Cerebral Autoregulation Assessment Using the Near Infrared Spectroscopy ‘NIRS-Only’ High Frequency Methodology in Critically Ill Patients: A Prospective Cross-Sectional Study

Abstract

Impairments in cerebral autoregulation (CA) are related to poor clinical outcome. Near infrared spectroscopy (NIRS) is a non-invasive technique applied to estimate CA. Our general purpose was to study the clinical feasibility of a previously published ‘NIRS-only’ CA methodology in a critically ill intensive care unit (ICU) population and determine its relationship with clinical outcome. Bilateral NIRS measurements were performed for 1–2 h. Data segments of ten-minutes were used to calculate transfer function analyses (TFA) CA estimates between high frequency oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) signals. The phase shift was corrected for serial time shifts. Criteria were defined to select TFA phase plot segments (segments) with ‘high-pass filter’ characteristics. In 54 patients, 490 out of 729 segments were automatically selected (67%). In 34 primary neurology patients the median (q1–q3) low frequency (LF) phase shift was higher in 19 survivors compared to 15 non-survivors (13° (6.3–35) versus 0.83° (−2.8–13), p = 0.0167). CA estimation using the NIRS-only methodology seems feasible in an ICU population using segment selection for more robust and consistent CA estimations. The ‘NIRS-only’ methodology needs further validation, but has the advantage of being non-invasive without the need for arterial blood pressure monitoring.

Evaluation of Morlet Wavelet Analysis for Artifact Detection in Low-Frequency Commercial Near-Infrared Spectroscopy Systems

“…Apart from having its own potential clinical prognostic values in varying disease states, rSO 2 has also shown to be an effective metric for measuring changes in cerebral blood flow (CBF) [ 21 , 22 , 23 ]. The non-invasive nature of NIRS devices reduces the difficulty of implementation compared to invasive cerebral hemodynamic monitoring methods like intracranial pressure (ICP) monitoring [ 24 ]. Despite these benefits, NIRS data streams are particularly rife with artifacts due to patient motion [ 9 , 11 ] pads falling off, and signal distortion due to hematomas [ 25 ] or other cerebral tissue [ 26 ].…”

Investigation of Cerebral Autoregulation Using Time-Frequency Transformations

“…Assessment of CA using NIRS-only methodology seems feasible in critically ill sedated/coma patients after incorporating methodological improvements. As the authors of the article [ 26 ] state, the NIRS-only methodology has the advantage that it is non-invasive and does not require monitoring of arterial blood pressure. However, the method has not yet entered into practice and requires further validation.…”