These results suggest that PSR augments physiological and psychological strain and reduces vigilance in the heat. Taking a nap seemed to be effective in reducing psychological strain and inhibiting the decrease in vigilance.
This study compared heat strain during walking while wearing impermeable protective suits between fan-precooling and nonprecooling conditions. Six males engaged in 60 min of walking at a moderate speed (∼2.5 km/h) in a hot environment (37 °C, 40% relative humidity). Fanning using a fan (4.5 m/s) and spraying water over the body before wearing the suits produced significantly lower rectal temperature before the walking (37.3 ± 0.1 °C vs. 37.0 ± 0.1 °C, P < 0.05). In addition, whilst walking, rectal temperature was significantly lower in the precooling condition (maximum difference: 0.4 °C at 15 min of walking; 38.0 ± 0.1 °C vs. 37.8 ± 0.1 °C at the end of walking, P < 0.05). Although skin temperature decreased during fanning, no difference was observed during walking. Heart rate was lower in the precooling condition during the early stages of walking. Thermal and fatigue perceptions whilst walking did not differ between the conditions. Body weight loss was significantly lower in the precooling condition. These results may indicate that fan precooling attenuates exertional heat strain while wearing impermeable protective clothing. The fan-cooling method is practical, convenient, and yields lower heat strain during prolonged moderate exertion.
The Ministry of Health, Labour and Welfare of Japan reported that 47 workers died from employment-related heat stroke in 2010 due to hot temperature; a sharp increase from the average of 20 workers per year over the previous ten years 1) . Heat stroke made up 3.9% of all employment-related deaths in 2010, and it has become a critical issue in industrial health in Japan. Risk factors for heat stroke in the workplace include high workload, clothing and high heat stress environments involving high ambient temperatures, high humidity, high radiation levels and low air velocity 2) . These factors increase heat storage in the body and consequently elevate the deep body temperature. Worker age is also considered to increase the occurrence of heat stroke.ISO 7243 3) provides a simple standard for employees working under heat stress conditions using the wet-bulb globe temperature (WBGT) index. WBGT reference values are listed in ISO 72433) for acclimatized and non-acclimatized workers, corresponding to metabolic rates (MR) during work. In addition to ISO 7243 3) , ACGIH-TLVs 4) on heat stress and heat strain also set a WBGT limit in work places according to the MR level, acclimatization and work-rest ratio. To apply these standards or guidelines to workplaces, information about both the WBGT of the working environment and the MR of the employee during work is needed. The method for estimating MR by job content outlined in ISO 7243 3) is ambiguous. Though WBGT can be measured by a natural wet bulb sensor, globe sensor and air temperature sensor, measuring metabolic rate is difficult.ISO 8996 5 is needed to determine wet-bulb globe temperature (WBGT) reference values in order to reduce heat strain in physical workers. The aim of this study was to develop MR prediction equation for younger and older men in hot working environments. Methods: We measured the MR and heart rate (HR) of both younger and older men at ambient temperatures (T a ) of 25, 30 and 35°C while they cycled on a bicycle ergometer at a workload of 30, 45 and 60% of maximal oxygen uptake (V . O 2max ). Seven younger male university students aged 22.9 ± 0.7 (mean ± SD) years and seven older male workers aged 61.7 ± 2.2 (mean ± SD) years participated in this study. MR, HR and rectal temperature (T re ) were measured during the study. HR, ambient temperature (T a ), body weight (BW) and body fat percentage (BF) served as predictors of MR using multivariate analysis. To increase the MR prediction accuracy, the following three alternative predictors of HR were used: HR res , calculated as 100 × [(HR − resting HR) / (maximal HR − resting HR)]; HR net , calculated as (HR − resting HR); and HR i , calculated as (HR / resting HR). Results: The R 2 value indicated that the models with HR res or HR net were more accurate than those with HR i or HR. T a had a significantly positive correlation with MR in older men. BW had a significantly positive correlation with MR in both younger and older men, and BF had a significantly negative correlation with MR in both younger...
ABSTRACT:The aim of this study was to evaluate right ventricular (RV) remodeling and right heart failure associated with different causes of elevated pulmonary arterial pressure (PAP) in dogs. In total, 169 client-owned dogs with tricuspid regurgitation (TR) and 40 client-owned clinically healthy dogs were included. Dogs with TR were further categorised as suffering from chronic respiratory disorders (CRD), heartworm disease (HWD), mild/ moderate chronic degenerative mitral valvular disease (CDMD), and severe CDMD. Among the echocardiographic indices of the right heart, no significant difference in the tricuspid annular plane systolic excursion to aortic root diameter ratio was found among the clinical healthy controls and the four different TR categories. No significant differences in TR peak velocity and pulmonic regurgitation peak velocity were found among dogs in the four different TR categories. The ratio of the right to left ventricular basal diameter in the right ventricular-focused view was significantly higher in dogs with chronic respiratory disorders and dogs with heartworms. Left ventricular compression quantified using the eccentricity index and the ratio of the main pulmonary artery to aortic root diameter were significantly higher in dogs with HWD. Their right ventricular acceleration to ejection time (AT/ET) was significantly lower in dogs with HWD. Based on these findings, we conclude that right heart indices are affected by CRD, HWD, and moderate to severe CDMD. However, right heart indices derived from left heart measurements might be underestimated in dogs with CDMD.Keywords: left ventricular eccentricity indices; mean electrical axis; pulmonary hypertension; right heart remodelling; tricuspid annular plane systolic excursion List of abbreviationsAo = aortic root diameter, AT = acceleration time, CDMD = chronic degenerative mitral valvular disease, CRD = chronic respiratory disorders, CV = coefficient of variation, ECG = electrocardiography, ET = ejection time, HWD = heartworm disease, LA/Ao = left atrial/aortic root ratio, LVD = left ventricular basal diameter, LV-EI = left ventricular eccentricity index, MEA = mean electrical axis, MPA = main pulmonary artery, PAP = pulmonary arterial pressure, PH = pulmonary hypertension, PR = pulmonic valve regurgitation, RVD = right ventricular basal diameter, SBP = systemic blood pressure, SD = standard deviation, TAPSE = tricuspid annular plane systolic excursion, TR = tricuspid regurgitation, VHS = vertebral heart scale Pulmonary hypertension (PH) is defined by high diastolic or systolic PAP and may lead to right ventricular concentric or eccentric hypertrophy, right atrial enlargement, and right-sided heart failure (Serres et al. 2006). High PAP values above the reference range indicate PH, which can result from pre-and post-capillary haemodynamic changes (Kellihan and Stepien 2012). PH is a wellrecognised clinical condition in human patients and can be primary or secondary to various diseases of the pulmonary vasculature (Galie et al. 2009). Primar...
Abstract:To elucidate the action of nitroglycol (Ng) on cardiac muscles, the contractile and chronotropic responses of the isolated rat cardiac muscles to Ng in a cumulative manner were investigated. Ng produced negative chronotropic and inotropic effects on spontaneously beating right atria in concentrations ranging from 10-' to 3 x 10~ M. Ng also produced dose-dependent negative inotropic effects on electrically driven left atrial muscles. On the other hand, in right ventricle muscles, Ng induced positive inotropic effects. These results suggest that Ng acts directly on the cardiac muscles as well as vascular smooth muscles in acute poisoning.
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