Physiological Effects of Continuous Colored Light Exposure on Mayer Wave Activity in Cerebral Hemodynamics: A Functional Near-Infrared Spectroscopy (fNIRS) Study.

We are increasingly exposed to colored light, but its impact on human physiology is not yet extensively investigated. In the present study we aimed to determine the effects of colored light on human cerebral Mayer wave activity (MWA). We measured oxy- ([O2Hb]), deoxy- ([HHb]), total hemoglobin ([tHb]) concentrations and tissue oxygen saturation (StO2) by functional near-infrared spectroscopy (fNIRS) in the left and right pre-frontal cortex (L-PFC, R-PFC) of 17 subjects (median age: 29 years, 6 women). In a randomized crossover design subjects were exposed to blue, red, green, and yellow LED light for 10 min. Pre-light (8 min, baseline) and post-light (15 min, recovery) conditions were darkness. MWA was calculated from band-pass filtered fNIRS signals (~0.08-0.12 Hz). The medians from the last 3 min of each period (baseline, light exposure, recovery) were statistically analyzed. MWA was increased during red and green light vs. baseline and after blue light exposure in recovery in the L-PFC. MWA differed depending on the chosen frequency range, filter design, and type of signals to analyze (raw intensity, hemoglobin signal from multi-distance method or modified Beer-Lambert law, or within hemoglobin signals).

Simulation of Preterm Neonatal Brain Metabolism During Functional Neuronal Activation Using a Computational Model.

We present a computational model of metabolism in the preterm neonatal brain. The model has the capacity to mimic haemodynamic and metabolic changes during functional activation and simulate functional near-infrared spectroscopy (fNIRS) data. As an initial test of the model's efficacy, we simulate data obtained from published studies investigating functional activity in preterm neonates. In addition we simulated recently collected data from preterm neonates during visual activation. The model is well able to predict the haemodynamic and metabolic changes from these observations. In particular, we found that changes in cerebral blood flow and blood pressure may account for the observed variability of the magnitude and sign of stimulus-evoked haemodynamic changes reported in preterm infants.

Factors that predict bleeding following endoscopic mucosal resection of large colonic lesions.

BACKGROUND AND STUDY AIMS: Endoscopic mucosal resection (EMR) for large colonic laterally spreading tumors (LSTs) is a safe, efficacious, and cost-effective treatment. The most common serious complication is delayed bleeding, which reduces these advantages, but consensus guidelines for large-polyp EMR do not exist. PATIENTS AND METHODS: Data from two large prospective intention-to-treat studies of EMR for colonic LSTs 20 mm or greater in size were analyzed. Data collection was comprehensive, and included patient and lesion characteristics. EMR technique and cessation of anticoagulant and antiplatelet therapy was standardized. Clinically significant delayed bleeding was defined as that requiring hospital admission. RESULTS: EMR was performed on 302 lesions in 288 patients. There was clinically significant delayed bleeding in 21 cases (7 %). Ten underwent colonoscopy. One required angiography. One required surgery after perforation following hemostatic clip placement. There were no deaths. Risk factors for bleeding on multivariate analysis were right colon location [adjusted odds ratio (OR) 4.4, P = 0.01], use of aspirin (OR 6.3, P = 0.005), and age (OR per decade of age 1.70). All bleeds occurred before aspirin was restarted. Patient characteristics, including ASA grade and co-morbidity type, were not predictive. Despite requiring more complex EMR, larger lesion size ( P = 0.2), multiple excisions rather than en bloc resection ( P = 0.1), polyp morphology ( P = 0.2), and previous attempts ( P = 0.5), were not associated with increased risk. CONCLUSIONS: Proximal lesion location is a highly significant risk for clinically significant delayed bleeding following colonic EMR, and this knowledge could form the basis of a targeted therapeutic trial. Recent aspirin use also increases bleeding risk--specific consensus guidelines in this area are required for colonic EMR.

Continuous coloured light altered human brain haemodynamics and oxygenation assessed by systemic physiology augmented functional near-infrared spectroscopy.

Exposure to artificial coloured light is unavoidable in our modern life, but we are only just beginning to understand the impact of coloured light on human physiology. The aim of the present study was to determine effects of coloured light exposure on human systemic and brain physiology using systemic physiology augmented functional near-infrared spectroscopy (SPA-fNIRS). We measured changes in haemoglobin concentrations and tissue oxygen saturation in the left and right prefrontal cortices (L-PFC, R-PFC) by fNIRS, and also recorded skin conductance (SC), partial pressure of end-tidal CO2 (PETCO2), and heart-rate variability variables. 17 healthy adults (median age: 29 years, range: 25-65 years, 6 women) were exposed to blue, red, green, or yellow light for 10 minutes. Pre-light and post-light conditions were in darkness. In the L-PFC the yellow evoked a brain activation. SC and PETCO2 did not change during any of the coloured light exposures, but SC increased and PETCO2 decreased for all colours (except green) in the post-light period. Changes in L-PFC haemoglobin concentration were also observed during the post-light period but have to be interpreted with care, because heart rate and SC increased while PETCO2 decreased. The detected effects are potentially of high relevance for choosing room lighting and may possibly be applied therapeutically.