Respiratory and peripheral muscle function in individuals with sickle cell anemia

Abstract

Introduction: Sickle cell anemia (SCA) is a chronic and systemic disease, being a public health problem in many parts of the world. It can cause a huge social impact due to its increasing progression, especially in Brazil where miscegenation produced high rates of incidence and prevalence of this illness. It belongs to the group of the sickle illnesses which include a great diversity of affections that cause dysfunction in hemoglobin and changes in its synthesis or structure producing, thus, occlusion in microcirculation and diverse symptomatology. In SCA, the systemic effects happen since the aggravation of the illness, as a respiratory and peripheral muscle dysfunction, painful crises and infarction or necrosis in many tissues, organs and systems, causing a decrease in quality of life (QoL) and life expectancy of these individuals. In these patients, the interest in the evaluation of the respiratory and peripheral muscle function and in the measurements of QoL is increasing progressively, once it can direct the development of new strategies for their treatment. Objective: To evaluate the respiratory and peripheral muscle function in adults with SCA, as well as to study the correlations between respiratory muscle function, peripheral muscle function and QoL from these individuals. Methods: In this cross-sectional study, it was included 22 individuals with SCA in outpatient treatment and 22 paired healthy volunteers which constituted the control group. All the participants were subjected to the muscle strength tests and endurance of quadriceps and hamstrings through the isokinetic dynamometer, hand grip strength and measure of respiratory muscle strength. Furthermore, they answered the following questionnaires: Medical Outcomes Study 36-item Short-Form Health Survey (SF-36, separately evaluated in relation to the Physical Component Summary-PCS and the Mental Component Summary-MCS) and International Physical Activity Questionnaire (IPAQ). Results: In relation to the healthy controls, adults with SCA had lower SF-36 scores, respiratory muscle strength and hand grip, but not on IPAQ. Regarding the isokinetic test, adults with SCA showed lower values, especially in the variable measures in flexion and with an angular velocity of 240o/s. There was a significant correlation between the peak torque (PT) at 240º/s and the SF-36-SCF in both extension (r = 0.77; p < 0.001) and flexion (r = 0.82; p < 0.001). It was also observed a significant correlation between the agonist/antagonist ratio (PT of hamstrings divided by PT of quadriceps) at 240o/s and the SF-36-PCS (r = 0.50; p < 0.001). Furthermore, the use of hydroxyurea positively impacted in to higher PT values. Conclusion: Adults with SCA have muscular dysfunction, especially in endurance of the knee flexor muscles. In these patients, there is a strong relation between muscle function with the QoL, mainly when there is unbalance between the muscles of quadriceps and hamstrings. Furthermore, the use of hydroxyurea positively impact in better performance in the peripheral muscle of these individuals.