Abstract
Sickle cell anemia (SCA) causes dysfunction of multiple organs, with pulmonary involvement as a major cause of mortality. Recently, there has been growing interest in the nitrogen single-breath washout (N2SBW) test, which is able to detect ventilation heterogeneity and small airway disease when the results of other pulmonary function tests (PFTs) are still normal. Thus, the objectives of the present study were to assess the heterogeneity in the ventilation distribution in adults with SCA and to determine the association between the ventilation distribution and the clinical, cardiovascular, and radiological findings. This cross-sectional study included 38 adults with SCA who underwent PFTs, echocardiography, computed tomography (CT), and 6-min walk test. To evaluate the ventilation heterogeneity, the patients were categorized according to the phase III slope of the N2SBW (SIIIN2). Compared with adults with lower SIIIN2 values, adults with higher SIIIN2 values showed lower hemoglobin levels (P=0.048), a history of acute chest syndrome (P=0.001), an elevated tricuspid regurgitation velocity (P=0.039), predominance of a reticular pattern in the CT (P=0.002), a shorter 6-min walking distance (6MWD) (P=0.002), and lower peripheral oxygen saturation (SpO2) after exercise (P=0.03). SIIIN2 values correlated significantly with hemoglobin (rs=-0.344; P=0.034), forced vital capacity (rs=-0.671; P<0.0001), diffusing capacity for carbon monoxide (rs=-0.376; P=0.019), 6MWD (rs=-0.554; P=0.0003), and SpO2 after exercise (P=0.040). Heterogeneity in the ventilation distribution is one of the most common pulmonary dysfunctions in adults with SCA. Moreover, relationships exist between ventilation heterogeneity, worsening of pulmonary structural damage, and reduced tolerance for exercise.
Highlights
Sickle cell anemia (SCA) is a disease with systemic repercussions
The following exclusion criteria were used: a history of acute chest syndrome (ACS) or vaso-occlusive crisis (VOC) in the last 4 weeks, a report of having received a blood transfusion in the last 3 months, a history of upper respiratory tract infection in the last 3 weeks, a history of smoking 410 packs per year, a report of previous pleuropulmonary disease not related to ACS, and any physical impairment that would impair the performance of the 6-min walk test (6MWT)
The main findings of the present study were that most adults with SCA presented heterogeneity in the ventilation distribution and that a lower frequency of patients presented with small airway disease
Summary
Sickle cell anemia (SCA) is a disease with systemic repercussions. Multiple organ dysfunction occurs due to inflammation, abnormal blood rheology, vaso-occlusion, and endothelial dysfunction [1,2]. The polymerization of hemoglobin S (Hb S) within the cell is the central event that occurs in the pathophysiology of SCA; there is increasing evidence that nitric oxide (NO) sequestration by cell-free Hb and impaired bioavailability of NO during intravascular hemolysis play important roles in SCA pathophysiology [1,2]. Respiratory system involvement accounts for approximately 30% of all deaths in patients with SCA and mainly involves acute chest syndrome (ACS) and pulmonary hypertension (PH) [1,2,3,4]. ACS is one of the most important events in patients with SCA and is a manifestation of the vaso-occlusive phenomenon that can progress to acute respiratory distress syndrome, respiratory failure, and death [3,5]. PH has a prevalence of approximately 10%, and its pathophysiology involves vaso-occlusive pulmonary phenomena, chronic hypoxia, pulmonary fibrosis, hemolysis, asplenia, iron overload, and endothelial dysfunction due to resistance to nitric oxide [6,7]
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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