Chest
Original ResearchPulmonary PhysiologyThe Impact of Sickle Cell Disease on Exercise Capacity in Children
Section snippets
Exercise Physiology
Noninvasive RMS permits the measurement of physiologic variables during both rest and exercise. Using a rebreathing protocol, the disappearance of acetylene and oxygen determines the effective pulmonary blood flow (Qpeff) (defined as being in contact with ventilated alveoli), effective stroke volume (Qpeff/heart rate), and oxygen consumption, respectively. Their ratio (Fick principle) determines the arteriovenous content difference (AVO).
Similarly, the disappearance of carbon monoxide (CO)
Results
Demographics are summarized in Table 1. Of 100 subjects recruited, four did not attend, two had oxygen saturation < 91% at rest, and five were excluded for persistent mouth leak; therefore, 89 of 100 (44 patients and 45 control subjects) had analyzable exercise data. All 89 reached the 25 W/m2 stage. Patients were well matched for age, but male patients were significantly shorter than control subjects, and female patients had a later puberty. Patients by definition had a lower Hb and higher
Statement of Principal Findings
Children with SCD have a greater than normal Qpeff at rest, on exercise, and during recovery, achieved by raising both stroke volume and heart rate, presumably to compensate for chronic anemia. This compensation was incomplete, as oxygen dispatch was consistently slightly reduced. DLCO corrected for hemoglobin and surface area was consistently slightly greater in subjects with SCD, making the ratio of DLCO to Qpeff about 40% to 50% less in subjects with SCD. Given that recruitment and
Acknowledgments
Author contributions: Dr Rosenthal acts as guarantor of the manuscript.
Dr Chaudry: contributed to recruiting all subjects, supervised all exercise tests, and wrote the drafts of the manuscript.
Dr Bush: contributed to writing and supervision of the project.
Dr Rosenthal: contributed to advising on the exercise protocol, supervised the analyses, assisted with writing, and supervised the project.
Dr Crowley: contributed to conceiving and designing the project and assisted with writing and
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Funding/Support: This study was funded by the St. George's Healthcare National Health Service Trust Charitable Trustees (UK) and The Sobell Foundation (UK). It was supported by the National Institute for Health Research Respiratory Disease Biomedical Research Unit at the Royal Brompton and Harefield National Health Service Foundation Trust and Imperial College London.
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