Oxygen Uptake Curves Research Articles

Cardiopulmonary Exercise Test in Myocardial Ischemia Detection

Exercise electrocardiography has low sensitivity for detection of myocardial ischemia. However, when combined with cardiopulmonary exercise testing (CPEX), the sensitivity and specificity of ischemia detection improves significantly. CPEX offers unique advantages over imaging techniques in tricky situations such as balanced ischemia. Early abnormal oxygen uptake would point toward profound coronary stenosis that could be missed in perfusion imaging. CPEX could be an invaluable tool in asymptomatic left bundle branch block pattern, without exposing patients to the risks of computerized tomography or invasive coronary angiography. Normal oxygen uptake curves would rule out significant coronary stenosis as the cause of left bundle branch block pattern. Elseways, abnormal oxygen uptake in patients with normal coronary arteries could indicate microvascular angina. Furthermore, exercise capacity is an excellent predictor of cardiovascular risk in those with and without heart disease. Using two clinical cases we introduce the concept of gas-exchange and hemodynamic changes encountered in ischemic heart disease.

Study of Aerobic Biodegradation of Surfactants and Fluorescent Whitening Agents in Detergents of a Few Selected Asian Countries (India, Indonesia, Japan, and Thailand)

Consumption of detergents containing linear alkyl benzene sulfonate (LAS) and fluorescent whitening agents (FWAs) is increasing rapidly in Asian countries. A respirometric oxygen uptake method was conducted to examine the aerobic biodegradability of some of the commercially available laundry and dishwashing detergents of India, Japan, Indonesia, and Thailand. Indian detergents and Japanese detergents showed 95–100% of LAS removal. However, the three-dimensional fluorescent spectra results indicated the presence of residual metabolites such as sulfophenyl carbonate. Indonesian detergents and Thai detergents showed less LAS removal, but the progress of benzene ring cleavage of LAS in these detergents was observed from the test results. The FWAs were observed mainly in laundry detergents. The removal of FWAs during biodegradation test was observed to be between 12.4 and 78.8%. The complex changes in oxygen uptake curve during the test period suggested the presence of various organic compounds in the detergents. The tested detergents were classified into three clusters based on the relationship between the total organic carbon and the fluorescence (220/290 nm) removals. The diverse biodegradation results among the tested detergents from different Asian countries suggested the effects of various ingredients present in the detergents.

A predictor of aerobic threshold for patients with heart failure with reduced ejection fraction.

[Purpose] The initial cardiopulmonary response to exercise is hypothesized to be a useful predictor of aerobic threshold in patients with heart failure. This study aimed to evaluate the correlation between aerobic threshold and cardiopulmonary responses to exercise onset by comparing patients with heart failure using preserved (≥50%) and reduced (<50%) left ventricular ejection fractions. [Participants and Methods] Twenty-eight males (age, 36–82 years; 12 with preserved and 16 with reduced left ventricular ejection fractions) underwent a progressive submaximal cardiopulmonary exercise test using a cycle ergometer. The aerobic threshold, time constant, and area under the oxygen uptake curve for the first 4 min (V̇O2AUC) were determined. [Results] A significant association was observed between aerobic threshold and V̇O2AUC in the reduced group but not in the preserved group. No significant correlations were found between time constant and V̇O2AUC or between aerobic threshold and time constant in either group. [Conclusion] The results suggest that V̇O2AUC measured from exercise onset to an initial 4-min period could provide an easily and safely obtained predictor to assess aerobic capacity in people with reduced left ventricular ejection fractions.

Cardiopulmonary Performance During Maximal Exercise in Soccer Players with Alterations in Renal Function.

The aim of this study was to evaluate the curves of cardiorespiratory variables during cardiopulmonary exercise testing (CPET) in soccer players who had acute alterations in the glomerular filtration rate (GFR) after performing the pre-season training protocol. Sixteen male professional soccer players (25 ± 3 years; 179 ± 2 cm; and 77 ± 6 kg) were evaluated for oxygen uptake (VO2), heart rate (HR) and pulse relative oxygen (relative O2 Pulse) curves with intervals corresponding to 10% of the total duration of CPET. Athletes were grouped according to the GFR and classified as decreased GFR (dGFR; n = 8) and normal GFR (nGFR; n = 8). Athletes from the dGFR group exhibited lower VO2 values (p < 0.05) when 90% (dGFR 49.8 ± 4.0 vs. nGFR 54.4 ± 6.1 ml·kg-1·min-1) and 100% (dGFR 52.6 ± 4.1 vs. nGFR 57.4 ± 5.9 ml·kg-1·min-1) of the test was complete; HR high values (p < 0.05) when 90% (dGFR 183.7 ± 5.1 vs. nGFR 176.6 ± 4.8 bpm-1) and 100% (dGFR 188.1 ± 5.0 vs. nGFR 180.8 ± 4.8 bpm-1) of the test was complete; and lower relative O2 Pulse values (p < 0.05) when 70% (dGFR 25.6 ± 8.4 vs. nGFR 27.9 ± 9.7 ml·beat-1·kg-1), 80% (dGFR 26.6 ± 8.8 vs. nGFR 29.1 ± 10.0 ml·beat-1·kg-1), 90% (dGFR 27.1 ± 9.0 vs. nGFR 30.8 ± 10.6 ml·beat-1·kg-1) and 100% (dGFR 28 ± 9.2 vs. nGFR 31.8 ± 10.9 ml·beat-1·kg-1) of the test was complete. A correlation was found (r = −0.66, R2 = 0.44, p = 0.00) between lower VO2 peak and elevated levels of urinary protein excretion. In conclusion, soccer players with reduced kidney function after performing the pre-season training protocol also presented alterations in cardiopulmonary variables. We suggest that monitoring of renal function may be used to identify less conditioned soccer players.

Removal of Recalcitrant Carbon from an Industrial Wastewater Using Electrocoagulation

Manufacturing industries synthesize new chemical products every day, which eventually find their way into domestic and industrial wastewaters. As a result, wastewater is becoming increasingly more complex in nature. The emerging pollutants escape the treatment systems and appear in the receiving water bodies. Wastewater treatment plants in India still report effluent parameters in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) at the ppm level, whereas these emerging pollutants, many of whom are non-biodegradable, can be toxic and carcinogenic at the ppb level. Therefore, it is imperative to look for alternatives or upgrade the existing systems which safely remove these harmful compounds from wastewater. In this research, efficiency of electrocoagulation process was assessed in a laboratory-scale setup in removing recalcitrant carbon from a real wastewater. The wastewater was collected from an effluent treatment plant that receives domestic wastewater and industrial effluents from chemical, bulk drugs and allied industries, for treatment. In this study, the wastewater sample was analyzed for total dissolved solids (TDS) and total organic carbon (TOC), and then treated biologically in a respirometer using aerobic microorganisms. After the oxygen uptake curve plateaued, indicating a cessation of biological process, the sample was analyzed for TDS and TOC and put in a lab-scale electrocoagulation setup. Iron and Aluminium electrodes were used in the study and efficiency of the system in removing the recalcitrant/residual carbon and TDS was studied with respect to the reaction time. The results showed that electrocoagulation can be a potential post-biological treatment system for removal of recalcitrant carbon from wastewaters.

The First Muscle Oxyhemoglobin Inflection Point Is Correlated To Gas Exchange Threshold And Time-To-Exhaustion During Heavy Intensity Exercise

PURPOSE: The twofold aim of the study was to: 1) compare the gas exchange threshold (GET), the first oxyhemoglobin inflection point ([O2Hb]-T), and perceptual threshold as determined during an incremental exercise test, and 2) investigate the link between each threshold and time-to-exhaustion during heavy intensity exercise. METHODS: Fourteen competitive cyclists performed an incremental exercise test to exhaustion on a cycloergometer to determine the different thresholds and peak workload (Wpeak). The participants then performed a sub-maximal constant workload test (90% Wpeak) to exhaustion to determine time-to-exhaustion. The thresholds were identified from: 1) the first breakpoint in the oxygen uptake vs carbon dioxide output curve (GET), 2) the first muscle oxyhemoglobin inflection point ([O2Hb]-T), and 3) a rating of 13 in perceived exertion (perceptual threshold: RPE13-T). RESULTS: Oxygen uptake at the different thresholds was not significantly different (P > 0.05). Moreover, GET and [O2Hb]-T were significantly correlated: (1) to each other (r ≥ 0.79; P ≤ 0.001) and (2) to time-to-exhaustion (r = 0.81 and r = 0.72, respectively; P < 0.01). RPE13-T, however, was not significantly correlated with the time-to-exhaustion (P = 0.148). CONCLUSIONS: The ‘anaerobic threshold’ as identified from GET was concomitant to [O2Hb]-T. Both thresholds were correlated to time-to-exhaustion, and could therefore be used as a performance index in middle-duration events.

Thermal oxidation and degradation of poly-3-hydroxybutyrate nonwoven materials

Studies of the thermal degradation of poly-3-hydroxybutyrate samples in the presence and absence of oxygen demonstrate that, in the first case, the degradation begins sooner, but the decomposition temperature (maximum of degradation peak) changes only slightly for two different types of samples. It is shown that the activation energy for the thermal degradation of samples without access of oxygen is higher. According to the oxygen uptake curves at T = 150°C and an oxygen pressure of p = 600 Torr, the longest induction period is observed for film samples, whereas the maximum rate of oxidation, for fine nonwoven fiber samples. The kinetics of water uptake is investigated, which shows that the thermophysical characteristics of the samples alter after exposure to an aquatic environment.

Contribution of cardiopulmonary exercise testing to the identification of latent systolic dysfunction in chronic aortic regurgitation

Chronic aortic regurgitation (AR) is a valvulopathy of slow and insidious evolution, and patients may remain asymptomatic for a long period of time. Exercise-induced systolic dysfunction occurs during the natural history of chronic AR and is related to changes in both preload and afterload. We describe the case of a 58-year-old woman with a diagnosis of chronic AR who reported progressive dyspnea of six years’ duration. A cardiopulmonary exercise test to assess functional capacity showed flattening of both oxygen uptake and oxygen pulse curves, suggesting latent systolic dysfunction related to chronic AR, which was later confirmed by stress Doppler echocardiogram with dynamic physical exercise.

Contribution of cardiopulmonary exercise testing to the identification of latent systolic dysfunction in chronic aortic regurgitation

Chronic aortic regurgitation (AR) is a valvulopathy of slow and insidious evolution, and patients may remain asymptomatic for a long period of time. Exercise-induced systolic dysfunction occurs during the natural history of chronic AR and is related to changes in both preload and afterload. We describe the case of a 58-year-old woman with a diagnosis of chronic AR who reported progressive dyspnea of six years’ duration. A cardiopulmonary exercise test to assess functional capacity showed flattening of both oxygen uptake and oxygen pulse curves, suggesting latent systolic dysfunction related to chronic AR, which was later confirmed by stress Doppler echocardiogram with dynamic physical exercise.

Time-evolution of oxidation states at the Ni(111) surface: O2 incident translational energy dependence

Metallic Ni is expected to be a substitution candidate for Pt and Pd in catalytic materials. Generally speaking, catalytic reactions take place on a metal oxide layer. In this study, therefore, the oxidation states of the Ni(111) surface, which were made by irradiation with a supersonic O2 molecular beam, were analyzed by soft x-ray photoemission spectroscopy with synchrotron radiation. The oxygen uptake curve and initial sticking rate were found to show remarkably strong dependence on the O2 incident energy for energies of up to 2.3 eV. The intermediate plateau seen in the oxygen uptake curve for low incident energies was found to disappear with increasing incident energy due to a change of the dissociative adsorption mechanism from a two-dimensional island growth model to a direct activated adsorption model. Due to this activated adsorption, the formation rate of NiO and peroxide nickel increased as compared to backfilling oxidation by O2 gas.

Exertional acidotic responses in idiopathic pulmonary fibrosis: The mechanisms of exertional dyspnea

To understand the mechanism of exertional dyspnea, we postulated that, despite hyperoxia during exercise, patients with idiopathic pulmonary fibrosis (IPF) might not regulate exertional acidosis by ventilatory compensation to stop exercise. The exercise responses during 30% O2 or compressed air (CA) were examined in 13 patients with IPF. The PaO2, PaCO2, and HCO3− levels were higher during exercise with hyperoxia than with CA. At peak exercise, hyperoxia reduced the plasma lactate level. The dyspnea-ratio (%) of the ΔV˙O2 (peak minus resting oxygen uptake) curve reached a break point that occurred at a similar exercise point with hyperoxia and CA, preceded by a break point in the breathing frequency-ratio of the ΔV˙O2. Accordingly, the dyspnea score and pH each reached similar levels with hyperoxia and CA to stop exercise. Regardless of breathing CA or 30% O2, IPF patients did not regulate exertional acidosis by ventilatory compensation to stop exercise, resulting in reaching a specific pH.

Aerobic Exercise and Circulatory Dysfunction in Resistant Hypertension

We read with great interest the article by Dimeo et al1 dealing with the effects of aerobic exercise on blood pressure, arterial compliance, and cardiac index in resistant hypertensive subjects. The results of their study demonstrated that exercise significantly decreased systolic and diastolic daytime ambulatory blood pressure in patients with resistant hypertension. In addition, regular exercise reduced blood pressures on exertion and increased physical performances as assessed by maximal oxygen uptake and lactate curves, …

Clinical Implications

HomeHypertensionVol. 60, No. 3Clinical Implications Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBClinical Implications Originally published1 Sep 2012https://doi.org/10.1161/HYP.0b013e31826a2660Hypertension. 2012;60:575Blood Pressure Variability (page 625)There is increasing evidence that greater visit-to-visit variability of blood pressure is associated with a higher risk of stroke, an association that is independent of average blood pressure over time. Previous studies reporting on visit-to-visit variability of blood pressure and stroke have been relatively small and included select patients who were already at high cardiovascular disease risk. In addition, scarce data exist as to whether the relation of visit-to-visit variability of blood pressure and stroke is explained by an increase in blood pressure over time. The present study examined these associations in 58228 postmenopausal women with a wide range of cardiovascular disease risk enrolled in the Women's Health Initiative. Over a median follow-up of 5.4 years, a higher risk of stroke was associated with greater SD for the participant's mean systolic blood pressure (SBP) across visits (SD). The increased risk of stroke was similar for the SD regarding the participant's regression line when SBP regressed across visits and was independent of the temporal trend in SBP. The association was strongest for lower levels of average SBP across visits, particularly among individuals with average SBP <120 mmHg. Therefore, visit-to-visit variability of blood pressure contributes to stroke in a manner that is independent of blood pressure trends, particularly in individuals who otherwise would be considered to be low risk based on their average SBP.Renal Resistive Index in Hypertension (page 770)The renal restive index (RI) measured using Doppler ultrasonography has been shown to correlate with the degree of renal impairment in hypertensive patients, but the status of RI as an independent cardiovascular risk marker remains to be elucidated. The present study evaluated the prognostic role of RI in 426 essential hypertensive subjects with no previous cardiovascular disease. The primary study end point included combined cardiovascular and renal events. During an average of 3.1 years, RI was an independent predictor of worse outcome in the whole cohort, as well as in patients with estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m2. When divided into 4 groups based on the respective sex-specific median levels of RI in the eGFR ≥60 and eGFR <60 mL/min per 1.73 m2 groups, the group with eGFR <60 mL/min per 1.73 m2 and high RI had a significantly poorer event-free survival. Evaluation of renal RI in addition to eGFR may help to assess not only renal function but also intrarenal hemodynamics, as well as intrarenal vascular resistance, and thus may provide clinically sensitive prognostic information in patients with essential hypertension. These findings corroborate the hypothesis that the impact of RI on cardiovascular and renal risk is important and that identifying renal hemodynamic abnormalities is useful for predicting cardiovascular and renal outcomes, especially in hypertensive patients with chronic kidney disease.Exercise in Resistant Hypertension (page 653)Regular aerobic exercise is associated with a significant reduction of blood pressure in hypertensive and normotensive subjects. Therefore, exercise is broadly recommended by current American and European hypertension guidelines. It remains elusive, however, whether exercise is able to reduce blood pressure in resistant hypertension as well. The present article describes the results of a randomized, controlled trial on the effects of regular aerobic exercise in resistant hypertension. Resistant hypertension is defined by its low responsiveness to drug therapy. The findings of this study reveal that a low responsiveness to pharmacological therapy does not inevitably go along with a low responsiveness to exercise. A moderate-intensity aerobic exercise program led to a significant and clinically relevant reduction of blood pressure. Moreover, the training increased physical performance as assessed by maximal oxygen uptake and lactate curves. In contrast to the rapidly emerging data on new invasive strategies like renal sympathetic denervation or baroreflex activation, there are only very few data on the efficacy of simple lifestyle modifications in resistant hypertension. A low responsiveness of hypertension to drug therapy may intuitively evoke the impression, “If this multitude of antihypertensive drugs is not able to provide blood pressure control, lifestyle modifications won't do anyway.” The present study shows, however, that aerobic exercise on a regular basis is a helpful adjunct to control blood pressure and should be included in the therapeutic approach to resistant hypertension. Previous Back to top Next FiguresReferencesRelatedDetails September 2012Vol 60, Issue 3 Advertisement Article InformationMetrics © 2012 American Heart Association, Inc.https://doi.org/10.1161/HYP.0b013e31826a2660 Originally publishedSeptember 1, 2012 PDF download Advertisement

Aerobic Exercise Reduces Blood Pressure in Resistant Hypertension

Regular physical exercise is broadly recommended by current European and American hypertension guidelines. It remains elusive, however, whether exercise leads to a reduction of blood pressure in resistant hypertension as well. The present randomized controlled trial examines the cardiovascular effects of aerobic exercise on resistant hypertension. Resistant hypertension was defined as a blood pressure ≥140/90 mm Hg in spite of 3 antihypertensive agents or a blood pressure controlled by ≥4 antihypertensive agents. Fifty subjects with resistant hypertension were randomly assigned to participate or not to participate in an 8- to 12-week treadmill exercise program (target lactate, 2.0±0.5 mmol/L). Blood pressure was assessed by 24-hour monitoring. Arterial compliance and cardiac index were measured by pulse wave analysis. The training program was well tolerated by all of the patients. Exercise significantly decreased systolic and diastolic daytime ambulatory blood pressure by 6±12 and 3±7 mm Hg, respectively (P=0.03 each). Regular exercise reduced blood pressure on exertion and increased physical performance as assessed by maximal oxygen uptake and lactate curves. Arterial compliance and cardiac index remained unchanged. Physical exercise is able to decrease blood pressure even in subjects with low responsiveness to medical treatment. It should be included in the therapeutic approach to resistant hypertension.

Effects of oxygen on exertional dyspnoea and exercise performance in patients with chronic obstructive pulmonary disease

The results of studies on the oxygen response in patients with COPD should provide important clues to the pathophysiology of exertional dyspnoea. We investigated the exercise responses to hyperoxia in relation to dyspnoea profile, as well as cardiopulmonary, acidotic and sympathetic parameters in 35 patients with stable COPD (mean FEV(1) 46% predicted). This was a single-blind trial, in which patients breathed 24% O(2) or compressed air (CA) in random order during two incremental cycle exercise tests. PaO(2) and PaCO(2) were higher (P < 0.0001 and P < 0.05, respectively) at each exercise point while patients were breathing 24% O(2) compared with CA. At a standardized time point near peak exercise, use of O(2) resulted in reduced plasma lactate and plasma noradrenaline concentrations (P < 0.01). Peak minute ventilation/indirect maximum voluntary ventilation was similar while breathing 24% O(2) and CA. At peak exercise, the dyspnoea score, pH and plasma noradrenaline concentrations were similar while breathing 24% O(2) and CA. The dyspnoea-ratio (%) of Δoxygen uptake (peak minus resting oxygen uptake) curve reached a break point that occurred at a similar exercise point while breathing 24% O(2) or CA. Regardless of whether they breathed CA or 24% O(2) , patients with COPD did not develop ventilatory compensation for exertional acidosis, and the pH values measured were similar. Hyperoxia during a standardized exercise protocol did not alter the pattern of exertional dyspnoea in these patients, compared with breathing CA, although hyperoxia resulted in miscellaneous effects.

The Structural Basis of Endocannabinoid Oxygenation by Cyclooxygenase-2

The cyclooxygenases (COX-1 and COX-2) oxygenate arachidonic acid (AA) in the committed step of prostaglandin biogenesis. Substitutions of I434V, H513R, and I523V constitute the only differences in residues lining the cyclooxygenase channel between COX-1 and COX-2. These changes create a hydrophobic pocket in COX-2, with Arg-513 located at the base of the pocket, which has been exploited in the design of COX-2-selective inhibitors. Previous studies have shown that COX-2, but not COX-1, can oxygenate endocannabinoid substrates, including 2-arachidonoyl glycerol (2-AG). To investigate the isoform-specific structural basis of endocannabinoid binding to COX-2, we determined the crystal structure of the 2-AG isomer 1-arachidonoyl glycerol (1-AG) in complex with wild type and R513H murine (mu) COX-2 to 2.2 and 2.35 Å, respectively, and R513H muCOX-2 in complex with AA to 2.45 Å resolution. The 2,3-dihydroxypropyl moiety of 1-AG binds near the opening of the cyclooxygenase channel in the space vacated by the movement of the Leu-531 side chain, validating our previous hypothesis implicating the flexibility of the Leu-531 side chain as a determinant for the ability of COX-2 to oxygenate endocannabinoid substrates. Functional analyses carried out to compliment our structural findings indicated that Y355F and R513H muCOX-2 constructs had no effect on the oxygenation of 1-AG and 2-AG, whereas substitutions that resulted in a shortened side chain for Leu-531 had only modest effects. Both AA and 1-AG bind to R513H muCOX-2 in conformations similar to those observed in the co-crystal structures of these substrates with wild type enzyme.

A multi-analytical approach to studying binding media in oil paintings

This article presents a multi-analytical approach to investigating the drying, polymerisation and oxidative degradation of linseed oil, which had undergone various treatments known to be undertaken during the nineteenth century in preparation for painting. The oil was mechanically extracted from the same seed lot then processed by different methods: water washing, heat treatments, and the addition of driers, with and without heat. The oil was prepared in 1999 within the framework of the MOLART project. We compared thermogravimetric analysis (TG), which yields macromolecular information, with gas-chromatography mass-spectrometry (GC/MS) and direct exposure mass spectrometry (DE-MS), which provide molecular information. This comparison enabled us to elucidate the role of pre-treatment on the composition of the oil. TG and oxygen uptake curves registered at a constant temperature helped us to identify the different physical behaviour of the oil samples, thus highlighting the presence of hydrolysed, oxidised and crosslinked fractions, as a consequence of the different pre-treatments. GC/MS was used to characterise the soluble and non-polymeric fraction of the oil, to calculate the ratios of palmitic to stearic acid (P/S), and azelaic to palmitic acid (A/P), and to further evaluate the effects of oil pre-treatments. DE-MS using chemical ionisation with CH4, enabled us to establish the chemical composition of the oil in different stages of ageing. DE-MS proved to be a useful tool for a simultaneous semi-quantitative characterisation of the free fatty acids, monoglycerids, diglycerides and triglycerides present in each sample. The combination of thermal analysis with GC/MS and DE-MS enabled a model to be developed, which unravelled how oil pre-treatments produce binders with different physical–chemical qualities.

Adsorption Dynamics on Si(111)-7 × 7 Surface Induced by Supersonic O2 Beam Studied Using Real-Time Photoelectron Spectroscopy

The adsorption mechanisms of O2 on a Si(111)-7 × 7 surface were studied using real-time X-ray photoelectron spectroscopy with synchrotron radiation in conjunction with a supersonic molecular-beam technique. To study the dependence of the initial sticking probability, s0, saturation coverage of the O2 incident energy, En, and the oxygen uptake curves, which were evaluated from the time evolution of O 1s peak area, were measured over energy ranges from En = 0.03 eV (thermal gas) to 2.26 eV. It was found that a trapping-mediated adsorption mechanism is dominant at En < 0.06 eV. In contrast, an activated adsorption mechanism becomes prominent at En > 0.06 eV, along with the trapping-mediated adsorption mechanism which becomes less prevalent with increasing En. The saturation coverage at energies over 1.9 eV is approximately 1.6 times larger than that at 0.03 eV. Two different components of the O 1s spectrum and their energy dependence were verified. A marked increase in the tri oxygen component is clearly observed in the O 1s photoelectron spectrum for saturation at En > 0.39 eV, which is the evidence for the enhancement of dissociative adsorption of O2 into the subsurface layers; 0.39 eV was taken as the threshold energy for En dependence of both s0 and saturation coverage. The adsorption states induced via the novel reaction channel correlating with En were confirmed by the in situ spectroscopic surface analysis method.

Impact of training status on maximal oxygen uptake criteria attainment during running

Objectives. The aims of this study were to assess whether training status influenced maximal physiological and perceptual responses and whether certain maximal criteria were more sensitive for individuals with different levels of training. Methods. Males who were either trained (N=8) or untrained (N=9) underwent a maximal treadmill test to assess whether thecriteria to indicate VO2 max were training-specific.Results. VO2 max was significantly higher in the trained (70.0mlO2.kg-1.min-1) compared with the untrained group (54.5 mlO2.kg-1.min-1). Only 11% of the trained and 56% of the untrained individuals achieved a plateau in the oxygen uptake curve. Peak treadmill running speed was significantly faster and total test time significantly longer in the trained group. In contrast, peak lactate, although maximal for both groups, was significantly higher in the untrained group (13.5 mmol.l-1 compared with 10.3 mmol.l-1). The other responses were not different between the groups. Noteworthy is that none of the subjects achieved all of the criteria indicating a maximal effort. The criteria most achieved in both sampleswere HRmax, RPEmax and Lamax with the latter being the mostattained in the untrained group and RPEmax being mostly attainedby the trained group.Conclusions. The criteria used to indicate attainment of VO2 max may be limited and may differ when comparing a heterogeneous training sample. Although VO2 max was significantly higher in the trained group, responses were different for O2 plateau attainment and Lamax but similar for the other British Association of Sports Sciences criteria. It may be concluded that the physiological variables coinciding with maximal effort may differ in individuals with different levels of training.

Non‐invasive measurement of the mean alveolar O2 tension from the oxygen uptake versus tidal volume curve

The classical equations for measuring the mean and the ideal alveolar O(2) tension are based on assumptions, which are shown to be invalid. So we thought to develop a new, non-invasive method for measuring the mean alveolar P,O(2) within the volume domain (PA,O(2(Bohr))). This method is based on the oxygen uptake vs. tidal volume curve (VO(2) vs. VT) obtained during tidal breathing of room air and/or air enriched with oxygen. PA,O(2(Bohr)) and the ideal alveolar PO(2) (PA,O(2(ideal))) were simultaneously measured in 10 healthy subjects and 34 patients suffering from chronic obstructive pulmonary disease (COPD) breathing tidally room air at rest. Additionally, 10 subjects (three healthy subjects and seven COPD patients) were studied while breathing initially room air and subsequently air enriched with oxygen. According to the results, PA,O(2(Bohr)) considerably differed from PA,O(2(ideal)) (P = 0.004). The cause of the difference, at the individual's R, is: (1) the difference between the arterial and Bohr's alveolar CO(2) tension, mainly in COPD patients, and (2) the inequality between Bohr's alveolar part of the tidal volume for CO(2) and O(2). Furthermore, end-tidal gas tension (PET,CO(2) and PET,O(2)) differed from Pa,CO(2) and PA,O(2(Bohr)) respectively. The deviation of PA,O(2(Bohr)) from PA,O(2(ideal)) has a definite impact on Bohr's dead space ratio for O(2) and CO(2), and on the alveolar-arterial O(2) difference. The difference (PA,O(2(Bohr)) - PA,O(2(ideal))) is not related to the pathology of the disease. So, gas exchange within the lungs should be assessed at the subject's R from PA,O(2(Bohr)) and PA,CO(2(Bohr)) but not from PA,O(2(ideal)) nor Pa,CO(2).