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Barry Dixon,1â 3 Jessica M Sharkey,1 Elliot J Teo,1,2 Sally A Grace,1 Jacqui S Savage,1 Andrew Udy,4 Paul Smith,5,6 Jack Hellerstedt,1 John D Santamaria2 1Cyban Pty Ltd, Melbourne, VIC, Australia; 2Department of Critical Care Medicine, St Vincentâs Hospital, Melbourne, Australia; 3Department of Medicine, University of Melbourne, Melbourne, Vic, Australia; 4Department of Critical Care Medicine, The Alfred Hospital, Melbourne, Australia; 5Department of Neurosurgery, St Vincentâs Hospital, Melbourne, Australia; 6University of Melbourne Medical School, Melbourne, Vic, AustraliaCorrespondence: Barry Dixon, Department of Critical Care Medicine, St Vincentâs Hospital (Melbourne), 41 Victoria Parade, Fitzroy, VIC, 3065, Australia, Tel +61 3 9231 4425, Email barry.dixon@svha.org.auBackground: Intracranial pressure (ICP) monitoring requires placing a hole in the skull through which an invasive pressure monitor is inserted into the brain. This approach has risks for the patient and is expensive. We have developed a non-invasive brain pulse monitor that uses red light to detect a photoplethysmographic (PPG) signal arising from the blood vessels on the brainâs cortical surface. The brain PPG and the invasive ICP waveform share morphological features which may allow measurement of the intracranial pressure.Methods: We enrolled critically ill patients with an acute brain injury with invasive ICP monitoring to assess the new monitor. A total of 24 simultaneous invasive ICP and brain pulse monitor PPG measurements were undertaken in 12 patients over a range of ICP levels.Results: The waveform morphologies were similar for the invasive ICP and brain pulse monitor PPG approach. Both methods demonstrated a progressive increase in the amplitude of P2 relative to P1 with increasing ICP levels. An automated algorithm was developed to assess the PPG morphological features in relation to the ICP level. A correlation was demonstrated between the brain pulse waveform morphology and ICP levels, R2=0.66, P < 0.001.Conclusion: The brain pulse monitorâs PPG waveform demonstrated morphological features were similar to the invasive ICP waveform over a range of ICP levels, these features may provide a method to measure ICP levels.Trial Registration: ACTRN12620000828921.Keywords: intracranial pressure, acute brain injury, monitoring, non-invasive, photoplethysmography |
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