion is a frequently found phenomenon: with diffusion, the respiratory gas exchange takes place between the air in the alveoli, blood and cellular cytoplasm, the nutritive substances diffuse from the thin intestine into blood and further away in the tissues, the diffusion lays at the basis of the white cells’ chemotactism, the olfaction happens when the molecules of the smelling substances spread in the air reach the cells of the olfactory mucosa. A particular case of diffusion is dialysis, which consists in the diffusion thought semipermeable membranes of the substances with a molecule smaller than the membranes pores. The dialysis takes place up to the equalising of the concentration in the two parts of the membrane.

Design and Operation of High Flow Oxygen Therapy: A novel approach to producing high concentration humidified oxygen for covid-19 patients

High-flow oxygen therapy provides adequate oxygen to those patients who suffer from pulmonary disorders due to the COVID-19 virus. The purpose of this research is to develop an oxygen therapy device that produces high-flow oxygen and provides a humidified supply of oxygen to patients suffering from Chronic Obstructive Pulmonary Disease (COPD) and Acute Respiratory Distress Syndrome (ARDS) caused by COVID-19. The development of a High-Flow Oxygen Therapy (HFOT) device using cannulation is a much-needed solution to fill the gap in the availability of ventilators in resource-limited settings like Pakistan. The HFOT has a system that offers high-flow oxygen with the help of a blender that is capable of producing a balanced mix of air and oxygen while keeping the fraction of inspired oxygen (FiO2) at the desired level. A Proportional, Integral, and Derivative (PID) valve is used to control the flow of the mixed gas as per the requirement. The mixed air is then passed through a humidifier that warms, humidifies, and purifies respiratory gas. The flow rate of the device is designed to produce up to 60 Liters Per Minute (LPM) with ± 0.5 variations with proper humidity. The designed prototype is tested for the gas flow rate, oxygen concentration, and desired pressure using professional calibrators and artificial lungs. The test results show significant achievements in delivering humid gases with high flow rates. ness together with appropriate humidification, gas warming, and concentration of oxygen.

Porosity quantification in pear fruit with X-ray CT and spatially resolved spectroscopy

Hypoxia-related disorders in apple and pears such as browning have been associated with insufficient transport of respiratory gasses inside the fruit during controlled atmosphere (CA) storage. Tissue porosity affects gas exchange and, hence, fruit respiration. It might, therefore, be interesting to adapt the storage conditions to the porosity of the fruit, especially in the case of low-porosity fruit like pears, which are highly susceptible to browning disorders. To improve the current CA storage strategies in that direction, fast, non-destructive measurement of fruit porosity is required. To this end, X-ray CT-based porosity maps and spatially resolved spectroscopy (SRS) were used to characterize respectively the porosity and optical properties of intact pear cultivars (Pyrus communis L.), including ‘Thimo’, ‘Cepuna’, and ‘Conference’. Thereafter, the link between the fruit porosity and light-scattering properties was investigated. The porosity of the tissue region from the fruit surface down to 3 mm deep as well as the spatially averaged porosity of intact pears from 3 cultivars were found to be linearly correlated to the reduced scattering coefficient (µs’) at 760 nm and 835 nm calculated from SRS measurements. Both ‘Cepuna’ and ‘Conference’ pears showed similar porosities and scattering levels, which were slightly higher than those observed for ‘Thimo’ pears. The presented results suggest the possible application of laser scatter imaging at 760 nm and 835 nm for fast, contactless and non-destructive assessment of pear porosity.

Gas volume corrections in intensive care unit: needed or pointless?

The conditions of temperature, pressure, and saturation in which respiratory gas volumes are expressed [standard temperature and pressure, dry (STPD), ambient temperature and pressure, saturated (ATPS), or body temperature and pressure, saturated (BTPS)] are physiologically relevant, but often ignored or unknown in clinical practice. In this study, we aimed to investigate whether and at which extent the gas volume corrections, either in natural or artificial lung, may alter key respiratory and metabolic variables and the possible clinical consequences. We primarily referred to the effects of gas volume corrections on three physiological variables: physiological dead space, venous admixture, and total CO2 production (V̇co2) during extracorporeal support. We used three physiological models in which calculations of these variables have been performed with and without correction of gas volumes, both in a theoretical model and in 448 patients. The lack of gas volume correction leads to an error in the computation of physiological dead space fraction between 0.05 and 0.15, both in the theoretical model and in the patient population. The venous admixture was minimally affected by the absence of correction (0.01-0.04 error). During extracorporeal support, if the V̇co2 of natural and membrane lung is expressed in different conditions, potentially large errors (0%-18.4%) may occur in the computation of total V̇co2 (V̇co2tot = V̇co2ML + V̇co2NL). This may lead to inappropriate settings of mechanical ventilation with higher plateau pressure. As the dead space and the CO2 sharing between natural and artificial lung are relevant both as prognostic index and as a guide for appropriate mechanical ventilation, their inappropriate computation may lead to erroneous categorization of the patients and inappropriate mechanical treatment.NEW & NOTEWORTHY Gas volume conditions are often ignored or unknown in the clinical practice. However, they could have relevance for the calculation of some key variables in ICU setting. This study shows that gas volume corrections are mostly relevant when assessing CO2 clearance, both in mechanical ventilation and during extracorporeal support, whereas irrelevant for oxygenation assessment of patients. Knowing when the appropriate corrections are needed allows to better understand patients' clinical conditions and to tailor the treatment.

Cardiorespiratory Fitness and Risk of Aortic Stenosis (from a Prospective Cohort Analysis)

Cardiorespiratory fitness (CRF) is a major risk factor and predictor of atherosclerotic cardiovascular disease. However, the relationship between CRF and risk of aortic stenosis (AS) has not been previously investigated. Thus, we aimed to assess the prospective association between CRF and risk of AS. CRF, as measured by maximal oxygen uptake, was assessed using a respiratory gas exchange analyzer during cardiopulmonary exercise testing in 2,308 men aged 42 to 61 years recruited into the Kuopio Ischemic Heart Disease prospective cohort study. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated for AS. During a median follow-up of 27 years, 101 cases of AS occurred. Dose-response analysis suggested there might be a nonlinear relation between CRF levels and AS risk. In an analysis adjusted for age, body mass index, systolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, smoking, history of type 2 diabetes mellitus, and coronary heart disease, the HRs 95% (CIs) of AS were 0.57 (0.34 to 0.96) and 0.91 (0.53 to 1.57) for participants in the middle and upper third of CRF levels, respectively, compared with participants in the bottom third. After further adjustment for alcohol consumption, the corresponding HRs (95% CIs) were 0.58 (0.34 to 0.97) and 0.91 (0.53 to 1.56), respectively. In conclusion, higher CRF levels may be associated with a lower incidence of AS in middle-aged and older Finnish men. Given the likely limitations of low statistical power, further research is needed to provide insights into the dose-response nature of any relationship between CRF and AS.

The biophysical modelling of the diffusion in the living systems

The transport phenomena mean the variation in time and space of generalized forces when they generate flows for which conservation laws apply. According to the general definition, the diffusion is a mass transportation under the action of a generalising force, which can be the concentration gradient, the pressure gradient, etc. The diffusion is explained on the basis of the spontaneous movement of the molecules which have the tendency to spread in equal numbers in each subspace tendency which arises from the concentration gradient. The diffusion is a frequently found phenomenon: with diffusion, the respiratory gas exchange takes place between the air in the alveoli, blood and cellular cytoplasm, the nutritive substances diffuse from the thin intestine into blood and further away in the tissues, the diffusion lays at the basis of the white cells’ chemotactism, the olfaction happens when the molecules of the smelling substances spread in the air reach the cells of the olfactory mucosa. A particular case of diffusion is dialysis, which consists in the diffusion thought semipermeable membranes of the substances with a molecule smaller than the membranes pores. The dialysis takes place up to the equalising of the concentration in the two parts of the membrane.

Candida tropicalis as a novel dietary additive to reduce methane emissions and nitrogen excretion in sheep.

The goal of this study was to investigate Candida tropicalis as a kind of environmentally friendly dietary additive to manipulate ruminal fermentation patterns, reduce methane emissions and nitrogen excretion, and to screen the appropriate dose for sheep. Twenty-four Dorper × thin-tailed Han crossbred ewes (51.12kg ± 2.23kg BW) were selected and randomly divided into four groups which were fed Candida tropicalis at dose of 0 (control), 4 × 108 (low dose), 4 × 109 (medium dose), and 4 × 1010 (high dose) colony-forming units (CFU)/d per head, respectively. The experiment lasted 33days with 21days for adaptation and 12days for nutrient digestibility trial and respiratory gases sampling. The results showed that nutrients intake was not affected by Candida tropicalis supplementation (P > 0.05), whereas apparent digestibility of nutrients significantly increased compared with the control group (P < 0.05). Nitrogen and energy utilization increased with Candida tropicalis supplementation (P < 0.05). Compared with the ewes of the control group, rumen fluid pH and NH3-N concentration were not affected (P > 0.05), whereas total volatile fatty acid concentration and molar proportion of propionate were greater (P < 0.05), and molar proportion of acetate and the ratio of acetate to propionate were less (P < 0.05) when the ewes were fed Candida tropicalis. Daily total CH4 production (L/d) and CH4 emissions yield (L/d of CH4 per kg of dry matter intake, metabolic weight, or digestibility dry matter intake) were decreased at the low dose group (P < 0.05). The abundance of total bacteria, methanogen, and protozoa in rumen fluid was significantly higher at medium dose and high dose of Candida tropicalis supplementation (P < 0.05) compared with low dose and the control group. In summary, Candida tropicalis supplementation has a potential to reduce CH4 emissions and nitrogen excretion, and the optimal dose should be 4 × 108CFU/d per head.