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Introduction: There is evidence that sleep disorders, including nocturnal hypoxemia, are common in individuals with cystic fibrosis (CF), but diagnostic tests are not routinely performed at an early stage, leading to late detection and worse prognosis. Similarly, it is known that there is a correlation between heart rate variability (HRV) and mortality in several clinical conditions. Evidence demonstrates changes in HRV as a consequence of some sleep disorders, but few studies relate such changes in patients with CF. Objective: To correlate HRV with findings of sleep disorders in CF children and adolescents. Methods: This is a cross-sectional study, with individuals diagnosed with CF, aged between 6 and 18 years, attended at a Reference Center in Vitória, Espírito Santo. Information regarding the sociodemographic and clinical profile of the sample, Shwachman Kulczycki (SK) score, evaluation of lung function, nutritional status and daily physical activity levels were recorded through the aplication of the short version of the International Physical Activity Questionnaire– IPAQ. To assess the heart rate variability, a Polar RS800CX cardiofrequency meter (Polar Electro Oy, Finland) was used for 25 minutes while at rest and to evaluate possible sleep disorders, basal nocturnal polysomnography was performed. For the analysis, HRV data were transmitted to a computer using a Polar ProTrainer 5 software and converted to text files that were analyzed using the Kubios HRV Standard Software. The initial 5 minutes were excluded for parameters stabilization purposes and manual filtering was performed to eliminate ectopic beats and a low intensity digital filter was applied to eliminate abnormal RR intervals, considering a maximum of 5% correction. As a sleep evaluation criteria, nocturnal hypoxemia was considered in individuals with an oxyhemoglobin saturation (SpO2) less than 90% for more than 5% of the total sleep time (TST), and obstructive sleep apnea syndrome (OSAS) when the rate of obstructive apnea and hypopnea was greater than or equal to 2 per hour. Results: The sample consisted of 30 individuals, with a mean age of 11.2 years, mostly female (66.6%). Reduced sleep efficiency was identified in 66.49% of patients, respiratory disorder index (RDI) with a median of 2.5 (1.85-3.9) and a presence of OSAS (rate of obstructive apnea and hypopnea ≥2 / h) oft 30% (n=9). In the HRV analysis we have found a mean SDNN of 60.76±45.85 and, in the frequency domain, a mean of 60.35±17.20 for LF (nu) and 38.90±17.24 for HF (nu). There was a significant correlation between the overall LF/HF modulation index and the minimum SpO2 during the sleep of patients in the group with lower pulmonary function (r=0.7134; p=0.02). The prevalence of sleep disorders and HRV abnormities was higher in individuals with lower pulmonary function (FEV1≤60%). Conclusion: The results obtained indicate an isolated correlation of sleep disorders with HRV parameters only in individuals with reduced pulmonary function. In addition, these patients have a higher prevalence of autonomic nervous system disorders, nocturnal hypoxemia, and OSAS. |
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