Factors associated with dyspnea in adult patients with sickle cell disease

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.

Testes Ergométricos em Pacientes com Anemia Falciforme: Segurança, Viabilidade e Possíveis Implicações no Prognóstico

Fundamento

Pacientes com anemia falciforme (AF) têm risco aumentado de complicações cardiovasculares. O teste ergométrico é usado como marcador de prognóstico em uma série de doenças cardiovasculares. Entretanto, há uma escassez de evidências sobre exercícios em pacientes com AF, especialmente em relação à sua segurança, viabilidade e possível função prognóstica.

Objetivos

Usamos o teste em esteira máximo para determinar a segurança e a viabilidade do teste ergométrico em pacientes com AF. Além disso, os fatores associados à duração do exercício, bem como o impacto das alterações causadas pelo exercício em resultados clínicos, também foram avaliados.

Métodos

113 pacientes com AF que passaram pelo teste ergométrico e por uma avaliação cardiovascular abrangente incluindo um ecocardiograma e os níveis do peptídeo natriurético do tipo B (BNP). O desfecho de longo prazo foi uma combinação de eventos incluindo morte, crises álgicas graves, síndrome torácica aguda ou internações hospitalares por outras complicações associadas â doença falciforme. A análise de regressão de Cox foi realizada para identificar as variáveis associadas ao resultado. Um p valor <0,05 foi considerado estatisticamente significativo.

Resultados

A média de idade foi de 36 ± 12 anos (intervalo, 18-65 anos), e 62 pacientes eram do sexo feminino (52%). A presença de alterações isquêmicas ao esforço e resposta pressórica anormal ao exercício foram detectadas em 17% e 9 % da´população estudada respectivamente. Dois pacientes apresentaram crise álgica com necessidade de internação hospitalar no período de 48 horas da realização do exame. Fatores associados à duração do exercício foram idade, sexo, velocidade máxima de regurgitação tricúspide (RT), e relação E/e’, após a padronização quanto aos marcadores da gravidade da doença. Durante o período médio de acompanhamento de 10,1 meses (variando de 1,2 a 26), 27 pacientes (23%) apresentaram desfechos clínicos adversos. Preditores independentes de eventos adversos foram a concentração de hemoglobina, velocidade do fluxo transmitral tardio (onda A), e a resposta da PA ao exercício.

Conclusões

A realização de testes ergométricos em pacientes com AF, clinicamente estáveis, é viável. A duração do exercício estava associada à função diastólica e a pressão arterial pulmonar. A resposta anormal da PA foi um preditor independente de eventos adversos.

Muscle structural, energetic and functional benefits of endurance exercise training in sickle cell disease

Sickle cell disease (SCD) patients display skeletal muscle hypotrophy, altered oxidative capacity, exercise intolerance and poor quality of life. We previously demonstrated that moderate-intensity endurance training is beneficial for improving muscle function and quality of life of patients. The present study evaluated the effects of this moderate-intensity endurance training program on skeletal muscle structural and metabolic properties. Of the 40 randomized SCD patients, complete data sets were obtained from 33. The training group (n = 15) followed a personalized moderate-intensity endurance training program, while the non-training (n = 18) group maintained a normal lifestyle. Biopsies of the vastus lateralis muscle and submaximal incremental cycling tests were performed before and after the training program. Endurance training increased type I muscle fiber surface area (P = .038), oxidative enzyme activity [citrate synthase, P < .001; β-hydroxyacyl-CoA dehydrogenase, P = .009; type-I fiber cytochrome c oxidase, P = .042; respiratory chain complex IV, P = .017] and contents of respiratory chain complexes I (P = .049), III (P = .005), IV (P = .003) and V (P = .002). Respiratory frequency, respiratory exchange ratio, blood lactate concentration and rating of perceived exertion were all lower at a given submaximal power output after training vs non-training group (all P < .05). The muscle content of proteins involved in glucose transport and pH regulation were unchanged in the training group relative to the non-training group. The moderate-intensity endurance exercise program improved exercise capacity and muscle structural and oxidative properties. This trial was registered at www.clinicaltrials.gov as #NCT02571088.

Effects of home-based inspiratory muscle training on sickle cell disease (SCD) patients

Introduction

Inspiratory muscle training (IMT) has been shown to be an efficient method of improving exercise tolerance and inspiratory and expiratory muscle strength in several diseases. The effects of IMT on patients with sickle cell anemia (SCD) are relatively unknown. Our study aimed to evaluate the effects of IMT on adult SCD patients, regarding respiratory muscle strength (RMS) variables, lung function, exercise tolerance, blood lactation concentration, limitation imposed by dyspnea during daily activities and impact of fatigue on the quality of life.

Methods

This was a randomized single-blind study, with an IMT design comprising true load (TG) and sham load (SG) groups. Initial assessment included spirometry, volumetric capnography (VCap) and measurement of RMS by maximal inspiratory and expiratory pressure (PImax and PEmax). The Medical Research Council dyspnea scale and modified fatigue impact scale were also applied and blood lactate concentration was measured before and after the 6-minute walk test. After this initial assessment, the patient used the IMT device at home daily, returning every 6 weeks for RMS reassessment. Both groups used the same device and were unaware of which group they were in. After a period totaling 18 weeks, patients underwent the final evaluation, as initially performed.

Results

Twenty-five patients in total participated until the end of the study (median age 42 years). There were no significant differences between TG and SG based on age, sex, body mass index or severity of genotype. At the end of the training, both groups showed a significant increase in PEmax and PImax, improvement in Vcap and in exercise tolerance and dyspnea reduction while performing daily life activities. The same was observed in patients grouped according to disease severity (HbSS and HbSβ⁰vs HbSC and HbSβ⁺), without differences between groups.

Conclusion

Home-based inspiratory muscle training benefits outpatients with SCD, including the sham load group.

Trial registration

http://www.ensaiosclinicos.gov.br; registration number: RBR-6g8n92.

Beneficial effects of endurance exercise training on skeletal muscle microvasculature in sickle cell disease patients

Sickle cell disease (SCD) is a genetic hemoglobinopathy leading to 2 major clinical manifestations: severe chronic hemolytic anemia and iterative vaso-occlusive crises. SCD is also accompanied by profound muscle microvascular remodeling. The beneficial effects of endurance training on microvasculature are widely known. The aim of this study was to evaluate the effects of an endurance training program on microvasculature of skeletal muscle in SCD patients. A biopsy of the vastus lateralis muscle and submaximal incremental exercise was performed before and after the training period. Of the 40 randomized SCD patients, complete data sets from 32 patients were obtained. The training group (n = 15) followed a personalized moderate-intensity endurance training program, while the nontraining (n = 17) group maintained a normal lifestyle. Training consisted of three 40-minute cycle ergometer exercise sessions per week for 8 weeks. Histological analysis highlighted microvascular benefits in the training SCD patients compared with nontraining patients, including increases in capillary density (P = .003), number of capillaries around a fiber (P = .015), and functional exchange surface (P < .0001). Conversely, no significant between-group difference was found in the morphology of capillaries. Indexes of physical ability also improved in the training patients. The moderate-intensity endurance exercise training program improved the muscle capillary network and partly reversed the microvascular defects commonly observed in skeletal muscle of SCD patients. This trial was registered at www.clinicaltrials.gov as #NCT02571088.

Salbutamol Worsens the Autonomic Nervous System Dysfunction of Children With Sickle Cell Disease

Background

Sickle cell disease (SCD) patients with asthma have an increased rate of vaso-occlusive crisis (VOC) and acute chest syndrome (ACS) episodes when compared to those without asthma. We hypothesized that either asthma diagnosis or bronchodilator treatment might aggravate SCD via their modulating effect on the autonomic nervous system (ANS).

Methods

Cross-sectional evaluation of heart rate variability (HRV) during pulmonary function tests, including salbutamol administration, in children with SCD receiving asthma treatment or not when compared to asthmatic children without SCD matched for ethnicity.

Results

SCD children with asthma (n = 30, median age of 12.9 years old) were characterized by a reduced FEV₁/FVC ratio, an increased bronchodilator response, and a greater incidence of VOC and ACS when compared to SCD children without asthma (n = 30, 12.7 years). Children with asthma without SCD (n = 29, 11.4 years) were characterized by a higher exhaled NO fraction than SCD children. SCD children when compared to non-SCD children showed reduced HRV [total power, low (LF) and high (HF, vagal tone) frequencies], which was further worsened by salbutamol administration in all the groups: reduction in total power and HF with an increase in LF/HF ratio. After salbutamol, the LF/HF ratio of the SCD children was higher than that of the non-SCD children. The two groups of SCD children were similar, suggesting that asthma diagnosis per se did not modify ANS functions.

Conclusion

SCD children are characterized by impaired parasympathetic control and sympathetic overactivity that is worsened by salbutamol administration.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04062409.

Physiological Evaluation for Endurance Exercise Prescription in Sickle Cell Disease

PURPOSE

Although strenuous exercise may expose sickle cell disease (SCD) patients to risks of vaso-occlusive crisis, evidence suggests that regular endurance exercise may be beneficial. This study aimed to test (i) the safety and usefulness of a submaximal incremental exercise in evaluating physical ability of SCD patients and identify a marker for the management of endurance exercise and (ii) the feasibility of endurance exercise sessions in SCD patients.

METHODS

Twenty adults with SCD (12 men and 8 women) performed a submaximal incremental exercise used to determine the first lactate threshold (LT1) and stopped as soon as blood lactate concentration ([lactate]b) reached ≥4 mmol·L. Fifteen of those patients (8 men and 7 women) also performed three 30-min endurance exercise sessions at ~2.5 mmol·L of [lactate]b on separate occasions.

RESULTS

LT1 occurred at 47 ± 3 and 33 ± 3 W for men and women, respectively, demonstrating the extreme deconditioning and, thus, low physical ability of adult SCD patients. During endurance exercise, peripheral oxygen saturation and [lactate]b most often remained stable and within acceptable ranges.

CONCLUSIONS

The proposed strategy of submaximal incremental exercise allowed safe determination of LT1, an important parameter of patients' physical ability. The study also demonstrated the feasibility and safety of individually tailored endurance exercises at ~2.5 mmol·L of [lactate]b. These latter results suggest that endurance training programs may be considered for adult SCD patients and that the method proposed here may be helpful in that regard.

Clinical phenotypes and outcomes of precapillary pulmonary hypertension of sickle cell disease

Rationale

Precapillary pulmonary hypertension (PH) is a devastating complication of sickle cell disease (SCD). Little is known about the influence of the SCD genotype on PH characteristics.

Objectives

To describe clinical phenotypes and outcomes of precapillary PH due to SCD according to disease genotype.

Methods

A nationwide multicentre retrospective study including all patients with SCD-related precapillary PH from the French PH Registry was conducted. Clinical characteristics and outcomes according to SCD genotype were analysed.

Results

58 consecutive SCD patients with precapillary PH were identified, of whom 41 had homozygous for haemoglobin S (SS) SCD, three had S-β0 thalassaemia (S-β0 thal) and 14 had haemoglobin SC disease (SC). Compared to SC patients, SS/S-β0 thal patients were characterised by lower 6-min walk distance (p=0.01) and lower pulmonary vascular resistance (p=0.04). Mismatched segmental perfusion defects on lung scintigraphy were detected in 85% of SC patients and 9% of SS/S-β0 thal patients, respectively, and 50% of SS/S-β0 thal patients had heterogeneous lung perfusion without segmental defects. After PH diagnosis, 31 patients (53%) received medical therapies approved for pulmonary arterial hypertension, and chronic red blood cell exchange was initiated in 23 patients (40%). Four patients were managed for chronic thromboembolic PH by pulmonary endarterectomy (n=1) or balloon pulmonary angioplasty (n=3). Overall survival was 91%, 80% and 60% at 1, 3 and 5 years, respectively, without influence of genotype on prognosis.

Conclusions

Patients with precapillary PH related to SCD have a poor prognosis. Thrombotic lesions appear as a major component of PH related to SCD, more frequently in SC patients.

How I treat hypoxia in adults with hemoglobinopathies and hemolytic disorders

Hemoglobinopathies are caused by genetic mutations that result in abnormal hemoglobin molecules, resulting in hemolytic anemia. Chronic complications involving the lung parenchyma, vasculature, and cardiac function in hemoglobinopathies result in impaired gas exchange, resulting in tissue hypoxia. Hypoxia is defined as the deficiency in the amount of oxygen reaching the tissues of the body and is prevalent in patients with hemoglobinopathies, and its cause is often multifactorial. Chronic hypoxia in hemoglobinopathies is often a sign of disease severity and is associated with increased morbidity and mortality. Therefore, a thorough understanding of the pathophysiology of hypoxia in these disease processes is important in order to appropriately treat the underlying cause and prevent complications. In this article, we discuss management of hypoxia based on three different cases: sickle cell disease, β-thalassemia, and hereditary spherocytosis. These cases are used to review the current understanding of the disease pathophysiology, demonstrate the importance of a thorough clinical history and physical examination, explore diagnostic pathways, and review the current management.

Respiratory resistance and reactance in adults with sickle cell anemia: Correlation with functional exercise capacity and diagnostic use

BACKGROUND

The improvement in sickle cell anemia (SCA) care resulted in the emergence of a large population of adults living with this disease. The mechanisms of lung injury in this new population are largely unknown. The forced oscillation technique (FOT) represents the current state-of-the-art in the assessment of lung function. The present work uses the FOT to improve our knowledge about the respiratory abnormalities in SCA, evaluates the associations of FOT with the functional exercise capacity and investigates the early detection of respiratory abnormalities.

METHODOLOGY/PRINCIPAL FINDINGS

Spirometric classification of restrictive abnormalities resulted in three categories: controls (n = 23), patients with a normal exam (n = 21) and presenting pulmonary restriction (n = 24). FOT analysis showed that, besides restrictive changes (reduced compliance; p<0.001), there is also an increase in respiratory resistance (p<0.001) and ventilation heterogeneity (p<0.01). FOT parameters are associated with functional exercise capacity (R = -0.38), pulmonary diffusion (R = 0.66), respiratory muscle performance (R = 0.41), pulmonary volumes (R = 0.56) and airway obstruction (R = 0.54). The diagnostic accuracy was evaluated by investigating the area under the receiver operating characteristic curve (AUC). A combination of FOT and machine learning (ML) classifiers showed adequate diagnostic accuracy in the detection of early respiratory abnormalities (AUC = 0.82).

CONCLUSIONS

In this study, the use of FOT showed that adults with SCA develop a mixed pattern of respiratory disease. Changes in FOT parameters are associated with functional exercise capacity decline, abnormal pulmonary mechanics and diffusion. FOT associated with ML methods accurately diagnosed early respiratory abnormalities. This suggested the potential utility of the FOT and ML clinical decision support systems in the identification of respiratory abnormalities in patients with SCA.

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.

Relationship between ventilation heterogeneity and exercise intolerance in adults with sickle cell anemia

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 (SIII_N2). Compared with adults with lower SIII_N2 values, adults with higher SIII_N2 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). SIII_N2 values correlated significantly with hemoglobin (r_s=-0.344; P=0.034), forced vital capacity (r_s=-0.671; P<0.0001), diffusing capacity for carbon monoxide (r_s=-0.376; P=0.019), 6MWD (r_s=-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.

Dense red blood cell and oxygen desaturation in sickle-cell disease

Production of abnormal hemoglobin (HbS) in sickle-cell disease (SCD) results in its polymerization in deoxygenated conditions and in sickled-RBC formation. Dense RBCs (DRBCs), defined as density >1.11 and characterized by increased rigidity are absent in normal AA subjects, but present at percentages that vary of a patient to another remaining stable throughout adulthood for each patient. Polymerized HbS has reduced affinity for oxygen, demonstrated by the rightward shift of the oxygen-dissociation curve, leading to disturbances in oxygen transport. Ninety-two SCD patients' total RBCs were separated into LightDRBC (LRBC) (d < 1.11 g/mL) and DRBC fractions. Venous blood partial oxygen pressure and RBC-fraction-deoxygenation and -reoxygenation Hb-oxygen-equilibrium curves were determined. All patients took a 6-minute walking test (6MWT); 10 had results before and after >6 months on hydroxyurea. 6MWT time with SpO2  < 88% (TSpO2  < 88) assessed the physiological impact of exertion. Elevated mean corpuscular hemoglobin (Hb) concentrations, decreased %HbF, and 2,3-bisphosphoglycerates in DRBCs modulated Hb-oxygen affinity. Deoxygenation and reoxygenation Hb-oxygen equilibrium curves differed between normal Hb AA and SS RBCs and between LRBCs and DRBCs, with rightward shifts confirming HbS-polymerization's role in affinity loss. In bivariate analyses, 50% Hb saturation correlated positively with %DRBCs (P < 0.0001, r(2)  = 0.34) and negatively with %HbF (P < 0.0001, r(2)  = 0.25). The higher the %DRBCs, the longer the TSpO2 88 (P = 0.04). Hydroxyurea was associated with significantly shorter TSpO2  < 88 (P = 0.01). We report that the %DRBCs directly affects SCD patients' SpO2 during exertion; hydroxyurea improves oxygen affinity and lowers the %DRBCs. Am. J. Hematol. 91:1008-1013, 2016. © 2016 Wiley Periodicals, Inc.

Treatment of 100 chronic thalassemic leg wounds by plasma-rich platelets

OBJECTIVE

Thalassemia is a heterogeneous group of congenital hemoglobinopathies caused by mutations in the globin gene complex that result in an unbalanced globin synthesis. Unmatched globin chains bind to the cytosolic surface of red blood cell membrane where they cause oxidative damage that might in part be responsible for membrane weakness. The deformability of red blood cells and hypercoagulable state in thalassemic patients have been incriminated in leg ulcer formation, as this might cause ischemia to the skin and consequently friability and ulceration.

METHODS

Platelet-rich plasma (PRP) gel is considered an advanced wound therapy for chronic and acute wounds. PRP gel consists of cytokines, growth factors, chemokines, and a fibrin scaffold derived from a patient's blood. In this study, we treated 100 thalassemic leg wounds using PRP.

RESULTS

There was wound size reduction in patients after 4 weeks of treatment. In wounds with 2-3.5 cm² surface area, complete closure happened after 12.5 weeks, 5-12 cm² wounds completely closed after 13.2 weeks, and finally, 4.5-6 cm² wounds healed completely after 14 weeks. None of the wounds reopened after 8 months of monitoring.

CONCLUSION

This study will help extrapolation of the use of PRP for at least thalassemic leg wound treatment.

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.

Predictive models of six-minute walking distance in adults with sickle cell anemia: Implications for rehabilitation

BACKGROUND

Sickle cell anemia (SCA) is characterized by a broad spectrum of abnormalities that affect most body organs and systems. To date, there is few data on the influence of these patients' clinical characteristics on the functional exercise capacity.

AIM

To investigate the effect of the clinical complications on the functional exercise capacity of adult SCA patients.

METHOD

Cross-sectional study, where 45 SCA patients underwent clinical evaluations, echocardiography, pulmonary function testing, and determination of six-minute walking distance (6MWD).

RESULTS

A significant correlation (P < 0.001) was found between 6MWD and hemoglobin (Hb) level, tricuspid regurgitation velocity, forced vital capacity, acute chest syndrome, and diffusing capacity for carbon monoxide. The prediction model for 6MWD explained 67% of the 6MWD variability (P < 0.001).

CONCLUSIONS

Hemodynamics, cardiovascular function, pulmonary function, and episodes of acute lung injury seem to impact the 6MWD in adults with SCA.

Time-based understanding of DLCO and DLNO

Capture of CO and NO by blood requires molecules to travel by diffusion from alveolar gas to haemoglobin molecules inside RBCs and then to react. One can attach to these processes two times, a time for diffusion and a time for reaction. This reaction time is known from chemical kinetics and, therefore, constitutes a unique physical clock. This paper presents a time-based bottom-up theory that yields a simple expression for DLCO and DLNO that produces quantitative predictions which compare successfully with experiments. Specifically, when this new approach is applied to DLCO experiments, it can be used to determine the value of the characteristic diffusion time, and the value of capillary volume (Vc). The new theory also provides a simple explanation for still unexplained correlations such as the observed proportionality between the so-called membrane conductance DM and Vc of Roughton and Forster's interpretation. This new theory indicates that DLCO should be proportional to the haematocrit as found in several experiments.

Relationship between pulmonary and cardiac abnormalities in sickle cell disease: implications for the management of patients

Objective

To evaluate the association between clinical, pulmonary, and cardiovascular findings in patients with sickle cell disease and, secondarily, to compare these findings between sickle cell anemia patients and those with other sickle cell diseases.

Methods

Fifty-nine adults were included in this cross-sectional study; 47 had sickle cell anemia, and 12 had other sickle cell diseases. All patients underwent pulmonary function tests, chest computed tomography, and echocardiography.

Results

Abnormalities on computed tomography, echocardiography, and pulmonary function tests were observed in 93.5%, 75.0%; and 70.2% of patients, respectively. A higher frequency of restrictive abnormalities was observed in patients with a history of acute chest syndrome (85% vs. 21.6%; p-value < 0.0001) and among patients with increased left ventricle size (48.2% vs. 22.2%; p-value = 0.036), and a higher frequency of reduced respiratory muscle strength was observed in patients with a ground-glass pattern (33.3% vs. 4.3%; p-value = 0.016). Moreover, a higher frequency of mosaic attenuation was observed in patients with elevated tricuspid regurgitation velocity (61.1% vs. 24%; p-value = 0.014). Compared to patients with other sickle cell diseases, sickle cell anemia patients had suffered increased frequencies of acute pain episodes, and acute chest syndrome, and exhibited mosaic attenuation on computed tomography, and abnormalities on echocardiography.

Conclusion

A significant interrelation between abnormalities of the pulmonary and cardiovascular systems was observed in sickle cell disease patients. Furthermore, the severity of the cardiopulmonary parameters among patients with sickle cell anemia was greater than that of patients with other sickle cell diseases.

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.

Lung function and six-minute walk test performance in individuals with sickle cell disease

Background

Sickle Cell Disease (SCD), which is characterized by a mutation in the gene encoding beta hemoglobin, causes bodily dysfunctions such as impaired pulmonary function and reduced functional capacity.

Objective

To assess changes in pulmonary function and functional capacity in patients with SCD and to identify the relationships between these variables.

Method

We evaluated sociodemographic, anthropometric, lung function (spirometry), respiratory (manovacuometer), peripheral muscle strength (Handgrip strength - HS) and functional capacity (i.e., the six-minute walk test) parameters in 21 individuals with SCD (average age of 29±6 years). Shapiro-Wilk, paired Student's, Wilcoxon, Pearson and Spearman correlation tests were used for statistical analyses, and the significance threshold was set at p<0.05.

Results

A total of 47.6% of the study subjects exhibited an altered ventilation pattern, 42.8% had a restrictive ventilatory pattern (RVP) and 4.8% exhibited a mixed ventilatory pattern (MVP). The observed maximal inspiratory pressure (MIP) values were below the predicted values for women (64 cmH₂O), and the maximum expiratory pressure (MEP) values, HS values and distance walked during the 6MWT were below the predicted values for both men (103 cmH₂O, 39 Kgf and 447 m, respectively) and women (64 cmH₂O; 27 Kgf; 405 m, respectively). Positive correlations were observed between maximum voluntary ventilation (MVV) and MEP (r=0.4; p=0.046); MVV and BMI (r=0.6; p=0.003); and between HS and MIP (r=0.7; p=0.001), MEP (r=0.6; p=0.002), MVV (r=0.5; p=0.015), distance walked in the 6MWT (r=0.4; p=0.038) and BMI (r=0.6; p=0.004).

Conclusions

SCD promoted changes in lung function and functional capacity, including RVPs and a reduction in the distance walked in the 6MWT when compared to the predictions. In addition, significant correlations between the variables were observed.

Airways obstruction and pulmonary capillary blood volume in children with sickle cell disease

OBJECTIVES AND WORKING HYPOTHESIS

Airways obstruction occurs in young children with sickle cell disease (SCD). Our aim was to test the hypothesis that increased pulmonary capillary blood volume at least in part explained the increased airways obstruction as this would inform which therapy might be most appropriate to treat the airway obstruction.

STUDY DESIGN

Observational study.

PATIENT-SUBJECT SELECTION

Twenty-five SCD children and 25 ethnic origin matched controls were recruited.

METHODOLOGY

Respiratory system resistance, using impulse oscillometry at 5 Hz (R5 %pred), pulmonary capillary blood volume (Vc), alveolar volume (VA), and spirometry were assessed before and after bronchodilator (ipratropium bromide). Lung volume measurements were also made.

RESULTS

The SCD children compared to the controls had a higher R5 %pred before (median 133 (range 88-181)% vs. 102 (83-184)%, P = 0.0046) and after (105 (79-150)% vs. 91 (64-147)%, P = 0.0489) bronchodilator and their median Vc/VA (ml/L) was higher before (26 (18-38) vs. 18 (14-28) P < 0.0001) and after (26 (19-41) vs. 18 (13-27) P < 0.0001) bronchodilator. There were similar decreases in R5 %pred post-bronchodilator in the two groups, but no significant changes in Vc/VA in either group. Vc/VA correlated significantly with R5 %pred in the SCD children only.

CONCLUSIONS

Increased pulmonary capillary blood volume contributes to the increased airways obstruction in children with SCD, hence, bronchodilators may be of limited benefit in reducing their airways obstruction.

Pulmonary function, CT and echocardiographic abnormalities in sickle cell disease

OBJECTIVES

To test the hypothesis that vascular abnormalities on high-resolution CT (HRCT) would be associated with echocardiographic changes and lung function abnormalities in patients with sickle cell disease (SCD) and the decline in lung function seen in SCD patients.

METHODS

HRCT, echocardiography and lung function assessments were made in 35 adults, 20 of whom had previously been assessed a median of 6.6 years prior to this study. The pulmonary arterial dimensions on HRCT were quantified as the mean segmental pulmonary artery/bronchus (A/B) ratio and the summated cross-sectional area of all pulmonary vessels <5 mm in diameter (cross-sectional area (CSA)<5 mm%).

RESULTS

The segmental A/B ratio was negatively correlated with FEV1, vital capacity (VC), forced expiratory flow between 25% and 75% of VC (FEF25/75) and arterial oxygen saturation (SpO2) and positively with the residual volume: total lung capacity ratio (RV:TLC) and respiratory system resistance (Rrs). CSA<5 mm% was negatively correlated with FEV1, FEF25/75 and SpO2 and positively with RV, RV:TLC and respiratory system resistance (Rrs). There were significant correlations between cardiac output assessed by echocardiography and the segmental A/B ratio and CSA<5 mm%. Lung function (FEV1 p=0.0004, VC p=0.0347, FEF25/75 p=0.0033) and the segmental A/B ratio (p=0.0347) and CSA<5 mm% (p<0.0001) significantly deteriorated over the follow-up period.

CONCLUSIONS

Abnormalities in pulmonary vascular volumes may explain some of the lung function abnormalities and the decline in lung function seen in adults with SCD.

Recurrent, severe wheezing is associated with morbidity and mortality in adults with sickle cell disease

Prior studies of asthma in children with sickle cell disease (SCD) were based on reports of a doctor-diagnosis of asthma with limited description of asthma features. Doctor-diagnoses of asthma may represent asthma or wheezing unrelated to asthma. Objectives of this study were to determine if asthma characteristics are present in adults with a doctor-diagnosis of asthma and/or wheezing, and to examine the relationship between doctor-diagnosis of asthma, wheezing and SCD morbidity. This was an observational cohort study of 114 adults with SCD who completed respiratory symptom questionnaires and had serum IgE measurements. A subset of 79 participants completed pulmonary function testing. Survival analysis was based on a mean prospective follow-up of 28 months and data were censored at the time of death or loss to follow-up. Adults reporting a doctor-diagnosis of asthma (N = 34) were more likely to have features of asthma including wheeze, eczema, family history of asthma, and an elevated IgE level (all P < 0.05). However, there was no difference in pain or ACS rate, lung function, or risk of death between adults with and without a doctor-diagnosis of asthma. In contrast, adults who reported recurrent, severe episodes of wheezing (N = 34), regardless of asthma, had twice the rates of pain and ACS, decreased lung function and increased risk of death compared with adults without recurrent, severe wheezing. Asthma features were not associated with recurrent, severe wheezing. Our data suggest that wheezing in SCD may occur independently of asthma and is a marker of disease severity.

Mild haemorheological changes induced by a moderate endurance exercise in patients with sickle cell anaemia

The levels and duration of physical activity that can be considered as completely safe in patients with sickle cell anaemia (SCA) is unknown. The present study compared the haemorheological and haematological profile, cell density distribution and basic biochemistry between a group of 17 patients with SCA and 21 healthy subjects before and after a 20 min duration submaximal cycling exercise at the same absolute workload. Blood was sampled at rest and 3 min after the end of exercise for measurement of biological parameters. Exercise did not affect the haematocrit and blood viscosity in the two groups. Plasma viscosity was not different between the two groups at rest and similarly increased with exercise. The proportion of intermediary dense cells (with density between 1·11 and 1·12 g/ml) decreased with exercise in the SCA group resulting in an increase in the proportion of red blood cells with a density >1·12 g/ml. No change was observed in the control group. The present study suggests that mild-moderate exercise is not very harmful for SCA patients. The haemorheological and haematological changes were very mild, except for the formation of dense cells but no clinically significant signs of medical complication were present in any of the patients.

Death due to asthma in two adolescents with sickle cell disease

In one prospective cohort study, a diagnosis of asthma was associated with an increased risk of mortality in individuals with sickle cell anemia or HbSS. However, a direct relationship between death and asthma exacerbation could not be documented. This report examines two adolescents with sickle cell disease (SCD) who died during worsening symptoms consistent with asthma. Autopsies in both individuals demonstrated pulmonary airway smooth muscle hyperplasia, basement membrane thickening, and eosinophilia, consistent with bronchial asthma. Individuals with SCD and asthma warrant ongoing education, treatment, and surveillance for life-threatening complications of asthma.

A community population survey of prevalence and severity of dyspnea in adults

Given the progress in the symptomatic treatment of breathlessness, and the physical and psychological morbidity associated with chronic breathlessness, estimates of the size of the population that may benefit from better support become imperative. Prevalence estimates have varied widely (0.9% of clinical encounters to 32%) and have largely relied only on respondents who used clinical services. Whole-of-population approaches may be able to define better the "true" prevalence of chronic breathlessness and quantify exertion limited by breathlessness. The aim of this study was to estimate population levels of chronic breathlessness, severity of limits to exercise, and demographic predictors of the presence of breathlessness. A whole-of-population face-to-face survey method (n=8,396) in South Australia was used, directly standardized for age, gender, country of birth, and rurality. Respondents were asked about breathlessness and levels of exertion causing breathlessness for at least three of the last six months using a modified Medical Research Council dyspnea scale. Univariate and multivariate analyses identify the demographic characteristics of people more likely to experience chronic breathlessness. With a participation rate of 65.3%, 8.9% of respondents had breathlessness that chronically limited exertion. Significant associations with chronic breathlessness in multivariate analysis included female sex (P<0.001), not working full time (P<0.001), low income (P=0.007), and older age (P=0.031). There are significant levels of chronic breathlessness in the community. Given the prevalence, it is feasible to explore the onset of breathlessness, the underlying etiologies and subsequent health service utilization, and health consequences.

Fear of Movement (Kinesiophobia), Pain, and Psychopathology in Patients With Sickle Cell Disease

OBJECTIVES

Fear of movement (ie, kinesiophobia) has emerged as a significant predictor of pain-related outcomes including disability and psychologic distress across various types of pain (eg, back pain, headache, fibromyalgia, complex regional pain syndrome). However, no research has examined the prevalence of kinesiophobia in adults with sickle cell disease (SCD). The purpose of this study was to assess the degree of kinesiophobia reported by African American men and women with SCD and to determine whether kinesiophobia is related to pain and psychologic distress in this population.

METHODS

Sixty-seven men and women with SCD recruited from a comprehensive sickle cell treatment program in a large academic medical center completed questionnaires that assess fear of movement, pain and pain interference, and psychologic distress.

RESULTS

Participants reported levels of kinesiophobia (M=30.48, SD=7.55) that were comparable to those obtained for patients with low back pain and fibromyalgia. Although pain levels did not differ by sex, men reported greater kinesiophobia than women (P=0.02). As hypothesized, higher levels of kinesiophobia were associated with greater psychologic distress, particularly Phobic Anxiety (r=0.35), Psychoticism (r=0.29), Somatization (r=0.45), Anxiety (r=0.35), Obsessive-compulsive (r=0.34), Interpersonal Sensitivity (r=0.25), Depression (r=0.29), and all 3 summary indices of the SCL-90-R (all Ps<0.05).

DISCUSSION

Although and historically, pain associated with SCD has not been considered in the context of fear of movement, findings suggest that both kinesiophobia and sex are relevant constructs for consideration in understanding pain-related outcomes in SCD. Though our results require replication, this study suggests that greater kinesiophobia is associated with greater pain and psychologic distress.

Decrease in lung nitric oxide production after peritonitis in mice with sickle cell disease*

OBJECTIVE

Nitric oxide bioavailability may limit the occurrence or severity of acute vaso-occlusive episodes in patients with sickle cell disease. Because sepsis is frequently involved in the initiation of vaso-occlusive crisis and acute chest syndrome, we designed the present study in transgenic (SAD) sickle cell mice to investigate whether acute infectious peritonitis affects the enzymatic balance (nitric oxide synthases/arginases) that governs lung nitric oxide production.

DESIGN

Controlled animal study.

SETTING

Research laboratory of an academic institution.

SUBJECTS

Transgenic Hbbsingle/single SAD1 (SAD) mice and nontransgenic wild-type littermates (C57/Black mice, control group).

INTERVENTIONS

Cecal ligation and puncture-induced peritonitis.

MEASUREMENTS AND MAIN RESULTS

We found that 24 hrs after peritonitis, control littermate mice showed an increase in inducible and endothelial nitric oxide synthase messenger RNA and proteins, together with an increase in exhaled nitric oxide (shift of the balance toward nitric oxide synthesis). In contrast, SAD mice, which showed elevated inducible and endothelial nitric oxide synthase protein expression at baseline, showed a marked decrease in nitric oxide synthase proteins, lung nitric oxide end-products, and exhaled nitric oxide after peritonitis, reflecting a shift of the enzymatic balance toward inhibition of nitric oxide synthesis. Peritonitis increased messenger RNA levels of arginase I and arginase II in controls and SAD mice but with a greater increase in arginase I in SAD than in control mice. Peritonitis was associated with a higher mortality rate at 24 hrs in SAD mice. Inhalation of nitric oxide (40 ppm in air) abolished the mortality rate induced by acute peritonitis in SAD mice.

CONCLUSIONS

Acute peritonitis in SAD mice is associated with a defect in lung nitric oxide production and bioavailability that may participate in the acute systemic and lung vaso-occlusive complications of sickle cell disease.

Abnormal pulmonary function in adults with sickle cell anemia

RATIONALE

Pulmonary complications of sickle cell anemia (Hb-SS) commonly cause morbidity, yet few large studies of pulmonary function tests (PFTs) in this population have been reported.

OBJECTIVES

PFTs (spirometry, lung volumes, and diffusion capacity for carbon monoxide [DLCO]) from 310 adults with Hb-SS were analyzed to determine the pattern of pulmonary dysfunction and their association with other systemic complications of sickle cell disease.

METHODS

Raw PFT data were compared with predicted values. Each subject was subclassified into one of five groups: obstructive physiology, restrictive physiology, mixed obstructive/restrictive physiology, isolated low DLCO, or normal. The association between laboratory data of patients with decreased DLCO or restrictive physiology and those of normal subjects was assessed by multivariate linear regression.

MEASUREMENTS AND MAIN RESULTS

Normal PFTs were present in only 31 of 310 (10%) patients. Overall, adults with Hb-SS were characterized by decreased total lung capacities (70.2 +/- 14.7% predicted) and DLCO (64.5 +/- 19.9%). The most common PFT patterns were restrictive physiology (74%) and isolated low DLCO (13%). Decreased DLCO was associated with thrombocytosis (p = 0.05), with hepatic dysfunction (elevated alanine aminotransferase; p = 0.07), and a trend toward renal dysfunction (elevated blood urea nitrogen and creatinine; p = 0.05 and 0.07, respectively).

CONCLUSIONS

Pulmonary function is abnormal in 90% of adult patients with Hb-SS. Common abnormalities include restrictive physiology and decreased DLCO. Decreased DLCO may indicate more severe sickle vasculopathy characterized by impaired hepatic and renal function.