RAQ: a novel surrogate for the craniospinal pressure-volume relationship

OBJECTIVE The intracranial pressure-volume relation contains information relevant for diagnostics of hydrocephalus and other space-occupying pathologies. We aimed to design a noise-resilient surrogate for this relationship that can be calculated from intracranial pressure (ICP) signals. APPROACH The new surrogate, termed respiratory amplitude quotient (RAQ), characterizes the modulation of the cardiac pulse wave amplitude by the respiratory wave in the ICP time course. RAQ is defined as the ratio of the amplitude of the respiratory wave in the ICP signal to the amplitude of the respiration-induced variation in the course of the cardiac pulse wave amplitude. We validated the calculation of RAQ on synthetically generated ICP waveforms. We further extracted RAQ retrospectively from overnight ICP recordings in a cohort of hydrocephalus patients with aqueductal stenosis, age 55.8 ± 18.0 years, and a comparison group with hydrocephalus diagnosed by morphology in MRI, but not responsive to either external lumbar drainage or ventriculo-peritoneal shunting, age 72.5 ± 6.1 years. RAQ was determined for the full recordings, and separately for periods containing B-waves. MAIN RESULTS We found a mean difference of less than 2% between the calculated values of RAQ and the theoretically determined equivalent descriptors of the synthetic ICP waveforms. In the overnight recordings, we found significantly different RAQ values during B-waves in the aqueductal stenosis (0.86 ± 0.11) and non-responsive hydrocephalus patient groups (1.07 ± 0.20), p = 0.027. In contrast, there was no significant difference in other tested parameters, namely pressure-volume index, elastance coefficient, and resistance to outflow. Neither did we find significant difference when considering RAQ over the full recordings. SIGNIFICANCE Our results indicate that RAQ may function as a potential surrogate for the intracranial pressure-volume relation

RAQ: A Noise-Resistant Calibration-Independent Compliance Surrogate

The intracranial pressure (ICP)-volume relationship contains important information for diagnosing hydrocephalus and other space-occupying pathologies. We aimed to design a new parameter which quantifies the relationship and can be calculated from overnight recordings. The new parameter, the respiratory amplitude quotient (RAQ), characterizes the modulation of the pulse amplitude by the respiratory wave in the ICP time course. RAQ is defined as the ratio of the amplitude of the respiratory wave in the ICP signal to the amplitude of the respiration-induced wave in the course of the heartbeat-dependent pulse amplitude. We tested RAQ on synthetically generated ICP waveforms and found a mean difference of <0.5% between the calculated values of RAQ and the theoretically determined values. We further extracted RAQ from datasets obtained by overnight recording in hydrocephalus patients with a stenosis of the aqueduct and a comparison group finding a significant difference between the RAQ values of either group. Keywords Intracranial pressure Waveform analysis Respiratory amplitude quotient Pressure-volume relationshi

Validation of Knowledge Acquisition for Surgical Process Models

International audienceOBJECTIVE: Surgical Process Models (SPMs) are models of surgical interventions. The objectives of this study are to validate acquisition methods for Surgical Process Models and to assess the performance of different observer populations. DESIGN: The study examined 180 SPM of simulated Functional Endoscopic Sinus Surgeries (FESS), recorded with observation software. About 150,000 single measurements in total were analyzed. MEASUREMENTS: Validation metrics were used for assessing the granularity, content accuracy, and temporal accuracy of structures of SPMs. RESULTS: Differences between live observations and video observations are not statistically significant. Observations performed by subjects with medical backgrounds gave better results than observations performed by subjects with technical backgrounds. Granularity was reconstructed correctly by 90%, content by 91%, and the mean temporal accuracy was 1.8 s. CONCLUSION: The study shows the validity of video as well as live observations for modeling Surgical Process Models. For routine use, the authors recommend live observations due to their flexibility and effectiveness. If high precision is needed or the SPM parameters are altered during the study, video observations are the preferable approach

Significant association of slow vasogenic ICP waves with normal pressure hydrocephalus diagnosis

OBJECTIVE: We aimed to test whether there is an association of slow vasogenic wave (SVW) occurrence with positive response to external lumbar drainage (ELD) and ventriculoperitoneal shunting and to design a method for the recognition and quantification of SVWs in the intracranial pressure (ICP) signal. MATERIALS AND METHODS: We constructed SVW templates using normalized sine waves. We calculated the cross-correlation between the respective SVW template and the ICP signal. This was followed by shifting the templates forward and performing the cross-correlation analysis again until the end of the recording. Cross-correlation values above a threshold were considered to be indicative of SVWs. This threshold was previously determined and validated on a sample of ICP records of six patients. We calculated the root mean square of the recognized SVW periods as a measure of signal strength. Time-averaged signal strength was calculated over the full recording time (ICP) and over the wave periods (ICP). RESULTS: We determined ICPand ICPin recordings of 2 groups of patients presenting with Hakim's triad: 26 normal pressure hydrocephalus (NPH) patients and 20 non-NPH patients. We then tested whether there was an association between ICPor ICPand the respective diagnosis using a Mann-Whitney test. We found significant association between ICP(p = 0.014) and ICP(p = 0.022) and the diagnoses. CONCLUSIONS: The described method based on pattern recognition in the time domain is suitable for the detection and quantification of SVWs in ICP signals. We found a significant association between the occurrence of SVWs and independent NPH diagnosis

Visualization Options for Surgical Workflows

International audienc

Visualization Options for Surgical Workflows

International audienc

Linking Top-Level Ontologies and Surgical Workflows

International audienc

Gap Analysis Regarding Prognostication in Neurocritical Care: A Joint Statement from the German Neurocritical Care Society and the Neurocritical Care Society

BACKGROUND/OBJECTIVE: Prognostication is a routine part of the delivery of neurocritical care for most patients with acute neurocritical illnesses. Numerous prognostic models exist for many different conditions. However, there are concerns about significant gaps in knowledge regarding optimal methods of prognostication. METHODS: As part of the Arbeitstagung NeuroIntensivMedizin meeting in February 2018 in Wurzburg, Germany, a joint session on prognostication was held between the German NeuroIntensive Care Society and the Neurocritical Care Society. The purpose of this session was to provide presentations and open discussion regarding existing prognostic models for eight common neurocritical care conditions (aneurysmal subarachnoid hemorrhage, intracerebral hemorrhage, acute ischemic stroke, traumatic brain injury, traumatic spinal cord injury, status epilepticus, Guillain-Barre Syndrome, and global cerebral ischemia from cardiac arrest). The goal was to develop a qualitative gap analysis regarding prognostication that could help inform a future framework for clinical studies and guidelines. RESULTS: Prognostic models exist for all of the conditions presented. However, there are significant gaps in prognostication in each condition. Furthermore, several themes emerged that crossed across several or all diseases presented. Specifically, the self-fulfilling prophecy, lack of accounting for medical comorbidities, and absence of integration of in-hospital care parameters were identified as major gaps in most prognostic models. CONCLUSIONS: Prognostication in neurocritical care is important, and current prognostic models are limited. This gap analysis provides a summary assessment of issues that could be addressed in future studies and evidence-based guidelines in order to improve the process of prognostication