Exercise Tolerance in Adult Sickle Cell Disease Patients

Abstract

Background Many adults with sickle cell disease (SCD) complain of significant exercise intolerance despite the health benefits in exercise. Most children with SCD also miss out on the important benefits of exercise because of unsubstantiated fears that it might be harmful in their condition. Several factors could contribute to exercise limitation in these patients. The six-minute walk test (6MWT) is a standardized test use to measure a person’s exercise tolerance. It is being increasingly used as a measure of overall functional ability in patients. However little information exists regarding the safety or the limit of exercise SCD patients can tolerate. The purpose of the present study is to examine these issues. General Aim To determine the exercise tolerance limit of SCD patients by using the six-minute walk test. Method A case control study was performed on 36 adult SCD patients (13 males and 23 females) and 36 healthy adult controls (13 males and 23 females) at the Tema General Hospital by the six minute walk test (6MWT). Anthropometric data of all participants comprising of height (cm) and weight (kg) were measured and body mass index (BMI) derived from this data were all recorded. The haemoglobin (Hb) level of all participants were measured. The following parameters were measured and recorded in all the participants prior to the 6MWT, 5 and 10 minutes after the test respectively: blood pressure (SBP and DBP), HR, SpO2, PEFR, chest pain (angina scale), dyspnoea, and leg fatigue (modified Borg scale) The total distance walked was also recorded in metres. The 6MWD was used to estimate the VO2 and the MET. Factors associated with the 6MWD were evaluated using multivariate analysis and used to derive an equation which aimed to estimate the likely 6MWD from the variables. The level of significance was set at p < 0.05. SPSS version 23 software was used for statistical analysis. Results The mean age of the SCD patients was 28.44 ± 6.29years and the healthy controls was 28.44 ± 6.29years. The mean Hb for SCD patients’ males and females were 8.60 ± 1.27g/dl and 9.84 ± 1.75 g/dl respectively: (p = 0.002). The mean Hb for healthy control males and females were 14.11 ± 0.56g/dl and 12.82 ± 0.69g/dl respectively (p < 0.001). There was however no significant difference in the mean height (m) ((1.68 ± 0.08 m) vs. (1.70 ± 0.070 m) (p = 0.137)) and mean BMI ((20.09 ± 3.19kg/m2) vs. (21.4 ± 2.80kg/m2) (p = 0.060)) between cases and controls respectively. There was a significant difference in the mean weight between cases and controls ((56.64 ± 10.67 kg) vs. (62.51± 10.51 kg): (p = 0.021)). There was an increase in the SBP, DBP, HR at the end of the 6MWD and decreased subsequently at 5 minutes and 10minutes after the test for the cases and as well as the controls. The SPO2 however, decreased at the end of the 6MWD and increased at 5 minutes and 10minutes after the test both cases and controls. The PEFR increased at the end of the 6MWD up to 10minutes after the test in both cases and controls. There was also significant difference (p < 0.001) in the mean distance walked in six minutes between SCD patients (551.03± 63.32m) and healthy controls (666.72 ±80.06m). Conclusion This study provides the first preliminary data on exercise tolerance for healthy Ghanaian adults and SCD patients between the ages of 20 years and 45 years. The maximum HR achieved, minimum SPO2, VO2, MET and blood pressures in adult SCD patients and healthy controls were within normal range in this study. Therefore SCD patients may take the 6MWD test safely. There was an improvement in PEFR in both SCD patients and healthy controls after the test. Even though SCD patients achieved lower values than the healthy controls. The maximum distance walked by SCD patients was significantly shorter than that of the healthy controls. Therefore SCD patients have reduced tolerance to exercise than healthy controls.