Abstract:Background: Morphological alterations in intracranial pressure (ICP) pulse waveform (ICPW) secondary to intracranial hypertension (ICP >20 mmHg) and a reduction in intracranial compliance (ICC) are well known indicators of neurological severity. The exclusive exploration of modifications in ICPW after either the loss of skull integrity or surgical procedures for intracranial hypertension resolution is not a common approach studied. The present study aimed to assess the morphological alterations in ICPW amon… Show more
“…Both methods demonstrated an increase in the amplitudes of P2 and P3 relative to P1, a later pulse peak and a progressively indistinct notch and P3. 44–46 Figure 5 The evolution of the morphological waveform features of the brain pulse monitor PPG signal over a 3 day period in relation to the simultaneous invasive ICP (one pulse period) measured from an external ventricular drain positioned in the right lateral ventricle of a patient with a grade 5 sub-arachnoid haemorrhage. Day 1: Normal ICP.…”
Section: Resultsmentioning
confidence: 99%
“…An automated algorithm was developed to assess the brain pulse monitor’s correlation with ICP levels based on the brain pulse waveform, using ICP morphological waveform features known to be associated with raised ICP. 44–46 The normal ICP waveform typically comprises 3 peaks P1 (the percussion wave, representing the early systolic increase in brain volume), P2 (the mid/late systolic tidal wave) and P3 (the dicrotic wave, following closure of the aortic valve during diastole). The dicrotic notch represents an earlier nadir associated with aortic valve closure.…”
Section: Methodsmentioning
confidence: 99%
“…With raised ICP levels there is an increase in the amplitude of P2 and P3 relative with P1, a temporal delay in the pulse’s peak, an increasingly indistinct P3 and dicrotic notch and changes in the area under curve of the waveform. 44–47 The peaks were determined using the Scipy signal “find_peaks” function (v1.8.0) and area under the curve was estimated using the Numpy “Trapz” function (v1.22.3). Further details of the algorithm are not disclosed at this time for commercial reasons.…”
Background
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 brain’s 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, R
2
=0.66, P < 0.001.
Conclusion
The brain pulse monitor’s 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.
“…Both methods demonstrated an increase in the amplitudes of P2 and P3 relative to P1, a later pulse peak and a progressively indistinct notch and P3. 44–46 Figure 5 The evolution of the morphological waveform features of the brain pulse monitor PPG signal over a 3 day period in relation to the simultaneous invasive ICP (one pulse period) measured from an external ventricular drain positioned in the right lateral ventricle of a patient with a grade 5 sub-arachnoid haemorrhage. Day 1: Normal ICP.…”
Section: Resultsmentioning
confidence: 99%
“…An automated algorithm was developed to assess the brain pulse monitor’s correlation with ICP levels based on the brain pulse waveform, using ICP morphological waveform features known to be associated with raised ICP. 44–46 The normal ICP waveform typically comprises 3 peaks P1 (the percussion wave, representing the early systolic increase in brain volume), P2 (the mid/late systolic tidal wave) and P3 (the dicrotic wave, following closure of the aortic valve during diastole). The dicrotic notch represents an earlier nadir associated with aortic valve closure.…”
Section: Methodsmentioning
confidence: 99%
“…With raised ICP levels there is an increase in the amplitude of P2 and P3 relative with P1, a temporal delay in the pulse’s peak, an increasingly indistinct P3 and dicrotic notch and changes in the area under curve of the waveform. 44–47 The peaks were determined using the Scipy signal “find_peaks” function (v1.8.0) and area under the curve was estimated using the Numpy “Trapz” function (v1.22.3). Further details of the algorithm are not disclosed at this time for commercial reasons.…”
Background
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 brain’s 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, R
2
=0.66, P < 0.001.
Conclusion
The brain pulse monitor’s 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.
“…Our modest results may be explained because in BD, despite an extreme level of intracranial hypertension having been reached [ 6 ], the absence of beat-by-beat variation on intracranial volume impacts the ICP waveform. Moreover, this can explain the particular impact we observed in our study over the P2/P1 ratio, since the P2 is translated as the tidal wave, that is, the spread of blood thru the brain after maximum arterial ejection (ending of systolic phase) [ 22 ].…”
Background: Due to the importance of not mistaking when determining the brain death (BD) diagnostic, reliable confirmatory exams should be performed to enhance its security. This study aims to evaluate the intracranial pressure (ICP) pulse morphology behavior in brain-dead patients through a noninvasive monitoring system. Methods: A pilot case-control study was conducted in adults that met the BD national protocol criteria. Quantitative parameters from the ICP waveforms, such as the P2/P1 ratio, time-to-peak (TTP) and pulse amplitude (AMP) were extracted and analyzed comparing BD patients and health subjects. Results: Fifteen patients were included, and 6172 waveforms were analyzed. ICP waveforms presented substantial differences amidst BD patients when compared to the control group, especially AMP, which had lower values in patients diagnosed with BD (p < 0.0001) and the TTP median (p < 0.00001), but no significance was found for the P2/P1 ratio (p = 0.8). The area under curve for combination of parameters on the BD prediction was 0.77. Conclusions: In this exploratory study, noninvasive ICP waveforms have shown potential as a screening method in patients with suspected brain death. Future studies should be carried out in a larger population.
“…The ICP waveform morphology has its own tracing, similar to that of the arterial pulse waveform, with three frequent peaks: the percussion wave (P1), the tidal wave (P2), and the dicrotic wave (P3) [ 3 ]. Another useful value is the time to peak (TTP), which is defined as the time between the onset of the ICP wave and its highest value [ 9 ].…”
Purpose
Individuals with TBI are at risk of intracranial hypertension (ICH), and monitoring of intracranial pressure (ICP) is usually indicated. However, despite many new noninvasive devices, none is sufficiently accurate and effective for application in clinical practice, particularly in the management of TBIs. This study aimed to compare the noninvasive Brain4Care system (nICP) with invasive ICP (iICP) curve parameters in their ability to predict ICH and functional prognosis in severe TBI.
Methods
Observational, descriptive-analytical, and prospective study of 22 patients between 2018 and 2021, simultaneously monitored with nICP and iICP. The independent variables evaluated were the presence of ICH and functional prognoses. The dependent variables were the P2/P1 pressure ratio metrics, time to peak (TTP), and TTP × P2/P1.
Results
We found a good nonlinear correlation between iICP and nICP waveforms, despite a moderate Pearson’s linear correlation. The noninvasive parameters of P2/P1, P2/P1 × TTP, and TTP were not associated with outcomes or ICH. The nICP P2/P1 ratio showed sensitivity/specificity/accuracy (%) of 100/0/56.3, respectively for 1-month outcomes and 77.8/22.2/50 for 6-month outcomes. The nICP TTP ratio had values of 100/0/56.3 for 1-month and 99.9/42.9/72.2 for 6-month outcomes. The nICP P2/P1 × TTP values were 100/0/56.3 for 1-month outcomes and 81.8/28.6/61.1 for 6-month outcomes.
Conclusion
Brain4Care’s noninvasive method showed low specificity and accuracy and cannot be used as the sole means of monitoring ICP in patients with severe TBI. Future studies with a larger sample of patients with P2 > P1 and new nICP curve parameters are warranted.
Supplementary Information
The online version contains supplementary material available at 10.1007/s00701-023-05580-z.
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