Cardiopulmonary exercise testing for evaluation of a randomized exercise training intervention following aortic valve replacement

Aortic valve surgery is the definitive treatment for aortic stenosis (AS). No specific recommendation is available on how exercise training should be conducted and evaluated after aortic valve replacement (AVR). This study aimed to examine the effect of aerobic exercise training on exercise capacity following AVR. In addition to our primary outcome variable, peak oxygen uptake (peakVO₂), the effect on submaximal cardiopulmonary variables including oxygen uptake kinetics (tau), oxygen uptake efficiency slope (OUES) and ventilatory efficiency (VE/VCO₂ slope) was evaluated. Following AVR due to AS, 12 patients were randomized to either a group receiving 12 weeks of supervised aerobic exercise training (EX) or a control group (CON). Exercise capacity was assessed by a maximal cardiopulmonary exercise test (CPET). There was a significant increase in peak load (+28%, P = 0·031) and in peakVO₂ (+23%, P = 0·031) in EX, corresponding to an increase in achieved percentage of predicted peakVO₂ from 88 to 104% (P = 0·031). For submaximal variables, there were only non‐statistically significant trends in improvement between CPETs in EX. In CON, there were no significant differences in any maximal or submaximal variable between CPETs. We conclude that 12 weeks of supervised aerobic exercise training induces significant adaptations in cardiopulmonary function following AVR, especially in regard to maximal variables including peakVO₂. In addition, we provide novel data on the effect on several submaximal variables following exercise training in this group of patients.     

Comparison of three methods for detection of the lactate threshold

The lactate threshold (LT) represents the onset of a metabolic acidosis during graded exercise testing (GXT). It is a valuable measurement in clinical exercise testing and correlates well with endurance performance. Our purpose was to compare three LT detection methods, namely, Inspection (work rate at onset of a systematic increase in blood lactate concentration determined by inspection of blood lactate versus work rate plot), 0.5 mM (work rate which just precedes a rise in blood lactate concentration of >0.5 mM) and log-log (work rate at the intersection of two linear lines in plot of log lactate versus log work rate where the residual sum of squares for both lines added together is minimized). Fourteen subjects underwent cycle ergometer GXT with blood samples obtained at the end of each 3-min work rate increment and analysed for lactate concentration. The mean +/- 95% confidence limits of work rates at LT for the Inspection, 0.5 mM and log-log methods were 104.5 +/- 28.0, 103.2 +/- 28.1 and 105.1 +/- 27.3 W, respectively. Repeated-measures analysis of variance yielded a non-significant F ratio. The Bland-Altman bias +/- 95% limits of agreement for Inspection versus 0.5 mM, Inspection versus log-log and 0.5 mM versus log-log were 1.3 +/- 20.6, -0.6 +/- 12.5 and -1.9 +/- 20.5 W, respectively. The intraclass correlation coefficients for Inspection versus 0.5 mM, Inspection versus log-log and 0.5 mM versus log-log were 0.978, 0.992 and 0.977, respectively. The results of this study suggest that all three methods detect the LT at the same work rate.     

下肢运动训练对外周动脉疾病患者小腿经皮氧分压及运动能力的影响

目的:探讨平板及踏车运动对外周动脉疾病患者小腿经皮氧分压(Tc PO2)及运动能力的影响,为不同人群最适运动处方的制定提供方法与依据。方法:将80例外周动脉疾病患者随机分为对照组(26例)、平板运动组(27例)及踏车运动组(27例),对照组予以常规药物治疗,平板及踏车运动组在对照组的基础上分别予以12周平板运动及踏车运动,3组患者在治疗前后行小腿经皮氧分压、6min步行试验及行走受损问卷(WIQ)评估。结果:治疗前三组患者小腿经皮氧分压基线、6min步行试验及行走受损问卷评估均无显著差异(P0.05);12周运动后,与治疗前相比,对照组患者各项评估较治疗前并无显著性差异(P0.05),而平板及踏车运动组均较治疗前改善(P0.05);组间对比,平板及踏车运动组各项评估均优于对照组(P0.05);平板运动组与踏车运动组相比,两组间经皮氧分压基线并无显著差异(P0.05),平板运动组6min步行距离优于踏车运动组(P0.05),而在行走受损问卷评估中踏车运动组表现出更好的爬梯能力,但两组间差异并不显著(P0.05)。结论:下肢运动能够改善外周动脉疾病患者小腿微循环情况,提高患者的运动能力,同时平板及踏车运动有着相似受益程度,对于不能安全行走及运动耐力较低的患者而言,踏车运动可能更为适合。     

Determination of both the time constant of vO2 and DeltavO2/DeltaW from a single incremental exercise test: validation and repeatability

A single incremental cycle exercise test including a steady-state load, combined with respiratory gas exchange, was performed with the objective of determining the time constant (tauVO(2)) and the amount of oxygen required at each load (DeltaVO(2)/DeltaW) by using a novel equation. The protocol was validated using four exercise tests at different constant loads and conventionally fitted mono-exponential functions to determine tauVO(2), and interpolation of VO(2) versus load to determine DeltaVO(2)/DeltaW. No significant differences were seen between the means of either tauVO(2) or DeltaVO(2)/DeltaW determined with the two protocols. The correlation coefficient was 0.62 for tauVO(2) and 0.48 for DeltaVO(2)/DeltaW. The absolute differences (2 SD) were 11.6 s for tauVO(2) and 1.1 ml min(-1) W(-1) for DeltaVO(2)/DeltaW. The equations were compared in the same steady-state test and good agreement of tauVO(2) was obtained (R = 0.99). The 5-6-week repeatability (incremental test) was evaluated. No statistical differences were seen between the mean of the repeated tests. The difference between the tests (2 SD) were 20 s for tauVO(2) and 1.2 ml min(-1) W(-1) for DeltaVO(2)/DeltaW. In conclusion, tauVO(2) and DeltaVO(2)/DeltaW can be determined from a single incremental test. The validation showed an acceptable agreement, although the variations in absolute values were not negligible. This could partly be explained by the natural day-to-day variation and fluctuations in incoming raw data. The test-retest variation in absolute values was considerable, which must be taken into account when using tauVO(2) and DeltaVO(2)/DeltaW for evaluation of aerobic function.     

Reference values for cardiopulmonary exercise testing in healthy adults: a systematic review

Reference values (RV) for cardiopulmonary exercise testing (CPET) provide the comparative basis for answering important questions concerning the normality of exercise response in patients and significantly impacts the clinical decision-making process. The aim of this study is to systematically review the literature on RV for CPET in healthy adults. A secondary aim is to make appropriate recommendations for the practical use of RV for CPET. Systematic searches of MEDLINE, EMBASE and PEDro databases up to March 2014 were performed. In the last 30 years, 35 studies with CPET RV were published. There is no single set of ideal RV; characteristics of each population are too diverse to pool the data in a single equation. Therefore, each exercise laboratory must select appropriate sets of RV that best reflect the characteristics of the population/patient tested, and equipment and methodology utilized.     

Direct comparison of a contractility and activity pacemaker sensor during treadmill exercise testing

There are limited data about the chronotropic capacity of the peak endocardial acceleration (PEA) sensor. This study directly compared the chronotropic function from the PEA and the activity (ACT) sensor. The study included 18 patients (age 73 ± 7 years) with ≥ 75% pacemaker-driven heart rate (HR) and a PEA sensor and 11 healthy controls (age 67 ± 7 years) underwent a chronotropic assessment exercise protocol (CAEP) exercise test with the pacemaker patients in VVIR mode after programming the sensors in the default setting with adjustment of the upper sensor rate as an age related maximum value (220-age). The ACT sensor was externally strapped on the thorax. Achieved exercise duration for the patients and controls was, respectively, 9.2 ± 3 vs 18.4 ± 4 minutes (P < 0.001). The maximal achieved HR with the PEA sensor was 124 ± 25 beats/min, versus the ACT with 140 ± 23, versus the controls with 153 ± 26 beats/min (P < 0.001 between the groups). For the PEA, ACT, and controls, the time to peak HR was, respectively, 11 ± 3, 7 ± 3.6, and 18 ± 4 (P < 0.001 between groups) and HR after 10 minutes recovery was, respectively, 80 ± 20, 65 ± 15, and 82 ± 4 beats/min (P < 0.001 between groups). The PEA sensor functions hypochonotroop during exercise programmed as a single sensor system. It is, therefore, preferable to combine the PEA sensor with an activity-based sensor in a dual sensor system. Although both groups had normal left ventricular functions, the exercise capacity of pacemaker patients is significantly lower than in the controls.     

Relationship between peak cardiac pumping capability and indices of cardio-respiratory fitness in healthy individuals

Cardiac power output (CPO) is a unique and direct measure of overall cardiac function (i.e. cardiac pumping capability) that integrates both flow‐ and pressure‐generating capacities of the heart. The present study assessed the relationship between peak exercise CPO and selected indices of cardio‐respiratory fitness. Thirty‐seven healthy adults (23 men and 14 women) performed an incremental exercise test to volitional fatigue using the Bruce protocol with gas exchange and ventilatory measurements. Following a 40‐min recovery, the subjects performed a constant maximum workload exercise test at or above 95% of maximal oxygen consumption. Cardiac output was measured using the exponential CO₂ rebreathing method. The CPO, expressed in W, was calculated as the product of the mean arterial blood pressure and cardiac output. At peak exercise, CPO was well correlated with cardiac output (r = 0·92, P<0·01), stroke volume (r = 0·90, P<0·01) and peak oxygen consumption (r = 0·77, P<0·01). The coefficient of correlation was moderate between CPO and anaerobic threshold (r = 0·47, P<0·01), oxygen pulse (r = 0·57, P<0·01), minute ventilation (r = 0·53, P<0·01) and carbon dioxide production (r = 0·56, P<0·01). Small but significant relationship was found between peak CPO and peak heart rate (r = 0·23, P<0·05). These findings suggest that only peak cardiac output and stroke volume truly reflect CPO. Other indices of cardio‐respiratory fitness such as oxygen consumption, anaerobic threshold, oxygen pulse, minute ventilation, carbon dioxide production and heart rate should not be used as surrogates for overall cardiac function and pumping capability of the heart.     

Test-retest reliability for two indices of ventilatory efficiency measured during cardiopulmonary exercise testing in healthy men and women

The level of ventilation (VE)) at a given carbon dioxide output (CO2) determines ventilatory efficiency. During cardiopulmonary exercise testing (CPET), ventilatory efficiency can be measured as the slope of the (VE) versus VCO2 relationship or the lowest VE/VCO2. We evaluated the test-retest reliability of these two ventilatory efficiency indices in 29 healthy subjects (14 males). Each subject performed duplicate cycle ergometer tests on different days. Ventilation and the gas fractions for oxygen and CO2 were measured with a Vacumed metabolic cart. Linear regression analysis of the VE versus VCO2 slope for the duplicate tests in the males, females, and both sexes combined yielded correlation coefficients of 0.822, 0.942, and 0.910, respectively. The corresponding correlation coefficients for the lowest VE/VCO2 were 0.745, 0.929, and 0.884. A comparison of the test-retest correlation coefficients between the two ventilatory efficiency measures for the men, women, and both sexes combined revealed that they were not significantly different and, for a given index, there were no sex differences. The bias (mean of difference scores between tests) and 95% limits of agreement for the VE versus VCO2 slope in the males, females, and both sexes combined were -0.05 +/- 2.41, -0.57 +/- 1.92, and -0.32 +/- 2.20, respectively. The bias and 95% limits of agreement for the lowest VE/VCO2 were very similar with values of 0.06 +/- 2.45, -0.22 +/- 2.03, and -0.10 +/- 2.27. We conclude that the test-retest reliability for the VE versus VCO2 slope and the lowest VE/VCO2 is the same and that there is no sex difference in reliability for either index of ventilatory efficiency.     

Prognostic predictors for survival in patients with COPD using cardiopulmonary exercise testing

We studied the relationship between physiologic parameters in cardiopulmonary exercise testing (CPET) and prognosis in terms of survival time in patients with chronic obstructive pulmonary disease (COPD) in order to accurately assess the severity of the disease. From a group of 195 patients with COPD who had consecutively undergone CPET between July 1989 and October 1997, we enrolled 120 subjects (mean age 67.6 years, 104 males) with exertional dyspnoea into a cohort protocol. Of these subjects, 34 (28.3%) died during the 3-5-year follow-up period after CPET. By univariate analysis, the following factors were significantly associated with survival time: age, body mass index, %FVC, %FEV1, FEV1%, PaCO2 at rest, severity of exercise-induced hypoxemia evaluated by DeltaPaO2/DeltaVO2 (PaO2-slope), oxygen uptake, ventilation, tidal volume, PaCO2 and oxygen pulse at maximum exercise, as well as prescribing long-term oxygen therapy. By multivariate analysis, age and the PaO2-slope showed significance as independent prognostic factors, and the PaO2-slope was most closely associated with the survival time. These results reveal that CPET is a useful technique to accurately assess the relationship between the functional impairments and the prognosis of patients with COPD.     

Influence of work rate on the determinants of oxygen deficit during short-term submaximal exercise: implications for clinical research

Objective: The effect of increasing work rate was studied on the determinants of the oxygen deficit. Methods: Exercise testing was performed on a treadmill and gas exchange was measured on a breath‐by‐breath basis. Eleven healthy subjects, aged 18–25 years, performed three square wave exercise tests of different intensity. Before exercise, gas exchange was measured at rest in the standing position for 3 min, followed by a 6‐min square wave exercise test, randomly assigned at 4, 8 or 12% inclination. Immediately after exercise the recovery gas exchange was determined for 3 min. To calculate oxygen deficit, the oxygen uptake (O₂) values at onset of exercise were subtracted from the steady‐state value, the differences were cumulated and expressed as a percentage of the total oxygen cost for the 6‐min exercise. Results: The oxygen deficit increased significantly (P<0·001) with increasing work rate (6·1 ± 1·4% for 4%, 8·4 ± 2·1% for 8% and 9·4 ± 1·7% at 12% inclination). This resulted from a somewhat slower increase of O₂ at the onset of exercise at the highest work rate, reflected by a significantly higher time constant for O₂ at 8 and 12% (24·6 ± 7·3 s at 8% and 24·1 ± 6·3 s at 12% versus 20·2 ± 8·1 s at 4%). More importantly a significantly higher steady‐state value for O₂ was found at the highest exercise level, compared with the other exercise intensities. Conclusion: The higher oxygen deficit at the highest level of exercise is determined by a slower time constant and a higher asymptote value for O₂.     

Physiological characteristics and hormonal profile of young normotensive men with exaggerated blood pressure response to exercise

Exaggerated blood pressure (BP) response to exercise in normotensive subjects is considered as a predictor of future hypertension. The aim of the study was to find out whether elevated BP response to exercise is associated with any other haemody-namic, metabolic or hormonal abnormalities. Abnormal BP response to exercise, i.e. systolic BP (SBP)>200 mmHg at 150 W or lower workload, was found in 37 out of 180 normotensive, male students, aged 20–24 years. Fifteen students with elevated exercise BP (group E) volunteered for further examinations. Their resting and ambulatory BP showed high normal values. Eight of them had a family history of hypertension. Four subjects met the criteria of cardiac hypertrophy. Significant correlations were found between exercise SBP and left ventricular mass index, average 24 h and daytime SBP recordings. In comparison with normal subjects of the same age (group N, n=13), those from group E did not differ in body mass index, plasma lipid profile, fasting glucose, insulin and catecholamine (CA) concentrations, but had increased erythrocyte sodium content, slightly elevated plasma renin activity and cortisol level. During exercise, E subjects showed greater cardiac output (CO) increases with normal heart rate, total peripheral resistance (TPR) and plasma CA. There were no significant differences between groups in haemodynamic and plasma CA responses to posture change from supine to standing. Glucose ingestion (75 g) caused smaller increases in CO and smaller decreases in TPR in E than in N subjects without differences in BP, blood glucose, plasma insulin and CA. It is concluded that young normotensive men with exaggerated BP response to exercise show some other characteristics that may be considered as markers of predisposition to hypertension or factors promoting the development of hypertension.     

Reference values for cardiopulmonary exercise testing in healthy subjects – an updated systematic review

Introduction: Reference values for cardiopulmonary exercise testing (CPET) parameters provide the comparative basis for answering important questions concerning the normalcy of exercise responses in patients, and significantly impacts the clinical decision-making process.

Areas covered: The aim of this study was to provide an updated systematic review of the literature on reference values for CPET parameters in healthy subjects across the life span.

A systematic search in MEDLINE, Embase, and PEDro databases were performed for articles describing reference values for CPET published between March 2014 and February 2019.

Expert opinion: Compared to the review published in 2014, more data have been published in the last five years compared to the 35 years before. However, there is still a lot of progress to be made. Quality can be further improved by performing a power analysis, a good quality assurance of equipment and methodologies, and by validating the developed reference equation in an independent (sub)sample. Methodological quality of future studies can be further improved by measuring and reporting the level of physical activity, by reporting values for different racial groups within a cohort as well as by the exclusion of smokers in the sample studied. Normal reference ranges should be well defined in consensus statements.     

冠心病患者运动前后血浆内皮素水平变化的研究

目的：研究冠心病患者运动前后血浆内皮素水平的变化,以探讨其内在关系。方法：利用放射免疫测定技术检测了２０ 例已确诊冠心病的患者和１８ 个正常人在运动试验前、中、后的外周血内皮素（ＥＴ）水平。结果：冠心病患者与正常人在静息状态下血浆ＥＴ值比较无统计学意义（ Ｐ＞ ０．０５）; 运动后,冠心病者的血浆ＥＴ值呈逐渐上升趋势,在１ｈ 后最为显著（Ｐ＜０．００１）;而正常人在运动前后血浆ＥＴ值无明显变化（Ｐ＞ ０．０５）。并且经冠状动脉造影发现累及冠脉病变越严重（如多支病变）,则运动后血浆ＥＴ值升高越明显。结论：对有冠状动脉疾病者应减少负荷性运动,避免ＥＴ分泌、释放增加。