Oxygen Uptake Efficiency Slope Values Research Articles

Cardiorespiratory fitness mitigates brain atrophy and cognitive decline in preclinical Alzheimer’s disease

AbstractBackgroundCardiorespiratory fitness (CRF) may be a mitigating factor for Alzheimer’s Disease (AD) progression. The purpose of this study was to examine the longitudinal associations of CRF with brain atrophy and cognitive function in a late‐middle‐aged cohort of adults at risk for AD.MethodOne hundred and ten adults (mean age = 64.2 ± 5.7 years, 65% female) from the Wisconsin Registry for Alzheimer’s Prevention (WRAP) completed a baseline graded treadmill exercise test, two brain MRI scans (over 4.67 ± 1.17 years) and neurocognitive assessments (2.18 ± .78 neurocognitive tests over 3.26 ± 1.02 years) as part of their WRAP study involvement. The oxygen uptake efficiency slope (OUES) was calculated for each participant and served as the CRF measure. Total gray matter and hippocampal volumes and the preclinical Alzheimer’s cognitive composite (PACC) score were the primary outcome measures. Linear mixed effects models examined the longitudinal associations adjusted for covariates. The CRF x age (i.e., time) interaction was centered and was the term of interest as it would indicate whether longitudinal decline in volumetrics or cognition differed as a function of CRF.ResultBaseline OUES values were 1.16 ± 0.28. Total gray matter and hippocampal volume declined at a rate of ‐0.73 ± 0.90% and ‐0.16 ± 1.30% per year, and cognitive trajectories decline ‐.047 points (standardized score) per year. The CRF × age interaction was significant for total gray matter volume (β=.26 SE .11; p=.020; Figure 1) and PACC score (β=.07 SE .03; p=.049; Figure 2), but not hippocampal volume (β=.002 SE .002; p=.347). These findings were most pronounced among APOE‐e4 carriers (p<.05).ConclusionCRF may be a modifiable physiological attribute to target during the preclinical stage of AD in effort to delay disease progression.

Oxygen Uptake Efficiency Slope is Strongly Correlated to VO2peak Long-Term After Arterial Switch Operation

After the arterial switch operation (ASO) for transposition of the great arteries (TGA), many patients have an impaired exercise tolerance. Exercise tolerance is determined with cardiopulmonary exercise testing by peak oxygen uptake (VO2peak). Unlike VO2peak, the oxygen uptake efficiency slope (OUES) does not require a maximal effort for interpretation. The value of OUES has not been assessed in a large group of patients after ASO. The purpose of this study was to determine OUES and VO2peak, evaluate its interrelationship and assess whether exercise tolerance is related to ventricular function after ASO. A cardiopulmonary exercise testing, assessment of physical activity score and transthoracic echocardiography (fractional shortening and left/right ventricular global longitudinal peak strain) were performed to 48 patients after ASO. Median age at follow-up after ASO was 16.0 (IQR 13.0–18.0) years. Shortening fraction was normal (36 ± 6%). Left and right global longitudinal peak strain were reduced: 15.1 ± 2.4% and 19.5 ± 4.5%. This group of patients showed lower values for all cardiopulmonary exercise testing parameters compared to the reference values: mean VO2peak% 75% (95% CI 72–77) and mean OUES% 82(95% CI 77–87); without significant differences between subtypes of TGA. A strong-to-excellent correlation between the VO2peak and OUES was found (absolute values: R = 0.90, p < 0.001; normalized values: R = 0.79, p < 0.001). No correlation was found between cardiopulmonary exercise testing results and left ventricle function parameters. In conclusion, OUES and VO2peak were lower in patients after ASO compared to reference values but are strongly correlated, making OUES a valuable tool to use in this patient group when maximal effort is not achievable.

Oxygen uptake efficiency slope during exercise in adults with Down syndrome

Persons with Down syndrome (DS) have low aerobic exercise capacity. The present authors sought to compare the oxygen uptake efficiency slope (OUES) between adults with and without DS performing graded exercise testing (GXT) and to investigate its relationship with peak oxygen uptake (VO2peak ) in both groups of participants. Twenty-three participants with DS and 24 non-disabled controls performed GXT with VO2 measurements. OUES was calculated from data of the first 75%, 90% and 100% GXT time. Multiple linear regression analyses were computed to explore associations between the independent (OUES and DS) and the dependent variables (VO2peak ). VO2peak , GXT time and OUES were lower in participants with DS (p<.05). OUES and DS explained 69.3% of the variance in VO2peak . Our findings show that OUES values are lower in persons with DS. Additionally, it was shown that OUES has predictive value for VO2peak estimations in DS.

WS21.8 Validity of the Oxygen Uptake Efficiency Slope (OUES) as a parameter of maximal and submaximal exercise testing in children with mild CF

Objective Maximal oxygen consumption (VO2max) is considered as gold standard of maximal exercise testing. The Oxygen Uptake Efficiency Slope is stated as a valuable parameter of submaximal exercise. We sought to investigate the validity of OUES at different levels of exercise duration in children with mild CF. Methods 20 CF-patients with mild respiratory limitation (9 boys, age 12.45 yrs, FEV1 91.8% and BSA 1.44 m 2 ) were analysed. OUES was calculated at three levels of exercise intensity: at 50%, 75% and 100% (OUES50, OUES75 and OUES100). OUES/BSA was correlated with VO2max, VO2max/kg, maximal minute ventilation at exercise (VE), VE/VCO2, respiratory exchange ratio (RER). Results OUES50/BSA (1254±205), OUES75/BSA (1332±234) and OUES100/BSA (1348±233) all correlated strongly with VO2max (1704±518 ml/min) (correlation coefficient 0.69, 0.69, 0.66 respectively, P=0.001) and VO2max/kg (36.2±7 ml/kg/min) (P Conclusion The strong correlation between OUES values at 50%, 75% or 100% of activity and VO2max proves that OUES values are valid submaximal parameters in children with mild CF. Due to the fact that only OUES75 is equal to OUES100, it is important that the patients can perform at least 75% of the predicted maximal exercise to be reliable. OUES values have no correlation with maximal minute ventilation during maximal exercise.

Causes of nonlinearity of the oxygen uptake efficiency slope: a prospective study in patients with chronic heart failure

The oxygen uptake efficiency slope (OUES) is an exercise parameter with strong prognostic value in the heart failure population. Yet, the optimal determination method of OUES remains unclear. The purpose of the present study was to investigate the influence of the ventilatory anaerobic threshold (VAT) and occurrence of a plateau in oxygen uptake (VO2) on determination of OUES from submaximal exercise data in patients with chronic heart failure (CHF). Ninety-eight CHF patients (New York Heart Association class II-III) were included. All patients performed a symptom-limited exercise test with gas exchange analysis on a cycle ergometer. VAT was determined by the V-slope method and OUES was derived via least-squares linear regression using 100% (OUES100), 90% (OUES90), and 75% (OUES75) of exercise duration, and, in addition, by using only the first 50% of data points preceding VAT (OUES½VAT), all data preceding VAT (OUESVAT), and only data following VAT (OUESpostVAT). Whereas OUESVAT (1720 ± 430 ml/min/log(l/min)), OUES75 (1811 ± 476 ml/min/log(l/min)), and OUESpostVAT (1742 ± 564 ml/min/log(l/min)) were not significantly different from OUES100 (1767 ± 542 ml/min/log(l/min)), OUES½VAT (1500 ± 314 ml/min/log(l/min)) was significantly lower than all other values (p < 0.01). When a VO2 plateau was present, OUES100 was lower than OUES90 (p < 0.05). The study results indicate that OUES values should be interpreted with caution when CHF patients do not reach the ventilatory anaerobic threshold or when a VO2 plateau is present.

Validity of reporting oxygen uptake efficiency slope from submaximal exercise using respiratory exchange ratio as secondary criterion.

Background. Oxygen uptake efficiency slope (OUES) is a reproducible, objective marker of cardiopulmonary function. OUES is reported as being relatively independent of exercise intensity. Practical guidance and criteria for reporting OUES from submaximal tests has not been established. Objective. Evaluate the use of respiratory exchange ratio (RER) as a secondary criterion for reporting OUES. Design. 100 healthy volunteers (53 women) completed a ramped treadmill protocol to exhaustive exercise. OUES was calculated from data truncated to RER levels from 0.85 to 1.2 and compared to values generated from full test data. Results. Mean (sd) OUES from full test data and data truncated to RER 1.0 and RER 0.9 was 2814 (718), 2895 (730), and 2810 (789) mL/min per 10-fold increase in VE, respectively. Full test OUES was highly correlated with OUES from RER 1.0 (r = 0.9) and moderately correlated with OUES from RER 0.9 (r = 0.79). Conclusion. OUES values peaked in association with an RER level of 1.0. Sub-maximal OUES values are not independent of exercise intensity. There is a significant increase in OUES value as exercise moves from low to moderate intensity. RER can be used as a secondary criterion to define this transition.

The Oxygen Uptake Efficiency Slope

To summarize what is currently known about the oxygen uptake efficiency slope (OUES) as an objective and independent submaximal measure of cardiorespiratory fitness in health and disease. A literature search was performed within the following electronic databases--PubMed, Cochrane Library, Embase, Web of Science, CINAHL, PsycINFO, Scopus, and MEDLINE--using the search terms "OUES," "oxygen uptake efficiency slope," and "ventilatory efficiency." The search identified 51 articles. Selection, evaluation, and data extraction were accomplished independently by 2 authors. Twenty-four studies satisfied all inclusion criteria: 17 cross-sectional studies and 7 intervention studies. The results indicated that the OUES is relatively independent of exercise intensity, correlates highly with other exercise parameters, appears to have discriminative value, and is sensitive to the effects of physical training in patients with cardiac disease. Oxygen uptake efficiency slope values are considerably influenced by anthropometric variables and show large interindividual variation. Oxygen uptake efficiency slope is an independent and reproducible measure of cardiorespiratory function that does not require maximal exercise. It greatly reduces test variability because of motivational and subjective factors and is reliable and easily determinable in all subjects. Although OUES appears not interchangeable with maximal parameters of cardiopulmonary function, it seems to be a useful submaximal alternative in subjects unable to perform maximal exercise.

EXERCISE PERFORMANCE AND VENTILATORY EFFICIENCY IN PATIENTS WITH MILD AND MODERATE LIVER CIRRHOSIS

1. The impact of ventilatory efficiency on reduced exercise capacity and recovery oxygen kinetics has not been addressed in cirrhotic patients. The aim of the present study was to investigate exercise performance and ventilatory efficiency in patients with mild and moderate liver cirrhosis (LC). 2. Nineteen male non-hypoxic patients with LC (age 51.3 +/- 9.1 years; body mass index (BMI) 25.6 +/- 3.6 kg/m(2)) classified by the Child-Pugh score as class A (n = 7) and class B (n = 12) and 19 age- and BMI-matched controls participated in the study. Subjects undertook maximal incremental exercise testing on a treadmill using the Bruce protocol. 3. Patients with LC showed a reduced diffusion capacity (D(L,CO)%) compared with controls (74.6 +/- 15.2 vs 95.6 +/- 12.9%, respectively; P < 0.001), but a comparable volume standardized diffusion coefficient (1.33 +/- 0.22 vs 1.45 +/- 0.18 mmol/min per kPa per L, respectively; P = 0.74). Patients with LC had a significantly lower exercise capacity compared with controls (VO(2 max) 23.8 +/- 3.8 vs 30.6 +/- 4.4 mL/min per kg, respectively; P < 0.001). Recovery oxygen kinetics were also impaired in LC patients compared with controls (104.6 +/- 19.3 vs 84.4 +/- 22.7 s, respectively; P = 0.012). The chronotropic index was significantly lower in the LC group compared with controls (0.67 +/- 0.19 vs 0.82 +/- 0.17, respectively; P = 0.030) and LC patients showed higher ventilatory equivalents (30.4 +/- 3.8 vs 26.3 +/- 2.3, respectively; P < 0.001) and lower oxygen uptake efficiency slope values (2187 +/- 445 vs 2745 +/- 473 mL/min per log(10)L, respectively; P < 0.001) compared with controls, which is indicative of decreased ventilatory efficiency. Patients with LC also had a higher standardized maximal exercise perception score (SMEPS) compared with controls (0.62 +/- 0.18 vs 0.46 +/- 0.15, respectively; P = 0.011). Moderate negative correlations were found between Child-Pugh score and VO(2 max)% (r = -0.496; P = 0.031). 4. In conclusion, patients with mild and moderate LC have reduced exercise capacity, which correlates with Child-Pugh score, as well as reduced chronotropic index and prolonged recovery oxygen uptake kinetics. The results suggest worsened ventilatory efficiency during exercise and cardiopulmonary reasons for the higher SMEPS in these patients.

Oxygen uptake efficiency slope: an index of exercise performance and cardiopulmonary reserve requiring only submaximal exercise

OBJECTIVESWe sought to evaluate, in adults, the efficacy of the Oxygen Uptake Efficiency Slope (OUES), an index of cardiopulmonary functional reserve that can be based upon a submaximal exercise effort.BACKGROUNDMaximal oxygen uptake (O2 max), the most reliable measure of exercise capacity, is seldom attained in standard exercise testing. The OUES, which relates oxygen uptake to total ventilation during exercise, was proposed by Baba and coworkers (7) in a study of pediatric cardiac patients. They felt this submaximal index of cardiopulmonary reserve might be more practical than O2 max and more appropriate than the commonly used peak oxygen consumption (O2 peak).METHODSTreadmill exercise tests with simultaneous respiratory gas measurement were performed in 998 older subjects free of clinically recognized cardiovascular disease and 12 male patients with congestive heart failure. During incremental exercise, oxygen uptake was plotted against the logarithm of total ventilation, and the OUES was determined.RESULTSThe OUES, when calculated only from the first 75% of the exercise test, differed by 1.9% from the OUES calculated from 100% of exercise time in subjects with a peak respiratory exchange rate ≥1.10. On serial tests the OUES was less variable than exercise duration or O2 peak. It correlated strongly with O2 max, with forced expiratory volume in 1 s and negatively with a history of current smoking. The OUES declined linearly with age in both women and men. A small sample of patients with congestive heart failure had OUES values much lower than those of older subjects without cardiovascular disease.CONCLUSIONSThe OUES is an objective, reproducible measure of cardiopulmonary reserve that does not require a maximal exercise effort. It integrates cardiovascular, musculoskeletal and respiratory function into a single index that is largely influenced by pulmonary dead space ventilation and exercise-induced lactic acidosis.