Impact of windscreen scatter on laser eye dazzle.

This study investigates the extent to which a windscreen affects the severity of laser eye dazzle (disability glare produced by a laser) experienced by a human observer. Windscreen scatter measurements were taken for a range of windscreens in a variety of conditions, showing that windscreen scatter is similar in magnitude to scatter from the human eye. Human subject experiments verified that obscuration angles caused by laser eye dazzle could be increased by the presence of a windscreen when comparing a dirty automobile windscreen to an eye-only condition with a 532-nm laser exposure. However, a light aircraft windscreen with lower scatter did not exhibit increased obscuration angles at 532 nm, and neither windscreen exhibited an increase at 635 nm. A theoretical analysis of laser eye dazzle, using measured windscreen scatter functions, has provided insight into the delicate interplay between scatter, transmission and the angular extent of dazzle. A model based on this analysis has been shown to be a useful tool to predict the impact of windscreens on laser eye dazzle, with the goal of informing future updates to the authors' laser eye dazzle safety framework.

Wavelength and ambient luminance dependence of laser eye dazzle.

A series of experiments has been conducted to quantify the effects of laser wavelength and ambient luminance on the severity of laser eye dazzle experienced by human subjects. Eight laser wavelengths in the visible spectrum were used (458-647 nm) across a wide range of ambient luminance conditions (0.1-10,000 cd·m-2). Subjects were exposed to laser irradiance levels up to 600 µW·cm-2 and were asked to recognize the orientation of optotypes at varying eccentricities up to 31.6 deg of visual angle from the laser axis. More than 40,000 data points were collected from 14 subjects (ages 23-64), and these were consolidated into a series of obscuration angles for comparison to a theoretical model of laser eye dazzle. Scaling functions were derived to allow the model to predict the effects of laser dazzle on vision more accurately by including the effects of ambient luminance and laser wavelength. The updated model provides an improved match to observed laser eye dazzle effects across the full range of conditions assessed. The resulting model will find use in a variety of laser safety applications, including the estimation of maximum dazzle exposure and nominal ocular dazzle distance values.

Measuring the contribution of atmospheric scatter to laser eye dazzle.

An experiment has been conducted to determine the contribution of atmospheric scatter to the severity of the dazzle experienced by a human under illumination from a visible laser. A 15 W 532 nm laser was propagated over a 380 m outdoor range in San Antonio, Texas, over nine data collection sessions spanning June and July 2014. A narrow acceptance angle detector was used to measure scattered laser radiation within the laser beam at different angles from its axis. Atmospheric conditions were logged via a local weather station, and air quality data were taken from a nearby continuous air monitoring station. The measured laser irradiance data showed very little variation across the sessions and a single fitting equation was derived for the atmospheric scatter function. With very conservative estimates of the scatter from the human eye, atmospheric scatter was found to contribute no more than 5% to the overall veiling luminance across the scene for a human observer experiencing laser eye dazzle. It was concluded that atmospheric scatter does not make a significant contribution to laser eye dazzle for short-range laser engagements in atmospheres of good to moderate air quality, which account for 99.5% of conditions in San Antonio, Texas.

Hospital Observation Upon Reversal (HOUR) With Naloxone: A Prospective Clinical Prediction Rule Validation Study.

OBJECTIVE: St. Paul's Early Discharge Rule was derived to determine which patients could be safely discharged from the emergency department after a 1-hour observation period following naloxone administration for opiate overdose. The rule suggested that patients could be safely discharged if they could mobilize as usual and had a normal oxygen saturation, respiratory rate, temperature, heart rate, and Glasgow Coma Scale score. Validation of the St. Paul's Early Discharge Rule is necessary to ensure that these criteria are appropriate to apply to patients presenting after an unintentional presumed opioid overdose in the context of emerging synthetic opioids and expanded naloxone access. METHODS: In this prospective, observational validation study, emergency medicine providers assessed patients 1 hour after administration of prehospital naloxone. Unlike in the derivation study the threshold for normal oxygen saturation was set at 95% and patients were not immediately discharged after a normal 1-hour evaluation. Patients were judged to have a normal 1-hour evaluation if all six criteria of the rule were met. Patients were judged to have an adverse event (AE) if they had one or more of the preestablished AEs. RESULTS: A total of 538 patients received at least one administration of prehospital naloxone, were transported to the study hospital, and had a 1-hour evaluation performed by a provider. AEs occurred in 82 (15.4%) patients. The rule exhibited a sensitivity of 84.1% (95% confidence interval [CI] = 76.2%-92.1%), a specificity of 62.1% (95% CI = 57.6%-66.5%), and a negative predictive value of 95.6% (95% CI = 93.3%-97.9%). Only one patient with a normal 1-hour evaluation subsequently received additional naloxone following a presumed heroin overdose. CONCLUSION: This rule may be used to risk stratify patients for early discharge following naloxone administration for suspected opioid overdose.

Femoral nerve block for diaphyseal and distal femoral fractures in the emergency department. Surgical technique.

BACKGROUND: Diaphyseal and distal femoral fractures are painful injuries that are frequently seen in patients requiring a trauma work-up in the hospital emergency department prior to definitive management. The purpose of this study was to determine whether a femoral nerve block administered in the emergency department could provide better pain relief for patients with femoral fractures than currently used pain management practices. METHODS: Patients who presented with an acute diaphyseal or distal femoral fracture were identified as potential candidates for this study. Eligible patients were randomized by medical record number to receive either (a) the femoral nerve block (20 mL of 0.5% bupivacaine) along with standard pain management or (b) standard pain management alone (typically intravenous narcotics). The pain was assessed with use of a visual analog scale at the initial evaluation and at five, fifteen, thirty, sixty, and ninety minutes following the initial evaluation. Fifty-four patients were enrolled in the study from April 2005 to May 2006. Thirty-one patients received a femoral nerve block, and twenty-three patients received standard pain management alone. RESULTS: Baseline scores on the visual analog pain scale did not differ between the groups at the initial evaluation. The patients who received a femoral nerve block (along with standard pain management) had significantly lower pain scores at five, fifteen, thirty, sixty, and ninety minutes following the block than did the patients who received standard pain management alone (p < 0.001). The score on the visual analog pain scale across these time points was an average of 3.6 points less (on a 10-point scale) for those who received the block. There were no infections, paresthesias, or other complications related to the femoral nerve block. CONCLUSIONS: The acute pain of a diaphyseal or distal femoral fracture can be significantly decreased through the use of a femoral nerve block, which can be administered safely in the hospital emergency department.

Femoral nerve block for diaphyseal and distal femoral fractures in the emergency department.

BACKGROUND: Diaphyseal and distal femoral fractures are painful injuries that are frequently seen in patients requiring a trauma work-up in the hospital emergency department prior to definitive management. The purpose of this study was to determine whether a femoral nerve block administered in the emergency department could provide better pain relief for patients with femoral fractures than currently used pain management practices. METHODS: Patients who presented with an acute diaphyseal or distal femoral fracture were identified as potential candidates for this study. Eligible patients were randomized by medical record number to receive either (a) the femoral nerve block (20 mL of 0.5% bupivacaine) along with standard pain management or (b) standard pain management alone (typically intravenous narcotics). The pain was assessed with use of a visual analog scale at the initial evaluation and at five, fifteen, thirty, sixty, and ninety minutes following the initial evaluation. Fifty-four patients were enrolled in the study from April 2005 to May 2006. Thirty-one patients received a femoral nerve block, and twenty-three patients received standard pain management alone. RESULTS: Baseline scores on the visual analog pain scale did not differ between the groups at the initial evaluation. The patients who received a femoral nerve block (along with standard pain management) had significantly lower pain scores at five, fifteen, thirty, sixty, and ninety minutes following the block than did the patients who received standard pain management alone (p < 0.001). The score on the visual analog pain scale across these time-points was an average of 3.6 points less (on a 10-point scale) for those who received the block. There were no infections, paresthesias, or other complications related to the femoral nerve block. CONCLUSIONS: The acute pain of a diaphyseal or distal femoral fracture can be significantly decreased through the use of a femoral nerve block which can be administered safely in the hospital emergency department.