The Vittamed 505 monitor uses transintracranial ultrasound to assess the change in the time an ultrasound pulse takes to cross the brain as intracranial blood and CSF volume varies. It generates a pressure-reactivity index measure (PRx), which is the phase difference between intracranial pressure and arterial blood pressure waves. Normal or intact cerebrovascular autoregulation has a negative correlation and up to 160 degrees in phase difference between ABP and ICP slow waves, i.e. cerebral arterioles constrict with increasing cerebral perfusion pressure, while a positive correlation or almost zero phase shift between ABP and ICP slow waves shows non-reacting cerebral vessels and impaired autoregulation.
Vittamed Technologies has demonstrated that the Vittamed 505 monitor generates similar autoregulation readings to invasive ABP and ICP slow wave monitoring in patients with traumatic brain injury (1,2).
Vittamed Technologies already patented [ European Patent No 2 111 787 B1 ] fully non-invasive version of Vittamed 505 which does not need ABP reference signals. Reference signal for phase shift monitoring and automatic PRx calculation is obtained by sophisticated automatic analysis of non-invasively recorded intracranial blood volume slow, respiratory and pulse waves.
It was demonstrated, that non-invasive monitoring delivers similar autoregulation readings to invasive monitoring (1,2).
1 Ragauskas et al: Med Engineering & Physics: 2003: 25: 667-678
2 Ragauskas et al: Acta Neurochir : 2005: [Suppl] 95: 367-370