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A recent study was conducted to compare five fit test methods for screening out poor-fitting N95 filtering-facepiece respirators. Eighteen models of NIOSH-certified, N95 filtering-facepiece respirators were used to assess the fit test methods by using a simulated workplace protection factor (SWPF) test. The purpose of this companion study was to investigate the effect of subject characteristics (gender and face dimensions) and respirator features on respirator fit. The respirator features studied were design style (folding and cup style) and number of sizes available (one size fits all, two sizes, and three sizes). Thirty-three subjects participated in this study. Each was measured for 12 face dimensions using traditional calipers and tape. From this group, 25 subjects with face size categories 1 to 10 tested each respirator. The SWPF test protocol entailed using the PortaCount Plus to determine a SWPF based on total penetration (face-seal leakage plus filter penetration) while the subject performed six simulated workplace movements. Six tests were conducted for each subject/respirator model combination with redonning between tests. The respirator design style (folding style and cup style) did not have a significant effect on respirator fit in this study. The number of respirator sizes available for a model had significant impact on respirator fit on the panel for cup-style respirators with one and two sizes available. There was no significant difference in the geometric mean fit factor between male and female subjects for 16 of the 18 respirator models. Subsets of one to six face dimensions were found to be significantly correlated with SWPFs (p < 0.05) in 16 of the 33 respirator model/respirator size combinations. Bigonial breadth, face width, face length, and nose protrusion appeared the most in subsets (five or six) of face dimensions and their multiple linear regression coefficients were significantly different from zero (p < 0.05). Lip length was found in only one subset. The use of face length and lip length as the criteria to define the current half-facepiece respirator fit test panel may need to be reconsidered when revising the panel. Based on the findings from this and previous studies, face length and face width are recommended measurements that should be used for defining the panel for half-facepiece respirators.
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The spatial and temporal variations of soil respiration were studied from May 2004 to June 2005 in a C3/C4 mixed grassland of Japan. The linear regression relationship between soil respiration and root biomass was used to determine the contribution of root respiration to soil respiration. The highest soil respiration rate of 11.54 micro mol m-2 s-1 was found in August 2004 and the lowest soil respiration rate of 4.99 micro mol m-2 s-1 was found in April 2005. Within-site variation was smaller than seasonal change in soil respiration. Root biomass varied from 0.71 kg m-2 in August 2004 to 1.02 in May 2005. Within-site variation in root biomass was larger than seasonal variation. Root respiration rate was highest in August 2004 (5.7 micro mol m-2 s-1) and lowest in October 2004 (1.7 micro mol m-2 s-1 ). Microbial respiration rate was highest in August 2004 (5.8 micro mol m-2 s-1 ) and lowest in April 2005 (2.59 micro mol m-2 s-1 ). We estimated that the contribution of root respiration to soil respiration ranged from 31% in October to 51% in August of 2004, and from 45% to 49% from April to June 2005.
The potential capacity of soil to sequester carbon in response to global warming is strongly regulated by the ratio of rhizosphere respiration to respiration by soil microbial decomposers, because of their different temperature sensitivities. To quantify relative contributions of rhizosphere respiration to total soil respiration as influenced by forest stand development, we conducted a trenching study in two larch (Larix gmelini (Rupr.) Rupr.) plantations, aged 17 and 31 years, in northeastern China. Four plots in each plantation were randomly selected and trenched in early May 2001. Soil surface CO2 effluxes both inside and outside the plots were measured from May 2001 to August 2002. Soil respiration (i.e., the CO2 effluxes outside the trenched plots) varied similarly in the two plantations from 0.8 micromol m(-2) s(-1) in winter to 6.0 micromol m(-2) s(-1) in summer. Rhizosphere respiration (i.e., CO2 efflux outside the trenched plots minus that inside the plots) varied from 0.2 to 2.0 micromol m(-2) s(-1) in the old forest and from 0.3 to 4.0 micromol m(-2) s(-1) in the young forest over the seasons. Rhizosphere respiration, on average, accounted for 25% of soil respiration in the old forest and 65% in the young forest. Rhizosphere and soil respiration were significantly correlated with soil temperature but not with soil water content. We conclude that the role forests play in regulating climate change may depend on their age.
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BACKGROUND: In 1995 the National Institute for Occupational Safety and Health issued new rules for personal respirators. All nine new respirator categories are authorized in health care facilities for the prevention of the transmission of tuberculosis (TB). The new N95 respirator category is the most frequently used for this purpose. Data are presented on their efficiency for collecting TB-size bacteria and their potential for reaerosolizing collected bacteria. METHODS: All measurements of bacterial penetration were performed with dynamic aerosol size spectrometers at flow conditions corresponding to normal wear and respirator certification conditions. The reaerosolization tests were performed at conditions ranging from normal breathing to violent coughing or sneezing. RESULTS: The tested N95 respirators collected 0.1 to 0.3 microm particles with efficiencies of 95% or higher, as specified by the regulations. TB-size bacteria of 0.8 microm and larger, however, were collected with 99.5% or higher efficiencies; that is, the penetration of these bacteria through the filter material was 0.5% or less, much less than the required maximum penetration of 5% for the smaller particle sizes. No bacteria were reaerosolized during normal exhalation. Some reaerosolization (0.1% or less) was observed only at low humidity and extremely high air flow through the respirator, corresponding to violent coughing or sneezing. CONCLUSIONS: The filter materials of N95 respirators provide good protection against TB bacteria. Thus, a significant number of bacteria can enter the respirator-wearer's breathing space only through spaces where the respirator inadequately seals to the wearer's face. Reentrainment and reaerosolization of mycobacteria is not a problem when normal work practices are observed in health care facilities.
These studies investigating the difference between controlled respiration performed by manual technique and controlled respiration applied by means of a respirator during general anaesthesia, and assessing the influence of these methods on the immediate post-operative condition of the patient were carried out on 75 patients during abdominal operations. Gasometric tests in arterial blood were performed before premedication, at intervals of 30 min from the beginning of operation, and 10 min. after the removal of the endotracheal tube. Controlled respiration with a respirator is a more favourable method of pulmonary ventilation during general anaesthesia given for a long-lasting surgical operation. The manual technique of controlled respiration leads to respiratory alkalosis. The best results were obtained using a respirator with inspiratory volume of 10 ml/kg and respiratory frequency 10/min., which ensured normocapnia. It was observed that oxygenation of arterial blood was reduced postoperatively in all patients but the value of PaO2 was the lowest in patients on manual controlled respiration. Disturbances in acid-base balance and oxygenation had an unfavourable effect and delayed the regaining of consciousness.
Root system architecture partially results from meristem activities, which themselves depend on endogenous and environmental factors, such as O2 depletion. In this study, meristem respiration and growth was measured in the root systems of three Prunus persica (L.) Batsch seedlings. The spatial distribution of meristem respiration within the root system was described, and the relationship between the respiration rates and meristem radii was analysed, using a model of radial O2 diffusion and consumption within the root. Histological observations were also used to help interpret the results. Respiration rates were linearly correlated to the root growth rates (rho 2 = 0.9). Respiration reached values greater than 3.5 x 10(-13) mol O2 s-1 for active meristems. The taproot meristem consumed more O2 than the rest of the entire root system meristems. Similarly, the first order lateral meristems used more O2 than the second order ones. A near hyperbolic relationship between respiration rates and meristem radii was observed. This can be explained by a model of radial O2 diffusion and consumption within the root. Therefore, only one maximum potential respiration rate and one O2 diffusion coefficient was estimated for all the meristems.
In Proton Medical Research Center (PMRC), we have performed the respiration-gated irradiation for treating the tumor in the body trunk. In the conventional method, patients must hold their expiration during CT scanning. The phase of holding expiration is different from the end-expiration phase. This results in difference of anatomical location in the body between CT scanning and the respiration-gated irradiation. For the sake of highly-accurate irradiation, a respiration gated CT scanning system is introduced. In case of natural respiration, it has been difficult to achieve the gated CT scanning because a stable period of end-expiratory is not so long as CT scanning time (1 second in our case). In this study, we developed a guided respiration method, which leads a patient to maintain the end-expiratory phase during required time. The respiration gated CT scanning is performed by using this. The phase of the acquired CT image can be approximated to that of respiration-gated irradiation.
A study was made of the characteristics of respiration recorded during the use of a respirator for preparing hypoxic hypercapnic mixtures as compared to the use of an additional "dead" space. In both cases, there was a significant increase of total ventilation, largely at the expense of respiration deepening. However, during respiration via a respiratory mask, the increase of the minute respiratory volume was accompanied by a rise of alveolar ventilation whereas during respiration via the ADS, alveolar ventilation dropped. Hyperventilation did not entail CO2 washing out from the blood and hypocapnia development during respiration via the mask and ADS. The differences revealed may appear helpful for respiration training at the hospital. In this case, an appropriate outfit should be sorted out for each patient on an individual basis.
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1. The dependence of the net transport of Na(+) and K(+) by rat liver on the respiration has been determined by incubating slices in the presence of varying concentrations of respiratory inhibitors. 2. Neither the rate of net transport nor the total amount of each ion transported was inhibited unless the rate of endogenous respiration was decreased below a critical value of about 330mmol of O(2)/h per kg of protein (i.e. 50% of the total endogenous respiration). 3. The uninhibited rate of respiration could be varied over a twofold range (380-770mmol of O(2)/h per kg of protein) by the use of different substrates, but the critical value for the onset of transport inhibition was quite constant (290-360mmol/h per kg of protein) under these different conditions. 4. Slices incubated at 38 degrees C without inhibitors showed an increase of their ATP content and the concentration ratio ATP/ADP. The final ATP content and concentration ratio, ATP/ADP, of slices treated with different concentrations of inhibitors were closely related to the rate of respiration. 5. The increased ATP content of the control slices during incubation was equal to the increase of total adenine nucleotides. At increasing degrees of respiratory inhibition the relative contributions of ADP and AMP to the total adenine nucleotide content increased. 6. The critical rate of respiration for the onset of inhibition of ion transport and the corresponding contents of adenine nucleotides provide estimates of the maximal values of certain parameters of energy metabolism required for the support of alkali-cation transport in the liver slices.
Spangler, W. J. (Oregon State University, Corvallis), and C. M. Gilmour. Biochemistry of nitrate respiration in Pseudomonas stutzeri. I. Aerobic and nitrate respiration routes of carbohydrate catabolism. J. Bacteriol. 91:245-250. 1966.-The metabolic pathways of glucose catabolism were studied in Pseudomonas stutzeri under aerobic conditions and under conditions of nitrate respiration. Studies on both glucose and gluconate catabolism, by the radiorespirometric method, indicated that these substrates are degraded in the same manner, i.e., the Entner-Doudoroff and pentose phosphate pathways. There appeared to be no major shift in primary metabolic pathways when nitrate was used as the terminal hydrogen acceptor in nitrate respiration as opposed to aerobic respiration with free molecular oxygen. It was shown that glucose is not degraded to any appreciable extent under anaerobic conditions in the absence of nitrate. Tentative evidence suggests that the tricarboxylic acid cycle functions under both conditions of oxygen relationships and that the rate of carbon oxidation via the tricarboxylic acid cycle is slower with nitrate respiration than under aerobic conditions.
This study assessed the effect of respirator speech device size on speech intelligibility and the impact of background noise on respirator communications effectiveness. Thirty-five subjects completed modified rhyme test (MRT) speech intelligibility testing procedures with and without a respirator under background noises of 40, 60, and 80 dBA. Respirator wear conditions included the use of one unmodified and three mechanical speech diaphragms modified to reduce the surface area of the vibrating inner membrane available for sound transmission. Average MRT scores decreased linearly as background noise levels increased for all conditions. Lower MRT scores were observed for all respirator speech diaphragm conditions compared to the nonrespirator condition within each noise category. Average MRT scores differed significantly between the unmodified speech diaphragm and one with a 70% reduced surface area with a 40-dBA background noise. However, MRT scores were similar between the modified and unmodified diaphragms at both the 60- and 80-dBA noise levels. These findings provide evidence that alternate designs of mechanical-type respirator speech devices can be achieved without further degradation of speech sound transmission.
The aim of this study was to investigate the mechanism of cellular regulation of mitochondrial respiration in permeabilized cardiac cells with clearly different structural organization: (i) in isolated rat cardiomyocytes with very regular mitochondrial arrangement, (ii) in HL-1 cells from mouse heart, and (iii) in non-beating (NB HL-1 cells) without sarcomeres with irregular and dynamic filamentous mitochondrial network. We found striking differences in the kinetics of respiration regulation by exogenous ADP between these cells: the apparent Km for exogenous ADP was by more than order of magnitude (14 times) lower in the permeabilized non-beating NB HL-1 cells without sarcomeres (25+/-4 microM) and seven times lower in normally cultured HL-1 cells (47+/-15 microM) than in permeabilized primary cardiomyocytes (360+/-51 microM). In the latter cells, treatment with trypsin resulted in dramatic changes in intracellular structure that were associated with 3-fold decrease in apparent Km for ADP in regulation of respiration. In contrast to permeabilized cardiomyocytes, in NB HL-1 cells creatine kinase activity was low and the endogenous ADP fluxes from MgATPases recorded spectrophotometrically by the coupled enzyme assay were not reduced after activation of mitochondrial oxidative phosphorylation by the addition of mitochondrial substrates, showing the absence of ADP channelling in the NB HL-1 cells. While in the permeabilized cardiomyocytes creatine strongly activated mitochondrial respiration even in the presence of powerful competing pyruvate kinase-phosphoenolpyruvate system, in the NB HL-1 cells the stimulatory effect of creatine was not significant. The results of this study show that in normal adult cardiomyocytes and HL-1 cells intracellular local restrictions of diffusion of adenine nucleotides and metabolic feedback regulation of respiration via phosphotransfer networks are different, most probably related to differences in structural organization of these cells.