Equine exercise-induced pulmonary hemorrhage: the role of high left-heart pressures secondary to exercise-induced hypervolemia, and high inspiratory pressures.

Exercise-induced hypervolemia is normal in racehorses. Stress failure of the blood-gas barrier causes EIPH and occurs when the transmural pulmonary capillary (Pcap)-alveolar pressure difference (Ptm) exceeds the barrier's stress failure threshold. Why Pcap increases is incompletely understood. We hypothesized that alterations in blood volume (BV) affect left ventricular (LV) and pulmonary arterial wedge (PAW) pressures, and Pcap, and correspondingly affect EIPH severity. Six thoroughbreds with EIPH underwent treadmill exercise at the same speed (≈11.9m/s [11.1, 12.2]; median [IQR]) before (≈119%V̇O2max; B), 2hr after 14L depletion of blood (≈132%V̇O2max; D) and 2hr after reinfusing the blood (≈111%V̇O2max; R). LV, pulmonary arterial (PAP), PAW and intrapleural (Ppl) pressures were measured throughout exercise. Pcap = (PAP+PAW)/2 and Ptm = Pcap - Ppl. EIPH severity was assessed 60min post-exercise by tracheoendoscopy (EIPHgrade) and bronchoalveolar lavage erythrocyte count (BALRBC). A mixed-effect model and Tukey post-hoc test analyzed effects of BV changes on LV, PAW, Pcap, Ppl, Ptm and EIPH. p≤0.05 was significant. EIPH severity was affected by BV (EIPHgrade: p=0.01, BALRBC: p=0.003). Peak Ptm was not different between B (146mmHg [140; 151]) and R (151mmHg [137; 160]) but was lower for D (128mmHg [127; 130]; B: p=0.005, R: p=0.02). LV end diastolic pressure (LVED) was correlated with maxPcap (r2=0.52, p=0.001). Ppl was unaffected by changes in BV. Vascular pressures and Ppl fluctuated constantly during exercise and independently influenced Ptm. Circulating BV but not exercise intensity had a major effect on LVED, Pcap and Ptm, and was correlated with EIPH severity in thoroughbred racehorses (r2=0.48, p=0.001).

Publications Among Pain Medicine Fellowship-Trained American Board of Anesthesiology Diplomates.

American Board of Anesthesiology (ABA) diplomates who pursue clinical fellowship training in pain medicine may be better suited to lead scholarly projects and serve as first authors of publications in peer-reviewed journals given their additional training and clinical expertise. The primary aim of this study was to determine whether ABA certification in pain medicine is associated with a greater number of peer-reviewed publications. The secondary aim included assessments of whether pain medicine fellowship training is associated with a higher publication rate (publications per year) or publication in a larger number of peer-reviewed journals. A literature search was conducted in December 2023 using the Scopus database for publications related to anesthesiology and pain medicine in the United States between 2013 and 2023. First authors identified through the search were then individually searched within the ABA physician directory. The following data were collected: author name and identification number, year of publication, publication type (article or review), year of primary anesthesiology certification, and year of fellowship, if applicable. This study identified 9,612 publications and 6,924 unique first authors. Pain medicine fellowship training was associated with a statistically significant increase (p-value < 0.001) in the number of publications (0.546; 95% confidence interval {CI}, 0.386-0.707), publications per year (0.140; 95% CI, 0.121-0.159), and publication in a larger number of peer-reviewed journals (0.256; 95% CI, 0.182-0.330) in regression models adjusted for the number of years from certification. This query of the Scopus database and ABA physician directory indicates that pain medicine fellowship training is associated with statistically significant increases in research productivity, as defined by the number of publications, publications per year, or the number of publications in peer-reviewed journals. However, these increases in research output would not lead to a marked increase in scholarship productivity to justify pursuing a fellowship for this purpose.

Quality Improvement Projects and Anesthesiology Graduate Medical Education: A Systematic Review.

Quality improvement (QI) projects are essential components of graduate medical education and healthcare organizations to improve patient outcomes. We systematically reviewed the literature on QI projects in anesthesiology graduate medical education programs to assess whether these projects are leading to publications. A literature search was conducted in July 2023, using PubMed, Embase, and the Central Register of Controlled Trials (CENTRAL) for articles describing QI initiatives originating within the United States and applicable to anesthesiology residency training programs. The following data were collected: intervention(s), sample size (number of participants or events), outcome metric(s), result(s), and conclusion(s). One hundred and fifty publications were identified, and 31 articles met the inclusion criteria. A total of 2,259 residents and 72,889 events were included in this review. Educational modalities, such as simulation, training sessions, or online curricula, were the most prevalent interventions in the included studies. Pre-intervention and post-intervention assessments were the most common outcome metrics reported. Our review of the literature demonstrates that few QI projects performed within anesthesiology training programs lead to published manuscripts. Further research should aim at increasing the impact of required QI projects within the sponsoring institution and specialty.

Adaptive social contact rates induce complex dynamics during epidemics.

Epidemics may pose a significant dilemma for governments and individuals. The personal or public health consequences of inaction may be catastrophic; but the economic consequences of drastic response may likewise be catastrophic. In the face of these trade-offs, governments and individuals must therefore strike a balance between the economic and personal health costs of reducing social contacts and the public health costs of neglecting to do so. As risk of infection increases, potentially infectious contact between people is deliberately reduced either individually or by decree. This must be balanced against the social and economic costs of having fewer people in contact, and therefore active in the labor force or enrolled in school. Although the importance of adaptive social contact on epidemic outcomes has become increasingly recognized, the most important properties of coupled human-natural epidemic systems are still not well understood. We develop a theoretical model for adaptive, optimal control of the effective social contact rate using traditional epidemic modeling tools and a utility function with delayed information. This utility function trades off the population-wide contact rate with the expected cost and risk of increasing infections. Our analytical and computational analysis of this simple discrete-time deterministic strategic model reveals the existence of an endemic equilibrium, oscillatory dynamics around this equilibrium under some parametric conditions, and complex dynamic regimes that shift under small parameter perturbations. These results support the supposition that infectious disease dynamics under adaptive behavior change may have an indifference point, may produce oscillatory dynamics without other forcing, and constitute complex adaptive systems with associated dynamics. Implications for any epidemic in which adaptive behavior influences infectious disease dynamics include an expectation of fluctuations, for a considerable time, around a quasi-equilibrium that balances public health and economic priorities, that shows multiple peaks and surges in some scenarios, and that implies a high degree of uncertainty in mathematical projections.

Human adaptation to climate change: An introduction to the special issue.

OBJECTIVES: Despite our focus on adaptation and human responses to climate, evolutionary and biological anthropologists (EBAs) are largely absent from conversations about contemporary "climate-change adaptation," a term popular in other disciplines, the development world, and related policy decisions. EBAs are missing a big opportunity to contribute to impactful, time-sensitive applied work: we have extensive theoretical and empirical knowledge pertinent to conversations about climate-change adaptation and to helping support communities as they cope. This special issue takes a tour of EBA contributions to our understanding of climate-change adaptation, from data on past and contemporary human communities to theoretically informed predictions about how individuals and communities will respond to climate change now and in the future. First, however, we must establish what we mean by "climate change" and "adaptation," along with other terms commonly used by EBAs; review what EBAs know about adaptation and about human responses to climate change; and identify just a few topics EBAs study that are pertinent to ongoing conversations about climate-change adaptation. In this article, we do just that. CONCLUSION: From our work on energy use to our work on demography, subsistence, social networks, and the salience of climate change to local communities, EBAs have an abundance of data and theoretical insights to help inform responses to contemporary climate change. We need to better reach the climate community and general public with our contributions.

Cardiopulmonary function during supramaximal exercise in hypoxia, normoxia and hyperoxia in Thoroughbred horses.

Supramaximal exercise while inspiring different O2 gases may induce different responses in cardiopulmonary function at the same relative and/or absolute exercise intensity. The purpose of this study was to compare the effects of supramaximal exercise in hypoxia, normoxia and hyperoxia on cardiopulmonary function in Thoroughbred horses. Using a crossover design, five well-trained horses were made to run up a 6% grade on a treadmill at supramaximal speeds sustainable for approximately 110 sec (approximately 115% V̇O2max) while breathing normoxic gas (NO, 21% O2) or hypoxic gas (LO, 15.3% O2) in random order. Horses also ran at the same speed, incline and run time as in NO while breathing hyperoxic gas (HONO, 28.8% O2) and as in LO while breathing normoxic gas (NOLO). Runs were on different days, and cardiopulmonary variables were analyzed with repeated-measures ANOVA and the Holm-Sidák method for pairwise comparisons. Supramaximal speeds differed significantly between NO and LO (14.0 ± 0.5 [SD] m/sec vs. 12.6 ± 0.5 m/sec), but run times to exhaustion did not (112 ± 17 sec vs. 103 ± 14 sec). The V̇O2max in NO was higher than that in LO (165 ± 11 vs. 120 ± 15 ml (min× kg)), as was the arterial oxygen tension (66 ± 5 vs. 45 ± 2 Torr). Oxygen consumption was increased in HONO and NOLO compared with the values in NO and LO, respectively. Supramaximal exercise in hypoxia induces more severe hypoxemia and decreases V̇O2max compared with normoxia at the same relative intensity. Conversely, supramaximal exercise in hyperoxia alleviates hypoxemia and increases V̇O2 compared with normoxia at the same absolute intensity.

Effects of exercise, furosemide, blood depletion, and reinfusion on body fluid compartment volumes in horses.

High pulmonary blood pressure contributes to exercise-induced pulmonary hemorrhage. The objective of this study was to use bioimpedance spectroscopy to assess body fluid compartment volumes under 3 conditions in 6 racehorses: i) Pre- and post-supramaximal treadmill exercise (control); ii) Exercise 4 hours after furosemide (0.5 mg/kg body weight, IV); iii) Exercise, removal of ~14 L of blood and subsequent reinfusion of the blood. Statistical analysis used linear mixed effects models. Body compartment volumes did not change during the control runs. Total body water (TBW) (P = 0.007, P = 0.007), extracellular fluid (ECF) (P = 0.003, P = 0.003), and intracellular fluid (ICF) volumes (P = 0.04, P = 0.04) decreased pre- and post-exercise following furosemide administration. The ICF trended to decrease (P = 0.07) after slow removal of blood. Blood reinfusion increased TBW (P = 0.02, P = 0.02) and ICF (P = 0.005, P = 0.005) pre- and post-exercise.

Effets de l'exercice, du furosémide, de la diminution sanguine et de la ré-infusion sur les volumes des liquides corporels compartimentés chez les chevaux. Une pression sanguine pulmonaire élevée contribue à des hémorragies pulmonaires induites par l'exercice. L'objectif de la présente étude était d'utiliser la spectroscopie à bio-impédance pour évaluer les volumes des liquides corporels compartimentés sous trois conditions chez six chevaux de course : i) Pré- et post-supramaximal exercice au tapis roulant (témoin); ii) Exercice 4 h après administration de furosémide (0,5 mg/kg de poids corporel, IV); iii) Exercice, retrait d'environ 14 L de sang et ré-infusion subséquente du sang. Les analyses statistiques utilisaient des modèles linéaires à effets mixtes. Les volumes des compartiments corporels n'ont pas changé durant les essais témoins. Les volumes de la quantité totale d'eau corporelle (TBW) (P = 0,007, P = 0,007), de liquide extracellulaire (ECF) (P = 0,003, P = 0,003) et liquide intracellulaire (ICF) (P = 0,04, P = 0,04) ont diminué pré- et post-exercice à la suite de l'administration de furosémide. L'ICF avait tendance à diminuer (P = 0,07) à la suite du lent retrait de sang. La ré-infusion de sang augmenta la TBW (P = 0,02, P = 0,02) et l'ICF (P = 0,005, P = 0,005) pré- et post-exercice.(Traduit par Dr Serge Messier).

Physiologic effects of furosemide in combination with water restriction when administered at 4 and 24 hours prior to high-intensity treadmill training.

Although controversial, due to its reported effectiveness in attenuating bleeding associated with exercise-induced pulmonary hemorrhage (EIPH), furosemide is currently a permitted race day medication in most North American racing jurisdictions. The objective of this study was to assess the efficacy of furosemide in reducing the presence and severity of EIPH when administered 24 hr prior to strenuous treadmill exercise. Eight exercised Thoroughbred horses received saline or 250 mg of furosemide either 4 or 24 hr prior to high-speed treadmill exercise in a balanced 3-way cross-over design. Blood samples were collected for determination of furosemide, lactate, hemoglobin, blood gas, and electrolyte concentrations. Heart rate and pulmonary arterial pressure were measured throughout the run and endoscopic examination and bronchoalveolar lavage (BAL) performed. Horses were assigned an EIPH score and the number of red blood cells in BAL fluid determined. Although not significantly different, endoscopic EIPH scores were lower in the 4-hr versus the 24-hr and saline groups. RBC counts were not significantly different between the treatment groups. Pulmonary arterial pressures were significantly increased at higher speeds; however, there were no significant differences between dose groups when controlling for speed. A small sample size and unknown bleeding history warrant a larger-scale study.

High-intensity training in normobaric hypoxia enhances exercise performance and aerobic capacity in Thoroughbred horses: A randomized crossover study.

We examined the effects of high-intensity training in normobaric hypoxia on aerobic capacity and exercise performance in horses and the individual response to normoxic and hypoxic training. Eight untrained horses were studied in a randomized, crossover design after training in hypoxia (HYP; 15.0% inspired O2 ) or normoxia (NOR; 20.9% inspired O2 ) 3 days/week for 4 weeks separated by a 4-month washout period. Before and after each training period, incremental treadmill exercise tests were performed in normoxia. Each training session consisted of 1 min cantering at 7 m/s and 2 min galloping at the speed determined to elicit maximal oxygen consumption ( V˙ O2 max) in normoxia. Hypoxia increased significantly more than NOR in run time to exhaustion (HYP, +28.4%; NOR, +10.4%, p = .001), V˙ O2 max (HYP, +12.1%; NOR, +2.6%, p = .042), cardiac output ( Q˙ ; HYP, +11.3%; NOR, -1.7%, p = .019), and stroke volume (SV) at exhaustion (HYP, +5.4%; NOR, -5.5%, p = .035) after training. No significant correlations were observed between NOR and HYP for individual changes after training in run time (p = .21), V˙ O2 max (p = .99), Q˙ (p = .19), and SV (p = .46) at exhaustion. Arterial O2 saturation during exercise in HYP was positively correlated with the changes in run time (r = .85, p = .0073), Q˙ (r = .72, p = .043) and SV (r = .77, p = .026) of HYP after training, whereas there were no correlations between these parameters in NOR. These results suggest that high-intensity training in normobaric hypoxia improved exercise performance and aerobic capacity of horses to a greater extent than the same training protocol in normoxia, and the severity of hypoxemia during hypoxic exercise might be too stressful for poor responders to hypoxic training.

Measuring V̇O2 in hypoxic and hyperoxic conditions using dynamic gas mixing with a flow-through indirect calorimeter.

Measurements of gas exchange while breathing gases of different O2 concentrations are useful in respiratory and exercise physiology. High bias flows required in flow-through indirect calorimetry systems for large animals like exercising horses necessitate the use of inconveniently large reservoirs of mixed gases for making such measurements and can limit the amount of equilibration time that is adequate for steady-state measurements. We obviated the need to use a pre-mixed reservoir of gas in a semi-open flow-through indirect calorimeter by dynamically mixing gases and verified the theoretical accuracy and utility of making such measurements using the mass-balance N2-dilution method. We evaluated the accuracy of the technique at different inspired oxygen fractions by measuring exercising oxygen consumption (V̇O2) at two fully aerobic submaximal exercise intensities in Thoroughbred horses. Horses exercised at 24% and 50% maximum oxygen consumption (V̇O2 max) of each horse while breathing different O2 concentrations (19.5%, 21% and 25% O2). The N2-dilution technique was used to calculate V̇O2. Repeated-measures ANOVA was used to tested for differences in V̇O2 between different inspired O2 concentrations. The specific V̇O2 of the horses trotting at 24%V̇O2max and cantering at 50%V̇O2max were not significantly different among the three different inspired oxygen fractions. These findings demonstrate that reliable measurements of V̇O2 can be obtained at various inspired oxygen fractions using dynamic gas mixing and the N2-dilution technique to calibrate semi-open-circuit gas flow systems.

Estimating the impact of violent events on transmission in Ebola virus disease outbreak, Democratic Republic of the Congo, 2018-2019.

INTRODUCTION: As of April 2019, the current Ebola virus disease (EVD) outbreak in the Democratic Republic of the Congo (DRC) is occurring in a longstanding conflict zone and has become the second largest EVD outbreak in history. It is suspected that after violent events occur, EVD transmission will increase; however, empirical studies to understand the impact of violence on transmission are lacking. Here, we use spatial and temporal trends of EVD case counts to compare transmission rates between health zones that have versus have not experienced recent violent events during the outbreak. METHODS: We collected daily EVD case counts from DRC Ministry of Health. A time-varying indicator of recent violence in each health zone was derived from events documented in the WHO situation reports. We used the Wallinga-Teunis technique to estimate the reproduction number R for each case by day per zone in the 2018-2019 outbreak. We fit an exponentially decaying curve to estimates of R overall and by health zone, for comparison to past outbreaks. RESULTS: As of 16 April 2019, the mean overall R for the entire outbreak was 1.11. We found evidence of an increase in the estimated transmission rates in health zones with recently reported violent events versus those without (p = 0.008). The average R was estimated as between 0.61 and 0.86 in regions not affected by recent violent events, and between 1.01 and 1.07 in zones affected by violent events within the last 21 days, leading to an increase in R between 0.17 and 0.53. Within zones with recent violent events, the mean estimated quenching rate was lower than for all past outbreaks except the 2013-2016 West African outbreak. CONCLUSION: The difference in the estimated transmission rates between zones affected by recent violent events suggests that violent events are contributing to increased transmission and the ongoing nature of this outbreak.

Genome-Wide Patterns of Gene Expression in a Wild Primate Indicate Species-Specific Mechanisms Associated with Tolerance to Natural Simian Immunodeficiency Virus Infection.

Over 40 species of nonhuman primates host simian immunodeficiency viruses (SIVs). In natural hosts, infection is generally assumed to be nonpathogenic due to a long coevolutionary history between host and virus, although pathogenicity is difficult to study in wild nonhuman primates. We used whole-blood RNA-seq and SIV prevalence from 29 wild Ugandan red colobus (Piliocolobus tephrosceles) to assess the effects of SIV infection on host gene expression in wild, naturally SIV-infected primates. We found no evidence for chronic immune activation in infected individuals, suggesting that SIV is not immunocompromising in this species, in contrast to human immunodeficiency virus in humans. Notably, an immunosuppressive gene, CD101, was upregulated in infected individuals. This gene has not been previously described in the context of nonpathogenic SIV infection. This expands the known variation associated with SIV infection in natural hosts and may suggest a novel mechanism for tolerance of SIV infection in the Ugandan red colobus.

Survival Analysis of Occipital Nerve Stimulator Leads Placed under Fluoroscopic Guidance with and without Ultrasonography.

BACKGROUND: Electrical stimulation of the greater occipital nerves is performed to treat pain secondary to chronic daily headaches and occipital neuralgia. The use of fluoroscopy alone to guide the surgical placement of electrodes near the greater occipital nerves disregards the impact of tissue planes on lead stability and stimulation efficacy. OBJECTIVE: We hypothesized that occipital neurostimulator (ONS) leads placed with ultrasonography combined with fluoroscopy would demonstrate increased survival rates and times when compared to ONS leads placed with fluoroscopy alone. STUDY DESIGN: A 2-arm retrospective chart review. SETTING: A single academic medical center. METHODS: This retrospective chart review analyzed the procedure notes and demographic data of patients who underwent the permanent implant of an ONS lead between July 2012 and August 2015. Patient data included the diagnosis (reason for implant), smoking tobacco use, disability, and age. ONS lead data included the date of permanent implant, the imaging modality used during permanent implant (fluoroscopy with or without ultrasonography), and, if applicable, the date and reason for lead removal. A total of 21 patients (53 leads) were included for the review. Chi-squared tests, Fishers exact tests, 2-sample t-tests, and Wilcoxon rank-sum tests were used to compare fluoroscopy against combined fluoroscopy and ultrasonography as implant methods with respect to patient demographics. These tests were also used to evaluate the primary aim of this study, which was to compare the survival rates and times of ONS leads placed with combined ultrasonography and fluoroscopy versus those placed with fluoroscopy alone. Survival analysis was used to assess the effect of implant method, adjusted for patient demographics (age, smoking tobacco use, and disability), on the risk of lead explant. RESULTS: Data from 21 patients were collected, including a total of 53 ONS leads. There was no statistically significant difference in the lead survival rate or time, disability, or patient age with respect to the implant method with or without ultrasonography. There was a statistically significant negative effect on the risk of explant with regards to lead removal in smoking patients compared to non-smoking patients (hazard ratio 0.36). There was also a statistically significant difference in smoking tobacco use with respect to the implant method, such that a greater number of patients whose leads were placed with combined fluoroscopy and ultrasonography had a history of smoking (P = 0.048). LIMITATIONS: This study is a retrospective chart review that had statistically significant differences in the patient groups and a small sample size. CONCLUSION: This study assessed the survival rates and times of ONS leads placed with ultrasonography and fluoroscopy versus fluoroscopy alone. We did not observe an effect to suggest that the incremental addition of ultrasound guidance to fluoroscopy as the intraoperative imaging modality used during the permanent implant of ONS leads yields statistically significant differences in lead survival rate or time. Medical comorbidities, including age and smoking status, may play a role in determining the risk of surgical revision and should be considered in future studies. KEY WORDS: Neuromodulation, peripheral nerve stimulation, occipital nerve stimulation, occipital neuralgia, chronic daily headaches, ultrasonography.

Changes in heart rate and heart rate variability as a function of age in Thoroughbred horses.

We investigated changes in heart rate (HR) and HR variability as a function of age in newborn foals to old Thoroughbred horses. Experiments were performed on a total of 83 healthy and clinically normal Thoroughbred horses. Resting HR decreased with age from birth. The relationship between age and HR fit the equation Y=48.2X-0.129(R2=0.705); the relationship between age and HR for horses 0-7 years old fit the equation Y=44.1X-0.179(R2=0.882). Seven-day-old horses had the highest HR values (106 ± 10.3 beat/min). The low frequency (LF) and high frequency (HF) powers increased with age in newborn to old horses. These changes in HR and HR variability appear to result from the effects of ageing. Three- to seven-year-old race horses had the lowest HR values (32.9 ± 3.5 beat/min) and the highest LF and HF powers except for the HF powers in the oldest horses. Race training may have contributed to these changes. Horses of ages greater than 25 years old had the highest HF powers and the lowest LF/HF ratios. In individual horses, 8 of the 15 horses over 25 years old had LF/HF ratios of less than 1.0; their HR variability appears to be unique, and they may have a different autonomic balance than horses of younger age.

Ventilatory response to carbon monoxide during exercise in hypoxia and hypercapnia.

We tested if the addition of CO to inspired gases with different inspired O2 and CO2 fractions (FIO2 and FICO2) stimulates ventilation at rest or during submaximal exercise. We measured minute ventilation (VE) in goats breathing combinations of FIO2 ranging from 0.21 to 0.06 and FICO2 from 0 to 0.05, both with and without inspired CO resulting in carboxyhemoglobin fractions (FHbCO) of 0.02 (no CO added), 0.15, or 0.45. We did this while they stood on a treadmill, walked at 1.4, or trotted at 2.5ms-1. Hypoxia, hypercapnia, and exercise, alone and in combination, increased ventilation compared to breathing air at rest. Both elevated FHbCO increased VE compared with ambient FHbCO during exercise (increases of 1.50 and 5.53mls-1kg-1 for FHbCO 0.15 and 0.45, respectively; P=0.035), but not at rest (P=0.958), when the ventilatory effects of FIO2 and FICO2 are factored out. Additionally, FHbCO 0.45 (but not 0.15) increased VE compared to FHbCO 0.02 for all FIO2 and FICO2 when the ventilatory effects of exercise are factored out. Taken together, these data suggest that exercise intensity and FHbCO dose interact to stimulate ventilation during exercise.

Hypoxic training increases maximal oxygen consumption in Thoroughbred horses well-trained in normoxia.

Hypoxic training is effective for improving athletic performance in humans. It increases maximal oxygen consumption (V̇O2max) more than normoxic training in untrained horses. However, the effects of hypoxic training on well-trained horses are unclear. We measured the effects of hypoxic training on V̇O2max of 5 well-trained horses in which V̇O2max had not increased over 3 consecutive weeks of supramaximal treadmill training in normoxia which was performed twice a week. The horses trained with hypoxia (15% inspired O2) twice a week. Cardiorespiratory valuables were analyzed with analysis of variance between before and after 3 weeks of hypoxic training. Mass-specific V̇O2max increased after 3 weeks of hypoxic training (178 ± 10 vs. 194 ± 12.3 ml O2 (STPD)/(kg × min), P<0.05) even though all-out training in normoxia had not increased V̇O2max. Absolute V̇O2max also increased after hypoxic training (86.6 ± 6.2 vs. 93.6 ± 6.6 l O2 (STPD)/min, P<0.05). Total running distance after hypoxic training increased 12% compared to that before hypoxic training; however, the difference was not significant. There were no significant differences between pre- and post-hypoxic training for end-run plasma lactate concentrations or packed cell volumes. Hypoxic training may increase V̇O2max even though it is not increased by normoxic training in well-trained horses, at least for the durations of time evaluated in this study. Training while breathing hypoxic gas may have the potential to enhance normoxic performance of Thoroughbred horses.

Recruitment, Methods, and Descriptive Results of a Physiologic Assessment of Latino Farmworkers: The California Heat Illness Prevention Study.

OBJECTIVE: The California heat illness prevention study (CHIPS) devised methodology and collected physiological data to assess heat related illness (HRI) risk in Latino farmworkers. METHODS: Bilingual researchers monitored HRI across a workshift, recording core temperature, work rate (metabolic equivalents [METs]), and heart rate at minute intervals. Hydration status was assessed by changes in weight and blood osmolality. Personal data loggers and a weather station measured exposure to heat. Interviewer administered questionnaires were used to collect demographic and occupational information. RESULTS: California farmworkers (n = 588) were assessed. Acceptable quality data was obtained from 80% of participants (core temperature) to 100% of participants (weight change). Workers (8.3%) experienced a core body temperature more than or equal to 38.5 °C and 11.8% experienced dehydration (lost more than 1.5% of body weight). CONCLUSIONS: Methodology is presented for the first comprehensive physiological assessment of HRI risk in California farmworkers.

Contact structure, mobility, environmental impact and behaviour: the importance of social forces to infectious disease dynamics and disease ecology.

Human factors, including contact structure, movement, impact on the environment and patterns of behaviour, can have significant influence on the emergence of novel infectious diseases and the transmission and amplification of established ones. As anthropogenic climate change alters natural systems and global economic forces drive land-use and land-cover change, it becomes increasingly important to understand both the ecological and social factors that impact infectious disease outcomes for human populations. While the field of disease ecology explicitly studies the ecological aspects of infectious disease transmission, the effects of the social context on zoonotic pathogen spillover and subsequent human-to-human transmission are comparatively neglected in the literature. The social sciences encompass a variety of disciplines and frameworks for understanding infectious diseases; however, here we focus on four primary areas of social systems that quantitatively and qualitatively contribute to infectious diseases as social-ecological systems. These areas are social mixing and structure, space and mobility, geography and environmental impact, and behaviour and behaviour change. Incorporation of these social factors requires empirical studies for parametrization, phenomena characterization and integrated theoretical modelling of social-ecological interactions. The social-ecological system that dictates infectious disease dynamics is a complex system rich in interacting variables with dynamically significant heterogeneous properties. Future discussions about infectious disease spillover and transmission in human populations need to address the social context that affects particular disease systems by identifying and measuring qualitatively important drivers.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.

Effects of maintaining different exercise intensities during detraining on aerobic capacity in Thoroughbreds.

OBJECTIVE To determine whether racehorses undergoing regular exercise at 2 intensities or stall rest during a period of reduced training (detraining) would differentially maintain their cardiopulmonary and oxygen-transport capacities. ANIMALS 27 Thoroughbreds. PROCEDURES Horses trained on a treadmill for 18 weeks underwent a period of detraining for 12 weeks according to 1 of 3 protocols: cantering at 70% of maximal rate of oxygen consumption ([Formula: see text]o2max) for 3 min/d for 5 d/wk (canter group); walking for 1 h/d for 5 d/wk (walk group); or stall rest (stall group). Standardized treadmill exercise protocols (during which cardiopulmonary and oxygen-transport variables were measured) were performed before and after detraining. RESULTS Mass-specific [Formula: see text]o2max, maximal cardiac output, and maximal cardiac stroke volume of all groups decreased after 12 weeks of detraining with no differences among groups. After detraining, arterial-mixed-venous oxygen concentration difference did not decrease in any group, and maximal heart rate decreased in the walk and stall groups. Run time to exhaustion and speeds eliciting [Formula: see text]o2max and maximal heart rate and at which plasma lactate concentration reached 4mM did not change in the canter group but decreased in the walk and stall groups. CONCLUSIONS AND CLINICAL RELEVANCE Horses following the cantering detraining protocol maintained higher values of several performance variables compared with horses following the walking or stall rest protocols. These results suggested that it may be possible to identify a minimal threshold exercise intensity or protocol during detraining that would promote maintenance of important performance-related variables and minimize reductions in oxygen-transport capacity in horses.