Targeting pCO<Subscript>2</Subscript> in Asthma: Pilot Evaluation of a Capnometry-Assisted Breathing Training

Objectives This pilot study aimed to evaluate the feasibility and potential benefits of a novel biofeedback breathing training for achieving sustained increases in pCO₂ levels. Methods Twelve asthma patients were randomly assigned to an immediate 4-week treatment group or waiting list control. Patients were instructed to modify their respiration in order to change levels of end-tidal pCO₂ using a hand-held capnometer. Treatment outcome was assessed in frequency and distress of symptoms, asthma control, lung function, and variability of peak expiratory flow (PEF). Results We found stable increases in pCO₂ and reductions in respiration rate during treatment and 2-month follow-up. Mean pCO₂ levels rose from a hypocapnic to a normocapnic range at follow-up. Frequency and distress of symptoms was reduced and reported asthma control increased. In addition, mean PEF variability decreased significantly in the treatment group. Conclusions Our pilot intervention provided evidence for the feasibility of pCO₂-biofeedback training in asthma patients.     

Effect of elevated atmospheric CO2 concentration on soil and root respiration in winter wheat by using a respiration partitioning chamber

Soil respiration in a cropland is the sum of heterotrophic (mainly microorganisms) and autotrophic (root) respiration. The contribution of both these types to soil respiration needs to be understood to evaluate the effects of environmental change on soil carbon cycling and sequestration. In this paper, the effects of free-air CO₂ enrichment (FACE) on hetero- and autotrophic respiration in a wheat field were differentiated and evaluated by a novel split-root growth and gas collection system. Elevated atmospheric pCO₂ of approximately 200 μmol mol⁻¹ above the ambient pCO₂ significantly increased soil respiration by 15.1 and 14.8% at high nitrogen (HN) and low nitrogen (LN) application rates, respectively. The effect of elevated atmospheric pCO₂ on root respiration was not consistent across the wheat growth stages. Elevated pCO₂ significantly increased and decreased root respiration at the booting-heading stage (middle stage) and the late-filling stage (late stage), respectively, in HN and LN treatments; however, no significant effect was found at the jointing stage (early stage). Thus, the effect of increased pCO₂ on cumulative root respiration for the entire wheat growing season was not significant. Cumulative root respiration accounted for approximately 25–30% of cumulative soil respiration in the entire wheat growing season. Consequently, cumulative microbial respiration (soil respiration minus root respiration) increased by 22.5 and 21.1% due to elevated pCO₂ in HN and LN, respectively. High nitrogen application significantly increased root respiration at the late stage under both elevated pCO₂ and ambient pCO₂; however, no significant effects were found on cumulative soil respiration, root respiration, and microbial respiration. These findings suggest that heterotrophic respiration, which is influenced by increased substrate supplies from the plant to the soil, is the key process to determine C emission from agro-ecosystems with regard to future scenarios of enriched pCO₂.     

Heart Rate Variability Biofeedback Does Not Substitute for Asthma Steroid Controller Medication

Despite previous findings of therapeutic effects for heart rate variability biofeedback (HRVB) on asthma, it is not known whether HRVB can substitute either for controller or rescue medication, or whether it affects airway inflammation. Sixty-eight paid volunteer steroid naïve study participants with mild or moderate asthma were given 3 months of HRVB or a comparison condition consisting of EEG alpha biofeedback with relaxing music and relaxed paced breathing (EEG+), in a two-center trial. All participants received a month of intensive asthma education prior to randomization. Both treatment conditions produced similar significant improvements on the methacholine challenge test (MCT), asthma symptoms, and asthma quality of life (AQOL). MCT effects were of similar size to those of enhanced placebo procedures reported elsewhere, and were 65% of those of a course of a high-potency inhaled steroid budesonide given to a sub-group of participants following biofeedback training. Exhaled nitric oxide decreased significantly only in the HRVB group, 81% of the budesonide effect, but with no significant differences between groups. Participants reported becoming more relaxed during practice of both techniques. Administration of albuterol after biofeedback sessions produced a large improvement in pulmonary function test results, indicating that neither treatment normalized pulmonary function as a potent controller medication would have done. Impulse oscillometry showed increased upper airway (vocal cord) resistance during biofeedback periods in both groups. These data suggest that HRVB should not be considered an alternative to asthma controller medications (e.g., inhaled steroids), although both biofeedback conditions produced some beneficial effects, warranting further research, and suggesting potential complementary effects. Various hypotheses are presented to explain why HRVB effects on asthma appeared smaller in this study than in earlier studies. Clinical Trial Registration NCT02766374.     

Respiratory Sinus Arrhythmia Biofeedback Therapy for Asthma: A Report of 20 Unmedicated Pediatric Cases Using the Smetankin Method

This multiple case study describes pulmonary function changes in 20 asthmatic children from 30 consecutive cases undergoing biofeedback training for increasing the amplitude of respiratory sinus arrhythmia (RSA). The Smetankin protocol was used, which, in addition to RSA biofeedback, includes instructions in relaxed abdominal pursed-lips breathing. Ten individuals were excluded, including 6 who had been taking asthma medication, 2 who developed viral infections during the treatment period, and 2 who dropped out prior to completing treatment. Patients each received 13 to 15 sessions of training. Asthma tended to be mild, with mean spirometric values close to normal levels. Nevertheless, significant improvements were noted in 2 spirometry measures taken during forced expiratory maneuvers from maximum vital capacity: FEV₁ and FEF50. These preliminary uncontrolled data suggest that the Smetankin protocol warrants further evaluation as a nonpharmacological psychophysiological treatment for this condition, although these data could not definitively prove that the method is effective.     

Long-term effects of biofeedback-induced facial relaxation on measures of asthma severity in children

We studied the effects of electromyographic biofeedback on measures of asthma severity in children. Fifteen children received biofeedback training to reduce facial tension, and 14 children, who served as controls, received biofeedback training to maintain facial tension at a stable level. Assignment to experimental condition was random. As a result of training, electromyographic levels decreased in children trained in facial relaxation and remained fairly constant in children trained in facial tension stability. Biofeedback training was augmented for children in both groups by having them practice their facial exercises at home. Each child's condition was followed for a five-month period subsequent to biofeedback training. Throughout the experiment, the following measures of asthma severity were monitored: lung function, self-rated asthma severity, medication usage, and frequency of asthma attacks. In addition, standardized measures of attitudes toward asthma, self-concept, and chronic anxiety were recorded at regular intervals. As compared to the facial stability subjects, the facial relaxation subjects exhibited higher pulmonary scores, more positive attitudes toward asthma, and lower chronic anxiety during the follow-up period. Subjects in the two groups, however, did not differ on self-rated asthma severity, medication usage, frequency of asthma attacks, or self-concept. Based on the improvements we observed in pulmonary, attitude, and anxiety measures, we concluded that biofeedback training for facial relaxation contributes to the self-control of asthma and would be a valuable addition to asthma self-management programs.     

Characteristics of Resonance in Heart Rate Variability Stimulated by Biofeedback

As we previously reported, resonant frequency heart rate variability biofeedback increases baroreflex gain and peak expiratory flow in healthy individuals and has positive effects in treatment of asthma patients. Biofeedback readily produces large oscillations in heart rate, blood pressure, vascular tone, and pulse amplitude via paced breathing at the specific natural resonant frequency of the cardiovascular system for each individual. This paper describes how resonance properties of the cardiovascular system mediate the effects of heart rate variability biofeedback. There is evidence that resonant oscillations can train autonomic reflexes to provide therapeutic effect. The paper is based on studies described in previous papers. Here, we discuss the origin of the resonance phenomenon, describe our procedure for determining an individual's resonant frequency, and report data from 32 adult asthma patients and 24 healthy adult subjects, showing a negative relationship between resonant frequency and height, and a lower resonant frequency in men than women, but no relationship between resonant frequency and age, weight, or presence of asthma. Resonant frequency remains constant across 10 sessions of biofeedback training. It appears to be related to blood volume.     

Combined Heart Rate Variability and Pulse Oximetry Biofeedback for Chronic Obstructive Pulmonary Disease: Preliminary Findings

The purpose of this study was to examine the feasibility of an intervention that included heart rate variability (HRV) biofeedback and walking with pulse oximetry feedback to improve functioning and quality of life for patients with chronic obstructive pulmonary disease (COPD). Twenty patients with COPD participated in 5 weekly sessions of HRV biofeedback and 4 weekly sessions of walking practice with oximetry feedback, with instructions for daily home practice. Primary outcomes measures were the distance walked in 6 min (6MWD) and overall quality of life, as measured by the St. George's Respiratory Questionnaire (SGRQ). Secondary outcomes included measures of self-efficacy, self-reported disability, anxiety, depression, dyspnea before and after the 6MWD, and HRV at the frequency of respiration during spontaneous and paced breathing. After 10 weeks of training, participants showed statistically and clinically significant improvements in 6MWD and quality of life. Significant changes were also seen in self-efficacy, disability, dyspnea before and after the 6MWD, and HRV amplitude during spontaneous breathing. We conclude that our intervention is feasible for patients with COPD and that further research using a randomized controlled design is warranted.     

Long-term effects of biofeedback-induced facial relaxation on measures of asthma severity in children

We studied the effects of electromyographic biofeedback on measures of asthma severity in children. Fifteen children received biofeedback training to reduce facial tension, and 14 children, who served as controls, received biofeedback training to maintain facial tension at a stable level. Assignment to experimental condition was random. As a result of training, electromyographic levels decreased in children trained in facial relaxation and remained fairly constant in children trained in facial tension stability. Biofeedback training was augmented for children in both groups by having them practice their facial exercises at home. Each child's condition was followed for a five-month period subsequent to biofeedback training. Throughout the experiment, the following measures of asthma severity were monitored: lung function, self-rated asthma severity, medication usage, and frequency of asthma attacks. In addition, standardized measures of attitudes toward asthma, self-concept, and chronic anxiety were recorded at regular intervals. As compared to the facial stability subjects, the facial relaxation subjects exhibited higher pulmonary scores, more positive attitudes toward asthma, and lower chronic anxiety during the followup period. Subjects in the two groups, however, did not differ on self-rated asthma severity, medication usage, frequency of asthma attacks, or self-concept. Based on the improvements we observed in pulmonary, attitude, and anxiety measures, we concluded that biofeedback training for facial relaxation contributes to the self-control of asthma and would be a valuable addition to asthma self-management programs.This research was supported by NIH grant No. HL27402. We are grateful to Anita D. Baker, Lisa Barclay, Deborah L. Harm, and Douglas J. Miller for serving as experimenters and to Constance K. Cottrell and Cindy Stout for compiling summaries of the data.     

Atlantic cod actively avoid CO<Subscript>2</Subscript> and predator odour,even after long-term CO<Subscript>2</Subscript> exposure

Introduction

The rising atmospheric CO₂ level is continuously driving the dissolution of more CO₂ into the oceans, and some emission scenarios project that the surface waters may reach 1000 μatm by the end of the century. It is not known if fish can detect moderately elevated CO₂ levels, and if they avoid areas with high CO₂. If so, avoidance behaviour to water with high CO₂ could affect movement patterns and migrations of fish in the future. It is also being increasingly recognized that fish behaviour can be altered by exposure to CO₂. Therefore this study investigated how long-term exposure to elevated pCO₂ affects predator avoidance and CO₂ avoidance in juvenile Atlantic cod (Gadus morhua). The fish were exposed to control water or CO₂-enriched water (1000 μatm) for six weeks before being subjected to tests of behaviour.

Results

Despite long term exposure to elevated pCO₂ the cod still strongly avoided the smell of a predator. These data are surprising because several coral reef fish have demonstrated reversal of olfactory responses after CO₂ exposure, turning avoidance of predator cues into preference for predator cues. Fish from both treatment groups also demonstrated strong avoidance of CO₂ when presented with the choice of control or CO₂-acidified water, indicating that habituation to the CO₂ sensory stimuli is negligible.

Conclusions

As Atlantic cod maintained normal behavioural responses to olfactory cues, they may be tolerant to CO₂-induced behavioural changes. The results also suggest that despite the long-term exposure to CO₂-acidified water, the fish still preferred the control water over CO₂-acidified water. Therefore, in the future, fish may alter their movements and migrations in search of waters with a lower CO₂ content.

     

淫羊藿苷对RSV感染诱发哮喘小鼠体内PGD2水平的影响

摘要 目的：观察淫羊藿苷对RSV感染诱发哮喘小鼠血清及支气管肺泡灌洗液中前列腺素D2（Prostaglandin D2,PGD2）表达水平的影响,以期为哮喘治疗寻找新的靶点。方法：30只Balb/c小鼠随机均分为三组：即正常组,OVA/RSV-YYH组（即淫羊藿苷治疗组）及OVA/RSV-非YYH组（即未经淫羊藿苷治疗组）。卵蛋白致敏RSV感染诱发小鼠哮喘模型成功建立后,予以淫羊藿苷2.5 mg连续腹腔注射治疗2周,比较治疗前后肺功能检测结果、支气管肺泡灌洗液（bronchoalveolar lavage fluid,BALF）中细胞分类计数、血清及BALF中PGD2表达水平、肺组织病理学变化。结果：淫羊藿苷治疗后,哮喘小鼠肺功能较治疗前明显改善,差异有统计学意义（P<0.05）;PGD2水平较前明显下降,差异有统计学意义（P<0.05）;各分类白细胞计数较前明显减少,差异有统计学意义（P<0.01）,气道管壁增厚及管腔狭窄现象较前明显改善,肺组织炎症细胞浸润较前减少。结论：淫羊藿苷可有效降低RSV感染诱发哮喘小鼠体内炎性介质PGD2水平,从而改善气道重塑,减轻小鼠的哮喘症状,它可能是以后哮喘治疗的一个新的靶点。     

One‐year experiment on the physiological response of the Mediterranean crustose coralline alga,Lithophyllum cabiochae,to elevated pCO2 and temperature

The response of respiration, photosynthesis, and calcification to elevated pCO₂ and temperature was investigated in isolation and in combination in the Mediterranean crustose coralline alga Lithophyllum cabiochae. Algae were maintained in aquaria during 1 year at near‐ambient conditions of irradiance, at ambient or elevated temperature (+3°C), and at ambient (ca. 400 μatm) or elevated pCO₂ (ca. 700 μatm). Respiration, photosynthesis, and net calcification showed a strong seasonal pattern following the seasonal variations of temperature and irradiance, with higher rates in summer than in winter. Respiration was unaffected by pCO₂ but showed a general trend of increase at elevated temperature at all seasons, except in summer under elevated pCO₂. Conversely, photosynthesis was strongly affected by pCO₂ with a decline under elevated pCO₂ in summer, autumn, and winter. In particular, photosynthetic efficiency was reduced under elevated pCO₂. Net calcification showed different responses depending on the season. In summer, net calcification increased with rising temperature under ambient pCO₂ but decreased with rising temperature under elevated pCO₂. Surprisingly, the highest rates in summer were found under elevated pCO₂ and ambient temperature. In autumn, winter, and spring, net calcification exhibited a positive or no response at elevated temperature but was unaffected by pCO₂. The rate of calcification of L. cabiochae was thus maintained or even enhanced under increased pCO₂. However, there is likely a trade‐off with other physiological processes. For example, photosynthesis declines in response to increased pCO₂ under ambient irradiance. The present study reports only on the physiological response of healthy specimens to ocean warming and acidification, however, these environmental changes may affect the vulnerability of coralline algae to other stresses such as pathogens and necroses that can cause major dissolution, which would have critical consequence for the sustainability of coralligenous habitats and the budgets of carbon and calcium carbonate in coastal Mediterranean ecosystems.     

自适应式与固定式生物反馈训练对出口梗阻型便秘患者肛直肠功能和心理状态的影响

目的:探讨自适应式与固定式生物反馈训练对出口梗阻型便秘(OOC)患者肛直肠功能和心理状态的影响。方法:选取2017年4月～2019年12月期间晋城大医院收治的OOC患者98例,根据随机数字表法将患者分为对照组(n=49,固定式生物反馈训练)和研究组(n=49,自适应式生物反馈训练),比较两组患者疗效、肛直肠功能、排便次数、排便困难评分和心理状态。结果:研究组治疗8周后的临床总有效率93.88%(46/49),高于对照组的77.55%(38/49)(P0.05)。两组治疗8周后排便次数增加,排便困难评分降低(P0.05),研究组治疗8周后排便次数多于对照组,排便困难评分低于对照组(P0.05)。两组治疗8周后直肠肛门抑制反射阈、肛管静息压均较治疗前下降,模拟排便时直肠肛管压力梯度较治疗前升高(P0.05)。两组治疗8周后焦虑自评量表(SAS)、抑郁自评量表(SDS)评分均较治疗前下降,且研究组低于对照组(P0.05)。结论:与固定式生物反馈训练相比,自适应式生物反馈训练可获得与之效果相当的肛直肠功能改善程度,并可进一步减轻患者症状及改善心理状态,疗效显著。     

Vulnerability of macronutrients to the concurrent effects of enhanced temperature and atmospheric pCO<Subscript>2</Subscript> in representative shelf sea sediment habitats

Fundamental changes in seawater carbonate chemistry and sea surface temperatures associated with the ocean uptake of anthropogenic CO₂ are accelerating, but investigations of the susceptibility of biogeochemical processes to the simultaneous occurrence of multiple components of climate change are uncommon. Here, we quantify how concurrent changes in enhanced temperature and atmospheric pCO₂, coupled with an associated shift in macrofaunal community structure and behavior (sediment particle reworking and bioirrigation), modify net carbon and nutrient concentrations (NH₄-N, NO_x-N, PO₄-P) in representative shelf sea sediment habitats (mud, sandy-mud, muddy-sand and sand) of the Celtic Sea. We show that net concentrations of organic carbon, nitrogen and phosphate are, irrespective of sediment type, largely unaffected by a simultaneous increase in temperature and atmospheric pCO₂. However, our analyses also reveal that a reduction in macrofaunal species richness and total abundance occurs under future environmental conditions, varies across a gradient of cohesive to non-cohesive sediments, and negatively moderates biogeochemical processes, in particular nitrification. Our findings indicate that future environmental conditions are unlikely to have strong direct effects on biogeochemical processes but, particularly in muddy sands, the abundance, activity, composition and functional role of invertebrate communities are likely to be altered in ways that will be sufficient to regulate the function of the microbial community and the availability of nutrients in shelf sea waters.     

Freshwater biota and rising pCO2?

Rising atmospheric carbon dioxide (CO₂) has caused a suite of environmental issues, however, little is known about how the partial pressure of CO₂ (pCO₂) in freshwater will be affected by climate change. Freshwater pCO₂ varies across systems and is controlled by a diverse array of factors, making it difficult to make predictions about future levels of pCO₂. Recent evidence suggests that increasing levels of atmospheric CO₂ may directly increase freshwater pCO₂ levels in lakes, but rising atmospheric CO₂ may also indirectly impact freshwater pCO₂ levels in a variety of systems by affecting other contributing factors such as soil respiration, terrestrial productivity and climate regimes. Although future freshwater pCO₂ levels remain uncertain, studies have considered the potential impacts of changes to pCO₂ levels on freshwater biota. Studies to date have focused on impacts of elevated pCO₂ on plankton and macrophytes, and have shown that phytoplankton nutritional quality is reduced, plankton community structure is altered, photosynthesis rates increase and macrophyte distribution shifts with increasing pCO₂. However, a number of key knowledge gaps remain and gaining a better understanding of how freshwater pCO₂ levels are regulated and how these levels may impact biota, will be important for predicting future responses to climate change.     

Soil pCO2, soil respiration,and root activity in CO2-fumigated and nitrogen-fertilized ponderosa pine

The purpose of this paper is to describe the effects of CO₂ and N treatments on soil pCO₂, calculated CO₂ efflux, root biomass and soil carbon in open-top chambers planted with Pinus ponderosa seedlings. Based upon the literature, it was hypothesized that both elevated CO₂ and N would cause increased root biomass which would in turn cause increases in both total soil CO₂ efflux and microbial respiration. This hypothesis was only supported in part: both CO₂ and N treatments caused significant increases in root biomass, soil pCO₂, and calculated CO₂ efflux, but there were no differences in soil microbial respiration measured in the laboratory. Both correlative and quantitative comparisons of CO₂ efflux rates indicated that microbial respiration contributes little to total soil CO₂ efflux in the field. Measurements of soil pCO₂ and calculated CO₂ efflux provided inexpensive, non-invasive, and relatively sensitive indices of belowground response to CO₂ and N treatments.     

哮喘患儿呼出气一氧化氮、1,25-二羟维生素D3及儿童哮喘控制测试评分与肺功能的相关性

目的:探讨哮喘患儿呼出气一氧化氮(FeNO)、1,25-二羟维生素D_3[1,25(OH)_2D_3]及儿童哮喘控制测试(C-ACT)评分与肺功能的相关性。方法:选取2017年6月～2018年6月在我院就诊的86例哮喘患儿作为观察组,另选取同期于我院进行健康检查的86例健康儿童作为对照组。比较两组受试儿童1,25(OH)_2D_3浓度、FeNO、一秒用力呼气容积(FEV1)、呼气流量峰值(PEF)水平,比较不同病情哮喘患儿1,25(OH)_2D_3浓度、FeNO、C-ACT、FEV1、PEF水平,并分析哮喘患儿1,25(OH)_2D_3、FeNO、C-ACT与肺功能的相关性。结果:观察组1,25(OH)_2D_3浓度、FEV1、PEF水平低于对照组(P0.05),FeNO水平高于对照组(P0.05);随着病情加重,1,25(OH)_2D_3浓度、PEF、FEV1水平、C-ACT评分均逐渐下降,FeNO水平逐渐升高,不同病情患儿间比较差异均有统计学意义(P0.05)。哮喘患儿1,25(OH)_2D_3与FEV1、PEF呈正相关(r=0.912、0.873,P=0.006、0.008);C-ACT与FEV1、PEF呈正相关(r=0.472、0.366,P=0.036、0.032);FeNO与FEV1、PEF无相关(r=-0.035、-0.124,P=0.075、0.064)。结论:哮喘患儿1,25(OH)_2D_3浓度、C-ACT评分明显降低,FeNO水平明显升高,1,25(OH)_2D_3、C-ACT评分与肺功能呈正相关,但FeNO与肺功能无相关,C-ACT可用于哮喘患儿病情的预测,同时,通过提高患儿体内1,25(OH)_2D_3浓度可以改善其肺功能。     

Productivity gains do not compensate for reduced calcification under near‐future ocean acidification in the photosynthetic benthic foraminifer species Marginopora vertebralis

Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO₂) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont‐bearing foraminifer species Marginopora vertebralis on natural CO₂ seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced pCO₂. Net oxygen production increased up to 90% with increasing pCO₂; temperature, light, and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing pCO₂ and declined at higher temperatures. Respiration was also significantly elevated (~25%), whereas calcification was reduced (16–39%) at low pH/high pCO₂ compared to present‐day conditions. In the field, M. vertebralis was absent at three CO₂ seep sites at pH_Total levels below ~7.9 (pCO₂ ~700 μatm), but it was found in densities of over 1000 m^?2 at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration) or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under pCO₂ exceeding 700 μatm, thus are likely to be extinct in the next century.     

Long-term effects of elevated atmospheric CO<Subscript>2</Subscript> on species composition and productivity of a southern African C<Subscript>4</Subscript> dominated grassland in the vicinity of a CO<Subscript>2</Subscript> exhalation

We describe the long-term effects of a CO₂ exhalation, created more than 70 years ago, on a natural C₄ dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO₂ enrichment changes the competitive balance between plants with C₃ and C₄ photosynthetic pathways and how CO₂ enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO₂ on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO₂ alone. Species compositional data and soil δ¹³C isotopic evidence suggest no detectable effect of CO₂ enrichment on C₃:C₄ plant mixtures and individual species dominance. Contrary to many general predictions C₃ grasses did not become more abundant and C₃ shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO₂ concentrations averaging 610 μmol mol⁻¹. Leaf properties such as total N decreased in the C₃ but not C₄ grass under elevated CO₂ while total non-structural carbohydrate accumulation was not affected. Elevated CO₂ possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO₂ enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO₂ source. The conservative response of this grassland suggests that many of the reported effects of elevated CO₂ on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO₂ conditions.     

Effects of Breathing Training on Voluntary Hypo- and Hyperventilation in Patients with Panic Disorder and Episodic Anxiety

Anxiety disorders are associated with respiratory abnormalities. Breathing training (BT) aimed at reversing these abnormalities may also alter the anxiogenic effects of biological challenges. Forty-five Panic Disorder (PD) patients, 39 Episodic Anxiety patients, and 20 non-anxious controls underwent voluntary hypoventilation and hyperventilation tests twice while psychophysiological measures were recorded. Patients were randomized to one of two BT therapies (Lowering vs. Raising pCO₂) or to a waitlist. Before treatment panic patients had higher respiration rates and more tidal volume instability and sighing at rest than did non-anxious controls. After the Lowering therapy, patients had lower pCO₂ during testing. However, neither reactivity nor recovery to either test differed between patients and controls, or were affected by treatment. Although the two treatments had their intended opposite effects on baseline pCO₂, other physiological measures were not affected. We conclude that baseline respiratory abnormalities are somewhat specific to PD, but that previously reported greater reactivity and slower recovery to respiratory challenges may be absent.     

Fungal content of air samples from some asthmatic childrens’ homes in Mexico City

Fungal particles can be considered a potential risk factor in children causing asthma, rhinitis, and allergy. However, a direct relationship between mold exposure and respiratory symptoms is difficult to establish, particularly if volumetric results are not well documented, as is often the case in Mexico. In order to assess mold exposure in some asthmatic childrens’ homes, eight asthmatic children were selected. For each child, lung function was measured by spirometry and the flow expiratory volume drop in the first second (FEV₁) as well as the CVF were estimated at 5, 10 and 15 min, after a running period on a treadmill. Exercise induced asthma (EIA) was defined as a FEV₁ drop <10% or FEV₁/CVF drop >10%. Atopy was estimated by skin testing of allergen extracts. Each room was volumetrically sampled using Burkard Personal samplers, every week for a month and with different degrees of activity. Fungal composition was mostly dominated by allergenic molds, spores smaller than 10 μm and non-seasonal molds. Concentrations ranged from 0 to 2087 CFU/m³ and 102 553–29 522 200 spores/m³, being significantly higher in indoor air, but the differences between rooms or weeks were not significant, either for CFUs (P>0.27) or for total particles (P>0.80). In general, mold counts were dominated byPenicillium spp. andCladosporium spp. especiallyP. aurantiogriseum andC. cladosporioides. We observed that the median concentration values were in general higher for children with exercise induced asthma (EIA). But the differences were significant only for EIA and degree, of asthma particularly for total (P=0.038), mycotoxin producers (P<0.009), seasonal molds (P<0.006) andPenicillium spp. (P=0.012). Total spore counts showed the highest median values in children without EIA, moderate asthma degree and no atopy. Significant differences were found for almost all spore, type groupings when comparing the presence of EIA (P<0.05) or asthma degree categories (P<0.030), but no differences were observed for atopy (P>0.21). We conclude that respiratory symptoms as described by EIA, asthma severity and atopy may give a good correlation with fungal concentrations and especially comparisons based on their physical and chemical properties.