Abstract
The novel method and the device for non - invasive cerebrovascular autoregulation (CA) status monitoring without using the arterial blood pressure (ABP) measurement channel are presented. This fully non-invasive CA monitor is based on the ultrasonic time-of-flight measurement of cerebral blood volume pulsations within the brain parenchyma, extraction of informative and reference slow and respiratory volumetric waves and calculation of CA estimating indexes without using any additional ABP measurements.For demonstrating the applicability of the proposed method, the CA status was monitored on 11 traumatic brain injury patients simultaneously by using the novel fully non-invasive monitor and compared to the CA status representing indexes calculated from the invasively measured intracranial pressure (ICP) and ABP slow waves. The total monitoring time was about 22 hrs. The correlation factor between the invasively and non-invasively obtained CA data showed significant agreement (r=0.751) between the two methods.The proposed innovative CA real-time monitoring method gives us new possibilities to perform estimation of the CA status from the intracranial waves only as well as to exclude the ABP line’s errors and artifacts from the measurement results.DOI: http://dx.doi.org/10.5755/j01.eee.20.8.5464
Highlights
Cerebrovascular autoregulation (CA) is a protective mechanism of the brain to regulate its blood supply by expanding or narrowing arterioles, while maintaining stable cerebral blood flow when cerebral perfusion pressure (CPP) is changing within physiological ranges [1], [2]
We have found that the reference slow or respiratory waves might be extracted after demodulation of the noninvasively measured intracranial pressure (ICP) pulse waves and used instead of the reference arterial blood pressure (ABP) waves [19], [20]
These slow waves were processed by using software ICM+ (Cambridge, UK) in order to calculate the moving correlation coefficient r(ICP; ABP) which was kept as a reference index of the CA status estimation
Summary
Cerebrovascular autoregulation (CA) is a protective mechanism of the brain to regulate its blood supply by expanding or narrowing arterioles, while maintaining stable cerebral blood flow when cerebral perfusion pressure (CPP) is changing within physiological ranges [1], [2]. The human brain is at risk of a secondary injury, especially when this. The autoregulation is effective when the CPP is approximately within the physiological limits from 50 mmHg to 150 mmHg. The CPP above the upper limit of autoregulation can cause cerebral oedema or hyperaemia. The CPP below the lower threshold causes disturbed supply of the blood flow and, as a result, cerebral ischemia. A brain injury can lead to vasomotor paralysis when autoregulation is impaired and cerebral blood flow depends entirely on CPP [5]
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