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The ventilatory efficiency for carbon dioxide output ( V ˙ CO2) during exercise, as measured by the minute ventilation vs. V ˙ CO2 slope ( V ˙ E vs. V ˙ CO2 slope), is a powerful prognostic index in patients with chronic heart failure (CHF). This measurement is higher in women than in men, and it increases with age. This study aimed to investigate the usefulness of the predicted value of the percentage V ˙ E vs. V ˙ CO2 slope (% V ˙ E vs. V ˙ CO2 slope) as a prognostic index in patients with CHF. A total of 320 patients with CHF and a left ventricular ejection fraction (LVEF) < 45% (male, 85.6%; mean age, 64.6 years) who underwent symptom-limited cardiopulmonary exercise tests using a cycle ergometer were included in the study. The % V ˙ E vs. V ˙ CO2 was calculated using predictive formulae based on age and sex. Cardiovascular-related death was defined as the primary endpoint. The mean follow-up duration was 7.5 ± 3.3 years. Of 101 patients who died during the study period, 75 experienced cardiovascular-related deaths. The average V ˙ E vs. V ˙ CO2 slope was 32.8 ± 8.0, and the average % V ˙ E vs. V ˙ CO2 slope was 119.6 ± 28.2%. The cumulative incidence of cardiovascular-related death after 10 years of follow-up were 44.7% (95% CI 34.4–54.6%) in patients with % V ˙ E vs. V ˙ CO2 slope > 120 and 15.0% (95% CI 9.4–21.8%) in patients with % V ˙ E vs. V ˙ CO2 slope ≤ 120. The multivariate Cox regression analysis indicated that a % V ˙ E vs. V ˙ CO2 slope > 120 was an independent predictor of cardiovascular-related death (adjusted hazard ratio, 3.24; 95% confidence interval 1.65–6.67; p < 0.01). The % V ˙ E vs. V ˙ CO2 slope can be used for risk stratification in patients with CHF and an LVEF < 45%. [ABSTRACT FROM AUTHOR]

Intelligent regulation for human exercise behaviors becomes significantly necessary for exercise medicine after the COVID-19 epidemic. The key issue of exercise regulation and its potential development for intelligent exercise is to describe human exercise physiological behaviors in a more accurate and sufficient manner. Here, a non-parametric modeling method with kernel-based regularization is presented to estimate cardiorespiratory biomarkers (i.e., oxygen uptake (V̇O2) and carbon dioxide output (V̇O2) by merely non-invasively monitoring the indicator of exercise intensity (e.g., walking speed). Using the kernel-based non-parametric modeling, we show that V̇O2 and V̇O2 behaviors in response to continuous and diversified exercise intensity stimulations can be quantitatively described. Furthermore, the dataset from the stairs experiment with a proper protocol is applied in the kernel parameter selection, and this selection approach is compared with the numerical simulation approach. The comparison results illustrate an improvement of 4.18% for oxygen uptake and 7.63% for carbon dioxide output in a half period, and 11.00% for oxygen uptake and 12.60% for carbon dioxide output in one period when using the kernel parameter selected from the stairs exercise. Moreover, the advantages of using the non-parametric model, the necessity of sufficient stimulation for identification and the importance of the kernel regularization term are also addressed in this paper. This method provides fundamental work for the practice of intelligent exercise.

The use of automated gas exchange analysis systems in exercise studies is common throughout the industrialized world and are frequently used in sports medicine laboratories for the measurement of maximal oxygen uptake (VO2max), as an integrative parameter that allows the physical condition to be assessed, in spite of its limitations. Actually, the fundamental principles behind the measurement of respiratory gas exchange (RGE) have not changed for a century. It was used a manual Douglas bag method together with separate chemical analyses. The need for faster and more efficient techniques, has conditioned the traditional procedures and determined the emergence of automated systems. However, the validity and reliability of all these different systems is not well known. The common features associates with these systems, also have disadvantages that must be evaluated at the time of the acquisition of an automated equipment: (1) regular quality control checks, which entails other added economic costs, (2) the validity and reliability of the results, which it is necessary to verify, and (3) the user does not know the equations that determine the values of oxygen consumption and carbon dioxide production. This work aims to clarify the disadvantages of these automated systems. At maximum intensities, the variation of VO2max or VO2peak can be very significant in athletes and even more relevant in sick people undergoing a training program. Therefore, considerable care is needed when comparing RGE data with automated systems.New and NoteworthyActually, stress tests are more conveniently performed with automated systems. It is necessary to examine the validity and reliability of automated respiratory gas exchange systems. The algorithms incorporated in the software, apart from being a “mystery,” show differences with respect to the data provided.

The use of automated gas exchange analysis systems in exercise studies is common throughout the industrialized world and are frequently used in sports medicine laboratories for the measurement of maximal oxygen uptake (VO2max), as an integrative parameter that allows the physical condition to be assessed, in spite of its limitations. Actually, the fundamental principles behind the measurement of respiratory gas exchange (RGE) have not changed for a century. It was used a manual Douglas bag method together with separate chemical analyses. The need for faster and more efficient techniques, has conditioned the traditional procedures and determined the emergence of automated systems. However, the validity and reliability of all these different systems is not well known. The common features associates with these systems, also have disadvantages that must be evaluated at the time of the acquisition of an automated equipment: (1) regular quality control checks, which entails other added economic costs, (2) the validity and reliability of the results, which it is necessary to verify, and (3) the user does not know the equations that determine the values of oxygen consumption and carbon dioxide production. This work aims to clarify the disadvantages of these automated systems. At maximum intensities, the variation of VO2max or VO2peak can be very significant in athletes and even more relevant in sick people undergoing a training program. Therefore, considerable care is needed when comparing RGE data with automated systems. New and Noteworthy: Actually, stress tests are more conveniently performed with automated systems. It is necessary to examine the validity and reliability of automated respiratory gas exchange systems. The algorithms incorporated in the software, apart from being a "mystery," show differences with respect to the data provided. [ABSTRACT FROM AUTHOR]

Dyspnea on exertion is a commonly encountered problem in clinical practice. It is usually investigated by resting tests such as pulmonary function tests and echocardiogram, which may at times can be non-diagnostic. Cardiopulmonary exercise testing (CPET) measures physiologic parameters during exercise which can enable accurate identification of the cause of dyspnea. Though CPET has been around for decades and provides valuable and pertinent physiologic information on the integrated cardiopulmonary responses to exercise, it remains underutilized. The objective of this review is to provide a comprehensible overview of the underlying principles of exercise physiology, indications and contraindications of CPET, methodology and interpretative strategies involved and thereby increase the understanding of the insights that can be gained from the use of CPET.

Dyspnea on exertion is a commonly encountered problem in clinical practice. It is usually investigated by resting tests such as pulmonary function tests and echocardiogram, which may at times can be non-diagnostic. Cardiopulmonary exercise testing (CPET) measures physiologic parameters during exercise which can enable accurate identification of the cause of dyspnea. Though CPET has been around for decades and provides valuable and pertinent physiologic information on the integrated cardiopulmonary responses to exercise, it remains underutilized. The objective of this review is to provide a comprehensible overview of the underlying principles of exercise physiology, indications and contraindications of CPET, methodology and interpretative strategies involved and thereby increase the understanding of the insights that can be gained from the use of CPE [ABSTRACT FROM AUTHOR]

Purpose: Cardiopulmonary exercise testing (CPET) is increasingly used as a biomarker of fitness in children. Maximal or peak values remain the most common variables obtained in CPET, but these physiologically challenging high-intensity work rates (WR) are often not achieved. We hypothesized that interactions of gas exchange, heart rate (HR), and WR CPET variables (slopes) could yield useful mechanistic and clinical insights that might enhance the clinical utility of CPET in children. We further hypothesized that the dependence of the slope on body mass could be predicted by the first-principle analysis of body size and physiological response. Methods: One hundred and sixty-nine healthy participants (8-18 yr old, body mass index <95th percentile, 82 females) underwent dual x-ray absorptiometry scan to estimate lean body mass (LBM) and performed a ramp-type progressive cycle ergometry exercise protocol with a breath-by-breath measurement of gas exchange. Linear regression was used to calculate the slopes among ̇VO2, ̇CO2, ̇VE, HR, and WR. Results: ΔWR/ΔHR (r = 0.87) and Δ̇VO2/ΔHR (r = 0.96) were strongly correlated with ̇VO2peak, whereas Δ̇VO2/ΔWR (r = 0.42) and ȦVE/ȦVCO2 (r = -0.51) were mildly correlated with peak values. LBM was more highly correlated with those slopes predicted to be body size dependent (P < 0.0001) compared with total body mass. Conclusions: The data largely supported our original hypotheses. Unlike peak or maximal values, which are derived from no more than a few data points at the end of a progressive exercise test, the CPET slopes were calculated from a much larger data set obtained throughout the test. An analysis of these slopes might ultimately prove useful clinically and in research studies when peak values are not achieved. [ABSTRACT FROM AUTHOR]

Abstract: Background: Hypercapnia can result from carbon dioxide pneumoperitoneum and adversely affect the postoperative period, particularly in morbidly obese patients. The purpose of the present study was to examine carbon dioxide homeostasis using a metabolic monitor in morbidly obese and normal weight patients during laparoscopic surgical procedures. The setting was a university hospital in Italy. Methods: The data from 25 patients with a body mass index of 47.7 ± 5.5 kg/m2 undergoing laparoscopic gastric mini-bypass were compared with the data from 25 normal weight patients undergoing laparoscopic cholecystectomy. The minute ventilation was adjusted to maintain a normal arterial partial pressure of carbon dioxide and normal end-tidal partial pressure of carbon dioxide throughout surgical procedures. The arterial partial pressure of carbon dioxide, end-tidal partial pressure of carbon dioxide, total exhaled carbon dioxide per minute, and arterial blood gas analysis were obtained at 10-minute intervals, along with other cardiorespiratory parameters. Results: The total exhaled carbon dioxide per minute increased by the same percentage in both groups (around 20%). In the laparoscopic cholecystectomy patients, a definite plateau in the total exhaled carbon dioxide per minute was observed within 20 minutes from the start of pneumoperitoneum but not in the morbidly obese patients. After desufflation, the total exhaled carbon dioxide per minute returned more rapidly to the baseline values in the laparoscopic cholecystectomy group than in the morbidly obese group (17.4 ± 6.2 and 24.1 ± 8.3 min, respectively). Conclusion: The results of our study have shown that the load of carbon dioxide insufflated is well tolerated in morbidly obese patients, as well as in normal patients, with proper intraoperative ventilation adjustments. However, after pneumoperitoneum, the return to a normal total exhaled carbon dioxide per minute required a longer period in the morbidly obese group. Prolonged mechanical ventilation is therefore advisable in morbidly obese patients. [Copyright &y& Elsevier]

The article focuses on the Candidate Physical Ability Test (CPAT) for firefighters in North America. It mentions that though CPAT is used to screen firefighters with their minimal physical capabilities for firefighting, it still overlooked the aspect of physiological demand in potential candidates. It states that to be able to determine the physiological demands of firefighters for the said test, a study was conducted that examines the oxygen uptake, carbon dioxide output, and heart rate responses on actual candidates undergoing the physical test. Moreover, it was revealed that CPAT covers both the aerobic and anaerobic energy supply systems that affect the candidate firefighters during firefighting simulations.

We examined the oxygen uptake (VO2) and carbon dioxide output (VCO2) during completion of a circuit developed for testing fire fighters and related performance time to laboratory measures of fitness. Twenty-two healthy university students (ten women) were trained in the tasks then performed the circuit as quickly as possible. Breath-by-breath gas exchange and heart rate were continuously measured with a portable system. Median circuit time was 6:13 (min:s, 25-75% = 5:46-6:42) for men and 7:25 (25-75% = 6:49-10:21) for 8 women finishers (P = 0.023), and VO2 averaged 68 and 64% VO2max for the men and women during the circuit. Both men and women had high respiratory exchange ratios (>1.0) suggesting marked anaerobic energy contribution. Physiological variables associated with circuit time were assessed by backward stepwise regression yielding a significant model that included only peak work rate during arm cranking exercise as a function of circuit completion time across men and women combined (P < 0.001). For men, but especially for women, the time required for the simulated victim drag (68.2 kg mannequin) was positively correlated with total time to complete the other circuit elements (r = 0.51, r = 0.96 respectively). The simple correlation between circuit time and VO2max (mL/kg/min) revealed poor relationships for men (r = -0.37, P > 0.05) and women (r = 0.20, P > 0.05). These data demonstrated that upper body fitness as reflected by peak work rate during arm cranking correlated with total circuit time for the men and women in our population sample. [ABSTRACT FROM AUTHOR]

The purpose of the study was to characterise statistically the inherent fluctuations in breath-by-breath measurements of pulmonary gas exchange (oxygen uptake and carbon dioxide output, VO2 and VCO2, respectively) and pulmonary ventilation (VE) in patients with chronic obstructive pulmonary disease (COPD) and to compare them with those of healthy control subjects. Thirty subjects with COPD [mean (SD): 67 (6) years old; forced expiratory volume in 1 min, FEV1 1.25( 0.18) l; 42 (6)% predicted FEV1] and 12 healthy subjects [31 (3) years old; FEV1 3.62 (0.54) l; 99 (8)% predicted FEV1] performed exercise tests on a cycle ergometer at a constant work rate of moderate intensity. Steady-state exercise values for VO2, VCO2 and VE were 905 (96) ml·min–1, 847(90) ml·min–1 and 23 (3) l·min–1, respectively for the COPD patients and 1239(89) ml·min–1, 1191(84) ml·min–1 and 37(3) l·min–1, respectively, for the healthy controls. The breath-by-breath fluctuations were well characterised by a Gaussian density-probability function with breath-to-breath autocorrelations that were not significantly different from 0, up to four subsequent breaths. Its magnitude varied among variables, but was independent of the signal amplitude for the same subject and variable. With ratios of amplitude of fluctuation:signal of around 10%, typical of the patients studied, the resolution of time constants and amplitude were ≅9 s and ≅100 ml·min–1, respectively for VO2 or VCO2 with one repetition. [ABSTRACT FROM AUTHOR]

To be clinically useful as indices reflective of altered physiological function consequent to interventions in patients with chronic obstructive pulmonary disease (COPD), the time constant (τ) and steady-state amplitude of the kinetic responses for oxygen uptake (VO2) carbon dioxide output (VCO2) ventilation (VE) and heart rate (HR) have to be appropriately differentiable and reproducible. We therefore assessed the reproducibility of τ and steady state amplitude values in 41 patients with severe COPD [mean (SD)] [forced expiratory volume in 1 s=41 (7)% predicted], aged 64 (5) years. Of the total, 6 of the patients (15%) did not produce breath-by-breath data of sufficient quality to warrant kinetic analysis. The remaining 35 patients completed two moderate-intensity 10 mm square-wave exercise tests separated by 2 h, both before and after an endurance training programme. Tests were conducted on an electromagnetically-braked cycle ergometer at an exercise intensity corresponding to 80% of the estimated lactate threshold (θLa) or 50% of peak oxygen uptake if °La was insufficiently differentiable. Breath-by-breath measurements of VO2, VCO2, VE and HR were averaged into 10 s bins and the on-transient response kinetics were estimated using a mono-exponential model. Analysing the pre-training and the post-training test 1 and test 2 comparisons together, the test 1-test 2 differences were not significantly different from 0 for either τ or A. The standard deviation of the test 1-test 2 differences allowed us to define the magnitude of change that would reach statistical significance. For τ, this averaged some 8, 10, 11 and 8 s, for VO2, VCO2, VE and HR, respectively, for a one-tailed paired-comparisons test (i.e. appropriate for assessing hypothesised improvements resulting from an intervention); for a two-tailed comparison, the differences were approximately 2 s greater. The corresponding one-tailed values for A were 100 ml·min-1, 95 ml·min-1, 2.5 1 mm-1 and 4 beats·min-1, respectively; the two-tailed values were 10%-15% greater. We therefore conclude that both τ and A for moderate-intensity exercise can be reproducibly estimated in patients with COPD when the data set provides a sufficiently large amplitude of response and sufficiently low sample variability to allow appropriate parameter estimation. [ABSTRACT FROM AUTHOR]

A self-calibrating fully automatic instrument for the measurement of oxygen consumption, carbon dioxide production and the respiratory quotient of mechanically ventilated patients has been developed. The instrument is based on commercially available conventional oxygen and carbon dioxide gas analysers and a domestic natural gas volumetric flow meter. The distribution of the different gas flows, i.e. calibration gases, the inspiratory mixture sample and the expiratory mixture sample, are controlled by in inexpensive microprocessor, which also performs the necessary calculations. The accuracy of the instrument has been validated by bench tests. The present prototype has been in use for over 3000 h without major failures. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to determine whether the linear relationship between CO2 output ( V˙CO2) and pulmonary ventilation ( V˙E) is altered during incremental cycling performed after exercise-induced metabolic acidosis. Ten untrained, female subjects performed two incremental cycling tests (15 W · min−1 up to 165 W) on separate days. One incremental exercise test was conducted without prior exercise, whereas the other test was preceded by a 1-min bout of maximal cycling. The ventilatory equivalent for O2 ( V˙E/ V˙O2) was only elevated above control values at 15–60 W during incremental cycling performed after high-intensity exercise. In contrast, the ventilatory equivalent for CO2 ( V˙E/ V˙CO2) was significantly increased above control levels at nearly every work stage of incremental work (all except 165 W). Hyperventilation relative to V˙CO2 was confirmed by the significantly lower end-tidal CO2 tension ( PETCO2) obtained throughout the incremental cycling that was performed after high-intensity exercise (except at 165 W). V˙E and V˙CO2 were significantly correlated under both treatment conditions ( r > 0.99; P < 0.001). Moreover, both the slope and y-intercept of the linear regression were found to be significantly elevated during the incremental cycling performed after high-intensity cycling compared to control conditions ( P < 0.01). The increase in the slope of the V˙E- V˙CO2 relationship during incremental exercise performed under these conditions does not represent an uncoupling of V˙E from V˙CO2, but could be accounted for by the significantly lower PETCO2 observed during exercise. [ABSTRACT FROM AUTHOR]

An estimated average CO2 output from Etna's summit craters in the range of 13±3 Mt/a has recently been determined from the measured SO2 output and measured CO2/SO2 molar ratios. To this amount the CO2 output emitted diffusely from the soil (≈ 1 Mt/a) and the amount of CO2 dissolved in Etna's aquifers (≈ 0.25 Mt/a) must be added. Data on the solubility of CO2 in Etnean magmas at high temperature and pressure allow the volume of magma involved in the release of such an amount of this gas to be estimated. This volume of magma (≈ 0.7 km3/a) is approximately 20 times greater than the volume of magma erupted annually during the period 1971–1995. On the basis of C-isotopic data of CO2 collected in the Etna area and of new hypotheses on the source of Mediterranean magmas, significant contributions of CO2 from non-magmatic sources to the total output from Etna are unlikely. Such large outputs of CO2 and also of SO2 from Etna could be due to an anomalously shallow asthenosphere beneath the volcano that allows a continuous escape of gases toward the surface, even without migration of magma. [ABSTRACT FROM AUTHOR]

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Carbon included in coke and coal was used as a reduction agent and fuel in blast furnace (BF) ironmaking processes, which released large quantities of carbon dioxide (CO2). Minimizing the carbon consumption and CO2 output has always the goal of ironmaking research. In this paper, the reduction reactions of iron oxides by carbon, the gasification reaction of carbon by CO2, and the coupling reactions were studied by thermodynamic functions, which were derived from isobaric specific heat capacity. The reaction enthalpy at 298 K could not represent the heat value at the other reaction temperature, so the certain temperature should be confirmed by Gibbs frees energy and gas partial pressure. Based on Hess' law, the energy consumption of the ironmaking process by carbon was calculated in detail. The decrease in the reduction temperature of solid metal iron has been beneficial in reducing the sensible heat required. When the volume ratio of CO to CO2 in the top gas of the furnace was given as 1.1–1.5, the coupling parameters of carbon gasification were 1.06–1.28 for Fe2O3, 0.71–0.85 for Fe3O4, 0.35–0.43 for FeO, respectively. With the increase in the coupling parameters, the volume fraction of CO2 decreased, and energy consumption and CO2 output increased. The minimum energy consumption and CO2 output of liquid iron production were in the reduction reactions with only CO2 generated, which were 9.952 GJ/t and 1265.854 kg/t from Fe2O3, 9.761 GJ/t and 1226.799 kg/t from Fe3O4, 9.007 GJ/t and 1107.368 kg/t from FeO, respectively. Compared with the current energy consumption of 11.65 GJ/t hot metal (HM) and CO2 output of 1650 kg/tHM of BF, the energy consumption and CO2 of ironmaking by carbon could reach lower levels by decreasing the coupled gasification reactions, lowering the temperature needed to generate solid Fe and adjusting the iron oxides to improve the iron content in the raw material. This article provides a simplified calculation method to understand the limit of energy consumption and CO2 output of ironmaking by carbon reduction iron oxides. [ABSTRACT FROM AUTHOR]

Purpose: This study examined the properties of the recovery processes of respiratory gases after breath-holding (BH) during exercise. We particularly focused on the time courses of minute carbon dioxide output (VC02) and minute oxygen uptake (VC02) after cessation of BH and examined how they were changed by the degree of exercise loads. Methods: Exercise tests were carried out with a bicycle ergometer for 8 healthy male athletes and the ventilation activities and expired gases were measured with a breath-by-breath based aeromonitor. The respiratory responses to 20 s BH were recorded during continuous cycling at each of three exercise loads. Mono- and hi-exponential decay functions with two parameters (initial amplitude A and rate constant a) and four parameters (A, B. and a, f.3 ), respectively, were fitted to the data of VCO2 and VO2 after cessation of the BH. AIC was used for model selection. Results and Discussion: VC02 and V02 after the BH, transiently increased and thereafter returned to a steady-state. The values immediately after BH and the decay rates to the steady-state level became larger as increase in load. When the two models were compared with AIC, th.e hi-expone. ntial decay model was selected for both VCO an.d V02. Wh.e reas the load dependencies of α, β of VCO2 and VO2 were very similar, those of A and B were different. This result may be explained by different sizes of tissue distribution volume of carbon dioxide and oxygen. [ABSTRACT FROM AUTHOR]