The response of patients with congestive heart failure to a rapid elevation in atmospheric temperature and humidity.
Explore the source record for details and available documents.
Heart Failure↗
SEARCH · Search PubMed
Results for “humidity response”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Photosynthetic and Stomatal Responses of Two Mangrove Species, Aegiceras corniculatum and Avicennia marina, to Long Term Salinity and Humidity Conditions.
Gas exchange characteristics were studied in two mangrove species, Aegiceras corniculatum (L.) Blanco and Avicennia marina (Forstk.) Vierh. var australasica (Walp.) Moldenke, grown under a variety of salinity and humidity conditions. The assimilation rate was measured as a function of the intercellular CO(2) concentration [A(c(i)) curve]. The photosynthetic capacity decreased with increase in salinity from 50 to 500 millimolar NaCl, as shown by decline in both the initial linear slope and the upper plateau of the A(c(i)) curve, with A. corniculatum being the more sensitive species. The decline in photosynthetic capacity was enhanced by increase in the leaf to air vapor pressure difference from 6 to 24 millibars, but this treatment caused a decrease in only the upper plateau of the A(c(i)) curve. Stomatal conductance was such that the intercellular CO(2) concentration obtaining under normal atmospheric conditions occurred near the transition between the lower linear and upper plateau portions of the A(c(i)) curves. Thus, stomatal conductance and photosynthetic capacity together co-limited the assimilation rate, which declined with increasing salinity and decreasing humidity. The marginal water cost of carbon assimilation was similar in most treatments, despite variation in the water loss/carbon gain ratio.
Journal Article↗
Combined environmental stress and physiological strain indices for physical training guidelines.
The purpose of this study was to develop guidelines based on the previously described environmental stress index (ESI) and physiological strain index (PSI) for work-rest cycles (WRC) during training, especially in the military. The ESI was introduced as a potential substitute for the Wet Bulb Globe Temperature Index because of the very high correlation coefficients between them. The ESI is constructed from the fast-reading meteorological response sensors ambient temperature (Ta), relative humidity (RH), and global radiation (GR), which require only a few seconds to reach equilibrium. The ESI, the first stress index using direct measurements of solar radiation (SR), is calculated as follows: ESI = 0.63Ta - 0.03RH + 0.002SR + 0.0054 (Ta x RH) - 0.073(0.1 + SR)(-1). The PSI is based on heart rate (HR) and rectal temperature (Tre) and can indicate heat strain online and analyze databases. The PSI is constructed as follows: PSI = 5(Tret - Tre0) x (39.5 - Tre0)(-1) + 5(HRt - HR0) x (180 - HR0)(-1), where Tre0 and HR0 are the initial Tre and HR, and Tret and HRt are simultaneous measurements taken at any time. The PSI is scaled from 0 to 10, whereby the respective variables, PSIHR and PSITre, representing the cardiovascular and thermoregulation systems, can contribute up to five units to the overall strain assessment. To integrate the PSI and ESI, we decided to use only the PSIHR component, which represents the metabolic rate and the strain reflected by the cardiovascular system. Furthermore, PSIHR is easier to measure, is easier to implement, and simplifies the integration with ESI. Concomitantly, PSIHR categorizes the strain between 0 and 5, the higher the value, the higher the strain. We believe that the use of the PSI WRC values will help in decreasing the risk of future heat injuries.
Algorithms↗
Effects of two kinds of sports shoes with different structure on thermoregulatory responses.
The present experiments were carried out to clarify the effects of two different kinds of shoes, i.e., the standard shoes and the mesh shoes, on thermophysiological responses and clothing microclimates (temperature and humidity) in five female students during rest and walking in the field conditions. Main results were summarized as follows: 1) Skin temperatures in instep, sole and leg were kept lower in the mesh shoes than in the standard shoes. 2) Rectal temperature and heart rates were also kept lower in the mesh shoes than in the standard shoes. 3) Questionnaires disclosed that the subjects wearing the mesh shoes felt less damp. These findings were discussed in terms of thermal physiology. The mesh shoes seemed to be more effective for both the dry and wet heat loss from the feet to the surroundings, resulting in the inhibition of increase in the core temperature.
Adult↗
[Effects of sauna on the values of blood circulation studied by the isometric exercise test].
Cardiovascular responses to isometric muscular exercise were evaluated during sauna. Nine healthy men aged 26 to 46 underwent testing during 5-6 saunas with one week interval between sessions. Each sauna included 2-6 heatings of 8-15 minutes (80-85 degrees C, humidity 15%) followed by complete cooling. Cardiovascular response during handgrip (45 seconds) were measured before sauna, after the first interval and 25 minutes after the end of sauna treatment.
Adult↗
[Practical possibilities of the objective quantitative olfactometry (author's transl)].
Explore the source record for details and available documents.
Adult↗
Helmet design to facilitate thermoneutrality during forest harvesting.
The purpose of this investigation was to evaluate the ventilatory characteristics of vented and non-vented helmets for use in forestry harvesting operations. A ventilation index developed by Birnbaum and Crockford (1978) was used to determine the ventilation capacity of twelve helmets varying in design and presence, location, and dimension of vents. Helmets with top vents had higher ventilation indices than non-vented, side and side/top-vented helmets. Ten physically fit men participated in a maximal oxygen consumption test and four trials wearing a non-vented, round-side-vented, round-top-vented or rectangulartop-vented helmet. Trials simulated typical summer environmental conditions (28 degrees C, 80% rh) and physiological work loads (40% VO(2)max) experienced during forest harvesting in New Zealand. The temperature and humidity under the helmet was typically lowest when the helmet with the largest vented area (288 mm(2)) in the crown was worn, although physiological responses (temperatures at the tympanum, ear and scalp; humidity at the centre of the helmet) of the participants to wearing the helmets differed significantly during some rest periods only. Top-vented helmets (in this experiment measured 288 mm(2)) should be worn to minimize temperature and humidity of the head during forest harvesting operations.
Adaptation, Physiological↗
Plasma volume and ions during exercise in cool, dry; hot, dry; and hot, humid conditions.
We studied the effects of heat and relative humidity (RH) on plasma volume (PV) and ion responses to submaximal exercise and 60 min recovery in Thoroughbreds. Five horses were exercised at 50% of peak VO2 in cool, dry (CD, T = 22 degrees C, RH = 45-55%), and hot, humid (HH, T = 30-34 degrees C, RH = 80-85%) conditions until a pulmonary artery temperature of 41.5 degrees C was reached. Blood was obtained from the carotid artery. Body mass was measured at rest and after 30 min of recovery. The thermal conditions had no effect on the PV and ion responses during exercise and initial 30 min of recovery. Exercise resulted in an 8.5% decrease in PV within the first 2 min and, in the absence of changes in plasma [Na+] and [Cl-], was responsible for a 150 to 185 mmol decrease in plasma Na+ and Cl- contents. The decrease in PV was responsible for about 50% of the increase in packed cell volume (37% at rest; 51% at 2 min of exercise). Plasma [K+] and K+ content increased rapidly during the first 2 min of exercise. With cessation of exercise, plasma [K+] declined with a half time of about 2 min; recovery of PV and plasma Na+ and Cl- contents occurred with a half time of 10-15 min, with nearly complete recovery by 30 min. In the HD trial, between 30 and 60 min of recovery there were further decreases in PV and ion contents. It is concluded that with this exercise protocol, thermal stress had minimal influence on the rate and magnitude of exercise-induced changes in PV and ion contents. However, thermal stress during recovery from exercise may impede the restoration of PV and ion contents.
Animals↗
Behavioral genetics of thermosensation and hygrosensation in Drosophila.
Whereas temperature and humidity are critical variables affecting physiology, behavior, and evolution, the genetic and neuronal underpinnings of thermosensation and hygrosensation remain poorly understood. We have initiated a behavioral-genetic investigation of these sensory systems in Drosophila. Behavioral tests are described for the rapid screening of mutants defective in thermosensation and hygrosensation. We demonstrate the strong responses of normal flies to temperature and humidity. Two mutants were found with defects in thermosensation, only one of which is also defective in hygrosensation, indicating that they involve different sensory mechanisms. Ablation experiments further separate these sensory systems by showing that thermoreceptors are housed in the third antennal segment, whereas hygroreceptors are located more distally in the antennal arista.
Animals↗
Field performance of a nephelometer in rural kitchens: effects of high humidity excursions and correlations to gravimetric analyses.
Rural kitchens of solid-fuel burning households constitute the microenvironment responsible for the majority of human exposures to health-damaging air pollutants, particularly respirable particles and carbon monoxide. Portable nephelometers facilitate cheaper, more precise, time-resolved characterization of particles in rural homes than are attainable by gravitational methods alone. However, field performance of nephelometers must contend with aerosols that are highly variable in terms of chemical content, size, and relative humidity. Previous field validations of nephelometer performance in residential settings explore relatively low particle concentrations, with the vast majority of 24-h average gravitational PM2.5 concentrations falling below 40 microg/m3. We investigate relationships between 24-h gravitational particle measurements and nephelometric data logged by the personal DataRAM (pDR) in highly polluted rural Chinese kitchens, where gravitationally determined 24-h average respirable particle concentrations were as high as 700 microg/m3. We find that where relative humidity remained below 95%, nephelometric response was strongly linear despite complex mixtures of aerosols and variable ambient conditions. Where 95% relative humidity was exceeded for even a brief duration, nephelometrically determined 24-h mean particle concentrations were nonsystematically distorted relative to gravitational data, and neither concurrent relative humidity measurements nor use of robust statistical measures of central tendency offered means of correction. This nonsystematic distortion is particularly problematic for rural exposure assessment studies, which emphasize upper quantiles of time-resolved particle measurements within 24-h samples. Precise, accurate interpretation of nephelometrically resolved short-term particle concentrations requires calibration based on short-term gravitational sampling.
Air Pollution, Indoor↗
Effect of combined heat and radiation on microbial destruction.
A series of experiments at several levels of relative humidity and radiation dose rates was carried out using spores of Bacillus subtilis var. niger to evaluate the effect of heat alone, radiation alone, and a combination of heat and radiation. Combined heat and radiation treatment of microorganisms yields a destruction rate greater than the additive rates of the independence agents. The synergistic mechanism shows a proportional dependency on radiation dose rate an Arrhenius dependency on temperature, and a dependency on relative humidity. Maximum synergism occurs under conditions where heat and radiation individually destroy microorganisms at approximately equal rates. Larger synergistic advantage is possible at low relative humidities rather than at high relative humidities.
Bacillus subtilis↗
Adaptations to daily exercise in hot and humid ambient conditions in trained thoroughbred horses.
The objectives of this study were to: 1) determine the effects of heat and high relative humidity (RH) on the clinical and physiological responses of horses during and after daily exercise training and 2) determine whether repeated exposure to, and exercise in, the heat would result in improved thermal tolerance (heat acclimation). Six trained Thoroughbred horses completed 1 h of submaximal exercise in cool, dry conditions (CD) and during a daily 4 h period of exposure to high heat and humidity (HH, room temperature = 33-35 degrees C, RH = 80-85%) for 22 days. Rectal temperature (Tre) and heart rate (HR) were measured before, during and after exercise and respiratory rate (RR) was measured before exercise and during a 2 h recovery. In HH, the rate of rise in Tre was significantly higher than in CD. However, by HH Day 5, Tre before, during and after exercise was significantly lower than on HH Day 1. The day-to-day decrease in Tre during exercise was reflected in significant decreases in heat storage following exercise by HH Day 10 (910 +/- 47 kcal) when compared to HH Day 1 (1211 +/- 75 kcal). At rest, RR was initially higher in HH than CD, and a further increase in pre-exercise RR from HH Day 1 to Day 10 may have contributed to the lower pre-exercise Tre. Recovery RR was higher after HH Day 1 and was associated with a lower end-of-exercise HR did not change in the 1 h before exercise in CD and did not differ from HH Days 1-22. By HH Day 10, mean HR during the latter part of exercise was lower than HH Day 1 and was not different from pre-exercise by 60 min of recovery. Pre-exercise body mass did not change during the 3 wk period and the decrease in body mass that occurred during the 4 h training period was significantly attenuated by HH Day 15 (9.8 +/- 0.8 kg) when compared to HH Day 1 (12.5 +/- 0.8 kg). Over the 3 week period of HH, mean 24 h water consumption increased from 26.0 +/- 2.1 litres to 39.5 +/- 3.2 litres, largely reflecting a 2-fold increase in water intake during the 4 h period of heat exposure. It is concluded that 3 weeks of daily exposure to, and exercise in, hot and humid ambient conditions resulted in a progressive reduction in thermal and cardiovascular strain. Furthermore, the reported physiological adaptations are consistent with an improved thermal tolerance (heat acclimation).
Adaptation, Physiological↗
Selective real-time measurement of styrene vapor using a surface-acoustic-wave sensor with a regenerable organoplatinum coating.
The performance of a coated surface-acoustic-wave (SAW) sensor for monitoring styrene vapor is investigated. The effects of several organic co-contaminants and atmospheric humidity are described, and regeneration of the sensor coating is demonstrated. The dual-SAW delay-line oscillator employs a reagent coating of trans-PtCl2(ethylene)(pyridine) to trap styrene via ethylene substitution. The rate of change of the sensor frequency is used to provide real-time measurement of styrene vapor concentrations. No effect on the response to styrene is observed upon simultaneous exposure to each of several olefin and non-olefin solvent vapors used with styrene in industrial processes. Butadiene, however, presents a reversible negative interference by successfully competing with styrene for reaction with the trapping agent. The response to styrene exhibits a moderate positive humidity dependence. Following prolonged exposure, the original complex can be regenerated in situ by exposure to ethylene gas, permitting repeated use of the sensor. An emphasis is placed on the application of the sensor to workplace air monitoring.
Chemical Phenomena↗
Aerosol light scattering measurements as a function of relative humidity.
The hygroscopic nature of atmospheric fine aerosol was investigated at a rural site in the Great Smoky Mountains National Park during July and August 1995. Passing the sample aerosol through an inlet, which housed an array of Perma Pure diffusion dryers, controlled the sample aerosol's relative humidity (RH). After conditioning the aerosol sample in the inlet, the light scattering coefficient and the aerosol size distribution were simultaneously measured. During this study, the conditioned aerosol's humidity ranged between 5% < RH < 95%. Aerosol response curves were produced using the ratio bspw/bspd; where bspw is the scattering coefficient measured at some RH greater than 20% and bspd is the scattering coefficient of the "dry" aerosol. For this work, any sample RH values below 15% were considered dry. Results of this investigation showed that the light scattering ratio increased continuously and smoothly over the entire range of relative humidity. The magnitude of the ratio at a particular RH value, however, varied considerably in time, particularly for RH values greater than approximately 60%. Curves of the scattering coefficient ratios as a function of RH were generated for each day and compared to the average 12-hour chemical composition of the aerosol. This comparison showed that for any particular RH value the ratio was highest during time periods of high sulfate concentrations and lowest during time periods of high soil or high organic carbon concentrations.
Aerosols↗
In vitro assessment of an ultrasonic flowmeter for use in ventilated infants.
An ultrasonic flowmeter could be advantageous over a differential pressure pneumotachograph having a constant error in varying conditions. The in vitro accuracy of ultrasonic tidal volume (VT) estimates for ventilated infants were evaluated. Flow linearity and frequency response were tested, as was the influence of humidity and oxygen content on the accuracy of VT estimates. The linearity was within the 5% limits between -350 and 350 mL x sec(-1) and was not affected by the presence of an endotracheal tube (ET). The frequency response was flat and unaffected by an ET up to 4.5 Hz. The VT in the range 7-100 mL, in air showed a mean error of 0.1% (95% confidence interval (CI) -0.2-0.4%) with a maximum and minimum of 6.5 and -3.5% respectively. Humidity did not affect accuracy. After calibration in air, the maximal mean error for measurements in pure oxygen was 3.0% (95% CI 1.9-4.1%). Repeated measurements over 5.5 h had a mean error of 0.4% (95% CI -0.7-0.1%). The in vitro evaluation of an ultrasonic flowmeter showed stable accuracy in mechanical ventilation conditions. Changing connection geometry and oxygen content did not increase the error to a clinically relevant degree. The flowmeter could therefore be a better alternative than the pneumotachograph for ventilated infants.
Humans↗
Environmental modification of western equine encephalomyelitis infection in the snowshoe hare (Lepus americanus).
The snowshoe hare (Lepus americanus) could be infected with western equine encephalomyelitis (WEE) virus and produce a viremia. Furthermore, viremia in hares exposed to variable climatic conditions differed significantly from viremias seen in the control animals held at constant temperatures. The viremia duration and titer were increased in animals subjected to fluctuating temperature and humidity. The time of onset of viremia was accelerated. Antibody response also increased in animals exposed to varying temperatures when compared with controls held at constant temperature and humidity. Snowshoe hares were studied at two distinct seasonal periods: winter, before reproductive activity; and summer, during reproductive midseason. Winter animals experienced greater viremia than did summer hares when exposed to fluctuating temperatures, suggesting a seasonality in the hare's susceptibility to host modification by environmental influences. These findings implicate the snowshoe hare as a possible mammalian amplifying host for WEE virus in the boreal forest.
Animals↗
[Effects of drugs and environmental factors on ciliary movement (author's transl)].
The effects of a number of drugs, potassium and calcium ions, and air humidity on mucociliary function were studied in isolated preparations of rats bronchial tree. Adrenergic drugs increased the rate of ciliary beat significantly. Cilioexitation also occurred, though to a smaller degree, after application of acetylcholine, pilocarpine, aminophylline, prednisolone, KI and NH4C1. Serotonin, histamine, and acetylcystein did not change ciliary frequency to any significant degree; however, histamine in high concentrations caused ciliary incoordination. Codein and normetadon, nicotine and pentobarbital had a dose-dependent ciliodepressive effect. However, small concentrations of nicotine and pentobarbital were slightly stimulative. Methysergid and phentolamine were slightly ciliodepressive. Alterations of the concentrations of calcium and potassium ions in the nutritive solution influenced ciliary frequency but had no effect on other characteristic features of the ciliary movement. The ciliated epithelium of the bronchial tree could be irreversibly damaged by air having low relative humidity.
Acetylcholine↗
Spectroscopy of growing and evaporating water droplets: exploring the variation in equilibrium droplet size with relative humidity.
We demonstrate that the thermodynamic properties of a single liquid aerosol droplet can be explored through the combination of a single-beam gradient force optical trap with Raman spectroscopy. A single aqueous droplet, 2-6 microm in radius, can be trapped in air indefinitely and the response of the particle to variations in relative humidity investigated. The Raman spectrum provides a unique fingerprint of droplet composition, temperature, and size. Spontaneous Raman scattering is shown to be consistent with that from a bulk phase sample, with the shape of the OH stretching band dependent on the concentration of sodium chloride in the aqueous phase and on the polarization of the scattered light. Stimulated Raman scattering at wavelengths commensurate with whispering gallery modes is demonstrated to provide a method for determining the size of the trapped droplet with nanometer precision and with a time resolution of 1 s. The polarization dependence of the stimulated scatter is consistent with the dependence observed for the spontaneous scatter from the droplet. By characterizing the spontaneous and stimulated Raman scattering from the droplet, we demonstrate that it is possible to measure the equilibrium size and composition of an aqueous droplet with variation in relative humidity. For this benchmark study we investigate the variation in equilibrium size with relative humidity for a simple binary sodium chloride/aqueous aerosol, a typical representative inorganic/aqueous aerosol that has been studied extensively in the literature. The measured equilibrium sizes are shown to be in excellent agreement with the predictions of Köhler theory. We suggest that this approach could provide an important new strategy for characterizing the thermodynamic properties and kinetics of transformation of aerosol particles.
Journal Article↗