Mechanisms That Modulate Peripheral Oxygen Delivery during Exercise in Heart Failure.

Oxygen uptake ([Formula: see text]o) measured at the mouth, which is equal to the cardiac output (CO) times the arterial-venous oxygen content difference [C(a-v)O], increases more than 10- to 20-fold in normal subjects during exercise. To achieve this substantial increase in oxygen uptake [[Formula: see text]o = CO × C(a-v)O] both CO and the arterial-venous difference must simultaneously increase. Although this occurs in normal subjects, patients with heart failure cannot achieve significant increases in cardiac output and must rely primarily on changes in the arterial-venous difference to increase [Formula: see text]o during exercise.

Better parameters of ventilation-CO₂output relationship predict death in CHF patients.

Objective: Measures of ventilation-CO₂output relationship have been shown to be more prognostic than peak O₂uptake in assessing life expectancy in patients with chronic heart failure (CHF). Because both the ratios (VE/Vco₂) and slopes (VE-vs-Vco₂) of ventilation-co₂ output of differing durations can be used, we aim to ascertain which measurements best predicted CHF life expectancy.

Methods: Two hundred and seventy-one CHF patients with NYHA class II-IV underwent incremental cardiopulmonary exercise testing (CPET) and were followed-up for a median duration of 479 days.

CO2 pulse and acid-base status during increasing work rate exercise in health and disease.

The CO2 pulse (VCO2/heart rate), analogous to the O2 pulse (VO2/heart rate), was calculated during cardiopulmonary exercise testing and evaluated in normal and diseased states. Our aim was to define its application in its release in excess of that from VCO2/heart rate in the presence of impaired cardiovascular and lung function. In the current study, forty-five patients were divided into six physiological states: normal, exercise-induced myocardial ischemia, chronic heart failure, pulmonary vasculopathy, chronic obstructive pulmonary disease, and interstitial lung disease.

[Parameters of oxygen uptake and carbon dioxide output ventilatory efficiency during exercise are index of circulatory function in normal subjects].

Objective: To observe oxygen uptake efficiency plateau (OUEP, i.e.highest V˙O2/V˙E) and carbon dioxide output efficiency (lowest V˙E/V˙CO2) parameter changes during exercise in normal subjects.

Clinical significance of a spiral phenomenon in the plot of CO₂ output versus O₂ uptake during exercise in cardiac patients.

A spiral phenomenon is sometimes noted in the plots of CO₂ output (VCO₂) against O₂ uptake (VO₂) measured during cardiopulmonary exercise testing (CPX) in patients with heart failure with oscillatory breathing. However, few data are available that elucidate the clinical significance of this phenomenon. Our group studied the prevalence of this phenomenon and its relation to cardiac and cardiopulmonary function.

Altered breathing syndrome in heart failure: newer insights and treatment options.

In patients with heart failure (HF), altered breathing patterns, including periodic breathing, Cheyne-Stokes breathing, and oscillatory ventilation, are seen in several situations. Since all forms of altered breathing cause similar detrimental effects on clinical outcomes, they may be considered collectively as an "altered breathing syndrome." Altered breathing syndrome should be recognized as a comorbid condition of HF and as a potential therapeutic target.

Ventilatory regulation of arterial H(+) (pH) during exercise.

We hypothesized that exercise ventilation and arterial H(+) ([H(+)]a) are mutually interactive, [H(+)]a stimulating V(E) and V(E) regulating [H(+)]a increase. Fifty-five patients were studied, 10 normal and 45 with cardio-respiratory disorders. Each patient underwent cardiopulmonary exercise testing with simultaneous serial arterial blood gas and pH measurements.

Relation between oscillatory breathing and cardiopulmonary function during exercise in cardiac patients.

Background: Oscillatory breathing, alternating between hyperpnea and hypopnea, has been recognized in cardiac patients, especially in those with heart failure. We evaluated whether the cycle length and amplitude of oscillatory breathing correlate with impaired cardiopulmonary function during exercise.

Methods And Results: We analyzed respiratory gas data during cardiopulmonary exercise testing (CPX) in 17 cardiac patients (68 ± 12 years) who showed clear oscillatory ventilation during CPX.

Abnormal end-tidal PO(2) and PCO(2) at the anaerobic threshold correlate well with impaired exercise gas exchange in patients with left ventricular dysfunction.

Background: The aim of the present study was to compare the end-tidal O(2) pressure (PETO(2)) to end-tidal CO(2) pressure (PETCO(2)) in cardiac patients during rest and during 2 states of exercise: at anaerobic threshold (AT) and at peak. The purpose was to see which metabolic state, PETO(2) or PETCO(2), best correlated with exercise limitation.

Methods And Results: Thirty-eight patients with left ventricular (LV) ejection fraction <40% underwent cardiopulmonary exercise testing (CPX).

Arterial H+ regulation during exercise in humans.

Resting arterial H+ concentration ([H+]a) is in the nanomolar range (40±2 nm/L) while its production is in the millimolar range/min, with little variation from subject to subject. To determine the precision with which [H(+)]a is regulated during exercise, [H+]a, PaCO2 and ventilation (V˙(E)) were measured during progressively increasing work rate exercise in 16 normal subjects. (V˙(E)) increased with [H+]a, the latter attributable to PaCO2 increase below the lactic acidosis threshold (LAT) (ΔV˙(E)/Δ[H+]a ≈ 15   L   min(-1)   nanomol(-1)).

Developing pulmonary vasculopathy in systemic sclerosis, detected with non-invasive cardiopulmonary exercise testing.

Background: Patients with systemic sclerosis (SSc) may develop exercise intolerance due to musculoskeletal involvement, restrictive lung disease, left ventricular dysfunction, or pulmonary vasculopathy (PV). The latter is particularly important since it may lead to lethal pulmonary arterial hypertension (PAH). We hypothesized that abnormalities during cardiopulmonary exercise testing (CPET) in patients with SSc can identify PV leading to overt PAH.

Exercise capacity in idiopathic pulmonary fibrosis: the effect of pulmonary hypertension.

Background And Objective: Increased pulmonary arterial pressure (PAP) usually coexists with impaired lung function in IPF. Data on the effect of pulmonary hypertension (PH) on cardiopulmonary responses during exercise in IPF patients is very limited. We sought to investigate the impact of PH on exercise capacity and the correlation between systolic PAP (sPAP) and pulmonary function testing, as well as cardiopulmonary exercise parameters, in patients with IPF and PH.

The utility of cardiopulmonary exercise testing to detect and track early-stage ischemic heart disease.

Evidence demonstrating the potential value of noninvasive cardiopulmonary exercise testing (CPET) to accurately detect exercise-induced myocardial ischemia is emerging. This case-based concept report describes CPET abnormalities in an asymptomatic at-risk man with suspected early-stage ischemic heart disease. When CPET was repeated 1 year after baseline assessment, his cardiovascular function had worsened, and an anti-atherosclerotic regimen was initiated.

Oscillatory breathing and exercise gas exchange abnormalities prognosticate early mortality and morbidity in heart failure.

Objectives: The goal of this study was to identify better predictors of early death in patients with chronic left ventricular heart failure (CHF). Potential predictors, derived from cardiopulmonary exercise testing, were compared with other commonly used cardiovascular measurements.

Background: The prediction of early death in patients with CHF remains challenging.

Usefulness of right-to-left shunting and poor exercise gas exchange for predicting prognosis in patients with pulmonary arterial hypertension.

We hypothesized that the longitudinal changes in peak oxygen uptake, ventilatory efficiency, and exercise-induced right-to-left shunting in patients with pulmonary arterial hypertension (PAH) would predict outcomes better than baseline measurements alone. Patients with PAH die prematurely. Identifying prognostic markers is critical for treating patients with PAH; however, longitudinal prognostic information of PAH is limited.

Paradoxical potentiation of exercise hyperpnea in congestive heart failure contradicts Sherrington chemoreflex model and supports a respiratory optimization model.

Congestive heart failure (CHF) patients suffer decreased exercise tolerance, yet they demonstrate an augmented ventilatory response to exercise such that P(aCO2) remains normal (isocapnic) from rest to maximal exercise in the face of increased pulmonary dead space (Fig. 1). On the other hand, the effect of a large external dead space is hypercapnic instead of isocapnic.

Oxygen uptake kinetics during and after exercise are useful markers of coronary artery disease in patients with exercise electrocardiography suggesting myocardial ischemia.

Background: The aim of the current study was to determine if the slowed exercise oxygen uptake (VO(2)) kinetics, which is developed by myocardial ischemia, would be accompanied by delayed recovery VO(2) kinetics in patients with coronary artery disease (CAD).

Methods And Results: Thirty-seven patients with significant ST depression during treadmill exercise underwent cardiopulmonary exercise testing with cycle ergometer. Measurements performed are the ratios of change in increase in oxygen (O(2)) uptake relative to increase in work rate (DeltaVO(2)/DeltaWR) across anaerobic threshold (AT) and 1 mm ST depression point (ST-dep), the time constants of VO(2) during recovery (T(1/2) VO(2)), stress radio-isotope scintigraphy and coronary angiography.

Alveolar membrane conductance decreases as BNP increases during exercise in heart failure. Rationale for BNP in the evaluation of dyspnea.

Background: In left ventricular failure (LVF) patients, brain natriuretic peptide (BNP), lung diffusion for carbon monoxide (DLCO), and alveolar-membrane conductance (DM) correlate with LVF severity and prognosis. The reduction of DLCO and DM during exercise reflects pulmonary edema formation.

Methods And Results: To evaluate, in LVF patients, the correlation between BNP and lung diffusion parameters at rest and during exercise, we studied 17 severe LVF patients, 13 moderate, and 10 normals measuring BNP and lung diffusion parameters before, at the end, and 1 hour after a 10-minute high-intensity constant-workload exercise.

The utility of cardiopulmonary exercise testing in the assessment of suspected microvascular ischemia.

Evidence demonstrating the potential value of cardiopulmonary exercise testing (CPET) to accurately detect myocardial ischemia secondary to macro-vascular disease is beginning to emerge. Despite distinct mechanisms mediating ischemia in micro-vascular and macrovascular coronary artery disease (CAD), the net physiologic effect of exercise-induced left ventricular (LV) dysfunction is common to both. The abnormal physiologic response to CPET may, therefore, be similar in patients with macro- and micro-vascular ischemia.

Exercise-induced myocardial ischemia detected by cardiopulmonary exercise testing.

Cardiopulmonary exercise testing (CPET) is a well-accepted physiologic evaluation technique in patients diagnosed with heart failure and in patients presenting with unexplained dyspnea on exertion. Several variables obtained during CPET, including oxygen consumption relative to heart rate and work rate provide consistent, quantitative patterns of abnormal physiologic responses to graded exercise when left ventricular dysfunction is caused by myocardial ischemia. This concept report describes both the methodology and clinical application of CPET associated with myocardial ischemia.

A sex-specific relationship between capillary density and anaerobic threshold.

Although both capillary density and peak oxygen consumption (Vo(2)) improve with exercise training, it is difficult to find a relationship between these two measures. It has been suggested that peak Vo(2) may be more related to central hemodynamics than to the oxidative potential of skeletal muscle, which may account for this observation. We hypothesized that change in a measure of submaximal performance, anaerobic threshold, might be related to change in skeletal muscle capillary density, a marker of oxidative potential in muscle, with training.

Argument for changing criteria for bronchodilator responsiveness.

Background: Extensively used current guidelines of the American Thoracic Society/European Respiratory Society (ATS/ERS) define a positive aerosolized bronchodilator (BD) response as: "...