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PubMed2001

Intranasal temperature and humidity profile in patients with nasal septal perforation before and after surgical closure.

Common complaints of patients with a nasal septal perforation are crusting, dryness and bleeding. As shown previously, intranasal humidity values are significantly lower in patients with a septal perforation compared with healthy volunteers. The aim of this study was to determine the influence of surgical closure of septal perforations on intranasal temperature and humidity, and to evaluate changes in clinical symptoms after surgery. Ten patients with septal perforations were included in the study. Intranasal temperature and humidity were measured at the nasal valve and anterior turbinate areas before and after surgical closure. Clinical symptoms were assessed using a nasal symptom score. The end-inspiratory humidity values were significantly (P < or = 0.05) higher postoperatively than preoperatively. The increase in temperature at the anterior turbinate area was significantly higher postoperatively. The temperature values at the nasal valve area were not significantly different. Recurrent epistaxis and nasal dryness were reduced after surgery. Nasal septal perforations disturb the intranasal temperature and humidity profile. After surgical closure, heating and humidification is improved. This may be responsible for the reduction of frequent complaints such as bleeding and dryness.

Adult↗
PubMed2006

Effect of temperature and relative humidity on the stability of infectious porcine reproductive and respiratory syndrome virus in aerosols.

The objective of this experiment was to describe the stability of airborne infectious porcine reproductive and respiratory syndrome virus (PRRSV) as a function of temperature and relative humidity. A cloud of infectious PRRSV was aerosolized using 24-jet Collison nebulizer into a dynamic aerosol toroid (DAT) maintained at a specific temperature and relative humidity. The PRRSV cloud within the DAT was sampled repeatedly over time using SKC BioSampler impingers and the total viral RNA (RT-PCR) and concentration of infectious PRRSV (TCID50) in the air samples was determined. As measured by quantitative RT-PCR, PRRSV RNA was stable under the conditions evaluated in this study. Thus, a comparison of viral RNA and Rhodamine B dye, a physical tracer, found no significant difference in the slopes of the lines. Titers of infectious virus were plotted by time and the half-life (T1/2) of infectious PRRSV was calculated using linear regression analysis. An analysis of the results showed that aerosolized PRRSV was more stable at lower temperatures and/or lower relative humidity, but temperature had a greater effect on the T1/2 of PRRSV than relative humidity. Based on these results, an equation was derived to predict the T1/2 of infectious airborne PRRSV for any combination of environmental temperature and relative humidity.

Aerosols↗
PubMed2001

Monitoring in-shoe plantar pressures, temperature, and humidity: reliability and validity of measures from a portable device.

OBJECTIVE: To investigate the reliability and validity of measures obtained from a portable electronic device used to monitor changes in plantar pressure, temperature, and humidity that occur within the shoe during prolonged activity. DESIGN: Descriptive study comparing electronic sensor output with criterion values. SETTINGS: Indoor level walkway for pressure data; uncontrolled, outdoor environment for step count data; enclosed environmental control chamber for humidity and temperature data. PARTICIPANTS: Convenience sample of 4 healthy, sensate subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Correlations between sensor output and criterion measures were determined for pressure and temperature data. The absolute differences between sensor output and criterion values of temperature, humidity, and step count were also determined. RESULTS: Pressure measurements from electronic sensors correlated highly with criterion values (r > or =.82), both before and after prolonged use. Relative humidity sensor output were within 5% of hygrometer values. In-shoe temperature data correlated highly with criterion values (r > or =.99), and differed from known temperatures by.50 degrees +/-.84 degrees C and.96 degrees +/- 1.56 degrees C at the forefoot and heel, respectively. Electronic step counts recorded at the central forefoot were within 1 step of visual step counts. Pressure tracings obtained from the device during different weight-bearing activities revealed qualitatively distinct pressure patterns. CONCLUSION: The device provides valid and reliable measures of in-shoe plantar pressures, temperature, and humidity during prolonged activity.

Diabetic Foot↗
PubMed2001

Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates.

BACKGROUND: Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. OBJECTIVE: The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. METHODS: During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. RESULTS: The low RH group homes started in June with a mean +/- SE of 401 +/- 124 live mites and 17 +/- 3 microg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 +/- 3 live mites per gram (P =. 004) and 4 +/- 1 microg of Der 1 per gram of dust (P <.001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 microg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P <.001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. CONCLUSION: This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels.

Air Pollution, Indoor↗
PubMed2003

Kinetics of size changes of individual Bacillus thuringiensis spores in response to changes in relative humidity.

Using an automated scanning microscope, we report the surprising result that individual dormant spores of Bacillus thuringiensis grow and shrink in response to increasing and decreasing relative humidity. We simultaneously monitored the size of inorganic calibration particles. We found that the spores consistently swell in response to increased relative humidity, and shrink to near their original size on reexposure to dry air. Although the dispersion of swelling amplitudes within an ensemble of spores is wide (approximately 30% of the average amplitude), amplitudes for individual spores are highly correlated between different swelling episodes, suggesting that individual spores respond consistently to changes in humidity. We find evidence for two distinct time scales for swelling: one with a time scale of no more than approximately 50 s, and another with a time scale of approximately 8 min. We speculate that these two mechanisms may be due to rapid diffusion of water into the spore coat + cortex, followed by slower diffusion of water into the spore core, respectively. Humidity-dependent swelling may account for the greater kill effectiveness of spores by gas-phase chlorine dioxide, formaldehyde, and ethylene oxide at very high relative humidity.

Bacillus thuringiensis↗
PubMed2006

The effect of temperature and humidity on the bionomics of six African egg parasitoids (Hymenoptera: Trichogrammatidae).

The life table statistics of six native Kenyan species/strains of Trichogramma and Trichogrammatoidea were established using a factitious host Corcyra cephalonica, Stainton (Lepidoptera: Pyralidae), at eight different temperatures (10, 15, 20, 25, 28, 30, 32 and 35 degrees C) and two humidity levels (40-50 and 70-80%). The objective was to select insects with superior attributes for augmentative release against lepidopteran pests in horticultural crops. Both temperature and humidity affected developmental time and life table parameters of the parasitoids but temperature played a more critical role. Developmental time was inversely related to temperature. The intrinsic and finite rates of increase increased with temperature up to 30 degrees C. Both net reproduction rate and intrinsic rate of increase were higher at the lower humidity. Temperature inversely affected generation time of parasitoid strains regardless of the relative humidity. Two strains of Trichogramma sp. nr. mwanzai collected from both low and medium altitudes and Trichogrammatoidea sp. nr. lutea from the mid-altitudes, were better adapted to both low and high temperatures than the other strains, as indicated by the high intrinsic and net reproductive rates, at both humidity levels. These three strains appear to be promising candidates for augmentation biocontrol against the African bollworm Helicoverpa armigera in Kenya.

Animals↗
PubMed2001

Influence of incubator humidity on sleep and behaviour of neonates kept at stable body temperature.

UNLABELLED: The influence of incubator air humidity (via passive humidification through use of a water reservoir or via active humidification to 2 and 4 kPa) on sleep and behavioural changes was investigated in 13 neonates. The thermal environment of the incubator was servocontrolled via an interactive device tracking the skin temperature changes of the neonates. Using this servocontrolled skin temperature derivative heating programme, it is believed that an increase in air moisture content (reducing evaporative skin cooling) can be counterbalanced by a fall in neutral air temperature, so as to keep the body thermally constant. This procedure permits the experimental evaluation of the specific effect of air humidity on the thermal equilibrium air temperature and the thermal comfort of neonates without eliciting thermoregulatory mechanisms. Under the experimental conditions, in order to keep body temperature stable an increase in water vapour partial pressure from 1.72 (water reservoir) to 3.99 kPa (produced by a nebulizer) is counterbalanced by a decrease in air temperature of 1.49 degrees C. Within this humidity range, the air temperature must be lowered by 0.05 degrees C when the vapour pressure is increased by 0.08 kPa. The magnitude of this deviation depends on the humidity range and is probably a result of changes in the wetted skin area. CONCLUSION: When body temperature is kept constant, changes in air humidity do not modify sleep, body motility and respiratory and heart rates in neonates.

Body Temperature↗
PubMed1980

An automated flow-temperature-humidity control system.

An automated system that controls air flow, temperature, and humidity has been developed from a commercially available temperature=humidity indicator and a specially built flow-temperature-humidity control module. Parameters are set using direct-reading dials on the control module. The air flow is maintained using a mass-flow controller while process controllers connected to the indicator regulate humidity and temperature. The system will run indefinitely without need for operator intervention. If the module and indicator are calibrated properly, accurate air flows (+/- 2% of full scale), temperatures (+/- 0.3 degrees C), and humidities (+/- 2% RH) can be achieved.

Environment, Controlled↗
PubMed2005

WBGT clothing adjustments for four clothing ensembles under three relative humidity levels.

Threshold limit values for heat stress and strain are based on an upper limit wet bulb globe temperature (WBGT) for ordinary work clothes, with clothing adjustment factors (CAF) for other clothing ensembles. The purpose of this study was to determine the CAF for four clothing ensembles (Cotton Coveralls, Tyvek 1424 Coveralls, NexGen Coveralls, and Tychem QC Coveralls) against a baseline of cotton work clothes and to determine what effect relative humidity may have. A climatic chamber was used to slowly increase the level of heat stress by increasing air temperature at three levels of relative humidity (20%, 50%, and 70%). Study participants wore one of the five ensembles while walking on a treadmill at a moderate metabolic rate of 155 W m-2 (about 300 W). Physiological data and environmental data were collected. When the participant's core temperature reached a steady state, the dry bulb temperature was increased at constant relative humidity. The point at which the core temperature began to increase was defined as the inflection point. The environmental temperature recorded 5 min before the inflection point was used to calculate the critical WBGT for each ensemble. A three-way analysis of variance with ensemble by humidity protocol interactions and a multiple comparison test were used to make comparisons among the mean values. Only the vapor-barrier ensemble (Tychem QC) demonstrated an interaction with humidity level. The following CAFs are proposed: Cotton Coveralls (0 degrees C-WBGT), Tyvek 1424 Coveralls (+1), NexGen Coveralls (+2), and Tychem QC Coveralls (+10).

Adult↗
PubMed2005

Investigating the evaporation of metered-dose inhaler formulations in humid air: single droplet experiments.

The effect of excipients and humidity on the evaporation of propellant from metered-dose inhaler (MDI) formulations was examined by means of single, pendant droplet experiments. Droplets of pure hydrofluoroalkane (HFA) 227ea propellant, as well as propellant-ethanol and propellant-ethanol-sorbitan-trioleate mixtures, were suspended by needle into a conditioned viewing chamber. Droplet evaporation was recorded through a microscope-coupled CCD camera for each mixture, with viewing chamber conditions of 37 degrees C and either 100% or <10% relative humidity, over a size range from approximately 4 to approximately 1 microL. Volume versus time data was collected for each droplet through digital processing of image frames, according to Axisymmetric Drop Shape Analysis (ADSA) routines. No significant difference was observed in the rate of change of droplet volume (i.e., evaporation rate) between dry and humid conditions, regardless of the formulation studied. In addition, the rate of propellant evaporation appeared unchanged despite the addition of 15% w/w ethanol to HFA 227ea, while only slight reductions in evaporation rate were observed for a mixture containing 15% ethanol and 0.2% sorbitan trioleate. It was concluded that the rate of evaporation of propellant from HFA-based MDI formulations likely remains unchanged in the presence of high levels of humidity. Therefore, alternative explanations should be explored to explain the increase in MDI particle deposition in highly humid, confined airways.

Aerosol Propellants↗
PubMed1999

Fluctuating hydrating and dehydrating relative humidities effects on the life cycle of Dermatophagoides farinae (Acari: Pyroglyphidae).

Reducing relative humidity to < 50% in homes is recommended as one means of reducing dust mite populations in the homes of those who suffer allergies to house dust mites. Because of some activities in the home (e.g., bathing, cooking, opening windows), it may not be possible to keep relative humidity constantly < 50%. We determined how the fluctuating daily regimes of hydrating (75%) and dehydrating (35%) relative humidities affected the development of Dermatophagoides farinae Hughes. The life cycle was completed (egg to adults) when mites were given regimes of 24 h at 75% RH, 8 h at 75% and 16 h at 35% RH, 6 h at 75% and 18 h at 35% RH, and 4 h at 75% and 20 h at 35% RH. The time required to complete development was inversely related to the amount of moist air given daily. Development took 58.3 +/- 1.44, 64.7 +/- 1.87, and 82.4 +/- 2.39 d for 8, 6, and 4 h of moist air daily, respectively. In comparison, the life cycle was completed in 41.1 +/- 0.50 d when development occurred at a constant 75% RH. Egg incubation time was significantly longer for fluctuating ambient relative humidity compared to a continuous 75 or 35% RH. Of the emerging larvae 53.8, 72.7, 62.7, and 85.0% completed the life cycle when given 4, 6, 8, and 24 h 75% RH daily and 35% RH for the remainder of the day. This study revealed that D. farinae can complete development when given only short periods of moist air daily but the rate of development is much slower than development at a constant 75% RH. Therefore, reducing ambient relative humidity does reduce the rate of development of mite populations and the accumulation of dust mite allergen.

Animals↗
PubMed2003

Relative humidity is a key factor in the acclimation of the stomatal response to CO(2).

Previous work has shown that stomata of growth chamber-grown Vicia faba leaves have an enhanced CO2 response when compared with stomata of greenhouse-grown plants. This guard cell response to CO2 acclimatizes to the environmental conditions on the transfer of plants between the two environments. In the present study, air relative humidity is identified as a key environmental factor mediating the changes in stomatal sensitivity to CO2. In the greenhouse environment, elevation of relative humidity to growth chamber levels resulted in an enhanced CO2 response, whereas a reduction in the light level to that comparable to growth chamber conditions had no effect on stomatal CO2 sensitivity. The transfer of plants between humidified and normal greenhouse conditions resulted in an acclimation response with a time-course matching that previously obtained in transfers of plants between greenhouse and growth chamber environments. The high stomatal sensitivity to CO2 of growth chamber-grown plants could be reduced by lowering growth chamber relative humidity and then restored with its characteristic acclimation time-course by an elevation of relative humidity. Leaf temperature was unchanged during this restoration, eliminating it as a primary factor in the acclimation response. Humidity regulation of stomatal CO2 sensitivity could function as a signal for leaves inside dense foliage canopies, promoting stomatal opening under low light, low CO2 conditions.

Acclimatization↗
PubMed1996

Effect of periocular humidity on the tear film lipid layer.

The purpose of this study was to determine the relationship between the tear film and humidity by examining whether alterations in periocular humidity influence the thickness of the tear film lipid layer. Thirteen dry eye subjects presenting with a baseline lipid layer thickness of < or = 60 nm were fitted with modified swim goggles in which the right eye (OD) was exposed to conditions of high humidity and the left eye (OS) remained exposed to ambient room conditions. The lipid layer was monitored over a 60-min time course with goggles on and for an additional 60 min following goggle removal. The OD lipid layer increased significantly in thickness within 5 min of exposure to conditions of high humidity (p < 0.0001), reaching a maximum increase of 66.4 nm after 15 min of goggle wear (p < 0.0001). This maximum increase to a lipid layer thickness of 120.5 nm was maintained at the 30- and 60-min goggle time points. No significant change was detected OS. Following goggle removal, OD values declined but remained significantly elevated over the OS lipid layer thickness throughout the 60-min postgoggle period. Moderate to total relief of dry eye symptoms was reported during goggle wear and generally persisted at a reduced level for 1-3 h following goggle removal. Increased periocular humidity results in an increase in tear film lipid layer thickness, possibly by providing an environment that is more conducive to the spreading of meibomian lipid and its incorporation into the tear film.

Adult↗
PubMed1997

Airway humidification in mechanically ventilated neonates and infants: a comparative study of a heat and moisture exchanger vs. a heated humidifier using a new fast-response capacitive humidity sensor.

OBJECTIVE: To study the efficiency of a heated humidifier and a heat and moisture exchanger in mechanically ventilated neonates and infants. DESIGN: Prospective, controlled, clinical study. SETTING: University pediatric intensive care unit. PATIENTS: Forty neonates and infants who needed mechanical ventilation were enrolled in the study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A heat and moisture exchanger and active airway humidification were alternately used in the same patients to exclude interindividual differences in airway humidification. Airway humidity was measured by a new fast-response capacitive humidity sensor which measures airway humidity with an acquisition rate of 20 Hz throughout the respiratory cycle. The humidity sensor was placed at the endotracheal tube adapter. Measurements were done at the beginning and at the end of three consecutive sessions of passive, active, and again passive airway humidification, each session lasting 6 hrs. There was no significant difference between mean inspiratory airway humidity with the heated humidifier (33.8 +/- 2.9 mg/L) and with the heat and moisture exchanger (34.0 +/- 2.6 mg/L). Moreover, the mode of airway humidification did not significantly influence body temperature or PCO2. No serious side effects such as endotracheal tube occlusion were observed. CONCLUSIONS: Passive airway humidification by a heat and moisture exchanger is effective in mechanically ventilated neonates and infants over a 6-hr period. However, the performance and safety of a heat and moisture exchanger in prolonged mechanical ventilation remain to be proven.

Costs and Cost Analysis↗
PubMed2001

A humidity-sensitive Arabidopsis copine mutant exhibits precocious cell death and increased disease resistance.

The copines are a newly identified class of calcium-dependent, phospholipid binding proteins that are present in a wide range of organisms, including Paramecium, plants, Caenorhabditis elegans, mouse, and human. However, the biological functions of the copines are unknown. Here, we describe a humidity-sensitive copine mutant in Arabidopsis. Under nonpermissive, low-humidity conditions, the cpn1-1 mutant displayed aberrant regulation of cell death that included a lesion mimic phenotype and an accelerated hypersensitive response (HR). However, the HR in cpn1-1 showed no increase in sensitivity to low pathogen titers. Low-humidity-grown cpn1-1 mutants also exhibited morphological abnormalities, increased resistance to virulent strains of Pseudomonas syringae and Peronospora parasitica, and constitutive expression of pathogenesis-related (PR) genes. Growth of cpn1-1 under permissive, high-humidity conditions abolished the increased disease resistance, lesion mimic, and morphological mutant phenotypes but only partially alleviated the accelerated HR and constitutive PR gene expression phenotypes. The disease resistance phenotype of cpn1-1 suggests that the CPN1 gene regulates defense responses. Alternatively, the primary function of CPN1 may be the regulation of plant responses to low humidity, and the effect of the cpn1-1 mutation on disease resistance may be indirect.

Amino Acid Sequence↗
PubMed1996

Reduction in humidity as a method of controlling mites and mite allergens: the use of mechanical ventilation in British domestic dwellings.

BACKGROUND: Low humidity is an important limiting factor for mite population growth. Reducing humidity can therefore be used as a method to control mites within the home. OBJECTIVE: This study investigated the effect of mechanical ventilation heat recovery (MVHR) units on house dust mites and mite allergen Der p 1 in typical homes in the North-West of England. METHODS: Mite counts and Der p 1 levels were measured at 3-monthly intervals over a period of 1 year in 18 houses (nine with MVHR units and nine architecturally matched control houses). Paired dust samples were collected using a vacuum cleaner with an air-flow rate 451/sec, adapted to collect the sample onto a preweighed filter paper. A 1 m2 area of bedroom carpet, living room carpet and mattress was sampled for 2 min. Indoor temperature and relative humidity (RH) levels were recorded for a period of 1 week before and after the winter period (November and February: 3 and 6 months data sets). The environmental questionnaire was completed at the beginning and at the end of the study. RESULTS: No difference in either Der p 1 concentrations or mite counts in any of the sampling sites at 3, 6, 9 and 12 months as compared with the baseline values was found, both within and between the groups (P > 0.01). The measured levels of RH performed in autumn and winter were found to be lower in the MVHR houses compared to the architectural controls. The indoor temperature during each period did not differ between the groups. Questionnaire data showed that the severity of condensation improved in the MVHR homes, whilst during the winter period, the severity of condensation had increased in the architectural control group. CONCLUSIONS: The MVHR unit does not reduce indoor humidity to levels capable of retarding the mite population growth and decreasing mite allergens in the type of houses predominantly found in the mild and humid climate of the North-West of England.

Allergens↗
PubMed1983

House-dust mites and absolute indoor humidity.

The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared, however, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapour) did not contain noticeable concentrations of house-dust mites in the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, when this process is convenient to perform because of the low outdoor absolute humidity.

Animals↗
PubMed1984

Influence of variations in the ambient humidity on insensible water loss and thermoneutral environment of low birth weight infants.

Total evaporative water loss, transepidermal as well as respiratory water loss was measured in 8 infants on day 1, 11 infants from day 2 to 8 and 8 infants after day 8. Measurements were performed at two levels of humidity, either vapor pressure of 16 or 25 mmHg (2 133 or 3 333 Pa). Evaporative water loss was 40% lower at the higher humidity. Neither metabolic rate nor body temperature showed a significant difference between the two levels of humidity. The effect of the change in humidity on the neutral thermal environment was calculated, the neutral temperature being 0.05 degrees C lower when the vapor pressure is increased by 1 mmHg (133.3 Pa). We conclude that a high humidity is of limited value in nursing infants born after 30-40 weeks.

Humans↗