Effects of Diaphragmatic Breathing in Sickle Cell Disease Patients: Preliminary Data

Introduction: Sickle cell disease (SCD) can be defined as an autosomal recessive disease, characterized by hemolytic anemia, progressive lesions in most organs and vaso-occlusive crises. Affected individuals suffer from severe pain due to vaso-occlusion and ischemic damage. Acute and chronic pulmonary complications including acute thoracic syndrome, pulmonary hypertension, thromboembolism, sleep-disordered breathing and asthma are among the leading causes of morbidity and mortality of SCD individuals. Dyspnea may be present due to pulmonary involvement, exercise intolerance, as well as a feature of pulmonary complications or due to the complications inherent to SCD. The practice of diaphragmatic breathing (DB) has been shown to improve exercise tolerance, reduce dyspnea and increase inspiratory muscle strength in several diseases, especially asthma and chronic obstructive pulmonary disease. However, the effects of this breathing exercise are not yet known in patients with SCD. Thus, the aim of this study was to evaluate the effects of BD in patients with SCD.

Methods: The study was approved by the UNICAMP ethics committee and all the patients who agreed to participate signed a written informed consent form. Participants were randomly divided into a control group (CG) and an intervention group (IG). The IG was instructed to do 3 sets of 20 repetitions per day of DB at home, 5 times a week. They were instructed to write down the date and time of DB, as well as justify any reason that prevented them from carrying out the training at some point. Patients in both groups were contacted weekly via the smartphone messaging application (app). In the case of IG patients, this contact aimed to reinforce the importance of continuing the intervention protocol. For the CG participants, the weekly contact was important in order avoid a bias of the GI participants alone receiving continuous attention from the researchers. In addition, once a week, IG participants had to record and send a video via the smartphone messaging app showing how they were doing the exercise. The video was analyzed and the patient received feedback, also via messaging app, from the researchers with compliments or suggestions for corrections regarding the practice of DB. Thus, there was constant monitoring of the implementation of the intervention protocol seeking to maintain patient adherence to the training protocol. The CG did not perform any breathing exercises during the study. The effects of DB on SCD patients were evaluated twice, the initial evaluation (IE) and final evaluation (FE), performed with a 12-week interval and consisted of the application of the Modified Medical Research Council Scale (mMRC), assessment of the maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP), volumetric capnography (VCap) and 6-minute walk test (6MWT). Comparison between groups was performed using the Mann-Whitney and Fisher's exact tests. Within-group comparisons of BD effects were performed using Wilcoxon's Sign Rank Test. The comparison between groups was performed with the Mann-Whitney Test with Bonferroni correction.

Results: 19 patients completed the 12 weeks between IE and FE. There were no significant differences between CG (n=9) and IG (n=10) based on age (p=0.1619), sex (p=0.0698), body mass index (p=0.5490) or severity of genotype (n=13 HbSS, 4 HbSC, 1 HbSβ0 and 1 HbSβ ⁺) with p=0.9879. At the end of the DB protocol, in the within-group comparations, the IG presented significant changes in MIP (p=0.0117) and among the variables measured by VCap, such as inspiratory tidal volume (p=0.0371), expiratory tidal volume (p=0.0371), Tobin index (p=0.0488) and oxygen saturation (p=0.0488). No significant alterations were observed in the other variables evaluated in between-group comparisons. The CG showed no significant change in any of the comparisons.

Conclusions: DB is an exercise that can be easily applied to outpatients with SCD, allowing for an improvement in inspiratory muscle strength, VCap and favoring blood oxygenation in these individuals.

Funding: FAPESP 2017/21801-2; CNPq grants #303405/2018-0; #405918/2022-4 - Instituto Nacional de Ciência e Tecnologia do Sangue (INCT do Sangue).