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Transmission of slow waves in Masimo O3 near infrared spectroscopy measures.

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Kazimierska, Agnieszka  ORCID logo
Karvandi, Elika 


INTRODUCTION: Cerebral autoregulation (CA) dysfunction is a key complication following brain injury. CA assessment using near-infrared spectroscopy (NIRS) offers a promising alternative to the current non-invasive standard, cerebral blood flow velocity (CBFV) measured with transcranial Doppler. RESEARCH QUESTION: Can autoregulatory slow waves (frequency range 0.005-0.05 Hz) associated with spontaneous and induced changes in ABP in healthy volunteers be detected by parameters measured with the Masimo O3 NIRS device? METHODS: ABP, CBFV and Masimo O3 parameters were measured in 10 healthy volunteers at baseline and during ABP oscillations induced by squat/stand manoeuvres. Transmission of slow waves was assessed with power spectral density and coherence analysis in NIRS signals and compared to that of CBFV. RESULTS: At baseline, slow waves were detected with sufficient power that substantially exceeded the signals' measurement resolution in all parameters except cerebral oxygen saturation. During ABP oscillations in the 0.033 Hz range (induced by squat/stand), the power of slow waves increased in all parameters in a similar pattern, with total (cHb) and oxygenated (O2Hb) haemoglobin concentrations most closely mirroring CBFV (median standardised power [first-third quartile], baseline vs squat/stand: CBFV 0.35 [0.28-0.42] vs 0.50 [0.45-0.62], O2Hb 0.47 [0.33-0.68] vs 0.61 [0.59-0.69]). Coherence with ABP increased for both CBFV and NIRS measures from low at baseline (<0.4) to high during induced changes (>0.8). CONCLUSION: Spontaneous fluctuations in ABP can be observed in analysed Masimo O3 metrics to a varying degree. The clinical utility of Masimo O3 signals in CA assessment requires further investigation in brain injury patients.



Brain injury, Cerebral autoregulation, Cerebral blood flow, Multimodality monitoring, Near infrared-spectroscopy, Transcranial Doppler

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Brain Spine

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Elsevier BV
Medical Research Council (G0802251/1)
Authors’ support: CAS– Skye Cambridge International Patrick & Margaret Flanagan Scholarship. AK– Polish National Agency for Academic Exchange. EB– the Medical Research Council (grant no.: MR N013433-1) and by the Gates Cambridge Scholarship. AH– Medical Research Council/Royal College of Surgeons of England Clinical Research Training Fellowship (Grant no. G0802251), the NIHR Biomedical Research Centre and the NIHR Brain Injury MedTech Cooperative; The views expressed are those of the authors and are not necessarily those of the NIHR, the Department of Health and Social Care or of any of the other funding bodies.