High Ventilation Rates Research Articles

Numerical and experimental study of the International Space Station crew quarters ventilation

The current paper proposes a detailed study of the ventilation system of the crew quarters (CQ) aboard the International Space Station (ISS) in order to identify the ventilation system's capacity to reduce CO2 accumulation around an occupant. These results would enable the improvement of the ventilation system, thereby decreasing the health risks of the occupants. The ventilation flow fields are studied through numerical results which are validated with experimental Particle Image Velocimetry (PIV) measurements in a reduced-scale mock-up. The equivalence between the reduced scale experimental and the full-scale numerical results is obtained through a Reynolds-number based similitude criteria. This enabled the authors to validate the isothermal airflow in the full-scale numerical model with the experimental results of the water flow in the reduced-scale mock-up. Normalized numerical and experimental velocity profiles have been superposed and were found to be in good agreement. Both numerical and experimental models highlight a stagnation region in the centre of the CQ volume leading to a ventilation deficit of the astronaut's breathing zone. The results indicate that this stagnant region is a reason for the excess CO2 accumulation in the CQ, despite the high ventilation rate (>45 hourly air exchanges). To the author's best knowledge this is the first numerical study of the CQ ventilation system validated with reduced-scale experimental modelling. The paper's findings have implications in building air quality studies, suggesting that targeted ventilation is preferable to raw increased in flow rates.

Investigation of Microclimate Ventilation of Simulated Garment in Terms of Wind Speed and Air Gap Thickness

During the circulation of air in the garment’s microclimate, the body extra heat dissipates to the environment. This event is an important factor in thermal comfort and ventilation. In this study, a heating cylinder was designed and calibrated to assess the ventilation occurrences in garment as a simulator of the human body. Tubular samples with different sizes were prepared using double jersey weft knitted fabric in order to obtain five levels of air gap thickness, including −1.5, 0, 1, 1.5 and 2 cm. Experiments were carried out in two conditions including without wind and by wind blowing with eight different wind speeds include 0.5, 1, 1.5, 2, 2.5, 3, 5 and 7 m/s. In each condition, the air gap’s temperature was considered as the main parameter for examination of the microclimate ventilation. The obtained outcomes revealed that by increasing the air gap thickness to more than 1 centimetre, the ventilation rate increased significantly. In the absence of wind, the change in the air gap’s temperature was not considerable for all sizes due to the natural convection phenomena that were slow. An increase of wind speed to more than 1 m/s led to a rise in the forced convection heat loss and took less time for the system to reach the equilibrium temperature; hence, higher ventilation rate was achieved. Moreover, by the increment of wind speed, the reduction of microclimate temperature follows a power function and at higher wind speeds remained approximately constant. According to the statistical analysis of results, it was confirmed that the ventilation rate of garment was influenced by wind speed; however, the influence of air gap thickness only in the absence of wind is significant.

Indoor humidity of dwellings and association with building characteristics, behaviors and health in a northern climate

Data from a nationwide survey on the status of the Swedish residential building stock and indoor air quality was placed in the public domain by the National Board of Housing, Building and Planning of Sweden. The current research investigates the indoor humidity conditions in Swedish residential buildings, single-family houses and apartments, assessing the measurements from the extensive BETSI-survey against adjusted relative humidity levels based on existing norms and Standards. The aim of this study is to investigate associations and correlations between relative humidity levels and multiple building and system characteristics, occupancy patterns and behaviors and health symptoms-complaints. The analysis uses 13 categorical and 9 continuous variables-parameters of the examined dwellings.Analysis shows that low indoor relative humidity is a realistic issue in Swedish dwellings during the heating season. The issue is more prevalent in apartments than single-family houses. In addition, low indoor relative humidity seems to be more extensive in dwellings with higher indoor temperature, smaller volume, higher ventilation rate and frequent airing practices, lower number of occupants, constructed mainly after 1985, in city suburbs and in the northern parts of the country. The developed multinomial logistic regression model may predict very accurately the relative humidity level of the Swedish dwellings, during heating season. This analysis offers additional evidence to the scientific literature for possible correlation of low relative humidity with specific health symptoms, complaints and disturbances.

Non-invasive respiratory support strategies in COVID-19

Non-invasive respiratory support strategies in COVID-19

Performance comparison of heat recovery systems to reduce viral contagion in indoor environments.

Strong ventilation increments are currently suggested for containing the airborne diffusion of COVID-19 in indoor environments. However, it can involve an unacceptable growing of energy consumption. Therefore, maximum care must be addressed to improve efficiency of ventilation heat recovery (VHR). For this purpose, this paper investigates the opportunity of a technical solution. Consisting in adding downstream of the most diffuse heat recuperator, a heat pump using exhaust air as a cold source. An autonomous high efficiency air handling unit (HEAHU) was modelled for a school application. By simulation a performance comparison was carried on with two alternative systems based only on an exhaust air heat pump (EAHP) or on a heat recuperator for different weather conditions. Results indicated that the milder climate strongly penalizes heat recuperator and this fact deeply influences the conclusions. HEAHU saving compared to energy consumption of only heat recuperator is between 31% and 46%. For EAHP this saving varies from 2.5% to 48%. Only with a milder climate, EAHP presents a lightly greater saving than HEAHU. Heat pump technology looks to be very performing to foster the efficiency of VHR, especially in presence of high ventilation rates.

Occupant-density-detection based energy efficient ventilation system: Prevention of infection transmission

Ventilation plays an important role in prevention and control of COVID-19 in enclosed indoor environment and specially in high-occupant-density indoor environments (e.g., underground space buildings, conference room, etc.). Thus, higher ventilation rates are recommended to minimize the infection transmission probability, but this may result in higher energy consumption and cost. This paper proposes a smart low-cost ventilation control strategy based on occupant-density-detection algorithm with consideration of both infection prevention and energy efficiency. The ventilation rate can be automatically adjusted between the demand-controlled mode and anti-infection mode with a self-developed low-cost hardware prototype. YOLO (You Only Look Once) algorithm was applied for occupancy detection based on video frames from surveillance cameras. Case studies show that, compared with a traditional ventilation mode (with 15% fixed fresh air ratio), the proposed ventilation control strategy can achieve 11.7% energy saving while lowering the infection probability to 2%. The developed ventilation control strategy provides a feasible and promising solution to prevent transmission of infection diseases (e.g., COVID-19) in public and private buildings, and also help to achieve a healthy yet sustainable indoor environment.

High energy efficiency ventilation to limit COVID-19 contagion in school environments

This study investigates the possibility to contain COVID-19 contagion in indoor environments via increasing ventilation rates obtained through high energy efficiency systems combining thermal recovery by heat exchanger and thermodynamic recovery by heat pump. The starting point of this assessment is a procedure to evaluate in naturally ventilated environments, the current infectious risk by using measurements of indoor/outdoor CO2 concentrations to calculate actual air changes per hour. The method was applied to some typical school environments in Italy. The results indicated very infectious situations with reproduction number Ro values up to exceed 13. But, the simulations assessed an extraordinary reduction of indoor viral concentration and consequently of the infection risk by a strong mechanical ventilation. High ventilation rates make facemasks effective even with use levels (from 50%) reasonable also for pupils. This way, R0 goes down the value one. As regards energy performance, the behavior of an autonomous high efficiency air handling unit (HEAHU), to be installed in an existing naturally ventilated classroom, was simulated in the monitored days. The results highlight the ability to achieve a reduction in energy consumption between 60% and 72%.

A Comparison Study of Coronavirus Disease 2019 Outcomes in Hospitalized Kidney Transplant Recipients.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect any human host, but kidney transplant recipients (KTR) are considered more susceptible on the basis of previous experience with other viral infections. We evaluated rates of hospital complications between SARS-CoV-2-positive KTR and comparator groups. We extracted data from the electronic health record on patients who were hospitalized with SARS-CoV-2, testing at six hospitals from March 4 through September 9, 2020. We compared outcomes between SARS-CoV-2-positive KTR and controls: SARS-CoV-2-positive non-KTR, SARS-CoV-2-negative KTR, and SARS-CoV-2-negative non-KTR. Of 31,540 inpatients, 3213 tested positive for SARS-CoV-2. There were 32 SARS-CoV-2-positive and 224 SARS-CoV-2-negative KTR. SARS-CoV-2-positive KTR had higher ferritin levels (1412; interquartile range, 748-1749 versus 553; interquartile range, 256-1035; P<0.01) compared with SARS-CoV-2-positive non-KTR. SARS-CoV-2-positive KTR had higher rates of ventilation (34% versus 14%, P<0.01; versus 9%, P<0.01; versus 5%, P<0.01), vasopressor use (41% versus 16%, P<0.01; versus 17%, P<0.01; versus 12%, P<0.01), and AKI (47% versus 15%, P<0.01; versus 23%, P<0.01; versus 10%, P<0.01) compared with SARS-CoV-2-positive non-KTR, SARS-CoV-2-negative KTR, and SARS-CoV-2-negative non-KTR, respectively. SARS-CoV-2-positive KTR continued to have increased odds of ventilation, vasopressor use, and AKI compared with SARS-CoV-2-positive non-KTR independent of Elixhauser score, Black race, and baseline eGFR. Mortality was not significantly different between SARS-CoV-2-positive KTR and non-KTR, but there was a notable trend toward higher mortality in SARS-CoV-2-positive KTR (25% versus 16%, P=0.15, respectively). Hospitalized SARS-CoV-2-positive KTR had a high rate of mortality and hospital complications, such as requiring ventilation, vasopressor use, and AKI. Additionally, they had higher odds of hospital complications compared with SARS-CoV-2-positive non-KTR after adjusting for Elixhauser score, Black race, and baseline eGFR. Future studies with larger sample size of KTR are needed to validate our findings. This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/K360/2021_03_25_KID0005652020.mp3.

Enhancing Air Quality for Embedded Hospital Germicidal Lamps

The indoor air of a hospital is always full of bacteria and viruses due to patients with different diseases. These bacteria and viruses could be highly infectious to the people in the hospital irrespective of their health conditions, and could be hazardous to the patients, their care takers, and hospital staff. Thus, keeping a good hospital air quality is very essential to the operation of the hospital. This study aims at enhancing ventilation of the interior lighting of hospitals with germicidal capabilities. Air disinfection is accomplished by adding the specially designed disinfecting filters and fans to existing embedded lamps in the hospitals. The embedded lamp has a square shape of 601 mm in width and 112 mm in thickness. In the design stage, the air flow inside the embedded lamp with the added filters and fans was investigated by numerical simulation using a computational fluid dynamics (CFD) tool. Three designs, referred to as Types 1, 2, and 3, were evaluated using steady-state CFD flow simulations. The ventilation rate of the Type 1 design was about 251.9 CMH, and 348.3 CMH for the Type 2 design by increasing the fan outlet area. However, even though the ventilation was increased by 34%, the flow field of the Type 2 design was not uniform, resulting in flows being circulated around the side locations. Thus, the Type 3 design further treats this aspect by streamlining the outlet geometry and adding flow guiding vanes to reduce flow resistance and flow unsteadiness; the corresponding air ventilation rate reached 376.3 CMH. Hence, the Type 3 design was fabricated and tested. The test results confirm that the design not only has a higher ventilation rate but also operates under a smaller pressure drop, thus accomplishing the goal of providing good air quality in the hospital environment efficiently. Moreover, the associated flow noise is reduced by about 8 dBA. Hence, both an increase in the air ventilation rate and a reduction of noise are achieved simultaneously by the present method.

Mechanistic transmission modeling of COVID-19 on the Diamond Princess cruise ship demonstrates the importance of aerosol transmission

Several lines of existing evidence support the possibility of airborne transmission of coronavirus disease 2019 (COVID-19). However, quantitative information on the relative importance of transmission pathways of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains limited. To evaluate the relative importance of multiple transmission routes for SARS-CoV-2, we developed a modeling framework and leveraged detailed information available from the Diamond Princess cruise ship outbreak that occurred in early 2020. We modeled 21,600 scenarios to generate a matrix of solutions across a full range of assumptions for eight unknown or uncertain epidemic and mechanistic transmission factors. A total of 132 model iterations met acceptability criteria (R2 > 0.95 for modeled vs. reported cumulative daily cases and R2 > 0 for daily cases). Analyzing only these successful model iterations quantifies the likely contributions of each defined mode of transmission. Mean estimates of the contributions of short-range, long-range, and fomite transmission modes to infected cases across the entire simulation period were 35%, 35%, and 30%, respectively. Mean estimates of the contributions of larger respiratory droplets and smaller respiratory aerosols were 41% and 59%, respectively. Our results demonstrate that aerosol inhalation was likely the dominant contributor to COVID-19 transmission among the passengers, even considering a conservative assumption of high ventilation rates and no air recirculation conditions for the cruise ship. Moreover, close-range and long-range transmission likely contributed similarly to disease progression aboard the ship, with fomite transmission playing a smaller role. The passenger quarantine also affected the importance of each mode, demonstrating the impacts of the interventions.

Design of solar-powered forced ventilation system and energy-efficient thermal comfort operation of greenhouse

This study focuses on design of energy-efficient forced ventilation scheme by exploitation of renewable energy in agricultural greenhouse facilities, which are available to and applicable in the farming industry. For a high productive greenhouse, thermal comfort operation is essential, which is ensured by an effective and efficient ventilating fan and pad system. The spatial temperature variations inside greenhouse are regulated through high ventilation rate. But it is contrasted by the energy consumption costs. The provision of ambient uniform indoor environmental quality for plants whilst achieving energy and cost efficient operation in agriculture buildings represents a multi variant problem. The experimental study is conducted in the greenhouse facility available at Centre of Excellence for Vegetables, Tamil Nadu, India and the iterative dynamic programming scheme is proposed to determine the optimal sequence of ventilation set points by considering the meteorological conditions which affect the environment inside the greenhouse. For instance, this multi speed ventilation approach trade-off between the low and high ventilation rates in order to compensate the thermal stratification and energy consumed by the forced ventilation system. Considering the endurance level of plant physiology, the set point blueprint is determined under the compatible control region which is helpful to trail less energy cost and to realize lower level climate control objectives of the overall environmental control greenhouse. Moreover, the energy required is realized by a photovoltaic system design to guarantee the essential and continuous self-sustained operation of the greenhouse. The performance of the system is monitored over a period of time and the system is able to provide favourable growth conditions under sustainable ecological environment principles for greenhouse agro-ecosystem. In addition to minimisation of temperature variation, it provides thermal stability and comfort by mitigating heat stress ascertained during cycling of existing single speed fan operation with 30.83% energy savings.

Numerical Study on Indoor Environmental Quality in a Room Equipped with a Combined HRV and Radiator System

Heat recovery ventilation (HRV) systems can be integrated with an additional air heater in buildings with low energy demand in order to cover space heating demand. The employment of coupled HRV-heater systems is, therefore, gaining increasing interest for the improvement of the indoor environmental quality (IEQ), as well as the reduction of ventilation energy loss. The present paper analyses the efficacy of a HRV system, coupled with a low-temperature radiator, in satisfying the IEQ indices inside a retrofitted dormitory room. A computational fluid dynamic (CFD) model based on the finite volume method is established to investigate IEQ characteristics including indoor air quality and thermal comfort condition. The presented CFD code provides a practical tool for a comprehensive investigation of the IEQ indices in spaces employing a coupled HVAC system. In an analysis of indoor air quality, parameters such as age of the air, air change efficiency, and ventilation efficiency in removal of gaseous contaminants, namely VOCs and CO2, are evaluated. The results obtained by the numerical model allow addressing the interaction between HRV and radiator systems and its effects on airflow field. The results show the decrease of the indoor operative temperature with increment of the supply air flow rate, which is mainly due to the decreased thermal efficiency of the HRV system. The obtained results indicate that, while higher ventilation rates can significantly decrease the age of the air and gaseous contaminants level, at the same time, it would cause a local discomfort in some parts of the room.

Air Changes for Healthy Indoor Ambiences under Pandemic Conditions and Its Energetic Implications: A Galician Case Study

The present paper aims to show a mathematical understanding of the effect of ventilation rate over building energy consumption. Moreover, as a case study to show this methodology, a proposal was analyzed of modifying the teaching period to reach a maximum increase of air changes in school buildings, to allow adherence to the COVID-19 pandemic requirements in the Galicia region, with lower energy consumption. In this sense, to analyze the energetic implication of this proposal, the building construction was defined, modeled in accordance with the ISO Standard 13790 and implemented in accordance with the Monte Carlo method. Results showed the probability of energy consumption as a Weibull model. Furthermore, a map of different Weibull models in accordance with different ventilation rates was developed. The constants of the Weibull models allow to identify normal distributions of the probability density functions of energy consumption, especially the ones with lower energy consumption. As a consequence, these constants are a better parameter to identify the optimal ventilation rate for each season in search of a healthy indoor ambience, which is of interest for a future design guide. Finally, the main results showed a reduction of energy consumption at a higher ventilation rate in the summer season. As a consequence, the necessity of modifying teachings periods, as an adequate procedure to prevent more COVID infections, is concluded.

Polyvinylidene fluoride composite nanofibrous filter for high-efficiency PM2.5 capture

Filter materials are widely used in the capture of fine particulate matter (PM), however, there are some problems such as low filtration efficiency, difficult cleaning and low air flow still need to be solved eagerly. In this work, a high-performance PM2.5 capture as well as high productivity (1000 m2/day) was fabricated by introducing an ultra-thin polyvinylidene fluoride (PVDF) nanofibrous layer on the filter materials via electrospinning technology with rotary bead-wire spinnerets. The electrospun PVDF nanofibers exhibit a strong ability to intercept and attract PM, thus, the filtering efficiency of the filter material for PM2.5 improved significantly (69.958%–98.161%). The composite filter has a higher air flow (278.4 mm/s) and lower pressure drop (30 Pa). Furthermore, long-term filtration and ventilation rate experiments show that the composite filter has stable high filtration efficiency (98.137%–96.36%) and ventilation rate. Electrospun PVDF fibers also have a certain degree of hydrophobicity, which could increase the long lifetime of composite filter effectively. This high-performance composite nanofibrous membrane would be a promising filter for large-scale PM2.5 capture production and personal health protection.

Severe Group A and Group B Streptococcus Diseases at a Pediatric ICU: Are they Still Sensitive to the Penicillins?

: Background: Group A β-hemolytic Streptococcus (GAS) and Group B streptococcus (GBS) are two common pathogens that are associated with many diseases in children. Severe infections as a result of these two streptococci are albeit uncommon but associated with high mortality and morbidity, and often necessitate intensive care support. This paper aims to review the mortality and morbidity of severe infection associated with GAS and GBS isolations at a Pediatric Intensive Care Unit (PICU).Methods: All children admitted to PICU of a teaching hospital between October 2002 and May 2018 with laboratory-proven GAS and GBS isolations were included.Results: There were 19 patients (0.7% PICU admissions) with streptococcal isolations (GAS, n=11 and GBS, n=8). Comparing to GAS, GBS affected infants were younger (median age 0.13 versus 5.47 years, 95% CI, 1.7-8.5, p=0.0003), and cerebrospinal fluids more likely positive (p = 0.0181). All GAS and GBS were sensitive to penicillin (CLSI: MICs 0.06 – 2.0 μg/mL), with the majority of GAS sensitive to clindamycin and erythromycin, and half of the GBS resistant to clindamycin and erythromycin. Co-infections were prevalent, but viruses were only isolated with GAS (p=0.024). Isolation of GAS and GBS was associated with nearly 40% mortality and high rates of mechanical ventilation and inotropic supports. All non-survivors had high mortality (PIM2) and sepsis scores.Conclusions: Severe GAS and GBS are rare but associated with high mortality and rates of mechanical ventilation and inotropic supports in PICU. The streptococci are invariably sensitive to penicillin. The high PIM2 and Sepsis scores suggest that prompt recognition of sepsis and the timely judicious institution of antibiotics and intensive care support may be life-saving for these devastating infections.

Definition of Optimal Ventilation Rates for Balancing Comfort and Energy Use in Indoor Spaces Using CO2 Concentration Data

Air ventilation rate plays a relevant role in maintaining adequate indoor air quality (IAQ) conditions in public buildings. In general, high ventilation rates ensure good indoor air quality but entail relevant energy consumption. Considering the necessity of balancing IAQ and energy consumption, a correlation between the number of occupants obtained from analysis of CO2 concentration variation is presented as a general element for controlling the operation of heating ventilation and air cooling (HVAC) systems. The specific CO2 exhalation rate is estimated using experimental data in some real conditions in university classrooms. A method for the definition of optimal values of air exchange rate is defined, highlighting that the obtained values are much lower than those defined in current technical standards with possibilities of relevant reduction of the total energy consumption.

Long-term, continuous air quality monitoring in a cross-sectional study of three UK non-domestic buildings

Long-term, continuous air quality monitoring has been carried out alongside seasonal passive sampling within a case study a hospital, school and office building, representing a cross-section of the UK non-domestic sector. This approach aimed at adopting state of the art sensor technology to provide a greater understanding of the variations in indoor air quality over time and how these variations relate to both building operation and occupant behavior. The results highlight how the relationship between indoor and outdoor air evolves considerably on both short and long-term basis, with varying behaviors then seen across different sources of pollutants. The mechanically ventilated hospital and school buildings demonstrate the effectiveness of particulate filters, with very low internal concentrations of PM2.5. However, high ventilation rates, combined with the absence of any filtration of NO2, resulted in the hospital having the highest indoor concentrations of NO2 and the highest associated indoor-outdoor ratio. Morning and evening traffic related peaks in NO2 can be observed indoors, with their penetration dependent upon the delivered ventilation rates. This demonstrates the impact of adopting high ventilation rates during peak traffic, and the consequences of CO2 based demand-controlled ventilation systems in polluted urban areas without full filtration. The naturally ventilated office then demonstrates significant seasonal variations, with increased ventilation openings resulting in indoor NO2 concentrations in the summer exceeding those in the winter, despite significant reductions in ambient levels. Conversely, concentrations of indoor pollutants are seen to reduce with increasing ventilation rates, demonstrating the complex balance between the dilution of indoor pollutants and penetration of outdoor sources. Despite significant reductions from the winter to the summer (21.6–11.2 μg/m3), all formaldehyde measurements in the naturally ventilated office exceeded guideline values, indicating improved guidance and product labelling schemes may be required to achieve these guideline concentrations and reduce associated health risks.

Delivery of Positive End-Expiratory Pressure Using Self-Inflating Bags during Newborn Resuscitation Is Possible Despite Mask Leak

Background: Ventilation is the key intervention to resuscitate non-breathing newborns. Positive end-expiratory pressure (PEEP) may facilitate lung-liquid clearance and help establish functional residual capacity. Objectives: The aim of this study was to describe how mask leak and ventilation rates affect delivered PEEP and tidal volumes during newborn resuscitations using a self-inflating bag with an integrated PEEP valve. Methods: This was an observational study including near-term/term newborns who received bag-mask ventilation (BMV) with a new self-inflating bag with a novel 6 mbar PEEP valve, without external gas flow, between October 1, 2016 and June 30, 2018 in rural Tanzania. Helping Babies Breathe-trained midwives performed most of the resuscitations. Pressures and flow were continuously measured and recorded by resuscitation monitors. Results: In total, 198 newborns with a median gestation of 39 weeks (25th, 75th percentiles 37, 40) and birth weight of 3,100 g (2,580, 3,500) were included. The median delivered PEEP and expired (tidal) volume at different levels of mask leak were 6.0 mbar and 11.3 mL/kg at 0–20% mask leak, 5.5 mbar and 9.3 mL/kg at 20–40%, 5.2 mbar and 7.8 mL/kg at 40–60%, 4.6 mbar and 5.0 mL/kg at 60–80%, and 1.0 mbar and 0.6 mL/kg at 80–100% mask leak. A high ventilation rate (>60/min) nearly halved expired volumes compared to <60/min for 0–60% leak. The BMV rate had a negligible effect on peak inflation pressure (PIP) and PEEP. Conclusions: Mask leak up to 80% did not impair the provision of recommended PEEP or tidal volumes during BMV with a self-inflating bag. High or low ventilation rates did not significantly affect PIP or PEEP. Expired volumes were reduced at ventilation rates >60/min.

Cut-off values to evaluate exercise-induced asthma in eucapnic voluntary hyperventilation test for children.

Background and AimThe eucapnic voluntary hyperventilation (EVH) testing is a diagnostic tool for diagnostics of exercise‐induced bronchoconstriction; while the testing has become more common among children, data on the test's feasibility among children remain limited. Our aim was to investigate EVH testing feasibility among children, diagnostic testing cut‐off values, and which factors affect testing outcomes.MethodsWe recruited 134 patients aged 10–16 years with a history of exercise‐induced dyspnoea and 100 healthy control children to undergo 6‐min EVH testing. Testing feasibility was assessed by the children's ability to achieve ≥70% of the target minute ventilation of 30 times forced expiratory volume in 1 s (FEV1). Bronchoconstriction was assessed as a minimum of 8%, 10%, 12%, 15% or 20% fall in FEV1. Patient characteristics were correlated with EVH outcomes.ResultsOverall, 98% of the children reached ≥70%, 88% reached ≥80%, 79% reached ≥90% and 62% reached ≥100% of target ventilation in EVH testing; of children with a history of exercise‐induced dyspnoea, the decline percentages were as follows: 24% (≥8% fall), 17% (≥10% fall), 10% (≥12% fall), 6% (≥15% fall) and 5% (≥20% fall) in FEV1, compared to 11%, 4%, 3%, 1% and 0% among the healthy controls, respectively. Healthy controls and boys performed testing at higher ventilation rates (p < .05).ConclusionEucapnic voluntary hyperventilation testing is feasible among children aged 10–16 years and has diagnostic value in evaluating exercise‐induced dyspnoea among children. A minimum 10% fall in FEV1 is a good diagnostic cut‐off value. Disease status appears to be important covariates.

Energy, Production and Environmental Characteristics of a Conventional Weaned Piglet Farm in North West Spain

Postweaning is one of the most sensitive and energy-demanding phases of swine production. The objective of this research was to assess the energy, production and environmental characteristics of a conventional farm with temperature-based environmental control. The selected energy, environmental and production variables were measured on farm, in a high livestock density area of NW Spain, for seven production cycles. The quantification of variables was aimed at obtaining the maximum performance with the lowest possible use of resources, focusing on animal welfare and production efficiency. The Brown–Forsythe, Welch and Games-Howell tests revealed significant differences in terms of temperature, relative humidity and CO2 concentrations among production cycles, and among the critical, postcritical and final periods. Improved humidity management resulted in a 17% reduction of climate control energy, which involved energy savings in the range of 33% to 47% per kg produced at the end of the postweaning cycle. Accordingly, adding humidity as a control variable could result in higher ventilation rates, thereby improving animal welfare, reducing heating energy use and increasing weight gain per unit climate control energy. In addition, the strong correlations found between heating energy and relative humidity (R2 = 0.73) and ventilation energy and CO2 (R2 = 0.99) suggest that these variables could be readily estimated without additional sensor costs.