Concussion Symptoms and Neurocognitive Performance of Children and Adolescents on Antidepressants

INTRODUCTION/PURPOSE

There is a well-established association between preexisting depression/anxiety and greater postconcussion symptom burden, but the potential impact of antidepressant medications has not been fully explored. The primary objective of this study was to compare preinjury/baseline and postinjury concussion symptom scores and neurocognitive performance of athletes on antidepressant medications, both with healthy controls and with those with depression/anxiety not on antidepressants.

METHODS

This is a cross-sectional study using data collected from 49,270 junior and high school athletes from computerized neurocognitive assessments (Immediate Post-Concussion Assessment and Cognitive Test [ImPACT]) administered between 2009 and 2018 held by the Massachusetts Concussion Management Coalition. The main outcome measures were symptom scores and neurocognitive performance measures, all of which were assessed both at baseline and postinjury. Statistical analysis included analysis of variance and Tukey pairwise comparisons for continuous variables and Fisher's exact test for categorical variables. Multivariate regression models were used to adjust for potential confounding variables.

RESULTS

Both at baseline and postinjury, athletes with depression/anxiety had mean total symptom scores that were more than double that of healthy controls regardless of antidepressant use. Although there were no significant differences in neurocognitive performance at baseline, depression/anxiety was associated with small but significant decreases in postinjury visual memory and visual motor scores.

CONCLUSIONS

Both at baseline and after sustaining a concussion, young athletes with depression/anxiety experience significantly greater symptom burden compared with healthy controls regardless of antidepressant use.

Factors Associated with Symptom Resolution after Aerobic Exercise Intervention in Adolescent and Young Adults with Concussion

BACKGROUND

Aerobic exercise facilitates postconcussion symptom resolution at the group level, but patient-level characteristics may affect the likelihood of treatment efficacy.

PURPOSE

This study aimed to investigate demographic and clinical characteristics, which differentiate postconcussion aerobic exercise treatment efficacy from nonefficacy in the intervention arm of a randomized clinical trial.

METHODS

Adolescent and young adult participants initiated a standardized aerobic exercise intervention within 14 d of concussion, consisting of self-selected exercise for 100 min·wk -1 at an individualized heart rate (80% of heart rate induced symptom exacerbation during graded exercise testing). Treatment efficacy was defined as symptom resolution within 28-d postconcussion. Treatment efficacy and nonefficacy groups were compared on demographics, clinical characteristics, intervention adherence, and persistent symptom risk using the Predicting Persistent Postconcussive Problems in Pediatrics (5P) clinical risk score.

RESULTS

A total of 27 participants (16.1 ± 2.3 yr old; range, 11-21 yr; 52% female) began the intervention, with a mean of 9.5 ± 3.7 d after concussion; half ( n = 13; 48%) demonstrated treatment efficacy (symptom resolution within 28 d postconcussion). Those whose symptoms resolved within 28 d had significantly lower preintervention postconcussion symptom inventory scores (21.2 ± 13.2 vs 41.4 ± 22.2; P < 0.01), greater adherence to the intervention (77% vs 36%; P = 0.05), and longer average exercise duration (median [interquartile range], 49.7 [36.8-68.6] vs 30.4 [20.7-34.7] min; P < 0.01) than those whose symptoms lasted more than 28 d. Groups were similar in age, sex, timing of intervention, and preintervention 5P risk score.

CONCLUSIONS

A standardized aerobic exercise intervention initiated within 14 d of concussion demonstrated efficacy for approximately half of participants, according to our definition of treatment efficacy. This multisite aerobic exercise intervention suggests that lower symptom severity, higher intervention adherence, and greater exercise duration are factors that increase the likelihood of symptoms resolving within 28 d of concussion.

Abortion Restrictiveness and Infant Mortality: An Ecologic Study, 2014-2018

INTRODUCTION

The U.S. has the highest infant mortality rate among peer countries. Restrictive abortion laws may contribute to poor infant health outcomes. This ecological study investigated the association between county-level infant mortality and state-level abortion access legislation in the U.S. from 2014 to 2018.

METHODS

A multivariable regression analysis with the outcome of county-level infant mortality rates, controlling for the primary exposure of state-level abortion laws, and county-level factors, county-level distance to an abortion facility, and state Medicaid expansion status was performed. Incidence rate ratios and 95% CIs were reported. Analyses were conducted in 2022-2023.

RESULTS

There were 113,397 infant deaths among 19,559,660 live births (infant mortality rate=5.79 deaths/1,000 live births; 95% CI=5.75, 5.82). Black infant mortality rate (10.69/1,000) was more than twice the White infant mortality rate (4.87/1,000). In the multivariable model, increased infant mortality rates were seen in states with ≥8 restrictive laws, with the most restrictive (11-12 laws) having a 16% increased infant mortality level (adjusted incidence rate ratios=1.162; 95% CI=1.103, 1.224). Increased infant mortality rates were associated with increased county-level Black race individuals (adjusted incidence rate ratios=1.031; 95% CI=1.026, 1.037), high school education (adjusted incidence rate ratios=1.018; 95% CI=1.008, 1.029), maternal smoking (adjusted incidence rate ratios=1.025; 95% CI=1.018, 1.033), and inadequate prenatal care (adjusted incidence rate ratios=1.045; 95% CI=1.036, 1.055).

CONCLUSIONS

State-level abortion law restrictiveness is associated with higher county-level infant mortality rates. The Supreme Court decision on Dobbs versus Jackson and changes in state laws limiting abortion may affect future infant mortality.

Optimizing Choice and Timing of Behavioral Outcome Tests After Repetitive Mild Traumatic Brain Injury: A Machine Learning-Based Approach on Multiple Pre-Clinical Experiments

Repetitive mild traumatic brain injury (rmTBI) is a potentially debilitating condition with long-term sequelae. Animal models are used to study rmTBI in a controlled environment, but there is currently no established standard battery of behavioral tests used. Primarily, we aimed to identify the best combination and timing of behavioral tests to distinguish injured from uninjured animals in rmTBI studies, and secondarily, to determine whether combinations of independent experiments have better behavioral outcome prediction accuracy than individual experiments. Data from 1203 mice from 58 rmTBI experiments, some of which have already been published, were used. In total, 11 types of behavioral tests were measured by 37 parameters at 13 time points during the first 6 months after injury. Univariate regression analyses were used to identify optimal combinations of behavioral tests and whether the inclusion of multiple heterogenous experiments improved accuracy. k-means clustering was used to determine whether a combination of multiple tests could distinguish mice with rmTBI from uninjured mice. We found that a combination of behavioral tests outperformed individual tests alone when distinguishing animals with rmTBI from uninjured animals. The best timing for most individual behavioral tests was 3-4 months after first injury. Overall, Morris water maze (MWM; hidden and probe frequency) was the behavioral test with the best capability of detecting injury effects (area under the curve [AUC] = 0.98). Combinations of open field tests and elevated plus mazes also performed well (AUC = 0.92), as did the forced swim test alone (AUC = 0.90). In summary, multiple heterogeneous experiments tended to predict outcome better than individual experiments, and MWM 3-4 months after injury was the optimal test, also several combinations also performed well. In order to design future pre-clinical rmTBI trials, we have included an interactive application available online utilizing the data from the study via the Supplementary URL.

Alternative care sites and resident exposure in pediatric emergency medicine: Who, what, and where

Objectives

Emergency medicine (EM) physicians and pediatricians who provide acute pediatric care depend on clinical exposure during residency to learn pediatric EM. Increasing volumes of pediatric patients, especially with behavioral health complaints, have stressed pediatric emergency departments (ED) and prompted clinical operations innovations including alternative care sites outside the main ED. We investigated the impact of these recent trends and resulting alternative care sites on the exposure of residents to core pediatric conditions.

Methods

This retrospective study reviewed patient encounters between July 1, 2018, and December 31, 2022, at a pediatric ED that hosts one pediatric and three EM residencies. During the study, the hospital employed alternative care sites in response to increased and shifting patient populations. Median patients per resident per academic year were compared before and after the opening of alternative care sites, overall and stratified by patient factors (age, sex, Emergency Severity Index [ESI], and diagnostic category). The study also compared the percentage of residents who saw no patients with a given diagnosis between the two periods.

Results

Of 231,101 patient encounters, 199,947 were seen in the main ED and 31,154 in alternative care sites. The median number of patients seen by a single resident in a single academic year ranged from 82 to 136 for pediatric residents and from 128 to 183 for EM residents. The median number of patients per resident per year did not decrease for any age group, sex, ESI level, or diagnosis across the two periods. Residents saw a median of 19 more patients with psychiatric diagnoses (95% CI 15.4-22.7) in the more recent period. Seven diagnoses were not seen by at least 20% of residents during both periods.

Conclusions

Current pediatric ED capacity challenges can be addressed with alternative care sites without decreasing volume or variety of patients seen by residents.

Adolescents With More Oculomotor and Vestibular Signs of Sport-Related Concussion Benefit from Aerobic Exercise: An Exploratory Analysis

Abstract Early targeted heart rate (HR) aerobic exercise has been shown to reduce the duration of recovery from sport-related concussion (SRC) as well as the incidence of persistent post-concussive symptoms (PPCS). It is not known, however, if more severe oculomotor and vestibular presentations of SRC benefit from a prescription of aerobic exercise. The current study is an exploratory analysis of two published randomized controlled trials that compared aerobic exercise within 10 days of injury with a placebo-like stretching intervention. Combining the two studies yielded a larger sample size to stratify severity of concussion based on the number of abnormal physical examination signs present at the initial office evaluation, which were confirmed with self-reported symptoms and recovery outcomes. The most discriminant cut-off was between those who had ≤3 oculomotor and vestibular signs and those who had >3 signs. Aerobic exercise (hazard ratio = 0.621 [0.412, 0.936], p = 0.023) reduced recovery times even when controlling for site (hazard ratio = 0.461 [0.303, 0.701], p < 0.001), severity (hazard ratio = 0.528 [0.325, 0.858], p = 0.010) and the interaction term of intervention and severity (hazard ratio = 0.972 [0.495, 1.909], p = 0.935). Adolescents who presented with >3 signs and were assigned to the placebo-like stretching group had a PPCS incidence of 38%, which was the highest of all subgroups (aerobic exercise and ≤3 findings: 8%; stretching and ≤3 findings: 11%; aerobic exercise and >3 findings: 21%). This exploratory study provides pilot evidence that prescribed sub-symptom threshold aerobic exercise treatment early after SRC may be effective for adolescents with more oculomotor and vestibular physical examination signs and should be validated in future adequately powered trials.

Early analgesic administration and headache presence 7 days post-concussion in children

OBJECTIVE

This study investigates whether acute treatment with ibuprofen, acetaminophen, or both is associated with resolution of headache or reduction of headache pain at 7 days post-concussion in children and youth.

METHODS

A secondary analysis of the Predicting and Preventing Post-concussive Problems in Pediatrics (5P) prospective cohort study was conducted. Individuals aged 5-18 years with acute concussion presenting to nine Canadian pediatric emergency departments (ED) were enrolled from August 2013 to June 2015. The primary outcome was the presence of headache at 7 days, measured using the Post-Concussion Symptom Inventory. The association between acute administration of ibuprofen, acetaminophen, or both and headache presence at 7 days was investigated with propensity scores and adjusted multivariate regression models.

RESULTS

2277 (74.3%) of 3063 participants had headache upon ED presentation. Of these participants, 1543 (67.8%) received an analgesic medication before or during their ED visit [ibuprofen 754 (33.1%), acetaminophen 445 (19.5%), both 344 (15.1%); or no medication 734 (32.2%)]. Multivariate analysis pertained to 1707 participants with propensity scores based on personal characteristics and symptoms; 877 (51.4%) reported headache at 7 days post-concussion. No association emerged between treatment and presence of headache at 7 days [ibuprofen vs. untreated: (relative risk (RR) = 1.12 (95% CI 0.99,1.26); acetaminophen vs untreated RR = 1.02 (95% CI 0.87,1.22); both vs untreated RR = 1.02 (95% CI 0.86,1.18)].

CONCLUSIONS

Exposure to ibuprofen, acetaminophen, or both in the acute phase does not decrease the risk of headache at 7 days post-concussion. Non-opioid analgesics like ibuprofen or acetaminophen may be prescribed for short-term headache relief but clinicians need to be cautious with long-term medication overuse in those whose headache symptoms persist.

Examining racial and ethnic disparities in adult emergency department patient visits for concussion in the United States

Background

Racial and ethnic differences in emergency department (ED) visits have been reported among adolescent patients but are unsubstantiated among adults. Therefore, our purpose in this study was to examine the relationship between race/ethnicity and adult ED visits for concussions, their injury mechanisms, and computed tomography (CT) scan use among a nationally representative sample.

Methods

We used the National Hospital Ambulatory Medical Care Survey database from 2010-2015 to examine 63,725 adult (20-45 years old) patient visits, representing an estimated 310.6 million visits presented to EDs. Of these visits, 884 (4.5 million national estimate) were diagnosed with a concussion. Visit records detailed patient information (age, sex, race/ethnicity, geographic region, primary payment type), ED visit diagnoses, injury mechanism (sport, motor vehicle, fall, struck by or against, "other"), and head CT scan use. The primary independent variable was race/ethnicity (non-Hispanic Asian, non-Hispanic Black or African American, Hispanic/Latinx, non-Hispanic multiracial or another, and non-Hispanic White). We used multivariable logistic and multinomial regression models with complex survey sampling design weighting to examine the relationship between concussion ED visits, injury mechanisms, and CT scan use separately by race/ethnicity while accounting for covariates.

Results

There were no associations between race/ethnicity and concussion diagnosis among adult ED visits after accounting for covariates. Relative to sports-related injuries, non-Hispanic Black or African American patient visits were associated with a motor vehicle (OR = 2.69, 95% CI: 1.06-6.86) and "other" injury mechanism (OR = 4.58, 95% CI: 1.34-15.69) compared to non-Hispanic White patients. Relative to sports-related injuries, non-Hispanic Asian, multiracial, or patients of another race had decreased odds of falls (OR = 0.20, 95% CI: 0.04-0.91) and "other" injuries (OR = 0.09, 95% CI: 0.01-0.55) compared to non-Hispanic White patients. The odds of a CT scan being performed were significantly lower among Hispanic/Latinx patient visits relative to non-Hispanic White patients (OR = 0.52, 95% CI: 0.30-0.91), while no other race/ethnicity comparisons differed.

Conclusion

Our findings indicate that the overarching concussion ED visit likelihood may not differ by race/ethnicity in adults, but the underlying mechanism causing the concussion and receiving a CT scan demonstrates considerable differences. Prospective future research is warranted to comprehensively understand and intervene in the complex, multi-level race/ethnicity relationships related to concussion health care to ensure equitable patient treatment.

Association of Clinical Guidelines and Decision Support with Computed Tomography Use in Pediatric Mild Traumatic Brain Injury

OBJECTIVE

To examine whether the presence of clinical guidelines and clinical decision support (CDS) for mild traumatic brain injury (mTBI) are associated with lower use of head computed tomography (CT).

STUDY DESIGN

We conducted a cross-sectional study of 45 pediatric emergency departments (EDs) in the Pediatric Hospital Information System from 2015 through 2019. We included children discharged with mTBI and surveyed ED clinical directors to ascertain the presence and implementation year of clinical guidelines and CDS. The association of clinical guidelines and CDS with CT use was assessed, adjusting for relevant confounders. As secondary outcomes, we evaluated ED length of stay and rates of 3-day ED revisits and admissions after revisits.

RESULTS

There were 216 789 children discharged with mTBI, and CT was performed during 20.3% (44 114/216 789) of ED visits. Adjusted hospital-specific CT rates ranged from 11.8% to 34.7% (median 20.5%, IQR 17.3%, 24.3%). Of the 45 EDs, 17 (37.8%) had a clinical guideline, 9 (20.0%) had CDS, and 19 (42.2%) had neither. Compared with EDs with neither a clinical guideline nor CDS, visits to EDs with CDS (aOR 0.52 [0.47, 0.58]) or a clinical guideline (aOR 0.83 [0.78, 0.89]) had lower odds of including a CT for mTBI. ED length of stay and revisit rates did not differ based on the presence of a clinical guideline or CDS.

CONCLUSIONS

Clinical guidelines for mTBI, and particularly CDS, were associated with lower rates of head CT use without adverse clinical outcomes.

Racial Disparities in Diagnosis of Concussion and Minor Head Trauma and Mechanism of Injury in Pediatric Patients Visiting the Emergency Department

OBJECTIVE

To determine if racial/ethnic differences exist in the diagnosis and mechanism of injury among children and adolescents visiting the emergency department (ED) for concussion and minor head trauma (MHT).

STUDY DESIGN

A retrospective, cross-sectional study of patient (age ≤19 years) visits to the ED for concussion between 2010-2015, using the National Hospital Ambulatory Medical Care Survey, was completed. The primary study exposure was race/ethnicity. Outcome measures included ED visits that resulted in a concussion/MHT diagnosis and mechanism of injury. Mechanism categories included sport, motor vehicle collision, fall, assault, and other mechanism. A multivariable logistic regression and multinomial logistic regression were conducted to assess relationships between race/ethnicity and outcomes. Findings were weighted to reflect population estimates.

RESULTS

In total, 1263 child/adolescent visits for concussion/MHT were identified, representing an estimated 6.6 million child/adolescent visits nationwide. Compared with non-Hispanic White pediatric patients, non-Hispanic Black patients were least likely to have an ED visit for a concussion/MHT (P < .001; OR, 0.66; 95% CI, 0.52-0.83) The odds of non-Hispanic Black children/adolescents (OR, 3.80; 95% CI, 1.68-8.55) and children/adolescents of other race/ethnicity (OR, 4.93; 95% CI, 1.09-22.23) sustaining a concussion/MHT resulting from assault vs sport was higher.

CONCLUSIONS

Amid the emerging focus on sport-related concussion, these ethnic/racial differences in ED diagnosis of concussion/MHT demonstrate sociodemographic differences that warrant further attention. Assault may be a more common mechanism of concussion among children/adolescents of a racial minority.

Revisits, readmissions, and outcomes for pediatric traumatic brain injury in California, 2005-2014

Long-term outcomes related to emergency department revisit, hospital readmission, and all-cause mortality, have not been well characterized across the spectrum of pediatric traumatic brain injury (TBI). We evaluated emergency department visit outcomes up to 1 year after pediatric TBI, in comparison to a referent group of trauma patients without TBI. We performed a longitudinal, retrospective study of all pediatric trauma patients who presented to emergency departments and hospitals in California from 2005 to 2014. We compared emergency department visits, dispositions, revisits, readmissions, and mortality in pediatric trauma patients with a TBI diagnosis to those without TBI (Other Trauma patients). We identified 208,222 pediatric patients with an index diagnosis of TBI and 1,314,064 patients with an index diagnosis of Other Trauma. Population growth adjusted TBI visits increased by 5.6% while those for Other Trauma decreased by 40.7%. The majority of patients were discharged from the emergency department on their first visit (93.2% for traumatic brain injury vs. 96.5% for Other Trauma). A greater proportion of TBI patients revisited the emergency department (33.4% vs. 3.0%) or were readmitted to the hospital (0.9% vs. 0.04%) at least once within a year of discharge. The health burden within a year after a pediatric TBI visit is considerable and is greater than that of non-TBI trauma. These data suggest that outpatient strategies to monitor for short-term and longer-term sequelae after pediatric TBI are needed to improve patient outcomes, lessen the burden on families, and more appropriately allocate resources in the healthcare system.

Identifying Persistent Postconcussion Symptom Risk in a Pediatric Sports Medicine Clinic

BACKGROUND

Although most children report symptom resolution within a month of a concussion, some patients experience persistent postconcussion symptoms (PPCS) that continues for more than 1 month. Identifying patients at risk for PPCS soon after an injury can provide useful clinical information.

PURPOSE

To determine if the Predicting Persistent Post-concussive Problems in Pediatrics (5P) clinical risk score, an emergency department (ED)-derived and validated tool, is associated with developing PPCS when obtained in a primary care sports concussion setting.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We conducted a study of patients seen at a pediatric sports medicine concussion clinic between May 1, 2013, and October 1, 2017, who were <19 years of age and evaluated within 10 days of a concussion. The main outcome was PPCS, defined as symptoms lasting >28 days. Nine variables were used to calculate the 5P clinical risk score, and we assessed the association between the 5P clinical risk score and PPCS occurrence. The secondary outcome was total symptom duration.

RESULTS

We examined data from 230 children (mean age, 14.8 ± 2.5 years; 50% female; mean time from injury to clinical assessment, 5.6 ± 2.7 days). In univariable analyses, a greater proportion of those who developed PPCS reported feeling slowed down (72% vs 44%, respectively; P < .001), headache (94% vs 72%, respectively; P < .001), sensitivity to noise (71% vs 43%, respectively; P < .001), and fatigue (82% vs 51%, respectively; P < .001) and committed ≥4 errors in tandem stance (33% vs 7%, respectively; P < .001) than those who did not. Higher 5P clinical risk scores were associated with increased odds of developing PPCS (adjusted odds ratio [OR], 1.62 [95% CI, 1.30-2.02]) and longer symptom resolution times (β = 8.40 [95% CI, 3.25-13.50]). Among the individual participants who received a high 5P clinical risk score (9-12), the majority (82%) went on to experience PPCS. The area under the curve for the 5P clinical risk score was 0.75 (95% CI, 0.66-0.84). After adjusting for the effect of covariates, fatigue (adjusted OR, 2.93) and ≥4 errors in tandem stance (adjusted OR, 7.40) were independently associated with PPCS.

CONCLUSION

Our findings extend the potential use for an ED-derived clinical risk score for predicting the PPCS risk into the sports concussion clinic setting. While not all 9 predictor variables of the 5P clinical risk score were independently associated with the PPCS risk in univariable or multivariable analyses, the combination of factors used to calculate the 5P clinical risk score was significantly associated with the odds of developing PPCS. Thus, obtaining clinically pragmatic risk scores soon after a concussion may be useful for early treatments or interventions to mitigate the PPCS risk.

Burden of USA hospital charges for traumatic brain injury

OBJECTIVES

This study sought to estimate charges associated with USA hospital visits for traumatic brain injury (TBI), compare charges from 2006-2010 and evaluate factors associated with higher charges.

METHODS

The Nationwide Emergency Department Sample database, 2006-2010, was used to estimate charges for emergency department visits and inpatient hospital stays associated with TBI and trends in charges over time were compared. Multivariable linear regression was used to evaluate factors associated with visit charges.

RESULTS

In 2010, there were $21.4 billion (95% confidence interval (CI) = $17.7-$25.2 billion) in charges for TBI-related admissions, an increase of 22% from 2006. Charges for ED visits resulting in discharge or transfer were $8.2 billion (95% CI = $7.4-$8.9 billion), an increase of 94% from 2006. The proportion of charges for TBI-related visits was disproportionately higher than the proportion of visits for TBI across all years of the study (p < 0.001). Patient age and gender, West region, trauma centre status, non-paediatric hospital designation, metropolitan location and hospital ownership were independently associated with higher charges.

CONCLUSIONS

There was a substantial charge burden from TBI-related hospital visits and charges increased disproportionately to visit volume. There are patient and hospital factors independently associated with higher charges. These findings, as well as methods to reduce the charge burden and charge disparities, deserve further study.

Initial somatic symptoms are associated with prolonged symptom duration following concussion in adolescents

AIM

To determine which initial postinjury symptom domains are independently associated with symptoms lasting >28 days in youth athletes who sustained sport-related concussions.

METHODS

Patients who presented for care at a sport concussion clinic completed the postconcussion symptom scale. They were classified into two groups: those who reported symptom resolution within 28 days of injury and those who did not. Logistic regression models were constructed for children and adolescents to determine the independent association between symptom recovery and potential predictor variables: initial symptom scores in 5 postconcussion symptom scale domains (somatic, vestibular-ocular, cognitive, sleep and emotional), sex, loss of consciousness or amnesia at the time of injury, history of prior concussion, prior treatment for headaches or migraines, or family history of concussion.

RESULTS

Sixty-eight child (8-12 years of age) and 250 adolescent (13-18 years of age) athletes were included. For adolescents, initial somatic symptom severity was independently associated with prolonged symptom duration (adjusted odds ratio = 1.162; 95% CI: 1.060, 1.275) and no other predictor variables were. No potential predictor variables were independently associated with prolonged symptom duration for children.

CONCLUSION

Among adolescent athletes, a high initial somatic symptom burden (e.g. headache, nausea, vomiting, etc.) is associated with increased odds of symptoms beyond 28 days postinjury.

Physical Activity Level and Symptom Duration Are Not Associated After Concussion

BACKGROUND

Physical rest after a concussion has been described as a key component in the management of the injury. Evidence supporting this recommendation, however, is limited.

PURPOSE

To examine the association between physical activity and symptom duration in a cohort of patients after a concussion.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This study included 364 patients who were diagnosed with a concussion, were seen by a physician within 3 weeks of injury, and completed a questionnaire at the initial clinic visit. The questionnaire assessed the postconcussion symptom scale (PCSS) score, previous number of concussions, presence of the loss of consciousness or amnesia at the time of injury, and prior treatment for headaches. During each follow-up clinic visit, physical activity level was self-reported. A Cox proportional hazard model was constructed to determine the association between symptom duration, initial clinic visit responses, and self-reported physical activity level after the injury.

RESULTS

Study participants ranged in age from 8 to 27 years (mean age, 15.0 years) and had sustained a mean of 0.8 prior concussions; 222 patients (61%) were male. On initial examination, the mean PCSS score was 34.7. The mean symptom duration was 48.9 days after the injury. Among the variables included in the model, initial PCSS score and female sex were independently associated with symptom duration, while physical activity level after the injury was not. For participants aged between 13 and 18 years, however, higher levels of physical activity after the injury were associated with a shorter symptom duration.

CONCLUSION

Results from this study indicate that physical activity after the injury may not be universally detrimental to the recovery of concussion symptoms.

Variation in Computed Tomography Imaging for Pediatric Injury-Related Emergency Visits

OBJECTIVE

To assess variation in the use of computed tomography (CT) for pediatric injury-related emergency department (ED) visits.

STUDY DESIGN

This was a retrospective cohort study of visits to 14 network-affiliated EDs from November 2010 through February 2013. Visits were identified by International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. Primary outcome was CT use. We used descriptive statistics and performed multivariable logistic regression to evaluate the association of patient and ED covariates on any and body region-specific CT use.

RESULTS

Of the 80 868 injury-related visits, 11.4% included CT, and 28.4% of those involved more than 1 CT. Across EDs, CT use ranged from 7.6% to 25.5% of visits and did not correlate with institutional Injury Severity Score (P = .33) or admission/transfer rates (P = .07). In multivariable analysis of nonpediatric EDs, trauma centers and nonacademic EDs were associated with CT use. Higher pediatric volume was associated with any CT use; however, there was an inverse relationship between volume and nonhead CT use. When the pediatric ED was included in multivariable modeling, the effect of level 1-3 trauma center designation remained, and the pediatric level 1 trauma center was less likely to use most body region-specific CTs.

CONCLUSION

There is wide variation in CT imaging for pediatric injury-related visits not attributable solely to case mix. Future work to optimize CT utilization should focus on additional factors contributing to imaging practices and interventions.

Quality Improvement Effort to Reduce Cranial CTs for Children With Minor Blunt Head Trauma

OBJECTIVE

Blunt head trauma is a common injury in children, although it rarely requires surgical intervention. Cranial computed tomography (CT) is the reference standard for the diagnosis of traumatic brain injury but has been associated with increased lifetime malignancy risk. We implemented a multifaceted quality improvement initiative to decrease the use of cranial CT for children with minor head injuries.

METHODS

We designed and implemented a quality improvement effort that included an evidence-based guideline as well as individual feedback for children aged 0 to 21 years who present to the emergency department (ED) for evaluation of minor blunt head trauma. Our primary outcome was cranial CT rate, and our balancing measure was any return to the ED within 72 hours that required hospitalization. We used statistical process control methodology to measure cranial CT rates over time.

RESULTS

We included 6851 ED visits of which 4242 (62%) occurred in the post-guideline implementation period. From a baseline CT rate of 21%, we observed an absolute reduction of 6% in cranial CT rate (95% confidence interval 3% to 9%) after initial guideline implementation and an additional absolute reduction of 6% (95% confidence interval 4% to 8%) after initiation of individual provider feedback. No children discharged from the ED required admission within 72 hours of initial evaluation.

CONCLUSIONS

An ED quality improvement effort that included an evidence-based guideline as well as individual provider feedback was associated with a reduction in cranial CT rates without an increase in missed significant head injuries.

Effect of cognitive activity level on duration of post-concussion symptoms

OBJECTIVE

To determine the effect of cognitive activity level on duration of post-concussion symptoms.

METHODS

We conducted a prospective cohort study of patients who presented to a Sports Concussion Clinic within 3 weeks of injury between October 2009 and July 2011. At each visit, patients completed a scale that recorded their average level of cognitive activity since the previous visit. The product of cognitive activity level and days between visits (cognitive activity-days) was calculated and divided into quartiles. Kaplan-Meier Product Limit method was used to generate curves of symptom duration based on cognitive activity level. To adjust for other possible predictors of concussion recovery, we constructed a Cox proportional hazard model with cognitive activity-days as the main predictor.

RESULTS

Of the 335 patients included in the study, 62% were male, 19% reported a loss of consciousness, and 37% reported experiencing amnesia at the time of injury. The mean age of participants was 15 years (range, 8-23) and the mean number of previous concussions was 0.76; 39% of athletes had sustained a previous concussion. The mean Post-Concussion Symptom Scale score at the initial visit was 30 (SD, 26). The overall mean duration of symptoms was 43 days (SD, 53). Of all variables assessed, only total symptom burden at initial visit and cognitive activity level were independently associated with duration of symptoms.

CONCLUSIONS

Increased cognitive activity is associated with longer recovery from concussion. This study supports the use of cognitive rest and adds to the current consensus opinion.

Symptom severity predicts prolonged recovery after sport-related concussion, but age and amnesia do not

OBJECTIVE

To identify predictors of prolonged symptoms in athletes who sustain concussions.

STUDY DESIGN

This was a multicenter prospective cohort study of patients in 2 sport concussion clinics. Possible predictors of prolonged symptoms from concussion were compared in 2 groups, those whose symptoms resolved within 28 days and those whose symptoms persisted beyond 28 days. Candidate predictor variables were entered into a logistic regression model that was used to generate aORs.

RESULTS

A total of 182 patients met the inclusion criteria during the study period. The mean patient age was 15.2 ± 3.04 years. More than one-third of the patients (n = 65) underwent computerized neurocognitive testing on their initial visit. On univariate analyses, Post-Concussion Symptom Scale (PCSS) score and all composite scores on computerized neurocognitive testing were apparently associated with prolonged symptom duration. Sex, age, loss of consciousness at time of injury, and amnesia at time of injury were not associated with prolonged symptom duration. After adjusting for potential confounding, only total PCSS score was associated with the odds of suffering prolonged symptoms.

CONCLUSION

Further efforts to develop clinical tools for predicting which athletes will suffer prolonged recoveries after concussion should focus on initial symptom score.

Management strategies and medication use for treating paediatric patients with concussions

AIM

To assess management strategies for paediatric patients suffering from concussions.

METHODS

A 17-item questionnaire was distributed to 1305 section members of the American Academy of Pediatrics Sections on Adolescent Health, Sports Medicine and Fitness, Community Pediatrics and School Health. The use of medications, neuropsychological testing, neuroimaging and published guidelines in concussion management was queried.

RESULTS

Two hundred and twenty respondents (17%) completed the questionnaire, of which 64% had been an attending for greater than 10 years. A majority of respondents (92%) managed patients with concussions, with 26% treating more than 24 patients per year. Most paediatricians (84%) reported using a published guideline. The majority of respondents (89%) manage the symptoms of concussed patients with medications, most commonly acetaminophen (62%) or nonsteroidal anti-inflammatory medications (54%). The use of prescriptions medications such as tricyclic antidepressants (23%), amantadine (10%) and methylphenidate (8%) was also commonly reported. Paediatricians treating >16 patients per year with concussion were more likely to prescribe tricyclic antidepressants, stimulants and agents used for sleep disturbance.

CONCLUSION

Paediatricians nationwide routinely use medications when managing patients with concussions. The pharmacological agents used differ according to number of patients treated per year. In addition, most paediatricians use published guidelines in concussion management.

Bicycle helmet laws are associated with a lower fatality rate from bicycle-motor vehicle collisions

OBJECTIVE

To assess the association between bicycle helmet legislation and bicycle-related deaths sustained by children involved in bicycle-motor vehicle collisions.

STUDY DESIGN

We conducted a cross-sectional study of all bicyclists aged 0-16 years included in the Fatality Analysis Reporting System who died between January 1999 and December 2010. We compared fatality rates in age-specific state populations between states with helmet laws and those without helmet laws. We used a clustered Poisson multivariate regression model to adjust for factors previously associated with rates of motor vehicle fatalities: elderly driver licensure laws, legal blood alcohol limit (<0.08% vs ≥ 0.08%), and household income.

RESULTS

A total of 1612 bicycle-related fatalities sustained by children aged <16 years were evaluated. There were no statistically significant differences in median household income, the proportion of states with elderly licensure laws, or the proportion of states with a blood alcohol limit of >0.08% between states with helmet laws and those without helmet laws. The mean unadjusted fatality rate was lower in states with helmet laws (2.0/1,000,000 vs 2.5/1,000,000; P = .03). After adjusting for potential confounding factors, lower fatality rates persisted in states with mandatory helmet laws (adjusted incidence rate ratio, 0.84; 95% CI, 0.70-0.98).

CONCLUSION

Bicycle helmet safety laws are associated with a lower incidence of fatalities in child cyclists involved in bicycle-motor vehicle collisions.

Detrimental effect of genetic inhibition of B-site APP-cleaving enzyme 1 on functional outcome after controlled cortical impact in young adult mice

β-Amyloid (Aβ) peptides, most notably associated with Alzheimer's disease, have been implicated in the pathogenesis of secondary injury after traumatic brain injury (TBI). A prior study has demonstrated that blocking the β-site amyloid precursor protein (APP)-cleaving enzyme 1 (Bace1) required for production of Aβ from APP improved functional and histologic outcomes after controlled cortical impact (CCI) in aged mice. However, the majority of patients with severe TBI are young adults under the age of 40. Prior experimental models have suggested age-dependent differences in Aβ clearance, and a recent study in our lab suggests that young animals remediate acute elevations in Aβ after CCI better than older animals. We therefore tested the hypothesis that Bace1 deletion in young adult mice would not be protective after CCI. Male Bace1 knockout (Bace1(-/-)) and wild-type Bace1(+/+) (C57BL/6) mice (2-3 months old) were subjected to CCI (n=18-23/group) or sham injury (n=10-12/group). Functional outcomes were assessed with wire grip (motor) and the Morris water maze (MWM; spatial memory). Soluble Aβ levels were assessed at 48 h after CCI. Histopathological outcomes were assessed by lesion and hippocampal volume. Clustered ordinal logistic regression showed overall significant impairment in motor performance in injured Bace1(-/-) versus Bace1(+/+) animals (p=0.003). No significant differences in MWM performance were found on repeated-measures ANOVA (p=0.11) between groups. Probe scores were significantly worse in injured Bace1(-/-) versus Bace1(+/+) mice (p=0.0009). Soluble Aβ(40) was significantly lower in ipsilateral hemispheres of Bace1(-/-) than in Bace1(+/+) animals after CCI (0.9 [IQR 0.88-0.94] pmol/g protein versus 3.8 [IQR 2.4-6.0] pmol/g protein; p=0.005). Lesion and hippocampal volumes did not differ between injured groups. The data suggest that therapies targeting Bace1 may need to be tailored according to age and injury severity, as their use may exacerbate functional deficits after TBI in younger or less severely injured patients.

Cardiac troponin increases among runners in the Boston Marathon

STUDY OBJECTIVE

Studies indicate that running a marathon can be associated with increases in serum cardiac troponin levels. The clinical significance of such increases remains unclear. We seek to determine the prevalence of troponin increases and epidemiologic factors associated with these increases in a large and heterogeneous cohort of marathon finishers.

METHODS

Entrants in the 2002 Boston Marathon were recruited 1 to 2 days before the race. Data collected included demographic and training history, symptoms experienced during the run, and postrace troponin T and I levels. Simple descriptive statistics were performed to describe the prevalence of troponin increases and runner characteristics.

RESULTS

Of 766 runners enrolled, 482 had blood analyzed at the finish line. In all, 34% were women, 20% were younger than 30 years, and 92% had run at least 1 previous marathon. Most runners (68%) had some degree of postrace troponin increase (troponin T > or = 0.01 ng/mL or troponin I > or = 0.1 ng/mL), and 55 (11%) had significant increases (troponin T > or = 0.075 ng/mL or troponin I > or = 0.5 ng/mL). Running inexperience (< 5 previous marathons) and young age (< 30 years) were associated with elevated troponins. These correlates were robust throughout a wide range of troponin thresholds considered. Health factors, family history, training, race performance, and symptoms were not associated with increases.

CONCLUSION

Troponin increases were relatively common among marathon finishers and can reach levels typically diagnostic for acute myocardial infarction. Less marathon experience and younger age appeared to be associated with troponin increases, whereas race duration and the presence of traditional cardiovascular risk factors were not. Further work is needed to determine the clinical significance of these findings.

The Boston Marathon Study: a novel approach to research during residency

Resident physicians from a pediatric academic training program developed a hospital-wide research project in an effort to enhance their residency research experience. In this model, residents themselves assumed primary responsibility for each stage of a large prospective clinical research study. The project, which was integrated successfully into the residency program, enabled a large group of residents, with mentorship from a dedicated faculty member, to benefit from a structured clinical research experience while providing the flexibility necessary to meet the demands of a busy residency curriculum. Careful topic selection with a well-defined end point, faculty involvement, resident collegiality, and institutional support were factors identified by study leaders as central to the success of this model.

Hyponatremia among runners in the Boston Marathon

BACKGROUND

Hyponatremia has emerged as an important cause of race-related death and life-threatening illness among marathon runners. We studied a cohort of marathon runners to estimate the incidence of hyponatremia and to identify the principal risk factors.

METHODS

Participants in the 2002 Boston Marathon were recruited one or two days before the race. Subjects completed a survey describing demographic information and training history. After the race, runners provided a blood sample and completed a questionnaire detailing their fluid consumption and urine output during the race. Prerace and postrace weights were recorded. Multivariate regression analyses were performed to identify risk factors associated with hyponatremia.

RESULTS

Of 766 runners enrolled, 488 runners (64 percent) provided a usable blood sample at the finish line. Thirteen percent had hyponatremia (a serum sodium concentration of 135 mmol per liter or less); 0.6 percent had critical hyponatremia (120 mmol per liter or less). On univariate analyses, hyponatremia was associated with substantial weight gain, consumption of more than 3 liters of fluids during the race, consumption of fluids every mile, a racing time of >4:00 hours, female sex, and low body-mass index. On multivariate analysis, hyponatremia was associated with weight gain (odds ratio, 4.2; 95 percent confidence interval, 2.2 to 8.2), a racing time of >4:00 hours (odds ratio for the comparison with a time of <3:30 hours, 7.4; 95 percent confidence interval, 2.9 to 23.1), and body-mass-index extremes.

CONCLUSIONS

Hyponatremia occurs in a substantial fraction of nonelite marathon runners and can be severe. Considerable weight gain while running, a long racing time, and body-mass-index extremes were associated with hyponatremia, whereas female sex, composition of fluids ingested, and use of nonsteroidal antiinflammatory drugs were not.

Effects of breathing parameters on sidestream cigarette smoke deposition in a hollow tracheobronchial model

The effects of variations in cyclic breathing parameters (i.e., tidal volume and breath frequency) have been the subject of few studies devoted to the deposition of submicrometer aerosols in the human respiratory tract. Therefore, a series of experiments was performed to investigate whether the deposition efficiency (DE) of sidestream cigarette smoke is altered by varying tidal volume and breath frequency in a child-size hollow tracheobronchial (TB) model while maintaining a fixed minute ventilation rate of 5 L/min. Under cyclic flow conditions with tidal volumes of 100 mL (50 breaths/min), 250 mL (20 breaths/min), 500 mL (10 breaths/min) and 750 mL (6.7 breaths/min), sidestream cigarette smoke was passed through replicas of an idealized hollow TB model. The smoke deposits were extracted and then quantitated spectrophotometrically. The experiments revealed a significant difference in DE between the 100-mL tidal volume (DE = 6.0%) and the 750-mL tidal volume (DE = 11.1%). Under equivalent steady flow conditions, the mean DE was 21.5%. A trend was evident in the data--DE increased as tidal volume increased (and breathing frequency decreased)--suggesting that the influence of diffusion and secondary flows on DE becomes greater as the air residence time increases and the degree of air turbulence decreases. The results provide evidence of the importance of breathing parameters when attempting to model in vivo deposition of environmental tobacco smoke and other similar-size respirable aerosols.

Deposition of monodisperse particles in hollow models representing adult and child-size tracheobronchial airways

A series of experiments was performed to determine deposition efficiencies of four sizes of radiolabeled monodisperse particles in custom-made hollow tracheobronchial models. The particles had geometric diameters of about 1, 5, 10, and 15 microm. The tracheobronchial models, consisting of a trachea and two or more additional generations, had dimensions representative of a typical adult, a 7-y-old child, and a 4-y-old child; the child-size models were appropriately scaled-down replicas of the adult-size model. Each deposition experiment was conducted using a steady inspiratory airflow representative of low physical activity for the appropriate age of individual: 20 L min(-1) for the adult; 9 L min(-1) for the 7-y-old; 5.5 L min(-1) for the 4-y-old. The results indicate that deposition efficiency of the particles increased substantially (up to 35 times) in all three models as particle diameter increased from 1-15 microm, undoubtedly as a result of particle impaction and sedimentation-related phenomena. An analysis of variance demonstrated the occurrence of statistically-significant (p < 0.05) main effects of hollow model size and particle size; the interaction between the two parameters was also significant. In general, deposition efficiencies of the various sizes of particles were greater in the child-size models than in the adult-size model; this effect may have risk assessment implications. In addition, the results obtained experimentally agreed more closely with those predicted using a radiation-protection mathematical particle deposition formulation as the particle size increased for each of the sizes of models.

Physical characterization of incense aerosols

Experiments were performed to study the physical characteristics of smoke aerosols generated by burning three types of stick incense in a 4 m3 clean room. Sidestream cigarette smoke was also examined under the same conditions to provide a comparison. Among the parameters measured were (a) masses of aerosol, carbon monoxide and nitrogen oxides generated by burning the incense or cigarettes, (b) rates of decay of the particles from the air, and (c) estimates of count median particle size during a 7 h period post-burning. There was variability among the types of incense studied with respect to many of the parameters. Also, as a general trend, the greater the initial particulate mass concentration, the more rapid the rate of decay of the smoke. In relation to the quantity of particulate generated, cigarette smoke was found to produce proportionally larger quantities of carbon monoxide and nitrogen oxides than did incense. Due to the fact that burning incense was found to generate large quantities of particulate (an average of greater than 45 mg/g burned, as opposed to about 10 mg/g burned for the cigarettes), it is likely, in cases in which incense is habitually burned in indoor settings, that such a practice would produce substantial airborne particulate concentrations.

Effects of nitrogen dioxide on respiratory tract clearance in the ferret

During growth and development, young children are periodically exposed to relatively high concentrations of various air contaminants, including tobacco smoke and environmental pollutants generated by fossil fuel use. The effects of these exposures on respiratory function and lung development are difficult to determine because of interindividual variation and lack of accurate dosimetry. To provide information on the effects of chronic exposure to a common indoor and outdoor pollutant during lung development, a study was performed to assess the effects of exposure to two concentrations of nitrogen dioxide (NO2; 0.5 or 10 ppm) on tracer particle clearance from the airways of ferrets exposed during postnatal respiratory tract development. Separate groups of ferrets were exposed nose-only to the test atmospheres or clean air 4 h/d, 5 d/wk, for either 8 or 15 wk. Those animals exposed for 8 wk were subsequently housed in a filtered air environment until the particle clearance measurements commenced at 3 wk prior to the end of the 15-wk exposure protocol. Radiolabeled (51Cr) tracer particles were deposited in the respiratory tract of all animals by inhalation, and the clearance rates from the head and thoracic regions were separately monitored for 18 d. No significant effects of the NO2 exposure on head airways clearance were seen. In contrast, the rates of particle clearance from the thorax of both the 8- and 15-wk groups exposed to 10 ppm NO2 were significantly reduced, and did not differ from each other. Thoracic clearance was also reduced in animals exposed to 0.5 ppm, but the rate was not significantly different from that of the clean air exposed controls. These results show that NO2 at moderate concentrations caused highly significant changes in the deep lung of the juvenile ferret, and suggest that impairment of the clearance function may be only slowly recovered after chronic exposure.

Health effects of acid aerosols formed by atmospheric mixtures

Under ambient conditions, sulfur and nitrogen oxides can react with photochemical products and airborne particles to form acidic vapors and aerosols. Inhalation toxicological studies were conducted, exposing laboratory animals, at rest and during exercise, to multicomponent atmospheric mixtures under conditions favorable to the formation of acidic reaction products. Effects of acid and ozone mixtures on early and late clearance of insoluble radioactive particles in the lungs of rats appeared to be dominated by the oxidant component (i.e., the mixture did cause effects that were significantly different from those of ozone alone). Histopathological evaluations showed that sulfuric acid particles alone did not cause inflammatory responses in centriacinar units of rat lung parenchyma (expressed in terms of percent lesion area) but did cause significant damage (cell killing followed by a wave of cell replication) in nasal respiratory epithelium, as measured by uptake of tritiated thymidine in the DNA of replicating cells. Mixtures of ozone and nitrogen dioxide, which form nitric acid, caused significant inflammatory responses in lung parenchyma (in excess of effects seen in rats exposed to ozone alone), but did not damage nasal epithelium. Mixtures containing acidic sulfate particles, ozone, and nitrogen dioxide damaged both lung parenchyma and nasal epithelia. In rats exposed at rest, the response of the lung appeared to be dominated by the oxidant gas-phase components, while responses in the nose were dominated by the acidic particles. In rats exposed at exercise, however, mixtures of ozone and sulfuric acid particles significantly (2.5-fold) elevated the degree of lung lesion formation over that seen in rats exposed to ozone alone under an identical exercise protocol.

Effects of pollutant atmospheres on surface receptors of pulmonary macrophages

The effects of two multicomponent pollutant atmospheres on the surface receptors (FcR) and phagocytic activity of rat pulmonary alveolar macrophages have been studied. FcR are crucial for the macrophages to become cytotoxic against target cells. The atmospheres were composed of pollutants that are prevalent in the South Coast Air Basin of southern California. Rats were exposed nose-only to a 7-component oxidant-and sulfate-containing atmosphere for 4 h/d for either 7 or 21 consecutive days. In another experiment rats were exposed 5 h/d for 5 consecutive days to another pollutant combination--acid droplets plus carbon-containing dilute diesel engine exhaust. In both experiments matched rats were exposed nose-only to purified air to be used as controls. Each of the atmospheres studied significantly reduced FcR activity for at least 3 d following the exposure, with the group of rats exposed to the 7-component atmosphere for 21 d exhibiting the most pronounced effect. Macrophages from rats exposed to the diesel exhaust plus acid atmosphere and the 7-component atmosphere for 7 d had significantly reduced phagocytic activity for at least 3 d postexposure, while the macrophages from rats exposed to the latter atmosphere for 21 d had phagocytic activity near control values. The decrease in phagocytosis and inhibition of FcR of macrophages suggests an impairment of macrophage function that probably renders the host vulnerable to bacterial and/or viral infections.

Tracheal and bronchoalveolar permeability changes in rats inhaling oxidant atmospheres during rest or exercise

Permeability of tracheal and bronchoalveolar airways of rats was measured and used to examine the effects of inhaled oxidant-containing atmospheres. The atmospheres studied were (a) ozone (O3) at 0.6 ppm (1.2 mg/m3) or 0.8 ppm (1.6 mg/m3); (b) nitrogen dioxide (NO2) at 6 ppm (11.3 mg/m3) or 12 ppm (22.6 mg/m3); (c) O3 + NO2 at 0.6 ppm (1.2 mg/m3) and 2.5 ppm (4.7 mg/m3), respectively; and (d) a 7-component particle and gas mixture (complex atmosphere) representing urban air pollution in a photochemical environment. The rats were exposed for 2 h. The effects of exercise during exposure were evaluated by exposing additional groups in an enclosed treadmill. Exposure of resting rats to 0.8 ppm O3 increased tracheal permeability to DTPA and bronchoalveolar permeability to diethylenetriamine pentaacetate (DTPA) and bovine serum albumin (BSA) at 1 h after the exposure. Bronchoalveolar, but not tracheal, permeability remained elevated at 24 h after the exposure. Exercise during exposure to O3 increased permeability to both tracers in the tracheal and the bronchoalveolar zones, and prolonged the duration of increased permeability in the tracheal zone from 1 h to 24 h, and in the bronchoalveolar zone from 24 h to 48 h. Permeability in the tracheal and bronchoalveolar zones of rats exposed at rest to 6 or 12 ppm NO2 did not differ from controls. However, rats exposed during exercise to 12 ppm NO2 for 2 h developed a significant increase in tracheal and bronchoalveolar permeability to DTPA and BSA at 1 h, but not at 24 or 48 h, after exposure. Exposure at rest to 0.6 ppm O3 plus 2.5 ppm NO2 significantly increased bronchoalveolar permeability at 1 and 24 h after exposure, although exposure at rest to 0.6 ppm O3 alone increased bronchoalveolar permeability only at 1 h after exposure. Exposure to O3 + NO2 during exercise led to significantly greater permeability to DTPA than did exercising exposure to O3 alone. Resting rats exposed to a complex gas/aerosol atmosphere composed of the above O3 and NO2 concentrations, plus 5 ppm (13.1 mg/m3) sulfur dioxide (SO2) and an aerosol of insoluble colloidal Fe2O3 with an aerosol of manganese, ferric, and ammonium salts, demonstrated increased permeability at 1 and 24 h after exposure. Nitric acid vapor was formed in both the O3 + NO2 atmosphere and the complex gas/aerosol atmosphere.(ABSTRACT TRUNCATED AT 400 WORDS)

Relative permeability of nasal, tracheal, and bronchoalveolar mucosa to macromolecules in rats exposed to ozone

Nasal, tracheal and bronchoalveolar injuries resulting from acute ozone exposure of rats were investigated by permeability changes. 99mTc-labeled diethylenetriaminepentaacetate (DPTA) and 125I-labeled bovine serum albumin (BSA) were selectively instilled into localized airway regions of anesthetized rats exposed to 0.8 ppm 03 or clean air for 2 h. Transmucosal transfer of the radiolabeled tracers was detected by counting the radioactivity in blood samples collected at short postinstillation time intervals. Permeability measurements were made on d 0, 1, and 2 after O3 exposure to analyze the extent and persistence of tissue injury in the nasal, tracheal, and bronchoalveolar regions. Normal mucosal permeability was low in nose, intermediate in bronchoalveolar zone, and high in trachea. The O3-related injury, reflected by elevated permeability, was substantial in the trachea and bronchoalveolar zone but was minimal in the nose immediately after the exposure. Abnormal permeability persisted for less than 24 h in the trachea but for more than 24 h in the bronchoalveolar zone. The results are consistent with the properties of O3 of causing greater injury in the smaller airways and the alveolar zone than in the trachea.

Inhalation exposure methodology

Modern man is being confronted with an ever-increasing inventory of potentially toxic airborne substances. Exposures to these atmospheric contaminants occur in residential and commercial settings, as well as in the workplace. In order to study the toxicity of such materials, a special technology relating to inhalation exposure systems has evolved. The purpose of this paper is to provide a description of the techniques which are used in exposing laboratory subjects to airborne particles and gases. The various modes of inhalation exposure (whole body, head only, nose or mouth only, etc.) are described at length, including the advantages and disadvantages inherent to each mode. Numerous literature citations are included for further reading. Among the topics briefly discussed are the selection of appropriate animal species for toxicological testing, and the types of inhalation studies performed (acute, chronic, etc.).

Effects of sulfur dioxide and formaldehyde on particle clearance in the rat

The effects of exposures to sulfur dioxide and formaldehyde atmospheres on the clearance of inhaled, insoluble tracer particles from the lungs of rats have been studied. The tracer particles employed were polystyrene latex microspheres radio-labeled with 51Cr. Following the deposition of the 1.9-micron activity median aerodynamic diameter (AMAD) particles, the rats were divided into 3 groups for a single 4-h exposure to purified air, 20 ppm sulfur dioxide, or 20 ppm formaldehyde. Early, presumably upper-respiratory-tract, clearance was monitored by analysis of radioactivity excreted in feces, while late, presumably deep-lung, clearance was followed by thoracic counting of the animals. Both the sulfur dioxide and formaldehyde atmospheres did significantly delay early clearance (p less than 0.1, two-tailed t-test). However, the late clearance rates of the two pollutant-exposed groups of rats were not significantly different from that of the purified air-exposed group of rats. Although sulfur dioxide had numerically greater effects than formaldehyde, the differences were not statistically significant at the p less than 0.1 level.

Effect of sulfur dioxide-sulfate exposure on rat respiratory tract clearance

The effects of a 4 hour exposure to a model sulfur pollutant atmosphere on the clearance of inhaled insoluble tracer particles from the lungs of rats has been studied. The pollutant combination consisted of 5 ppm of sulfur dioxide gas and 1.5 mg/m3 of sulfate aerosol at 80-85% relative humidity. The exposure atmosphere was aged for 30 minutes upstream of the exposure chamber in an aging line in order to provide for gas/ particle interactions such as those occurring in industrial and environmental atmosphere. Results indicate that the sulfur pollutant atmosphere did not produce a statistically significant alteration in early (nasopharyngeal and tracheobronchial) or late (parenchymal) clearance rates such as those which have been identified in this laboratory following exposure to ozone-containing atmospheres.