Maximising the clinical use of exercise gaseous exchange testing in children with repaired cyanotic congenital heart defects - The development of an appropriate test strategy

Implicit in deciding upon an exercise test strategy to elucidate cardiopulm onary function in children with congenital heart disease are appropriate ap plication of gas exchange techniques and the significance of the data colle cted to the specific congenital heart disorder. Post-operative cardiopulmon ary responses to exercise in cyanotic disorders are complex and, despite a large body of extant literature in paediatric patients, there has been much difficulty in achieving quality and consistency of data. Maximal oxygen uptake is widely recognised as the best single indicator of cardiopulmonary function and has therefore been the focus of most clinical exercise tests in children. Many children with various heart anomalies are able to exercise to maximum without adverse symptoms, and it is essential t hat test termination is based on the same criteria for these children. Choo sing appropriate, valid indicators of maximum in children with congenital h eart disease is beset by difficulties. Such maximal intensity exercise testing procedures have been challenged on the grounds that they do not give a good indication of cardiopulmonary func tion that is relevant to real life situations. Furthermore, they are prone to much interindividual variability and error in the definition of maximal exertion. Alternative strategies have been proposed which focus upon dynami c submaximal and kinetic cardiopulmonary responses, which are thought to be less dependent on maximal voluntary effort and more suited to the daily ac tivity patterns of children. These methods are also not without problems. V ariability in anaerobic threshold measurements and controversy regarding it s physiological meaning have been debated. It is recommended that an appropriate cardiopulmonary exercise gas exchange test strategy, which provides clinically useful information for children w ith cyanotic congenital heart disease, should include both maximal and subm aximal data. The inclusion of oxygen uptake kinetics and ventilatory data a re encouraged, since they may allow the distinction between a pulmonary, ca rdiovascular or inactivity related exercise limitation.