SEARCH · PubMed Health

Results for “Exercise Tolerance”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

PubMed1992

Regional blood flow in chronic heart failure: the reason for the lack of correlation between patients' exercise tolerance and cardiac output?

BACKGROUND: In patients with chronic heart failure there is no relation between cardiac output and symptom limited exercise tolerance measured on a bicycle or treadmill. Furthermore, the increase in cardiac output in response to treatment may not be matched by a similar increase in exercise tolerance. More important in determining exercise capability is blood flow to skeletal muscle. This implies that the reduction in skeletal muscle blood flow is not directly proportional to the reduction in cardiac output and that there are regional differences in blood flow in patients with heart failure. METHODS: Cardiac output and regional blood flow measured in 30 patients with chronic heart failure were compared with values obtained from 10 healthy controls. Measurements were made at rest and in response to treadmill exercise and were all made non-invasively. RESULTS: Cardiac output was lower in the patients at rest and during exercise. Blood flow in the superior mesenteric and renal arteries was also lower in the patients and represented a different proportion of cardiac output than in the controls. In response to exercise the increase in blood flow to the calf and therefore to skeletal muscle, was reduced in the patients. In the patients there was no correlation between resting cardiac output and blood flow in the superior mesenteric artery, renal artery, or calf. CONCLUSIONS: Because blood flow to skeletal muscle and to the kidneys is likely to be important in determining patients' symptoms this factor may explain why central haemodynamic variables do not correlate with the exercise tolerance in patients with chronic heart failure.

Aged↗

PubMed2004

Effects of exercise training after open heart surgery on quality of life and exercise tolerance in patients with mitral regurgitation or aortic regurgitation.

We conducted a questionnaire survey regarding quality of life (QOL) to evaluate the effects of exercise training on the QOL in patients with valvular heart disease after surgery. This study included 64 consecutive patients who underwent heart surgery. They were divided into two groups: exercise training could (EX(+) group, n = 31) and could not be performed (EX(-) group, n = 33) until 6 months after surgery. To evaluate the QOL and exercise tolerance, we employed "a questionnaire regarding disease and quality of life" developed for Japanese people and cardiopulmonary exercise testing. In our questionnaire survey, the improvement rating (Delta subjective/social index), which was calculated from the difference between the pre-and postoperative values, was greater in the EX(+) group than that in the EX(-) group (4.9 +/- 3.1 versus 1.1 +/- 4.0, P < 0.05). In the changes in exercise tolerance, Delta anaerobic threshold was greater in the EX(+) group (0.79 +/- 0.17 versus -0.02 +/- 0.28, P < 0.01). Moreover, there was a positive correlation between Delta subjective/social index and Delta peak VO(2) (r = 0.62, P < 0.05). We concluded that exercise training for patients after cardiac surgery improves the QOL and exercise tolerance. It is suggested that changes in subjective and social parameters contribute to an exercise training-related improvement in the QOL.

Aged↗

PubMed1995

Cardiopulmonary evaluation of exercise tolerance after chest irradiation and anticancer chemotherapy in children and adolescents.

OBJECTIVE: The aim of the study was to evaluate the cardiopulmonary exercise tolerance in children and adolescents after chest irradiation and anticancer chemotherapy. METHODS: We studied 30 subjectively asymptomatic patients aged 8 to 25 years treated for pediatric malignancies with chest irradiation (XRT) +/- chemotherapy. The median interval since XRT was 7 (range, 2 to 13) years. The median XRT dose for mediastinum and/or lungs was 2550 (range, 1000 to 5100) cGy. The median cumulative dose of anthracyclines was 250 (range, 0 to 480) mg/m2. Cardiac function and exercise tolerance were evaluated by electrocardiography, echocardiography, radionuclide cineangiography, and exercise test with gas exchange analysis. RESULTS: The patients differed from normal controls in systolic indices of myocardial function. In echocardiography, the left ventricular contractility was abnormal in 14/30 patients. In radionuclide cineangiography, the left ventricular ejection fraction was subnormal in 6/30 patients, and in 9/30 patients the rise in ejection fraction during exercise was inadequate (< 5%). In exercise testing, the mean (+/- SD) maximum workload attained was 2.7 (+/- 0.7) watts/kg, and the mean (+/- SD) maximum oxygen consumption was 35.4 (+/- 9.7) mL/min/kg. Both variables were < 80% of predicted values in 11 patients. CONCLUSIONS: XRT and anticancer chemotherapy very often lead to late cardiopulmonary toxicity and impaired exercise tolerance. Although in most cases this toxicity seemed to be mild and subclinical, the long-term clinical sequels merit further evaluation.

Adolescent↗

PubMed1983

Improved exercise tolerance of the polycythemic lung patient following phlebotomy.

The present study evaluated the effects of therapeutic phlebotomy on the exercise tolerance and the maximal carbon dioxide output of polycythemic patients with chronic obstructive pulmonary disease. Fifteen maximal exercise studies were performed before and after phlebotomy in patients with moderate to severe chronic obstructive pulmonary disease (mean forced expiratory volume in one second [FEV1]= 970 ml). After phlebotomy there were no significant differences in pulmonary function, blood gases, oxygen consumption, or carbon dioxide production at rest. However, after phlebotomy there was a significant increase in the exercise tolerance of the patients. The mean workload, the duration of exercise, the maximal oxygen consumption, the maximal carbon dioxide production, and the ventilation at maximal exercise all increased significantly. The improved exercise tolerance after phlebotomy appeared due to an increased cardiac output generated mainly through an increased stroke volume. We hypothesize that the increased stroke volume was due to a higher ejection fraction of the right ventricle secondary to a lower pulmonary artery pressure. This study provides further evidence that patients with chronic obstructive pulmonary disease who have polycythemia benefit by therapeutic interventions that maintain their hematocrits below 55 percent.

Aged↗

PubMed1999

Effect of ticlopidine on exercise-induced platelet aggregation and exercise tolerance time in patients with ischemic heart disease.

Platelet aggregation is one of the most important mechanisms for acute myocardial infarction during exercise. We sought to evaluate the effect of ticlopidine (TP) on platelet aggregation (PA) during exercise in patients with ischemic heart disease (IHD). We studied 38 patients with IHD, 26 patients with effort angina pectoris, and 12 patients with a previous myocardial infarction. In protocol I, subjects were divided into two groups. Drugs altering platelet aggregation were withheld 2-4 weeks before the study in 25 patients (control group). TP (200 mg/day) was administered for 7 days in 13 patients (ticlopidine group). A symptom-limited modified Bruce protocol treadmill exercise test was performed. PA was measured at rest and after exercise by using optical densitometry induced by adenosine diphosphate (ADP). PA ratio (percentage of maximum) was compared. In protocol II, in 12 patients, treadmill exercise test and PA measurement were performed with and without TP. PA significantly increased after exercise in control (from 51.7+/-23.3% to 64.4+/-27.7%, p < 0.01) and ticlopidine (from 31.9+/-10.5% to 42.0+/-20.4%, p < .01) groups; however, its grade was lower in the ticlopidine group than in the control group. After exercise, PA was lower in the ticlopidine group than in control group (42.0+/-20.4% vs. 64.4+/-27.7%; p < 0.01). In the same patients, PA was lower with TP than without TP after exercise. Treadmill exercise-tolerance time was greater in the ticlopidine group than in the control group, but not statistically significant (762.3+/-139.2 vs. 711.6+/-169.6 s; NS). Exercise-tolerance time was significantly greater with TP than without TP in same patient (791.7+/-98.9 vs. 733.3+/-152.8 s; p < .05). TP suppressed the increase of PA during exercise and increased the exercise-tolerance time in patients with IHD.

Adenosine Diphosphate↗

PubMed1998

Efficacy of oral magnesium administration on decreased exercise tolerance in a state of chronic sleep deprivation.

We have previously reported that chronic sleep deprivation causes a deficiency of intracellular magnesium (Mg) and decreased exercise tolerance. The aim of this study was to clarify whether oral administration of Mg could be effective in restoring the exercise tolerance that is decreased by chronic sleep deprivation. A bicycle ergometer cardiopulmonary exercise test was performed by 16 healthy volunteers (mean age 21.9 years). They were divided into 2 groups: 8 received doses of 100 mg of Mg orally per day for 1 month (Mg group) and the remaining 8 received no Mg and served as the control group. The study conditions were designed as follows: (1) the usual state (good sleep); and (2) the sleep-deprived state (sleeping time up to 60% less than the usual state for 1 month). The ratio of intracellular Mg content of the sleep-deprived state to the usual sleep state was significantly higher in the Mg group (p<0.05) than the untreated control group. There was no difference between the sleep-deprived state and the usual state with regard to anaerobic threshold and peak oxygen uptake in the Mg group, whereas both of these decreased in the sleep-deprived state in the control group. These results indicate that decreased exercise tolerance observed in the sleep-deprived state could be improved by oral Mg administration.

Administration, Oral↗

PubMed1987

A comparison of nine calcium ion antagonists and propranolol: exercise tolerance, heart rate and ST-segment changes in patients with chronic stable angina pectoris.

The effects of nine calcium ion antagonists on exercise tolerance, heart rate and ST-segment changes were compared with those of propranolol in two hundred and eighty patients with established chronic stable angina pectoris. These patients participated in clinical trials for anti-anginal efficacy against placebo, using identical methods and similar protocols, but the comparison reported here was retrospective. The trials were all fixed dose, and the dose was determined by previous upward titration to arrive at an average maximal tolerance level. All the drugs except prenylamine increased the exercise tolerance significantly when compared with placebo. Maximal ST-segment depression on exercise was reduced during treatment with propranolol while treatment with the calcium ion antagonists had no significant effect. The time to the development of 1 mm ST-segment depression was prolonged by all the drugs. Nifedipine, PY-108-068 and nicardipine increased the resting heart rate whereas verapamil, diltiazem, gallopamil, KB-944, prenylamine and tiapamil produced a slight reduction. Propranolol produced a highly significant reduction in the resting and maximal heart rates and the rate-pressure product, whereas gallopamil increased the rate-pressure product by +8% and prenylamine reduced it by -10%. At the doses used, diltiazem, gallopamil and verapamil produced a greater increase in exercise tolerance than did propranolol, while the other drugs were inferior. None of the calcium ion antagonists matched the increase in the time taken to develop 1 mm ST-segment depression with propranolol, although the results with verapamil and gallopamil were close. The calcium ion antagonists are effective antianginal agents which produce their effects by mechanisms which are very different to the beta-adrenoreceptor blocking agents.

Adult↗

PubMed1991

Effects of atenolol, slow-release nifedipine, and their combination on respiratory gas exchange and exercise tolerance in stable effort angina.

The effects of atenolol, nifedipine, and their combination on gas exchange and exercise tolerance were studied in 27 patients with effort angina and normal global ventricular function in an open-label and randomized cross-over trial. Symptom-limited semi-supine exercise tests using a ramp protocol (20 W/min) with simultaneous breath-by-breath analysis of gas exchange were carried out after a 4-day wash-out period and after consecutive 2-week treatment periods with atenolol (50 mg b.i.d.), slow-release nifedipine (20 mg b.i.d.), and their combination (b.i.d.). Exercise tolerance was not significantly higher with atenolol than with nifedipine [118(24) vs 113(23) W]. Combination therapy [120(23) W] was more effective than monotherapy with nifedipine (p less than 0.05) but produced no further increase in exercise tolerance over atenolol monotherapy. Maximum oxygen uptake was not significantly different among the treatments. In the range of light to moderate exercise, the slope of the VO2-workload regression line expressed as ml.min-1.W-1 was lower with atenolol than with nifedipine [8.64(1.59) vs 10.28(1.74), p less than 0.005] and intermediate with combination therapy [9.99(1.83)]. The intercept on the VO2 axis was higher with atenolol than with nifedipine [366(111) vs 299(113) ml.min-1, p less than 0.05]. A similar pattern of results was seen when the drug effects on the slope of the VCO2-workload relation were analyzed. VE was higher with nifedipine than with atenolol at all points of the regression analysis [greater than 30 W].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Thyroid status and exercise tolerance. Cardiovascular and metabolic considerations.

Both hypo- and hyperthyroidism are characterised by exercise intolerance. In hypothyroidism, inadequate cardiovascular support appears to be the principal factor involved. Insufficient skeletal muscle blood flow compromises exercise capacity via reduced oxygen delivery, and endurance through decreased delivery of blood-borne substrates. The latter effect results in increased dependence on intramuscular glycogen. Additionally, decreased mobilisation of free fatty acids from adipose tissue and, consequently, lower plasma free fatty acid levels compound the problem of reduced lipid delivery to active skeletal muscle in the hypothyroid state. In contrast, cardiovascular support is enhanced in hyperthyroidism, implicating other factors in exercise tolerance. Greater reliance on muscle glycogen appears to be the primary reason for decreased endurance. Biochemical changes with hyperthyroidism that would favour enhanced flux through glycolysis may account for this dependence on glycogen. Deviations from normal thyroid function, and the ensuing exercise tolerance, require appropriate medical therapy to attain euthyroid status.

Cardiovascular Physiological Phenomena↗

PubMed1988

The effect of three test meals on exercise tolerance of an individual with McArdle's disease.

This study examined the effect of three test meals on exercise tolerance of an individual with McArdle's disease, a myopathy characterized by phosphorylase b deficiency. The subject's exercise tolerance and ability to achieve the second wind, in response to each test meal, was evaluated over a 16-week period using a bicycle ergometer in a double-blind situation. Data were analyzed using one-way analysis of variance. No significant differences were found. It was concluded that a high protein meal, a high polyunsaturated fat meal, and a meal containing MCT oil did not affect the exercise tolerance of this individual compared to the control meal.

Adult↗

PubMed1996

[Lung function and exercise tolerance in patients with chronic major vessel thromboembolic pulmonary hypertension].

We studied 14 consecutive patients with severe pulmonary hypertension due to chronic major vessel thromboembolic pulmonary hypertension (CPTEH), clinical entity that may be successfully surgically treated by pulmonary thrombendarterectomy. Resting pulmonary mechanics and gas exchange were investigated. Exercise tolerance was studied by 3 different exercise tests. Pulmonary volumes and flows were normal. Some patients presented with decreased lung compliance and reduced diffusion capacity for carbon monoxide. Majority of patients had hypoxaemia and respiratory alkalosis. Exercise tolerance was very limited. In 6 minute walking test patients covered 346 +/- 95 meters. During Bruce test patients completed from 1 to 4 stages. During incremental maximal symptom limited test on cycloergometer patients achieved 56 +/- 18 watts. We concluded that patients with CPTEH present with resting hypoxaemia deteriorating further on exercise and severely limited exercise tolerance.

Adult↗

PubMed2005

Effect of treating depression on quality-of-life and exercise tolerance in severe COPD.

The aim of this study was to determine whether treating concomitant depression improves quality of life and exercise tolerance in COPD patients. Out-patients with moderate to severe, stable COPD completed Hospital Anxiety-Depression (HAD) and General Health questionnaires. A psychiatrist interviewed those with high scores. In a randomised, double-blind fashion, 28 depressed COPD patients took a selective serotonin re-uptake inhibitor, Paroxetine 20 mg daily, or matched placebo for 6 weeks. Subsequently, all patients took un-blinded Paroxetine for 3 months. From these questionnaires, 35% of 135 patients had significant depression, but this was confirmed by psychiatric interview in only 21%. Throughout the study, there were no changes in laboratory lung function nor in home peak flow. Six weeks' treatment produced no significant differences between placebo and treatment group in either depression, quality of life scores or 6-minute walking distances, although overall improvements in depression, correlated with increases in walking distance. Three months of un-blinded treatment, significantly improved depression scores (self-complete HAD, Beck's Depression and psychiatrist-completed Montgomery-Asberg scores), walking distances (369 to 427 m, p = 0.0003) and St. George's Respiratory Questionnaire Total Scores (65 to 58, p = 0.033). Although self-complete questionnaires over-diagnose depression, the condition is nevertheless common in patients with moderately severe COPD. Six weeks of antidepressants is insufficient to improve either depression, quality of life or exercise tolerance. However, our study suggests that a longer course of treatment may be effective and that improvements in depression are associated with improvements in exercise tolerance. A larger, double blind study with a longer treatment period is indicated.

Aged↗

PubMed1982

Exercise tolerance and cardiorespiratory adjustments at peak work capacity in cystic fibrosis.

Exercise tolerance and cardiorespiratory adjustments at peak work capacity (PWC) were determined in 20 patients with cystic fibrosis (CF) during progressive cycle ergometry. The results were related to resting lung function tests, expressed by a pulmonary function score (PFS) that ranged from 0 (no pulmonary dysfunction) to 18 (extreme dysfunction). Patients with CF with no (PFS less than 3), mild (PFS 3-7), or moderate (PFS 8-12) pulmonary dysfunction exercised as well as normal subjects. When the PFS exceeded 12, PWC was reduced on the average by 51%, peak heart rate (PHR) was reduced by 15%, and peak ventilation (PVE) was reduced by 39%. Severely affected patients developed arterial desaturation at PWC (-7.3%), CO2 retention (end-tidal PCO2 + 5 mmHg), and an increase in the PHR/PWC ratio. In most patients with CF the PVE/PWC ratio was elevated, suggestion wasted VE and a probable increase in dead space ventilation. The results indicate that whenever pulmonary disease in CF is advanced, there are decreases in exercise tolerance and cardiorespiratory reserves, exercise-induced ventilation-perfusion abnormalities, arterial desaturation, and alveolar hypoventilation. In view of the abnormal physiological adaptations to exercise in patients with CF with advanced lung disease (PFS greater than 12), they should engage in exercise training programs and strenuous physical activity with caution and only after their cardiorespiratory reserves and adjustments to exercise have been objectively evaluated.

Adolescent↗

PubMedDate not supplied

Cardiac neurosis: exercise tolerance and the role of sympathetic activity.

To evaluate the cardiovascular and plasma catecholamine responses to dynamic exercise in patients with cardiac neurosis (CN), treadmill testing was performed. Thirty-four patients with CN were chosen for this study based on exercise tolerance and the results were compared with those in 31 patients with organic heart disease and 12 normal subjects. Patients with CN showed an augmentation of cardiovascular and plasma catecholamine responses. The augmentation of the norepinephrine response in patients with CN was not as remarkable as that in patients with organic heart disease. On the other hand, the augmentation of the epinephrine response was greater in patients with CN than in those with organic heart disease. Administration of metoprolol (40 mg/day) for two weeks improved exercise tolerance in patients with CN. We suggest that anxiety augments both sympatho-neural and sympatho-adrenal activity and that it is the symptoms induced by the augmented cardiovascular response which reduce exercise tolerance in patients with CN.

Adult↗

PubMed2001

Enhanced ventilatory response to exercise in patients with chronic heart failure and preserved exercise tolerance: marker of abnormal cardiorespiratory reflex control and predictor of poor prognosis.

BACKGROUND: In patients with chronic heart failure (CHF) and preserved exercise tolerance, the value of cardiopulmonary exercise testing for risk stratification is not known. Elevated slope of ventilatory response to exercise (VE/VCO(2)) predicts poor prognosis in advanced CHF. Derangement of cardiopulmonary reflexes may trigger exercise hyperpnea. We assessed the relationship between cardiopulmonary reflexes and VE/VCO(2)and investigated the prognostic value of (VE/VCO(2)) in CHF patients with preserved exercise tolerance. METHODS AND RESULTS: Among 344 consecutive CHF patients, we identified 123 with preserved exercise capacity, defined as a peak oxygen consumption (PEAK VO(2)) >/=18 mL. kg(-1). min(-1) (age 56 years; left ventricular ejection fraction 28%; peak VO(2) 23.5 mL. kg(-1). min(-1)). Hypoxic and hypercapnic chemosensitivity (n=38), heart rate variability (n=34), baroreflex sensitivity (n=20), and ergoreflex activity (n=20) were also assessed. We identified 40 patients (33%) with high VE/VCO(2) (ie, >34.0). During follow-up (49+/-22 months, >3 years in all survivors), 34 patients died (3-year survival 81%). High VE/VCO(2) (hazard ratio 4.3, P<0.0001) but not peak f1.gif" BORDER="0">O(2) (P=0.7) predicted mortality. In patients with high VE/VCO(2), 3-year survival was 57%, compared with 93% in patients with normal VE/VCO(2) P<0.0001). Patients with high VE/VCO(2) demonstrated impaired reflex control, as evidenced by augmented peripheral (P=0.01) and central (P=0.0006) chemosensitivity, depressed low-frequency component of heart rate variability (P<0.0001) and baroreflex sensitivity (P=0.03), and overactive ergoreceptors (P=0.003) compared with patients with normal VE/VCO(2). CONCLUSIONS: In CHF patients with preserved exercise capacity, enhanced ventilatory response to exercise is a simple marker of a widespread derangement of cardiovascular reflex control; it predicts poor prognosis, which VO(2) does not.

Chronic Disease↗

PubMed1995

Oxygen deficit during exercise testing in heart failure. Relation to submaximal exercise tolerance.

Measurements of oxygen deficit during submaximal exercise were correlated with the anaerobic threshold (as measured by gas exchange analysis), peak work rate on a ramp protocol, and the ability to perform constant work rate exercise in 10 male patients with New York Heart Association class 2 congestive heart failure and 12 age- and gender-matched normal controls. All subjects performed a maximal ramp exercise test for measurement of the anaerobic threshold. In addition, several 15-min constant work rate exercise sessions were conducted to evaluate oxygen deficit, measured as the area between the "ideal" square curve of oxygen consumption at the onset of constant work rate exercise and the actual exponentially shaped curve. Since the oxygen deficit significantly correlated with the plateau oxygen consumption during the 25-W constant work rate exercise (r = 0.61, p = 0.002), the oxygen deficit was normalized by the rectangular area of 15-min oxygen consumption above baseline. This normalized value significantly correlated with the inverse of the anaerobic threshold (r = 0.81, p < 0.0001). The logarithm of the normalized oxygen deficit significantly correlated with the maximum ramp work rate (r = -0.86, p < 0.0001) and the highest constant work rate sustained for 15 min (r = -0.82, p < 0.0001). In addition, the time to reach plateau oxygen consumption for the 25-W exercise significantly correlated with the inverse of the anaerobic threshold (r = -0.78, p < 0.0001), the maximum ramp work rate (r = -0.76, p < 0.0001), and the highest constant work rate sustained for 15 min (r = -0.74, p < 0.0001). Thus, the oxygen deficit seen in patients with heart failure during constant work rate exercise results from abnormally slow oxygen uptake kinetics and correlates with exercise capacity as measured by anaerobic threshold (via gas exchange analysis) and maximal and submaximal exercise tolerance. Oxygen deficit warrants further evaluation as a submaximal index of functional capacity in patients with heart failure.

Adult↗

PubMed2003

Effects of an early invasive strategy on ischemia and exercise tolerance among patients with unstable coronary artery disease.

BACKGROUND: An early invasive approach after an episode of unstable coronary artery disease has beneficial effects on mortality and myocardial infarction, but its effects on exercise capacity and ischemia have not been investigated. METHODS: In the Fast Revascularisation during InStability in Coronary disease (FRISC) II trial, 2457 patients with unstable coronary artery disease were assigned randomly to an early invasive or noninvasive strategy. A symptom-limited bicycle exercise test was performed before discharge in the noninvasive group and after 3 months in both groups. RESULTS: At 3 months, 86% (1046/1222) of the patients in the invasive group and 81% (995/1235) in the noninvasive group performed the exercise test. Before the test, revascularization had been performed in 78% (n = 819) of these patients in the invasive group compared with 28% (n = 281) of those in the noninvasive group. The mean (+/- SD) exercise capacity was higher (6.4 +/- 1.9 vs. 6.2 +/- 1.9 metabolic equivalents [METS], P <0.01), and the occurrence of ischemia lower (23% [229/1004] vs. 36% [352/966], P <0.001) in the invasive group. In the noninvasive group, 882 patients performed an exercise test both predischarge and at 3 months. If a revascularization procedure was performed (n = 210), exercise tolerance increased from 5.1 +/- 1.4 to 6.0 +/- 1.8 METS (P <0.001) and the number of patients with ST depression decreased from 65% (131/203) to 31% (63/203) (P <0.001). Without revascularization (n = 670), exercise tolerance increased from 5.9 +/- 2.2 to 6.3 +/- 1.9 METS (P <0.001), and there were no differences in the occurrence of ischemia. CONCLUSION: In unstable coronary artery disease, an invasive strategy improves exercise tolerance and reduces exercise-induced ischemia.

Angina, Unstable↗

PubMed1996

Contribution of peripheral chemoreceptors to ventilation and the effects of their suppression on exercise tolerance in chronic heart failure.

OBJECTIVES: To assess the contribution of peripheral chemoreceptors to ventilation and the effects of continuous inspired oxygen on exercise tolerance in chronic heart failure patients. The role of peripheral chemoreceptors in mediating hyperpnoea in chronic heart failure is unknown. Hyperoxia is known to suppress the peripheral chemoreceptor drive. The magnitude of decrease in ventilation with transient inhalations of oxygen thus provides a measure of the contribution of the peripheral chemoreceptors to ventilation. SETTING: Tertiary specialist hospital. SUBJECTS AND METHODS: Three breaths of 100% oxygen were given at rest and also during cycle ergometry at 25 W to 8 healthy controls (age 52.0 (4.7) (SEM) years) and 13 patients with chronic heart failure (age 60.5 (2.1) years (P = NS); radionuclide left ventricular ejection fraction 25.5 (4.3)%). The peripheral chemoreceptor sensitivity was also measured by assessing the ventilatory response to hypoxia using transient inhalations of pure nitrogen. Another group of 12 patients with chronic heart failure (age 65.5 (1.5) years; left ventricular ejection fraction 21.3 (3.0)%) underwent treadmill exercise testing on 2 occasions, breathing air or 100% oxygen in a randomised single-blind manner, to examine the effects of continuous inspired oxygen on exercise tolerance. RESULTS: The reduction in ventilation with transient hyperoxia was 18.1 (2.9)% v 17.9 (2.6)% (P = NS) at rest and 20.4 (2.8)% v 21.0 (1.6)% (P = NS) during cycle ergometry, for controls and patients respectively. The hypoxic chemosensitivity was higher in patients (0.232 (0.022) v 0.572 (0.082) 1/min/%SaO2; P = 0.002). Continuous inspired oxygen increased exercise time (517 (31) v 455 (27) seconds; P = 0.003), and a trend towards a reduction in the ventilatory response to exercise, characterised by the regression slope relating ventilation to carbon dioxide output, was evident (31.27 (2.60) v 34.19 (2.35); P = 0.08). CONCLUSIONS: Despite an increased peripheral chemoreceptor sensitivity, the proportionate contribution of peripheral chemoreceptors to ventilation remained similar in heart failure patients (about 20%). This suggests that the peripheral chemoreceptors are not the main mediator of increased ventilation and there are other non-peripheral chemoreceptor-mediated mechanisms involved. Hyperoxia reduced ventilation at rest and during cycle ergometry. The increase in exercise duration with continuous inspired oxygen that was associated with a reduction in exercise ventilatory response suggests that suppression of the peripheral chemoreceptors may improve exercise tolerance; the effects of possible reduced skeletal muscle anaerobiosis cannot be excluded, however.

Chemoreceptor Cells↗