SignificanceThe optical measurement of cerebral oxygen metabolism was evaluated.AimCompare optically derived cerebral signals to the electroencephalographic bispectral index (BIS) sensors to monitor propofol-induced anesthesia during surgery.ApproachRelative cerebral metabolic rate of oxygen (rCMRO2) and blood flow (rCBF) were measured by time-resolved and diffuse correlation spectroscopies. Changes were tested against the relative BIS (rBIS) ones. The synchronism in the changes was also assessed by the R-Pearson correlation.ResultsIn 23 measurements, optically derived signals showed significant changes in agreement with rBIS: during propofol induction, rBIS decreased by 67% [interquartile ranges (IQR) 62% to 71%], rCMRO2 by 33% (IQR 18% to 46%), and rCBF by 28% (IQR 10% to 37%). During recovery, a significant increase was observed for rBIS (48%, IQR 38% to 55%), rCMRO2 (29%, IQR 17% to 39%), and rCBF (30%, IQR 10% to 44%). The significance and direction of the changes subject-by-subject were tested: the coupling between the rBIS, rCMRO2, and rCBF was witnessed in the majority of the cases (14/18 and 12/18 for rCBF and 19/21 and 13/18 for rCMRO2 in the initial and final part, respectively). These changes were also correlated in time (R > 0.69 to R = 1, p-values < 0.05).ConclusionsOptics can reliably monitor rCMRO2 in such conditions.
The HEMOCOVID-19 clinical trial, carried out in 10 hospitals from 5 countries, aims to non-invasively assess, through continuous-wave near-infrared spectroscopy (CW-NIRS), the microvascular and endothelial health in COVID-19 patients admitted to intensive care. We achieve this by performing a vascular occlusion test on the forearm muscle while continuously measuring local tissue oxygen saturation and hemoglobin concentration. We found significant alterations in systemic microcirculation of COVID-19 patients with respect to healthy subjects (i.e. slower deoxygenation during the ischemia and reoxygenation after releasing the cuff, and lower hyperemic response). In addition, we found that, within the group of COVID-19 patients, the systemic microcirculation alterations correlate with severity of pulmonary disease.
We present the HEMOCOVID-19 study spanning four countries and eight hospitals where near-infrared spectroscopy is utilized to evaluate microvascular and endothelial health of severe COVID-19 patients at the intensive care.
Obstructive apnea causes periodic changes in cerebral and systemic hemodynamics, which may contribute to the increased risk of cerebrovascular disease of patients with obstructive sleep apnea (OSA) syndrome. The improved understanding of the consequences of an apneic event on the brain perfusion may improve our knowledge of these consequences and then allow for the development of preventive strategies. Our aim was to characterize the typical microvascular, cortical cerebral blood flow (CBF) changes in an OSA population during an apneic event. Sixteen patients (age 58 ± 8 years, 75% male) with a high risk of severe OSA were measured with a polysomnography device and with diffuse correlation spectroscopy (DCS) during one night of sleep with 1365 obstructive apneic events detected. All patients were later confirmed to suffer from severe OSA syndrome with a mean of 83 ± 15 apneas and hypopneas per hour. DCS has been shown to be able to characterize the microvascular CBF response to each event with a sufficient contrast-to-noise ratio to reveal its dynamics. It has also revealed that an apnea causes a peak increase of microvascular CBF (30 ± 17 % ) at the end of the event followed by a drop (−20 ± 12 % ) similar to what was observed in macrovascular CBF velocity of the middle cerebral artery. This study paves the way for the utilization of DCS for further studies on these populations.
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