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PubMedDate not supplied

Factors affecting humidity of inspired gas in a neonatal lung model.

OBJECTIVE: The American National Standards Institute recommends an absolute humidity of > or = 30 mg/L of inspired gas in patients receiving mechanical ventilation. This study was designed to assess the absolute humidity of inspired gas in relation to humidifier settings and environmental conditions in a test lung. STUDY DESIGN: Measurements were obtained at the endotracheal tube manifold of an artificial lung in an isolette or radiant warmer with use of a nonheated wired system and two different ventilator circuit lengths. Temperature and relative humidity were measured at three environmental temperatures and various humidifier settings. RESULTS: We achieved adequate absolute humidity levels only at near maximum humidifier settings. When the artificial lung was placed in an isolette with a standard circuit length inside the isolette, adequate absolute humidity was never reached at an environmental temperature of 30 degrees C. Increasing the length of the ventilator circuit situated inside the isolette or using a radiant warmer improved absolute humidity compared with that obtained with use of a standard circuit length. CONCLUSION: Recommended absolute humidity levels may not be reached at the manifold even at high humidifier settings. Thus actual measurements of relative humidity and temperature at the endotracheal tube site are necessary to optimize humidity according to American National Standards Institute recommendations.

Artificial Organs↗
PubMed1997

The effect of humidity on germination and infection of termites by the hyphomycete, Metarhizium anisopliae.

The effect of relative humidities (r.h.) from 90 to 100% on germination of a termite-active isolate of Metarhizium anisopliae (isolate FI25 and FI610) was studied using a liquid germinating medium to which the appropriate amount of glycerol had been added. Germination was increasingly delayed at water activities equivalent to 99, 98, and 96% r.h. and completely inhibited at 94, 92, and 90%. Twenty-one isolates were then screened for germination at 96 and 100% r.h. All isolates showed delayed germination at 96% r.h. but most isolates eventually gave a high final percentage germination at this humidity. Two isolates, FI527 and FI638, were markedly slower to germinate at both humidities. The susceptibility of two species of termites, Nasutitermes exitiosus and Coptotermes acinaciformis, to FI610 was tested at r.h. down to 86%-the lowest humidity at which the insects would survive. No consistent effect of humidity on pathogenicity was detected. Mortality occurred over the range range of humidities tested; sporulation from the disease-killed termites, however, occurred only at r.h. above 93%. It is concluded that the microclimate around living termites is usually sufficiently humid to ensure infection under most field conditions and that humidity is unlikely to limit the efficacy of the fungus in controlling termites.

Animals↗
PubMed1996

The influence of absolute humidity on shear bond adhesion.

OBJECTIVES: The purpose of this study was to investigate the relationship between dentine shear bond strength, using data from experiments performed according to a standard protocol, and the absolute humidity for a new, fourth generation dentine adhesive system. METHODS: Results of seven recently performed adhesion experiments using the same protocol and product were analysed. Groups of 10 human molars were each bonded in a humidity chamber. The temperature and relative humidity conditions varied from 23 to 37 degrees C and 30 to 95%. After bonding of the composite resin a shear bond test at a crosshead speed of 2.0 mm/min was performed. RESULTS: The bond strength levels of the dentine adhesive system were influenced significantly by extreme temperature and humidity differences. Adhesion levels varied from 27.8 (SD 8.5) MPA to 12.8 (SD 1.4) MPA. Isobond strength curves are a good method to gain insight into the humidity sensitivity of adhesive systems. CONCLUSIONS: Results of in vitro adhesive bonding procedures for a dentine adhesive can be significantly influenced by the absolute humidity levels at which the procedures are performed. Consequently "Materials and Methods" sections of publications should refer to absolute humidity or temperature and relative humidity levels as a relevant parameter.

Acid Etching, Dental↗
PubMed2002

Properties of heat-humidity cured cellulose acetate phthalate free films.

Cellulose acetate phthalate (CAP) free films containing diethyl phthalate (DEP) or triethyl citrate (TEC) as the plasticizer were prepared by the spray method. The chemical and mechanical properties of films were compared following heat-only (50 degrees C for 24 h) and heat-humidity curing (50 degrees C/75% RH for 24 h) conditions. The surface roughness of the heat-humidity cured films decreased compared to that of the uncured and heat-only cured films. The heat-humidity curing condition suppressed evaporation of the plasticizer, resulting in higher plasticizer levels remaining in the films, as compared to the heat-only curing condition. The heat-humidity curing also significantly increased the mechanical strength and decreased the water vapor permeability of the films. When exposed to the acidic media, despite rapid leaching of plasticizer, the heat-humidity cured films retained the most mechanical strength of the films prior to exposure. The moisture content and phthalic acid content after heat-humidity curing were increased slightly, but did not reach a level that would interfere with enteric performance. TEC was less volatile and produced films with increased % elongation, and decreased tensile strength and elastic modulus compared to the films plasticized with DEP. However, the DEP plasticized films were less permeable than TEC-plasticized films following heat-humidity curing. The results indicated that a short-term exposure of the CAP films to heat and humidity during the curing process greatly improved the degree of film coalescence and mechanical strength, without causing significant chemical degradation of the polymer.

Cellulose↗
PubMed2000

Regulation of the cutaneous allergic reaction by humidity.

Humidity is 1 of the environmental factors which regulate skin conditions. Effects of humidity on the cutaneous immune reaction were examined. Contact hypersensitivity to 2,4,6-trinitrochlorobenzene was elicited in C57BL/6 mice. The reaction was greater in mice housed under low humidity conditions (about 10%) for 2 days, at either the induction or elicitation phase, than in mice housed under rather high humidity conditions (80%). After housing under controlled humidity for 2 days, the number of I-A positive cells was 16% higher in the epidermis exposed to the dry condition. The increased population of FITC-positive cells were in regional lymph nodes after painting of FITC during housing under lower humidity. Our study demonstrated that the cutaneous immune reaction is regulated by environmental humidity and suggested 2 possible mechanisms, i.e., increase in Langerhans cells and increased penetration of allergen with low humidity.

Allergens↗
PubMed2001

Low relative humidity and aircraft cabin air quality.

Mucosal irritation remains a common complaint among travelers and flight attendants in aircraft cabins. Despite the fact that very low humidity is routinely encountered, few studies of its effects have been conducted in the cabin environment. The authors reviewed chamber and field studies in the experimental literature to explore whether there is an association and, if so, at what level it was likely to be present. Subjects who participated in prior research were not always able to perceive low humidity or changes in the humidity level and, at times, this inability has been confused in the literature with the lack of a humidity effect. The studies with more powerful experimental designs have demonstrated the effects of low humidity, such as drying of the skin and mucus membranes, and that a modest increase in relative humidity seems to alleviate a great number of symptoms. The exposure duration below during which the effects of low humidity are not noticeable is in the order of 3 to 4 h. It is conceivable that some symptoms experienced by flight attendants and passengers, especially on flights lasting 3 h or longer, may stem from low humidity.

Adult↗
PubMed1992

The effect of environmental temperature and humidity on 24 h energy expenditure in men.

The effects of environmental temperature and humidity and their interaction on 24 h energy expenditure were measured using whole-body indirect calorimetry in eight normal-weight young men who wore standardized light clothing and followed a controlled activity regimen. A randomized-block experimental design was used, with temperature effects assessed by measurements at 20, 23, 26 and 30 degrees, while humidity was altered from ambient (50-65% relative humidity) to high (80-93% relative humidity) at 20 and 30 degrees only. There was no significant effect of humidity on 24 h energy expenditure at the two extreme temperatures in this range, though when periods of sleep and exercise were excluded the energy expenditure at high humidity was significantly higher than that ambient humidity (P < 0.02). The effect of temperature at ambient humidity levels showed lower values at 23 and 26 degrees than at 20 and 30 degrees (P < 0.02). The effect of temperature was not equally apparent in all components of the 24 h energy expenditure, as sleeping metabolic rate and the energy cost of walking and cycling showed no significant effect of temperature over this range. This raises the possibility that the effects of temperature are attributable to behavioural changes during the waking portion of the day rather than any non-shivering thermogenic mechanisms at tissue level.

Adult↗
PubMed2001

The influence of plasticizer on heat-humidity curing of cellulose acetate phthalate coated beads.

The objectives of the present study are to investigate the effect of plasticizer type and level on the curing of cellulose acetate phthalate (CAP) coated beads with and without the presence of humidity. Theophylline beads were coated in a fluidized-bed with CAP dispersion (Aquacoat CPD) plasticized by a water-insoluble plasticizer, diethyl phthalate (DEP), or a water-soluble plasticizer, triethyl citrate (TEC), at various levels. The coated heads were cured at a heat-only condition (50 degrees C for 24 hr) and a heat-humidity condition (50 degrees C/75% RH for 24 hr). Rapid drug release in the acidic media was found for both heat-only and heat-humidity cured beads when plasticizer was not used in the coating dispersion, indicating that the heat-humidity curing is ineffective without the presence of plasticizers. When plasticizer was incorporated in the coating formulations, heat-humidity curing effectively improved the acid resistance of the coated films at all plasticizer levels investigated. The minimum plasticizer level required to obtain enteric release profiles for heat-humidity cured beads coated at an outlet coating temperature of 46 degrees C was 15%. This limit was further decreased when the beads were coated at a lower temperature due to a less plasticizer loss at the lower coating temperature. Between the two plasticizers, less TEC was lost during the coating process, and TEC was more effective compared to DEP with regards to heat-humidity curing at the 10% plasticizer level. The enteric release profiles were reproducible following a 7-day drying period at 40 degrees C for all heat-humidity cured beads that had initially passed the enteric release dissolution test. The rapid leaching of TEC and DEP into the.

Cellulose↗
PubMed1998

Water balance of Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) maintained by brief daily spells of elevated air humidity.

A facility was constructed to expose cultured Dermatophagoides pteronyssinus (Trouessart) to 24-h cycles of changing relative humidity; low humidity was interrupted every day by a period of high humidity. The temperature was kept at 16 degrees C, a common temperature on the ground floor of Dutch houses. Partially dehydrated mites were exposed to various humidity regimes in the absence of food and liquid water. Some mites gained weight when moist air was given for only 1.5 h every day. In the presence of food, egg production was recorded when moist air was given for at least 3 h daily, whereas the average relative humidity was quite low and less than the critical equilibrium humidity of D. pteronyssinus. Brief spells of elevated humidity allowed populations to survive much longer in a microclimate that was otherwise too dry, and may be decisive for survival during the winter months. We found that average relative humidity was misleading as an indicator of mite survival and growth conditions.

Acari↗
PubMed2005

Relative humidity of the external auditory canal in normal and abnormal ears, and its pathogenic effect.

OBJECTIVE: To find the relative humidity of the normal external ear canal and to demonstrate that the relative humidity of the external auditory canal was higher in abnormal ears, i.e. ears commonly associated with chronic discharge. SETTING: Secondary health care within the ENT departments of Addenbrooke's and Hinchingbrooke hospitals. DESIGN: A clinical observational study. PARTICIPANTS: Volunteers seen in ENT outpatients. Inclusion criteria for the normal ear group, was a normal ear with no history of infection or previous ear disease. Inclusion criteria for abnormal ear group commonly associated with chronic discharge. Exclusion criteria were the presence of pus or infection within the ear canal. METHOD: The relative humidity of the external ear canal was measured in normal and abnormal ears. Abnormal ears were grouped as those commonly associated with chronic discharge, mastoid cavities, tympanic perforations, recurrent otitis externa and hearing-aided ears. RESULTS: The range of relative humidity of normal ears is 40-70%. The humidity in abnormal ears was found to be significantly higher than the humidity in normal ears (P < 0.0001). CONCLUSION: The raised relative humidity in the external canal may explain the predisposition of certain abnormal ears to chronic discharge and infection. If the humidity of the canal could be brought down to a normal level, this could offer a new therapeutic treatment.

Animals↗
PubMed2004

Impact of indoor air temperature and humidity in an office on perceived air quality, SBS symptoms and performance.

UNLABELLED: Perceived air quality (PAQ), sick building syndrome (SBS) symptoms and performance of office work were studied in a real office space at three levels of air temperature and humidity and two levels of ventilation rate (20 degrees C/40%, 23 degrees C/50%, 26 degrees C/60% RH at 10 l s(-1) p(-1) outside air, and 20 degrees C/40% RH at 3.5 l s(-1) p(-1) outside air). Thirty female subjects participated in the experiment. They were exposed to each environmental condition for 280 min. Thermal comfort was maintained at different thermal environments by self-adjustment of clothing. The subjects performed simulated office work throughout each exposure and repeatedly marked a set of visual-analog scales to indicate their perception of environmental conditions and of the intensity of SBS symptoms at the time. The study confirmed the previously observed impact of temperature and humidity on perceived air quality and the linear correlation between acceptability and enthalpy. The impact on perceived air quality of decreasing the ventilation rate from 10 to 3.5 l s(-1) per person could be counteracted by a decrement of temperature and humidity from 23 degrees C/50% RH to 20 degrees C/40% RH. Performance of office work was not significantly affected by indoor air temperature and humidity. However, several SBS symptoms were alleviated when the subjects worked at low levels of air temperature and humidity, which implies that a longer term exposure to low indoor air temperature and humidity might help to improve the performance of office work. PRACTICAL IMPLICATIONS: The findings of this study indicate the importance of indoor air temperature and humidity on perceived air quality and SBS symptoms. In practice, the required ventilation rate for comfort and health should no longer be independent of indoor air temperature and humidity.

Adult↗
PubMed2004

[Relationship between absolute humidity and influenza prevalence in Odate and Akita cities, Akita Prefecture, in 2001 and 2002].

The dynamics of influenza viruses in relation to one meteorological factor, absolute humidity, was investigated. The number of influenza patients, absolute humidity, and isolation of influenza viruses were compared between Odate City the north and Akita City in central Akita Prefecture from 2001 to 2002. The results were as follows: 1) In both Odate and Akita cities, Influenza A (H1N1 and H3N2) and Influenza B (Victoria and Yamagata) viruses were isolated when absolute humidity ranged between 2.7 and 8.8 g/m3. 2) In Akita City in 2002, the influenza viruses were isolated in May (weeks 20 and 22), and the absolute humidity was below 9 g/m3, suggesting that the influenza season lasted until May in this year. 3) A correlation between absolute humidity and isolation of influenza viruses was observed, and the influenza prevalence may occur below 9 g/m3 of absolute humidity. 4) In Odate and Akita cities, the absolute humidity of 10 g/m3, a level at which 5% of influenza viruses can survive after six hours, was observed from January to June and October to December. 5) Influenza prevalence show differential occurrence by time and place. Therefore, further research is required to clarify the absolute humidity related to influenza prevalence.

Humans↗
PubMedDate not supplied

Relationship of symptomatology with closed chamber infrared thermometry and humidity in dry eyes.

PURPOSE: To evaluate the relationship of symptoms of dry eye with closed chamber infrared thermometry and humidity measurements. METHODS: The authors studied 54 patients (108 eyes) with dry eye disorders of different grades of clinical severity (mean age 35.75+/-14.37 years), 31 cases (62 eyes) with normal eyes (mean age 33.68+/-14.42 years), and 10 cases (20 eyes) with epidemic conjunctivitis (mean age 33.68+/-14.42 years). The symptoms and the clinical tests (Schirmer-1 test, fluorescein tear break up time, Lissamine green stain; closed chamber infrared thermometry and humidity) were used to establish the diagnosis of dry eyes. The closed chamber humidity difference was used to classify the groups of dry eye. RESULTS: The authors noted no temperature difference from closed to open eye position in dry eyes as compared to 0.10 +/- 0.00 degrees C difference in normal eyes and epidemic conjunctivitis. Four groups of cases were identified by difference in values of humidity: Group 1 = <0.9 relative humidity (RH)% to 1 RH%; Group 2 = >1 RH% to 1.5 RH%; Group 3 = >1.5 RH% to 2 RH %; and Group 4 = >2 RH%. The symptomatology was measured in the eyes using Oxford scale (0-4) and correlated with the humidity groups. The grading of symptoms with the humidity showed a statistically significant relationship (p<0.0001) in each group. The severity of the symptoms showed an increase in frequency and severity from Group 1 to Group 4, which was statistically significant (p<0.0001). The mean sum total of global symptomatology score was statistically significant (p<0.0001): 3.43 +/- 0.31 in Group 1, 4.65+/-0.42 in Group 2, 8.56 +/- 0.78 in Group 3, and 13.35+/-1.21 in Group 4. However, total symptomatology score in epidemic conjunctivitis did not show a statistically significant value (p=0.20). CONCLUSIONS: The closed chamber humidity and thermometry measurements showed statistical correlation in all four groups of dry eyes to total mean symptomatology score (p<0.001) and showed an increase in value with increasing severity of symptoms. However, all individual symptoms fail to show any conclusive relationship.

Adolescent↗
PubMed2005

[The influence of the initial humidity of balneological peat on its pharmacological features].

The viscosity of balneological peat got special meaning according to its thermical features. Until now, there has been no answer on the question in how far balneological peat, which is prepared with different degrees of humidity, can vary the pharmacological character. Aim of this work was, on the one hand, to examine which initial degree of peat-humidity is necessary to get the wished viscosity in therapy when diluted with water. On the other hand, how far the pharmacological character of balneological is influenced by the initial degree of humidity. From peat, with initial different degrees of humidity, balneological peat is prepared, fulfilling the demands of the Quentin-Test and therefore the necessary consistence for therapy. Here in this work the in-vitro effect of aqueous peat extract (APE) on the spontaneous contractile activity of the smooth muscle fibres of guinea-pig stomachs was examined. The APE used got initial different degrees of humidity. It was found out, that the ability of peat according to a new water-uptake, with a initial humidity under 60%, was clearly reduced. Because of the reduced water content of balneological peat its thermical features were deteriorated. This goes for peat with a humidity factor < 60%. First, with the Quentin-Test, showing the optimal viscosity of peat before medical use, you can also make statements according its ability of maximum uptake of water, meaning the ability taking up water until it becomes gel-like. Second, the results show that the initial humidity of peat got no influence on the pharmacological features.

Animals↗
PubMed1983

Absolute humidity measurement utilizing alpha-ray absorption.

Changes in air density due to humidity were measured by a scintillation detector with alpha-particles. The distance between the scintillator and an alpha-ray source of 241 Am, 3.7 MBq (100 microCi), was fixed at 25 mm which was a little shorter than the range of alpha-particles from the source. The measured absolute humidities were in a range of 7.9 g/m3 to 52.2 g/m3 at temperatures of 35 degrees C and 45 degrees C and under atmospheric pressure. The counting rate of alpha-particles in an absolute humidity of 31.7 g/m3 (80% in relative humidity) at 35 degrees C increased 28% compared with that in dry air. From experimental results and theoretical calculation, the counting rate difference between humid air and dry air was shown to be almost proportional to the absolute humidity in air. The absolute humidity can be measured with an accuracy of +/- 3 g/m3, that is +/- 5% in relative humidity at 45 degrees C.

Alpha Particles↗
PubMedDate not supplied

Influence of environment on airsacculitis: effects of relative humidity and air temperature on broilers infected with Mycoplasma synoviae and infectious bronchitis.

Mycoplasma synoviae (MS) obtained from broiler chickens condemned for airsacculitis was used to determine the influence of air temperature and relative humidity on the severity of airsacculitis produced experimentally. Infectious bronchitis virus was administered to 3-week-old broilers 5 days before aerosol exposure to MS broth cultures, producing extensive airsacculitis within 21-day study periods. High (31-32 C), medium (19-24 C), and low (7-10 C) air temperatures were studied in conjection with high (75-90%), medium (38-56%), and low (23-26%) relative humidities. Airsacculitis was most extensive (45%) at low temperatures regradless of high or medium humidity. The incidence of airsacculitis was greater (39%) at low humidity than at high humidity (17%) when air temperatures were medium. At high temperature, the trend was toward more airsacculitis (12%) at high humidity than (5%) at low humidity. However, the effect of cold air temperature was more dominant than the effect of relative humidity.

Aerosols↗
PubMed2006

Humidity-induced restructuring of the calcite surface and the effect of divalent heavy metals.

The composition and topography of calcite 10114 cleavage surfaces, with and without exposure to divalent metals, have been investigated as a function of relative humidity. Atomic force microscopy (AFM) was used to understand topographical changes on the calcite surface due to the presence of divalent metal and exposure to different humid environments. Ion scattering spectroscopy (ISS) was used to determine the composition of the near and outermost surface of the calcite after exposure to Cd and Pb and before exposure to the varying humidity conditions. In general, the extent of topographical changes observed on the calcite surface increased with the humidity level, though the initial step density of the cleaved calcite surface affects the extent of surface restructuring. Pretreatment of the calcite surface with aqueous divalent Pb prior to humidity exposure did not appear to alter the humidity-induced structural changes that occurred on the calcite surface. In contrast, calcite pretreated with divalent Cd showed little topographical change following exposure to high humidity. The results suggest that while Pb forms surface precipitates on the calcite surface, Cd exhibits a stronger interaction with the step edges of the calcite surface, which inhibits the ability of the calcite surface to restructure when exposed to a high relative humidity environment.

Journal Article↗
PubMed2001

[Endonasal temperature and humidity profile after exposure to various climate-controlled inspiratory air].

BACKGROUND AND OBJECTIVE: The nose as the first segment of the upper respiratory tract is exposed to different climatic conditions of the ambient air. The purpose of this study was to determine whether nasal air conditioning of ambient air is influenced by a short-term exposure to air of different climatic conditions. PATIENTS AND METHODS: Fifteen healthy volunteers were enclosed into the study. A miniaturised humidity sensor and thermocouple was used for detection of humidity and airway temperature at three detection sites within the anterior nasal cavity. Both parameters were measured at the end of inspiration during breathing of ambient air after exposure to cold dry air, "normal" ambient air, and warm humid air for 10 minutes. RESULTS: The end-inspiratory intranasal humidity during breathing of ambient air increased at all locations within the nose when the temperature and humidity of the exposure condition increased. At the most anterior detection site, the effect of increase in humidity after exposure to the different climatic conditions was the most pronounced. The increase in intranasal temperature had no relation to the different climatic conditions during the short-term exposure. CONCLUSIONS: The results suggest that nasal humidification in ambient air can be influenced by short-term exposure to air of extreme temperature and humidity prior to breathing of ambient air.

Adult↗