Pattern of ventilation during exercise in chronic heart failure

Abstract

Objective: To determine the pattern of the abnormal ventilatory response in heart failure and how it relates to symptoms by looking at tidal volume (VT) and frequency (f) during exercise. Methods: 45 patients with heart failure and 21 controls underwent maximal treadmill based exercise testing with metabolic gas exchange analysis. The relation of ventilation (V E) to VT was plotted to look for an inflection point where VT failed to increase further. The slope of the relation before this inflection point was documented. Time to the inflection point, VT, and f at the inflection point were recorded. The relation of symptom scores to f and V E was also examined. Results: Peak oxygen consumption (PV O 2 ) (mean (SD)) was lower (19.7 (4.5) v 37.9 (8.6) ml/kg/min; p < 0001) and the ventilation to carbon dioxide production (V E/V CO 2 ) slope was steeper (40.0 (6.5) v 26.0 (1.6); p < 0.0001) in patients with heart failure than in the control group. The patients reached the inflection point of the V E/VT slope sooner during exercise than the controls (271 (110) v 502 (196) seconds; p < 0.0001). Patients had a higher f and a smaller VT at that point and throughout exercise until the peak where f was the same for patients and controls. VT at the inflection point correlated with PṼO 2 (r = 0.67; p < 0.0001). Despite having an increased sensation of breathlessness for a given V E, patients were less symptomatic of f than controls. Conclusions: Patients with heart failure breathe at a higher f throughout exercise, reaching an apparent maximal VT earlier. The VT at an inflection point on the V E/VT slope predicts PV O 2 .

Health-Related Quality of Life in Relation to Different Levels of Disease Severity in Patients with Chronic Heart Failure

“…BNP concentration increases as CHF becomes more severe, and BNP is a known, independent factor of mortality of CHF 19) . Because BNP concentration in our study increased as NYHA functional class increased, 22) . Ventilation perfusion mismatch, impaired diffusion of metabolic gases, respiratory muscle weakness, and heightened sensitivity of peripheral receptors have all been postulated as possible causes 22) .…”

“…Because BNP concentration in our study increased as NYHA functional class increased, 22) . Ventilation perfusion mismatch, impaired diffusion of metabolic gases, respiratory muscle weakness, and heightened sensitivity of peripheral receptors have all been postulated as possible causes 22) . In this way, physiological outcomes such as peak V With regard to another important outcome, indices of HRQOL also decreased with NYHA functional class.…”

Recommendations on the use of exercise testing in clinical practice

“…Contributory factors include: premature metabolic acidaemia (reflecting reduced O 2 delivery and/or utilisation) [146,147]; increased physiological dead space [4]; increased sympathetic system activation via mechano-or pressor-receptor stimulation in the exercising muscles [148][149][150][151][152] and, possibly, contributions from cardiopulmonary vagal and sympathetic reflexes [132,153,154]. Several studies have shown that breathing pattern in CHF is more rapid and shallow than in healthy controls at any given V9E [4,155,156].…”

Physiology of the abnormal response of heart failure patients to exercise

“…Hyperventilation is observed at each level of exercise compared with controls. The pattern is also different with increased breathing rate and decreased tidal volume [43]. Exertional dyspnea is far from being only related to pulmonary wedge pressure and has been related to CO 2 output, pulmonary dead space, pulmonary blood flow, and activation of peripheral muscle chemoreceptors.…”