Thermal acclimation in a non-migratory songbird occurs via changes to thermogenic capacity, but not conductance.

Thermoregulatory performance can be modified through changes in various subordinate traits, but the rate and magnitude of change in these traits is poorly understood. We investigated flexibility in traits that affect thermal balance between black-capped chickadees (Poecile atricapillus) acclimated for 6 weeks to cold (-5°C) or control (23°C) environments (n=7 per treatment). We made repeated measurements of basal and summit metabolic rates via flow-through respirometry and of body composition using quantitative magnetic resonance of live birds. At the end of the acclimation period, we measured thermal conductance of the combined feathers and skins. Cold-acclimated birds had a higher summit metabolic rate, reflecting a greater capacity for endogenous heat generation, and an increased lean mass. However, birds did not alter their thermal conductance. These results suggest that chickadees respond to cold stress by increasing their capacity for heat production rather than increasing heat retention, an energetically expensive strategy.

Impact of in-Station Medication Automated Dispensing Systems on Prehospital Pain Medication Administration.

INTRODUCTION: Medication automatic dispensing systems (ADS) have been implemented in many settings, including fire-based EMS stations. The aim of this study was to evaluate the impact of in-station ADSs on controlled substance administration rates and EMS response intervals. METHODS: This study was a retrospective review of data from a single fire-based EMS agency. Medication administration rates and EMS response intervals were compared before ADS implementation (P1; 6/1/15 to 5/31/16) and after ADS implementation (P3; 6/1/17-5/31/19). Cases with missing data and during a one-year implementation period were excluded. RESULTS: 4045 cases were identified in P1 and 8168 in P3. The odds of morphine or versed administration increased following ADS implementation: OR = 1.77 (95% CI: 1.53, 2.03) and OR = 1.53 (95%CI: 1.18, 2.00) respectively. There were statistically, but likely not operationally significant increases in median response interval and transport interval from P1 to P3 of 14 seconds, (p < 0.001) and 39 seconds (p < 0.001) respectively. Time at hospital for all calls decreased by more than 11 minutes for all transports, from a median of 34 minutes (IQR; 23.7, 45.5) to 22.7 minutes (IQR:18.5, 27.6) in P3, p < 0.001 and by 27.9 minutes for calls in which a controlled substance was given: P1 = 50.6 minutes (IQR: 34.6, 63.2), P3 = 22.7 minutes (IQR: 18.3, 27.4), p < 0.001. CONCLUSION: In this system, medication ADS implementation was associated with an increase in the rates of controlled substance administration and a decrease in the time units were at hospitals.

Correlation between prehospital and in-hospital hypotension and outcomes after traumatic brain injury.

BACKGROUND AND OBJECTIVE: Hypotension has a powerful effect on patient outcome after traumatic brain injury (TBI). The relative impact of hypotension occurring in the field versus during early hospital resuscitation is unknown. We evaluated the association between hypotension and mortality and non-mortality outcomes in four cohorts defined by where the hypotension occurred [neither prehospital nor hospital, prehospital only, hospital only, both prehospital and hospital]. METHODS: Subjects ≥10 years with major TBI were included. Standard statistics were used for unadjusted analyses. We used logistic regression, controlling for significant confounders, to determine the adjusted odds (aOR) for outcomes in each of the three cohorts. RESULTS: Included were 12,582 subjects (69.8% male; median age 44 (IQR 26-61). Mortality by hypotension status: No hypotension: 9.2% (95%CI: 8.7-9.8%); EMS hypotension only: 27.8% (24.6-31.2%); hospital hypotension only: 45.6% (39.1-52.1%); combined EMS/hospital hypotension 57.6% (50.0-65.0%); (p < 0.0001). The aOR for death reflected the same progression: 1.0 (reference-no hypotension), 1.8 (1.39-2.33), 2.61 (1.73-3.94), and 4.36 (2.78-6.84), respectively. The proportion of subjects having hospital hypotension was 19.0% (16.5-21.7%) in those with EMS hypotension compared to 2.0% (1.8-2.3%) for those without (p < 0.0001). Additionally, the proportion of patients with TC hypotension was increased even with EMS "near hypotension" up to an SBP of 120 mmHg [(aOR 3.78 (2.97, 4.82)]. CONCLUSION: While patients with hypotension in the field or on arrival at the trauma center had markedly increased risk of death compared to those with no hypotension, those with prehospital hypotension that was not resolved before hospital arrival had, by far, the highest odds of death. Furthermore, TBI patients who had prehospital hypotension were five times more likely to arrive hypotensive at the trauma center than those who did not. Finally, even "near-hypotension" in the field was strongly and independently associated the risk of a hypotensive hospital arrival (<90 mmHg). These findings are supportive of the prehospital guidelines that recommend aggressive prevention and treatment of hypotension in major TBI.

Optimal Out-of-Hospital Blood Pressure in Major Traumatic Brain Injury: A Challenge to the Current Understanding of Hypotension.

STUDY OBJECTIVE: Little is known about the out-of-hospital blood pressure ranges associated with optimal outcomes in traumatic brain injuries (TBI). Our objective was to evaluate the associations between out-of-hospital systolic blood pressure (SBP) and multiple hospital outcomes without assuming any predefined thresholds for hypotension, normotension, or hypertension. METHODS: This was a preplanned secondary analysis from the Excellence in Prehospital Injury Care (EPIC) TBI study. Among patients (age ≥10 years) with major TBIs (Barell Matrix type 1 and/or Abbreviated Injury Scale-head severity ≥3) and lowest out-of-hospital SBPs of 40 to 299 mmHg, we utilized generalized additive models to summarize the distributions of various outcomes as smoothed functions of SBP, adjusting for important and significant confounders. The subjects who were enrolled in the study phase after the out-of-hospital TBI guideline implementation were used to validate the models developed from the preimplementation cohort. RESULTS: Among 12,169 included cases, the mortality model revealed 3 distinct ranges: (1) a monotonically decreasing relationship between SBP and the adjusted probability of death from 40 to 130 mmHg, (2) lowest adjusted mortality from 130 to 180 mmHg, and (3) rapidly increasing mortality above 180 mmHg. A subanalysis of the cohorts with isolated TBIs and multisystem injuries with TBIs revealed SBP mortality patterns that were similar to each other and to that of the main analysis. While the specific SBP ranges varied somewhat for the nonmortality outcomes (hospital length of stay, ICU length of stay, discharge to skilled nursing/inpatient rehabilitation, and hospital charges), the patterns were very similar to that of mortality. In each model, validation was confirmed utilizing the postimplementation cohort. CONCLUSION: Optimal adjusted mortality was associated with a surprisingly high SBP range (130 to 180 mmHg). Below this level, there was no point or range of inflection that would indicate a physiologically meaningful threshold for defining hypotension. Nonmortality outcomes showed very similar patterns. These findings highlight how sensitive the injured brain is to compromised perfusion at SBP levels that, heretofore, have been considered adequate or even normal. While the study design does did not allow us to conclude that the currently recommended treatment threshold (<90 mmHg) should be increased, the findings imply that the definition of hypotension in the setting of TBI is too low. Randomized trials evaluating treatment levels significantly higher than 90 mmHg are needed.

Effect of Implementing the Out-of-Hospital Traumatic Brain Injury Treatment Guidelines: The Excellence in Prehospital Injury Care for Children Study (EPIC4Kids).

STUDY OBJECTIVE: We evaluate the effect of implementing the out-of-hospital pediatric traumatic brain injury guidelines on outcomes in children with major traumatic brain injury. METHODS: The Excellence in Prehospital Injury Care for Children study is the preplanned secondary analysis of the Excellence in Prehospital Injury Care study, a multisystem, intention-to-treat study using a before-after controlled design. This subanalysis included children younger than 18 years who were transported to Level I trauma centers by participating out-of-hospital agencies between January 1, 2007, and June 30, 2015, throughout Arizona. The primary and secondary outcomes were survival to hospital discharge or admission for children with major traumatic brain injury and in 3 subgroups, defined a priori as those with moderate, severe, and critical traumatic brain injury. Outcomes in the preimplementation and postimplementation cohorts were compared with logistic regression, adjusting for risk factors and confounders. RESULTS: There were 2,801 subjects, 2,041 in preimplementation and 760 in postimplementation. The primary analysis (postimplementation versus preimplementation) yielded an adjusted odds ratio of 1.16 (95% confidence interval 0.70 to 1.92) for survival to hospital discharge and 2.41 (95% confidence interval 1.17 to 5.21) for survival to hospital admission. In the severe traumatic brain injury cohort (Regional Severity Score-Head 3 or 4), but not the moderate or critical subgroups, survival to discharge significantly improved after guideline implementation (adjusted odds ratio = 8.42; 95% confidence interval 1.01 to 100+). The improvement in survival to discharge among patients with severe traumatic brain injury who received positive-pressure ventilation did not reach significance (adjusted odds ratio = 9.13; 95% confidence interval 0.79 to 100+). CONCLUSION: Implementation of the pediatric out-of-hospital traumatic brain injury guidelines was not associated with improved survival when the entire spectrum of severity was analyzed as a whole (moderate, severe, and critical). However, both adjusted survival to hospital admission and discharge improved in children with severe traumatic brain injury, indicating a potential severity-based interventional opportunity for guideline effectiveness. These findings support the widespread implementation of the out-of-hospital pediatric traumatic brain injury guidelines.

Can Emergency Medical Services Utilization Rates Be Used to Measure the Success of An Alcohol Amnesty Policy?

INTRODUCTION: Medical Amnesty/Good Samaritan (MAGS) policies, which eliminate legal charges when students call 9-1-1 for excessive drinking, have been implemented with the goal of reducing barriers to accessing Emergency Medical Services (EMS). This study investigated the impact of MAGS policy implementation on EMS calls on campus and if that EMS call volume could be used to measure policy success. The aim of this study was to compare the prevalence of alcohol-related EMS calls before and after MAGS implementation at a single large public university campus. Methods: A retrospective review of all 9-1-1 calls to on-campus locations was conducted using patient care records (PCRs) from a collegiate EMS agency responding exclusively to on-campus 9-1-1 calls. Calls were excluded if the PCR was marked "incomplete", were outside the 2015 CBEMS response zone boundaries, or if patient age was <15 or >25 years old to ensure analysis was targeting the on-campus student population. The incidence of alcohol-related 9-1-1 calls was compared between one academic year (AY) prior to (pre-MAGS, AY2015) and two years after MAGS implementation (post-MAGS, AY2016/17). An alcohol-related 9-1-1 call was defined as an EMS provider primary or secondary impression of "Alcohol, Alcohol Intoxication, or Alcohol Ingestion" or a call in which the patient explicitly admitted to alcohol use. Relative risk (RR) with 95% confidence intervals (CI) were used to describe the results. Results: Over the three-year study period, the collegiate EMS agency responded to 2440 calls of which 1283 met inclusion criteria. 58 calls were excluded for being incomplete, 227 were outside the original boundaries and 872 were outside the defined age range. Of those calls, 351 were pre-MAGS and 932 were post-MAGS. Of the total 9-1-1 calls, 127 (36.2%) were related to alcohol pre-MAGS and 327 (35.1%) were related to alcohol post-MAGS policy implementation. The relative risk of a 9-1-1 call being made for alcohol-related issues after MAGS implementation was RR = 0.97 (95% CI 0.83-1.14; P = 0.713). Conclusion: Implementation of a MAGS policy was not associated with a significant change in the number of alcohol-related EMS responses. It is unclear if these results reflect ineffective policy implementation or a general reduction in on-campus alcohol consumption. However, using EMS call volume as a marker for policy success and quality improvement offers an innovative tool through which EMS agencies can provide valuable feedback to other system stakeholders.

Refusals After Prehospital Administration of Naloxone during the COVID-19 Pandemic.

OBJECTIVE: To determine if COVID-19 was associated with a change in patient refusals after Emergency Medical Services (EMS) administration of naloxone. METHODS: This is a retrospective cohort study in which the incidence of refusals after naloxone administration in a single EMS system was evaluated. The number of refusals after naloxone administration was compared across the before-pandemic interval (01/01/20 to 02/15/20) and the during-pandemic interval (03/16/20 to 04/30/20). For comparison the incidence of all other patient refusals before and during COVID-19 as well as the incidences of naloxone administration before and during COVID-19 were also reported. RESULTS: Prior to the widespread knowledge of the COVID-19 pandemic, 24 of 164 (14.6%) patients who received naloxone via EMS refused transport. During the pandemic, 55 of 153 (35.9%) patients who received naloxone via EMS refused transport. Subjects receiving naloxone during the COVID-19 pandemic were at greater risk of refusal of transport than those receiving naloxone prior to the pandemic (RR = 2.45; 95% CI 1.6-3.76). Among those who did not receive naloxone, 2067 of 6956 (29.7%) patients were not transported prior to the COVID-19 pandemic and 2483 of 6016 (41.3%) were not transported during the pandemic. Subjects who did not receive naloxone with EMS were at greater risk of refusal of transport during the COVID-19 pandemic than prior to it (RR = 1.39; 95% CI 1.32-1.46). CONCLUSION: In this single EMS system, more than a two-fold increase in the rate of refusal after non-fatal opioid overdose was observed following the COVID-19 outbreak.

Prehospital Protocols Reducing Long Spinal Board Use Are Not Associated with a Change in Incidence of Spinal Cord Injury.

Introduction: Many emergency medical services (EMS) agencies have de-emphasized or eliminated the use of long spinal boards (LSB) for patients with possible spinal injury. We sought to determine if implementation of spinal motion restriction (SMR) protocols, which reduce LSB use, was associated with an increase in spinal cord injury (SCI). Methods: This retrospective observational study includes EMS encounters from January 1, 2013 to December 31, 2015 submitted by SMR-adopting ground-based agencies to a state EMS database with hospital discharge data. Encounters were excluded if SMR implementation date was unknown, occurred during a 3-month run-in period, or were duplicates. Study samples include patients with traumatic injury (TI), possible spinal trauma (P-ST), and verified spinal trauma (V-ST) using hospital discharge ICD-9/10 diagnosis codes. The incidence of SCI before and after implementation of SMR was compared using Chi-squared and logistic regression. Results: From 1,005,978 linked encounters, 104,315 unique encounters with traumatic injury and known SMR implementation date were identified with 51,199 cases of P-ST and 5,178 V-ST cases. The incidence of SCI in the pre-SMR and post-SMR interval for each group was: TI, 0.20% vs. 0.22% (p = 0.390); P-ST, 0.40% vs. 0.45% (p = 0.436); and V-ST, 4.04% vs. 4.37% (p = 0.561). Age and injury severity adjusted odds ratio of SCI in the highest risk cohort of patients with V-ST was 1.097 after SMR implementation (95% CI 0.818-1.472). Conclusion: In this limited study, no change in the incidence of SCI was identified following implementation of SMR protocols. Prospective evaluation of this question is necessary to evaluate the safety of SMR protocols.

Maladaptive learning and memory in hybrids as a reproductive isolating barrier.

Selection against hybrid offspring, or postzygotic reproductive isolation, maintains species boundaries in the face of gene flow from hybridization. In this review, we propose that maladaptive learning and memory in hybrids is an important, but overlooked form of postzygotic reproductive isolation. Although a role for learning in premating isolation has been supported, whether learning deficiencies can contribute to postzygotic isolation has rarely been tested. We argue that the novel genetic combinations created by hybridization have the potential to impact learning and memory abilities through multiple possible mechanisms, and that any displacement from optima in these traits is likely to have fitness consequences. We review evidence supporting the potential for hybridization to affect learning and memory, and evidence of links between learning abilities and fitness. Finally, we suggest several avenues for future research. Given the importance of learning for fitness, especially in novel and unpredictable environments, maladaptive learning and memory in hybrids may be an increasingly important source of postzygotic reproductive isolation.

Genetic variation during range expansion: effects of habitat novelty and hybridization.

How species' ranges evolve remains an enduring problem in ecology and evolutionary biology. Species' range limits are potentially set by the inability of peripheral populations to adapt to range-edge habitat. Indeed, peripheral populations are often assumed to have reduced genetic diversity and population sizes, which limit evolvability. However, support for this assumption is mixed, possibly because the genetic effects of range expansion depend on two factors: the extent that habitat into which expansion occurs is novel and sources of gene flow. Here, we used spadefoot toads, Spea bombifrons, to contrast the population genetic effects of expansion into novel versus non-novel habitat. We further evaluated gene flow from conspecifics and from heterospecifics via hybridization with a resident species. We found that range expansion into novel habitat, relative to non-novel habitat, resulted in higher genetic differentiation, lower conspecific gene flow and bottlenecks. Moreover, we found that hybridizing with a resident species introduced genetic diversity in the novel habitat. Our results suggest the evolution of species' ranges can depend on the extent of differences in habitat between ancestral and newly occupied ranges. Furthermore, our results highlight the potential for hybridization with a resident species to enhance genetic diversity during expansions into novel habitat.

Association of Out-of-Hospital Hypotension Depth and Duration With Traumatic Brain Injury Mortality.

STUDY OBJECTIVE: Out-of-hospital hypotension has been associated with increased mortality in traumatic brain injury. The association of traumatic brain injury mortality with the depth or duration of out-of-hospital hypotension is unknown. We evaluated the relationship between the depth and duration of out-of-hospital hypotension and mortality in major traumatic brain injury. METHODS: We evaluated adults and older children with moderate or severe traumatic brain injury in the preimplementation cohort of Arizona's statewide Excellence in Prehospital Injury Care study. We used logistic regression to determine the association between the depth-duration dose of hypotension (depth of systolic blood pressure <90 mm Hg integrated over duration [minutes] of hypotension) and odds of inhospital death, controlling for significant confounders. RESULTS: There were 7,521 traumatic brain injury cases included (70.6% male patients; median age 40 years [interquartile range 24 to 58]). Mortality was 7.8% (95% confidence interval [CI] 7.2% to 8.5%) among the 6,982 patients without hypotension (systolic blood pressure ≥90 mm Hg) and 33.4% (95% CI 29.4% to 37.6%) among the 539 hypotensive patients (systolic blood pressure <90 mm Hg). Mortality was higher with increased hypotension dose: 0.01 to 14.99 mm Hg-minutes 16.3%; 15 to 49.99 mm Hg-minutes 28.1%; 50 to 141.99 mm Hg-minutes 38.8%; and greater than or equal to 142 mm Hg-minutes 50.4%. Log2 (the logarithm in base 2) of hypotension dose was associated with traumatic brain injury mortality (adjusted odds ratio 1.19 [95% CI 1.14 to 1.25] per 2-fold increase of dose). CONCLUSION: In this study, the depth and duration of out-of-hospital hypotension were associated with increased traumatic brain injury mortality. Assessments linking out-of-hospital blood pressure with traumatic brain injury outcomes should consider both depth and duration of hypotension.

Body Temperature after EMS Transport: Association with Traumatic Brain Injury Outcomes.

INTRODUCTION: Low body temperatures following prehospital transport are associated with poor outcomes in patients with traumatic brain injury (TBI). However, a minimal amount is known about potential associations across a range of temperatures obtained immediately after prehospital transport. Furthermore, a minimal amount is known about the influence of body temperature on non-mortality outcomes. The purpose of this study was to assess the correlation between temperatures obtained immediately following prehospital transport and TBI outcomes across the entire range of temperatures. METHODS: This retrospective observational study included all moderate/severe TBI cases (CDC Barell Matrix Type 1) in the pre-implementation cohort of the Excellence in Prehospital Injury Care (EPIC) TBI Study (NIH/NINDS: 1R01NS071049). Cases were compared across four cohorts of initial trauma center temperature (ITCT): <35.0°C [Very Low Temperature (VLT)]; 35.0-35.9°C [Low Temperature (LT)]; 36.0-37.9°C [Normal Temperature (NT)]; and ≥38.0°C [Elevated Temperature (ET)]. Multivariable analysis was performed adjusting for injury severity score, age, sex, race, ethnicity, blunt/penetrating trauma, and payment source. Adjusted odds ratios (aORs) with 95% confidence intervals (CI) for mortality were calculated. To evaluate non-mortality outcomes, deaths were excluded and the adjusted median increase in hospital length of stay (LOS), ICU LOS and total hospital charges were calculated for each ITCT group and compared to the NT group. RESULTS: 22,925 cases were identified and cases with interfacility transfer (7361, 32%), no EMS transport (1213, 5%), missing ITCT (2083, 9%), or missing demographic data (391, 2%) were excluded. Within this study cohort the aORs for death (compared to the NT group) were 2.41 (CI: 1.83-3.17) for VLT, 1.62 (CI: 1.37-1.93) for LT, and 1.86 (CI: 1.52-3.00) for ET. Similarly, trauma center (TC) LOS, ICU LOS, and total TC charges increased in all temperature groups when compared to NT. CONCLUSION: In this large, statewide study of major TBI, both ETs and LTs immediately following prehospital transport were independently associated with higher mortality and with increased TC LOS, ICU LOS, and total TC charges. Further study is needed to identify the causes of abnormal body temperature during the prehospital interval and if in-field measures to prevent temperature variations might improve outcomes.

The Impact of a Pediatric Emergency Department Facility Verification System on Pediatric Mortality Rates in Arizona.

BACKGROUND: The Emergency Medical Services for Children State Partnership Program, as well as the Institute of Medicine report on pediatric emergency care, encourages recognition of emergency departments (EDs) through categorization and verification systems. Although pediatric verification programs are associated with greater pediatric readiness, clinical outcome data have been lacking to track the effects and patient-centered outcomes by implementing such programs. OBJECTIVE: To describe pediatric mortality rates prior to and after implementation of a pediatric emergency facility verification system in Arizona. METHODS: This was a cross-sectional study conducted using data from ED visits between 2011 and 2014 recorded in the Arizona Hospital Discharge Database. The primary outcome measure was the mortality rate for ED visits by patients under 18 years old. Rates were compared prior to and after facility certification by the Arizona Pediatric Prepared Emergency Care program. RESULTS: The total number of ED visits by children during the study period was 1,928,409. Of these, 1,127,294 were at facilities undergoing certification. For hospitals becoming certified, overall ED mortality rates were 35.2 deaths/100,000 ED visits (95% confidence interval [CI] 29.5-41.7) in the precertification analysis and 34.4 deaths/100,000 ED visits (95% CI 30.4-38.9) in the postcertification analysis. The injury-related ED visit mortality rate for certified hospitals showed a decrease from 40.0 injury-related deaths/100,000 ED visits (95% CI 28.6-54.4) in the precertification analysis to 25.8 injury-related deaths/100,000 ED visits (95% CI 18.7-34.8) in the postcertification analysis. CONCLUSION: The implementation of the Arizona pediatric ED verification system was associated with a trend toward lower mortality. These results offer a platform for further research on pediatric ED preparedness efforts and their effects on improved patient outcomes.

Respiration-related discharge of hyoglossus muscle motor units in the rat.

Although respiratory muscle motor units have been studied during natural breathing, simultaneous measures of muscle force have never been obtained. Tongue retractor muscles, such as the hyoglossus (HG), play an important role in swallowing, licking, chewing, breathing, and, in humans, speech. The HG is phasically recruited during the inspiratory phase of the respiratory cycle. Moreover, in urethane anesthetized rats the drive to the HG waxes and wanes spontaneously, providing a unique opportunity to study motor unit firing patterns as the muscle is driven naturally by the central pattern generator for breathing. We recorded tongue retraction force, the whole HG muscle EMG and the activity of 38 HG motor units in spontaneously breathing anesthetized rats under low-force and high-force conditions. Activity in all cases was confined to the inspiratory phase of the respiratory cycle. Changes in the EMG were correlated significantly with corresponding changes in force, with the change in EMG able to predict 53-68% of the force variation. Mean and peak motor unit firing rates were greater under high-force conditions, although the magnitude of discharge rate modulation varied widely across the population. Changes in mean and peak firing rates were significantly correlated with the corresponding changes in force, but the correlations were weak (r(2) = 0.27 and 0.25, respectively). These data indicate that, during spontaneous breathing, recruitment of HG motor units plays a critical role in the control of muscle force, with firing rate modulation playing an important but lesser role.

Reinforcement generates reproductive isolation between neighbouring conspecific populations of spadefoot toads.

Reproductive character displacement is the adaptive evolution of traits that minimize deleterious reproductive interactions between species. When arising from selection to avoid hybridization, this process is referred to as reinforcement. Reproductive character displacement generates divergence not only between interacting species, but also between conspecific populations that are sympatric with heterospecifics versus those that are allopatric. Consequently, such conspecific populations can become reproductively isolated. We compared female mate preferences in, and evaluated gene flow between, neighbouring populations of spadefoot toads that did and did not occur with heterospecifics (mixed- and pure-species populations, respectively). We found that in mixed-species populations females significantly preferred conspecifics. Such females also tended to prefer a conspecific call character that was dissimilar from heterospecifics. By contrast, females from pure-species populations did not discriminate conspecific from heterospecific calls. They also preferred a more exaggerated conspecific call character that resembles heterospecific males. Moreover, gene flow was significantly reduced between mixed- and pure-species population types. Thus, character displacement (and, more specifically, reinforcement) may initiate reproductive isolation between conspecific populations that differ in interactions with heterospecifics.

EMS Treatment Guidelines in Major Traumatic Brain Injury With Positive Pressure Ventilation.

Importance: The Excellence in Prehospital Injury Care (EPIC) study demonstrated improved survival in patients with severe traumatic brain injury (TBI) following implementation of the prehospital treatment guidelines. The impact of implementing these guidelines in the subgroup of patients who received positive pressure ventilation (PPV) is unknown. Objective: To evaluate the association of implementation of prehospital TBI evidence-based guidelines with survival among patients with prehospital PPV. Design, Setting, and Participants: The EPIC study was a multisystem, intention-to-treat study using a before/after controlled design. Evidence-based guidelines were implemented by emergency medical service agencies across Arizona. This subanalysis was planned a priori and included participants who received prehospital PPV. Outcomes were compared between the preimplementation and postimplementation cohorts using logistic regression, stratified by predetermined TBI severity categories (moderate, severe, or critical). Data were collected from January 2007 to June 2017, and data were analyzed from January to February 2023. Exposure: Implementation of the evidence-based guidelines for the prehospital care of patient with TBI. Main Outcomes and Measures: The primary outcome was survival to hospital discharge, and the secondary outcome was survival to admission. Results: Among the 21 852 participants in the main study, 5022 received prehospital PPV (preimplementation, 3531 participants; postimplementation, 1491 participants). Of 5022 included participants, 3720 (74.1%) were male, and the median (IQR) age was 36 (22-54) years. Across all severities combined, survival to admission improved (adjusted odds ratio [aOR], 1.59; 95% CI, 1.28-1.97), while survival to discharge did not (aOR, 0.94; 95% CI, 0.78-1.13). Within the cohort with severe TBI but not in the moderate or critical subgroups, survival to hospital admission increased (aOR, 6.44; 95% CI, 2.39-22.00), as did survival to discharge (aOR, 3.52; 95% CI, 1.96-6.34). Conclusions and Relevance: Among patients with severe TBI who received active airway interventions in the field, guideline implementation was independently associated with improved survival to hospital admission and discharge. This was true whether they received basic airway interventions or advanced airways. These findings support the current guideline recommendations for aggressive prevention/correction of hypoxia and hyperventilation in patients with severe TBI, regardless of which airway type is used.

Optimizing the trade-off between offspring number and quality in unpredictable environments: testing the role of differential androgen transfer to collared flycatcher eggs.

According to the brood reduction hypothesis, parents adjust their brood size in response to current environmental conditions. When resources are abundant, parents can successfully raise all hatched offspring, but when resources are scarce, brood reduction, i.e., the sacrifice of some siblings to secure the quality of a subset of offspring, may maximize fitness. Differential transfer of maternal androgens is one potential proximate mechanism through which female birds may facilitate brood reduction because it may alter the relative competitive ability of sibling nestlings. We tested the hypothesis that female collared flycatchers (Ficedula albicollis) manipulate sibling competition by transferring less androgens to eggs late in the laying sequence. We experimentally elevated androgen levels in i) whole clutches and ii) only the two last laid eggs, and compared growth and begging behavior of offspring from these treatments with a control treatment. By using three treatments and video assessment of begging, we examined the effects of within-clutch patterns of yolk androgen transfer on levels of sibling competition in situ. When androgens were elevated in only the two last laid eggs, begging was more even among siblings compared to control nests. We also found that female nestlings receiving additional yolk androgens showed higher mass gain later in the breeding season, while their male counterparts did not. Our results suggest that females may improve reproductive success in unpredictable environments by altering within-clutch patterns of yolk androgen transfer. We discuss the possibility that life-history divergence between the co-occurring collared and pied flycatcher (Ficedula hypoleuca) is amplified by patterns of yolk androgen transfer.

Low fertility of wild hybrid male flycatchers despite recent divergence.

Postzygotic isolation may be important for maintaining species boundaries, particularly when premating barriers are incomplete. Little is known about the course of events leading from minor environmental mismatches affecting hybrid fitness to severe genetic incompatibilities causing sterility or inviability. We investigated whether reduced reproductive success of hybrid males was caused by suboptimal sperm traits or by more severe genetic incompatibilities in a hybrid zone of pied (Ficedula hypoleuca) and collared flycatchers (F. albicollis) on the island of Öland, Sweden. About 4 per cent hybridization is observed in this population and all female hybrids are sterile. We found no sperm in the ejaculates of most sampled hybrid males, and sperm with abnormal morphology in two hybrids. Furthermore, none of the hybrids sired any offspring because of high levels of hatching failure and extra-pair paternity in their nests. These results from a natural hybrid zone suggest that the spermatogenesis of hybrid males may become disrupted despite little genetic divergence between the parental species.

A guide to the genomics of ecological speciation in natural animal populations.

Interest in ecological speciation is growing, as evidence accumulates showing that natural selection can lead to rapid divergence between subpopulations. However, whether and how ecological divergence can lead to the buildup of reproductive isolation remains under debate. What is the relative importance of natural selection vs. neutral processes? How does adaptation generate reproductive isolation? Can ecological speciation occur despite homogenizing gene flow? These questions can be addressed using genomic approaches, and with the rapid development of genomic technology, will become more answerable in studies of wild populations than ever before. In this article, we identify open questions in ecological speciation theory and suggest useful genomic methods for addressing these questions in natural animal populations. We aim to provide a practical guide for ecologists interested in incorporating genomic methods into their research programs. An increased integration between ecological research and genomics has the potential to shed novel light on the origin of species.

Synchronization of presynaptic input to motor units of tongue, inspiratory intercostal, and diaphragm muscles.

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1-8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10-20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.