Relationship between the shape of intracranial pressure pulse waveform and computed tomography characteristics in patients after traumatic brain injury.

BACKGROUND: Midline shift and mass lesions may occur with traumatic brain injury (TBI) and are associated with higher mortality and morbidity. The shape of intracranial pressure (ICP) pulse waveform reflects the state of cerebrospinal pressure-volume compensation which may be disturbed by brain injury. We aimed to investigate the link between ICP pulse shape and pathological computed tomography (CT) features. METHODS: ICP recordings and CT scans from 130 TBI patients from the CENTER-TBI high-resolution sub-study were analyzed retrospectively. Midline shift, lesion volume, Marshall and Rotterdam scores were assessed in the first CT scan after admission and compared with indices derived from the first 24 h of ICP recording: mean ICP, pulse amplitude of ICP (AmpICP) and pulse shape index (PSI). A neural network model was applied to automatically group ICP pulses into four classes ranging from 1 (normal) to 4 (pathological), with PSI calculated as the weighted sum of class numbers. The relationship between each metric and CT measures was assessed using Mann-Whitney U test (groups with midline shift > 5 mm or lesions > 25 cm3 present/absent) and the Spearman correlation coefficient. Performance of ICP-derived metrics in identifying patients with pathological CT findings was assessed using the area under the receiver operating characteristic curve (AUC). RESULTS: PSI was significantly higher in patients with mass lesions (with lesions: 2.4 [1.9-3.1] vs. 1.8 [1.1-2.3] in those without; p << 0.001) and those with midline shift (2.5 [1.9-3.4] vs. 1.8 [1.2-2.4]; p < 0.001), whereas mean ICP and AmpICP were comparable. PSI was significantly correlated with the extent of midline shift, total lesion volume and the Marshall and Rotterdam scores. PSI showed AUCs > 0.7 in classification of patients as presenting pathological CT features compared to AUCs ≤ 0.6 for mean ICP and AmpICP. CONCLUSIONS: ICP pulse shape reflects the reduction in cerebrospinal compensatory reserve related to space-occupying lesions despite comparable mean ICP and AmpICP levels. Future validation of PSI is necessary to explore its association with volume imbalance in the intracranial space and a potential complementary role to the existing monitoring strategies.

Analysis of intracranial pressure pulse waveform in traumatic brain injury patients: a CENTER-TBI study.

OBJECTIVE: Intracranial pressure (ICP) pulse waveform analysis may provide valuable information about cerebrospinal pressure-volume compensation in patients with traumatic brain injury (TBI). The authors applied spectral methods to analyze ICP waveforms in terms of the pulse amplitude of ICP (AMP), high frequency centroid (HFC), and higher harmonics centroid (HHC) and also used a morphological classification approach to assess changes in the shape of ICP pulse waveforms using the pulse shape index (PSI). METHODS: The authors included 184 patients from the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) High-Resolution Sub-Study in the analysis. HFC was calculated as the average power-weighted frequency within the 4- to 15-Hz frequency range of the ICP power density spectrum. HHC was defined as the center of mass of the ICP pulse waveform harmonics from the 2nd to the 10th. PSI was defined as the weighted sum of artificial intelligence-based ICP pulse class numbers from 1 (normal pulse waveform) to 4 (pathological waveform). RESULTS: AMP and PSI increased linearly with mean ICP. HFC increased proportionally to ICP until the upper breakpoint (average ICP of 31 mm Hg), whereas HHC slightly increased with ICP and then decreased significantly when ICP exceeded 25 mm Hg. AMP (p < 0.001), HFC (p = 0.003), and PSI (p < 0.001) were significantly greater in patients who died than in patients who survived. Among those patients with low ICP (< 15 mm Hg), AMP, PSI, and HFC were greater in those with poor outcome than in those with good outcome (all p < 0.001). CONCLUSIONS: Whereas HFC, AMP, and PSI could be used as predictors of mortality, HHC may potentially serve as an early warning sign of intracranial hypertension. Elevated HFC, AMP, and PSI were associated with poor outcome in TBI patients with low ICP.

Intracranial Pressure Pulse Morphology-based Definition of Life-threatening Intracranial Hypertension Episodes.

Intracranial hypertension (IH) is associated with poor outcome in traumatic brain injury (TBI) patients and must be avoided to prevent secondary brain injury. In clinical practice the most common method of IH detection is the calculation of the mean value of intracranial pressure (ICP) and the therapeutic intervention is usually introduced when the mean exceeds a certain threshold. This threshold, however, is rather individual for each patient than universal for all. Impaired cerebrovascular reactivity and reduced intracranial compliance are associated with raised ICP. This work explores a new definition of life-threatening hypertension (LTH) which accounts for the state of cerebral compliance. In the proposed method, changes in compliance are analysed through identification of likely pathological and/or pathological shapes of ICP pulse waveforms using a neural network. In terms of predictive power for mortality in TBI, detection of both shape clasess of ICP pulse waveforms during raised ICP offers similar results to previously proposed LTH definition accounting for the state of cerebrovascular reactivity (77.8% vs 76.9% accuracy, respectively). On the other hand, the fully pathological shapes of ICP pulses are present during ICP rises almost only in recordings of patients who died: out of 216 analysed patients only 6% of surviving and as many as 42% of deceased patients developed this type of LTH event. The stricter definition of LTH events including only pathological shape of ICP pulses presents the highest accuracy among the analysed approaches for mortality prediction (87.9%). Clinical relevance-Reliable detection of potentially life-threatening episodes of ICP elevation offers the possibility of improving clinical management of TBI by identifying the patients at risk of unfavourable outcome.

End-to-End Automatic Morphological Classification of Intracranial Pressure Pulse Waveforms Using Deep Learning.

OBJECTIVE: Mean intracranial pressure (ICP) is commonly used in the management of patients with intracranial pathologies. However, the shape of the ICP signal over a single cardiac cycle, called ICP pulse waveform, also contains information on the state of the craniospinal space. In this study we aimed to propose an end-to-end approach to classification of ICP waveforms and assess its potential clinical applicability. METHODS: ICP pulse waveforms obtained from long-term ICP recordings of 50 neurointensive care unit (NICU) patients were manually classified into four classes ranging from normal to pathological. An additional class was introduced to simultaneously identify artifacts. Several deep learning models and data representations were evaluated. An independent testing dataset was used to assess the performance of final models. Occurrence of different waveform types was compared with the patients' clinical outcome. RESULTS: Residual Neural Network using 1-D ICP signal as input was identified as the best performing model with accuracy of 93% in the validation and 82% in the testing dataset. Patients with unfavorable outcome exhibited significantly lower incidence of normal waveforms compared to the favorable outcome group even at ICP levels below 20 mm Hg (median [first-third quartile]: 9 [1-36]% vs. 63 [52-88] %, p = 0.002). CONCLUSIONS: Results of this study confirm the possibility of analyzing ICP pulse waveform morphology in long-term recordings of NICU patients. Proposed approach could potentially be used to provide additional information on the state of patients with intracranial pathologies beyond mean ICP.

Analysis of the Shape of Intracranial Pressure Pulse Waveform in Traumatic Brain Injury Patients.

Intracranial pressure (ICP) pulse waveform, i.e., the shape of the ICP signal over a single cardiac cycle, is regarded as a potential source of information about intracranial compliance. In this study we aimed to compare the results of automatic classification of ICP pulse shapes on a scale from normal to pathological with other ICP pulse-derived metrics. Additionally, identification of artifacts was performed simultaneously with pulse classification to assess the effect of artifact removal on the results. Data from 35 traumatic brain injury (TBI) patients were analyzed retrospectively in terms of dominant waveform shape, mean ICP, mean amplitude of ICP (AmpICP), mean index of compensatory reserve (RAP index), and their association with the patient's clinical outcome. Our results show that patients with poor outcome exhibit more pathological waveform shape than patients with good outcome. More pathological ICP pulse shape is associated with higher mean ICP, mean AmpICP, and RAP.Clinical relevance- In the clinical setting, ICP pulse waveform analysis could potentially be used to complement the commonly monitored mean ICP and improve the assessment of intracranial compliance in TBI patients. Artifact removal from the ICP signal could reduce the frequency of false positive detection of clinically adverse events.