Heart Rate Variability Can Detect Blunt Traumatic Brain Injury Within the First Hour.

INTRODUCTION: In patients with multi-organ system trauma, the diagnosis of coinciding traumatic brain injury can be difficult due to injuries from the hemorrhagic shock that confound clinical and radiographic signs of traumatic brain injury. In this study, a novel technique using heart rate variability was developed in a porcine model to detect traumatic brain injury early in the setting of hemorrhagic shock without the need for radiographic imaging or clinical exam. METHODS: A porcine model of hemorrhagic shock was used with an arm of swine receiving hemorrhagic shock alone and hemorrhagic shock with traumatic brain injury. High-resolution heart rate frequencies were collected at different time intervals using waveforms based on voltage delivered from the heart rate monitor. Waveforms were analyzed to assess statistically significant differences between heart rate variability parameters in those with hemorrhagic shock and traumatic brain injury versus those with only hemorrhagic shock. Stochastic analysis was used to assess the validity of results and create a model by machine learning to better assess the presence of traumatic brain injury. RESULTS: Significant differences were found in several heart rate variability parameters between the two groups. Additionally, significant differences in heart rate variability parameters were found in swine within 1 hour of inducing hemorrhage in those with traumatic brain injury versus those without. These results were confirmed with stochastic analysis and machine learning was used to generate a model which determined the presence of traumatic brain injury in the setting of hemorrhage shock with 91.6% accuracy. CONCLUSIONS:  Heart rate variability represents a promising diagnostic tool to aid in the diagnosis of traumatic brain injury within 1 hour of injury.

Narrative persuasion and stigma: Using news accounts to denormalize texting while driving.

Despite nearly universal texting while driving bans in U.S. states, distracted driving still poses a major risk for American motorists and pedestrians on a daily basis. We argue texting while driving behavior, due to its cultural, social, and psychological motivations, may be addressed by cultivating a stigma to denormalize TWD much in the same way public health campaigns and bans did with tobacco use. While extant strategies may similarly stigmatize this risky behavior, we contend the stigmatizing effect of news narratives offers an untapped and unexamined resource. In this paper we draw on emergent findings in narrative persuasion work to present an exploratory analysis and evidence indicates news narratives, through narrative engagement, can both stigmatize TWD behavior and diminish attitudes toward distracted driving. These initial findings are then validated against an independent sample. If applied widely, this method may be applied to increase social pressure against distracted driving, leading to fewer people engaging in TWD behavior, and making roads safer.

Accelerated Failure Time Survival Model to Analyze Morris Water Maze Latency Data.

Traumatic brain injury (TBI) induces cognitive deficits clinically and in animal models. Learning and memory testing is critical when evaluating potential therapeutic strategies and treatments to manage the effects of TBI. We evaluated three data analysis methods for the Morris water maze (MWM), a learning and memory assessment widely used in the neurotrauma field, to determine which statistical tool is optimal for MWM data. Hidden platform spatial MWM data aggregated from three separate experiments from the same laboratory were analyzed using 1) a logistic regression model, 2) an analysis of variance (ANOVA) model, and 3) an accelerated failure time (AFT) time-to-event model. The logistic regression model showed no significant evidence of differences between treatments among any swims over all days of the study, p > 0.11. Although the ANOVA model found significant evidence of differences between sham and TBI groups on three out of four swims on the third day, results are potentially biased due to the failure of this model to account for censoring. The time-to-event AFT model showed significant differences between sham and TBI over all swims on the third day, p < 0.045, taking censoring into account. We suggest AFT models should be the preferred analytical methodology for latency to platform associated with MWM studies.

Multivariate physiological recordings in an experimental hemorrhage model.

In this paper we describe a data set of multivariate physiological measurements recorded from conscious sheep (N = 8; 37.4 ± 1.1 kg) during hemorrhage. Hemorrhage was experimentally induced in each animal by withdrawing blood from a femoral artery at two different rates (fast: 1.25 mL/kg/min; and slow: 0.25 mL/kg/min). Data, including physiological waveforms and continuous/intermittent measurements, were transformed to digital file formats (European Data Format [EDF] for waveforms and Comma-Separated Values [CSV] for continuous and intermittent measurements) as a comprehensive data set and stored and publicly shared here (Appendix A). The data set comprises experimental information (e.g., hemorrhage rate, animal weight, event times), physiological waveforms (arterial and central venous blood pressure, electrocardiogram), time-series records of non-invasive physiological measurements (SpO2, tissue oximetry), intermittent arterial and venous blood gas analyses (e.g., hemoglobin, lactate, SaO2, SvO2) and intermittent thermodilution cardiac output measurements. A detailed explanation of the hemodynamic and pulmonary changes during hemorrhage is available in a previous publication (Scully et al., 2016) [1].

Temporal plasticity in auditory cortex improves neural discrimination of speech sounds.

BACKGROUND: Many individuals with language learning impairments exhibit temporal processing deficits and degraded neural responses to speech sounds. Auditory training can improve both the neural and behavioral deficits, though significant deficits remain. Recent evidence suggests that vagus nerve stimulation (VNS) paired with rehabilitative therapies enhances both cortical plasticity and recovery of normal function. OBJECTIVE/HYPOTHESIS: We predicted that pairing VNS with rapid tone trains would enhance the primary auditory cortex (A1) response to unpaired novel speech sounds. METHODS: VNS was paired with tone trains 300 times per day for 20 days in adult rats. Responses to isolated speech sounds, compressed speech sounds, word sequences, and compressed word sequences were recorded in A1 following the completion of VNS-tone train pairing. RESULTS: Pairing VNS with rapid tone trains resulted in stronger, faster, and more discriminable A1 responses to speech sounds presented at conversational rates. CONCLUSION: This study extends previous findings by documenting that VNS paired with rapid tone trains altered the neural response to novel unpaired speech sounds. Future studies are necessary to determine whether pairing VNS with appropriate auditory stimuli could potentially be used to improve both neural responses to speech sounds and speech perception in individuals with receptive language disorders.

Inaccuracy of Urine Output Measurements due to Urinary Retention in Catheterized Patients in the Burn ICU.

Electronic urinary output monitors, intended to provide urine output information to guide fluid therapy during burn resuscitation, can be inaccurate because of airlocks causing urine retention in the drainage tube and bladder. In this study, the authors explore the effects of airlock formation on urine output measured using an electronic urinary output monitor connected to either a standard commercial drainage tubing system or a drainage tubing system with an automated airlock clearing mechanism. In a multicenter study in the burn intensive care unit, urine output was compared between 10 control patients with a standard commercial drainage tubing system and 10 test patients with a novel automated airlock clearing drainage tubing system. The comparison was focused on identifying the number and magnitude of surges in urinary output because of airlocks and associated periods of false oliguria. In the control group, 5 of 10 (50%) patients had drainage line flow impediments from 8 airlocks. In addition, control patients experienced six associated periods of false oliguria. Airlock surge volumes ranged from 50 to 329 ml, and false oliguria duration ranged from 39.4 to 185.2 minutes. In the test group, 0 of 10 (0%) patients had drainage line impediments from airlocks (P < .01), and hence, there were no periods of false oliguria. Airlocks and associated periods of false oliguria occur with standard commercial drainage tubing and are eliminated using an automated airlock clearing drainage tube. Electronic urinary output monitoring with self-clearing drainage has the potential to improve tracking of real-time urine output and decrease caregiver workload.

Effect of hemorrhage rate on early hemodynamic responses in conscious sheep.

Physiological compensatory mechanisms can mask the extent of hemorrhage in conscious mammals, which can be further complicated by individual tolerance and variations in hemorrhage onset and duration. We assessed the effect of hemorrhage rate on tolerance and early physiologic responses to hemorrhage in conscious sheep. Eight Merino ewes (37.4 ± 1.1 kg) were subjected to fast (1.25 mL/kg/min) and slow (0.25 mL/kg/min) hemorrhages separated by at least 3 days. Blood was withdrawn until a drop in mean arterial pressure (MAP) of >30 mmHg and returned at the end of the experiment. Continuous monitoring includedMAP, central venous pressure, pulmonary artery pressure, pulse oximetry, and tissue oximetry. Cardiac output by thermodilution and arterial blood samples were also measured. The effects of fast versus slow hemorrhage rates were compared for total volume of blood removed and stoppage time (whenMAP < 30 mmHg of baseline) and physiological responses during and after the hemorrhage. Estimated blood volume removed whenMAPdropped 30 mmHg was 27.0 ± 4.2% (mean ± standard error) in the slow and 27.3 ± 3.2% in the fast hemorrhage (P = 0.47, pairedttest between rates). Pressure and tissue oximetry responses were similar between hemorrhage rates. Heart rate increased at earlier levels of blood loss during the fast hemorrhage, but hemorrhage rate was not a significant factor for individual hemorrhage tolerance or hemodynamic responses. In 5/16 hemorrhages MAP stopping criteria was reached with <25% of blood volume removed. This study presents the physiological responses leading up to a significant drop in blood pressure in a large conscious animal model and how they are altered by the rate of hemorrhage.

Pairing tone trains with vagus nerve stimulation induces temporal plasticity in auditory cortex.

The selectivity of neurons in sensory cortex can be modified by pairing neuromodulator release with sensory stimulation. Repeated pairing of electrical stimulation of the cholinergic nucleus basalis, for example, induces input specific plasticity in primary auditory cortex (A1). Pairing nucleus basalis stimulation (NBS) with a tone increases the number of A1 neurons that respond to the paired tone frequency. Pairing NBS with fast or slow tone trains can respectively increase or decrease the ability of A1 neurons to respond to rapidly presented tones. Pairing vagus nerve stimulation (VNS) with a single tone alters spectral tuning in the same way as NBS-tone pairing without the need for brain surgery. In this study, we tested whether pairing VNS with tone trains can change the temporal response properties of A1 neurons. In naïve rats, A1 neurons respond strongly to tones repeated at rates up to 10 pulses per second (pps). Repeatedly pairing VNS with 15 pps tone trains increased the temporal following capacity of A1 neurons and repeatedly pairing VNS with 5 pps tone trains decreased the temporal following capacity of A1 neurons. Pairing VNS with tone trains did not alter the frequency selectivity or tonotopic organization of auditory cortex neurons. Since VNS is well tolerated by patients, VNS-tone train pairing represents a viable method to direct temporal plasticity in a variety of human conditions associated with temporal processing deficits.

Cortical activity patterns predict robust speech discrimination ability in noise.

The neural mechanisms that support speech discrimination in noisy conditions are poorly understood. In quiet conditions, spike timing information appears to be used in the discrimination of speech sounds. In this study, we evaluated the hypothesis that spike timing is also used to distinguish between speech sounds in noisy conditions that significantly degrade neural responses to speech sounds. We tested speech sound discrimination in rats and recorded primary auditory cortex (A1) responses to speech sounds in background noise of different intensities and spectral compositions. Our behavioral results indicate that rats, like humans, are able to accurately discriminate consonant sounds even in the presence of background noise that is as loud as the speech signal. Our neural recordings confirm that speech sounds evoke degraded but detectable responses in noise. Finally, we developed a novel neural classifier that mimics behavioral discrimination. The classifier discriminates between speech sounds by comparing the A1 spatiotemporal activity patterns evoked on single trials with the average spatiotemporal patterns evoked by known sounds. Unlike classifiers in most previous studies, this classifier is not provided with the stimulus onset time. Neural activity analyzed with the use of relative spike timing was well correlated with behavioral speech discrimination in quiet and in noise. Spike timing information integrated over longer intervals was required to accurately predict rat behavioral speech discrimination in noisy conditions. The similarity of neural and behavioral discrimination of speech in noise suggests that humans and rats may employ similar brain mechanisms to solve this problem.