AI Article Synopsis

  • Transfer function analysis (TFA) is used to evaluate how the brain regulates blood flow, and this study tested the reliability of TFA metrics taken from short 5-minute recordings in various groups, including healthy subjects and critically ill patients.
  • The research found that separating recordings in time increased the variability (SRD) for gain metrics in both subarachnoid hemorrhage and sepsis patients, but extending recording durations did not improve reliability for any group.
  • In conclusion, 5-minute recordings are not long enough to get stable and reliable TFA metrics, especially in patients with severe conditions like subarachnoid hemorrhage and sepsis.

Article Abstract

Transfer function analysis (TFA) is a widely used method for assessing dynamic cerebral autoregulation in humans. In the present study, we assessed the test-retest reliability of established TFA metrics derived from spontaneous blood pressure oscillations and based on 5 min recordings. The TFA-based gain, phase and coherence in the low-frequency range (0.07-0.20 Hz) from 19 healthy volunteers, 37 patients with subarachnoid haemorrhage and 19 patients with sepsis were included. Reliability assessments included the smallest real difference (SRD) and the coefficient of variance for comparing consecutive 5 min recordings, temporally separated 5 min recordings and consecutive recordings with a minimal length of 10 min. In healthy volunteers, temporally separating the 5 min recordings led to a 0.38 (0.01-0.79) cm s mmHg higher SRD for gain (P = 0.032), and extending the duration of recordings did not affect the reliability. In subarachnoid haemorrhage, temporal separation led to a 0.85 (-0.13 to 1.93) cm s mmHg higher SRD (P = 0.047) and a 20 (-2 to 41)% higher coefficient of variance (P = 0.038) for gain, but neither metric was affected by extending the recording duration. In sepsis, temporal separation increased the SRD for phase by 94 (23-160)° (P = 0.006) but was unaffected by extending the recording. A recording duration of 8 min was required to achieve stable gain and normalized gain measures in healthy individuals, and even longer recordings were required in patients. In conclusion, a recording duration of 5 min appears insufficient for obtaining stable and reliable TFA metrics when based on spontaneous blood pressure oscillations, particularly in critically ill patients with subarachnoid haemorrhage and sepsis.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11215465PMC
http://dx.doi.org/10.1113/EP091500DOI Listing

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