Evaluation of the Lung Capillary Blood Volume in Children With Sickle Cell Disease

Overview

Sickle cell disease (SCD) is the most common inherited disease of the world affecting African and Caribbean populations. SCD is caused by the homozygous inheritance of the gene for sickle hemoglobin (HbS). Most patients with SCD develop abnormal pulmonary function characterized by airway obstruction, restrictive lung disease, abnormal diffusing capacity, hypoxemia and pulmonary hypertension In healthy subjects, lung capillary blood volume (Qc) and membrane diffusing capacity (Dm) can be accurately measured by the nitric oxide-carbon monoxide (NO-CO) method. We propose to study, for the first time, lung capillary blood volume and alveolar membrane diffusing capacity, using the NO-CO method, in children with SCD aged of at least 6 years Early determination of lung function and pulmonary circulation in children with SCD is very important, not only for the understanding of physiopathologic mechanisms of the disease but also for a better therapeutic management of these children.

We propose to study, for the first time, lung capillary blood volume and alveolar membrane diffusing capacity, using the NO-CO method, in children with SCD aged of at least 6 years. We will compare lung function and measurement of Qc and Dm in 2 groups of 120 subjects, one group of SCD children, and the other of normal children matched on age and ethnic origin. Measurement of lung capillary blood will be measured twice, to assess short term reproducibility. The measurement will be done in sitting position and lying down for one part of subjects, and at rest and during a moderate rectangular exercise for the other part of subjects. These different tests are designed to assess the physiological adaptation of pulmonary circulation in these two populations of children. Combined with complete lung function measurements, echocardiographic assessment of pulmonary hemodynamics, and measurement of exhaled nitric oxide, these evaluations will lead to a better understanding of pathophysiology of lung injury in SCD. The study will be completes at Robert Debré Hospital, in close collaboration with Sickle Cell Disease Center and Physiology Department. Children will be included after informed consent signed, as legally prescribed.