Longitudinal Decline in Lung Volume in a Population of Children with Sickle Cell Disease

Long-Term Organ Function After HCT for SCD: A Report From the Sickle Cell Transplant Advocacy and Research Alliance

Hematopoietic cell transplantation (HCT) is an established cure for sickle cell disease (SCD) supported by long-term survival, but long-term organ function data are lacking. We sought to describe organ function and assess predictors for dysfunction in a retrospective cohort (n = 247) through the Sickle cell Transplant Advocacy and Research alliance. Patients with <1-year follow-up or graft rejection/second HCT were excluded. Organ function data were collected from last follow-up. Primary measures were organ function, comparing pre- and post-HCT. Bivariable and multivariable analyses were performed for predictors of dysfunction. Median age at HCT was 9.4 years; the majority had HbSS (88.2%) and severe clinical phenotype (65.4%). Most received matched related (76.9%) bone marrow (83.3%) with myeloablative conditioning (MAC; 57.1%). Acute and chronic graft-versus-host disease (GVHD) developed in 24.0% and 24.8%. Thirteen patients (5.3%) died ≥1 year after HCT, primarily from GVHD or infection. More post-HCT patients had low ejection or shortening fractions than pre-HCT (0.6% → 6.0%, P = .007 and 0% → 4.6%, P = .003). The proportion with lung disease remained stable. Eight patients (3.2%) had overt stroke; most had normal (28.3%) or stable (50.3%) brain magnetic resonance imaging. On multivariable analysis, cardiac dysfunction was associated with MAC (odds ratio [OR] = 2.71; 95% confidence interval [CI], 1.09-6.77; P = .033) and severe acute GVHD (OR = 2.41; 95% CI, 1.04-5.62; P = .041). Neurologic events were associated with central nervous system indication (OR = 2.88; 95% CI, 2.00-4.12; P < .001). Overall organ dysfunction was associated with age ≥16 years (OR = 2.26; 95% CI, 1.35-3.78; P = .002) and clinically severe disease (OR = 1.64; 95% CI, 1.02-2.63; P = .043). In conclusion, our results support consideration of HCT at younger age and use of less intense conditioning.

The Cardiopulmonary Complications of Sickle Cell Disease

Sickle cell disease (SCD) is a genetic hemoglobinopathy associated with extensive morbidity and early mortality. While there have been recent improvements in available disease-modifying therapies for SCD, cardiopulmonary complications remain a major risk factor for death in this population. We provide an overview of current knowledge regarding several of the major acute and chronic cardiopulmonary complications in SCD, including: acute chest syndrome, airway disease, lung function abnormalities, nocturnal hypoxemia and sleep disordered breathing, pulmonary vascular disease, and sickle cell cardiomyopathy.

Spirometric Changes After Initiation of Hydroxyurea in Children With Sickle Cell Anemia

Individuals with sickle cell disease (SCD) develop a decline in lung function over time. Hydroxyurea (HU) is the most common disease-modifying therapy used in SCD. We hypothesized that children with SCD treated with HU will have a slower decline in pulmonary function. We performed a retrospective chart review of children with HbSS and HbS-beta zero thalassemia referred to pulmonology for respiratory symptoms. We compared the spirometry results at 2 time points between children on HU (HU group) and not on HU (control group). For the HU group, these endpoints were evaluated before and after being on HU. The mean time interval between 2 spirometry studies was not significantly different between the groups (2.6±1.5 y for HU group vs. 3.0±1.8 y for the control group; P =0.33). The mean age of patients in the HU group was 9.8±3.8 years (55% male) and 10.7±4.9 years (50% male) in the control group. The spirometry data was compared within and between the groups using t test. There was a significant increase in forced vital capacity in HU group during follow-up, while children in the control group showed a decline (7.2±17.1 vs. -3.4±18.2; P <0.01). Our study suggests that HU therapy may help preserve lung function over time in children with SCD.

Cardiopulmonary changes in patients with sickle cell anemia: A systematic review

BACKGROUND

Given the high prevalence of cardiovascular and pulmonary abnormalities associated with sickle cell anemia (SCA), the clinical impact caused in addition to compromising the quality of life of patients and the overcharge that it represents to the public health system, this study systematized and evaluated scientific publications on pulmonary complications and cardiovascular diseases in sickle cell patients from 1920 to 2020. This compilation aims to provide knowledge for health professionals and managers in order to draw attention to the importance of chronic diseases in SCA patients and in addition to providing elements that provide improvements in management of useful resources that contribute to improve the quality and increase the life expectancy of these patients.

AIM

To systematically compile information about cardiopulmonary changes in patients with SCA.

METHODS

A systematic literature review was performed based on the PRISMA recom-mendation including scientific articles indexed in the Scientific Electronic Library Online databases of the United States National Library of Medicine and Biblioteca Virtual de Saúde. The search period was delimited between 1990 and 2020 and selected in Portuguese, English and Spanish. Three sets of descriptors were used for each database including research carried out with human beings. After reading the articles, those useful for this review were extracted using a collection instrument designed for this purpose.

RESULTS

The final selection included 27 studies. The year with the highest number of publications was 2016 with 5 studies (18.51%), followed by 2017 with 4 (14.81%). The type of study most carried out in the period was cohort 10 (37.03%) followed by cross-sectional and case-control with 8 studies in each (29.62%). Regarding the language of publication, the distribution was as follows: 25 (92.59%) in English, 1 (3.70%) in Spanish and 1 (3.70%) in Portuguese.

CONCLUSION

The findings of the present study suggest that cardiopulmonary alterations represent a serious clinical repercussion of SCA. Of the analyzed studies, the high occurrence of pulmonary hypertension, ventricular hypertrophy and diastolic dysfunction stands out as the main cardiopulmonary complications. In view of the increased survival in SCA, there is a need for surveillance and the development of strategies aimed at preserving the cardiopulmonary function and consequently improving the quality of life of these patients.

Lung Clearance Index May Detect Early Peripheral Lung Disease in Sickle Cell Anemia

RATIONALE

Chronic lung injury is common in sickle cell anemia (SCA) and worsens outcomes. Sensitive lung function tests might predict reversible disease that might benefit from therapeutic interventions.

OBJECTIVE

To evaluate whether Lung Clearance Index (LCI), S_acin & S_cond, measuring global, intracinar & conductive ventilation inhomogeneity respectively, are more frequently abnormal than lung volumes in young people with SCA.

METHODS

Nitrogen multiple breath washout, spirometry and body plethysmography were cross-sectionally evaluated at steady state in subjects with SCA (hemoglobin SS) and healthy controls aged 8-21 years from London, UK.

RESULTS

35 patients (51% boys; mean±SD 16.4±3.5 years) and 31 controls (48% boys; 16.2±3.2 years) were tested. There were significant differences between the study and control group in mean LCI (mean difference 0.42 units, 95%CI 0.22 to 0.63, p = 0.0001), S_acin (mean difference 0.014 units, 95%CI 0.001 to 0.026, p = 0.04), FEV₁ (mean difference -0.79 z-scores, 95%CI -1.28 to -0.30, p = 0.002), FVC (mean difference -0.80 z-scores, 95%CI -1.28 to -0.31) and TLC (mean difference -0.79 z-scores, 95%CI -1.25 to -0.29), but not in S_cond and FEV₁/FVC ratio. While 29% (10/35) of patients had LCI >95th percentile of controls, 23% (8/35) had abnormal FEV₁ (<5th of the reference population).

CONCLUSION

Lung clearance index detected slightly more abnormalities than lung volumes in young people with SCA. Significant differences with controls in LCI and S_acin but not in S_cond and FEV₁/FVC ratio suggest that the lung function changes were most likely due to patchy peripheral lung disease.

Stable to improved cardiac and pulmonary function in children with high-risk sickle cell disease following haploidentical stem cell transplantation

Children with sickle cell disease (SCD) are at high-risk of progressive, chronic pulmonary and cardiac dysfunction. In this prospective multicenter Phase II trial of myeloimmunoablative conditioning followed by haploidentical stem cell transplantation in children with high-risk SCD, 19 patients, 2.0-21.0 years of age, were enrolled with one or more of the following: history of (1) overt stroke; (2) silent stroke; (3) elevated transcranial Doppler velocity; (4) multiple vaso-occlusive crises; and/or (5) two or more acute chest syndromes and received haploidentical transplants from 18 parental donors. Cardiac and pulmonary centralized cores were established. Pulmonary function results were expressed as percent of the median of healthy reference cohorts, matched for age, sex, height and race. At 2 years, pulmonary functions including forced expiratory volume (FEV), FEV₁/ forced vital capacity (FVC), total lung capacity (TLC), diffusing capacity of lung for carbon monoxide (DLCO) were stable to improved compared to baseline values. Importantly, specific airway conductance was significantly improved at 2 years (p < 0.004). Left ventricular systolic function (fractional shortening) and tricuspid regurgitant velocity were stable at 2 years. These results demonstrate that haploidentical stem cell transplantation can stabilize or improve cardiopulmonary function in patients with SCD.

Chronic organ injuries in children with sickle cell disease

Median life expectancy of patients with sickle cell disease has increased to up to 55 years but there are still frequent cases of premature death, mostly in patients with pre-existing organ failure such as pulmonary hypertension, kidney injury, and cerebral vasculopathy. Most organ injuries remain asymptomatic for a long time and can only be detected through early systematic screening. Protocols combining assessment of velocities on transcranial Doppler and regular transfusions in patients with abnormal velocities have been demonstrated to dramatically reduce the risk of stroke. In contrast, no consensus has been reached on systematic screening or therapy for silent cerebral infarcts. The prognostic significance of increased tricuspid regurgitant jet velocity on echocardiography has not yet been identified in children, whereas increased albuminuria is a good predictor of kidney injury. Finally, screening for hip and eye disorder is recommended; however, different countries adopt different screening strategies. Hydroxyurea is probably of potential benefit in preventing chronic organ damage but this requires further study in order to be fully demonstrated. Efficacy and safety of the other new drugs available are also under investigation.

Lung clearance index in children with sickle cell disease

INTRODUCTION

The lung clearance index (LCI) derived from the multiple breath washout test (MBW), is both feasible and sensitive to early lung disease detection in young children with cystic fibrosis and asthma. The utility of LCI has not been studied in children with sickle cell disease (SCD). We hypothesized that children with SCD, with or without asthma or airway hyperreactivity (AHR), would have an elevated LCI compared to healthy controls.

METHODS

Children with SCD from a single center between the ages of 6 and 18 years were studied at baseline health and completed MBW, spirometry, plethysmography and blood was drawn for serum markers. Results were compared to healthy controls of similar race, age, and gender.

RESULTS

Healthy controls (n = 35) had a significantly higher daytime oxygen saturation level, weight and body mass index but not height compared to participants with SCD (n = 34). Total lung capacity (TLC) z-scores were significantly higher in the healthy controls compared to those with SCD (0.87 [1.13] vs. 0.02 [1.27]; p = .005) while differences in forced expiratory volume in 1 s z-scores approached significance (0.26 [0.97] vs. -0.22 [1.09]; p = .055). There was no significant difference in LCI between the healthy controls compared to participants with SCD (7.29 [0.72] vs. 7.40 [0.69]; p = .514).

CONCLUSION

LCI did not differentiate SCD from healthy controls in children between the ages of 6 and 18 years at baseline health. TLC may be an important pulmonary function measure to follow longitudinally in the pediatric SCD population.

Predictors of Diffusing Capacity in Children With Sickle Cell Disease: A Longitudinal Study

Background: Gas exchange abnormalities in Sickle Cell Disease (SCD) may represent cardiopulmonary deterioration. Identifying predictors of these abnormalities in children with SCD (C-SCD) may help us understand disease progression and develop informed management decisions. Objectives: To identify pulmonary function tests (PFT) estimates and biomarkers of disease severity that are associated with and predict abnormal diffusing capacity (DLCO) in C-SCD. Methods: We obtained PFT data from 51 C-SCD (median age:12.4 years, male: female = 29:22) (115 observations) and 22 controls (median age:11.1 years, male: female = 8:14), formulated a rank list of DLCO predictors based on machine learning algorithms (XGBoost) or linear mixed-effect models, and compared estimated DLCO to the measured values. Finally, we evaluated the association between measured or estimated DLCO and clinical outcomes, including SCD crises, pulmonary hypertension, and nocturnal desaturation. Results: Hemoglobin-adjusted DLCO (%) and several PFT indices were diminished in C-SCD compared to controls. Both statistical approaches ranked FVC (%), neutrophils (%), and FEF_25-75 (%) as the top three predictors of DLCO. XGBoost had superior performance compared to the linear model. Both measured and estimated DLCO demonstrated a significant association with SCD severity: higher DLCO, estimated by XGBoost, was associated with fewer SCD crises [beta = -0.084 (95%CI: -0.13, -0.033)] and lower TRJV [beta = -0.009 (-0.017, -0.001)], but not with nocturnal desaturation (p = 0.12). Conclusions: In this cohort of C-CSD, DLCO was associated with PFT estimates representing restrictive lung disease (FVC, TLC), airflow obstruction (FEF_25-75, FEV1/FVC, R5), and inflammation (neutrophilia). We used these indices to estimate DLCO, and show association with disease outcomes, underscoring the prediction models' clinical relevance.

Management of chronic respiratory complications in children and adolescents with sickle cell disease

Sickle cell disease (SCD) is a life-threatening hereditary blood disorder that affects millions of people worldwide, especially in sub-Saharan Africa. This condition has a multi-organ involvement and highly vascularised organs, such as the lungs, are particularly affected. Chronic respiratory complications of SCD involve pulmonary vascular, parenchymal and airways alterations. A progressive decline of lung function often begins in childhood. Asthma, sleep-disordered breathing and chronic hypoxaemia are common and associated with increased morbidity. Pulmonary hypertension is a serious complication, more common in adults than in children. Although there is a growing attention towards respiratory care of patients with SCD, evidence regarding the prognostic meaning and optimal management of pulmonary issues in children with this condition is limited.This narrative review presents state-of-the-art evidence regarding the epidemiology, pathophysiology and therapeutic options for chronic respiratory complications commonly seen in paediatric patients with SCD. Furthermore, it highlights the gaps in the current knowledge and indicates future directions for studies that aim to improve our understanding of chronic respiratory complications in children with SCD.

American Society of Hematology 2019 guidelines for sickle cell disease: cardiopulmonary and kidney disease

BACKGROUND

Prevention and management of end-organ disease represent major challenges facing providers of children and adults with sickle cell disease (SCD). Uncertainty and variability in the screening, diagnosis, and management of cardiopulmonary and renal complications in SCD lead to varying outcomes for affected individuals.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about screening, diagnosis, and management of cardiopulmonary and renal complications of SCD.

METHODS

ASH formed a multidisciplinary guideline panel that included 2 patient representatives and was balanced to minimize potential bias from conflicts of interest. The Mayo Evidence-Based Practice Research Program supported the guideline development process, including performing systematic evidence reviews up to September 2017. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE evidence-to-decision frameworks, to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 10 recommendations for screening, diagnosis, and management of cardiopulmonary and renal complications of SCD. Recommendations related to anticoagulation duration for adults with SCD and venous thromboembolism were also developed.

CONCLUSIONS

Most recommendations were conditional due to a paucity of direct, high-quality evidence for outcomes of interest. Future research was identified, including the need for prospective studies to better understand the natural history of cardiopulmonary and renal disease, their relationship to patient-important outcomes, and optimal management.

Differences in lung function between children with sickle cell anaemia from West Africa and Europe

Introduction

Lung function abnormalities are common in sickle cell anaemia (SCA) but data from sub-Saharan Africa are limited. We hypothesised that children with SCA from West Africa had worse lung function than their counterparts from Europe.

Methods

This prospective cross-sectional study evaluated spirometry and anthropometry in black African individuals with SCA (haemoglobin phenotype SS) aged 6–18 years from Nigeria and the UK, when clinically stable. Age-matched controls were also included in Nigeria to validate the Global Lung Initiative spirometry reference values.

Results

Nigerian SCA patients (n=154) had significant reductions in both FEV1 and FVC of ~1 z-score compared with local controls (n=364) and ~0.5 z-scores compared with the UK patients (n=101). Wasting (body mass index z-score<−2) had a prevalence of 27% in Nigerian patients and 7% in the UK ones (p<0.001). Among children with SCA, being resident in Nigeria (OR 2.4, 95% CI 1.1 to 4.9), wasting (OR 2.3, 95% CI 1.1 to 5.0) and each additional year of age (OR 1.2, 95% CI 1.1 to 1.4) were independently associated with increased risk of restrictive spirometry (FVC z-score<−1.64+FEV1/FVC≥−1.64).

Conclusions

This study showed that chronic respiratory impairment is more severe in children with SCA from West Africa than Europe. Our findings suggest the utility of implementing respiratory assessment in African children with SCA to early identify those with chronic lung injury, eligible for closer follow-up and more aggressive therapies.

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

A physicians survey assessing management of pulmonary airway involvement in sickle cell disease

BACKGROUND

Airway involvement in patients with sickle cell disease (SCD) involves recurrent episodes of acute chest syndrome (ACS), co-existent asthma, lower airway obstruction (LAO), or airway hyper-responsiveness/ bronchodilator response (AHR/BDR). With increased recognition that sickle cell (SC) airway inflammation may be distinct from asthma, our aim was to study regional and individual practices among pediatric pulmonologists and elucidate the patient characteristics that determine the diagnosis of asthma or SC airway inflammation.

METHODS

A cross-sectional web-based survey including 6 case scenarios on diagnosis and management of pulmonary manifestations of pediatric SC airway disease was conducted. The case scenarios, combined different risk factors for airway inflammation: history of recurrent ACS, atopy, family history of asthma, LAO, or AHR/BDR, with possible responses including - diagnosis of asthma, SC airway inflammation, both or neither.

RESULTS

Of the 130 responses, 83 were complete. "Asthma" was diagnosed when LAO (OR, 7.96 [4.28, 14.79]; p < 0.001), family history of asthma (OR 18.88 [5.87, 60.7]; p < 0.001), and atopy (OR 3.19 [1.74, 5.8]; p < 0.001) were present. "SC airway inflammation" was diagnosed when ACS (OR 3.95 [2.08, 7.51]; p < 0.001), and restrictive pattern on PFT (OR 3.75 [2.3, 6.09]; p < 0.001) were present in the scenarios. Regardless of the diagnosis, there was a high likelihood of initiating or stepping up inhaled corticosteroid as compared to prescribing montelukast.

CONCLUSION

There is variability in the diagnosis and management of SC airway inflammation among pediatric pulmonologists. This study highlights the need for consensus guidelines to improve management of SC airway inflammation.

Lung function in children with sickle cell disease from Central Africa

Lung function in patients with sickle cell anaemia (SCA) living in sub-Saharan Africa is largely unknown. Anthropometry and spirometry were cross-sectionally evaluated in patients with SCA (HbSS) aged 6–18 years and in schoolchildren from the Democratic Republic of the Congo. The Global Lung Initiative 2012 spirometry reference values were used. A total of 112 patients and 377 controls were included. Twenty-six per cent of patients with SCA had spirometry findings suggestive of a restrictive pattern and 41% had a FEV1 z-score <5th percentile. Wasting, increasing age and female sex were independently associated with increased risk of restrictive spirometry pattern in patients with SCA. Longitudinal studies could clarify the prognostic meaning of these findings.

Pulmonary dysfunction among adolescents and adults with sickle cell disease in Nigeria: Implications for monitoring

BACKGROUND:

Pulmonary complications of sickle cell disease (SCD) contribute to excess morbidity and mortality. The burden of pulmonary dysfunction among Nigerians with SCD has not been well elucidated.

OBJECTIVES:

The objectives of this study are to describe the frequency and pattern of spirometry abnormalities in SCD and to explore the association between pulmonary dysfunction and selected parameters.

METHODS:

A cross-sectional study among adolescents and adults with SCD attending a University Teaching Hospital and healthy age- and gender-matched controls. Respiratory symptoms, oxygen saturation, spirometry, complete blood counts, and fetal hemoglobin (Hb) were measured.

RESULTS:

A total of 245 participants with SCD and 216 controls were included in the study. Frequency of respiratory symptoms was similar between the two groups. The median forced expiratory volume 1 (FEV1), forced vital capacity (FVC), and the FEV1/FVC were significantly lower in SCD as compared to controls (P = 0.000 in all instances). The frequency of abnormal pulmonary patterns was higher in SCD as compared to controls with abnormal spirometry pattern in 174 (71%) and 68 (31.5%) of participants with SCD and controls, respectively (P = 0.000). The suggestive of restrictive pattern was predominant (48% vs. 23%), but obstructive (11.8% vs. 7.4%) and mixed patterns (11% vs. 0.9%) were also found among SCD versus controls. Hb concentration was positively associated with FEV1 and FVC, whereas white cell count and age were negatively associated with FVC and FEV1, respectively.

CONCLUSION:

There is a high burden of pulmonary dysfunction in SCD among Nigerians which may be related to the severity of disease. There is a need for further research to explore the effectiveness of potential interventions so as to harness the benefits from monitoring and early detection.

Airway inflammation in sickle cell disease-A translational perspective

Asthma and sickle cell disease (SCD) are common chronic conditions in children of African ancestry that are characterized by cough, wheeze, and obstructive patterns on pulmonary function. Pulmonary function testing in children with SCD has estimated a prevalence of obstructive lung disease ranging from 13% to 57%, and airway hyper-responsiveness of up to 77%, independent of a diagnosis of asthma. Asthma co-existing with SCD is associated with increased risk of acute chest syndrome (ACS), respiratory symptoms, pain episodes, and death. However, there are inherent differences in the pathophysiology of SCD and asthma. While classic allergic asthma in the general population is associated with a T-helper 2 cell (Th-2 cells) pattern of cell inflammation, increased IgE levels and often positive allergy testing, inflammation in SCD is associated with different inflammatory pathways, involving neutrophilic and monocytic pathways, which have been explored to a limited extent in mouse models and with a dearth of human studies. The current review summarizes the existent literature on sickle cell related airway inflammation and its cross roads with allergic asthma-related inflammation, and discusses the importance of further elucidating and understanding these common and divergent inflammatory pathways in human studies to facilitate development of targeted therapy for children with SCD and pulmonary morbidity.

Age is a predictor of a small decrease in lung function in children with sickle cell anemia

The longitudinal pattern of lung function in children with sickle cell anemia (SCA) has shown a decrease in FEV₁ % predicted, a risk factor for death in adults with SCA, but predictors for this decline are poorly characterized. In a prospective longitudinal multi-center cohort of children with SCA, we tested the hypotheses that: (1) FEV₁ % predicted declines over time; and (2) SCA-specific characteristics and therapy predict this decline. At three clinical centers, children with SCA (HbSS or HbSβ⁰ thalassemia), unselected for respiratory disease, were enrolled in the Sleep and Asthma Cohort (SAC) study. Study-certified pulmonary function technicians performed spirometry and lung volumes. Each assessment was reviewed centrally. Predicted values were determined for TLC, FEV₁ , FVC, and FEV₁ /FVC ratio. A total of 197 participants, mean age 11.0 years at first testing (range 4-19.3 years), had a minimum of three spirometry measurements, over an average of 4.4 years (range 1.1-6.5 years) from baseline to endpoint. In a multivariable model, FEV₁ % predicted declines by 0.3% for every additional year of age (95% CI -0.56 to -0.05, P = .020). Sex, asthma history, hemoglobin, reticulocyte count, white blood cell count, incidence rate of severe acute pain and acute chest syndrome episodes, and hydroxyurea therapy were not associated with a decline in FEV₁ % predicted. In a large, rigorously evaluated, prospective cohort of an unselected group of children with SCA, FEV₁ % predicted declines minimally over an average of 4 years, and none of the examined disease features predict the decline.

Pulmonary function in children and adolescents with sickle cell disease: have we paid proper attention to this problem?

Objective:

To evaluate pulmonary function and functional capacity in children and adolescents with sickle cell disease.

Methods:

This was a cross-sectional study involving 70 children and adolescents (8-15 years of age) with sickle cell disease who underwent pulmonary function tests (spirometry) and functional capacity testing (six-minute walk test). The results of the pulmonary function tests were compared with variables related to the severity of sickle cell disease and history of asthma and of acute chest syndrome.

Results:

Of the 64 patients who underwent spirometry, 15 (23.4%) showed abnormal results: restrictive lung disease, in 8 (12.5%); and obstructive lung disease, in 7 (10.9%). Of the 69 patients who underwent the six-minute walk test, 18 (26.1%) showed abnormal results regarding the six-minute walk distance as a percentage of the predicted value for age, and there was a ≥ 3% decrease in SpO₂ in 36 patients (52.2%). Abnormal pulmonary function was not significantly associated with any of the other variables studied, except for hypoxemia and restrictive lung disease.

Conclusions:

In this sample of children and adolescents with sickle cell disease, there was a significant prevalence of abnormal pulmonary function. The high prevalence of respiratory disorders suggests the need for a closer look at the lung function of this population, in childhood and thereafter.

Cardiorespiratory pathogenesis of sickle cell disease in a mouse model

The nature and development of cardiorespiratory impairments associated with sickle cell disease are poorly understood. Given that the mechanisms of these impairments cannot be addressed adequately in clinical studies, we characterized cardiorespiratory pathophysiology from birth to maturity in the sickle cell disease SAD mouse model. We identified two critical phases of respiratory dysfunction in SAD mice; the first prior to weaning and the second in adulthood. At postnatal day 3, 43% of SAD mice showed marked apneas, anemia, and pulmonary vascular congestion typical of acute chest syndrome; none of these mice survived to maturity. The remaining SAD mice had mild lung histological changes in room air with an altered respiratory pattern, seizures, and a high rate of death in response to hypoxia. Approximately half the SAD mice that survived to adulthood had an identifiable respiratory phenotype including baseline tachypnea at 7–8 months of age, restrictive lung disease, pulmonary hypertension, cardiac enlargement, lower total lung capacity, and pulmonary vascular congestion. All adult SAD mice demonstrated impairments in exercise capacity and response to hypoxia, with a more severe phenotype in the tachypneic mice. The model revealed distinguishable subgroups of SAD mice with cardiorespiratory pathophysiology mimicking the complications of human sickle cell disease.

[Pulmonary complications of sickle cell disease in children]

Acute and chronic pulmonary complications are frequent in sickle cell disease (SCD), with different spectrum and characteristics in children and adults. Chronic hypoxia is frequent and plays a role in several respiratory complications in SCD. Furthermore, hypoxia has been associated with a higher risk of cerebral ischemia. Despite differing oxygen affinity between hemoglobin A and S, standard pulse oximetry was shown to be accurate in diagnosing hypoxia in SCD patients. Whereas acute hypoxia management is similar to non-SCD patients, chronic hypoxia treatment is mainly based on a transfusion program rather than long-term oxygen therapy. Acute chest syndrome (ACS) is the foremost reason for admission to the intensive care unit and the leading cause of premature death. Guidelines on its management have recently been published. Asthma appears to be a different comorbidity and may increase the risk of vaso-occlusive crisis, ACS, and early death. Its management is not specific in SCD, but systemic steroids must be used carefully. Pulmonary hypertension (PH) is a major risk factor of death in adult patients. In children, no association between PH and death has been shown. Elevated tricuspid regurgitant velocity was associated with lower performance on the 6-min walk test (6MWT) but its long-term consequences are still unknown. These differences could be due to different pathophysiology mechanisms. Systematic screening is recommended in children. Regarding lung functions, although obstructive syndrome appears to be rare, restrictive pattern prevalence increases with age in SCD patients. Adaptation to physical exercise is altered in SCD children: they have a lower walking distance at the 6MWT than controls and can experience desaturation during effort, but muscular blood flow regulation maintains normal muscular strength. Sleeping disorders are frequent in SCD children, notably Obstructive sleep apnea syndrome (OSAS). Because of the neurological burden of nocturnal hypoxia, OSAS care is primordial and mainly based on adenotonsillectomy, which has been shown to reduce ischemic events. The high morbidity and mortality related to pulmonary impairments in SCD require a careful pulmonary assessment and follow-up. Mainly based on clinical examination, follow-up aims to the diagnosis of SCD-related respiratory complications early in these children.

Pattern of Lung Function Is Not Associated with Prior or Future Morbidity in Children with Sickle Cell Anemia

RATIONALE

Patient factors associated with development of abnormal lung function in children with sickle cell anemia (SCA) have not been fully characterized.

OBJECTIVES

To characterize lung function abnormalities among children with SCA and to determine whether these steady-state lung function results were associated with morbidity before or after testing among children with SCA.

METHODS

This study was part of the prospective National Institutes of Health-funded Sleep and Asthma Cohort Study. Children with HbSS or Hb Sβ(o) (SCA) were enrolled without regard for sickle cell-related comorbidities or diagnosis of asthma. Lung function was measured by spirometry and plethysmography on the same day, when free of acute disease. Standardized asthma symptom questionnaires and review of the medical records were also performed.

MEASUREMENTS AND MAIN RESULTS

A total of 149 children aged 6 to 19 years completed lung function testing, of whom 139 participants had retrospective morbidity data from birth to the test date, and 136 participants were followed prospectively for a median of 4.3 years from the test date. At baseline, percentages with normal, obstructive, restrictive, nonspecific, and mixed lung function patterns were 70, 16, 7, 6, and 1, respectively. Neither retrospective rates of pain nor acute chest syndrome was associated with lung function patterns. Furthermore, baseline lung function pattern was not predictive of future pain or acute chest syndrome episodes.

CONCLUSIONS

The majority of children with SCA have lung function that is within the normal range. Abnormal lung function patterns were not associated with prior vasoocclusive pain or acute chest syndrome episodes, and baseline lung function patterns did not predict future vasoocclusive pain or chest syndrome episodes.

Longitudinal assessment of lung function in children with sickle cell disease

OBJECTIVES

To prospectively assess longitudinal lung function in children with sickle cell disease (SCD).

WORKING HYPOTHESIS

Lung function in SCD children deteriorates with increasing age and the decline is more marked in younger children who have recently suffered ACS episodes.

STUDY DESIGN

Two prospective longitudinal studies.

PATIENT-SUBJECT SELECTION

Two cohorts of SCD children and age and ethnic matched controls were recruited. Cohort One (47 SCD and 26 controls) had a median age of 8.8 years and follow up of 2 years and Cohort Two (45 SCD and 26 controls) a median age of 10.2 years and follow up of 10 years.

METHODOLOGY

Forced expiratory volume in one second (FEV1 ), vital capacity (VC), forced expiratory flow between 25% and 75% of VC (FEF 25-75 ), total lung capacity (TLC) and residual volume (RV) were measured on two occasions.

RESULTS

In both groups of SCD children, lung function declined significantly, but in neither control group. ACS episodes were more frequent during the follow up period in Cohort One than Cohort Two (P < 0.0001). The rate of decline was greater in Cohort One than Cohort Two for FEV1 (P = 0.008), VC (P = 0.001), FEF25-75 (P = 0.030), TLC (P = 0.004), and RV (P = 0.043). In Cohort Two restrictive abnormalities were more common at follow up (P = 0.006).

CONCLUSIONS

Lung function deteriorated with increasing age in SCD children and the rate of decline was greater in younger children in whom ACS episodes were more common. Pediatr Pulmonol. 2016;51:717-723. © 2015 Wiley Periodicals, Inc.

Lung function, transfusion, pulmonary capillary blood volume and sickle cell disease

Lung function abnormalities occur in children with sickle cell disease (SCD) and may be associated with elevated pulmonary blood volume. To investigate that association, we determined whether blood transfusion in SCD children acutely increased pulmonary capillary blood volume (PCBV) and increased respiratory system resistance (Rrs5). Measurements of Rrs5 and spirometry were made before and after blood transfusion in 18 children, median age 14.2 (6.6-18.5) years. Diffusing capacity for carbon monoxide and nitric oxide were assessed to calculate the PCBV. Post transfusion, the median Rrs5 had increased from 127.4 to 141.3% predicted (p<0.0001) and pulmonary capillary blood volume from 39.7 to 64.1 ml/m2 (p<0.0001); forced expiratory volume in one second (p=0.0056) and vital capacity (p=0.0008) decreased. The increase in Rrs5 correlated with the increase in PCBV (r=0.50, p=0.0493). Increased pulmonary capillary blood volume may at least partially explain the lung function abnormalities in SCD children.

Progression and prognostic indicators of bronchial disease in children with sickle cell disease

PURPOSE

The pulmonary complications of sickle cell disease (SCD) are a leading cause of morbidity and mortality (MacLean et al. Am J Respir Crit Care Med 178:1055-1059, 2008; Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; National Heart, Lung, and Blood Institute, 2009). Despite this recognition, predictive markers of lung dysfunction progression remain elusive (Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; Platt et al. N Engl J Med 330:1639-1644, 1994; Caboot et al. Curr Opin Pediatr 20:279-287, 2008; Field et al. Am J Hematol 83:574-576, 2008; Shirlo et al. Peadiatr Respir Review 12:78-82, 2011). This study was designed describe the longitudinal progression and identify specific markers that influence bronchial disease in SCD.

METHODS

A retrospective, chart review of 89 patients with SCD was conducted. All patients underwent spirometry in conjunction with body plethysmography as part of routine care. Eleven lung function variables were assessed, five of which were selected to establish patterns of normal, obstructive, restrictive, or mixed obstructive-restrictive physiology (Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; Field et al. Am J Hematol 83:574-576, 2008).

RESULTS

In the unadjusted model, forced expiratory volume in one second (FEV1)% of predicted trended downward with age, while total lung capacity (TLC)% of predicted showed a bimodal distribution and carbon monoxide diffusion capacity corrected for hemoglobin (DLCOcor)% of predicted remained stable. Adjusting for acute chest syndrome (ACS) episodes, medication status, and growth velocity (GV), the final model demonstrated that the downward trend between FEV1% of predicted with age was further influenced by the latter two factors.

CONCLUSIONS

Initial decline in FEV1% of predicted is associated with worsening pulmonary dysfunction over time. Independent of ACS episodes, the factors most influential on the progression of FEV1% predicted include the introduction of medications as well as the promotion of adequate prepubertal growth. Efforts to ensure normal prepubertal GV and treatment with bronchodilators, such as short-acting beta(2) agonists and inhaled corticosteroids (ICS), should be considered at an early age to delay progression of pulmonary dysfunction.

Abnormal pulmonary function and associated risk factors in children and adolescents with sickle cell anemia

Obstructive and restrictive pulmonary changes develop in children with sickle cell disease, but reports conflict as to the type of change that predominates. We prospectively performed spirometry, plethysmography, and lung diffusing capacity in 146 children aged 7 to 20 years with hemoglobin SS or Sβ(0)-thalassemia. Nineteen percent of the patients had obstructive physiology as defined according to guidelines of the American Thoracic Society. In addition, 9% had restrictive physiology and 11% had abnormal but not categorized physiology. Increasing age, patient-reported or family-reported history of asthma or wheezing, and higher lactate dehydrogenase concentration were independent predictors of obstruction as reflected in lower forced expiratory volume in the first second/forced vital capacity. In conclusion, abnormal pulmonary function, most often obstructive, is common in children with hemoglobin SS and Sβ(0)-thalassemia. Full pulmonary function testing should be performed in children with hemoglobin SS or Sβ(0)-thalassemia, especially with history of asthma or wheezing and accentuated elevations in hemolytic markers.

Wheezing symptoms and parental asthma are associated with a physician diagnosis of asthma in children with sickle cell anemia

OBJECTIVE

To identify factors associated with asthma associated with increased sickle cell anemia (SCA).

STUDY DESIGN

Children with SCA (N = 187; mean age 9.6 years, 48% male) were classified as having "asthma" based on parent report of physician diagnosis plus prescription of asthma medication (n = 53) or "no asthma" based on the absence of these features (n = 134). Pain and acute chest syndrome (ACS) events were collected prospectively.

RESULTS

Multiple variable logistic regression model identified 3 factors associated with asthma: parent with asthma (P = .006), wheezing causing shortness of breath (P = .001), and wheezing after exercise (P < .001). When ≥2 features were present, model sensitivity was 100%. When none of the features were present, model sensitivity was 0%. When only 1 feature was present, model sensitivity was also 0%, and presence of ≥2 of positive allergy skin tests, airway obstruction on spirometry, and bronchodilator responsiveness did not improve clinical utility. ACS incident rates were significantly higher in individuals with asthma than in those without asthma (incident rate ratio 2.21, CI 1.31-3.76), but pain rates were not (incident rate ratio 1.28, CI 0.78-2.10).

CONCLUSIONS

For children with SCA, having a parent with asthma and specific wheezing symptoms are the best features to distinguish those with and without parent report of a physician diagnosis of asthma and to identify those at higher risk for ACS events. The value of treatment for asthma in the prevention of SCA morbidity needs to be studied.

Lung function in sickle cell disease

Although some of the most severe complications of Sickle Cell Disease (SCD) tend to be acute and severe (e.g. acute chest syndrome, stroke etc.), the chronic ones can be equally debilitating. Prominent among them is the effect that the disease has on lung growth and function. For many years the traditional teaching has been that SCD is associated with the development of a restrictive lung defect. However, there is increasing evidence that this is not a universal finding and that at least during childhood and adolescence, the majority of the patients have a normal or obstructive pattern of lung function. The following article reviews the current knowledge on the effects of SCD on lung growth and function. Special emphasis is given to the controversies among the published articles in the literature and discusses possible causes for these discrepancies.

Reduced forced expiratory flow but not increased exhaled nitric oxide or airway responsiveness to methacholine characterises paediatric sickle cell airway disease

BACKGROUND

Asthma and airway hyper-responsiveness are reportedly more common in children with sickle cell disease (SCD).

AIM

To determine airway responsiveness, airway inflammation and clinical features of asthma in SCD.

METHODS

A prospective, single-centre study of 50 SCD children without overt pulmonary vascular disease and 50 controls. Exhaled nitric oxide (FeNO) and total serum IgE were measured and spirometry and methacholine challenge were performed. The methacholine dose-response slope (DRS) was calculated.

RESULTS

Doctor diagnosis of asthma was made in 7 (14%) SCD versus 12 (24%) control subjects (p=0.203). FeNO levels were similar in SCD and controls (p=0.250), and were higher in those with atopy and an asthma diagnosis (OR 4.33, 95% CI 1.7 to 11.1; p<0.05). zFEV1 (p=0.002) and zFEV1/FVC (p=0.003) but not zFVC (p=0.098) were lower in SCD versus controls. DRS was higher in those with asthma (p=0.006) but not in SCD versus controls (p=0.403). DRS correlated with FeNO and blood eosinophil count in controls but not SCD. In SCD, DRS was higher in those admitted to hospital with respiratory symptoms (n=27) versus those never admitted (n=23) (p=0.046). DRS was similar in those with at least one acute chest syndrome episode (n=12) versus those with none (n=35) (p=0.247).

CONCLUSIONS

SCD children have airflow obstruction despite having minimal evidence of pulmonary vascular disease. Airflow obstruction is not associated with increased methacholine sensitivity or eosinophilic inflammation, at least as judged by FeNO. Airflow obstruction in SCD does not appear to be related to childhood eosinophilic asthma, but its pathophysiology remains ill understood.

Asthma management in sickle cell disease

Asthma is a common comorbid factor in sickle cell disease (SCD). However, the incidence of asthma in SCD is much higher than expected compared to rates in the general population. Whether "asthma" in SCD is purely related to genetic and environmental factors or rather is the consequence of the underlying hemolytic and inflammatory state is a topic of recent debate. Regardless of the etiology, hypoxemia induced by bronchoconstriction and inflammation associated with asthma exacerbations will contribute to a cycle of sickling and subsequent complications of SCD. Recent studies confirm that asthma predisposes to complications of SCD such as pain crises, acute chest syndrome, and stroke and is associated with increased mortality. Early recognition and aggressive standard of care management of asthma may prevent serious pulmonary complications and reduce mortality. However, data regarding the management of asthma in SCD is very limited. Clinical trials are needed to evaluate the effectiveness of current asthma therapy in patients with SCD and coincident asthma, while mechanistic studies are needed to delineate the underlying pathophysiology.

Interpretation of pediatric lung function: impact of ethnicity

RATIONALE

To evaluate the appropriateness of spirometric and plethysmographic reference equations in healthy young children according to ethnic origin.

METHODS

Spirometry data were collated in 400 healthy children (214 Black and 186 White) aged 6-12 years. Of these children, 68 Black and 115 White children also undertook plethysmography. Results were expressed as percent predicted according to commonly used equations for spirometry and plethysmography.

RESULTS

Black children had lower lung function for a given height compared to White children. The magnitude and direction of these differences varied according to specific outcome. In the studied age range (6-12 years) the ethnic-specific Wang equations were adequate for spirometry (mean results approximating 100% predicted in both ethnic groups). By contrast, significant differences were found between observed and % predicted plethysmographic lung volumes according to published equations derived from White children: Among the Black children, function residual capacity (FRC) and total lung capacity (TLC) were on average, 14 and 6% lower than predicted, whereas mean residual volume (RV) and RV/TLC were 4 and 10% higher. Among White children, the Rosenthal equations gave the best fit, with the exception of FRC which was, on average, 9% lower than predicted.

CONCLUSION

Spirometry equations may suffice in Black children; however, interpretation of static lung volumes in Black children is limited due to inappropriate reference equations. More appropriate plethysmographic reference equations that are applicable to all ethnic groups across the entire age range are urgently needed.

Transition and sickle cell disease

Sickle cell disease (SCD), the most common genetic disease screened for in the newborn period, occurs in ~1 in 2400 newborns in the general population and 1 in 400 individuals of African descent in the United States. Despite the relative high prevalence and low pediatric mortality rate of SCD when compared with other genetic diseases or chronic diseases in pediatrics, few evidence-based guidelines have been developed to facilitate the transition from pediatrics to an internal medicine or family practice environment. As with any pediatric transition program, common educational, social, and health systems themes exist to prepare for the next phase of health care; however, unique features characterizing the experience of adolescents with SCD must also be addressed. These challenges include, but are not limited to, a higher proportion of SCD adolescents receiving public health insurance when compared with any other pediatric genetic or chronic diseases; the high proportion of overt strokes or silent cerebral infarcts (~30%) affecting cognition; risk of low high school graduation; and a high rate of comorbid disease, including asthma. Young adults with SCD are living longer; consequently, the importance of transitioning from a pediatric primary care provider to adult primary care physician has become a critical step in the health care management plan. We identify how the primary care physicians in tandem with the pediatric specialist can enhance transition interventions for children and adolescents with SCD.

Understanding the natural progression in %FEV1 decline in patients with cystic fibrosis: a longitudinal study

BACKGROUND

Forced expiratory volume in 1 s as a percentage of predicted (%FEV1) is a key outcome in cystic fibrosis (CF) and other lung diseases. As people with CF survive for longer periods, new methods are required to understand the way %FEV1 changes over time. An up to date approach for longitudinal modelling of %FEV1 is presented and applied to a unique CF dataset to demonstrate its utility at the clinical and population level.

METHODS AND FINDINGS

The Danish CF register contains 70,448 %FEV1 measures on 479 patients seen monthly between 1969 and 2010. The variability in the data is partitioned into three components (between patient, within patient and measurement error) using the empirical variogram. Then a linear mixed effects model is developed to explore factors influencing %FEV1 in this population. Lung function measures are correlated for over 15 years. A baseline %FEV1 value explains 63% of the variability in %FEV1 at 1 year, 40% at 3 years, and about 30% at 5 years. The model output smooths out the short-term variability in %FEV1 (SD 6.3%), aiding clinical interpretation of changes in %FEV1. At the population level significant effects of birth cohort, pancreatic status and Pseudomonas aeruginosa infection status on %FEV1 are shown over time.

CONCLUSIONS

This approach provides a more realistic estimate of the %FEV1 trajectory of people with chronic lung disease by acknowledging the imprecision in individual measurements and the correlation structure of repeated measurements on the same individual over time. This method has applications for clinicians in assessing prognosis and the need for treatment intensification, and for use in clinical trials.

Lower airway nitric oxide is increased in children with sickle cell disease

OBJECTIVES

To determine alveolar and airways nitric oxide (NO) levels in children with sickle cell disease (SCD).

STUDY DESIGN

Multiple flows fractional exhaled NO (FE(NO)), bronchial NO flux (J'aw(NO)), and alveolar NO concentration (Ca(NO)) were determined prospectively in 16 non-atopic children with SCD in a tertiary ambulatory clinic and compared with those in 10 children with primary ciliary dyskinesia and 22 healthy control subjects. Differences in FE(NO), J'aw(NO), and Ca(NO) were compared with mixed model analysis and Mann-Whitney tests.

RESULTS

Children with SCD had reference range FE(NO) at 50 mL/sec, but FE(NO) was elevated across all flows compared with healthy control subjects (mean difference=2.10±0.91 parts per billion, P=.03). Subjects with SCD had increased J'aw(NO) (1177±533 picoliters per second versus 833±343 picolitres per second, P=.03), and Ca(NO) was no different from control subjects. In contrast, children with primary ciliary dyskinesia had decreased FE(NO) (mean difference=3.36±1.24 parts per billion, P<.01) and J'aw(NO) (507±259 picoliters per second versus 833±343 picoliters per second, P<.01).

CONCLUSIONS

Lower airways NO is increased in children with SCD. Elevation of J'aw(NO) may represent dysregulation of NO metabolism or subclinical airways inflammation.

Allogeneic cellular and autologous stem cell therapy for sickle cell disease: 'whom, when and how'

Sickle cell disease (SCD) is an autosomal recessive inherited hematological disorder characterized by chronic hemolysis and vaso-occlusion, resulting in multiorgan dysfunction and premature death. The only known curative therapy for patients with severe SCD is myeloablative conditioning and allo-SCT from HLA-matched sibling donors. In this state of the art review, we discuss current and future considerations including patient selection/eligibility, intensity of conditioning regimens, allogeneic graft sources, graft manipulation, mixed donor chimerism, organ function and stability and autologous gene correction stem cell strategies. Recent novel approaches to promote mixed donor chimerism have included the use of matched unrelated adult donors, umbilical cord blood donors, haploidentical familial donors and the utilization of nonmyeloablative, such as reduced intensity and reduced toxicity conditioning regimens. Future strategies will include gene therapy and autologous gene correction stem cell designs. Prospects are bright for novel stem and cellular approaches for patients with severe SCD, and we are currently at the end of the beginning for utilizing cellular therapeutics for the curative treatment of this chronic and debilitating condition.

Primary Prophylaxis in Sickle Cell Disease: Is It Feasible? Is It Effective?

Consideration of primary prophylaxis to prevent complications of sickle cell disease (SCD) requires a clear understanding of the earliest manifestations of SCD-related organ injury, a reliable clinical or laboratory tool to detect organ dysfunction, and evidence that an intervention instituted in the presymptomatic state can mitigate disease progression. This review examines the pathophysiology of SCD in organs that may be potential targets for intervention, our current capacity to evaluate early SCD manifestations, results of clinical trials, and opportunities for future interventions.