Oxygen Uptake Efficiency Research Articles

Predictive Role of Atrial Strain, Aortic Stiffness, and Muscle-Related Factors for Maximal and Submaximal Exercise Capacity in Fontan Patients.

Fontan patients' exercise capacity and associated risks of morbidity and mortality necessitate a comprehensive study. We aim to explore maximal and submaximal exercise capacity, assessing the impact of cardiovascular and peripheral factors, including atrial strain, aortic stiffness, and muscle-related factors. Fontan patients and matched controls were examined. Clinical details were recorded, and atrial strain and aortic stiffness were measured using echocardiography. Hand grip and knee extensor strength were assessed, and muscle oxygenation was recorded. Cardiopulmonary exercise test determined exercise capacity, with peak oxygen uptake/kg (VO2/kg) and oxygen uptake efficiency slope/kg (OUES/kg) as markers for maximal and submaximal capacity, respectively. Thirty-one Fontan patients (median age = 18, range = 7-31years) and 30 controls (median age = 18, range = 7-32years) were studied. No significant differences in body composition and muscle strength were observed between Fontan patients and controls (p > 0.05). Fontan patients exhibited lower peak VO2/kg and OUES/kg (p < 0.001 for both), along with decreased atrial strain and increased aortic stiffness compared to controls (p < 0.001). Aortic pulse wave velocity (PWV), left atrial strain contractile phase (LASct), and knee extensor strength independently predicted peak VO2/kg (R2 = 0.514) and OUES/kg (R2 = 0.486) in Fontan patients; age was a predictor for peak VO2/kg. Atrial contractile strain, aortic stiffness, and knee extensor muscle strength are predictors of submaximal exercise capacity; furthermore, age, along with these variables, serves as predictors of maximal exercise capacity in Fontan patients. Evaluating hemodynamic, vascular, and muscular parameters, in conjunction with assessing both maximal and submaximal exercise capacities, is crucial for optimizing disease management in Fontan patients. Clinicaltrials.gov registration: NCT05011565.

Exercise stress testing recovery kinetics: the forgotten phase

Abstract Background Impaired exercise capacity is a cardinal feature of heart failure (HF). Peak oxygen uptake (pVO2) and ventilatory efficiency (VE/VCO2 slope) during exercise are well-consolidated prognostic markers in patients with HF. A previous study suggested that abnormally prolonged VO2 recovery, specifically the failure to decrease VO2 from peak exercise by 10.5 mL/kg/min at 180 seconds of the recovery phase, predicts adverse outcomes in HF. However, it is unknown to what extent the recovery of VEqCO2, a marker of ventilation/perfusion mismatch, adds prognostic value to the already existing parameters. Purpose The aim of this study was to characterize the functional and prognostic significance of VEqCO2 kinetics following peak exercise in individuals with HF. Methods This retrospective single-center study included consecutive adult patients with chronic (&amp;gt;3 months) and stable HF with left ventricular ejection fraction (LVEF) &amp;lt;50% who underwent cardiopulmonary exercise testing (CPET) between 2015 and 2020. Following maximal exercise, patients recovered over a 3-minute period (walking 2km/h for 1 minute and sittng passively for 2 minutes). VO2 and VEqCO2 kinetics during recovery, described as the absolute difference to peak VO2 (difVO2) and VEqCO2 (difVEqCO2), were measured at 30, 60, 120, and 180 seconds. Outcomes were assessed as a composite of cardiovascular (CV) death, urgent cardiac transplant, or left ventricular assist device (LVAD) implantation at 1 year. Results A total of 238 patients were included (mean age 58 ± 12 years; 82% males; mean LVEF 34 ± 10%; 68% with ischemic HF; 75% in NYHA class II-III; mean pVO2 18 ± 6 mL/kg/min; mean VE/VCO2 slope 41 ± 12). During the 1-year follow-up, 19 patients met the endpoint (8 CV deaths, 8 urgent heart transplants, and 3 LVAD). ROC curve analysis showed that the best correlation between difVEqCO2 and outcomes was apparent at difVEqCO2 of 180 seconds (AUC 0.83) with a cut-off value of 1 (sensitivity 93%, specificity 58%). These patients, who had a decrease in VEqCO2 (difVEqCO2 &amp;gt;1) at 180 seconds, were significantly older (p=0.02), had a lower LVEF (p&amp;lt;0.001), and higher NYHA (p&amp;lt;0.001). They were at an increased risk of cardiovascular events compared to those with an increase in VEqCO2 (difVEqCO2 &amp;lt;1) at 180 seconds (event-free survival at 1 year 86% vs. 98%, log-rank p&amp;lt;0.001). In multivariate analysis, the statistical association between difVEqCO2 and outcomes remained significant, even after adjusting for difVO2 at 180 seconds (HR 4.315, CI95% (1.349-13.804), p=0.014). Conclusion Abnormal VEqCO2 kinetics in the recovery period of CPET is an easily recognizable non-invasively derived measurement that predicts outcomes in HF. VEqCO2 may complement the evaluation of VO2 and other parameters during recovery to further improve prognostic risk stratification in HF.

The Oxygen Uptake Efficiency Slope Does Not Accurately Predict VO2peak In Young Children

The Oxygen Uptake Efficiency Slope Does Not Accurately Predict VO2peak In Young Children

Physiopathology of High-Altitude Pulmonary Edema.

The air-blood barrier is well designed to accomplish the matching of gas diffusion with blood flow. This function is achieved by maintaining its thickness at ∼0.5 µm, a feature implying to keep extravascular lung water to the minimum. Exposure to hypobaric hypoxia, especially when associated with exercise, is a condition potentially leading to the development of the so-called high-altitude pulmonary edema (HAPE). This article presents a view of the physiopathology of HAPE by merging available data in humans exposed to high altitude with data from animal experimental approaches. A model is also presented to characterize HAPE nonsusceptible versus susceptible individuals based on the efficiency of alveolar-capillary oxygen uptake and estimated morphology of the air-blood barrier.

The oxygen uptake efficiency slope does not accurately predict O2peak of children - the Arkansas Active Kids study.

Cardiorespiratory fitness (CRF) is a vital indicator of health. However, accurately measuring peak oxygen consumption ( O2peak) to determine CRF in children can be challenging. The oxygen uptake efficiency slope (OUES) has been proposed as an alternative metric for predicting O2peak in children, but its accuracy and agreement with measured O2peak remain unclear. A post hoc analysis was conducted in 94 children (ages 7-10years) who completed an incremental cycle ergometer test to measure O2peak. Body composition (Dual-energy X-ray absorptiometry) was measured, and fat mass index (FMI, kg/m2) and fat-free mass index (FFMI, kg/m2) were calculated. OUES was determined using all respiratory data (OUES100%) collected during the cycle ergometer test and using data only up to 60% of heart rate reserve (OUES60%HRR). Regression equations to predict O2peak (Pred- O2peak) were derived from simple and multiple linear regression analysis. Bland-Altman analysis assessed the level of agreement between Pred- O2peak and measured O2peak. OUES60%HRR (β = 0.46, p < 0.0001), age (β = 56.0, p = 0.0004), White race (β = 173.3, p < 0.0003), FFMI (β = 0.98.6, p < 0.000), and FMI (β = -0.40.8, p < 0.000) were retained in the final model. The difference between measured O2peak and Pred- O2peak was not different from zero (p = 0.999). There was a positive association between the difference of measured O2peak and Pred- O2peak and the average of the two methods (β = 0.79, p = 0.0028). There was no mean bias between measured O2peak and Pred- O2peak. However, magnitude bias was present even after considering other significant predictors of O2peak (FMI, FFMI, race, and age) in the regression equation. Caution is advised when using OUES to predict O2peak in children.

Oxygen uptake efficiency slope at anaerobic threshold can predict peak VO2 in adult congenital heart disease

IntroductionAssessment of exercise capacity by cardiopulmonary exercise testing (CPET) in adults with congenital heart disease (CHD) is important for prognostication and preoperative assessment. Peak oxygen uptake (PVO2) is used commonly, but can be challenging due to the difficulties of undertaking maximal CPET testing in this population. We explored whether oxygen uptake efficiency slope (OUES) at ventilatory anaerobic threshold (VAT), the point during CPET at which OUES becomes strongly correlated with PVO2, and is more reliably available from submaximal CPET, can predict PVO2 in adults with CHD. MethodsWe assessed consecutive individuals who completed maximal CPET at our cardiorespiratory centre, as part of routine service review, between March 2019 and August 2021, recording data such as PVO2, VAT and OUES at various proportions of a maximal test (75 %, 90 %, 100 %, and VAT). We employed linear regression modelling to analyse the association between PVO2 and OUES at VAT, and subsequently create an equation to predict PVO2 from OUES at VAT. Parametric data are presented using Pearson's correlation coefficient and non-parametric data using Spearman's rho. ResultsWe analysed 391 individuals (177 female, age 32 ± 11 years). Mean ± SD PVO2 was 23.3 ± 6.86 ml/min/kg or 1724 ± 540 ml/min, peak VE 86.7 ± 25.4 l/min. The point of VAT as a percentage of PVO2 achieved was 66.5 ± 9.4 %, and VAT as a percentage of predicted PVO2 46.9 ± 11.4 %. PVO2 was correlated with OUES at 100 % (R = 0.91, P < .001), 90 % (R = 0.91, P < .001), 75 % (R = 0.89, P < .001) of maximum, and VAT (R = 0.83, P < .001). PVO2(ml/min) could be predicted by: (OUES at VAT)∗685.245 + (BMI [kg/m2])∗5.045 + (FEV1[l])∗223.620 – 153.205. ConclusionsOUES at VAT can be used to calculate PVO2. To our knowledge, this is the first equation using OUES at VAT to predict PVO2 in adults with CHD. In a population who may find maximal CPET difficult, this may be a useful submaximal measurement of cardiovascular fitness, and to calculate PVO2, which is commonly used in guideline-based decision making in CHD.

Prognostic value of cardiopulmonary exercise test in children with congenital heart defects

BackgroundCardiopulmonary exercise testing (CPET) has an important prognostic value in adults with different congenital heart defects (CHDs) and is a useful tool for risk stratification and clinical decision-making. In this...

Oxygen uptake efficiency plateau is unaffected by fitness level - the NOODLE study

BackgroundEndurance athletes (EA) are an emerging population of focus for cardiovascular health. The oxygen uptake efficiency plateau (OUEP) is the levelling-off period of ratio between oxygen uptake (VO2) and ventilation (VE). In the cohort of EA, we externally validated prediction models for OUEP and derived with internal validation a new equation.Methods140 EA underwent a medical assessment and maximal cycling cardiopulmonary exercise test. Participants were 55% male (N = 77, age = 21.4 ± 4.8 years, BMI = 22.6 ± 1.7 kg·m− 2, peak VO2 = 4.40 ± 0.64 L·min− 1) and 45% female (N = 63, age = 23.4 ± 4.3 years, BMI = 22.1 ± 1.6 kg·m− 2, peak VO2 = 3.21 ± 0.48 L·min− 1). OUEP was defined as the highest 90-second continuous value of the ratio between VO2 and VE. We used the multivariable stepwise linear regression to develop a new prediction equation for OUEP.ResultsOUEP was 44.2 ± 4.2 mL·L− 1 and 41.0 ± 4.8 mL·L− 1 for males and females, respectively. In external validation, OUEP was comparable to directly measured and did not differ significantly. The prediction error for males was − 0.42 mL·L− 1 (0.94%, p = 0.39), and for females was + 0.33 mL·L− 1 (0.81%, p = 0.59). The developed new prediction equation was: 61.37–0.12·height (in cm) + 5.08 (for males). The developed model outperformed the previous. However, the equation explained up to 12.9% of the variance (R = 0.377, R2 = 0.129, RMSE = 4.39 mL·L− 1).ConclusionOUEP is a stable and transferable cardiorespiratory index. OUEP is minimally affected by fitness level and demographic factors. The predicted OUEP provided promising but limited accuracy among EA. The derived new model is tailored for EA. OUEP could be used to stratify the cardiorespiratory response to exercise and guide training.

Adoption of the cardiopulmonary exercise test in the exercise ability and cardiopulmonary function rehabilitation of coronary artery disease (CAD) patients

BackgroundThis study aimed to explore the application of cardiopulmonary exercise testing in coronary artery disease (CAD) patients, evaluate its impact on exercise ability and cardiopulmonary function in patients with coronary heart disease (CHD), and promote the application of cardiopulmonary exercise testing in CAD management.MethodsFifty CHD patients after percutaneous coronary intervention (PCI) were recruited and randomly enrolled into the control (Ctrl) group and intervention (Int) group. Routine health education and health education combined with RT training were carried out for the two groups. Blood lipid levels and lung function were compared between the two groups after intervention. Cardiac function was evaluated by Doppler ultrasonography, and cardiopulmonary fitness and exercise ability were evaluated by a cardiopulmonary exercise test (CPET). The self-rating anxiety scale (SAS) and self-rating depression scale (SDS) were employed to evaluate negative emotions. The 36-item short-form (SF-36) was adopted to evaluate quality of life.Result: Compared with those in the Ctrl group, the levels of serum total cholesterol (TC), triglycerides (TGs), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) decreased in the Int group, while the levels of high-density lipoprotein increased (P < 0.05). The quantitative load results showed that compared with the Ctrl group, the heart rate (HR) and self-perceived fatigue degree of the Int group decreased, and the ST segment increased (P < 0.05). Compared with the Ctrl group, the left ventricular ejection fraction (LVEF), forced expiratory volume at 1 s (FEV1), ratio of forced expiratory volume to forced vital volume (FEV1/FVC%), and maximum chase volume (MVV) increased in the Int group, while the left ventricular end diastolic diameter and left ventricular end contractile diameter decreased (P < 0.05). The results of the CPET showed that compared with the Ctrl group, minute ventilation/carbon dioxide production slope, VE/VCO2 − Peak, anaerobic threshold (AT), peak oxygen pulse (VO2/HR peak), oxygen uptake efficiency platform (OUEP), increasing power exercise time (IPEt), HR recovery 1 min after exercise, peak load power (Watt peak), and value metabolic equivalent (Watt peak) increased in the Int group (P < 0.05). Compared with the Ctrl group, the SAS and SDS scores in the Int group decreased (P < 0.05). The results of the quality of life evaluation showed that compared with the Ctrl group, the score of the SF-36 dimensions increased in the Int group (P < 0.05).ConclusionRT training can reduce postoperative blood lipid and quantitative load levels in CAD patients and improve adverse mood. Furthermore, it can improve patients’ cardiopulmonary function, cardiopulmonary fitness, exercise ability, and quality of life.

Association of Sarcopenia and Oxygen Uptake Efficiency Slope in Male Patients With Heart Failure.

Sarcopenia, the loss of muscle mass and function, is a common comorbidity in patients with heart failure (HF). The skeletal muscle modulates the respiratory response during exercise. However, whether ventilatory behavior is affected by sarcopenia is still unknown. We enrolled 169 male patients with HF. Muscle strength was measured by a handgrip dynamometer. Body composition was measured with dual-energy X-ray absorptiometry. Sarcopenia was defined by handgrip strength <27 kg and appendicular lean mass divided by height squared (ALM/height 2 ) <7.0 kg/m 2 . Oxygen uptake efficiency slope (OUES), ventilation (VE), oxygen uptake (VO 2 ), and carbon dioxide output (VCO 2 ) were measured by a cardiopulmonary exercise test. Sarcopenia was identified in 29 patients (17%). At the first ventilatory threshold, VE/VO 2 (36.9±5.9 vs 32.7±6.5; P =.003) and VE/VCO 2 (39.8±7.2 vs 35.3±6.9; P =.004) were higher in patients with sarcopenia compared to those without sarcopenia. At the exercise peak, compared to patients without sarcopenia, patients with sarcopenia had lower OUES (1186±295 vs 1634±564; P <.001), relative VO 2 (16.2±5.0 vs 19.5±6.5 mL/kg/min; P =.01), and VE (47.3±10.1 vs 63.0±18.2L/min; P <.0001), while VE/VCO 2 (42.9±8.9 vs 38.7±8.4; P =.025) was increased. OUES was positively correlated with ALM/height 2 ( r =0.36; P <.0001) and handgrip strength ( r =0.31; P <.001). Hemoglobin (OR=1.149; 95% CI, 0.842-1.570; P =.038), ALM/height 2 (OR=2.166; 95% CI, 1.338-3.504; P =.002), and VO 2peak (OR=1.377; 95% CI, 1.218-1.557; P <.001) were independently associated with OUES adjusted by cofounders. Our results suggest that sarcopenia is related to impaired ventilatory response during exercise in patients with HF.

Oxygen uptake efficiency slope in 8- to 12-year-old boys and girls.

Oxygen uptake efficiency slope (OUES) is an objective physiological measure that can be obtained from a standard graded exercise test. However, there is conflicting evidence regarding sex differences in OUES values in children. Therefore, this study investigated potential sex differences in absolute, ratio-scaled, and allometrically scaled OUES in 8.0- to 12.0-year-old children. Retrospective and prospective data of 18 boys and 22 girls were utilized. All participants had undergone familiarization before performing a maximal cycle ergometer test to determine OUES. These values were also ratio-scaled and allometrically scaled to mass and body surface area (BSA). Group differences were tested via independent sample t-tests (or Mann-Whitney U if not normally distributed). Absolute OUES values (VO<inf>2</inf> mL∙min-1/log<inf>10</inf>VE L∙min-1) were significantly higher in boys compared to girls (1860.8±359.3 vs. 1514.3±212.6). When scaled to mass (VO<inf>2</inf> mL∙kg-1∙min-1/log<inf>10</inf>VE L∙kg-1∙min-1), OUES was no longer significantly different between groups, but when scaled to BSA (VO<inf>2</inf> mL∙m-2∙min-1/log<inf>10</inf>VE L∙m-2∙min-1), OUES was significantly higher in the boys than the girls (1414.4±204.2 vs. 1268.9±134.6). When allometry was applied for mass (OUES/mass0.444) boys had significantly higher value than girls (350.8±46.7 vs. 305.0±31.5). The present study demonstrated that boys had greater OUES values scaled to BSA and allometrically scaled to body mass. These findings provide further evidence of sex differences with OUES values in preadolescent children and implies the need for sex-specific reference values prior to using OUES for the assessment of cardiorespiratory pathology in children.

Persisting exercise ventilatory inefficiency in subjects recovering from COVID-19. Longitudinal data analysis 34 months post-discharge

BackgroundSARS-CoV-2 infection has raised concerns about long-term health repercussions. Exercise ventilatory inefficiency (EVin) has emerged as a notable long-term sequela, potentially impacting respiratory and cardiovascular health. This study aims to assess the long-term presence of EVin after 34 months and its association with cardiorespiratory health in post-COVID patients.MethodsIn a longitudinal study on 32 selected post-COVID subjects, we performed two cardiopulmonary exercise tests (CPETs) at 6 months (T0) and 34 months (T1) after hospital discharge. The study sought to explore the long-term persistence of EVin and its correlation with respiratory and cardiovascular responses during exercise. Measurements included also V̇O2peak, end-tidal pressure of CO2 (PETCO2) levels, oxygen uptake efficiency slope (OUES) and other cardiorespiratory parameters, with statistical significance set at p < 0.05. The presence of EVin at both T0 and T1 defines a persisting EVin (pEVin).ResultsOut of the cohort, five subjects (16%) have pEVin at 34 months. Subjects with pEVin, compared to those with ventilatory efficiency (Evef) have lower values of PETCO2 throughout exercise, showing hyperventilation. Evef subjects demonstrated selective improvements in DLCO and oxygen pulse, suggesting a recovery in cardiorespiratory function over time. In contrast, those with pEvin did not exhibit these improvements. Notably, significant correlations were found between hyperventilation (measured by PETCO2), oxygen pulse and OUES, indicating the potential prognostic value of OUES and Evin in post-COVID follow-ups.ConclusionsThe study highlights the clinical importance of long-term follow-up for post-COVID patients, as a significant group exhibit persistent EVin, which correlates with altered and potentially unfavorable cardiovascular responses to exercise. These findings advocate for the continued investigation into the long-term health impacts of COVID-19, especially regarding persistent ventilatory inefficiencies and their implications on patient health outcomes.

Prognostic Value of Body Surface Area-Adjusted Oxygen Uptake Efficiency Slope in Heart Failure Patients.

COVID-19 has been associated with a higher risk of developing heart failure (HF). Among the parameters derived from cardiopulmonary exercise testing (CPET), oxygen uptake efficiency slope (OUES) has become one of the most important parameters for predicting the prognosis of HF patients. However, the clinical utilization of OUES is limited owing to its variation with patient height and weight. This study aimed to evaluate the prognostic value of body surface area-adjusted OUES (OUES/BSA) in adults with HF. Thirty-six HF patients (mean age, 57 ± 12 years; 30 men) undergoing CPET between July 2019 and May 2020 who were followed up for 12 months were enrolled. The endpoints were major cardiovascular (CV) events, including hospitalization due to acute decompensated HF, left ventricular assist device implantation, heart transplantation, and cardiovascular-related death. We analyzed the correlations between clinical/CPET variables and major CV events. Among the analyzed CPET variables, OUES/BSA had better correlation with maximal oxygen uptake (VO2max) than other variables. In univariate Cox proportional analysis, OUES/BSA and peak VO2 were both significant independent prognostic factors. The cutoff value of OUES/BSA was 595 ml/min/m2 with an area under the curve of 0.929. The patients with OUES/BSA < 595 ml/min/m2 had a lower CV event-free survival rate at 12 months of follow-up compared with the other group (33.3% and 100%, respectively; log-rank test, p < 0.001). BSA-adjusted OUES is an effective independent predictor for prognosis in HF patients and can be an alternative to peak VO2 for risk stratification in HF patients, regardless of exercise intensity. However, further large-scale studies are required to validate our findings.

Usefulness of oxygen uptake efficiency slope in a 6min walk test in chronic heart failure.

Frailty is an obstacle to performing cardiopulmonary exercise test (CPET) in patients with chronic heart failure (CHF). We evaluated the usefulness of oxygen uptake efficiency slope (OUES) using a 6min walk test (6MWT) with portable gas analysis compared with CPET-derived parameters in patients with CHF. Patients with CHF who underwent both the 6MWT with portable gas analysis and CPET between December 2016 and May 2020 were retrospectively investigated. The 6MWT-derived and echocardiographic parameters were compared with the OUES and peak oxygen consumption (VO2) from the CPET. Forty patients were analysed; 50% were male with a mean age of 55.45±14.70years. Twenty-six patients (65%) had New York Heart Association Functional Classification II or III dyspnoea. Twenty-five patients (62.5%) had heart failure (HF) with preserved ejection fraction (EF) (left ventricular EF>50%), and nine patients (22.5%) had HF with reduced EF (EF<40%). During the 6MWT, the peak VO2 was 14.97±3.80mL/kg/min, which was only 74% of the peak VO2 in the CPET, 20.18±5.64mL/kg/min. The OUES in the 6MWT was lower than that in the CPET (1528.87±579.01 in the 6MWT vs. 1638.69±601.31 in the CPET). The 6min walk distance (6MWD) and OUES in the 6MWT were positively correlated with the OUES in the CPET (6MWD, r=0.434, P=0.005; OUES, r=0.729, P<0.001). The OUES in the 6MWT showed the strongest correlation with the OUES in the CPET. When we divided patients into two groups according to peak VO2 in the CPET, the correlation between OUES values of the 6MWT and that of the CPET was consistently confirmed (peak VO2≥20mL/kg/min group, r=0.661, P=0.001; peak VO2<20mL/kg/min group, r=0.526, P=0.021). In addition, the 6MWD, OUES, and peak VO2 in the 6MWT were associated with peak VO2 in the CPET (6MWD, r=0.627, P<0.001; OUES, r=0.452, P=0.003; and peak VO2, r=0.492, P=0.001). In frail patients with CHF who have difficulty performing maximal exercises, the OUES through the 6MWT may be applied instead of the OUES and peak VO2 from the CPET.

Effects of Exercise Training Response on Quality of Life and Cardiovascular Risk Factor Profiles in People With Coronary Artery Disease: Insights From the HIIT or MISS UK Trial

ObjectiveTo compare the characteristics of responders and nonresponders to 8 weeks of exercise training to determine differences in key cardiovascular disease outcomes in people with coronary artery disease (CAD). DesignSecondary analysis of data from the HIIT or MISS UK trial. SettingSix outpatient National Health Service cardiac rehabilitation (CR) centers in the UK. In people with CAD attending CR, the HIIT or MISS UK trial reported that short-term, low-volume, high-intensity interval training (HIIT) was more effective than moderate-intensity steady state (MISS) exercise training for improving peak oxygen uptake (V̇o2peak). Participants382 participants with CAD (N=382) (mean age: 58.8±9.6y; mean body mass index: 29.0±4.3 kg/m2). Main Outcome MeasuresWe identified responders and nonresponders based on a meaningful change in V̇o2peak, using 2 established methods. Key clinical, quality of life (QoL), and cardiopulmonary exercise test (CPET)–derived outcomes were compared between groups. ResultsResponders were more likely to be younger (P<.05), and demonstrate greater improvement in CPET-related outcomes, for example, oxygen uptake efficiency slope, ventilatory efficiency, and peak power output (all comparisons, P<.001). Responders were more likely to observe improvements in QoL (EQ-5D-5L; mean Δ 13.6 vs mean Δ 9.4; P=.045), and high-density lipoprotein cholesterol (HDL-c) (mean Δ 0.09 mmol/L vs mean Δ 0.04 mmol/L; P=.004), compared to nonresponders. ConclusionsIn people with CAD attending CR, responders to exercise training were more likely to be younger and demonstrate greater improvements in health-related QoL and HDL-c.

Determinants of V̇+O2peak Changes After Aerobic Training in Coronary Heart Disease Patients.

This study aimed to highlight the ventilatory and circulatory determinants of changes in ˙VO2peak after exercise-based cardiac rehabilitation (ECR) in patients with coronary heart disease (CHD). Eighty-two CHD patients performed, before and after a 3-month ECR, a cardiopulmonary exercise testing (CPET) on a bike with gas exchanges measurements (˙VO2peak, minute ventilation, i. e., ˙VE), and cardiac output (Q˙c). The arteriovenous difference in O2 (C(a-v¯)O2) and the alveolar capillary gradient in O2 (PAi-aO2) were calculated using Fick's laws. Oxygen uptake efficiency slope (OUES) was calculated. A 5.0% cut off was applied for differentiating non- (NR: ˙VO2<0.0%), low (LR: 0.0≤ ∆˙VO2<5.0%), moderate (MR: 5.0≤∆˙VO2 < 10.0%), and high responders (HR: ∆˙VO2≥10.0%) to ECR. A total of 44% of patients were HR (n=36), 20% MR (n=16), 23% LR (n=19), and 13% NR (n=11). For HR, the ˙VO2peak increase (p<0.01) was associated with increases in ˙VE (+12.8±13.0 L/min, p<0.01), (+1.0±0.9 L/min, p<0.01), and C(a-v¯)O2 (+2.3±2.5 mLO2/100 mL, p<0.01). MR patients were characterized by+6.7±19.7 L/min increase in ˙VE (p=0.04) and+0.7±1.0 L/min of Q˙c (p<0.01). ECR induced decreases in ˙VE (p=0.04) and C(a-v¯)O2 (p<0.01) and a Q˙c increase in LR and NR patients (p<0.01). Peripheral and ventilatory responses more than central adaptations could be responsible for the ˙VO2peak change with ECR in CHD patients.

Predischarge oxygen uptake efficiency slope has short and long-term value in the prognosis of patients after acute myocardial infarction.

Patients who survive an acute myocardial infarction (AMI) have a higher risk of having a major cardiovascular event (MACE). Cardiopulmonary exercise testing (CPET) could develop prognostic stratification and prescribing exercise prescription. Patients after AMI frequently terminate CPET early with submaximal testing results. We aimed to look at the characteristics of patients' predischarge CPET variables after AMI intervention and find potential CPET variables with prognostic value. Between July 2012 and August 2017, we recruited patients who survived first AMI after primary percutaneous coronary intervention and received predischarge CPET retrospectively in a tertiary medical center of Taiwan. Patients were followed-up on a MACE or administrative censoring occurred (up to 5 years). To identify significant predictors of a MACE, a Cox regression model was used. One hundred thirteen patients (103 men and 10 women) were studied, with an average age of 58.32 ± 12.49. MACE over 3 months, 2-years, and 5-years was 17.70%, 53.10%, and 62.83%, respectively. The oxygen uptake efficiency slope during the whole during of CPET (OUES 100) divided by body surface area (OUES 100/BSA) was found to be a significant event predictor for MACE at 3-month, 2- and 5-years. Cox regression analysis revealed that those with OUES 100/BSA <0.722 ( p = 0.004), OUES 100/BSA <0.859 ( p = 0.002), and OUES 100/BSA <0.829 ( p = 0.002) had a 7.14-fold, 3.47-fold, and 2.72-fold increased risk of 3-month, 2-year, and 5-year MACE, respectively. It is critical to identify a submaximal predictor during CPET for patients who survive AMI. Our findings suggested that OUES could be a significant prognostic indicator in patients after first AMI in both the short and long term.

Cardiopulmonary Exercise Testing after Surgical Repair of Tetralogy of Fallot-Does Modality Matter?

Despite a successful repair of tetralogy of Fallot (rToF) in childhood, residual lesions are common and can contribute to impaired exercise capacity. Although both cycle ergometer and treadmill protocols are often used interchangeably these approaches have not been directly compared. In this study we examined cardiopulmonary exercise test (CPET) measurements in rToF. Inclusion criteria were clinically stable rToF patients able to perform a cardiac magnetic resonance imaging (CMR) and two CPET studies, one on the treadmill (incremental Bruce protocol) and one on the cycle ergometer (ramped protocol), within 12 months. Demographic, surgical and clinical data; functional class; QRS duration; CMR measures; CPET data and international physical activity questionnaire (IPAQ) scores of patients were collected. Fifty-seven patients were enrolled (53% male, 20.5 ± 7.8 years at CPET). CMR measurements included a right ventricle (RV) end-diastolic volume index of 119 ± 22 mL/m2, a RV ejection fraction (EF) of 55 ± 6% and a left ventricular (LV) EF of 56 ± 5%. Peak oxygen consumption (VO2)/Kg (25.5 ± 5.5 vs. 31.7 ± 6.9; p < 0.0001), VO2 at anaerobic threshold (AT) (15.3 ± 3.9 vs. 22.0 ± 4.5; p < 0.0001), peak O2 pulse (10.6 ± 3.0 vs. 12.1± 3.4; p = 0.0061) and oxygen uptake efficiency slope (OUES) (1932.2 ± 623.6 vs. 2292.0 ± 639.4; p < 0.001) were significantly lower on the cycle ergometer compared with the treadmill, differently from ventilatory efficiency (VE/VCO2) max which was significantly higher on the cycle ergometer (32.2 ± 4.5 vs. 30.4 ± 5.4; p < 0.001). Only the VE/VCO2 slope at the respiratory compensation point (RCP) was similar between the two methodologies (p = 0.150). The majority of CPET measurements differed according to the modality of testing, with the exception being the VE/VCO2 slope at RCP. Our data suggest that CPET parameters should be interpreted according to test type; however, these findings should be validated in larger populations and in a variety of institutions.

Mechanisms underlying exercise intolerance in long COVID: An accumulation of multisystem dysfunction.

The pathogenesis of exercise intolerance and persistent fatigue which can follow an infection with the SARS-CoV-2 virus ("long COVID") is not fully understood. Cases were recruited from a long COVID clinic (N = 32; 44 ± 12 years; 10 (31%) men), and age-/sex-matched healthy controls (HC) (N = 19; 40 ± 13 years; 6 (32%) men) from University College London staff and students. We assessed exercise performance, lung and cardiac function, vascular health, skeletal muscle oxidative capacity, and autonomic nervous system (ANS) function. Key outcome measures for each physiological system were compared between groups using potential outcome means (95% confidence intervals) adjusted for potential confounders. Long COVID participant outcomes were compared to normative values. When compared to HC, cases exhibited reduced oxygen uptake efficiency slope (1847 (1679, 2016) vs. 2176 (1978, 2373) mL/min, p = 0.002) and anaerobic threshold (13.2 (12.2, 14.3) vs. 15.6 (14.4, 17.2) mL/kg/min, p < 0.001), and lower oxidative capacity, measured using near infrared spectroscopy (τ: 38.7 (31.9, 45.6) vs. 24.6 (19.1, 30.1) s, p = 0.001). In cases, ANS measures fell below normal limits in 39%. Long COVID is associated with reduced measures of exercise performance and skeletal muscle oxidative capacity in the absence of evidence of microvascular dysfunction, suggesting mitochondrial pathology. There was evidence of attendant ANS dysregulation in a significant proportion. These multisystem factors might contribute to impaired exercise tolerance in long COVID sufferers.

Below or all the way to the peak? Oxygen uptake efficiency slope as the index of cardiorespiratory response to exercise-the NOODLE study.

Background: The ratio of oxygen uptake (VO2) to minute ventilation (VE) is described as the oxygen uptake efficiency slope (OUES). OUES has been suggested as a valuable submaximal cardiorespiratory index; however, its characteristics in endurance athletes remain unknown. In this study, we a) investigated OUES between different time intervals, b) assessed their prediction power for VO2peak, and c) derived new prediction equations for OUES tailored for well-trained individuals. Materials and Methods: A total of 77 male (age = 21.4 ± 4.8yrs; BMI = 22.1 ± 1.6kg·m-2; peak oxygen uptake = 4.40 ± 0.64L·min-1) and 63 female individuals (age = 23.4 ± 4.3yrs; BMI = 23.1 ± 1.6kg·m-2; peak oxygen uptake = 3.21 ± 0.48L·min-1) underwent the cycling cardiopulmonary exercise test. OUES was measured at 75%, 90%, and 100% of exercise duration. Prediction power and new models were derived with the multiple linear regression method. Results: In male subjects, OUES [mL·min-1/L·min-1] from 75% = 4.53 ± 0.90, from 90% = 4.52 ± 0.91, and from 100% = 4.41 ± 0.87. In female subjects, OUES [mL·min-1/L·min-1] from 75% = 3.50 ± 0.65, from 90% = 3.49 ± 0.62, and from 100% = 3.41 ± 0.58. OUES did not differ between time intervals in male (p = 0.65) and female individuals (p = 0.69). OUES strongly predicts peak VO2 independently from the measuring interval (β = 0.71-0.80; R 2 = 0.50-0.63). The prediction model designed for elite athletes was OUES [mL·min-1/L·min-1] = -1.54 + 2.99; BSA [m2]-0.0014; (age [in years]; sex [1 = male, 2 = female]) (R 2 = 0.36). Conclusion: OUES enables an accurate prediction of peak cardiorespiratory fitness in elite endurance athletes. OUES is a feasible alternative to maximal exercise testing. A new prediction equation should be used for highly trained individuals. Physicians should understand OUES physiology to properly assess the cardiorespiratory response to exercise in athletic cohorts.