Cardiorespiratory and metabolic responses to exercise in HbSC sickle cell patients

The relationship between hemoglobin and [Formula: see text]: A systematic review and meta-analysis

OBJECTIVE

There is widespread agreement about the key role of hemoglobin for oxygen transport. Both observational and interventional studies have examined the relationship between hemoglobin levels and maximal oxygen uptake ([Formula: see text]) in humans. However, there exists considerable variability in the scientific literature regarding the potential relationship between hemoglobin and [Formula: see text]. Thus, we aimed to provide a comprehensive analysis of the diverse literature and examine the relationship between hemoglobin levels (hemoglobin concentration and mass) and [Formula: see text] (absolute and relative [Formula: see text]) among both observational and interventional studies.

METHODS

A systematic search was performed on December 6th, 2021. The study procedures and reporting of findings followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Article selection and data abstraction were performed in duplicate by two independent reviewers. Primary outcomes were hemoglobin levels and [Formula: see text] values (absolute and relative). For observational studies, meta-regression models were performed to examine the relationship between hemoglobin levels and [Formula: see text] values. For interventional studies, meta-analysis models were performed to determine the change in [Formula: see text] values (standard paired difference) associated with interventions designed to modify hemoglobin levels or [Formula: see text]. Meta-regression models were then performed to determine the relationship between a change in hemoglobin levels and the change in [Formula: see text] values.

RESULTS

Data from 384 studies (226 observational studies and 158 interventional studies) were examined. For observational data, there was a positive association between absolute [Formula: see text] and hemoglobin levels (hemoglobin concentration, hemoglobin mass, and hematocrit (P<0.001 for all)). Prespecified subgroup analyses demonstrated no apparent sex-related differences among these relationships. For interventional data, there was a positive association between the change of absolute [Formula: see text] (standard paired difference) and the change in hemoglobin levels (hemoglobin concentration (P<0.0001) and hemoglobin mass (P = 0.006)).

CONCLUSION

These findings suggest that [Formula: see text] values are closely associated with hemoglobin levels among both observational and interventional studies. Although our findings suggest a lack of sex differences in these relationships, there were limited studies incorporating females or stratifying results by biological sex.

Safety of maximal cardiopulmonary exercise testing in individuals with sickle cell disease: a systematic review

OBJECTIVE

We evaluated the safety of maximal cardiopulmonary exercise testing (CPET) in individuals with sickle cell disease (SCD). Maximal CPET using gas exchange analysis is the gold standard for measuring cardiopulmonary fitness in the laboratory, yet its safety in the SCD population is unclear.

DESIGN

Systematic review.

DATA SOURCES

Systematic search of Medline (PubMed), EMBASE, Cochrane, ClinicalTrials.gov and professional society websites for all published studies and abstracts through December 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Two reviewers independently extracted data of interest from studies that assessed safety outcomes of maximal CPET in children and adults with SCD. A modified version of the Newcastle-Ottawa Scale was used to assess for risk of bias in studies included.

RESULTS

In total, 24 studies met inclusion/exclusion criteria. Adverse events were reported separately or as part of study results in 36 (3.8%) of 939 participants with SCD undergoing maximal CPET in studies included. Most adverse events were related to transient ischaemic changes on ECG monitoring or oxygen desaturation during testing, which did not result in arrhythmias or other complications. Only 4 (0.43%) of 939 participants experienced pain events due to maximal CPET.

CONCLUSION

Maximal CPET appears to be a safe testing modality in children and adults with SCD and can be used to better understand the physiological basis of reduced exercise capacity and guide exercise prescription in this population. Some studies did not focus on reporting adverse events related to exercise testing or failed to mention safety monitoring, which contributed to risk of bias.

Impact of a submaximal mono-articular exercise on the skeletal muscle function of patients with sickle cell disease

PURPOSE

Sickle cell disease (SCD) patients exhibit a limited exercise tolerance commonly attributed to anaemia, as well as hemorheological and cardio-respiratory abnormalities, but the functional status of skeletal muscle at exercise is unknown. Moreover, the effect of SCD genotype on exercise tolerance and skeletal muscle function has been poorly investigated. The aim of this study was to investigate skeletal muscle function and fatigue during a submaximal exercise in SCD patients.

METHODS

Nineteen healthy individuals (AA), 28 patients with sickle cell anaemia (SS) and 18 with sickle cell-haemoglobin C disease (SC) performed repeated knee extensions exercise (FAT). Maximal isometric torque (Tmax) was measured before and after the FAT to quantify muscle fatigability. Electromyographic activity and oxygenation by near-infrared spectroscopy of the Vastus Lateralis were recorded.

RESULTS

FAT caused a reduction in Tmax in SS (- 17.0 ± 12.1%, p < 0.001) and SC (- 21.5 ± 14.5%, p < 0.05) but not in AA (+ 0.58 ± 29.9%). Root-mean-squared value of EMG signal (RMS) decreased only in SS after FAT, while the median power frequency (MPF) was unchanged in all groups. Oxygenation kinetics were determined in SS and AA and were not different.

CONCLUSION

These results show skeletal muscle dysfunction during exercise in SCD patients, and suggest different fatigue aetiology between SS and SC. The changes in EMG signal and oxygenation kinetics during exercise suggest that the greater skeletal muscle fatigue occurring in SCD patients would be rather due to intramuscular alterations modifications than decreased tissue oxygenation. Moreover, SS patients exhibit greater muscle fatigability than SC.

Exercise capacity and clinical outcomes in adults followed in the Cooperative Study of Sickle Cell Disease (CSSCD)

OBJECTIVES

To determine the factors associated with exercise capacity in adults with sickle cell disease (SCD) and its relationship to hospitalizations and mortality.

METHODS

A total of 223 participants in the Cooperative Study of Sickle Cell Disease (CSSCD) (64% female, 70% hemoglobin SS/Sβ⁰ thalassemia, mean age 43.3 ± 7.5 years) underwent maximal exercise testing using a treadmill protocol with a mean duration of 11.6 ± 5.2 minutes.

RESULTS

Female sex (β = -3.34, 95% CI [-1.80, -4.88], P < 0.001), older age (β = -0.14, 95% CI [-0.24, -0.04], P = 0.005), higher body mass index (β = -0.23, 95% CI [-0.37, -0.10]; P = 0.001), and lower hemoglobin (β = 0.56, 95% CI [0.08, 1.04], P = 0.02) were independently associated with lower fitness, while there was a trend with abnormal pulmonary function testing (β = -1.42, 95% CI [-2.92, 0.07]; P = 0.06). Lower percent-predicted forced expiratory volume in 1 second (FEV₁ ) was independently associated with lower fitness (β = 0.08, 95% CI [0.03, 0.13], P = 0.001). Genotype and hospitalization rates for pain and acute chest syndrome (ACS) prior to testing were not associated with exercise capacity. Baseline exercise capacity predicted neither future pain or ACS nor survival in our cohort. Adults with SCD tolerated maximal exercise testing.

CONCLUSIONS

Prospective studies are needed to further evaluate the impact of regular exercise and improved fitness on clinical outcomes and mortality in SCD.

Exercise tolerance, lung function abnormalities, anemia, and cardiothoracic ratio in sickle cell patients

Many patients with sickle cell disease (SCD) have a reduced exercise capacity and abnormal lung function. Cardiopulmonary exercise testing (CPET) can identify causes of exercise limitation. Forty-four consecutive SCD patients (27 HbSS, 11 HbSC, and 6 HbS-beta thalassemia) with a median age (interquartile range) of 26 (21-41) years underwent pulmonary function tests, CPET, chest x-ray, and echocardiography to further characterize exercise limitation in SCD. Peak oxygen uptake (V'O2 -peak), expressing maximum exercise capacity, was decreased in 83% of the studied patients. V'O2 -peak correlated with hemoglobin levels (R = 0.440, P = 0.005), forced vital capacity (FVC) (R = 0.717, P < 0.0001). Cardiothoracic ratio on chest x-ray inversely correlated with FVC (R = -0.637, P < 0.001). According to criteria for exercise limitation, the patients were limited in exercise capacity due to anemia (n = 17), cardiovascular dysfunction (n = 2), musculoskeletal function (n = 10), pulmonary ventilatory abnormalities (n = 1), pulmonary vascular exercise limitation (n = 1), and poor effort (n = 3). In the present study we demonstrate that anemia is the most important determinant of reduced exercise tolerance observed in SCD patients without signs of pulmonary hypertension. We found a strong correlation between various parameters of lung volume and cardiothoracic ratio and we hypothesize that cardiomegaly and relative small chest size may be important causes of the impairment in pulmonary function, that is, reduced long volumes and diffusion capacity, in SCD. Taking into account anthropomorphic differences between SCD patients and controls could help to interpret lung function studies in SCD better.

Lactic response in sickle cell trait carriers in comparison with subjects with normal hemoglobin

OBJECTIVE

The objective of this study was to assess lactic response (mmol/L) during incremental exercise in a specific population of men and women with sickle cell trait.

SUBJECTS

Athletic men and women from the French West Indies showing no anemia and/or alpha thalassemia.

METHODS

Anemia was ruled out by hemoglobin level, and alpha thalassemia was ruled out by hemoglobin S percentage with concomitant hemoglobin level and mean corpuscular volume. Comparison was made with control subjects with normal hemoglobin, matched for physical fitness, anthropometric data, and sex. All subjects performed an incremental exercise test using a cycle ergometer. Peak oxygen uptake (mL/min) was predicted from an equation at peak exercise. Heart rate (beats/min) was noted continuously, and blood samples were collected for lactic response determination every minute during the incremental exercise test and at 1, 3, and 5 minutes of recovery.

RESULTS

Comparison of peak oxygen uptake and heart rate values showed no significant differences in subjects with sickle cell trait versus control subjects during the incremental exercise test. In contrast, analysis of variance revealed significantly lower lactic response time courses during the incremental exercise test and at peak exercise (p < 0.05) in the sickle cell trait group, whereas the heart rate time course was lower during recovery (p < 0.05).

CONCLUSION

We conclude that the lower lactic response exhibited by subjects with sickle cell trait during incremental exercise was the result of an adaptive process in red blood cells in relation to either lower lactate production or greater lactate uptake capability than in individuals with normal hemoglobin.

Equation to estimate resting energy expenditure in adolescents with sickle cell anemia

BACKGROUND

Basal energy requirements are higher in adolescents with sickle cell anemia (SCA) than in healthy control subjects. However, no equation is available to accurately predict their energy needs.

OBJECTIVE

Our objective was to develop a clinically useful equation to estimate resting energy expenditure (REE) in adolescents with SCA.

DESIGN

REE and other components of total energy expenditure were measured in adolescents with SCA (n = 37) and in control subjects (n = 23) for 24 h in a whole-room indirect calorimeter. Multiple linear regression analysis was used to describe the relations of REE with independent variables such as sex, weight, height, fat-free mass, fat mass, age, and hemoglobin concentration in adolescents with SCA. The Bland-Altman comparison technique was used to compare values predicted by existing equations with measured REE values.

RESULTS

Mean (+/-SD) measured REEs were 7746 +/- 974 and 6332 +/- 869 kJ/d in the male and female subjects with SCA, respectively, and these values were 16% higher than those in the healthy control subjects. Standard equations underestimated REE by 12% (P </= 0.001) in adolescents with SCA and overestimated REE by 4% in control subjects (P = 0.01-0.29). Several REE regression equations for SCA were developed. The most parsimonious equation for males was REE (kJ/d) = 5461 + 77.7.weight (kg) - 233.2.hemoglobin (g/dL), or REE (kcal/d) = 1305 + 18.6.weight (kg) - 55.7.hemoglobin (g/dL). For females, the most parsimonious equation was REE (kJ/d) = 4603 + 55.6.weight (kg) - 126.2.hemoglobin (g/dL), or REE (kcal/d) = 1100 + 13.3.weight (kg) - 30.2.hemoglobin (g/dL).

CONCLUSION

The new equations have better agreement with the basal metabolic needs of adolescents with SCA than do standard predictive equations.

Patterns and energy expenditure of free-living physical activity in adolescents with sickle cell anemia

OBJECTIVE

Our purpose was to examine the relationship between physical activity (PA), PA-associated energy expenditure (PAEE), and total daily energy expenditure (TEE) in free-living adolescents with sickle-cell anemia (SCA).

STUDY DESIGN

Adolescents with SCA (n = 28) were matched for sex and age with 22 healthy control participants. PA was measured for 6 to 8 consecutive days with a triaxial accelerometer and resting energy expenditure (REE) by whole-room indirect calorimetry. TEE was calculated by summing PAEE and REE.

RESULTS

TEE was similar, REE was higher (difference, 209 kcal x day(-1); P =.0001), and PAEE was lower (difference, 657 kcal x day(-1); P <.001) in patients with SCA than in control participants. In SCA, there was a positive linear relationship between PAEE and hemoglobin concentration (r (2) = 0.583). Time spent in PA of moderate and high intensity was lower in patients with SCA than in control participants (18 +/- 22 vs 48 +/- 31 min/d; P <.0001).

CONCLUSION

In adolescents with SCA under free-living conditions, there is a significant intra and interindividual variability in the amount of PA, PAEE, and PA patterns. Because of a lower PAEE and a higher REE, TEE is similar in adolescents with SCA and healthy adolescents. An association of PAEE with hemoglobin concentration may be a part of an energy saving compensatory mechanism in SCA.