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

OBJECTIVES: We 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. BACKGROUND: Maximal oxygen uptake (VO2,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 VO2max and more appropriate than the commonly used peak oxygen consumption (VO2 peak). METHODS: Treadmill 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. RESULTS: The 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 > or =1.10. On serial tests the OUES was less variable than exercise duration or VO2 peak. It correlated strongly with VO2max, 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. CONCLUSIONS: The 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.     

Association of blood pressure and fitness with levels of atherosclerotic risk markers pre-exercise and post-exercise

BACKGROUND: Physical fitness may attenuate the increased atherosclerotic risk in patients with systemic hypertension. We investigated the association of screening blood pressure (BP) and cardiorespiratory fitness with baseline levels and exercise-induced changes in levels of soluble atherosclerotic risk markers. METHODS: Twenty-six otherwise healthy and unmedicated subjects with elevated BP (systolic BP and/or diastolic BP > or =130/85 mm Hg) and 40 subjects with normal BP underwent 20-min treadmill exercise at 65% to 70% of predetermined peak oxygen consumption (VO(2peak)). Interleukin (IL)-6, soluble intercellular adhesion molecule (sICAM)-1, von Willebrand factor (VWF) antigen, and plasminogen activator inhibitor (PAI)-1 antigen were measured at baseline (ie, pre-exercise), early postexercise, and late postexercise (ie, 25 min after exercise). RESULTS: At baseline, higher screening mean arterial BP (MAP) independently predicted higher sICAM-1 levels (P = .031), and lower VO(2peak) independently predicted higher IL-6 (P = .016) and PAI-1 (P < .001) levels. Early and late postexercise lower VO(2peak) was associated with higher mean PAI-1 (P < or = .072) and IL-6 (P < or = .026) levels, and higher screening MAP was associated with higher mean sICAM-1 levels (P < or = .035). Higher VO(2peak) was associated with a greater PAI-1 increase from baseline to early postexercise in subjects with elevated BP (P = .045) but not in those with normal BP. CONCLUSIONS: Circulating levels of some atherosclerotic risk markers at baseline and with exercise were higher with elevated BP and lower with better fitness. Greater fitness did not particularly protect subjects with elevated BP from potentially harmful responses of atherosclerotic risk markers to acute physical exercise.     

Therapeutic exercise for individuals with heart failure: special attention to older women with heart failure

BACKGROUND: A cardinal feature of heart failure (HF) is the reduced peak aerobic power (VO(2peak)) secondary to alterations in cardiovascular and musculoskeletal function.Methods and results During the last decade, a number of randomized trials have examined the role that exercise training plays in attenuating the HF-mediated decline in VO(2peak) and muscle strength. The major finding of these investigations was that aerobic or strength training was an effective intervention to increase VO(2peak), muscular strength, distance walked in 6 minutes, and quality of life without negatively altering left ventricular systolic function. Despite these benefits, a limitation of these investigations was the primary focus on males <60 years with impaired left ventricular systolic function. Thus the role that exercise training may play in attenuating the HF-mediated decline in VO(2peak) in women > or =65 years of age remains unknown. CONCLUSION: Older women with HF have a VO(2peak) that is below the minimal threshold level required for independent living. Moreover, older women with HF have greater disability then men and are less likely to be referred to an exercise rehabilitation program. Accordingly, future exercise intervention trials are required to examine the role that exercise training may play in attenuating the HF-mediated decline in cardiorespiratory and musculoskeletal fitness and disability in older women with HF.     

Longitudinal study of determinants of dependence in an elderly population

OBJECTIVES: To describe those factors, from the host of initial measures in ambulatory, independent older men and women, that were determinants of becoming dependent over an 8-year follow-up. DESIGN: Initial measures in a cohort of independent older adults were used in logistic regression to describe the determinants of becoming dependent at the 8-year follow-up. SETTING: London, Ontario. PARTICIPANTS: Three hundred seventy-three men and women aged 55 to 86. MEASUREMENTS: Initial variables included body size, presence of chronic disease, maximal oxygen uptake (VO2max), strength, flexibility, walking pace, and leisure time physical activity. RESULTS: An 8-year follow-up of 297 participants identified 43 as dependent. Logistic regression showed age, presence of disease, and VO2max (cardiorespiratory fitness) at baseline to have significant odds ratios related to the outcome of becoming dependent. Controlling for other factors, a lower VO2max increased the odds of dependence by 14% for each mL/kg.min. CONCLUSION: Lower cardiorespiratory fitness was a significant determinant of becoming dependent in an 8-year follow-up of older adults. Initiatives to encourage physical activity in older adults should emphasize exercise, such as brisk walking, to maintain or improve cardiorespiratory fitness.     

Fitness, fatigue, disease activity, and quality of life in pediatric lupus

OBJECTIVE: To measure aerobic fitness (maximum oxygen consumption [VO(2peak)]), fatigue, quality of life (QOL), and disease activity in young persons with systemic lupus erythematosus (SLE), and to determine an equation for predicting VO(2peak) from the distance walked in 6 minutes (6MW). METHODS: Fifteen young patients ages 12-19 years with SLE participated. VO(2) was measured by a graded treadmill exercise test. Submaximal exercise intensity was determined from the ventilatory anaerobic threshold. Submaximal aerobic capacity was measured using the 6MW. Patient questionnaires included measures of fatigue, QOL, and physical activity. Physician questionnaires included the Systemic Lupus Erythematosus Disease Activity Index and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. RESULTS: Compared with age-matched norms, our patients had moderate impairment in aerobic fitness, with a mean +/- SD VO(2peak) of 31.1 +/- 7.9 ml/minute/kg and a mean 6MW distance Z score of -2.4 +/- 2.3. The regression equation to predict VO(2peak) (ml/minute/kg) from 6MW was as follows: 57.1 + [0.038 x distance (meters)] + (-0.35 x maximal heart rate) (R = 0.67, P = 0.027). Ten subjects (67%) reported significant fatigue. There was no significant correlation of fatigue with fitness measures. Neither fatigue nor fitness was significantly correlated with disease activity, disease damage, or QOL measures. CONCLUSION: Young SLE patients have lower aerobic fitness than reference norms. The 6MW may be used as a marker of fitness, but it is preferable to determine VO(2) with a graded exercise test. Fatigue is a significant symptom in young SLE patients. The application of fatigue measures in young persons is exploratory. The relationship between fatigue and aerobic fitness is not clear.     

Effects of aerobic exercise training in community-based subjects aged 80 and older: a pilot study

OBJECTIVES: To assess the ability of sedentary, frail subjects aged 80 and older to train in a community-based exercise program and to evaluate clinical factors that predict improvements in peak oxygen consumption (VO2peak). DESIGN: Pretest, posttest. SETTING: Charlestown Retirement Community, Catonsville, Maryland PARTICIPANTS: Twenty-two (11 male, 11 female; mean age +/- standard deviation = 84 +/- 4.0, range 80-92) self-referred. INTERVENTION: Six months of moderate-intensity aerobic exercise training, two to three sessions/week, 20 to 30 minutes per session. Training modes included treadmill walking and/or stationary cycling. MEASUREMENTS: Baseline and follow-up maximal exercise treadmill tests (ETTs) with electrocardiogram monitoring and respiratory gas analysis. RESULTS: Six months of aerobic exercise training resulted in significant increases (mean +/- standard deviation) in ETT duration (11.9 +/- 3.3 vs 15.9 +/- 4.3 minutes; P =.01), VO2peak (1.23 +/- 0.37 vs 1.31 +/- 0.36 L/min; P =.04), and oxygen pulse (9.3 +/- 2.8 vs 10.1 +/- 3.2; P =.03). Mean heart rate was significantly lower during submaximal ETT stages 1 through 4 (P <.05), and resting systolic blood pressure decreased (146 +/- 18 vs 133 +/- 14 mmHg; P =.01) after training. Multiple regression analysis indicated that baseline VO2peak (r = 0.75, P =.002) and the total amount of time spent in exercise training (r = 0.55, P =.008) were independent predictors of the training-related improvements in VO2peak. CONCLUSION: Subjects aged 80 and older can increase aerobic capacity and reduce systolic blood pressure in a community-based exercise program of moderate intensity. The most important predictors of change in VO2peak were baseline VO2peak and the time spent in exercise training. Subjects with a lower baseline VO2peak had the greatest improvements in VO2peak after training.     

Comparison of cardiorespiratory fitness versus leisure time physical activity as predictors of coronary events in men aged < or = 65 years and > 65 years

Both high peak oxygen consumption (VO(2)) and high levels of leisure time physical activity (LTPA) are associated with a reduced risk of cardiovascular morbidity and mortality. We examined the contributions of LTPA and peak VO(2) to the risk of coronary events (CEs) in healthy younger (< or = 65 years, n = 522) and older (>65 years, n = 167) men from the Baltimore Longitudinal Study of Aging. LTPA derived from self reports of time spent in 97 activities were converted into METs-minutes/24 hours and grouped into high (> or = 6 METs), moderate- (4 to 5.9 METs), and low-intensity LTPA (<4 METs). Cardiorespiratory fitness was determined by measuring peak VO(2) during a maximal treadmill exercise test. Over a mean follow-up of 13.4 +/- 6.3 years, CEs occurred in 63 men. After accounting for coronary risk factors, proportional-hazards analyses showed a relative CE risk of 0.53 (p <0.0001) for a SD increase in peak VO(2) in younger men and 0.61 (p = 0.024) in older men, whereas total LTPA was unrelated to coronary risk in either age group. When the 3 LTPA intensity levels were substituted for total LTPA in the model, peak VO(2) remained the only predictor of events in younger men, whereas high-intensity LTPA (RR = 0.39 for tertile 3 vs tertiles 1 and 2, p = 0.016) and peak VO(2) (RR = 0.61/SD increase, p = 0.024) were of similar importance in older men. Thus, in healthy younger men, higher cardiorespiratory fitness but not LTPA predicts a reduced risk of coronary heart disease, independent of conventional risk factors. For older men, high-intensity LTPA and fitness appear to be of similar importance in reducing coronary risk.     

Exercise-induced silent myocardial ischemia and future cardiac events in healthy, sedentary, middle-aged and older men.

OBJECTIVES: Before men older than age 45 participate in vigorous exercise programs, the American Heart Association and the American College of Sports Medicine recommend they undergo a screening maximal exercise treadmill test. We examined the predictive value for subsequent cardiac events of exercise-induced silent myocardial ischemia (SI) during the exercise treadmill test in healthy, sedentary, obese, middle-aged and older men recruited for research studies. DESIGN: A cohort study with 7 years of follow-up. SETTING: Out-patient research at a tertiary hospital. PARTICIPANTS: 170 healthy, sedentary, obese, middle-aged and older (ages 45-79 years) men with no prior history of coronary artery disease (CAD) recruited for research studies. MEASUREMENTS: Cardiac risk factors, exercise-induced SI (ST segment depression on the electrocardiogram during a maximal exercise treadmill test), maximal aerobic capacity (VO2max), and 7- year follow-up data on incident CAD. RESULTS: At baseline, 37 of the men (22%) had exercise-induced SI on their treadmill tests. Seven-year follow-up data was obtained in 97% of the patients. In the interim, 31 men had cardiac endpoints (sudden cardiac death, myocardial infarction, angioplasty, coronary artery bypass graft surgery, angina), and four had noncardiac deaths. Seventeen of the 37 men (46%) with exercise-induced SI on their baseline exercise tests had cardiac endpoints compared with 14 of 133 (11%) men with normal exercise tests (P < .001). Compared with the men with no cardiac endpoints, the men with subsequent cardiac endpoints were older (63 +/- 1 vs 58 +/- 1 years, mean +/- SEM, P < .001) and had a lower maximal aerobic capacity (VO2max) (24 +/- 1 vs 29 +/- 1 mL/kg/min, P < .001). In Cox proportional hazards analysis, exercise-induced SI and a low VO2max were independent predictors of subsequent cardiac endpoints. CONCLUSION: In a healthy population of obese, sedentary, middle-aged and older men, exercise-induced SI and low VO2max were predictors of incident CAD. This suggests that exercise treadmill testing is beneficial in assessing risk for future cardiac events in obese, sedentary individuals.     

Oxygen uptake efficiency slope as monitoring tool for physical training in chronic hemodialysis patients

The purpose of this study was to clarify the utility of oxygen uptake efficiency slope (OUES) as a monitoring tool, and to investigate the effects of physical training in chronic hemodialysis (HD) patients. Seventeen patients (Trained Group) received physical training 2-3 times per week for 20 weeks at the intervals between exercise tests. Patients underwent a combination training of bicycle ergometry, walking and jogging for 30 min duration. The intensity of physical training was adjusted to maintain the exercising heart rate at between 50 and 60% of the peak heart rate. Twelve patients (Control Group) lived without physical training throughout the 20 weeks. Both the Groups received the symptom limited exercise tests before and after the 20 week physical training. Minute ventilation (VE), carbon dioxide output (VCO2) and oxygen uptake (VO2) were continuously measured during the exercise tests. Oxygen uptake efficiency slope was derived from the logarithmic relation between VO2 and VE during an incremental exercise test. In the Trained Group, OUES after physical training (30.1 +/- 5.8) was significantly (P < 0.01) higher than that before physical training (25.2 +/- 2.6), while in the Control Group, OUES did not change in this study period of 20 weeks. In the Trained Group, changes in OUES correlated with those in the maximum oxygen uptake (r = 0.78, P < 0.001) and the anaerobic threshold (r = 0.61, P < 0.01). It was suggested that OUES was applicable as a monitoring tool for cardiorespiratory functional reserve during physical training in HD patients.     

Role of right-to-left atrial shunt in exercise tolerance of patients with Ebstein anomaly]

The aim of this study was to assess cardiorespiratory tolerance to exercise in children with non-operated, paucisymptomatic and untreated froms of Ebstein's anomaly. The authors undertook a prospective study in 11 children, mean age 9.6 years, who had lung function tests, cardiorespiratory exercise stress tests (bicycle ergometry N = 8, treadmill N = 3) and contrast echocardiography. All parameters of spirometry were normal. Contrast echocardiography showed a right-to-left interatrial shunt in 7 children (group 1) whereas the remaining 4 children had no shunt (group 2). The resting oxygen saturation was 97.4 +/- 2%, with no difference between the two groups. On the other hand, oxygen saturation at peak VO2 (VO2 max) was 90 +/- 9.5%, significantly lower in group 1 than in group 2 (85.7 +/- 2.2% vs 98.2 +/- 1.2%; p = 0.03). In group 1, the VO2 max was correlated to oxygen saturation (r = 0.98; p < 0.001, N = 6). The oxygen desaturation was correlated with presence of a right-to-left interatrial shunt (p = 0.01). The reduced exercise tolerance of non-operated, paucisymptomatic children with Ebstein's anomaly is due to a right-to-left interatrial shunt. In patients with poor exercise tolerance, contrast echocardiography is advised for the detection of these atrial shunts.     

Independent relationship between heart rate recovery and C-reactive protein in older adults

OBJECTIVES: To examine the independent effect of parasympathetic tone (PST), assessed here according to heart rate recovery (HRR) after exercise, on circulating levels of C-reactive protein (CRP) in 132 elderly participants. DESIGN: Cross-sectional analysis using baseline data from an ongoing trial assessing the effects of exercise on immune function. SETTING: Champaign/Urbana, Illinois, vicinity. PARTICIPANTS: Community-living older adults who had been sedentary for 6 months or longer. Major exclusion criteria were current use of medications that could interfere with immunity, severe arthritis, history of cancer or inflammatory disease, recent illness or vaccination, and smoking. MEASUREMENTS: Participants were assessed for serum CRP (using enzyme-linked immunosorbent assay), cardiorespiratory fitness (peak oxygen intake (VO(2))), HRR, percentage body fat (using dual-energy x-ray absorptiometry), physical activity level (according to the Physical Activity Scale for the Elderly (PASE)), fasting plasma glucose, kidney function (creatinine level), and perceived stress. RESULTS: Mean CRP level+/-standard deviation was 3.81+/-2.7 mg/L, placing this group in a high-risk category. After adjusting for the effects of body fat (34.6%+/-7.4%), aspirin use, VO(2) peak (19.5+/-3.9 mL oxygen/kg per minute), PASE, sex (64% women), and perceived stress, HRR was the only independent predictor of CRP (beta=-0.257, P=.003, change in coefficient of determination=0.060). CONCLUSION: HRR after exercise appears to be independently associated with lower CRP in older sedentary individuals, suggesting that the parasympathetic nervous system is involved in regulating chronic inflammation in older adults. Improvements in PST, as a result of regular physical exercise, may contribute to the antiinflammatory effects of exercise, independent of physical fitness or fatness.     

Cardiovascular and behavioral effects of aerobic exercise training in healthy older men and women

The cardiovascular and behavioral adaptations associated with a 4-month program of aerobic exercise training were examined in 101 older men and women (mean age = 67 years). Subjects were randomly assigned to an Aerobic Exercise group, a Yoga and Flexibility control group, or a Waiting List control group. Prior to and following the 4-month program, subjects underwent comprehensive physiological and psychological evaluations. Physiological measures included measurement of blood pressure, lipids, bone density, and cardiorespiratory fitness including direct measurements of peak oxygen consumption (VO2) and anaerobic threshold. Psychological measures included measures of mood, psychiatric symptoms, and neuropsychological functioning. This study demonstrated that 4 months of aerobic exercise training produced an overall 11.6% improvement in peak VO2 and a 13% increase in anaerobic threshold. In contrast, the Yoga and Waiting List control groups experienced no change in cardiorespiratory fitness. Other favorable physiological changes observed among aerobic exercise participants included lower cholesterol levels, diastolic blood pressure levels, and for subjects at risk for bone fracture, a trend toward an increase in bone mineral content. Although few significant psychological changes could be attributed to aerobic exercise training, participants in the two active treatment groups perceived themselves as improving on a number of psychological and behavioral dimensions.     

The validation of oxygen uptake efficiency slope in patients with stroke

To evaluate the real aerobic capacity is difficult due to impaired limbs function in stroke patients. Oxygen uptake efficiency slope (OUES) could represent the aerobic capacity in submaximal exercise test. Hence, we designed this observational study to investigate the application of the OUES for evaluating aerobic capacity in these patients.Thirty-seven stroke patients were classified into 2 groups according to their Brunnstrom stage of affected lower limbs. Patients underwent cardiopulmonary exercise testing to assess cardiorespiratory fitness. Minute ventilation and oxygen consumption were measured, and OUES was calculated, compared with healthy reference values, and correlated with the peak oxygen consumption. The predictive validity of submaximal OUES was derived.Study participants’ OUES (median 566.2 [IQR, 470.0-711.6]) was 60% of healthy reference values and correlated positively with the peak oxygen consumption (r = 0.835) (P < .01). The predictive validity of oxygen uptake efficiency slope at 50% of maximal exercise duration (OUES₅₀) and oxygen uptake efficiency slope at 75% of maximal exercise duration (OUES₇₅) for oxygen uptake efficiency slope at 100% of maximal exercise duration (OUES₁₀₀) was 0.877 and 0.973, respectively (P < .01). The OUES₅₀, OUES₇₅, and OUES₁₀₀ groups were not significantly different; agreement of submaximal and maximal OUES values was strong.OUES is a valuable submaximal index for evaluating cardiorespiratory fitness in stroke patients. Moderate-to-high concurrent validity of this parameter with peak oxygen consumption and the high predictive validity of OUES₅₀ and OUES₇₅ for OUES₁₀₀ suggest maximal exercise testing in stroke patients who cannot reach maximal exercise is unnecessary.     

Executive function, more than global cognition, predicts functional decline and mortality in elderly women

BACKGROUND: Functional impairment in community-dwelling older adults is common and is associated with poor outcomes. Our goal was to compare the contribution of impairment in executive function or global cognitive function to predicting functional decline and mortality. METHODS: We studied 7717 elderly women enrolled in a prospective study (mean age 73.3 years) and identified women with poor baseline executive function (score > 1 standard deviation [SD] below the mean on the Trail Making Test B (Trails B; n = 957, 12.4%), poor global cognitive function (score > 1 SD below the mean on a modified Mini-Mental State Examination [mMMSE], n = 387, 5.0%), impairment in both (n = 249, 3.2%), or no impairment (n = 6124, 79.4%). We compared level of functional difficulty (Activities of Daily Living [ADLs] and Instrumental ADLs [IADLs]) at baseline and at 6-year follow-up and survival at follow-up. We also determined if the association was independent of age, education, depression, medical comorbidities, and baseline functional ability. RESULTS: At baseline, women with Trails B impairment only or impairment on both tests reported the highest proportion of ADL and IADL dependence compared to the other groups. At the 6-year follow-up after adjusting for age, education, medical comorbidities, depression, and baseline ADL or IADL, women with only Trails B impairment were 1.3 times more likely to develop an incident ADL dependence (adjusted odds ratio [OR] = 1.34; 95% confidence interval [CI], 1.07-1.69) and 1.5 times more likely to develop a worsening of ADL dependence (adjusted OR = 1.48; 95% CI, 1.16-1.89) when compared to women with no impairment on either test. In addition, women with only Trails B impairment had a 1.5-fold increased risk of mortality (adjusted hazard ratio [HR] = 1.48; 95% CI, 1.21-1.81). In contrast, women with impairment on only mMMSE were not at increased risk to develop incident ADL or IADL dependence, a worsening of ADL or IADL dependence, or mortality. CONCLUSION: Compared to women with no impairment, women with executive function impairment had significantly worse ADL and IADL function cross-sectionally and over 6 years. Individuals with executive dysfunction also had increased risk of mortality. These results suggest that screening of executive function can help to identify women who are at risk for functional decline and decreased survival.     

The effects of exercise training on the pharmacokinetics of digoxin

BACKGROUND: Studies have shown that digoxin binds to the working muscles during an acute bout of exercise, with a concomitant decrease in serum digoxin concentration. This study investigated the effects of 16 weeks of endurance exercise training on the pharmacokinetics of digoxin in old and young adults. METHODS: Twelve subjects, aged 68.5 +/- 4.5 years, and six subjects, aged 30.3 +/- 3.8 years, completed the study. All subjects were healthy, sedentary, and taking no cardiovascular medications. After initial testing and maximum oxygen consumption (VO2max) measurements, subjects were hospitalized for 28 hours for renal function testing and digoxin clearance studies and then randomly assigned to an exercise (EG) or control (CG) group. The EG completed 16 weeks (three 1-hour bouts/week) of aerobic training at 75% to 85% of maximum capacity. The CG did not exercise. All tests were repeated at the end of the 16-week study period. RESULTS: In the older EG subjects, VO2max increased by 3.4 ml/kg/min, or approximately 16% (P = 0.0002). VO2max increased in the younger EG subjects by 1.1 ml/kg/min, but the increase was not significant (P > 0.05). There were no significant changes in body composition, renal function, or time of onset, peak concentration, or elimination phase half-life of digoxin in either the old or young exercise or control groups (P > 0.05 for all variables). CONCLUSION: Although 16 weeks of endurance exercise training improves cardiorespiratory fitness, the pharmacokinetics of digoxin are neither improved nor adversely affected in healthy old and young adults.     

The influence of body mass index on the oxygen uptake efficiency slope in patients with heart failure

There does not appear to be a relationship between peak oxygen consumption (VO(2)) and body mass index (BMI) in patients with heart failure (HF). We assessed the hypothesis that BMI and the oxygen uptake efficiency slope (OUES) would be related. Three hundred and thirty-seven HF patients (280 male/57 female, mean age: 56.5+/-14.1 years, resting left ventricular ejection fraction: 35.1+/-14.2%, BMI: 29.3+/-6.2 kg/m(2)) underwent cardiopulmonary exercise testing where peak VO(2) and the OUES (VO(2)=a log(10)VE+b, units: L/min) were determined. Pearson product moment correlation analysis revealed that the correlation between BMI and the OUES was significant (r=0.32, p<0.001). Furthermore, the OUES was prognostically significant in normal weight (optimal threshold: 1.2, hazard ratio: 3.7, 95% confidence interval: 1.4-9.9, p=0.01), overweight (optimal threshold: 1.5, hazard ratio: 3.9, 95% confidence interval: 1.3-11.1, p=0.01) and obese (optimal threshold: 1.7, hazard ratio: 4.1, 95% confidence interval: 1.4-12.8, p=0.01) subgroups. The OUES appears to improve with body weight in patients with HF. Furthermore, the OUES appears to be a significant prognostic marker irrespective of BMI although the optimal threshold value may differ according to body weight.     

Gas exchange during exercise in diabetic children.

The purpose of this study was to evaluate the cardiorespiratory and metabolic response to exercise in 33 children, aged 9 to 15 years, affected by type I diabetes mellitus, in comparison with 47 age-, sex-, weight-, and height-matched healthy children. All diabetic children were on a mixed split-dose insulin regimen, consisting of both regular and long-acting insulin in the morning and evening. The last insulin injection was administered on average 6 hours before the test. The mean duration of diabetes mellitus was 5.0 +/- 3.1 years. The metabolic control was evaluated on the basis of HbA1 levels (mean, 8.9 +/- 1.8%). Pulmonary function tests and progressive exercise tests on the treadmill were performed. Gas exchange, ventilation, and heart rate (HR) were monitored during the tests. The O2 pulse (VO2/HR) was calculated. There was no difference in the baseline oxygen uptake (VO2) between the diabetic children and the control group. VO2 peak was significantly lower (P less than 0.01) in the diabetic adolescents (41.2 +/- 5.9 mL/min/kg) compared to control subjects (46.3 +/- 9.6 mL/min/kg) and it was achieved at an earlier (P less than 0.01) time of run (7.5 +/- 1.8 vs. 9.1 +/- 2.8 min). Anaerobic threshold and minute ventilation were similar in the two groups. The O2 pulse throughout the test was significantly lower (ANOVA, P less than 0.001) in the diabetic group compared to the controls. No differences were found in resting and post-exercise spirometric values. In conclusion, our study shows that well-controlled diabetic adolescents have a reduced working capacity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Submaximal exercise gas exchange is an important prognostic tool to predict adverse outcomes in heart failure

AIMS: Traditionally, VO(2peak) has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (V(E)/VCO(2)), end-tidal CO(2) (P(ET)CO(2)), oxygen uptake efficiency slope (OUES), and circulatory power [ systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients. Method and results One hundred and thirty-two consecutive heart failure patients (mean age 56 ± 12 years, ejection fraction 29 ± 11%) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0-114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included V(E)/VCO(2) slope and ratio, P(ET)CO(2), OUES, and circulatory power (P ≤ 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (V(E) and circulatory power) and at an RER of 0.9 (V(E)/VCO(2) ratio). The inclusion of VO(2 peak) and demographic data, with submaximal data (V(E)/VCO(2) ratio at an RER = 0.9), increased the predictiveness of the model (C-statistic 0.78). CONCLUSION: Submaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise.     

The predictive value of cardiorespiratory fitness combined with coronary risk evaluation and the risk of cardiovascular and all-cause death

BACKGROUND: There are no data on directly measured cardiorespiratory fitness combined coronary risk evaluation with respect to death from cardiovascular diseases and all-causes. We investigated the prognostic significance of risk scores and cardiorespiratory fitness with respect to cardiovascular disease and all-cause mortality. METHODS: Cardiorespiratory fitness (maximal oxygen uptake, VO2peak) was measured by exercise test with an electrically braked cycle ergometer. The study is based on a random population-based sample of 1639 men (42-60 years) without history of type 2 diabetes or atherosclerotic cardiovascular diseases. RESULTS: During an average follow-up of 16 years, a total of 304 deaths occurred. Independent predictors for all-cause death were European Score (for 1% increment, RR 1.15, 95% CI 1.10-1.20), VO2peak (for 1 MET increment, RR 0.84, 95% CI 0.78-0.89), when adjusted for C-reactive protein, alcohol consumption, serum high-density lipoprotein, waist-to-hip ratio, family history of coronary heart disease, exercise-induced ST changes and the use of medications for hypertension, dyslipidaemia or aspirin. Also, Framingham risk score was related to the risk of death (RR 1.05, 95% CI 1.03-1.07, P < 0.001). Subjects with high European or Framingham score and low VO2peak represent the highest risk group. CONCLUSION: An important finding is that the risk scores can be used to identify men for whom low cardiorespiratory fitness predicts an especially high risk for death from cardiovascular and any other cause.