Low frequency oscillations assessed by diffuse speckle contrast analysis for foot angiosome concept

An angiosome refers to a 3D tissue volume that is vascularized by a single artery and is a relatively new concept that is useful in vascular surgery; however, the direct relationship between arterial blood flow and micro-perfusion is still controversial. Here, we propose a diffuse speckle contrast analysis (DSCA), which is an emerging tissue perfusion monitoring modality, to investigate the correlations among low frequency oscillations (LFOs) measured from different areas on the feet of healthy subjects. We obtained reproducible results from the correlation analyses of LFOs, and their physiological implications were discussed. In order to confirm the changes in the frequency oscillations, we analyzed and compared the power spectral density changes due to heart rate variability in the electrocardiographic signal during reactive hyperemia and head-up tilt protocols.

Data-Driven Calibration Estimation for Robust Remote Pulse-Oximetry

Pulse-oximetry has become a core monitoring modality in most fields of medicine. Typical dual-wavelength pulse-oximeters estimate blood oxygen saturation (SpO2) levels from a relationship between the amplitudes of red and infrared photoplethysmographic (PPG) waveforms. When captured with a camera, the PPG waveforms are much weaker and consequently the measurement is more sensitive to distortions and noises. Therefore, an indirect method has recently been proposed where, instead of extracting the relative amplitudes from the individual waveforms, the waveforms are linearly combined to construct a collection of pulse signals with different pulse signatures, each corresponding to a specific oxygen saturation level. This method has been shown to outperform the conventional ratio-of-ratios based methods, especially when adding a third wavelength. Adding wavelengths, however, complicates the calibration. Inaccuracies in the calibration model threaten the performance of the method. Opto-physiological models have been shown earlier to provide useful calibration parameter estimates. In this paper, we show that the accuracy can be improved using a data-driven approach. We performed 5-fold cross validation on recordings with variations in oxygen saturation and optimized for pulse quality. All evaluated wavelength combinations, also without visible red, meet the required ISO standard accuracy with the calibration from the proposed method. This scalable approach is not only helpful to fine-tune the calibration model, but even allows computation of the calibration model parameters from scratch without prior knowledge of the data acquisition details, i.e., the properties of camera and illumination.

Comparison of cerebrovascular reactivity tests: a pilot human study

In neurosurgery intensive care units, cerebrovascular reactivity tests for neuromonitoring are used to evaluate the status of cerebral blood flow autoregulation; lack of autoregulation indicates a poor patient outcome. The goal of neuromonitoring is to prevent secondary injuries following a primary central nervous system injury, when the brain is vulnerable to further compromise due to hypoxia, ischemia and disturbances in cerebral blood flow and intracranial pressure. Ideally, neuromonitoring would be noninvasive and continuous. This study compares cerebrovascular reactivity monitored by rheoencephalography, a noninvasive continuous monitoring modality, to cerebrovascular reactivity measured by currently used neuromonitoring modalities: transcranial Doppler, near infrared spectroscopy and laser Doppler flowmetry. Fourteen healthy volunteer subjects were measured. The tests used for comparison of cerebrovascular reactivity were breath-holding, hyperventilation, CO2 inhalation, the Valsalva maneuver, and the Trendelenburg and reverse Trendelenburg positions. Data for all modalities measured were recorded by computers and processed off line. All measured modalities reflected cerebrovascular reactivity with variabilities. Breath-holding, CO2 inhalation, and the Valsalva maneuver caused CO2 increase and consequent brain vasodilatation; hyperventilation caused CO2 decrease and brain vasoconstriction. The Trendelenburg and reverse Trendelenburg positions caused extracranial blood volume changes, which masked intracranial cerebrovascular reactivity. The hyperventilation test proved ineffective for measuring cerebrovascular reactivity with rheoencephalography due to respiratory artifacts. Some discrepancies among the

Multimodal Neuromonitoring: Current Scenario in Neurocritical Care

Multimodal neuromonitoring (NM) is the concept of integrating various tools and data to understand brain physiology and guide therapeutic interventions to prevent secondary brain injury. There exists a range of invasive/noninvasive and global/regional monitors of cerebral hemodynamics, oxygenation, metabolism, and electrophysiology that can be used to guide treatment decisions after neurological insult. No single monitoring modality is ideal for all patients. Simultaneous assessment of cerebral hemodynamics, oxygenation, and metabolism allows individualized patient care. The ability to analyze these advanced data for real-time clinical care, however, remains intuitive and primitive. Advanced informatics is promising and may provide us a supportive tool to interpret physiological events and guide pathophysiological-based therapeutic decisions. Available literature is not robust regarding multimodality NM and favorable patient outcome. This narrative review is undertaken to know the status and recent advancement of multimodal NM in neurocritical care.

Study of Intracranial Pressure Monitoring In Traumatic Brain Injury

Intracranial pressure monitoring is considered the standard of care for severe traumatic brain injury and is used frequently. However, the efficacy of treatment based on monitoring in improving the outcome has not been rigorously assessed. We conducted a trial in which we included 26 patients of all types of traumatic brain injury (TBI) and they were monitored for intracranial pressure by Conventional fluid filled system with a manometer (Group 1) and compared with the Fiber optic transducer-tipped intracranial pressure monitoring system (Group 2).The main aim of this study was to examine the relationship between Intracranial Pressure (ICP) monitoring and in-hospital mortality. The median length of stay in the ICU was similar in the two groups (12 days in the conventional pressure-monitoring group and 9 days in the new fiber optic group; P=0.25), the number of days of brain-specific treatments (e.g., administration of hyperosmolar fluids and the use of hyperventilation) in the ICU was similar in both groups. The distribution of serious adverse events was similar in the two groups. We concluded that ICP monitoring (as is any monitoring modality) is a useful guide for management. The outcomes are decided by the differences in management protocols that the knowledge of the said parameter brings about. ICP monitoring is recommended for the better management of traumatic brain injury and fiber optic ICP monitoring seems to be beneficial than using the conventional methods of ICP monitoring with manometer.Nepal Journal of Neuroscience, Volume 15, Number 2, 2018, page: 23-29

Multimodal Neuromonitoring in Neurocritical Care

Neuromonitoring is important for patients with acute brain injury. The bedside neurologic examination is standard for neurologic monitoring; however, a clinical examination may not reliably detect subtle changes in intracranial physiology. Changes found during neurologic examinations are often late signs. The assessment of multiple physiological variables in real time can provide new clinical insights into treatment decisions. No single monitoring modality is ideal for all patients. Simultaneous assessment of cerebral hemodynamics, oxygenation, and metabolism, such as in multimodal monitoring, allows an innovative approach to individualized patient care.

Modern Endoscopic Imaging in Diagnosis and Surveillance of Inflammatory Bowel Disease Patients

Endoscopy remains the most important diagnostic and monitoring modality in the management of inflammatory bowel disease. Advances in imaging have progressively added new tools into the armamentarium of endoscopists with the goal of more accurate, sensitive, and accessible visual diagnoses for the benefit of patients with gastrointestinal diseases. Here, we review the relevant literature regarding commonly used endoscopic techniques (dye-based and digital chromoendoscopy, high-definition endoscopy, capsule endoscopy, and endosonography), as well as advanced and experimental technologies (full-spectrum endoscopy, endocytoscopy, autofluorescence, laser endoscopy, and endomicroscopy, including molecular imaging), applicable to inflammatory bowel diseases and emerging for implementation into everyday practice. Additionally, we discuss future directions and techniques as candidates for a superior inflammation imaging in the diagnosis and prediction of therapeutic response.

Intracranial pressure monitoring in the ICU

Intracranial pressure (ICP) measurement is an established monitoring modality in the ICU and can aid prognostication after acute brain injury. ICP monitoring is recommended in all patients with severe traumatic brain injury (TBI), and an abnormal cranial computed tomographic (CT) scan and the ability to control ICP is associated with improved outcome after TBI. The lessons from TBI studies can also be applied to other acute pathologies of the central nervous system where ICP can be increased. ICP measurement can warn of impending disaster and allow intervention. Furthermore, measurement of ICP allows the calculation of cerebral perfusion pressure (CPP) and maintenance of CPP may help to ensure adequate cerebral oxygen delivery. Various systems exist to monitor ICP. A recent trial in two South American countries suggested that ICP-guided management and management guided by clinical examination and repeated imaging produced equivalent outcomes. Although this trial currently provides the best evidence regarding the impact of monitoring ICP on outcome following TBI, but because of the inadequate power and questionable external validity, the generalizability of the results remain to be confirmed.