Eloara M. V. Ferreira

Kinetics of muscle deoxygenation are accelerated at the onset of heavy-intensity exercise in patients with COPD: relationship to central cardiovascular dynamics

Patients with chronic obstructive pulmonary disease (COPD) have slowed pulmonary O(2) uptake (Vo(2)(p)) kinetics during exercise, which may stem from inadequate muscle O(2) delivery. However, it is currently unknown how COPD impacts the dynamic relationship between systemic and microvascular O(2) delivery to uptake during exercise. We tested the hypothesis that, along with slowed Vo(2)(p) kinetics, COPD patients have faster dynamics of muscle deoxygenation, but slower kinetics of cardiac output (Qt) following the onset of heavy-intensity exercise. We measured Vo(2)(p), Qt (impedance cardiography), and muscle deoxygenation (near-infrared spectroscopy) during heavy-intensity exercise performed to the limit of tolerance by 10 patients with moderate-to-severe COPD and 11 age-matched sedentary controls. Variables were analyzed by standard nonlinear regression equations. Time to exercise intolerance was significantly (P < 0.05) lower in patients and related to the kinetics of Vo(2)(p) (r = -0.70; P < 0.05). Compared with controls, COPD patients displayed slower kinetics of Vo(2)(p) (42 +/- 13 vs. 73 +/- 24 s) and Qt (67 +/- 11 vs. 96 +/- 32 s), and faster overall kinetics of muscle deoxy-Hb (19.9 +/- 2.4 vs. 16.5 +/- 3.4 s). Consequently, the time constant ratio of O(2) uptake to mean response time of deoxy-Hb concentration was significantly greater in patients, suggesting a slower kinetics of microvascular O(2) delivery. In conclusion, our data show that patients with moderate-to-severe COPD have impaired central and peripheral cardiovascular adjustments following the onset of heavy-intensity exercise. These cardiocirculatory disturbances negatively impact the dynamic matching of O(2) delivery and utilization and may contribute to the slower Vo(2)(p) kinetics compared with age-matched controls.

Effects of oxygen supplementation on cerebral oxygenation during exercise in chronic obstructive pulmonary disease patients not entitled to long-term oxygen therapy.

Background:  The rate of change (Δ) in cerebral oxygenation (COx) during exercise is influenced by blood flow and arterial O2 content (CaO2). It is currently unclear whether ΔCOx would (i) be impaired during exercise in patients with chronic obstructive pulmonary disease (COPD) who do not fulfil the current criteria for long‐term O2 therapy but present with exercise‐induced hypoxaemia and (ii) improve with hyperoxia (FIO2 = 0·4) in this specific sub‐population.

Optimizing the evaluation of excess exercise ventilation for prognosis assessment in pulmonary arterial hypertension.

Background Increased ventilatory ( V · E) response to carbon dioxide output ( V · CO2) is a key finding of incremental cardiopulmonary exercise testing in both heart failure and pulmonary arterial hypertension (PAH). As with heart failure, measures of excessive exercise ventilation considering high-to-peak exercise V · E– V · CO2 might have higher prognostic relevance than those restrained to sub-maximal exercise in PAH. Design Cross-sectional and observational study on a tertiary center. Methods Eighty-four patients (36 idiopathic and 48 with associated conditions) were followed up for up to five years. Excessive exercise ventilation was calculated as a slope (Δ V · E/Δ V · CO2 to the respiratory compensation point (RCP) and to exercise cessation (PEAK)) and as a ratio ( V · E/ V · CO2 at the anaerobic threshold (AT) and at PEAK). Results Thirteen patients died and three had atrial septostomy. Multivariable regression analyses revealed that Δ V · E/Δ V · CO2(PEAK) <55 and V · E/ V · CO2(PEAK) <57 were better related to prognosis than Δ V · E/Δ V · CO2(RCP) and V · E/ V · CO2(AT) (p < 0.01). Δ oxygen uptake ( V · O2)/Δ work rate >5.5 ml/min per W was the only other independent prognostic index. According to a Kaplan–Meier survival analysis, 96.9% (90.8% to 100%) of patients showing Δ V · E/Δ V · CO2(PEAK) <55 and Δ V · O2/Δ work rate >5.5 ml/min per W were free from a PAH-related event. In contrast, 74.7% (70.1% to 78.2%) with both parameters outside these ranges had a negative outcome. Conclusion Measurements of excessive exercise ventilation which consider all data points maximize the usefulness of incremental cardiopulmonary exercise testing in the prognosis evaluation of PAH.

Haemodynamic effects of proportional assist ventilation during high-intensity exercise in patients with chronic obstructive pulmonary disease.

Background and objective:  Proportional assist ventilation (PAV) has been proposed as a more physiological modality of non‐invasive ventilation, thereby reducing the potential for deleterious cardio‐circulatory effects during exercise, in patients with COPD. We therefore evaluated whether PAV modulates the kinetic and ‘steady‐state’ haemodynamic responses to exercise in patients with moderate‐to‐severe COPD.