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Published on: November 5, 2019
The impact of sickle cell disease on exercise capacity in children
Rifat A Chaudry1, Andrew Bush2, Mark Rosenthal2
1Department of Paediatric Respiratory Medicine, Royal Brompton Hospital, London, England; St. George's Hospital, London, England.
Insights
Children with sickle cell disease (SCD) experience exercise limitations due to insufficient pulmonary blood flow (Qpeff) to compensate for anemia, not subtle pulmonary vascular disease. This impacts their overall exercise capacity.
Area of Science:
- Pulmonary Medicine
- Pediatric Hematology
- Cardiopulmonary Physiology
Background:
- Pulmonary vascular complications in children with sickle cell disease (SCD) are not well understood.
- Pulmonary vascular abnormalities may impact exercise capacity in pediatric SCD patients.
Purpose of the Study:
- To investigate pulmonary vascular complications in children with SCD.
- To determine if diffusing capacity of the lung for carbon monoxide (D(LCO)) can serve as a surrogate for pulmonary vascular bed size.
- To assess the impact of pulmonary vascular abnormalities on exercise capacity in pediatric SCD.
Main Methods:
- Fifty stable pediatric SCD patients (10-18 years) and 50 healthy controls underwent incremental ergometer cardiopulmonary exercise testing.
- Respiratory mass spectrometry was used for gas analysis, including rebreathing maneuvers to measure functional residual capacity, effective pulmonary blood flow (Qpeff), and D(LCO).
- Helium dilution calculated ventilation, oxygen consumption, and CO2 production.
Main Results:
- No ventilatory differences were observed between SCD and control subjects.
- Effective pulmonary blood flow (Qpeff) was 15-20% higher in SCD patients, while D(LCO) was only 7-10% higher.
- The D(LCO)/Qpeff ratio was significantly lower in SCD patients, indicating reduced pulmonary capillary blood volume relative to flow.
Conclusions:
- Exercise limitation in pediatric SCD is primarily due to insufficient Qpeff to compensate for anemia, not subtle pulmonary vascular disease.
- A reduced D(LCO)/Qpeff ratio suggests underlying pulmonary vascular changes, but these do not appear to be the main factor limiting exercise.
- Findings challenge the hypothesis that D(LCO) is a direct surrogate for pulmonary vascular bed size in this population.
Background:
Little is known about pulmonary vascular complications in children with sickle cell disease (SCD). We hypothesized that transfer factor (diffusing capacity of the lung for carbon monoxide [D(LCO)] ) may be used as a surrogate for the size of the pulmonary vascular bed and that pulmonary vascular abnormalities in children with SCD may limit exercise capacity.
Methods:
Fifty stable patients with SCD aged 10 to 18 years and 50 healthy control subjects matched for race and age were recruited. Incremental ergometer cardiopulmonary exercise testing was performed using respiratory mass spectrometry for exhaled gas analysis. A rebreathing maneuver was used to measure functional residual capacity, effective pulmonary blood fl ow (Qpeff), and D(LCO), and helium dilution was used to calculate minute ventilation, oxygen consumption, and CO 2 production.
Results:
In the 89 evaluable subjects, there were no ventilatory differences between SCD and control subjects. Qpeff was consistently 15% to 20% greater in subjects with SCD than control subjects at all stages, but D(LCO) corrected for both surface area and hemoglobin was only about 7% to 10% greater in subjects with SCD at all stages. As a result, the D(LCO)/Qpeff ratio was considerably lower in SCD at all stages. Arteriovenous oxygen content difference was about one-third less in SCD at all stages.
Conclusions:
Contrary to our hypothesis, failure to maintain a sufficient Qpeff to compensate for anemia led to exercise limitation. The ratio of pulmonary capillary blood volume to fl ow is reduced throughout, implying subtle pulmonary vascular disease; however, this was not a factor limiting exercise.
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