Effect of cold and warm dry air hyperventilation on canine airway blood flow

Tracheobronchial blood flow increases with cold air hyperventilation in the dog. The present study was designed to determine whether the cooling or the drying of the airway mucosa was the principal stimulus for this response. Six anesthetized dogs (group 1) were subjected to four periods of eucapnic hyperventilation for 30 min with warm humid air [100% relative humidity (rh)], cold dry air (-12 degrees C, 0% rh), warm humid air, and warm dry air (43 degrees C, 0% rh). Five minutes before the end of each period of hyperventilation, tracheal and central airway blood flow was determined using four differently labeled 15-micron diam radioactive microspheres. We studied another three dogs (group 2) in which 15- and 50-micron microspheres were injected simultaneously to determine whether there were any arteriovenous communications in the bronchovasculature greater than 15 micron diam. After the last measurements had been made, all dogs were killed, and the lungs, including the trachea, were excised and blood flow to the trachea, left lung bronchi, and parenchyma was calculated. Warm dry air hyperventilation produced a consistently greater increase in tracheobronchial blood flow (P less than 0.01) than cold dry air hyperventilation, despite the fact that there was a smaller fall (6 degrees C) in tracheal tissue temperature during warm dry air hyperventilation than during cold dry air hyperventilation (11 degrees C), suggesting that drying may be a more important stimulus than cold for increasing airway blood flow. In group 2, the 15-micron microspheres accurately reflected the distribution of airway blood flow but did not always give reliable measurements of parenchymal blood flow.     

Evaluation of the desiccation tolerance of blastospores of Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) using a lab-scale, air-drying chamber with controlled relative humidity

The stabilization of living microbial agents for use as biological control agents is often accomplished through desiccation. Our air-drying studies with the entomopathogenic fungus Paecilomyces fumosoroseus have shown that the relative humidity (RH) of the drying air significantly affects the desiccation tolerance and the storage stability of blastospores. Drying air with a RH of more than 40% supported significantly higher rates of initial blastospore survival (68-82%) after drying compared to drying with lower relative humidity air. Drying air with a RH above 50% improved the shelf-life of the air-dried blastospore preparations. Adjustment of the pH or replacement of the spent medium with deionized water (d-H₂O) in the blastospore suspension had no significant impact on blastospore desiccation tolerance or storage stability. We have developed and describe a lab-scale, air-drying chamber that delivers air flow over the sample and that can be operated at controlled relative humidity.     

The paradox of higher light tolerance during desiccation in rare old forest cyanolichens than in more widespread co-occurring chloro- and cephalolichens

? Desiccation tolerance was quantified in four cyanolichens (Lobaria hallii, Lobaria retigera, Lobaria scrobiculata, Pseudocyphellaria anomala), one cephalolichen (Lobaria pulmonaria) and one chlorolichen (Platismatia glauca) from xeric and mesic, open and closed North American boreal forests. ? These sympatric epiphytes were exposed to 0%, 33%, 55% and 75% relative humidity with or without medium light (200?μmol?m(-2) s(-1) ) for 7?d. Permanent and temporary photoinhibitory damage was recorded as viability measures. ? All species tolerated well the drying in darkness, but L.?hallii and L.?retigera, associated with a very humid climate, showed minor damage at the hardest drying (silica gel). Simultaneous exposure to medium light severely aggravated the drying damage at all relative humidity levels. Combined drying-light exposure was particularly devastating for the widespread chloro- and cephalolichens, whereas cyanolichens, including rare old forest species, were fairly resistant. ? The ability to recover after combined drying-light stress (this study) correlated positively with increasing species-specific water holding capacities (from the literature). Cyanolichens, depending on liquid water and large internal water storage, probably require strong drying-light resistance to handle long periods between hydration events, whereas chlorolichens can regularly maintain their photosynthetic apparatus during frequent and rapid activation by humid air on clear mornings.     

Effect of inspired air conditions on exercise-induced bronchoconstriction and urinary CC16 levels in athletes

Injury to the airway epithelium has been proposed as a key susceptibility factor for exercise-induced bronchoconstriction (EIB). Our goals were to establish whether airway epithelial cell injury occurs during EIB in athletes and whether inhalation of warm humid air inhibits this injury. Twenty-one young male athletes (10 with a history of EIB) performed two 8-min exercise tests near maximal aerobic capacity in cold dry (4°C, 37% relative humidity) and warm humid (25°C, 94% relative humidity) air on separate days. Postexercise changes in urinary CC16 were used as a biomarker of airway epithelial cell perturbation and injury. Bronchoconstriction occurred in eight athletes in the cold dry environment and was completely blocked by inhalation of warm humid air [maximal fall in forced expiratory volume in 1 s = 18.1 ± 2.1% (SD) in cold dry air and 1.7 ± 0.8% in warm humid air, P < 0.01]. Exercise caused an increase in urinary excretion of CC16 in all subjects (P < 0.001), but this rise in CC16 was blunted following inhalation of warm humid air [median CC16 increase pre- to postchallenge = 1.91 and 0.35 ng/μmol in cold dry and warm humid air, respectively, in athletes with EIB (P = 0.017) and 1.68 and 0.48 ng/μmol in cold dry and warm humid air, respectively, in athletes without EIB (P = 0.002)]. The results indicate that exercise hyperpnea transiently disrupts the airway epithelium of all athletes (not only in those with EIB) and that inhalation of warm moist air limits airway epithelial cell perturbation and injury.     

胡萝卜吸附式低温干燥特性的研究

对胡萝卜吸附式低温干燥过程的干燥特性进行了试验研究。考察了干燥气体 (空气 )的湿度和风量以及物料粒度对胡萝卜干燥特性和复水比的影响 ,得到形状相似的干燥曲线 ,用自定义最小二乘法拟合均能获得较好的结果。结果表明 :吸附式低温干燥过程可使被干燥物料达到超干水平 (含水率 <5 % ) ;增加干燥气体流量对干燥过程进行有利 ,当气体流量从 2 0 0L/h增加到 4 0 0L/h时 ,胡萝卜含水率从 4 1 13%降低到 34 93% ;被干燥物料颗粒大小和形状对干燥过程有显著影响 ;经过吸附式干燥后的胡萝卜色泽鲜艳 ,无褐变 ,外表品质优于热风干燥。吸附式低温干燥后胡萝卜的复水比 (6 5 2 )显著高于热风干燥 (1 78)。     

The potential for establishment of axial temperature profiles during solid-state fermentation in rotating drum bioreactors

The mixing and heat transfer phenomena within rotating drum bioreactors (RDBs) used for solid-state fermentation processes are poorly studied. The potential for the establishment of axial temperature gradients within the substrate bed was explored using a heat transfer model. For growth of Aspergillus oryzae on wheat bran within a 24 L RDB with air at a superficial velocity of 0.0023 m s(-1) and 15% relative humidity, the model predicts an axial gradient between the air inlet and outlet of 2 degrees C during rapid growth, compared to experimental axial temperature gradients of between 1 and 4 degrees C. Undesirably high temperatures occur throughout the bed under these operating conditions, but the model predicts that good temperature control can be achieved using humid air (90% relative humidity) at superficial velocities of 1 m s(-1) for a 204 L RDB. For a 2200 L RDB, good temperature control is predicted with superficial velocities as low as 0.4 m s(-1) with the airflow being switched from 90% to 15% relative humidity whenever the temperature at the outlet end of the drum exceeds the optimal temperature for growth. This work suggests that significant axial temperature gradients can arise in those RDBs that lack provision for axial mixing. It is therefore advisable to use angled lifters within RDBs to promote axial mixing.     

Longitudinal distribution of canine respiratory heat and water exchanges

We assessed the longitudinal distribution of intra-airway heat and water exchanges and their effects on airway wall temperature by directly measuring respiratory fluctuations in airstream temperature and humidity, as well as airway wall temperature, at multiple sites along the airways of endotracheally intubated dogs. By comparing these axial thermal and water profiles, we have demonstrated that increasing minute ventilation of cold or warm dry air leads to 1) further penetration of unconditioned air into the lung, 2) a shift of the principal site of total respiratory heat loss from the trachea to the bronchi, and 3) alteration of the relative contributions of conductive and evaporative heat losses to local total (conductive plus evaporative) heat loss. These changes were not accurately reflected in global measurements of respiratory heat and water exchange made at the free end of the endotracheal tube. Raising the temperature of inspired dry air from frigid to near body temperature principally altered the mechanism of airway cooling but did not influence airway mucosal temperature substantially. When local heat loss was increased from both trachea and bronchi (by increasing minute ventilation), only the tracheal mucosal temperature fell appreciably (up to 4.0 degrees C), even though the rise in heat loss from the bronchi about doubled that in the trachea. Thus it appears that the bronchi are better able to resist changes in airway wall temperature than is the trachea. These data indicate that the sites, magnitudes, and mechanisms of respiratory heat loss vary appreciably with breathing pattern and inspired gas temperature and that these changes cannot be predicted from measurements made at the mouth. In addition, they demonstrate that local heat (and presumably, water) sources that replenish mucosal heat and water lost to the airstream are important in determining the degree of local airway cooling (and presumably, drying).     

Mathematical modeling of an aqueous film coating process in a Bohle Lab-Coater, Part 1: Development of the model

The purpose of this study was to develop a model to predict (1) air and product temperatures, (2) product moisture, and (3) air humidity during an aqueous coating process using a Bohle Lab-Coater. Because of the geometrical properties and the airflow, the drum of the Bohle Lab-Coater can in principle be divided into 2 zones of equal size—the drying and the spraying zones. For each zone, 4 balance equations could be set up describing the change of the air humidity, the product moisture, the enthalpy of the air, and the enthalpy of the product in each zone. For this purpose, knowledge regarding heat and mass transfer and also the motion of the tablets in drums was used. Based on the considerations of the heat and mass transfer, a set of first-order coupled ordinary differential equations (ODEs) was developed. This set of ODEs can be solved numerically. In this part, the development of the model is described in detail, whereas the application of the model can be found in part 2.     

Tracheobronchial and upper airway blood flow in dogs during thermally induced panting

Tracheobronchial blood flow increases two- to fivefold in response to isocapnic hyperventilation with warm dry or cold dry air in anesthetized, tracheostomized dogs. To determine whether this response is governed by central nervous system thermoregulatory control or is a local response to the drying and/or cooling of the airway mucosa, we studied eight anesthetized spontaneously breathing dogs in a thermally controlled chamber designed so that inspired air temperature, humidity, and body temperature could be separately regulated. Four dogs breathed through the nose and mouth (group 1), and four breathed through a short tracheostomy tube (group 2). Dogs were studied under the following conditions: 1) a normothermic control period and 2) two periods of hyperthermia in which the dogs panted with either warm 100% humidified air or warm dry (approximately 10% humidified) air. Radiolabeled microspheres (15 +/- 3 micron diam) were injected into the left ventricle as a marker of nasal, lingual, and tracheobronchial blood flow. After the final measurements, the dogs were killed and tissues of interest excised. Results showed that lingual and nasal blood flow (ml.min-1.g-1) increased during panting (P less than 0.01) in both groups and were not affected by the inspired air conditions. In group 1, tracheal mucosal blood flow barely doubled (P less than 0.01) and bronchial blood flow did not change during humid and dry air panting. In group 2, there was a sevenfold increase in tracheal mucosal and about a threefold increase in bronchial blood flow (P less than 0.01), which was only observed during dry air panting.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypertonic aerosol inhalation does not alter central airway blood flow in dogs

Tracheobronchial blood flow in dogs increases with cold or dry air hyperventilation, possibly as a result of airway drying leading to increased osmolarity of airway surface fluid. This study was designed to examine whether administration of aerosols of various tonicity to alter airway surface fluid osmolarity would induce similar blood flow changes. Tracheobronchial blood flow was measured by the radioactive microsphere technique in six anesthetized dogs ventilated with warm humid air (100% relative humidity) for 15 min (period 1), air containing ultrasonically nebulized saline aerosol (1,711 mosmol/kg) for 3 min (period 2) and 12 min (period 3), and the same aerosol at a higher nebulizer output for a further 3 min (period 4). Between periods 3 and 4, the dogs were ventilated with warm humid air for 30 min to reestablish base-line conditions. In another five dogs, measurements were made after 30 min of ventilation with 1) warm humid air, 2) isotonic saline aerosol, 3) warm humid air, 4) distilled water aerosol (3 dogs), and hypertonic saline aerosol (2 dogs). After the last measurement was made, each dog was killed, the trachea and major bronchi were excised, and blood flow was calculated. No change in blood flow was found during any period of aerosol inhalation. The osmolar load imposed on the airways was estimated and was similar to that occurring during cold or dry air hyperventilation. These data suggest that increasing osmolarity of airway surface fluid does not explain the blood flow changes seen during hyperventilation of cold or dry air.     

Efficacy of humidity retention bags for the reduced adsorption and improved cleaning of tissue proteins including prion-associated amyloid to surgical stainless steel surfaces

Increasing drying time adversely affects attachment of tissue proteins and prion-associated amyloid to surgical stainless steel, and reduces the efficacy of commercial cleaning chemistries. This study tested the efficacy of commercial humidity retention bags to reduce biofouling on surgical stainless steel and to improve subsequent cleaning. Surgical stainless steel surfaces were contaminated with ME7-infected brain homogenates and left to dry for 15 to 1,440 min either in air, in dry polythene bags or within humidity retention bags. Residual contamination pre/post cleaning was analysed using Thioflavin T/SYPRO Ruby dual staining and microscope analysis. An increase in biofouling was observed with increased drying time in air or in sealed dry bags. Humidity retention bags kept both protein and prion-associated amyloid minimal across the drying times both pre- and post-cleaning. Therefore, humidity bags demonstrate a cheap, easy to implement solution to improve surgical instrument reprocessing and to potentially reduce associated hospital acquired infections.     

Prevention of abnormal pulmonary mechanics in the postmortem guinea pig lung

Severe postmortem bronchoconstriction has been shown previously in guinea pig lungs and linked to pulmonary blood loss during exsanguination (Lai et al., J. Appl. Physiol. 56: 308-314, 1984). To reexamine this phenomenon we measured postmortem airway function in anesthetized open-chest guinea pigs after sudden circulatory arrest. Animals were divided into 4 groups of 10 and ventilated for 15 min postmortem with different gases: 1) room air, 2) conditioned air, 3) dry 5% CO2-21% O2-74% N2, and 4) conditioned 5% CO2-21% O2-74% N2. In room air-ventilated lungs there was a 50% decrease in dynamic compliance (Cdyn) by 15 min and marked gas trapping compared with control lungs. Conditioning the room air did not attenuate these changes, but when 5% CO2 was added to the conditioned postmortem inspirate, gas trapping was eliminated and the fall in Cdyn was almost abolished. Ventilation with a dry 5% CO2 gas mixture at room temperature resulted in a 31% fall in Cdyn at 15 min but no gas trapping. We conclude that marked abnormalities of airway function occur postmortem in room air-ventilated guinea pig lungs in the absence of pulmonary blood loss. The changes are mainly due to airway hypocarbia, a known cause of bronchoconstriction, but a reduction in Cdyn can also occur if there is marked airway cooling and drying. Acute postmortem airway dysfunction can be prevented in the guinea pig by maintaining normal airway gas composition.     

Whole-body plethysmography, does it measure tidal volume of small animals?

A whole-body plethysmograph was used for mice. The increase in pressure caused by each inhalation was equivalent to the increase that could be calculated to result from heating and humidification of the inhaled air. However, comprehending that a drop in temperature and humidity would cause an abrupt pressure decline during exhalation was difficult. Pressure changes in the plethysmograph were also studied with an artificial chest, modeling the respiratory mechanics, but without the "inhaled" air being heated or humidified. The "chest" consisted of a metal bellows oscillated by a stepper motor 25 to 175 times per minute. Hereby air (0.05 to 0.20 mL) moved in and out of the bellows. The air passed through a polyethylene tube, the length of which was proportional to "airway resistance" and varied from 5 to 35 cm. It was found that the pressure oscillation was affected not only by "tidal volume" of the mechanical chest but also by "respiratory rate" and by "airway resistance." We concur with previous investigators that the plethysmograph pressure reflects alveolar pressure and that fluctuations cannot be explained by changes in temperature and humidity. Accordingly, tidal volume can only be qualitatively and not quantitatively assessed.     

Effects of wetting on the persistence of quiescent conidia of Isaria fumosorosea

Quiescent conidia of Isaria fumosorosea were submitted to various wetting–drying cycles under different regimes of temperature and air humidity. Germination and viability of conidia collected on cultures freshly host-passed (P2) were not affected at 25 °C during five cycles at increasing wet phase duration (2–12 h per daily cycle) under any moisture conditions (13–86% RH). Infectivity levels remained stable, but mortality was slightly postponed. In vitro-cultured inocula (P5) were significantly affected after only one cycle at higher air humidity (75 and 86% RH) and temperature (35 and 40 °C). The persistence of I. fumosorosea conidia suspended in water soluble extracts of leaf surfaces (corn and cabbage) confirmed the better persistence of P2 conidia and the relatively higher detrimental effect of lower air humidity conditions when combined with moderate temperatures. Quiescent conidia deposited in situ on potted plants of cabbage showed a higher persistence on wet foliage and on foliage submitted to wetting–drying cycles, than on dry foliage. These results underline that constraints prevailing in targeted environments and ecological fitness of fungal isolates have to be taken into account for assessing microbial control strategies.     

冻干松茸包装条件的选择

冻干松茸吸水能力较强,要控制水分含量在7%以下,包装条件的选择成为比较重要的工艺环节.实验通过选择空气相对湿度、包装材料、干燥剂等包装条件,来确定最佳包装环境.     

Effect of air humidity on spinability and transport capacity of canine airway secretions

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T degrees:20 degrees C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m3 air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m3 air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p less than 0.01) lower (range: 0.59-0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70-1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p less than 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.     

Prokaryotic aminopeptidase activity along a continuous salinity gradient in a hypersaline coastal lagoon (the Coorong, South Australia)

The relation between climatic parameters (relative air humidity) and the water activity of the Urmia Sea water determines the possible maximum evaporation of the lake. Using the Pitzer thermodynamic approach, the activity of the Urmia Lake water during evaporation was calculated and compared to the present relative air humidity above the water. Present climatic conditions allow the Urmia Sea water to evaporate down to water with activity of 0.55, corresponding to the lowest air humidity measured over the lake. This water activity falls in the range of halite precipitation, while carnalite precipitation starts at somewhat lower (a H₂O = 0.499) point. Our dynamic model predicts that for air humidity as low as 55% (reflecting present climate conditions), the Urmia Sea level may drop to as low as 1270 m (i. e., 1270 m above mean sea level). At that point, the lake water volume will have a volume of 11 km³. For the sake of comparison, at the beginning of 1990, the level of the lake was 1275 m, its volume was 25 km³, and its surface area was 5145 km².     

镇江内江湿地不同演替阶段植物群落小气候日动态

2005年5月,选择镇江内江湿地具有代表性的裸地、虉草群落和芦苇群落,分别代表植被群落的不同演替阶段,测定不同群落、不同层次的光照强度、气温、土温和空气相对湿度,研究其植物群落小气候的日动态.结果表明,随演替由裸地到虉草群落到芦苇群落进行,群落内光照强度、气温和土壤温度均明显降低,日变幅减小.其中,日均光照强度由1 204.7 μmol·m^-2·s^-1降至141.28 μmol·m^-2·s^-1,日均变幅由1 126μmol·m^-2·s^-1降至265 μmol·m^-2·s^-1;日均气温由32.2 ℃降至24.9 ℃,日均变幅由12.75 ℃降至4.8 ℃;日均土温由21.83 ℃降至19.47 ℃,日均变幅由4.5 ℃降至2.1 ℃.群落内空气相对湿度明显升高(由58.95%增至87.3%）,变幅减小(由29.75%降至5.15%）.生境具有早期的开放性和后期的封闭性,小气候环境朝着更为阴、凉、湿的环境变化,且波动性减弱,稳定性增强.各群落内的光强、气温、湿度及土温之间均存在一定相关,但不同演替阶段各因子间相关程度各异.     

Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers

Aims: To compare an ultra‐rapid hand dryer against warm air dryers, with regard to: (A) bacterial transfer after drying and (B) the impact on bacterial numbers of rubbing hands during dryer use. Methods and Results: The Airblade? dryer (Dyson Ltd) uses two air ‘knives’ to strip water from still hands, whereas conventional dryers use warm air to evaporate moisture whilst hands are rubbed together. These approaches were compared using 14 volunteers; the Airblade? and two types of warm air dryer. In study (A), hands were contaminated by handling meat and then washed in a standardized manner. After dryer use, fingers were pressed onto foil and transfer of residual bacteria enumerated. Transfers of 0–10⁷ CFU per five fingers were observed. For a drying time of 10 s, the Airblade? led to significantly less bacterial transfer than the other dryers (P < 0·05; range 0·0003–0·0015). When the latter were used for 30–35 s, the trend was for the Airblade to still perform better, but differences were not significant (P > 0·05, range 0·1317–0·4099). In study (B), drying was performed ± hand rubbing. Contact plates enumerated bacteria transferred from palms, fingers and fingertips before and after drying. When keeping hands still, there was no statistical difference between dryers, and reduction in the numbers released was almost as high as with paper towels. Rubbing when using the warm air dryers inhibited an overall reduction in bacterial numbers on the skin (P < 0·05). Conclusions: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing. Significance and Impact of the Study: The Airblade? was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands.     

Water loss from cut grass with special reference to hay-making

Water loss from cut grass was studied to determine factors limiting the drying process. An apparatus, used to measure water loss at 28±1°C from blotting paper and from leaves and stem internodes of cocksfoot, consisted of four channels in which air speed was controlled at 25–80 cm s^-1 and relative humidity at 7–68%. The maximum rate of water loss from wet blotting paper was 10500 mg water dm^-2 h^-1 but from leaves and stem internodes supplied with water it was less than 250 mg dm^-2 h^-1. The rate of loss from both plant specimens and blotting paper was linearly related to the vapour pressure differences between the specimen and the surrounding air but was not increased when air speed was changed from 40 to 80 cm s^-1. Grass specimens supplied with water had lower rates of water loss than wet blotting paper because of tissue resistances which were calculated for (a) untreated leaf and stem specimens, (b) rubbed leaves, (c) cut leaves, (d) leaves exposed to steam for 60 s. Treatments (b)-(d) greatly reduced tissue resistances. The rates of drying of leaves and stem internodes not supplied with water changed only slightly in response to faster air speeds but were significantly increased by treatments (b), (c), (c_s) (split stems), (d) and (e) (exposure to petroleum vapour for 60 s). The most effective treatments trebled the drying rates of leaves and increased the drying rates of stem internodes by 10 times. Reductions in relative humidity had little effect on drying rate following treatments (a), (b), (c) and (d), but when treatments (c_s) and (e) were given, additional significant increases in drying rates were obtained when the relative humidity was reduced. Grass specimens given the most effective treatments and dried under the most favourable conditions did not utilize the full drying capacity of the environment, for the rates of water loss from these specimens were at least three times lower than those from wet blotting paper. The results indicate that high rates of drying could be achieved at 28 ^oC or similar temperatures if practical treatments were developed to remove or greatly reduce the high resistance to water loss in cut grass.