Gas Exchange during Exercise in Children with Thalassemia Major and Diamond-Blackfan Anemia

Abstract

ABSTRACT: The two main goals of the study were: 1) 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 2) 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 agematched normal children who performed the same protocol on two occasions separated by a 2-day interval, and to the reults of 109 normal children studied in this laboratory. Transfusion resulted in: 1) a small, but significant increase in the anaerobic threshold (9%) and 2) 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.

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