Ventilatory and Near-Infrared Spectroscopy Responses Similarly Determine Anaerobic Threshold in Patients With Heart Failure.

PURPOSE: The present study compared the level of agreement of anaerobic threshold (AT) between ventilatory and near-infrared spectroscopy (NIRS) techniques in patients with chronic heart failure (CHF) and healthy subjects. METHODS: Patients with CHF (n = 9) and a control group (CG; n = 14) underwent cardiopulmonary exercise testing on a cycle ergometer until physical exhaustion. Determination of AT was performed visually by (1) ventilatory-expired gas analysis curves and (2) oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) curves assessed by NIRS. RESULTS: The CHF group presented significantly lower oxygen consumption (O2), heart rate, and workload at AT when compared with the CG measured by NIRS (P < .05). However, the effect size, measured by the Cohen d, revealed large magnitude (>0.80) in both techniques when compared between CHF patients and the CG. In addition, ventilatory and NIRS techniques demonstrated significant and very strong/strong correlations for relative O2 (r = 0.91) and heart rate (r = 0.85) in the detection of AT in the CHF group. CONCLUSION: Both ventilatory and NIRS assessments are correlated and there are no differences in the responses between CHF patients and healthy subjects in the determination of AT. These findings indicate both approaches may have utility in the assessment of submaximal exercise performance in patients with CHF.

Effects of tiotropium and formoterol on dynamic hyperinflation and exercise endurance in COPD.

BACKGROUND: It is currently unclear whether the additive effects of a long-acting beta(2)-agonist (LABA) and the antimuscarinic tiotropium bromide (TIO) on resting lung function are translated into lower operating lung volumes and improved exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). METHODS: On a double-blind and cross-over study, 33 patients (FEV(1) = 47.4 +/- 12.9% predicted) were randomly allocated to 2-wk formoterol fumarate 12 microg twice-daily (FOR) plus TIO 18 microg once-daily or FOR plus placebo (PLA). Inspiratory capacity (IC) was obtained on constant-speed treadmill tests to the limit of tolerance (Tlim). RESULTS: FOR-TIO was superior to FOR-PLA in increasing post-treatment FEV(1) and Tlim (1.34 +/- 0.42 L vs. 1.25 +/- 0.39 L and 124 +/- 27% vs. 68 +/- 14%, respectively; p < 0.05). FOR-TIO slowed the rate of decrement in exercise IC compared to FOR-PLA (Deltaisotime-rest = -0.27 +/- 0.40 L vs. -0.45 +/- 0.36 L, p < 0.05). In addition, end-expiratory lung volume (% total lung capacity) was further reduced with FOR-TIO (p < 0.05). Of note, patients showing greater increases in Tlim with FOR-TIO (16/26, 61.6%) had more severe airways obstruction and lower exercise capacity at baseline. Improvement in Tlim with FOR-TIO was also related to larger increases in FEV(1) (p < 0.05). CONCLUSIONS: Compared to FOR monotherapy, FOR-TIO further improved effort-induced dynamic hyperinflation and exercise endurance in patients with moderate-to-severe COPD. These beneficial consequences were more likely to be found in severely-disabled patients with larger resting functional responses to the combination therapy. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT00680056 [ClinicalTrials.gov].

Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF.

Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O(2) pressure and decrease the rate of O(2) transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e.g., angiotensin-converting enzyme inhibitors and third-generation beta-blockers) may have improved microvascular O(2) delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O(2) uptake (Vo(2)) kinetics. We assessed the rate of change of pulmonary Vo(2) (Vo(2)(p)), (estimated) fractional O(2) extraction in the vastus lateralis (approximately Delta[deoxy-Hb+Mb] by near-infrared spectroscopy), and cardiac output (Qt) during high-intensity exercise performed to the limit of tolerance (Tlim) in 10 optimally treated sedentary patients (ejection fraction = 29 + or - 8%) and 11 controls. Sluggish Vo(2)(p) and Qt kinetics in patients were significantly related to lower Tlim values (P < 0.05). The dynamics of Delta[deoxy-Hb+Mb], however, were faster in patients than controls [mean response time (MRT) = 15.9 + or - 2.0 s vs. 19.0 + or - 2.9 s; P < 0.05] with a subsequent response "overshoot" being found only in patients (7/10). Moreover, tauVo(2)/MRT-[deoxy-Hb+Mb] ratio was greater in patients (4.69 + or - 1.42 s vs. 2.25 + or - 0.77 s; P < 0.05) and related to Qt kinetics and Tlim (R = 0.89 and -0.78, respectively; P < 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in "central" and "peripheral" circulatory adjustments still play a prominent role in limiting Vo(2)(p) kinetics and tolerance to heavy-intensity exercise in nontrained patients.

Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure.

Blood flow requirements of the respiratory muscles (RM) increase markedly during exercise in chronic heart failure (CHF). We reasoned that if the RM could subtract a fraction of the limited cardiac output (QT) from the peripheral muscles, RM unloading would improve locomotor muscle perfusion. Nine patients with CHF (left ventricle ejection fraction = 26 +/- 7%) undertook constant-work rate tests (70-80% peak) receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Delta%) in deoxy-hemoglobyn, oxi-Hb ([O2Hb]), tissue oxygenation index, and total Hb ([HbTOT], an index of local blood volume) in the vastus lateralis were measured by near infrared spectroscopy. In addition, QT was monitored by impedance cardiography and arterial O2 saturation by pulse oximetry (SpO2). There were significant improvements in exercise tolerance (Tlim) with PAV. Blood lactate, leg effort/Tlim and dyspnea/Tlim were lower with PAV compared with sham ventilation (P < 0.05). There were no significant effects of RM unloading on systemic O2 delivery as QT and SpO2 at submaximal exercise and at Tlim did not differ between PAV and sham ventilation (P > 0.05). Unloaded breathing, however, was related to enhanced leg muscle oxygenation and local blood volume compared with sham, i.e., higher Delta[O2Hb]% and Delta[HbTOT]%, respectively (P < 0.05). We conclude that RM unloading had beneficial effects on the oxygenation status and blood volume of the exercising muscles at similar systemic O2 delivery in patients with advanced CHF. These data suggest that blood flow was redistributed from respiratory to locomotor muscles during unloaded breathing.