Abstract
The two main goals of this study were: to determine how O2 uptake, ventilation, and CO2 production during exercise were acutely affected by transfusion in children with congenital anemia (thalassemia major and Diamond-Blackfan syndrome) requiring hypertransfusion and chelation therapy and to compare gas exchange responses to exercise of the anemic patients to normal values. Thirteen patients (age range 7-27) performed cycle ergometry with a progressively increasing work rate. Gas exchange was measured breath-by-breath. Tests were done before and after routine transfusion (mean increase in hematocrit 22%). The results were compared to 10 age-matched normal children who performed the same protocol on two occasions separated by a 2-day interval, and to the results of 109 normal children studied in this laboratory. Transfusion resulted in: a small, but significant increase in the anaerobic threshold (9%) and an increase in the slope of the relationship between O2-uptake and heart rates. Despite these improvements, the majority of the patients had abnormally low values of maximal O2 uptake, anaerobic threshold, and slope of the O2 uptake-heart rate relationship. The abnormalities were more marked in the older patients. Measurement of gas exchange during exercise may be helpful in determining an optimal hematocrit for patients on hypertransfusion regimens.
Highlights
Sufficient for normal cardiovascular and respiratory function at the same time that the consequent iron overload can be eliminated by chelation therapy
The present study was designed with two goals: I) to compare the gas exchange responses to exercise in children with congenital anemia to those in a large group of normal children previously studied in our laboratory [9, 10] and 2) to examine how the gas exchange responses in the patients were acutely affected by transfusions
Twelve of the 13 patients were below their predicted value and five were below 2 SD. (Consistent with this, the mean V02max of the patients was significantly lower than the mean V02max of the 10 control subjects.) There was no significant change in V02max in the patients following transfusion
Summary
Sufficient for normal cardiovascular and respiratory function at the same time that the consequent iron overload can be eliminated by chelation therapy. We reasoned that measurement of gas exchange during exercise could prove useful in these patients since it allows an assessment of the response of the cardiovascular and respiratory systems to increases in metabolic demand. The measurement of the dynamic responses of V 0 2 ,VE,and VC02(e.g.the anaerobic threshold) to exercise has not been frequently used to assess cardiac and respiratory function in children, but the ability of the organism to consume atmospheric O2is the final and critical product of adjustments of cardiac output and ventilation. The analysis of gas exchange during exercise yields an insight into the adequacy of a patient's response that cannot be obtained from measurements of cardiac output or ventilation alone. The present study was designed with two goals: I) to compare the gas exchange responses to exercise in children with congenital anemia to those in a large group of normal children previously studied in our laboratory [9, 10] and 2) to examine how the gas exchange responses in the patients were acutely affected by transfusions
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