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Results for “Exercise Tolerance”

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PubMed1988

Left ventricular dysfunction, exercise capacity and activity recommendations.

There is lack of consistent correlation between left ventricular function at rest, haemodynamic measurements at rest, symptomatic status and exercise tolerance. Haemodynamic data appear comparable in patients whose exercise tolerance is limited clinically by fatigue and by breathlessness. Selected patients with left ventricular dysfunction and compensated congestive heart failure can safely undergo both exercise testing and training, and an improvement in functional status can be anticipated to result from exercise training.

Cardiomegaly↗

PubMed1999

Smoking-induced elevations in blood carboxyhaemoglobin levels. Effect on maximal oxygen uptake.

Many people engage in physical activity to reduce their cardiovascular risk associated with smoking. These people should be made aware of the metabolic and cardiorespiratory changes induced by chronic and acute smoking and, in particular, the exercise ramifications of increased levels of blood carbon monoxide (CO). Smoking-induced elevations in the CO content of the blood can reduce exercise tolerance and maximal aerobic capacity. Smoking also increases the reliance upon glycolytic metabolism during exercise. Together, these factors contribute to earlier fatigue in smokers compared with nonsmokers who exercise. Similar effects upon exercise tolerance are noted in those who inhale environmental tobacco smoke.

Carboxyhemoglobin↗

PubMed1985

Long-term oral administration of amrinone for congestive heart failure: lack of efficacy in a multicenter controlled trial.

A number of uncontrolled studies have indicated that oral administration of amrinone, a phosphodiesterase inhibitor with potent positive inotropic effects in experimental preparations, may be beneficial in patients with chronic congestive heart failure. The present multicenter trial was designed to prospectively evaluate clinical response and change in exercise tolerance during 12 weeks of amrinone therapy in a double-blind, placebo-controlled protocol. Ninety-nine patients with NYHA functional class 3 or 4 congestive heart failure on digitalis and diuretics, of whom 31 were also receiving captopril, were enrolled. After baseline clinical assessment and determination of exercise tolerance, radionuclide left ventricular ejection fraction, and roentgenographic cardiothoracic ratio, patients were randomly assigned to receive amrinone or placebo, beginning at 1.5 mg/kg tid and increasing to a maximum dosage of 200 mg tid. After 12 weeks of therapy or at the last blinded evaluation in patients who did not complete this protocol, there were no significant differences from baseline values between treatment with amrinone or placebo with regard to symptoms, NYHA functional class, left ventricular ejection fraction, cardiothoracic ratio, frequency and severity of ventricular ectopy, or mortality. Exercise tolerance improved significantly from baseline by 37 +/- 10% (mean 163 sec) in patients on amrinone and 35 +/- 11% (mean 149 sec) in patients on placebo, but there was no significant difference between treatments. Adverse reactions were significantly more frequent and more severe on amrinone, occurring in 83% of patients and necessitating withdrawal in 34%.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed2006

Results of one-year anticoagulation in patients with newly detected chronic thromboembolic pulmonary hypertension not treated with pulmonary endarterectomy.

INTRODUCTION: Currently pulmonary endarterectomy is considered the method of choice in patients with chronic thromboembolic pulmonary hypertension (CTEPH). It is not known if this option should be recommended in all suitable patients as it is highly variable with respect to prognosis. There is also doubt about selection of adequate time to refer patients with CTEPH for surgery. AIM: To establish whether some patients with CTEPH may clinically benefit from isolated anticoagulation with drugs and if the use of anticoagulation may have any impact on the time of patient referral for pulmonary endarterectomy. METHODS: The prospective analysis involved 29 patients (9 male, 20 female) aged 37 to 82 years, with pulmonary arterial systolic pressure ranging from 39 to 133 mmHg and newly diagnosed CTEPH who had not been treated with pulmonary endarterectomy and were not receiving anticoagulation. Survival, functional status according to NYHA classification, duration of thromboembolism, exercise tolerance and echocardiographic parameters of right ventricular overload before and at one year after initiation of therapy with anticoagulants were evaluated. RESULTS: During follow-up, 3 patients with PASP ranging from 120 to 133 mmHg died. In 26 patients with PASP 39-115 mmHg, who survived, improvement in echocardiographic parameters of right ventricular overload, better exercise tolerance as well as functional status according to NYHA classification was observed. In 12 survivors, pulmonary pressure returned to normal. CONCLUSIONS: The results of this study suggest that favourable effects of isolated anticoagulation are likely in patients with newly detected CTEPH, mild and moderate baseline pulmonary hypertension and acceptable exercise tolerance. They also indicate the necessity of anticoagulation in these patients prior to possible referral for pulmonary endarterectomy.

Acenocoumarol↗

PubMed1994

Fatty acid exercise scintigraphy after percutaneous transluminal coronary angioplasty.

We performed a sequential fatty acid exercise-rest scintigraphy in 18 patients with an initially successful percutaneous transluminal coronary angioplasty (PTCA) to study the concordance of trends in symptoms, exercise tolerance and myocardial metabolism. Eleven patients stopped the exercise because of angina pectoris in the preoperative test; 2 days after PTCA this number decreased to two, but again increased to eight 3 months later. Exercise time (9.7 +/- 0.6 min, mean +/- SEM) and maximum exercise heart rate (128 +/- 4 beats min-1) were at least as good immediately after the operation as originally (8.8 +/- 0.6 min and 121 +/- 4 beats min-1, respectively). After 3 months both parameters were significantly (P < 0.05) better (10.3 +/- 0.6 min and 136 +/- 4 beats min-1, respectively) than originally. Some relative improvement in washout was noticed in 61% 2 days and in 56% of cases 3 months after PTCA. Fatty acid exercise uptake was more homogeneous in 72% of cases immediately after angioplasty and in 44% 3 months later. The trend in fatty acid uptake, exercise characteristics, and also in symptoms was most favourable among the eight patients with a dilatated left anterior descending coronary artery. Although the gamma camera technique possibly underestimated the effects of angioplasty, the impaired fatty acid metabolism could be linked with persistent symptoms after the operation. We conclude that most patients can safely participate in a symptom-limited (maximal) ergometry test already 2 days after PTCA, and that postoperatively myocardial perfusion and metabolism improve rapidly. However, this advantage is eventually lost to some degree, even if exercise tolerance continues to improve.

Adult↗

PubMed1991

[Fitness for swimming after myocardial infarct].

Standardized telemetry during swimming and blood pressure monitoring were performed on 25 consecutive patients (22 men and 3 women: mean age 59 +/- 7 years) after myocardial infarction, sustained on average 28 +/- 26 months ago. Mean exercise tolerance, as judged by symptoms during bicycle ergometry, was 1.31 +/- 0.5 W/kg (pulse limit 117 +/- 21 beats/min). The swimming test had to be discontinued in six patients because of severe arrhythmias, in two because of severe angina. Seven patients completed the full swimming distance, but were also considered unsuitable for swimming because of moderate angina and dyspnoea. Ten patients proved to be fit for swimming. Their average ergometrically determined exercise tolerance (1.27 +/- 0.51 W/kg, pulse limit 114 +/- 16 beats/min) was not different from that of unfit patients (1.34 +/- 0.50 W/kg; 119 +/- 24 beats/min). During swimming the unfit patients had a significantly higher heart rate and blood pressure rise than the fit ones. Only in the unfit patients the exercise tolerance limit determined by bicycle ergometry was exceeded during swimming. This indicates that postinfarction patients should undergo swimming telemetry before declared fit for swimming.

Angina Pectoris↗

PubMed1988

Effect of vasodilator and inotropic drugs on clinical symptoms and long-term survival in chronic congestive heart failure.

The major therapeutic goals in the treatment of congestive heart failure are the relief of symptoms and the prolongation of life, but it remains unclear whether there is a relation between changes in exercise tolerance and alterations in the risk of death. Although all vasodilator and inotropic agents produce short-term haemodynamic benefits, these acute effects do not predict the long-term clinical responses to these drugs. Converting-enzyme inhibitors appear to improve symptoms and survival. A combination of hydralazine and isosorbide dinitrate produces variable effects on exercise tolerance but appears to prolong life. Catecholamines and phosphodiesterase inhibitors may reduce dyspnea and fatigue but adversely affect mortality. Calcium channel blocking drugs may exert deleterious effects on both symptoms and prognosis. alpha-Adrenergic blocking drugs produce no beneficial or adverse effects on clinical status or mortality. Hence, there is no consistent relation between the symptomatic and prognostic effects of drug therapy in patients with chronic heart failure. This variability makes it impossible to predict the effects of any drug on exercise tolerance or survival based on an evaluation of the agent's short-term haemodynamic effects.

Adrenergic alpha-Antagonists↗

PubMed1991

Maximum intensity exercise training in patients with chronic obstructive pulmonary disease.

We studied high intensity, symptom-limited, endurance exercise training in 52 patients with COPD participating in a pulmonary rehabilitation program. The patients had moderate to severe airway obstruction and reduced exercise tolerance with ventilatory limitation. The target workload for endurance exercise testing was 95 percent of the baseline maximum treadmill work load. At training weeks 1, 4 and 8, they were training at 85, 84, and 86 percent respectively, of baseline maximum. After rehabilitation, there was an increase in maximal treadmill work load, VO2max, and endurance exercise time, and a decrease in perceived symptoms. Patients who did not reach anaerobic threshold (group 2) were able to train at a higher percentage of maximum exercise tolerance than patients who reached anaerobic threshold (group 1). The increase in exercise performance of both groups, however, was similar. We conclude that patients with moderate to severe COPD can perform exercise training successfully at intensity targets which represent higher percentages of maximum than typically recommended in normal individuals or other patients.

Anaerobic Threshold↗

PubMed1984

Lack of relationship between the short-term hemodynamic effects of captopril and subsequent clinical responses.

The role of hemodynamic monitoring during the initiation of vasodilator therapy for heart failure remains to be defined, despite the tremendous potential socioeconomic and clinical ramifications. We therefore performed resting and exercise hemodynamic studies before and during the initial 48 hr of captopril therapy in 14 stable patients with New York Heart Association Class II or III chronic congestive heart failure. Their clinical response to therapy was determined by evaluating changes in clinical status and the measured changes in exercise tolerance, heart size, and ejection fraction after 3 months. Significant improvement in each of these indexes was found for the group as a whole, but the baseline hemodynamics and the hemodynamic responses to captopril differed little between the patients showing marked improvement and those exhibiting little or no change. Correlations between the hemodynamic measurements and the changes in clinical class, exercise tolerance, heart size, and ejection fraction were generally poor. Even when they achieved significance, these correlations were too loose to allow prediction of the clinical efficacy of captopril in individual subjects. These findings indicate that the routine use of invasive hemodynamic monitoring during the initiation of captopril is unnecessary and potentially misleading, although such measurements remain valuable for diagnosis, the management of patients with complex conditions, and for investigation. The response to captopril may be best evaluated by serial measurements of exercise tolerance and heart size in addition to clinical assessment.

Aged↗

PubMed2001

Detection of changes in diastolic function by pulmonary venous flow analysis in women athletes.

BACKGROUND: Left ventricular cavity dimension, wall thickness, relaxation, and filling increase with exercise training and have a role in enhancing physical performance. We probed whether changes in diastole may develop separately from those in cardiac morphometry and still contribute to improve physical performance. Challenging diastole by preload reduction with standing and integrating mitral flow analysis with the pulmonary venous flow analysis were viewed as a means for detecting fine diastolic variations. METHODS: Patterns of mitral, tricuspid, and pulmonary venous flow were evaluated by echo Doppler imaging in the supine and standing positions in 11 long-distance runner women athletes participating in training programs and having no or very mild cardiac morphologic alterations and were compared with those in 11 healthy women active in daily life not participating in training programs. Maximal exercise tolerance was tested in both groups with a treadmill with use of the standard Bruce protocol. RESULTS: Echocardiographic left ventricular mass index and mitral and pulmonary flow patterns in athletes and controls were similar while they were supine. Major (P<.01) percent variations and differences between athletes and controls with standing were smaller decrease in right (-12% +/- 5% vs -29% +/- 5%) and left ventricular (-3% +/- 1% vs -9% +/- 2%) dimensions and stroke volume (-7% +/- 4% vs -23% +/- 4%), smaller lengthening of early mitral deceleration (+7% +/- 4% vs +18% +/- 5%), and isovolumic relaxation (-3% +/- 5% vs +15% +/- 7%) times. Athletes showed greater reduction in pulmonary S wave peak velocity (-25% +/- 10% vs -12.5% +/- 7%) and time velocity integral (Si) (-50% +/- 9% vs -21% +/- 8%), greater increases in pulmonary venous diastolic (D) wave peak velocity(+20% +/- 9% vs +12% +/- 10%, meters per second), and time velocity integral (Di) (+81% +/- 16% vs +27% +/- 14%) and greater decrease of S/D(-30% +/- 6% vs -18% +/- 5%) and Si/Di (-70% +/- 10% vs -33% +/- 5%) ratios. At multivariate analysis standing Si/Di was the strongest independent predictor of better exercise tolerance (peak exercise time 1035 +/- 88 sec in athletes, 751 +/- 20 in controls). CONCLUSIONS: Pulmonary flow analysis in athletes while standing can detect changes in diastolic function that are dissociated from apparent left ventricular morphologic alterations, are undetected in the supine position, and may, in part, determine exercise performance.

Adult↗

PubMed2001

Muscle ergoreceptor overactivity reflects deterioration in clinical status and cardiorespiratory reflex control in chronic heart failure.

BACKGROUND: In chronic heart failure (CHF), overactivation of ergoreceptors (afferents sensitive to the metabolic effects of muscular work) may be a link between peripheral changes, sympathetic overactivation, and increased hemodynamic and ventilatory responses to exercise. The relationship between ergoreceptors, autonomic changes, and the progression of the syndrome has not yet been studied. METHODS AND RESULTS: Thirty-eight stable CHF patients (age, 57+/-1 years; ejection fraction, 26+/-2%) were compared with 12 age-matched normal control subjects. The ergoreflex contribution to the ventilatory and hemodynamic responses to exercise, together with peripheral and central chemoreceptor sensitivity, arterial baroreflex sensitivity, plasma norepinephrine, epinephrine, and heart rate variability, were measured. Enhanced ergoreflex effects on ventilation (78+/-2% versus 50+/-8%), peripheral chemosensitivity (0.6+/-0.4 versus 0.2+/-0.1 L/min per percent SaO(2)), and central chemosensitivity (2.9+/-0.2 versus 2.0+/-0.2 L. min(-1). mm Hg(-1)) and an impaired baroreflex function (4.1+/-0.6 versus 9.1+/-5.6 ms/mm Hg) were confirmed in CHF compared with control subjects (P<0.01 in all comparisons). Ergoreceptor overactivity was associated with a worse symptomatic state (NYHA class, P<0.05), lower exercise tolerance (peak VO(2), P<0.05), and pronounced exercise hyperventilation (VE/VCO(2), P<0.01). It was also a strong predictor of increased central chemosensitivity (independently of clinical parameters), baroreflex impairment, and sympathetic activation (plasma catecholamines and heart rate variability indexes; all P<0.05). In multivariate analysis, among all reflexes studied, the ventilatory component of the ergoreflex was the only independent predictor of peak VO(2) and VE/VCO(2). CONCLUSIONS: In CHF, overactivation of the ergoreflex is associated with abnormal cardiorespiratory reflex control, independently of clinical severity. Among impaired reflexes, overactivation of the ergoreflex is an important determinant of exercise hyperventilation and reduced exercise tolerance.

Autonomic Nervous System↗

PubMed1989

Beneficial effects of low dose amiodarone in patients with congestive cardiac failure: a placebo-controlled trial.

The effects of amiodarone in a low dosage (200 mg every 8 h for 2 weeks, then 200 mg/day) was assessed in a double-blind placebo-controlled trial in 34 patients with a history of severe congestive heart failure but no sustained ventricular arrhythmia. Left ventricular ejection fraction, treadmill exercise tolerance and 48 h electrocardiographic monitoring were assessed before and repeatedly after beginning amiodarone or placebo therapy over 6 months, and side effects were monitored. In patients receiving amiodarone, the ejection fraction increased significantly from 19 +/- 7 to 29 +/- 15% at 6 months (p less than 0.01 from baseline), but not significantly in 14 placebo-treated patients (18 +/- 5 to 22 +/- 9%). Exercise tolerance increased significantly in amiodarone-treated patients (median 433 s to 907 s, p less than 0.05), but not significantly in placebo-treated patients (757 to 918 s). Nonsustained ventricular tachycardia was present in 88% of amiodarone-treated patients before, but in only 21% of patients after 6 months of treatment (p = 0.06); it was seen in 43% of placebo-treated patients at baseline and in 50% after 6 months. Fifty percent of amiodarone-treated patients had side effects (principally nausea) and the drug was withdrawn in 28% of cases; no life-threatening effects were seen. Low dose amiodarone appears to have a multifaceted potential to produce benefits in arrhythmia control, exercise tolerance and ventricular function in patients with a history of severe congestive heart failure, but better control of side effects (principally nausea) appears essential. Effects on mortality could not be determined from this study; such assessment requires a larger cohort of patients.

Aged↗

PubMed1996

The six-minute walking test in children with cystic fibrosis: reliability and validity.

There is a need to judge general exercise tolerance in children with cystic fibrosis (CF) under normal daily activity conditions and -when more extensive testing is required-in an exercise laboratory in a specialized center. We investigated the reproducibility, validity, and criterion for a 6-minute walking test, which simulates normal childhood activities. In Part A, we evaluated the reproducibility of a 6-minute walking test in 23 children (12 girls and 11 boys; ages 11.1 +/- 2.2 years; range, 8.2 15.6 years) with mild symptoms of CF [forced expiratory volume in 1 second (FEV1) 94.4 +/- 16.5% of predicted values (range, 60.6-129.7); body weight Z-score -0.71 +/- 0.81 (range, -1.73-0.93)]. The subjects performed two standardized 6-minute walking tests with 1 week between tests. There was no significant difference between the two walking distances reached (737 +/- 85 versus 742 +/- 90 meters; P = 0.56), and there was a strong correlation between the two walking distances reached by the individuals (r = 0.90, P < 0.0001). In Part B, the validity of the walking test was evaluated in 15 children (6 girls and 9 boys; ages 14.5 +/- 2.0 years; range, 10.2-16.9 years) with moderate symptoms of CF [FEV1 = 58 +/- 16.0% of predicted values, (range, 41.1-89.4); RV/TLC ratio = 46.3 +/- 6.5% (range, 31.6-57.2); body weight Z-score: -1.29 +/- 0.60 (range, -2.20-0.14)]. They underwent standardized maximum incremental exercise testing on a cycle ergometer and a 6-minute walking test. Postexertional lactate values exceeded threshold values (as described in the literature) in all patients but one. Correlation analysis (Pearson) showed a significant correlation between the walking distance reached (WD = 697 +/- 104 meters), and the maximum workload (Wmax = 118 +/- 44 watt; r = 0.76, P < 0.001) or the maximum oxygen uptake (1,688 +/- 495 ml; r = 0.76, P < 0.001), the latter two being determined on a cycle ergometer, RV/TLC% showed a significant negative correlation (r = -0.72, P < 0.01) with WD. Stepwise multiple regression analysis showed a multiple regression coefficient of R = 0.84 (P < 0.001) for Wmax and RV/TLC % as the independent variables vs. WD as the dependent variable. We conclude that the 6-minute walking test is a valid and useful test in children with mild to moderate symptoms of CF to assess their exercise tolerance and endurance. Exercise test results correlated negatively with pulmonary hyperinflation expressed by the RV/TLC ratio.

Adolescent↗

PubMed1998

Withdrawal effects of antianginal therapy: comparison of isosorbide dinitrate and nifedipine.

We compared the effects of abrupt cessation of nifedipine and isosorbide dinitrate therapy in patients with stable angina pectoris. Eighteen males were studied. Each patient received isosorbide dinitrate and nifedipine continuously for 5 weeks by randomised cross-over technique. Exercise treadmill tests were performed before each treatment period, at the beginning of treatment, 4 weeks after initiation of treatment and on the first and eighth days of drug withdrawal. At the end of treatment the antianginal effect of both agents attenuated (versus acute administration). Abrupt cessation of isosorbide dinitrate caused only a tendency towards decrease in exercise tolerance versus pre-treatment level. Alternatively, abrupt cessation of nifedipine resulted in substantial deterioration in exercise tolerance, which was statistically significant 21 and 24 h after the last dose administration. The number of anginal attacks increased >25% in two patients after cessation of isosorbide dinitrate and in eight patients after cessation of nifedipine. In no patient rest angina episodes appeared after stopping of isosorbide dinitrate, however, after stopping of nifedipine rest angina episodes appeared in three patients. We conclude that withdrawal phenomenon of nifedipine is much more pronounced than that of isosorbide dinitrate and may emerge on the first day of drug cessation. Such a phenomenon may be evident even in patients in whom nifedipine effect have attenuated due to the development of tolerance.

Adult↗

PubMed1978

Ventricular tachycardia due to cardiac ischaemia: assessment by exercise electrocardiography.

Although ventricular tachycardia is a well-known complication of myocardial ischaemia and may be provoked by exercise, many patients may appreciate only the angina and be unaware of the unduly rapid heart rate that precipitates it. Exercise testing is needed to show this arrhythmia and to enable treatment to be started.Twenty-three patients were found to have chronic ischaemic heart disease complicated by ventricular tachycardia. Six patients with old myocardial infarction had ventricular tachycardia at rest which required conversion to sinus rhythm; 17 patients developed ventricular tachycardia only when they exercised. In 12 of these 17 patients coronary angiography showed disease of the anterior descending branch of the left coronary artery; other vessels were usually also affected. Although beta-adrenergic blocking drugs increased exercise tolerance, ventricular tachycardia still occurred when the heart rate on exercise reached a level similar to that before treatment. In five patients coronary artery bypass surgery was performed because of angina and exercise-induced ventricular tachycardia. Exercise tolerance was increased in all three patients who underwent exercise tests after operation, and in two of these patients, both of whom were known to have patent grafts, ventricular tachycardia was abolished.If part of the beneficial effect of coronary bypass surgery is preventing life-threatening ventricular arrhythmias it is essential to detect these, and ambulatory monitoring and stress testing have a complementary role.

Adult↗

PubMed2000

Use of nitric oxide inhalation in chronic obstructive pulmonary disease.

BACKGROUND: Inhalation of nitric oxide with oxygen could be a promising treatment in patients with chronic obstructive pulmonary disease (COPD) and pulmonary hypertension. However, the current methods of delivery of NO are cumbersome and unsuitable for long term use. The present study was undertaken to investigate the safety and efficacy of a mixture of nitric oxide (NO) and oxygen administered via a nasal cannula for 24 hours in patients with oxygen dependent COPD. METHODS: Twenty five parts per million (ppm) of NO was administered by inhalation combined with supplemental oxygen at a flow rate of 2 l/min via a nasal cannula for 24 hours to 11 ambulatory men with stable, oxygen dependent COPD. Room air with supplemental oxygen at 2 l/min was administered in an identical manner for another 24 hours as control therapy in a randomised, double blind, crossover fashion to all patients. Pulmonary function tests, exercise tolerance, dyspnoea grade, and lung volumes were measured at baseline, 24, and 48 hours. Pulmonary artery pressure (PAP), cardiac output (CO), pulmonary vascular resistance (PVR), arterial blood gas tensions, and minute ventilation were measured at baseline, after 30 minutes and 24 hours of breathing NO and oxygen. Venous admixture ratio (Qs/Qt) and dead space ratio (Vd/Vt) were also calculated. Concentrations of nitrogen dioxide (NO(2)) and NO in the inhaled and ambient air were monitored continuously. Differences in pulmonary function, arterial blood gas tensions, pulmonary haemodynamics, exercise tolerance, and dyspnoea between oxygen and NO breathing periods were analysed for significance using paired t tests. RESULTS: A significant (p<0.05) fall was observed in PVR (183.1 (116.05) and 137.2 (108.4) dynes.s.cm(-3) before and after breathing NO for 24 hours, respectively) with NO administration without significant changes in symptoms, pulmonary function, arterial oxygen tension, or exercise tolerance. CONCLUSIONS: NO at a concentration of 25 ppm blended with oxygen can be safely administered by nasal cannula for 24 hours without significant adverse effects and lowers PVR in stable patients with COPD receiving long term oxygen therapy.

Administration, Inhalation↗

PubMed1986

Bedrest-induced peak VO2 reduction associated with age, gender, and aerobic capacity.

To compare the factors of age and gender on aerobic work capacity following bedrest-induced deconditioning, peak oxygen uptake (peak VO2), heart rate (peak HR), and exercise tolerance time were measured in 15 middle-aged men (55 +/- 2 yr) and 17 middle-aged women (55 +/- 1 yr) before and after 10 d of continuous bedrest (BR). The average body weight following BR was unchanged in both men and women. Following BR, peak VO2 decreased from 35.6 +/- 2.0 to 32.6 +/- 1.1 ml . kg-1 . min-1 (-8.4%, p less than 0.05) in the men and from 26.5 +/- 1.4 to 24.7 +/- 1.3 ml . kg-1 . min-1 (-6.8%, p less than 0.05) in the women, while total exercise tolerance time was reduced by 8.1% (p less than 0.05) and 7.3% (p less than 0.05) in the men and women, respectively. The peak HR was elevated by BR from 158 +/- 4 to 165 +/- 4 bpm (+4.4%, p less than 0.05) in the men and from 157 +/- 4 to 159 +/- 4 bpm (+1.3%, NS) in the women. The percent changes in peak VO2, peak HR, and exercise tolerance time measured in the men were not significantly different compared to those of the women. The reduction in peak VO2 in the middle-aged men and women in the present study were comparable to the reductions of 9.3% and 7.8% observed in our earlier studies with 15 young men (21 +/- 1 yr) and 8 young women (28 +/- 2 yr), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed2004

Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest base camp: a randomized, double-blind, placebo-controlled crossover trial.

BACKGROUND: Alveolar hypoxia causes pulmonary hypertension and enhanced right ventricular afterload, which may impair exercise tolerance. The phosphodiesterase-5 inhibitor sildenafil has been reported to cause pulmonary vasodilatation. OBJECTIVE: To investigate the effects of sildenafil on exercise capacity under conditions of hypoxic pulmonary hypertension. DESIGN: Randomized, double-blind, placebo-controlled crossover study. SETTING: University Hospital Giessen, Giessen, Germany, and the base camp on Mount Everest. PARTICIPANTS: 14 healthy mountaineers and trekkers. MEASUREMENTS: Systolic pulmonary artery pressure, cardiac output, and peripheral arterial oxygen saturation at rest and during assessment of maximum exercise capacity on cycle ergometry 1) while breathing a hypoxic gas mixture with 10% fraction of inspired oxygen at low altitude (Giessen) and 2) at high altitude (the Mount Everest base camp). INTERVENTION: Oral sildenafil, 50 mg, or placebo. RESULTS: At low altitude, acute hypoxia reduced arterial oxygen saturation to 72.0% (95% CI, 66.5% to 77.5%) at rest and 60.8% (CI, 56.0% to 64.5%) at maximum exercise capacity. Systolic pulmonary artery pressure increased from 30.5 mm Hg (CI, 26.0 to 35.0 mm Hg) at rest to 42.9 mm Hg (CI, 35.6 to 53.5 mm Hg) during exercise in participants taking placebo. Sildenafil, 50 mg, significantly increased arterial oxygen saturation during exercise (P = 0.005) and reduced systolic pulmonary artery pressure at rest (P < 0.001) and during exercise (P = 0.031). Of note, sildenafil increased maximum workload (172.5 W [CI, 147.5 to 200.0 W]) vs. 130.6 W [CI, 108.8 to 150.0 W]); P < 0.001) and maximum cardiac output (P < 0.001) compared with placebo. At high altitude, sildenafil had no effect on arterial oxygen saturation at rest and during exercise compared with placebo. However, sildenafil reduced systolic pulmonary artery pressure at rest (P = 0.003) and during exercise (P = 0.021) and increased maximum workload (P = 0.002) and cardiac output (P = 0.015). At high altitude, sildenafil exacerbated existing headache in 2 participants. LIMITATIONS: The study did not examine the effects of sildenafil on normoxic exercise tolerance. CONCLUSIONS: Sildenafil reduces hypoxic pulmonary hypertension at rest and during exercise while maintaining gas exchange and systemic blood pressure. To the authors' knowledge, sildenafil is the first drug shown to increase exercise capacity during severe hypoxia both at sea level and at high altitude.

3',5'-Cyclic-GMP Phosphodiesterases↗