Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 166
Filtrar
2.
J Dairy Sci ; 103(5): 4822-4837, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32113780

RESUMO

Prenatal heat stress during late gestation exerts long-term effects on growth and productivity of the dairy calf. Further, direct exposure to heat stress during the preweaning period impairs calf thermoregulation and performance. We examined the effects of heat stress abatement during the prenatal period, postnatal period, or both on calf performance. We hypothesized that calves exposed to pre- and postnatal heat stress abatement would perform most optimally in terms of thermoregulation, growth, and health responses when compared with calves that are heat-stressed at any time in the pre- or postnatal periods. Holstein calves born to heat-stressed (HT) or cooled (CL) dams during late gestation (44 ± 5 d; prenatal HT or CL) were exposed to heat stress or cooling postnatally for 56 d (postnatal HT or CL), resulting in 4 treatments: HT-HT, HT-CL, CL-HT, and CL-CL; n = 12/treatment. Calves were administered 4 L of pooled colostrum and after 2 d of age allotted 10 L/d milk replacer and up to 3 kg/d concentrate in automatic feeder group pens (n = 6/pen). Postnatal cooling was achieved by 2 fans (average wind speed 2 m/s). Thermoregulatory responses (respiration rate and heart rate; rectal, body, and skin temperature), feed intake, growth parameters including average daily gain and medication events were recorded, and blood samples were collected weekly. Thermoregulatory responses were lower in postnatal CL calves compared with postnatal HT. In the afternoon, HT-HT calves had the highest respiration rate and rectal temperature, HT-CL calves had the lowest respiration rate, and CL-HT calves had the lowest heart rate compared with the other treatment groups. Prenatal CL calves weighed more at birth and weaning with a tendency for greater average daily gain compared with prenatal HT calves, whereas postnatal CL calves had increased milk replacer and concentrate intake and a tendency for reduced fever, infection, and total medication events relative to postnatal HT. Prenatal HT calves were esophageal tube fed more often than prenatal CL. Blood hematocrit and 24-h serum IgG concentration were greater in prenatal CL calves relative to prenatal HT. Prenatal heat stress abatement improves weight gain, hematocrit, and immunoglobulin transfer, whereas postnatal heat stress abatement modulates thermoregulatory responses, feed intake, and calf health. This study is the first to characterize the combined effects of pre- and postnatal heat stress or active cooling on the dairy calf.


Assuntos
Regulação da Temperatura Corporal , Doenças dos Bovinos/terapia , Transtornos de Estresse por Calor/veterinária , Animais , Bovinos , Doenças dos Bovinos/fisiopatologia , Temperatura Baixa , Colostro , Dieta/veterinária , Feminino , Transtornos de Estresse por Calor/terapia , Temperatura Alta , Leite , Gravidez , Complicações na Gravidez/terapia , Complicações na Gravidez/veterinária , Desmame , Ganho de Peso
3.
Curr Sports Med Rep ; 19(2): 70-75, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32028351

RESUMO

Tactical athletes are individuals in service occupations with significant physical fitness and performance requirements such as law enforcement, firefighters, emergency responders, and military service members. Tactical athletes also may have specific administrative requirements related to documenting physical injuries. Musculoskeletal injuries are a large burden on the tactical athlete population, with incident rates varying based on the specific profession. Chronic exertional compartment syndrome (CECS) is difficult to manage in the tactical athlete population due to their limited ability to reduce impact activities and poor surgical outcomes. Botulinum neurotoxin-A and gait retraining show promise as alternative treatments for CECS. Heat injuries are frequent in the tactical athlete populations, and a graduated return to play process helps to prevent morbidity. Management of musculoskeletal injuries in tactical athletes requires consideration of operational schedules and adequate reconditioning, in addition to traditional injury evaluation.


Assuntos
Atletas , Socorristas , Militares , Doenças Musculoesqueléticas/epidemiologia , Traumatismos Ocupacionais/epidemiologia , Síndromes Compartimentais/terapia , Transtornos de Estresse por Calor/terapia , Humanos , Sistema Musculoesquelético/lesões , Saúde do Trabalhador , Desempenho Físico Funcional , Medicina Esportiva
5.
J Therm Biol ; 87: 102478, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31999606

RESUMO

BACKGROUND: A recent review article on an aromatherapeutic inhaler demonstrated clinical effects on a number of bodily systems, like the cardiovascular system, the respiratory system, the nervous system and the endocrine system. OBJECTIVE: This paper extends these findings and investigates whether specially designed essential oils inhalers are capable to counter experimentally induced stressful heat sensations. METHOD: Two prospective, randomized, controlled experiments using the Hot Immersion Test Paradigm (HIT) were conducted to investigate whether deep odor inhalations increase heat tolerance. RESULTS: In both experiments, the inhaler strongly prolonged pain tolerance and increased blood oxygenation (1 < d < 1.3). In the second experiment, the inhaler also increased heart rate variability (d = 1.3) as a mechanism to cope with heat stress. CONCLUSION: The ability to resist a stressful thermal stimulus can be exogenously improved by short and deep inhalations of essential scents directly delivered to the olfactory system.


Assuntos
Aromaterapia/métodos , Transtornos de Estresse por Calor/prevenção & controle , Óleos Voláteis/farmacologia , Termotolerância/efeitos dos fármacos , Administração por Inalação , Adulto , Feminino , Frequência Cardíaca , Transtornos de Estresse por Calor/terapia , Humanos , Imersão , Masculino , Pessoa de Meia-Idade , Nebulizadores e Vaporizadores , Óleos Voláteis/administração & dosagem , Oxigênio/sangue
6.
Br J Sports Med ; 54(16): 1003-1007, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31992546

RESUMO

PURPOSE: Assess the health status and heat preparation strategies of athletes competing in a World Cycling Championships held in hot ambient conditions (37°C, 25% relative humidity, wet-bulb-globe-temperature 27°C) and monitor the medical events arising during competition. METHODS: 69 cyclists (~9% of the world championships participants) completed a pre-competition questionnaire. Illnesses and injuries encountered by the Athlete Medical Centre (AMC) were extracted from the race reports. RESULTS: 22% of respondents reported illness symptoms in the 10 days preceding the Championships. 57% of respondents had previously experienced heat-related symptoms (cramping most commonly) while 17% had previously been diagnosed with exertional heat illness. 61% of the respondents had undergone some form of heat exposure prior to the Championships, with 38% acclimating for 5 to 30 days. In addition, several respondents declared to live in warm countries and all arrived in Qatar ~5 days prior to their event. 96% of the respondents used a pre-cooling strategy for the time trials and 74% did so before the road race (p<0.001), with ice vests being the most common. The AMC assessed 46 injuries and 26 illnesses in total, with three cyclists diagnosed with heat exhaustion. CONCLUSIONS: The prevalence of previous heat illness in elite cyclists calls for team and event organisation doctors to be trained on heat illness management, including early diagnosis and rapid on-site cooling. Some cyclists had been exposed to the heat prior to the Championships, but few had a dedicated plan, calling for additional education on the importance of heat acclimation. Pre-cooling was widely adopted.


Assuntos
Aclimatação , Ciclismo/fisiologia , Comportamento Competitivo/fisiologia , Nível de Saúde , Transtornos de Estresse por Calor/epidemiologia , Temperatura Alta , Aniversários e Eventos Especiais , Ciclismo/lesões , Feminino , Hidratação , Exaustão por Calor/diagnóstico , Exaustão por Calor/epidemiologia , Exaustão por Calor/terapia , Transtornos de Estresse por Calor/diagnóstico , Transtornos de Estresse por Calor/terapia , Humanos , Masculino , Catar , Adulto Jovem
7.
Med Sci Sports Exerc ; 52(2): 362-369, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31469711

RESUMO

PURPOSE: Sweat-induced fluid loss during prolonged exercise-heat stress can compromise cardiovascular and thermoregulatory function, although its effects on cardiac autonomic modulation remain unclear. We therefore examined heart rate variability (HRV) and recovery (HRRec), as surrogates of cardiac autonomic modulation, during and after prolonged exercise in the heat with and without fluid replacement. METHODS: Eleven young and healthy men performed 90 min of semi-recumbent cycling in dry heat (40°C; 20% relative humidity) at a fixed rate of metabolic heat production (600 W; ~46% V˙O2peak) followed by 40-min resting recovery without fluid replacement (No-FR; ~3.4% reduction in body mass). On a separate day, participants completed the same protocol with fluid replacement (FR; 500-700 mL timed boluses) to offset sweat losses. Esophageal temperature and ECG were recorded throughout, with measurements analyzed over 10-min averaged epochs during baseline, each 30-min interval during exercise and 20-min interval during recovery. RESULTS: Esophageal temperature and heart rate were elevated in No-FR relative to FR throughout exercise (all P ≤ 0.02). The HRV indices reflecting vagal influence of heart rate including the cardiac vagal index (CVI = log10[16 × SD1 × SD2]) and root-mean-square of successive differences were attenuated throughout exercise relative to baseline in both conditions (all P < 0.05), with the magnitude of the reduction greater in the No-FR condition (all P < 0.05). Further, sample entropy was reduced throughout all time points measured during exercise in the No-FR relative to FR condition (all P ≤ 0.03). CONCLUSIONS: Our unique observations indicate that while prolonged exercise heat stress attenuates the vagal influence and complexity of cardiac rhythms, that reduction is further exacerbated by fluid loss, highlighting the importance of fluid replacement in such conditions.


Assuntos
Exercício Físico/fisiologia , Frequência Cardíaca/fisiologia , Transtornos de Estresse por Calor/fisiopatologia , Sudorese/fisiologia , Nervo Vago/fisiopatologia , Adulto , Pressão Sanguínea/fisiologia , Temperatura Corporal/fisiologia , Eletrocardiografia , Hidratação , Transtornos de Estresse por Calor/terapia , Temperatura Alta , Humanos , Masculino , Fatores de Tempo
8.
Dtsch Arztebl Int ; 116(31-32): 537-544, 2019 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-31554541

RESUMO

BACKGROUND: With climate change, heat waves are expected to become more frequent in the near future. Already, on average more than 25 000 "heat deaths" are estimated to occur in Europe every year. However, heat stress and heat illnesses arise not just when ambient temperatures are high. Physical exertion increases heat production within the organism many times over; if not enough heat is lost, there is a risk of exertional heat stress. This review article discusses contributing factors, at-risk groups, and the diagnosis and treatment of heat illnesses. METHODS: A selective literature search was carried out on PubMed. Current guidelines and expert recommendations were also included. RESULTS: Apart from muscular heat production (>70% of converted energy), there are other factors that singly or in combination can give rise to heat stress: clothing, climate/acclimatization, and individual factors. Through its insulating properties, clothing reduces the evaporation of sweat (the most effective physiological cooling mechanism). A sudden heat wave, or changing the climate zone (as with air travel), increases the risk of a heat-related health event. Overweight, low fitness level, acute infections, illness, dehydration, and other factors also reduce heat tolerance. In addition to children, older people are particularly at risk because of their reduced physiological adaptability, (multi-)morbidity, and intake of prescription drugs. A heat illness can progress suddenly to life-threatening heat stroke. Successful treatment depends on rapid diagnosis and cooling the body down as quickly as possible. The aim is to reduce core body temperature to <40 °C within 30 minutes. CONCLUSION: Immediately effective cooling interventions are the only causal treatment for heat stroke. Time once lost cannot be made up. Prevention (acclimatization, reduced exposure, etc.) and terminating the heat stress in good time (e.g., stopping work) are better than any cure.


Assuntos
Transtornos de Estresse por Calor/epidemiologia , Transtornos de Estresse por Calor/terapia , Mudança Climática , Europa (Continente)/epidemiologia , Humanos , Esforço Físico/fisiologia , Fatores de Risco
9.
J Dairy Sci ; 102(12): 10695-10710, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31521355

RESUMO

Impaired fertility during periods of heat stress is the culmination of numerous physiological responses to heat stress, ranging from reduced estrus expression and altered follicular function to early embryonic death. Furthermore, heat-stressed dairy cattle exhibit a unique metabolic status that likely contributes to the observed reduction in fertility. An understanding of this unique physiological response can be used as a basis for improving cow management strategies, thereby reducing the negative effects of heat stress on reproduction. Potential opportunities for improving the management of dairy cattle during heat stress vary greatly and include feed additives, targeted cooling, genetic selection, embryo transfer and, potentially, crossbreeding. Previous studies indicate that dietary interventions such as melatonin and chromium supplementation could alleviate some of the detrimental effects of heat stress on fertility, and that factors involved in the methionine cycle would likely do the same. These supplements, particularly chromium, may improve reproductive performance during heat stress by alleviating insulin-mediated damage to the follicle and its enclosed cumulus-oocyte complex. Beyond feed additives, some of the simplest, yet most effective strategies involve altering the timing of feeding and cooling to take advantage of comparatively low nighttime temperatures. Likewise, expansion of cooling systems to include breeding-age heifers and dry cows has significant benefits for dams and their offspring. More complicated but promising strategies involve the calculation of breeding values for thermotolerance, the identification of genomic markers for heat tolerance, and the development of bedding-based conductive cooling systems. Unfortunately, no single approach can completely rescue the fertility of lactating dairy cows during heat stress. That said, region-appropriate combinations of strategies can improve reproductive measures to reasonable levels.


Assuntos
Doenças dos Bovinos/fisiopatologia , Transtornos de Estresse por Calor/veterinária , Reprodução , Ração Animal , Animais , Bovinos , Doenças dos Bovinos/terapia , Suplementos Nutricionais , Feminino , Fertilidade , Transtornos de Estresse por Calor/terapia , Lactação , Reprodução/fisiologia
10.
Wilderness Environ Med ; 30(4S): S33-S46, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31221601

RESUMO

The Wilderness Medical Society convened an expert panel in 2011 to develop a set of evidence-based guidelines for the recognition, prevention, and treatment of heat illness. We present a review of the classifications, pathophysiology, and evidence-based guidelines for planning and preventive measures, as well as best practice recommendations for both field- and hospital-based therapeutic management of heat illness. These recommendations are graded based on the quality of supporting evidence and balance the benefits and risks or burdens for each modality. This is an updated version of the original Wilderness Medical Society Practice Guidelines for the Treatment and Prevention of Heat-Related Illness published in 2013.


Assuntos
Transtornos de Estresse por Calor/prevenção & controle , Padrões de Prática Médica , Medicina Selvagem/normas , Transtornos de Estresse por Calor/classificação , Transtornos de Estresse por Calor/fisiopatologia , Transtornos de Estresse por Calor/terapia , Humanos , Sociedades Médicas , Medicina Selvagem/métodos
11.
Artigo em Alemão | MEDLINE | ID: mdl-30997525

RESUMO

The number of heatwaves is going to increase due to climate change and will pose a high health risk especially for elderly people. Additional risk factors like immobility, the need for care, chronic and acute diseases (worsening of symptoms), and the intake of medications lead to an increased sensitivity to heat in this particular age group. Nursing staff and medical assistants working in general practices are two important professions to reach the risk group during heatwaves and provide preventive and curative care.The "Klinikum der Universität München" has developed an interprofessional blended-learning program to sensitize for this topic and to enable those two professional groups to react adequately to heat events. It combines independent learning with the help of online videos and presentations and a face-to-face component for the practical application of knowledge through examples. The concept, the results, as well as the conclusion of the project, which completed in October 2018, are presented in this article.Educational programs are part of the adaption strategies to heat events. The "Recommendations for the creation of Heat Action Plans for the Protection of Human Health" state that advanced trainings and education of healthcare and social workers help to communicate relevant content to adequately act during heat periods. The developed educational program fulfills this demand.To enable the widest possible use, the training materials are available free of charge and can be downloaded from www.klimawandelundbildung.de .


Assuntos
Mudança Climática , Pessoal de Saúde/educação , Transtornos de Estresse por Calor/terapia , Temperatura Alta , Idoso , Assistência Ambulatorial , Assistência à Saúde , Alemanha , Humanos , Enfermagem
13.
J Athl Train ; 54(2): 133-141, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30517023

RESUMO

CONTEXT: Schools that sponsor athletic programs have an obligation to provide a safe environment with appropriate policies for addressing emergencies. OBJECTIVE: To describe the emergency preparedness of secondary schools in Arizona specific to emergency action plans (EAPs), cardiac arrest, concussion, and heat illness. DESIGN: Cross-sectional study. SETTING: Online survey. PATIENTS OR OTHER PARTICIPANTS: Athletic directors from 143 Arizona secondary schools (response rate = 54%). INTERVENTION(S): A 6-section survey that included questions related to athletic trainer (AT) access, EAPs, automated external defibrillators (AEDs), concussion, heat illness, and other policies. MAIN OUTCOME MEASURE(S): Descriptive statistics were reported. Comparisons of responses between schools with and without AT access were conducted with Mann-Whitney U tests. RESULTS: Most respondents (81%, n = 116) indicated their school had access to an AT, and 95% (n = 125) of respondents reported their school had a written EAP. The AEDs were available at most (93%, n = 121) schools. All respondents were familiar with the interscholastic concussion policy, and 98% (n = 123) indicated they had a school-specific policy. Almost all respondents (99%, n = 121) reported being familiar with the state heat-illness policy. Environmental measures were taken before practices at 48% (n = 60) of schools. Schools with access to an AT were more likely to have an EAP, venue-specific EAPs, physician approval of EAPs, AEDs, heat-illness policies, and cold-water immersion tubs and to take environmental measures. CONCLUSIONS: Whereas the majority of schools reported AT access, not all schools had adequate EAPs in place. Schools would benefit from educational opportunities regarding best practices and policy development to improve emergency preparedness.


Assuntos
Serviços Médicos de Emergência/organização & administração , Instituições Acadêmicas/organização & administração , Esportes , Arizona , Concussão Encefálica/diagnóstico , Concussão Encefálica/terapia , Estudos Transversais , Desfibriladores , Parada Cardíaca/diagnóstico , Parada Cardíaca/terapia , Transtornos de Estresse por Calor/diagnóstico , Transtornos de Estresse por Calor/terapia , Humanos , Inquéritos e Questionários
14.
J Sport Rehabil ; 28(5): 522-525, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29809089

RESUMO

Clinical Scenario: Exertional heat stroke (EHS) is a medical emergency characterized by body core temperatures >40.5°C and central nervous system dysfunction. An EHS diagnosis should be immediately followed by cold-water immersion (CWI). Ideally, EHS victims cool at a rate >0.15°C/min until their temperature reaches 38.9°C. While generally accepted, these EHS treatment recommendations often stem from research that examined only males. Since gender differences exist in anthropomorphics (eg, body surface area, lean body mass) and anthropomorphics impact CWI cooling rates, it is possible that CWI cooling rates may differ between genders. Clinical Question: Do CWI rectal temperature (Trec) cooling rates differ between hyperthermic males and females? Summary of Findings: The average Trec cooling rate across all examined studies for males and females was 0.18 (0.05) and 0.24 (0.03)°C/min, respectively. Hyperthermic females cooled ∼33% faster than males. Clinical Bottom Line: Hyperthermic females cooled faster than males, most likely because of higher body surface area to mass ratios and less lean body mass. Regardless of gender, CWI is highly effective at lowering Trec. Clinicians must be able to treat all EHS victims, regardless of gender, with CWI, given its high survival rate when implemented appropriately. Strength of Recommendation: Moderate evidence (2 level 3 studies) suggests that females cool faster than males when treated with CWI following severe hyperthermia. Despite gender differences, cooling rates exceeded cooling rate recommendations for EHS victims (ie, 0.15°C/min).


Assuntos
Atletas , Temperatura Corporal/fisiologia , Temperatura Baixa , Transtornos de Estresse por Calor/terapia , Imersão , Feminino , Humanos , Masculino , Reto , Fatores Sexuais
15.
J Athl Train ; 53(12): 1200-1205, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30562055

RESUMO

CONTEXT: Treatment delays can be contributing factors in the deaths of American football athletes from exertional heat stroke. Ideally, clinicians begin cold-water immersion (CWI) to reduce rectal temperature (Trec) to <38.9°C within 30 minutes of collapse. If delays occur, experts recommend Trec cooling rates that exceed 0.15°C/min. Whether treatment delays affect CWI cooling rates or perceptual variables when football uniforms are worn is unknown. OBJECTIVE: To answer 3 questions: (1) Does wearing a football uniform and delaying CWI by 5 minutes or 30 minutes affect Trec cooling rates? (2) Do Trec cooling rates exceed 0.15°C/min when treatment delays have occurred and individuals wear football uniforms during CWI? (3) How do treatment delays affect thermal sensation and Environmental Symptoms Questionnaire responses? DESIGN: Crossover study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Ten physically active men (age = 22 ± 2 y, height = 183.0 ± 6.9 cm, mass = 78.9 ± 6.0 kg). INTERVENTION(S): On 2 days, participants wore American football uniforms and exercised in the heat until Trec was 39.75°C. Then they sat in the heat, with equipment on, for either 5 or 30 minutes before undergoing CWI (10.6°C ± 0.1°C) until Trec reached 37.75°C. MAIN OUTCOME MEASURE(S): Rectal temperature and CWI duration were used to calculate cooling rates. Thermal sensation was measured pre-exercise, postexercise, postdelay, and post-CWI. Responses to the Environmental Symptoms Questionnaire were obtained pre-exercise, postdelay, and post-CWI. RESULTS: The Trec cooling rates exceeded recommendations and were unaffected by treatment delays (5-minute delay = 0.20°C/min ± 0.07°C/min, 30-minute delay = 0.19°C/min ± 0.05°C/min; P = .4). Thermal sensation differed between conditions only postdelay (5-minute delay = 6.5 ± 0.6, 30-minute delay = 5.5 ± 0.7; P < .05). Environmental Symptoms Questionnaire responses differed between conditions only postdelay (5-minute delay = 27 ± 15, 30-minute delay = 16 ± 12; P < .05). CONCLUSIONS: Treatment delays and football equipment did not impair CWI's effectiveness. Because participants felt cooler and better after the 30-minute delay despite still having elevated Trec, clinicians should use objective measurements (eg, Trec) to guide their decision making for patients with possible exertional heat stroke.


Assuntos
Temperatura Corporal , Vestuário , Transtornos de Estresse por Calor/terapia , Imersão , Adulto , Atletas , Temperatura Baixa , Estudos Cross-Over , Exercício Físico/fisiologia , Feminino , Futebol Americano/fisiologia , Golpe de Calor/terapia , Temperatura Alta , Humanos , Hipertermia Induzida , Masculino , Sensação Térmica , Estados Unidos , Água , Adulto Jovem
16.
Artigo em Inglês | MEDLINE | ID: mdl-30481241

RESUMO

Soccer requires significant physical conditioning and endurance, as well as the physicality required for contact play. In order to keep athletes safe, it is important that coaches, medical staff, and the players themselves are educated on the most common dangers to their health that they may encounter on a soccer pitch. This article aims to review the current literature and recommendations on concussion, cardiovascular considerations, and heat-related illness as they relate to competitive soccer, with a goal of educating all those who help to keep athletes healthy and competing to their full potential.


Assuntos
Traumatismos em Atletas/prevenção & controle , Concussão Encefálica , Doenças Cardiovasculares , Transtornos de Estresse por Calor , Futebol/lesões , Traumatismos em Atletas/diagnóstico , Traumatismos em Atletas/terapia , Concussão Encefálica/complicações , Concussão Encefálica/diagnóstico , Concussão Encefálica/prevenção & controle , Concussão Encefálica/terapia , Doenças Cardiovasculares/diagnóstico , Doenças Cardiovasculares/prevenção & controle , Doenças Cardiovasculares/terapia , Promoção da Saúde , Transtornos de Estresse por Calor/diagnóstico , Transtornos de Estresse por Calor/prevenção & controle , Transtornos de Estresse por Calor/terapia , Temperatura Alta/efeitos adversos , Humanos
17.
PLoS One ; 13(11): e0206872, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30403743

RESUMO

Establishing appropriate heatwave thresholds is important in reducing adverse human health consequences as it enables a more effective heatwave warning system and response plan. This paper defined such thresholds by focusing on the non-linear relationship between heatwave outcomes and meteorological variables as part of an inductive approach. Daily data on emergency department visitors who were diagnosed with heat illnesses and information on 19 meteorological variables were obtained for the years 2011 to 2016 from relevant government agencies. A Multivariate Adaptive Regression Splines (MARS) analysis was performed to explore points (referred to as "knots") where the behaviour of the variables rapidly changed. For all emergency department visitors, two thresholds (a maximum daily temperature ≥ 32.58°C for 2 consecutive days and a heat index ≥ 79.64) were selected based on the dramatic rise of morbidity at these points. Nonetheless, visitors, who included children and outside workers diagnosed in the early summer season, were reported as being sensitive to heatwaves at lower thresholds. The average daytime temperature (from noon to 6 PM) was determined to represent an alternative threshold for heatwaves. The findings have implications for exploring complex heatwave-morbidity relationships and for developing appropriate intervention strategies to prevent and mitigate the health impact of heatwaves.


Assuntos
Calor Extremo/efeitos adversos , Transtornos de Estresse por Calor/prevenção & controle , Meteorologia/métodos , Aprendizado de Máquina Supervisionado , Adolescente , Adulto , Idoso , Serviço Hospitalar de Emergência/estatística & dados numéricos , Transtornos de Estresse por Calor/epidemiologia , Transtornos de Estresse por Calor/etiologia , Transtornos de Estresse por Calor/terapia , Hospitalização/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade , Estações do Ano , Adulto Jovem
18.
Exp Physiol ; 103(9): 1243-1250, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29947436

RESUMO

NEW FINDINGS: What is the central question of this study? Does inspiratory resistance breathing improve tolerance to simulated haemorrhage in individuals with elevated internal temperatures? What is the main finding and its importance? The main finding of this study is that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress. These findings demonstrate a scenario in which exploitation of the respiratory pump can ameliorate serious conditions related to systemic hypotension. ABSTRACT: Heat exposure impairs human blood pressure control and markedly reduces tolerance to a simulated haemorrhagic challenge. Inspiratory resistance breathing enhances blood pressure control and improves tolerance during simulated haemorrhage in normothermic individuals. However, it is unknown whether similar improvements occur with this manoeuvre in heat stress conditions. In this study, we tested the hypothesis that inspiratory resistance breathing improves tolerance to simulated haemorrhage in individuals with elevated internal temperatures. On two separate days, eight subjects performed a simulated haemorrhage challenge [lower-body negative pressure (LBNP)] to presyncope after an increase in internal temperature of 1.3 ± 0.1°C. During one trial, subjects breathed through an inspiratory impedance device set at 0 cmH2 O of resistance (Sham), whereas on a subsequent day the device was set at -7 cmH2 O of resistance (ITD). Tolerance was quantified as the cumulative stress index. Subjects were more tolerant to the LBNP challenge during the ITD protocol, as indicated by a > 30% larger cumulative stress index (Sham, 520 ± 306 mmHg min; ITD, 682 ± 324 mmHg min; P < 0.01). These data indicate that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress.


Assuntos
Transtornos de Estresse por Calor/terapia , Hemorragia/terapia , Respiração com Pressão Positiva Intermitente/métodos , Adulto , Resistência das Vias Respiratórias , Pressão Sanguínea , Temperatura Corporal , Circulação Cerebrovascular , Feminino , Febre/fisiopatologia , Febre/terapia , Transtornos de Estresse por Calor/complicações , Transtornos de Estresse por Calor/fisiopatologia , Hemodinâmica , Hemorragia/complicações , Hemorragia/fisiopatologia , Humanos , Pressão Negativa da Região Corporal Inferior , Masculino , Taxa Respiratória , Síncope/etiologia , Síncope/fisiopatologia
19.
Vet Clin North Am Food Anim Pract ; 34(2): 325-339, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29935720

RESUMO

Feedlot cattle consuming large amounts of feed and gaining weight rapidly generate significant amounts of metabolic heat. In summer, failure to dissipate this heat leads to heat accumulation and heat stress. Respiratory rates, panting scores, and behavioral changes are useful indicators of heat stress in cattle. Ceasing cattle movement, providing supplementary water tanks in the pens, cooling the pen surface, and manipulation of nutrition and feeding management should be considered to mitigate the risk and manage a heat stress crisis. Removing manure from the pens and provisions of shade has been found to be beneficial for cattle exposed to hot climates.


Assuntos
Doenças dos Bovinos/diagnóstico , Doenças dos Bovinos/terapia , Transtornos de Estresse por Calor/veterinária , Animais , Bovinos , Doenças dos Bovinos/etiologia , Doenças dos Bovinos/prevenção & controle , Transtornos de Estresse por Calor/diagnóstico , Transtornos de Estresse por Calor/terapia , Temperatura Alta , Estações do Ano , Abastecimento de Água
20.
J Dairy Sci ; 101(9): 8269-8283, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29935820

RESUMO

This study determined the effectiveness of convective cooling at different times of day when air temperature (Ta) was cycled from day to night. Mid-lactation Holstein cows (n = 12) were placed in 3 environmental chambers (4 cows per chamber) and acclimated to Ta 19.9°C (thermoneutral; TN) for 7 d followed by an incremental increase over 3 d to a heat stress (HS) condition. Conditions were maintained for 11 d at high and low daily Ta of 33 and 23°C, respectively. To determine adaptive HS response, the HS period was divided into early (E: d 11 to 14) and late (L: d 17 to 20) periods. During HS, cows were exposed to continuous fan (convective) cooling (CC), 8-h day fan cooling (1100 to 1900 h; DC), or 8-h night fan cooling (2300 to 0700 h; NC). Compared with DC, the NC treatment maximized the thermal gradient during the convective cooling. Each animal received all treatments within 3 trials using a repeated 3 × 3 Latin square design. Cows were fed a total mixed ration and milked twice daily. Thermal status was assessed by using thermal conductance and average daily values for mean, minimum, and maximum rectal temperature (Tre), skin temperatures, and respiration rate. Percent reduction in dry matter intake from TN to HS was less for CC than DC and NC, with no change from E to L periods. The DC group exhibited the greatest trend for a percent reduction in total milk yield below CC due to the significantly lower morning milk production. All values for total daily milk production decreased from E to L periods, with E to L reductions in both morning and afternoon milk production. Minimum Tre for CC and NC cows was 0.4°C below DC. In contrast, maximum Tre was similar for NC and DC groups, at 0.5 to 0.6°C above the CC group. Skin temperature for CC cows was always less than DC cows. Skin temperature for NC cows was equal to CC for minimum skin temperature, but exceeded both CC and DC cows for maximum skin temperature. Average skin temperature decreased from E to L, which suggested heat adaptation. The thermal advantage of night (lowest Ta and greatest thermal gradient) versus day cooling (greatest Ta and lowest thermal gradient) was increased heat transfer via thermal conductance with NC. The higher thermal strain of DC cows caused a larger percent decrease in morning milk yield than for NC cows. In contrast, use of convective cooling at night in the absence of elevated humidity could sufficiently reduce heat strain beyond DC to maintain milk production at a level that is closer to that of CC cows.


Assuntos
Doenças dos Bovinos/terapia , Transtornos de Estresse por Calor/veterinária , Abrigo para Animais , Animais , Bovinos , Indústria de Laticínios/métodos , Feminino , Transtornos de Estresse por Calor/terapia , Temperatura Alta , Lactação , Leite
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA