Brain-injured patients exhibited significantly lower respiratory heart rate variability amplitude (1.04 vs. 6.21 bpm; p<0.001) and an inverted phase compared to healthy controls.
Does brain injury alter respiratory heart rate variability amplitude and phase compared to healthy humans?
Brain-injured patients demonstrate markedly reduced amplitude and inverted phase of respiratory heart rate variability, which may serve as a physiological marker of impaired brainstem control and neurological recovery.
• Brain-injured patients show markedly reduced amplitude of respiratory heart rate variability (RespHRV). • RespHRV phase is inverted in brain-injured patients, with peak heart rate during expiration. • Sedation depth and machine-triggered ventilation significantly decrease RespHRV amplitude. Respiratory heart rate variability (RespHRV), the variation in heart rate in phase with breathing, is mainly generated by central brainstem mechanisms. Its characteristics in brain-injured patients are poorly understood. The objective of the study was to characterize RespHRV amplitude and phase in brain-injured patients compared to healthy participants. We analyzed 55 brain-injured patients and 31 healthy controls. Physiological signals were recorded and processed to extract RespHRV amplitude and phase. Group differences were assessed using Mann–Whitney and Watson–Williams tests. In an additional analysis, 55 patients’ RespHRV amplitude and phase were modeled using generalized linear mixed models to evaluate the impact of sedation, ventilation mode, vasoactive and analgesic drugs, and time. Compared to controls, brain-injured patients exhibited a significantly lower RespHRV amplitude (1.04 0.45, 1.96 vs. 6.21 4.08, 9.34 bpm; p < 0.001) and an inverted RespHRV phase, with peak heart rate occurring during expiration rather than inspiration. Mixed-effects modeling revealed that machine-triggered ventilation and high level of sedation induced a significant reduction in RespHRV amplitude. Brain-injured patients demonstrate markedly impaired central generation of RespHRV. This profound alteration of RespHRV reflects impaired brainstem control and offers a potential physiological marker of autonomic and neurological recovery.
Ghibaudo et al. (2026) studied this question. Brain-injured patients exhibited significantly lower respiratory heart rate variability amplitude (1.04 vs. 6.21 bpm; p<0.001) and an inverted phase compared to healthy controls.
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