Abstract / Summary
Introduction: Spinal cord injury (SCI), especially at cervical and upper thoracic levels, impairs cardiovascular autonomic regulation, resulting in changes in heart rate (HR) and responses to postural stimuli. Heart rate variability (HRV) is a noninvasive method used to assess this modulation. Objective: To analyze HRV in adult patients with spinal cord injury during hospital hospitalization, comparing individuals with injuries above and below the T5 level in different body positions. Methods: This was a cross-sectional observational study conducted in the wards of an Emergency Hospital in Goiás, Brazil, including individuals aged ≥18 years of both sexes diagnosed with spinal cord injury. HRV was recorded using a Polar H10 heart rate monitor in the supine position at 0° and with head-of-bed elevation to 60°, for 5 minutes in each position. Data were analyzed using Kubios HRV software. The following parameters were assessed: mean RR interval, mean HR, RMSSD, SDNN, LF/HF ratio, and the non-linear index DFA α1. Participants were stratified according to the level of injury (above and below T5). Statistical analysis was performed using IBM SPSS Statistics 26, applying the Wilcoxon and Mann–Whitney U tests, with p < 0.05 considered statistically significant. Results: A total of 33 individuals participated in the study, predominantly male, with a mean age of 35 ± 14 years. In the supine position (0°), patients with injuries above T5 showed significantly reduced mean RR intervals (p = 0.025), higher mean HR (p = 0.026), and lower autonomic complexity assessed by DFA α1 (p = 0.041) compared with those injured below T5. During head-of-bed elevation to 60°, these differences persisted for mean RR (p = 0.013) and mean HR (p = 0.014), and were associated with a significant change in the LF/HF ratio (p = 0.030) and a more pronounced reduction in DFA α1 (p = 0.005), indicating lower autonomic adaptability in individuals with higher-level injuries. Conclusion: Patients with spinal cord injury above T5 exhibit greater cardiac autonomic dysfunction and reduced adaptive capacity in response to postural changes during hospital hospitalization.