Standard Ventilation Research Articles

Achieving standard natural ventilation rate of dwellings in a hot-arid climate using solar chimney

Increasingly, passive ventilation solutions are receiving considerable attention for inducing natural ventilation in dwellings regarding operation costs, energy demands, and carbon dioxide emissions. Solar chimney, in particular, is a promising alternative to enhance thermal and ventilation performance for the indoor environment by using convection of air heated by passive solar energy. The present study focuses on achieving optimum natural ventilation rate by incorporating solar chimney into a single room in a hot climatic context. Specifically, a mathematical model is developed through an overall energy balance on the solar chimney. This model examines a wide range of geometry parameters under real weather data to determine the optimum design solutions for the solar chimney. Furthermore, the model predicts the temperatures of the glazing and the black painted absorber as well as air velocity exiting from the chimney. The analytical results showed that an optimum air flow rate of 0.019–0.033m3/s was achieved by 88.2% during the daytime when the dimensions of a proposed solar chimney are 45° inclination angle, 1.4m length, 0.6m width and 0.20m air gab. Moreover, Computational Fluid Dynamics (CFD) was applied to predict space flow pattern using CFD module in DesignBuilder software, which is based on Energy-Plus dynamic simulation engine. The renormalization group (RNG) k-ε turbulence model was applied to solving the mass and energy equations within the solar chimney. Comparisons of the model predictions with CFD calculations and bibliographic experimental work outline the validity of the model.

Airway pressure release ventilation during ex vivo lung perfusion attenuates injury

ObjectiveCritical organ shortages have resulted in ex vivo lung perfusion gaining clinical acceptance for lung evaluation and rehabilitation to expand the use of donation after circulatory death organs for lung transplantation. We hypothesized that an innovative use of airway pressure release ventilation during ex vivo lung perfusion improves lung function after transplantation. MethodsTwo groups (n = 4 animals/group) of porcine donation after circulatory death donor lungs were procured after hypoxic cardiac arrest and a 2-hour period of warm ischemia, followed by a 4-hour period of ex vivo lung perfusion rehabilitation with standard conventional volume-based ventilation or pressure-based airway pressure release ventilation. Left lungs were subsequently transplanted into recipient animals and reperfused for 4 hours. Blood gases for partial pressure of oxygen/inspired oxygen fraction ratios, airway pressures for calculation of compliance, and percent wet weight gain during ex vivo lung perfusion and reperfusion were measured. ResultsAirway pressure release ventilation during ex vivo lung perfusion significantly improved left lung oxygenation at 2 hours (561.5 ± 83.9 mm Hg vs 341.1 ± 136.1 mm Hg) and 4 hours (569.1 ± 18.3 mm Hg vs 463.5 ± 78.4 mm Hg). Likewise, compliance was significantly higher at 2 hours (26.0 ± 5.2 mL/cm H2O vs 15.0 ± 4.6 mL/cm H2O) and 4 hours (30.6 ± 1.3 mL/cm H2O vs 17.7 ± 5.9 mL/cm H2O) after transplantation. Finally, airway pressure release ventilation significantly reduced lung edema development on ex vivo lung perfusion on the basis of percentage of weight gain (36.9% ± 14.6% vs 73.9% ± 4.9%). There was no difference in additional edema accumulation 4 hours after reperfusion. ConclusionsPressure-directed airway pressure release ventilation strategy during ex vivo lung perfusion improves the rehabilitation of severely injured donation after circulatory death lungs. After transplant, these lungs demonstrate superior lung-specific oxygenation and dynamic compliance compared with lungs ventilated with standard conventional ventilation. This strategy, if implemented into clinical ex vivo lung perfusion protocols, could advance the field of donation after circulatory death lung rehabilitation to expand the lung donor pool.

Abstract PR532

Background & Objectives: Preoxygenation is used to maximise alveolar oxygen reserves prior to induction of anaesthesia thus allowing a longer safe apnoea time prior to securing the airway. A barrier to routine preoxygenation is the delay that such practice might incur in the time to induction of anaesthesia1. Optimal preoxygenation is defined as FeO2≥0.9. However, this may predispose to alveolar absorption atelectasis and may be unachievable within an acceptable timeframe. Therefore, a FeO2≥0.8 is a compromise target. The purpose of this study was to determine whether Non-Invasive Ventilation (NIV) would achieve a targeted Fractional Expired Oxygen (FeO2) concentration faster than standard ventilation (SV) during preoxygenation prior to induction of anaesthesia. Materials & Methods: This was a cross-over study of 20 adult patients (age range 18-80) undergoing elective surgery. The patients were recruited via the Pre-Operative Assessment Clinic to undergo a controlled comparison of two preoxygenation techniques. SV consisted of 10L/min of 100% oxygen via tight fitting facemask. NIV consisted of 10L/min of 100% oxygen via tight fitting facemask, with 5cmH20 pressure support and 5cmH20 positive end expiratory pressure. Each patient was preoxygenated using both techniques. The sequence of preoxygenation was randomised, with sufficient time interval between techniques to allow alveolar gas composition to return to baseline. Patients were placed in the supine position and initial FeO2 after the first breath was recorded. The time the patient reached a FeO2 0.8 was recorded. An additional 2 minutes were allowed for the patient to reach 0.9. If this was not achieved the maximal FeO2 was recorded. At the end of the study patients were asked for their preferred technique. Results: Of the 20 patients recruited 14 were male and 6 female. The average age was 60 years. The mean time to achieve FeO20.8 using NIV (57 seconds: range 30 - 105 sec) was faster than SV (148 seconds: range 50 - 440 sec). The mean difference was 92 seconds faster for NIV (95% confidence interval: range 43.3 -142.6; P=0.0009). In addition, when subjected to NIV, 15/20 patients (75%) achieved FeO2 0.9 in a further 2 minutes, compared to only 6/20 patients (30%) in the standard preoxygenation group. 78% of patients preferred NIV to standard technique (P=0.0184).Conclusion: This study demonstrates that NIV is a technique that achieves a FeO2 0.8 faster and is better tolerated than standard preoxygenation.

Associations Between Ventilator Bundle Components and Outcomes

Ventilator bundles, including head-of-bed elevation, sedative infusion interruptions, spontaneous breathing trials, thromboprophylaxis, stress ulcer prophylaxis, and oral care with chlorhexidine gluconate, are ubiquitous, but the absolute and relative value of each bundle component is unclear. To evaluate associations between individual and collective ventilator bundle components and ventilator-associated events, time to extubation, ventilator mortality, time to hospital discharge, and hospital death. This retrospective cohort study included all 5539 consecutive patients who underwent mechanical ventilation for at least 3 days from January 1, 2009, to December 31, 2013, at Brigham and Women's Hospital. Head-of-bed elevation, sedative infusion interruptions, spontaneous breathing trials, thromboprophylaxis, stress ulcer prophylaxis, and oral care with chlorhexidine. Hazard ratios (HRs) for ventilator-associated events, extubation alive vs ventilator mortality, and hospital discharge vs hospital death. Effects were modeled using Cox proportional hazards regression and Fine-Gray competing risk models adjusted for patients' demographic characteristics, comorbidities, unit type, severity of illness, recent procedures, process measure contraindications, day-to-day markers of clinical status, and calendar year. Of 5539 consecutive patients undergoing mechanical ventilation, 3208 were male (57.9%), 2331 female (42.1%), and the mean (SD) age was 61.2 (16.1) years. Sedative infusion interruptions were associated with less time to extubation (HR, 1.81; 95% CI, 1.54-2.12; P < .001) and a lower hazard for ventilator mortality (HR, 0.51, 95% CI, 0.38-0.68; P < .001). Similar associations were found for spontaneous breathing trials (HR for extubation, 2.48; 95% CI 2.23-2.76; P < .001; HR for mortality, 0.28; 95% CI, 0.20-0.38; P = .001). Spontaneous breathing trials were also associated with lower hazards for ventilator-associated events (HR, 0.55; 95% CI, 0.40-0.76; P < .001). Associations with less time to extubation were found for head-of-bed elevation (HR, 1.38, 95% CI, 1.14-1.68; P = .001) and thromboembolism prophylaxis (HR, 2.57; 95% CI, 1.80-3.66; P < .001) but not ventilator mortality. Oral care with chlorhexidine was associated with an increased risk for ventilator mortality (HR, 1.63; 95% CI, 1.15-2.31; P = .006), and stress ulcer prophylaxis was associated with an increased risk for ventilator-associated pneumonia (HR, 7.69; 95% CI, 1.44-41.10; P = .02). Standard ventilator bundle components vary in their associations with patient-centered outcomes. Head-of-bed elevation, sedative infusion interruptions, spontaneous breathing trials, and thromboembolism prophylaxis appear beneficial, whereas daily oral care with chlorhexidine and stress ulcer prophylaxis may be harmful in some patients.

Neurally adjusted ventilatory assist (NAVA) in preterm newborn infants with respiratory distress syndrome-a randomized controlled trial.

Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator synchrony during invasive ventilation and leads to lower peak inspiratory pressures (PIP) and oxygen requirements. The aim of this trial was to compare NAVA with current standard ventilation in preterm infants in terms of the duration of invasive ventilation. Sixty infants born between 28+0 and 36+6weeks of gestation and requiring invasive ventilation due to neonatal respiratory distress syndrome (RDS) were randomized to conventional ventilation or NAVA. The median durations of invasive ventilation were 34.7h (quartiles 22.8-67.9h) and 25.8h (15.6-52.1h) in the NAVA and control groups, respectively (P=0.21). Lower PIPs were achieved with NAVA (P=0.02), and the rapid reduction in PIP after changing the ventilation mode to NAVA made following the predetermined extubation criteria challenging. The other ventilatory and vital parameters did not differ between the groups. Frequent apneas and persistent pulmonary hypertension were conditions that limited the use of NAVA in 17% of the patients randomized to the NAVA group. Similar cumulative doses of opiates were used in both groups (P=0.71). NAVA was a safe and feasible ventilation mode for the majority of preterm infants suffering from RDS, but the traditional extubation criteria were not clinically applicable during NAVA. • NAVA improves patient-ventilator synchrony during invasive ventilation. • Lower airway pressures and oxygen requirements are achieved with NAVA during invasive ventilation in preterm infants by comparison with conventional ventilation. What is new: • Infants suffering from PPHN did not tolerate NAVA in the acute phase of their illness. • The traditional extubation criteria relying on inspiratory pressures and spontaneous breathing efforts were not clinically applicable during NAVA.

Design of Compressor less Solar Powered Refrigerator

The thermoelectric effect has been proven as a source of cooling and small power generation as defined by the Peltier-Seebeck effect. Thermoelectric modules, optimized by semiconductors, have been used for temperature regulation by operating as a heat pump to maintain computing devices and integrated circuits at optimum temperatures for improved processing efficiency. Thermoelectric modules have also been used to capture microwatt electrical power from personal computing and other small scale devices by way of utilizing the waste heat rejected through its heat sink. In modern data centers and server farms, water cooling of electronics has been widely adapted as a more efficient cooling method than standard air conditioning and ventilation systems due to its vastly larger thermal capacity. However, even high density electronics cabinets and processing units are low level heat applications unfit for waste heat recovery by standard thermodynamics cycles and heat pumps. When applying the thermoelectric effect to the temperature difference between the heat source of the processing electronics and the heat sink of a water cooling system, potential exists for practical and economic energy recovery. This study demonstrates the feasibility of waste energy recovery from high power density electronics in data centers and server farms by way of the practical and economic application of thermoelectricity. An overview of thermoelectricity and the thermoelectric effect is given, including a review of semiconductor materials and electronics cabinet cooling techniques. This report describes an investigation into the efficiency of applying thermoelectricity to low temperature waste heat situations. Conclusions are presented concerning the effectiveness of this application towards waste heat utilization for power recovery.

The Ratio of Partial Pressure Arterial Oxygen and Fraction of Inspired Oxygen 1 Day After Acute Respiratory Distress Syndrome Onset Can Predict the Outcomes of Involving Patients.

The initial hypoxemic level of acute respiratory distress syndrome (ARDS) defined according to Berlin definition might not be the optimal predictor for prognosis. We aimed to determine the predictive validity of the stabilized ratio of partial pressure arterial oxygen and fraction of inspired oxygen (PaO2/FiO2 ratio) following standard ventilator setting in the prognosis of patients with ARDS.This prospective observational study was conducted in a single tertiary medical center in Taiwan and compared the stabilized PaO2/FiO2 ratio (Day 1) following standard ventilator settings and the PaO2/FiO2 ratio on the day patients met ARDS Berlin criteria (Day 0). Patients admitted to intensive care units and in accordance with the Berlin criteria for ARDS were collected between December 1, 2012 and May 31, 2015. Main outcome was 28-day mortality. Arterial blood gas and ventilator setting on Days 0 and 1 were obtained.A total of 238 patients met the Berlin criteria for ARDS were enrolled, and they were classified as mild (n = 50), moderate (n = 125), and severe (n = 63) ARDS, respectively. Twelve (5%) patients who originally were classified as ARDS did not continually meet the Berlin definition, and a total of 134 (56%) patients had the changes regarding the severity of ARDS from Day 0 to Day 1. The 28-day mortality rate was 49.1%, and multivariate analysis identified age, PaO2/FiO2 on Day 1, number of organ failures, and positive fluid balance within 5 days as significant risk factors of death. Moreover, the area under receiver-operating curve for mortality prediction using PaO2/FiO2 on Day 1 was significant higher than that on Day 0 (P = 0.016).PaO2/FiO2 ratio on Day 1 after applying mechanical ventilator is a better predictor of outcomes in patients with ARDS than those on Day 0.

Extraction of Aerosol-Deposited Yersinia pestis from Indoor Surfaces To Determine Bacterial Environmental Decay

Public health and decontamination decisions following an event that causes indoor contamination with a biological agent require knowledge of the environmental persistence of the agent. The goals of this study were to develop methods for experimentally depositing bacteria onto indoor surfaces via aerosol, evaluate methods for sampling and enumerating the agent on surfaces, and use these methods to determine bacterial surface decay. A specialized aerosol deposition chamber was constructed, and methods were established for reproducible and uniform aerosol deposition of bacteria onto four coupon types. The deposition chamber facilitated the control of relative humidity (RH; 10 to 70%) following particle deposition to mimic the conditions of indoor environments, as RH is not controlled by standard heating, ventilation, and air conditioning (HVAC) systems. Extraction and culture-based enumeration methods to quantify the viable bacteria on coupons were shown to be highly sensitive and reproducible. To demonstrate the usefulness of the system for decay studies,Yersinia pestis persistence as a function of surface type at 21 °C and 40% RH was determined to be >40%/min for all surfaces. Based upon these results, at typical indoor temperature and RH, a 6-log reduction in titer would expected to be achieved within 1 h as the result of environmental decay on surfaces without active decontamination. The developed approach will facilitate future persistence and decontamination studies with a broad range of biological agents and surfaces, providing agent decay data to inform both assessments of risk to personnel entering a contaminated site and decontamination decisions following biological contamination of an indoor environment. Public health and decontamination decisions following contamination of an indoor environment with a biological agent require knowledge of the environmental persistence of the agent. Previous studies on Y. pestis persistence have utilized large liquid droplet deposition to provide persistence data. As a result, methods were developed to deposit aerosols containing bacteria onto indoor surfaces, reproducibly enumerate bacteria harvested from coupons, and determine surface decay utilizing Y. pestis The results of this study provide foundational methods required to evaluate surface decay of bacteria and potentially other biological agents, such as viruses, in aerosol particles as a function of surface type and environment. Integrating the data from both aerosol and liquid deposition surface decay studies will provide medical and public health personnel with a more complete understanding of agent persistence on surfaces in contaminated areas for assessment of health risks and to inform decontamination decisions.

Extracorporeal support for pulmonary resection: current indications and results.

Extracorporeal assistances are exponentially used for patients, with acute severe but reversible heart or lung failure, to provide more prolonged support to bridge patients to heart and/or lung transplantation. However, experience of use of extracorporeal assistance for pulmonary resection is limited outside lung transplantation. Airways management with standard mechanical ventilation system may be challenging particularly in case of anatomical reasons (single lung), presence of respiratory failure (ARDS), or complex tracheo-bronchial resection and reconstruction. Based on the growing experience during lung transplantation, more and more surgeons are now using such devices to achieve good oxygenation and hemodynamic support during such challenging cases. We review the different extracorporeal device and attempt to clarify the current practice and indications of extracorporeal support during pulmonary resection.

Parameter estimation of an artificial respiratory system under mechanical ventilation following a noisy regime

Introduction: This work concerns the assessment of a novel system for mechanical ventilation and a parameter estimation method in a bench test. The tested system was based on a commercial mechanical ventilator and a personal computer. A computational routine was developed do drive the mechanical ventilator and a parameter estimation method was utilized to estimate positive end-expiratory pressure, resistance and compliance of the artificial respiratory system. Methods The computational routine was responsible for establishing connections between devices and controlling them. Parameters such as tidal volume, respiratory rate and others can be set for standard and noisy ventilation regimes. Ventilation tests were performed directly varying parameters in the system. Readings from a calibrated measuring device were the basis for analysis. Adopting a first-order linear model, the parameters could be estimated and the outcomes statistically analysed. Results Data acquisition was effective in terms of sample frequency and low noise content. After filtering, cycle detection and estimation took place. Statistics of median, mean and standard deviation were calculated, showing consistent matching with adjusted values. Changes in positive end-expiratory pressure statistically imply changes in compliance, but not the opposite. Conclusion The developed system was satisfactory in terms of clinical parameters. Statistics exhibited consistent relations between adjusted and estimated values, besides precision of the measurements. The system is expected to be used in animals, with a view to better understand the benefits of noisy ventilation, by evaluating the estimated parameters and performing cross relations among blood gas, ultrasonography and electrical impedance tomography.

Sampling and analyzing alveolar exhaled breath condensate in mechanically ventilated patients: a feasibility study

Recent studies in spontaneously breathing subjects indicate the possibility of obtaining the alveolar fraction of exhaled breath condensate (aEBC). In critically ill mechanically ventilated patients, in whom microbial colonization of the upper airways is constant, collection of aEBC could considerably add to the ability of monitoring alveolar inflammation. We designed this study to test the feasibility of collecting aEBC in mechanically ventilated critically ill patients through a dedicated apparatus, i.e. a CO2 valve combined with a condenser placed in the expiratory limb of the ventilator circuit. We also aimed to assess the adequacy of the samples obtained by measuring different markers of oxidative stress and inflammation.We enrolled 40 mechanically ventilated patients, 20 with and 20 without acute respiratory distress syndrome (ARDS). Measurements of respiratory mechanics, gas exchange and hemodynamics were obtained with a standard ventilator circuit after 30 min of aEBC collection and after inserting the dedicated collecting apparatus. Data showed that intrinsic positive end-expiratory pressure, peak and plateau pressure, static compliance and airway resistance (Raw) were similar before and after adding the collecting apparatus in both ARDS and controls. Similarly, gas exchange and hemodynamic variables did not change and 30 min collection provided a median aEBC volume of 2.100 and 2.300 ml for ARDS and controls, respectively. aEBC pH showed a trend toward a slight reduction in the ARDS group of patients, as opposed to controls (7.83 (7.62–8.03) versus 7.98 (7.87–8.12), respectively, p = 0.055)). H2O2 was higher in patients with ARDS, compared to controls (0.09 (0.06–0.12) μM versus 0.03 (0.01–0.09) μM, p = 0.043), while no difference was found in proteins content, 8-isoprostane, 4-hydroxy-2-nonhenal.In conclusion, we demonstrate, in patients receiving controlled mechanical ventilation, that aEBC collection is feasible without detrimental effects on ventilator functioning, respiratory mechanics and gas exchange. In addition, we show that the sample obtained is appropriate for compounds analysis.

Ammonia and Hydrogen Sulfide Concentrations and Emissions for Naturally Ventilated Freestall Dairy Barns

<abstract> <b><sc>Abstract.</sc></b> Concentrations and emissions of ammonia (NH₃) and hydrogen sulfide (H₂S) data for two naturally ventilated freestall dairy barns, within a one-year window of a two-year measurement effort, are presented in this article. Barn 1 (B1) had a capacity of 400 fresh-lactating Holstein cows, while barn 2 (B2) had a capacity of 850 non-fresh-lactating Holstein cows. The 10 min mean concentrations of NH₃ in the barns ranged from 0.16 to 2.85 ppm, while the concentrations of H₂S ranged from 0.0 to 135.8 ppb. The concentrations of NH₃ and H₂S in the barns were significantly below the OSHA permissible and NIOSH recommended exposure levels with respect to safety and health concerns of farm workers. Air exchange rates ranged from 7 to 74 h^-1 during all measurement periods, which met and exceeded the standard minimum ventilation rate requirements for dairy barns. Ammonia emissions ranged from 15.1 to 36.7 g d^-1 AU^-1 (20.3 to 49.5 g d^-1 cow^-1) with a mean of 21.6 g d^-1 AU^-1 (29.0 g d^-1 cow^-1). Emissions of H₂S, on the other hand, ranged from 0.0 to 1.5 g d^-1 AU^-1 (0.0 and 2.0 g d^-1 cow^-1) with an overall mean of 0.51 g d^-1 AU^-1 (0.69 g d^-1 cow^-1). In general, NH₃ emissions correlated fairly well with temperature (R² = 0.29 to 0.51). However, the relationships between NH₃ emission and wind speed were mixed, ranging from zero to moderately positive (R² = 0.01 to 0.46). Regression analyses did not indicate any significant relationships between H₂S emissions and these environmental parameters.

Lung protective vs. standard ventilation during laparoscopic surgery in obese patients. preliminary results of a randomized, controlled trial

Two different papers published recently suggested the use of a comprehensive strategy providing low tidal volumes, peep and recruiting maneuvers in patients undergoing open abdominal surgery (1,2). It is unknown whether such ventilatory approach may be feasible in patients undergoing laparoscopy, as pneumoperitoneum and Trendelenburg position may alter lung volumes and chest-wall elastance.

A ventilation technique for oxygenation and carbon dioxide elimination in CPR: Continuous insufflation of oxygen at three levels of pressure in a pig model

Pulmonary ventilation remains an important part of cardiopulmonary resuscitation, affecting gas exchange and haemodynamics. We designed and studied an improved method of ventilation for CPR, constructed specifically to support both gas exchange and haemodynamics. This method uses continuous insufflation of oxygen at three levels of pressure, resulting in tri-level pressure ventilation (TLPV). We hypothesized that TLPV improves gas exchange and haemodynamics compared to manual gold standard ventilation (GSV). In 14 pigs, ventricular fibrillation was induced and automated CPR performed for 10 min with either TLPV or GSV. After defibrillation, CPR was repeated with the other ventilation method. Gas exchange and haemodynamics were monitored. Data are presented as mean±standard error of the mean. TLPV was superior to GSV for PaO2 (163±36 mmHg difference; P=0.001), and peak AWP (-20±2 cmH2O difference; P=0.000) and higher for mean AWP (8±0.2 cmH2O difference; P=0.000). TLPV was comparable to GSV for CPP (5±3 mmHg difference; P=0.012), VCO2 (0.07±0.3 mL/min/kg difference; P=0.001), SvO2 (4±3%-point; P=0.001), mean carotid flow (-0.5±4 mL/min difference; P=0.016), and pHa (0.00±0.03 difference; P=0.002). The PaCO2 data do not provide a conclusive result (4±4 mmHg difference). We conclude that the ventilation strategy with a tri-level pressure cycle performs comparable to an expert, manual ventilator in an automated-CPR swine model.

The Potential of Bee-Generated Carbon Dioxide for Control of Varroa Mite (Mesostigmata: Varroidae) in Indoor Overwintering Honey bee (Hymenoptera: Apidae) Colonies.

The objective of this study was to manipulate ventilation rate to characterize interactions between stocks of honey bees (Apis mellifera L.) and ventilation setting on varroa mite (Varroa destructor Anderson and Trueman) mortality in honey bee colonies kept indoors over winter. The first experiment used colonies established from stock selected locally for wintering performance under exposure to varroa (n = 6) and unselected bees (n = 6) to assess mite and bee mortality and levels of carbon dioxide (CO2) and oxygen (O2) in the bee cluster when kept under a simulated winter condition at 5°C. The second experiment, used colonies from selected bees (n = 10) and unselected bees (n = 12) that were exposed to either standard ventilation (14.4 liter/min per hive) or restricted ventilation (0.24 liter/min per hive, in a Plexiglas ventilation chamber) during a 16-d treatment period to assess the influence of restricted air flow on winter mortality rates of varroa mites and honey bees. Experiment 2 was repeated in early, mid-, and late winter. The first experiment showed that under unrestricted ventilation with CO2 concentrations averaging <2% there was no correlation between CO2 and varroa mite mortality when colonies were placed under low temperature. CO2 was negatively correlated with O2 in the bee cluster in both experiments. When ventilation was restricted, mean CO2 level (3.82 ± 0.31%, range 0.43-8.44%) increased by 200% relative to standard ventilation (1.29 ± 0.31%; range 0.09-5.26%) within the 16-d treatment period. The overall mite mortality rates and the reduction in mean abundance of varroa mite over time was greater under restricted ventilation (37 ± 4.2%) than under standard ventilation (23 ± 4.2%) but not affected by stock of bees during the treatment period. Selected bees showed overall greater mite mortality relative to unselected bees in both experiments. Restricting ventilation increased mite mortality, but did not affect worker bee mortality relative to that for colonies under standard ventilation. Restricted ventilation did not affect the overall level of Nosema compared with the control. However, there was an interaction between stock, season, and time of the trial. Unselected stock showed an increase in Nosema over time in the late winter trial that did not occur in the selected stock. In conclusion, these findings suggested that restricted ventilation has potential to suppress varroa mite in overwintering honey bee colonies via a low-cost and environmentally friendly measure.

The “Spacemaker”, a New Device for Minimally Invasive Cardiothoracic Surgery: An Evaluation and Feasibility Study

Our aim was to evaluate a new inflatable lung retractor, the "Spacemaker", and its efficacy in facilitating minimally invasive cardiothoracic surgery without the need of one lung ventilation or carbon dioxide overpressure insufflation. The device was tested in 12 anesthetized pigs (90-100 kg) placed on standard endotracheal ventilation. The device was introduced into the right or left side of the chest, depending on the intended procedure to be performed, via a 3-cm incision in the fifth intercostal space. A total of seven animals were used to evaluate hemodynamic and respiratory response to the device, whereas another five animals were used to assess the feasibility of a variety of minimally invasive cardiothoracic surgical procedures. Introduction was easy and unhindered. The device was inflated up to 0.6 bar, thereby pushing the lung tissue gently away cranially, posteriorly, and caudally without interfering with pulmonary function or resulting in respiratory compromise. In addition, hemodynamics remained stable throughout the experiments. Different closed-chest surgical procedures such as left atrial appendage exclusion, pulmonary vein exposure, pacemaker lead placement, and endoscopic stabilization for coronary surgery, were successfully performed. Removal was quick and complete in all cases, and lung tissue showed no remnant atelectasis. The "Spacemaker" may represent a reliable alternative to current conventional techniques to facilitate minimally invasive cardiothoracic surgery. Further research is warranted to confirm the effectiveness and the safety of this device and to optimize the model before its use in humans and its introduction into clinical practice.

Impact of laryngeal tube use on chest compression fraction during out-of-hospital cardiac arrest. A prospective alternate month study

AimSupraglottic devices are thought to allow efficient ventilation and continuous chest compressions during cardiac arrest. Therefore, the use of supraglottic devices could increase the chest compression fraction (CCF), a critical determinant of patient survival. The aim of this study was to assess the CCF in out-of-hospital cardiac arrest (OHCA) patients ventilated with a supraglottic device. MethodsWe conducted an open prospective multicenter study with temporal clusters. OHCA patients treated by emergency nurses received either intermittent chest compressions with bag-valve mask ventilations (30:2 rhythm; BVM group); or continuous chest compressions with asynchronous ventilations by laryngeal tube (LT group). The primary endpoint was the CCF assessed using an accelerometer connected to the defibrillator. We also investigated the ease of use of the laryngeal tube. ResultsEighty-two patients were included (41 in each group); 68% were male and the median age was 68 (54–80) years. Patients and cardiac arrest characteristics did not differ between groups. The CCF was 75% (68–79%) in the LT group and 59% (51–68%) in the BVM group (p<0.01). LT insertion failed in nine out of 40 cases (23%). The median time of LT insertion was 26s (11–56s). CCF was significantly lower when LT insertion failed (58% (48–74%) vs. 76% (72–80%) when LT insertion succeeded; p=0.01). ConclusionThe use of the LT during OHCA increases the CCF when compared to standard BVM ventilation. However, the impact of LT use on mortality remains unclear.

RESPIRATORY SUPPORT OF PRETERM INFANTS AFTER EXTUBATION: COMPARISON OF CLINICAL EFFICACY OF STANDART AND HIGH FREQUENCY NON-INVASIVE VENTILATION

In animal models nasal high frequency oscillatory ventilation appears to provide better development of immature lung causing less injury. This open randomized study compared the clinical efficacy of the standard (SV) and high frequency (HFV) non-invasive (nasal) ventilation after primary extubation of very preterm infants. The study included 24 very premature infants with birth weight ≤1500 gand respiratory distress syndrome. Before the first extubation infants were randomized into the main (n = 12) or control (n = 12) group. A certain mode of respiratory support was used according to the protocol for at least 72 hrs. The primary study outcome was the need for re-intubation within 72 hrs after the initial extubation. Mortality, incidences of bronchopulmonary dysplasia (BPD) and other important complications of prematurity were also compared in these groups. The frequency of re-intubation within the first 72 hrs. of non-invasive respiratory support was similar in both groups (41.67%). No differences were observed between the groups for the total duration of respiratory support as well. The incidence of BPD was twice higher in the group of infants who were treated using nasal HFV (main group) according to physiological definition, but this difference was not significant (2 cases (16.67%) compared to 1 case (8.33%) accordingly; p = 0.78). BPD incidences according to the clinical definition were similar in the both groups (5 cases - 41.67%). The use of high-frequency non-invasive ventilation after primary extubation of very preterm infants has no obvious clinical advantages over the extubation followed by standard non-invasive ventilation.

Application of Image-Pro Plus in the Groove Filter Rod Characteristic Parameters Measurement

Basing on the Image-Pro plus (IPP) technique, a kind of groove filter rod characteristic parameters (such as groove depth, channel ventilation area, number of grooves) measurement system was build. Method: put 5 groups of standard channel ventilation area-known groove rods and 10 pre-cut self-made groove filters under the microscope with the groove sides up, adjust the intensity of the light and the focal length, take the pictures of all. Use IPP to measure all the parameters, and MINTAB to analyze the accuracy and precision of the IPP system. Results: (1) the IPP system is convenient to operate, easy to use and fast to measure the characteristic parameters such as channel ventilation areas, groove depth as well as groove numbers of the groove filters. (2) the measurements for the channel ventilation area, groove depth doesn't exist linear bias. The channel ventilation area precision index GageR&amp;R = 24.66 &lt; 30, and groove depth precision index GageR&amp;R = 26.40 &lt; 30, which means measurement precision is good.( 3)The manual measurement mode and automatic measurement mode of IPP system in regard to the measurement results bear no significant difference (P &gt; 0.05), and can be chosen for different needs. The measuring method provides help in the research of groove filters rod’ tar-reducing mechanism as well as in the increase of production process control capacity.

Neurally adjusted ventilator assist in very low birth weight infants: Current status.

Continuous improvements in perinatal care have resulted in increased survival of premature infants. Their immature lungs are prone to injury with mechanical ventilation and this may develop into chronic lung disease (CLD) or bronchopulmonary dysplasia. Strategies to minimize the risk of lung injury have been developed and include improved antenatal management (education, regionalization, steroids, and antibiotics), exogenous surfactant administration and reduction of barotrauma by using exclusive or early noninvasive ventilatory support. The most frequently used mode of assisted ventilation is pressure support ventilation that may lead to patient-ventilator asynchrony that is associated with poor outcome. Ventilator-induced diaphragmatic dysfunction or disuse atrophy of diaphragm fibers may also occur. This has led to the development of new ventilation modes including neurally adjusted ventilatory assist (NAVA). This ventilation mode is controlled by electrodes embedded within a nasogastric catheter which detect the electrical diaphragmatic activity (Edi) and transmit it to trigger the ventilator in synchrony with the patient's own respiratory efforts. This permits the patient to control peak inspiratory pressure, mean airway pressure and tidal volume. Back up pressure control (PC) is provided when there is no Edi signal and no pneumatic trigger. Compared with standard conventional ventilation, NAVA improves blood gas regulation with lower peak inspiratory pressure and oxygen requirements in preterm infants. NAVA is safe mode of ventilation. The majority of studies have shown no significant adverse events in neonates ventilated with NAVA nor a difference in the rate of intraventricular hemorrhage, pneumothorax, or necrotizing enterocolitis when compared to conventional ventilation. Future large size randomized controlled trials should be established to compare NAVA with volume targeted and pressure controlled ventilation in newborns with mature respiratory drive. Most previous studies and trials were not sufficiently large and did not include long-term patient oriented outcomes. Multicenter, randomized, outcome trials are needed to determine whether NAVA is effective in avoiding intubation, facilitating extubation, decreasing time of ventilation, reducing the incidence of CLD, decreasing length of stay, and improving long-term outcomes such as the duration of ventilation, length of hospital stay, rate of pneumothorax, CLD and other major complications of prematurity. In order to prevent barotrauma, next generations of NAVA equipment for neonatal use should enable automatic setting of ventilator parameters in the backup PC mode based on the values generated by NAVA. They should also include an upper limit to the inspiratory time as in conventional ventilation. The manufacturers of Edi catheters should produce smaller sizes available for extreme low birth weight infants. Newly developed ventilators should also include leak compensation and high frequency ventilation. A peripheral flow sensor is also essential to the proper delivery of all modes of conventional ventilation as well as NAVA.