Chronic heart failure (CHF) is the condition in which the heart is unable to maintain sufficient cardiac output (the amount of blood that the heart pumps) for adequate tissue oxygenation. In order to find the right treatment for CHF patients, it is crucial to find out whether these patients are primarily limited by oxygen delivery or by oxygen utilization. Near-InfraRed Spectroscopy (NIRS) has the ability to monitor changes in muscle oxygenation during exercise. This technique has the potential to disclose the nature of the limitation in a totally non-invasive setup. Before introducing NIRS as a routine measurement in a clinical setting it is crucial to investigate the applicability and reproducibility of various NIRS parameters, especially in moderately impaired CHF patients. To reach that goal we have investigated the kinetics of the local tissue oxygenation (Tissue Saturation Index (TSI)) in a skeletal muscle during onset and recovery of submaximal exercise. The associated parameters represent a ratio between oxygen delivery and utilization and were found with an acceptable reproducibility. In comparison with healthy control subjects on average both onset and recovery appeared to be delayed in CHF patients. It is suggested that a delayed TSI onset indicates a CHF patient with a more pronounced limitation in oxygen utilization and a delayed TSI recovery a CHF patient with a limitation in oxygen delivery. The nature of the slowing of the pulmonary oxygen uptake kinetics during onset and recovery of exercise contributes to a better understanding of the pathophysiology of heart failure in an individual patient. The correlation between the TSI recovery kinetics and the oxygen recovery kinetics measured in lung function tests suggests that the slowing of the oxygen recovery kinetics in CHF patients is more governed by processes which regulate the oxygen delivery. From these results it can be concluded that treatments that improve the skeletal muscle oxygen delivery or the skeletal muscle oxygen utilization can both be necessary to ameliorate exercise intolerance in moderately impaired CHF patients. In practice this means that some patients are in need of an improved cardiac output for instance with Cardiac Resynchronization Therapy (CRT), while others are better helped with physical exercise.
|Date of Award||28 Feb 2014|
|Supervisor||P.F.F. Wijn (Supervisor 1) & M.M.J. Damen (Supervisor 2)|