P wave height during incremental exercise in patients with chronic airway obstruction.

We examined changes in P wave height in lead 2 of an ECG obtained during progressive exercise in 23 patients with COPD, and measured both P wave changes and pulmonary hemodynamics during exercise at a constant workload corresponding to approximately 50 to 60 percent of VO2 max in nine patients. The P wave response to exercise (delta P/delta VO2, %/ml/min), estimated by the relationship between percentage of change in P wave height and VO2, was significantly greater (p less than 0.01) in 15 patients who had a decrease in PaO2 with exercise (group A) than eight patients who did not have a fall in PaO2 with exercise (group B). There was a significant negative correlation between change in PaO2 and change in P wave height from rest to maximal exercise (r = -0.68, p less than 0.001). Oxygen therapy in nine patients in group A reduced the increase in P wave height during exercise. Furthermore, change in P wave height from rest to exercise correlated significantly with that of mean pulmonary artery pressure (r = 0.75, p less than 0.01). These results suggest that increase in P wave height during exercise in COPD patients is related partly to oxygen desaturation during exercise, and continuous measurement of P wave change may be useful for noninvasively predicting the pulmonary vascular pressure response to exercise.     

Dependence of enhanced maximal exercise performance on increased peak skeletal muscle perfusion during long-term captopril therapy in heart failure

Maximal oxygen uptake (VO2), skeletal muscle blood flow by xenon-133 washout technique and femoral vein arteriovenous oxygen difference and lactate were measured at rest and during maximal bicycle exercise in eight patients with severe congestive heart failure before and after 8 weeks of therapy with captopril. During therapy, skeletal muscle blood flow at rest increased significantly from 1.5 +/- 0.6 to 2.6 +/- 1.0 ml/100 g per min (p less than 0.05), with a concomitant decrease in the femoral arteriovenous oxygen difference from 10.0 +/- 1.7 to 8.3 +/- 1.9 ml/100 ml (p less than 0.05). Maximal VO2 increased significantly from 13.4 +/- 3.0 to 15.5 +/- 4.1 ml/kg per min (p less than 0.05). In four patients, the increase in maximal VO2 averaged 3.7 ml/kg per min (range 2.7 to 4.9), whereas in the remaining four patients, it was less than 1 ml/kg per min. Overall, peak skeletal muscle blood flow attained during exercise did not change significantly during long-term therapy with captopril (19.6 +/- 6.2 versus 27.6 +/- 14.3 ml/100 g per min, p = NS). However, the four patients with a significant increase in maximal VO2 experienced substantial increases in peak skeletal muscle blood flow and the latter changes were linearly correlated with changes in maximal VO2 (r = 0.95, p less than 0.001). Femoral arteriovenous oxygen difference at peak exercise was unchanged (12.6 +/- 2.6 versus 12.6 +/- 2.4 ml/100 ml). Thus, improvement in maximal VO2 produced by long-term therapy with captopril is associated with an increased peripheral vasodilatory response to exercise, and this improvement only occurs when the peak blood flow is augmented.(ABSTRACT TRUNCATED AT 250 WORDS)     

Predictors of exercise benefit after operative relief of left ventricular outflow obstruction by the myotomy-myectomy procedure in hypertrophic cardiomyopathy.

To determine predictors of exercise benefit in patients with hypertrophic cardiomyopathy after operative relief of left ventricular (LV) outflow tract obstruction, 30 patients underwent catheterization and exercise testing before and 6 months after operation, and hemodynamic measurements were obtained. The increase in maximal oxygen consumption (VO2max) during treadmill exercise testing was chosen as an index of exercise benefit. Univariate analysis showed a significant positive correlation of operative change in VO2max with preoperative LV end-diastolic and pulmonary arterial wedge pressures, operative change in exercise duration, and operative reductions in LV end-diastolic and pulmonary arterial wedge pressures and resting LV outflow tract gradient, and a significant negative correlation with preoperative VO2max and percent predicted VO2max. Multivariate analysis by stepwise linear regression of only significant univariate variables selected only preoperative percent predicted VO2max, and operative reduction in LV end-diastolic pressure and resting LV outflow tract gradient as significant predictors of postoperative change in VO2max. Stepwise regression analysis, applied only to preoperative exercise and catheterization hemodynamic variables, selected only preoperative percent predicted VO2max and preoperative LV end-diastolic pressure as predictors of improvement in exercise capacity. Thus, patients with obstructive hypertrophic cardiomyopathy, after failing medical therapy, are most likely to demonstrate improvement in exercise capacity if preoperative exercise testing demonstrates limited exercise capacity and if surgery achieves reduction in elevated resting LV outflow tract gradients and LV filling pressures.     

慢性阻塞性肺疾病患者运动能力与通气效率的相关性分析

目的:通过分析二氧化碳通气当量和运动能力的关系,探讨稳定期慢性阻塞性肺疾病(COPD)患者运动中通气效率与最大运动能力的相关性。方法:选取54例稳定期COPD患者,行运动心肺功能测试,实时监测摄氧量(VO2)、分钟通气量(VE)和二氧化碳排出量(VCO2),根据公式:EqCO2=VE/VCO2计算得出静态二氧化碳通气当量(EqCO2rest)、无氧阈时二氧化碳通气当量(EqCO2at)和最大运动状态下的二氧化碳通气当量(EqCO2max)。结果:1.EqCO2rest、EqCO2at及EqCO2max呈递减趋势,差异有统计学意义(P=0.001)。2.EqCO2at与最大摄氧量(VO2max)(r=-0.294,P<0.05)、EqCO2max与VO2max(r=-0.301,P<0.05)均呈负相关;EqCO2rest与最大摄氧量占预计值的百分比(VO2max/Pred)呈负相关(r=-0.345,P<0.05)。3.肺功能GOLD 3级患者(21例)的VO2max(15.99±3.39)mL·min-1·kg-1明显低于GOLD 2级患者(25例)的VO2max[(18.88±5.36)mL·min-1·kg-1,P=0.038]。两组的EqCO2rest、EqCO2at及EqCO2max差异无统计学意义。结论:稳定期COPD患者运动中通气效率呈进行性下降趋势,这可能是导致其运动能力下降的重要因素之一。     

Oxygen transport and oxygen consumption during supplemental oxygen administration in patients with chronic obstructive pulmonary disease

PURPOSE: Oxygen consumption (VO2) is independent of oxygen delivery (DO2) above a critical level of DO2. VO2 may become dependent on DO2 when oxygen demand exceeds oxygen supply. We studied DO2 VO2, and exercise capacity in 12 stable, ambulatory patients with chronic obstructive pulmonary disease (COPD) receiving ambient air and 26% oxygen to ascertain whether VO2 is dependent on DO2 in this patient sample. PATIENTS AND METHODS: An exercise protocol consisting of a symptom-limited, low-level treadmill test with progressive increments in workload was performed twice, once with patients breathing ambient air and once with patients breathing 26% oxygen. Expired gas, arterial and mixed venous blood values, and recordings of systemic and pulmonary artery pressures were obtained after a 10-minute period of rest (while standing) and during the last minute of each three-minute exercise level. RESULTS: Five patients had an increase in exercise capacity, defined as an increase in the maximal VO2 greater than 25%, using supplemental oxygen. In these patients, oxygen delivery increased from 10.9 +/- 3.4 to 13.8 +/- 4.7 mL/minute/kg (p = 0.008) at rest and from 16.2 +/- 5.0 to 24.7 +/- 2.7 mL/minute/kg (p = 0.046) during exercise with supplemental oxygen administration. VO2 increased from 0.329 +/- 0.065 to 0.436 +/- 0.109 L/minute (p = 0.029) at rest and from 0.776 +/- 0.275 to 1.119 +/- 0.482 L/minute (p = 0.048) during exercise. Three of these five patients had an arterial oxygen pressure greater than 55 mm Hg at rest. Seven patients had little or no increase in exercise capacity with supplemental oxygen. This patient group had no increase in VO2 at rest. The DO2 failed to increase at rest despite an increase in arterial oxygen content because of a reduction in cardiac output. CONCLUSION: These data demonstrate that DO2 may fail to increase in some patients with COPD and resting or exertional hypoxemia when supplemental oxygen is administered because of a reduction in cardiac output; that patients who fail to increase their DO2 are less likely to increase exercise capacity; and that some stable, ambulatory patients with COPD who do not qualify for supplemental oxygen at rest by current standards may have inadequate DO2 to meet physiologic needs.     

Exercise outcomes after pulmonary rehabilitation depend on the initial mechanism of exercise limitation among non-oxygen-dependent COPD patients

STUDY OBJECTIVES: Pulmonary rehabilitation (PR) that includes exercise training can improve exercise tolerance and quality of life for patients with COPD. However, the degree of benefit from PR is variable. We hypothesized that the exercise response to PR varies depending on the initial factors that limit exercise. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: We retrospectively analyzed the change in exercise capacity after PR in 290 nonhypoxemic patients with COPD. We classified patients into the following subgroups based on the primary limitation seen on initial exercise testing: (1) ventilatory-limited (VL); (2) cardiovascular-limited (CVL); (3) mixed ventilatory/cardiovascular-limited (VLCVL); and (4) non-cardiopulmonary-limited (NL). We compared outcomes among subgroups. RESULTS: In the entire study population, PR led to increased timed walk distance (30.3%; p < 0.0001) and maximal oxygen consumption (VO2max) [84.8 mL/min; p < 0.0001]. Stepwise multiple regression selected age, ventilatory reserve at peak exercise, and exercise arterial oxygen pressure as individual predictors of improvement in VO2max. VO2max increased in the VL subgroup (30.4 mL/min; p = 0.008), the CVL subgroup (109.0 mL/min; p < 0.0001), the mixed VLCVL subgroup (61.3 mL/min; p < 0.0001), and NL subgroups (110.5 L/min; p < 0.0001). The improvement in VO2max was greater in the CVL subgroup than in the VL subgroup (p < 0.0001). Timed walk distance improved to a similar degree in all subgroups (26 to 36%). CONCLUSIONS: Patients with nonventilatory exercise limitations experience the greatest increase in VO2max after PR. However, even patients with severe ventilatory limitation can improve exercise tolerance with PR.     

Effects of high-intensity exercise training in a pulmonary rehabilitation programme for patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVES: The benefits of pulmonary rehabilitation for patients with COPD depend on the intensity of training. Traditional pulmonary rehabilitation programmes (PRPs) do not consistently achieve high-intensity training and have variable training effects. This study examined the effects of high-intensity exercise training on cardiac and pulmonary function in COPD patients. METHODS: Patients with COPD participated in a 6-week, cardiopulmonary exercise test-based PRP. Spirometry, 6-min walking distance and cardiopulmonary exercise test were used to evaluate cardiopulmonary function, respiratory muscle strength and endurance at rest, during exercise and before and after the programme. Patients were encouraged to complete high-intensity exercise with a targeted training intensity of at least 75% maximum oxygen uptake (VO(2)). RESULTS: Thirty-four COPD patients were enrolled into the study; 16 completed the high-intensity training, 18 did not. At the end of the 12-session PRP, submaximal exercise capacity (6-min walking distance, 461.8 +/- 77.2-502.7 +/- 66.9 m, P < 0.001) improved in both the patients who completed high-intensity training and those who did not. Only the patients who completed high-intensity training had significant improvements in FVC (2.47 +/- 0.70-2.70 +/- 0.62 L, P = 0.024) at rest, maximal exercise capacity (peak VO(2), 1001.6 +/- 286.4-1116.1 +/- 320.4 mL/min, P = 0.020) and work efficiency (7.3 +/- 1.4-8.4 +/- 1.8 mL/min/watt, P = 0.026). There was no statistically significant difference between the two groups in the change in the physiological parameters before and after exercise. CONCLUSIONS: Exercise training in a PRP improved submaximal exercise capacity. Only patients who completed high-intensity exercise training showed improvements in maximal exercise capacity, FVC and work efficiency.     

The body weight-walking distance product as related to lung function, anaerobic threshold and peak VO2 in COPD patients.

The product of walking distance and body weight (D x W) mimics the work of walking. We hypothesized the superiority of D x W to walking distance (D) alone in any correlation with lung function, anaerobic threshold (AT) and maximal oxygen uptake (VO2max). We further hypothesized that the D x W product for a 6-min walk test (6 MWT) would correlate with the AT and VO2max because all three are markers of exercise ability. Thirty-three male chronic obstructive pulmonary disease (COPD) patients with mean forced expiratory volume in 1 sec (FEV1) of 1.2+/-0.4 l (range 0.58-1.86 l) were enrolled. Six patients were excluded due to inability to achieve a maximal test. Lung function and self-assessed every-day activities using a oxygen-cost diagram were evaluated before entry of the study. A maximal effort ramp-pattern cardiopulmonary exercise test (CPET) and a 6 MWT were conducted in random order. Borg score, heart rate, and O2 saturation with pulse oximetry (SpO2) were measured during both exercise tests. VO2 AT and minute ventilation were also measured during the CPET. Correlations were sought between the distance covered in the 6 MWT, and the D x W product with AT, VO2max and other variables. The average D and D x W were 456 m and 27.5 kg km(-1), respectively. D x W was superior to D alone when correlated with the VO2max and AT determined from the CPET, while modestly correlated with the change (delta) in Borg score and delta SpO2 in the 6 MWT and self-assessed every-day activities. Distance x weight product was correlated with the AT and VO2max. In addition, D x W was better correlated with diffusing capacity for carbon monoxide and vital capacity than D alone. We conclude that D x W mimics the work of walking better than D and is suggested as a parameter for evaluation of patients' fitness if gas exchange measurements are not available.     

Comparison of estimated and measured maximal oxygen uptake during exercise testing in patients with chronic obstructive pulmonary disease

BACKGROUND: Maximal oxygen uptake (VO(2max)) and exercise modalities such as walking and standard pulmonary function testing are measurements that have been used by the surgical community as an indication of a patient's current exercise capacity to predict operative outcomes. There are equations available in published reports that allow an estimate of VO(2max) to be made by measuring a combination of the distance walked as well as lung function in patients with chronic obstructive -pulmonary disease (COPD). AIMS: The aim of the present study was to determine if estimates of VO(2max) and measured VO(2max) based on predictive equations are useful in individuals with COPD. METHODS: Twenty-eight male patients (mean age 68 years) with a mean forced expiratory volume in 1 s of 1.3 L were enrolled in the study after determining that they could perform a maximal exercise study. The estimated VO(2max) using equations reported by Chuang et al. and Cahalin et al. was cross-validated with the measured VO(2max) determined during cardiopulmonary exercise testing. RESULTS: The mean estimated VO(2max) using the pre-diction equation did not differ from the mean measured VO(2max) (1.13 vs 1.18 L/min, respectively; P = 0.25). However, the scattered relationship between the measured and the estimated VO(2max) did not support the use of this equation to predict an individual's performance. The prediction equations currently available in published reports significantly underestimate the measured VO(2max) (P < 0.05-10(-12)). CONCLUSIONS: It is recommended that VO(2max) is measured rather than estimated using the prediction equations when a VO(2max) measurement is used for clinical decision-making.     

摄氧量平均反应时间在重度慢性阻塞性肺疾病患者心肺功能评估中的应用研究

目的 探讨重度慢性阻塞性肺疾病(COPD)患者在心肺运动试验(cardiopulmonary exercise test,CPET)检测零负荷热身期中的摄氧量动力学改变特点,研究零负荷热身期间摄氧量平均反应时间(mean response time,MRT)与COPD患者心肺功能及常规肺功能的相关性,探讨MRT值评价重...     

Body composition analysis by dual energy X-ray absorptiometry and exercise performance in underweight patients with COPD

STUDY OBJECTIVES: The aim of this study was to examine the effect of body composition on maximal exercise performance in patients with COPD. METHODS: The study was carried out on 27 patients with COPD and was confirmed by pulmonary function testing. Body composition was measured by dual energy x-ray absorptiometry (DXA). Exercise performance was conducted on a cycle ergometer and was measured as maximal work rate (WRmax) and maximal oxygen uptake (VO2max). Bone mineral content (BMC), lean mass (LEAN), and fat mass (FAT) were assessed by DXA and were expressed as a percentage of ideal body weight, BMC, LEAN, and FAT. RESULTS: LEAN% correlated significantly with VO2max (r = 0.66, p = 0.0002) and WRmax (r = 0.70, p < 0.0001). No significant correlation was found between FAT% and exercise performance. By stepwise regression analysis, variables significantly contributing to WRmax and VO2max were LEAN% and the maximal voluntary ventilation. Total variance explained in these models was 81% for WRmax aid 82% for VO2max. CONCLUSION: Lean mass was an important determinant of maximal exercise performance in patients with COPD.     

Reduced mechanical efficiency in chronic obstructive pulmonary disease but normal peak VO2 with small muscle mass exercise

We studied six patients with chronic obstructive pulmonary disease (COPD) (FEV1 = 1.1 +/- 0.2 L, 32% of predicted) and six age- and activity level-matched control subjects while performing both maximal bicycle exercise and single leg knee-extensor exercise. Arterial and femoral venous blood sampling, thermodilution blood flow measurements, and needle biopsies allowed the assessment of muscle oxygen supply, utilization, and structure. Maximal work rates and single leg VO2max (control subjects = 0.63 +/- 0.1; patients with COPD = 0.37 +/- 0.1 L/minute) were significantly greater in the control group during bicycle exercise. During knee-extensor exercise this difference in VO2max disappeared, whereas maximal work capacity was reduced (flywheel resistance: control subjects = 923 +/- 198; patients with COPD = 612 +/- 81 g) revealing a significantly reduced mechanical efficiency (work per unit oxygen consumed) with COPD. The patients had an elevated number of less efficient type II muscle fibers, whereas muscle fiber cross-sectional areas, capillarity, and mitochondrial volume density were not different between the groups. Therefore, although metabolic capacity per se is unchanged, fiber type differences associated with COPD may account for the reduced muscular mechanical efficiency that becomes clearly apparent during knee-extensor exercise, when muscle function is no longer overshadowed by the decrement in lung function.     

O2 extraction during exercise determines training effect after cardiac rehabilitation in myocardial infarction.

Correlations between baseline hemodynamic and oximetric variables during an invasive exercise test and an improvement in peak oxygen uptake (peak VO2) after exercise training (ET) were examined in 20 patients who participated in a cardiac rehabilitation program after acute myocardial infarction (AMI). Peak VO2 significantly increased by 23 +/- 21% (p < 0.01) after ET and the improvement best correlated with the change in O2 extraction fraction ([arterial O2 content-venous O2 content]/arterial O2 content) during an exercise testbefore ET (r = -0.61, p<0.01). Exercise capacity was improved to a greater extent by ET in patients with a smaller increase in O2 extraction fraction during an exercise test before ET. Thus, O2 extraction fraction during an exercise test before ET may be a useful predictor of the improvement in exercise capacity after ET in post-AMI patients.     

Physiologic responses during the six minute walk test in obese and non-obese COPD patients

Although obesity is a common co-morbid condition in COPD, relatively little is known how it may affect functional exercise capacity. Accordingly, we compared physiologic responses during a 6 min walk test in 10 obese and 10 non-obese COPD patients matched by gender, age, and spirometric severity category. Patients first exercised on a treadmill to determine maximal exercise responses, then following a rest period they completed a 6 min walk test. Breath by-breath analyses of expired air via a facemask was obtained using a portable, battery operated device. Oxygen consumption (VO(2)), carbon dioxide production (VCO(2)), tidal volume (VT), respiratory rate (RR), minute ventilation (VE), and inspiratory capacity (IC) were compared. The mean FEV1 in the obese and non-obese groups was 52 ± 13 and 58 ± 18 percent of predicted, respectively, and the BMI of the obese patients was 37 ± 02 kg/m(2). Obese patients had shorter 6 min walk distances than non-obese patients (247 ± 73 vs 348 ± 51 m, respectively, p = 0.003), but walk-work, defined as 6 min walk distance × weight (in kg), was not different. There were no significant between-group differences in any exercise variable measured during the 6 min walk test. In both groups, VO(2) and VE increased linearly over the first 2-3 min, then plateaued at approximately 80% of maximum. Although 6 min walk distance is shorter in obese COPD patients, their physiologic responses are similar to those of non-obese patients.     

Factors associated with improvement in breathing capacity during exercise in patients with chronic obstructive pulmonary disease

OBJECTIVES: The aim of this study was to explore the relationship between resting pulmonary function indices and the ratio of minute ventilation at peak exercise to the maximal voluntary ventilation (VEmax/MVV) and to determine whether an improvement in breathing capacity during exercise (i.e. VEmax/MVV > 1) is associated with greater exercise capacity in patients with COPD. METHODOLOGY: The results of pulmonary function tests and incremental, symptom-limited cardiopulmonary exercise testing in 84 patients with predominantly moderate to severe COPD were reviewed. Multiple linear regression analysis was applied to determine the relationship of VEmax/MVV with selected independent variables at rest. Multiple logistic regression was used to determine significant predictors of VEmax/MVV 1. RESULTS: FEV1/FVC and inspiratory capacity (IC) were the only variables among resting pulmonary function indices that were significant independent determinants of VEmax/MVV and the stepwise analysis generated the following equation: VEmax/MVV = (-1.05E-02 x FEV1/FVC) + (0.15 x IC) + 1.28; r= 0.701, P < 0.001. Using multiple logistic regression with VEmax/MVV 1 as a dependent categorical variable, FEV1/FVC was the only significant predictor among resting pulmonary indices of a VEmax/MVV ratio of > 1 (Odds ratio 0.93, 95%CI 0.89, 0.97). There was a significant association between VEmax/MVV and peak oxygen uptake (VO2max) after adjusting for FEV1 (r = 0.66, P < 0.001). If the categorical variable of VEmax/MVV ( 1) was used instead of a continuous variable, a significant association with VO2max remained after adjusting for FEV1 (r = 0.60, P < 0.001). CONCLUSIONS: Among resting pulmonary function indices, the FEV1/FVC ratio is the best determinant of an improvement in breathing capacity during exercise in COPD patients. After adjusting for FEV1, an improvement in breathing capacity during exercise is associated with significantly higher exercise capacity.     

Effects of oral morphine on breathlessness and exercise tolerance in patients with chronic obstructive pulmonary disease

Previous studies have shown that opiates increase the maximal external work performed at exhaustion in patients with chronic obstructive pulmonary disease (COPD). The mechanism responsible for this improvement in exercise tolerance is unknown. The purpose of this study was to determine the effects of an oral morphine solution (0.8 mg/kg) on the exercise tolerance, perception of dyspnea, and arterial blood gases of patients with COPD. Thirteen eucapnic patients with stable COPD (FEV1 = 0.99 +/- 0.48) underwent duplicate incremental cycle ergometer tests to exhaustion (Emax) after the ingestion of placebo and after the ingestion of morphine. After the ingestion of morphine, the maximal workload increased by 18% (p less than 0.001) and the VO2 increased by 19.3% (p less than 0.001). Ten of the 13 patients had a higher ventilation at Emax after morphine ingestion. Despite the higher ventilation at Emax after morphine, the mean Borg score was not significantly higher. At Emax after morphine ingestion, the PaO2 (65.8 +/- 11.6 mm Hg) was significantly lower and the PaCO2 (43.5 +/- 8.3 mm Hg) was significantly higher than at Emax after placebo (71.9 +/- 15.5 and 38.3 +/- 8.5, respectively). When data at the highest equivalent workload were analyzed, the ventilation and the Borg scores were significantly lower, whereas the VO2 and VCO2 were comparable. From this study, we conclude that the administration of opiates can substantially increase the exercise capacity of patients with COPD. The improved exercise tolerance appears to be related to both a higher PaCO2 resulting in lowered ventilation requirements for a given workload and also to a reduced perception of breathlessness for a given level of ventilation.     

Arm exercise capacity and dyspnea ratings in subjects with chronic obstructive pulmonary disease

PURPOSE: This study aimed to compare the metabolic, ventilatory, and dyspnea responses to unsupported arm exercise, supported arm exercise and leg exercise between subjects with chronic obstructive pulmonary disease (COPD) and healthy age-matched controls. METHODS: For this study, 21 subjects with COPD (mean age, 62 +/- 2 years; predicted forced expiratory volume in 1 second [FEV(1)], 37 +/- 3%) and 7 healthy age-matched control subjects (% pred FEV(1) = 109 +/- 5%) were included in the analyses of three incremental exercise tests to peak work capacity: unsupported arm exercise, supported arm exercise (arm ergometry), and leg exercise (cycle ergometry). Work level, oxygen consumption (VO(2)), minute ventilation (V(E)), dyspnea, and rate of perceived exertion were measured each minute. RESULTS: Peak work level and peak VO(2) were significantly reduced in the subjects with COPD for all exercise tests (P <.01 for all), as compared with the control subjects. Within the COPD group, the VO(2) and V(E) at peak exercise were significantly lower for unsupported arm exercise than for both the leg and supported arm exercises (both P <.001). The ratio of V(E) to maximal voluntary ventilation was high for leg exercise (96%), supported arm exercise (91%), and unsupported arm exercise (77%) among the subjects with COPD. At a given percentage of VO(2) peak, dyspnea scores were similar for all the exercise tests. CONCLUSIONS: Ventilatory constraints limit exercise performance in COPD. The lowest amount of work, in terms of VO(2,), was during unsupported arm exercise. Because the subjects with COPD had scores showing similar levels of dyspnea at the same percentage of VO(2) peak, it is suggested that patients be encouraged to reach equivalent dyspnea levels when performing unsupported and supported arm exercise training and leg training.     

Constant-load cycle endurance performance: test-retest reliability and validity in patients with COPD

The purpose of this study was to evaluate the rest-retest reliability and validity of a constant-load endurance exercise test on a cycle ergometer with a workload of 75% of maximal work capacity (W(max)) in patients with moderate to severe chronic obstructive pulmonary disease (COPD). In 60 patients with COPD (FEV(1) 40 +/- 15% pred), exercise endurance time was measured with a constant-load endurance exercise tests at 75% of W(max), on two different occasions. In a subgroup of 20 patients, test-retest reliability of the measurement of end-exercise ventilatory and metabolic responses was assessed. Validity of the cycle endurance test was assessed comparing endurance time and total work performed during the cycle endurance test to peak oxygen uptake (VO(2peak)) and the 12-minute walking distance (12MWD).Test and retest assessments of cycle endurance time did not differ statistically significantly (P =.40). Highly significant intraclass correlation coefficients (ICC > or = 0.85; P <.001) were found between test and retest of assessment of endurance time as well as of end-exercise ventilatory and metabolic responses. In addition, statistically significant correlation coefficients were found between VO(2peak) and endurance time (r = 0.50; P =.001) and total work performed (r = 0.72; P <.001) during the constant-load cycle test. Significant correlation coefficients of the same magnitude were found between 12MWD and endurance time (r = 0.58; P =.001) and total work performed (r = 0.72; P <.001) during the constant-load cycle test. It is concluded that constant-load exercise testing on a cycle ergometer with a workload of 75% of maximal work capacity is a reliable and valid method to assess exercise endurance in patients with COPD.     

Effect of betaxolol on the hemodynamic, gas exchange, and cardiac output response to exercise in chronic atrial fibrillation

BACKGROUND: beta-blockade controls the ventricular response to exercise in chronic atrial fibrillation (AF), but the effects of beta-blockers on exercise capacity in AF have been debated. METHODS: Twelve men with AF (65+/-8 years) participated in a randomized, double-blind, placebo-controlled study of betaxolol (20 mg daily). Patients underwent maximal exercise testing with ventilatory gas exchange analysis, and a separate, submaximal test (50% of maximum) during which cardiac output was measured by a CO2 rebreathing technique. RESULTS: After betaxolol therapy, heart rate was reduced both at rest (92+/-27 vs 62+/-12 beats/min; p < 0.001) and at peak exercise (173+/-22 vs 116+/-24 beats/min; p < 0.001). Maximal oxygen uptake (VO2) was reduced by 19% after betaxolol (21.8+/-5.3 with placebo vs 17.6+/-5.1 mL/kg/min with betaxolol; p < 0.05), with similar reductions observed for maximal exercise time, minute ventilation, and CO2 production. VO2 was reduced by a similar extent (19%) at the ventilatory threshold. Submaximal cardiac output was reduced by 15% during betaxolol therapy (12.9+/-2.3 vs 10.9+/-1.3 L/min; p < 0.05), and stroke volume was higher (88.0+/-21 vs 105.6+/-19 mL/beat; p < 0.05). CONCLUSION: Betaxolol therapy in patients with AF effectively controlled the ventricular rate at rest and during exercise, but also caused considerable reductions in maximal VO2 and cardiac output during exercise. The observed increase in stroke volume could not adequately compensate for reduced heart rate to maintain VO2 during exercise.     

Dynamic hyperinflation and exercise intolerance in chronic obstructive pulmonary disease.

The role of dynamic hyperinflation (DH) in exercise limitation in chronic obstructive pulmonary disease (COPD) remains to be defined. We examined DH during exercise in 105 patients with COPD (FEV(1) = 37 +/- 13% predicted; mean +/- SD) and studied the relationships between resting lung volumes, DH during exercise, and peak oxygen consumption (VO(2)). Patients completed pulmonary function tests and incremental cycle exercise tests. We measured the change in inspiratory capacity (Delta IC) during exercise to reflect changes in DH. During exercise, 80% of patients showed significant DH above resting values. IC decreased 0.37 +/- 0.39 L or 14 +/- 15% predicted during exercise (p < 0.0005), but with large variation in range. Delta IC correlated best with resting IC, both expressed %predicted (r = -0.50, p < 0.0005). Peak VO(2) (%predicted maximum) correlated best with the peak tidal volume attained (VT standardized as % of predicted vital capacity) (r = 0.68, p < 0.0005), which, in turn, correlated strongly with IC at peak exercise (r = 0.79, p < 0.0005) or at rest (r = 0.75, p < 0.0005). The extent of DH during exercise in COPD correlated best with resting IC. DH curtailed the VT response to exercise. This inability to expand VT in response to increasing metabolic demand contributed importantly to exercise intolerance in COPD.