Ventilatory Pattern Research Articles

Cardiorespiratory Changes During Prolonged Downhill Versus Uphill Treadmill Exercise.

Oxygen uptake (V̇O2), heart rate (HR), energy cost (EC) and oxygen pulse are lower during downhill compared to level or uphill locomotion. However, a change in oxygen pulse and EC during prolonged grade exercise is not well documented. This study investigated changes in cardiorespiratory responses and EC during 45-min grade exercises. Nine male healthy volunteers randomly ran at 75% HR reserve during 45-min exercise in a level (+1%), uphill (+15%) or downhill (-15%) condition. V̇O2 , minute ventilation (V̇E ) and end-tidal carbon dioxide (PetCO2) were recorded continuously with 5-min averaging between the 10th and 15th min (T1) and 40th and 45th min (T2). For a similar HR (157±3 bpm), V̇O2 , V̇E , and PetCO2 were lower during downhill compared to level and uphill conditions (p<0.01). V̇O2 and V̇E decreased similarly from T1 to T2 for all conditions (all p<0.01), while PetCO2 decreased only for the downhill condition (p<0.001). Uphill exercise required greater EC compared to level and downhill exercises. EC decreased only during the uphill condition between T1 and T2 (p<0.01). The lowest V̇O2 and EC during downhill exercise compared to uphill and level exercises suggests the involvement of passive elastic structures in force production during downhill. The lower cardiorespiratory response and the reduction in PetCO2 during downhill running exercise, while EC remained constant, suggests an overdrive ventilation pattern likely due to a greater stimulation of efferent neural factors.

Adaptive Support Ventilation Attenuates Ventilator Induced Lung Injury: Human and Animal Study.

Adaptive support ventilation (ASV) is a closed-loop ventilation, which can make automatic adjustments in tidal volume (VT) and respiratory rate based on the minimal work of breathing. The purpose of this research was to study whether ASV can provide a protective ventilation pattern to decrease the risk of ventilator-induced lung injury in patients of acute respiratory distress syndrome (ARDS). In the clinical study, 15 ARDS patients were randomly allocated to an ASV group or a pressure-control ventilation (PCV) group. There was no significant difference in the mortality rate and respiratory parameters between these two groups, suggesting the feasible use of ASV in ARDS. In animal experiments of 18 piglets, the ASV group had a lower alveolar strain compared with the volume-control ventilation (VCV) group. The ASV group exhibited less lung injury and greater alveolar fluid clearance compared with the VCV group. Tissue analysis showed lower expression of matrix metalloproteinase 9 and higher expression of claudin-4 and occludin in the ASV group than in the VCV group. In conclusion, the ASV mode is capable of providing ventilation pattern fitting into the lung-protecting strategy; this study suggests that ASV mode may effectively reduce the risk or severity of ventilator-associated lung injury in animal models.

Postnatal intermittent hypoxia enhances phrenic and reduces vagal upper airway motor activities in rats by epigenetic mechanisms.

What is the central question of this study? What are the alterations in respiratory motor activity that may underlie ventilatory dysfunctions in juvenile and adult animals exposed to postnatal chronic intermittent hypoxia? What is the main finding and its importance? Postnatal chronic intermittent hypoxia modifies the motor activity to pumping and upper airway respiratory muscles in rats, mediated by epigenetic DNA hypermethylation, enhancing resting pulmonary ventilation and predisposing to collapse of the upper airways in juvenile and adult life. Periods of apnoea, commonly observed in prematures and newborns, are an important risk factor for the development of cardiorespiratory diseases in adulthood. In the present study, we evaluated changes in pulmonary ventilation and respiratory motor pattern in juvenile and adult rats exposed to postnatal chronic intermittent hypoxia (pCIH). Newborn male Holtzman rats (P1) were submitted to pCIH (6% O2 for 30 s, every 9min, 8h a day (09.30-17.30 h)) during their first 10days of life, while control animals were maintained under normoxic conditions (20.8% O2 ). Thereafter, animals of both groups were maintained under normoxia until the experiments. Unanaesthetized juvenile pCIH rats (n=27) exhibited elevated tidal volume and respiratory irregularities (P<0.05) compared to control rats (n=7). Decerebrate, arterially perfused in situ preparations of juvenile pCIH rats (n=11) displayed augmented phrenic nerve (PN) burst amplitude and reduced central vagus nerve activity in comparison to controls (n=10). At adulthood, pCIH rats (n=5) showed enhanced tidal volume (P<0.05) and increased respiratory variability compared to the control group (n=5). The pCIH-induced changes in ventilation and respiratory motor outputs were prevented by treatment with the DNA methyltransferase inhibitor decitabine (1mgkg-1 , i.p.) during the exposure to pCIH. Our data demonstrate that pCIH in rats impacts, in a persistent way, control of the respiratory pattern, increasing PN activity to the diaphragm and reducing the vagal-related activity to laryngeal muscles, which, respectively, may contribute to improve resting pulmonary ventilation and predispose to collapse of the upper airways during quiet breathing.

Prognostic significance of oscillatory ventilation at rest in patients with advanced heart failure undergoing cardiopulmonary exercise testing

BackgroundAmong heart failure patients diagnosed as having exertional oscillatory ventilation (OV), some present with OV at rest that persists during exercise, and others develop OV only after the onset of exercise during cardiopulmonary exercise (CPX) testing. We tested whether or not there was any difference in the prognostic significance between the two abnormal breathing patterns. MethodsPatients with New York Heart Association class III-heart failure were categorized into the following 3 groups according to their ventilation pattern during the CPX: patients with an OV pattern at rest that persisted for ≥60% of the exercise test at an amplitude of ≥15% of the average resting value (group 1), patients with the same abnormal ventilatory pattern as group 1 that was observed only during exercise (group 2), and patients without any OV (group 3). The patients were followed-up for at least 2 years to assess the composite outcome of cardiac death or hospitalization for worsening heart failure. ResultsThe occurrence of the composite outcome differed significantly across the groups with its highest occurrence in group 1 (21/29 [72.4%], 15/38 [39.5%] and 48/167 [28.7%]; log-rank P < 0.001). In multivariate hazard analyses, an N-terminal pro-brain natriuretic peptide of >900 pg/mL (hazard ratio [HR] = 1.72, P = 0.04), and group 1 (HR 2.03, P = 0.02) were independently associated with the composite outcome. ConclusionsChecking for the resting OV prior to incremental exercise during CPX testing may be helpful in risk-stratification among subjects with advanced heart failure.

Veterans with Gulf War Illness exhibit distinct respiratory patterns during maximal cardiopulmonary exercise.

IntroductionThe components of minute ventilation, respiratory frequency and tidal volume, appear differentially regulated and thereby afford unique insight into the ventilatory response to exercise. However, respiratory frequency and tidal volume are infrequently reported, and have not previously been considered among military veterans with Gulf War Illness. Our purpose was to evaluate respiratory frequency and tidal volume in response to a maximal cardiopulmonary exercise test in individuals with and without Gulf War Illness.Materials and methods20 cases with Gulf War Illness and 14 controls participated in this study and performed maximal cardiopulmonary exercise test on a cycle ergometer. Ventilatory variables (minute ventilation, respiratory frequency and tidal volume) were obtained and normalized to peak exercise capacity. Using mixed-design analysis of variance models, with group and time as factors, we analyzed exercise ventilatory patterns for the entire sample and for 11 subjects from each group matched for race, age, sex, and height.ResultsDespite similar minute ventilation (p = 0.57, η2p = 0.01), tidal volume was greater (p = 0.02, η2p = 0.16) and respiratory frequency was lower (p = 0.004, η2p = 0.24) in Veterans with Gulf War Illness than controls. The findings for respiratory frequency remained significant in the matched subgroup (p = 0.004, η2p = 0.35).ConclusionIn our sample, veterans with Gulf War Illness adopt a unique exercise ventilatory pattern characterized by reduced respiratory frequency, despite similar ventilation relative to controls. Although the mechanism(s) by which this pattern is achieved remains unresolved, our findings suggest that the components of ventilation should be considered when evaluating clinical conditions with unexplained exertional symptoms.

The Dynamics of Gas Analysis Parameters in Young Males of the Magadan Region from Different Generations of Europeoid Migrants and Adaptants

Using indirect calorimetry, we examined 1632 young males aged 17 to 21 years, belonging to the Europeoid (Caucasian) race and residing permanently in the city of Magadan. Depending on the duration of adaptation to the conditions of the Northeast of Russia, all male subjects were divided into 3 groups of generation 1, 2 and 3 descendants and a group of newcomers (migrants or adaptants) residing in the Magadan Region for a short period of time (generation 0). It was established that in the lineage from generations 0 to 3 there occurred an optimization of the ventilatory characteristics of the external respiration apparatus aimed at cutting respiratory heat losses during adaptation to extreme conditions of the Northeast, i.e. a decrease in the tidal volume, tidal minute volume, and respiratory rate. Relevant rearrangements of the ventilatory pattern in subjects with a longer duration of residence under the same extreme conditions are paralleled by an improvement of oxygen transport and more efficient use of each respiratory cycle.

Hydrodynamic characteristic curves and behavior of flow around a surface-piercing propeller using computational fluid dynamics based on FVM

In this study, unsteady Reynolds-Averaged Navier-Stokes computations based on a finite volume method was used to investigate the behavior of fluid flow around an optimized surface-piercing propeller (special blade section) operating at immersion ratio of 0.3. Sliding mesh technique was applied to simulate rotational motion of the propeller. Homogenous Eulerian multiphase model including volume of fluid method was employed to solve two-phase flow field equations. As the results showed, the highest thrust and efficiency of the key blade achieved at the regions near the rotation angle of 180°. Additionally, total thrust of the blade section (0.7R) was decreased with increase of advance coefficient. In a specified advance coefficient, from rotation angle of 90°–180°, total thrust of the blade section was increased and maximum local thrust occurred at a location close to the leading edge whereas from rotation angle of 180°–270°, total thrust of the blade section was dropped and maximum local thrust position got away from the leading edge. To validate the numerical results, experimental data of SPP-841B propeller was used. Comparison between numerically simulated results, measured open water characteristics of SPP-841B and ventilation pattern of the key blade revealed an acceptable level of conformity.

Effects of volatile substance abuse on the respiratory system in adolescents

&#x0D; &#x0D; &#x0D; Aim: Inhalant abuse is a prevalent and often overlooked form of substance abuse in adolescents. Chronic inhalant abuse can damage respiratory, cardiac, renal, hepatic, and neurolog- ic systems. This study aims to determine the physiologic effects of inhaling solvents on the respiratory functions.&#x0D; Methods: The general health status of the subjects was assessed by history taking, physical examination and a questionnaire which was designed to show the severity of respiratory symp- toms. Spirometry, ventilation/perfusion scintigraphy, and high resolution computed tomography (HRCT) were performed to assess pulmonary functions and anatomy.&#x0D; Results: Thirty-one male volatile substance abusers and 19 control subjects were included in the study. The mean age of onset of inhalant use was 14.6 ± 2.2 (9-18) years and dura- tion of drug use was 3.7 ± 1.7 years. The most common respi- ratory symptoms in volatile substance abusers were nasal congestion (45.2%), sputum (38.7%), exercise intolerance (32.3%) and cough (22.6%). Results of spirometric studies showed 12 (41.4%) subjects with low FVC values &lt; 80% of predicted, indicative of restrictive ventilatory pattern in the study group. Although the difference was not statistically sig- nificant, restrictive ventilatory pattern was higher in the study group. There was no statistically significant correlation between restrictive ventilatory pattern and the age of onset/duration/frequency of inhalant abuse, respiratory symptoms and scintigraphic abnormalities. Subjects who had restrictive pattern in their pulmonary function tests were more likely to have abnormal findings at HRCT (p &lt; 0.01).&#x0D; Conclusion: This study has shown a positive correlation between volatile substance abuse and the development of restrictive ventilatory pattern, but more comprehensive stud- ies are needed for more precise conclusions.&#x0D; &#x0D; &#x0D;

Postmenstrual age at discharge in premature infants with and without ventilatory pattern instability.

To determine if ventilatory pattern instability, manifested as periodic breathing (PB) during physiologic challenge testing, affects postmenstrual age (PMA) at discharge. Eighty infants underwent challenge testing at 36 weeks PMA. Infants breathing supplemental O2 received a room air challenge (RAC, N = 51); those breathing ambient air underwent a hypoxic challenge test (HCT, N = 29). Infants were assigned one of four ventilatory control phenotypes based on the presence or absence of PB during their test, and if they passed or failed because of hypoxemia during the challenge test. There were no clinical or demographic differences between groups. Infants who passed their challenge testing were, on average, discharged 1.6 weeks sooner than those who failed. The groups of ventilatory control phenotypes differed in PMA at discharge (p = 0.0020), but those with PB were younger by PMA at discharge. Ventilatory pattern instability did not prolong time to discharge. Passing either challenge was associated with earlier discharge, suggesting these tests might identify infants who can have nasal cannula support removed and be safely discharged sooner. Most of the infants who failed their challenge tests with PB were receiving nasal cannula support. Nasal cannula support may be not only treating hypoxemia due to bronchopulmonary dysplasia (BPD), but also mitigating their ventilatory pattern instability.

CORRELATION BETWEEN CLASSROOM POPULATION, VENTILATION BACTERIAL LOADS AND THIER ANTIMICROBIAL PATTERNS IN SCHOOLS WITHIN IKOT EKPENE, NIGERIA

Indoor air of classroom in eight schools (4 nursery; NS1, NS2, NS3 and NS4, and 4 secondaries; SS1, SS2, SS3 and SS4) within Ikot Ekpene, Akwa Ibom State, Nigeria, were analyzed at ambient and populated sampling conditions using natural sedimentation on nutrient agar medium. The results revealed varying ventilation patterns in each of the classrooms, and the following airborne bacterial counts; NS1 (16.6 cfu/m3), NS2 (13.3 cfu/m3), NS3 (23.3 cfu/m3), NS4 (33.3 cfu/m3), SS1 (6.6 cfu/m3), SS2 (6.6 cfu/m3), SS3(28.3 cfu/m3) and SS4 (15 cfu/m3) at ambient sampling and 40 cfu/m3, 41.6 cfu/m3, 58.3 cfu/m3, 68.3 cfu/m3, 6.6 cfu/m3, 31.6 cfu/m3, 56.6 cfu/m3 and 25 cfu/m3 respectively at populated sampling. Bacterial isolates identified were Lactobacillus, Staphylococcus, Bacillus, Rothia, Kurthia, Corynebacterium, Pseudomonas, Brevibacterium, and Flavobacterium. Statistical analysis of the results revealed negative relationships between class area and aerobic plate counts (p&gt;0.05), class population and aerobic plate count (p&gt;0.805), and significant increase in aerobic plate counts at populated conditions over that at ambient conditions (p&lt;0.05). The results therefore point to the dimensions of classrooms, ventilation and population of the classrooms as important factors in determining the bacterial air quality, and invariably affecting the health condition of students.

Cadaveric evaluation of fluoroscopy-assisted placement of one-lung ventilation devices for video-assisted thoracoscopic surgery in dogs.

To evaluate the feasibility of fluoroscopy-assisted placement of one-lung ventilation (OLV) devices in dogs. Experimental study. Canine cadavers (n = 8) weighing between 20.2 and 37.4 kg. Thoracoscopic access with a two-port approach was established to evaluate bilateral lung ventilation patterns. Advancement of a left-sided Robertshaw double-lumen endobronchial tube (DLT) and the EZ-blocker (EZ) were evaluated under direct fluoroscopic guidance. Each dog also underwent bronchoscopy-assisted placement of an Arndt endobronchial blocker (EBB). Time to initial placement, success of creating complete OLV (after initial placement attempt and after up to two repositionings), and ease of placement score were recorded. Device position was evaluated bronchoscopically after each fluoroscopy-assisted placement attempt. Time to initial placement was significantly shorter for EZ than for DLT and EBB. The rate of successful placement after up to two repositioning attempts was 87.5%, 87.5%, and 100.0% on the right and 87.5%, 100.0%, 100.0% on the left for DLT, EZ, and EBB, respectively, and was not different between devices. Ease of placement scores were significantly higher for DLT compared with EZ and EBB on both the left and the right sides. Fluoroscopy-assisted placement of DLT and EZ appears feasible in canine cadavers. EZ-blocker placement was efficient and technically easier than DLT, but positioning must be adapted for dogs. Bronchoscopy-assisted placement of EBB remains highly successful. Fluoroscopy-assisted placement of EZ and DLT is a useful alternative to bronchoscopy-assisted placement of these OLV devices.

Small-scale testing of coal dust explosion propagation and relation to active barrier suppression systems

Abstract Coal dust explosions are a lethal threat to anyone working in an underground coal mine. Many coal mining countries including Australia and much of Europe already utilize passive barrier explosion suppressant systems but due to differences in ventilation patterns in the United States, simple passive systems such as the bagged barrier are not as cost effective. Active systems are triggered by properties of an explosion, such as pressure, heat, or light, and release or project a suppressant into the environment to suppress an explosion. To deploy an active system, the best sensor and suppressant release location and spacing must be determined; this must account for total system latency and explosive propagation speed. A 10:1 model of a longwall entry system has been developed to study the pressure wave propagation of coal dust explosions and consequent triggering of different suppressants. The scaled model, with its removable stoppings, allows multiple potential propagation pathways for an explosion to be repeatedly tested, different from typical straight shock tunnel tests. The layout also facilitates the placement of sensors and cameras to fully observe and document the tests. The pressure wave characteristics found at crosscuts and corners will aid in the development of active barrier trigger systems and spacing of suppressant release locations.

P6326Which results of the cardiopulmonary exercise test deserve greatest attention to establish the prognosis in heart failure?

Abstract Background and aim Limitation of exercise tolerance is one of the cardinal manifestations of heart failure (HF). Cardiopulmonary exercise testing (CPET) provides a thorough assessment of exercise integrative physiology involving the pulmonary, muscular, and oxidative cellular systems. We aimed to identify which data collected during a CPET shows the best prognostic performance with respect to predicting mortality or the need for heart transplantation (HT). Methods Single-centre retrospective cohort study of consecutive HF patients performing a CPET for functional and prognostic HF evaluation from October 1996 till May 2018. Left ventricular ejection fraction was not an exclusion criterion. A Cox model was fit with time to death or heart transplantation (whichever recorded first within 5 years) as the dependent variable and CPET parameters as the independent variables. Both unadjusted and adjusted covariate Cox regressions were performed. ROC curve analysis was used to determine whether the significant variables, as a model, could reliably predict the study endpoint. Results The study population consisted of 513 patients, median age 58 (IQ 16) years, and 74.9% male. The majority had reduced ejection fraction (75.4%), and the most common HF aetiology was ischemic heart disease (55.8%). During the 5-years follow up, 126 patients died and 60 underwent heart transplantation. In unadjusted Cox regression, nearly all CPET variables were significantly associated with the study endpoint. After covariate adjustment, with prior exclusion of redundant variables, three measures remained associated with the study endpoint: peak VO2 consumption (hazard ratio [HR] 0.85; 95% confidence interval [CI], 0.81–0.90); VE/VCO2 slope (HR 1.02; 95% CI, 1.00–1.02); presence of oscillatory ventilatory pattern (HR 3.73; 95% CI, 2.43–5.72). As a model, these 3 variables showed a strong discriminatory ability (c-statistic 0.87; 95% CI, 0.83–0.90) (see figure) for the study endpoint. Figure 1 Conclusion When using the CPET for prognostic stratification of HF patients, the presence of an oscillatory ventilatory pattern, the peak VO2 and the VE/VCO2 slope are the most important tools on which clinicians should focus.

Forced Oscillation Technique and Small Airway Involvement in Chronic Hypersensitivity Pneumonitis

ObjectiveHypersensitivity pneumonitis (HP) is an interstitial lung disease caused by the inhalation of specific organic antigens or low-molecular weight substances in genetically susceptible individuals. Although small airway involvement is prominent in patients with chronic HP, conventional pulmonary function tests (PFTs) are relatively insensitive to identify it. Thus, the authors aimed to evaluate resistance (R5) and reactance (X5) values at 5Hz on inspiration, expiration, and whole breath, as well as small airway resistance (R5•19) values using a forced oscillation technique (FOT) in patients with chronic HP, and their responses after bronchodilator. In addition, R5 and X5 values according to the presence or absence of mosaic attenuation on computed tomography (CT) were compared. MethodsPFTs with plethysmography, diffusing capacity of the lungs for carbon monoxide (DLCO) and FOT measurements were performed pre-bronchodilator and post-bronchodilator. High-resolution CT was performed at the same visit, and classified according to the presence or absence of mosaic attenuation. R5 and X5 values were then compared according to the presence or absence of mosaic attenuation on CT. ResultsTwenty-eight patients with chronic HP (57.1% female; mean age, 56±11.5 years; mean forced vital capacity 57±17% predicted) were evaluated. All patients had low X5 values, reflecting lower lung compliance, and only three (8%) demonstrated elevated R5 (whole-breath) values. No patients exhibited bronchodilator response in R5, X5 and R5•19 values. In patients who exhibited greater extension of mosaic attenuation (n=11), R5 and X5 values could not discriminate those with a greater presence of these areas on CT. ConclusionsThe results suggest that FOT does not help to additionally characterise concomitant small airway involvement in patients with chronic fibrotic HP who demonstrate restrictive ventilatory pattern in conventional PFTs. Nevertheless, FOT appeared to better characterise decreased lung compliance due to fibrosis through X5. Bronchodilator therapy did not appear to induce an acute response in chronic HP patients with restrictive disease. The precise role of FOT in subacute HP and obstructive chronic HP, therefore, must be evaluated.

P5423Exercise oscillatory ventilation improves the performance of prognosis scores currently used for heart failure

Abstract Background and aim Several prognostic risk scores are available for heart failure with reduced ejection fraction (HFrEF), and are used, together with other criteria, to help decide the ideal timing for listing candidates for a heart transplant. The detection of an oscillatory ventilatory pattern (OVP) during cardiopulmonary exercise testing (CPET) has been associated with more advanced HF and a worse prognosis, but was not considered in the development of all the current risk scores. We evaluated whether OVP adds significant prognostic information to four contemporary HF scores. Methods Single-centre retrospective cohort study of consecutive HFrEF patients undergoing CPET for functional and prognostic assessment from October 1996 till May 2018. The Heart Failure Survival Score (HFSS), Seattle Heart Failure Model (SHFM), Meta-analysis Global Group in Chronic Heart Failure (MAGGIC) and Metabolic Exercise Cardiac Kidney Index (MECKI) were obtained in each patient. Cox model was fit with time to death or urgent transplant (whichever came first within 2 years) as the dependent variable and OVP and respective HF score as the independent variables. We further assessed the added discriminative power by performing ROC curve comparisons. Results We studied 387 patients, median age 58 (IQR 49; 65) years, and 77% were male. The most common HFrEF aetiology was ischemic heart disease (54%). Median peak oxygen consumption was 15,7 mL/kg/min (IQR 12,8; 20,0). OVP was present in 150 (39%) patients. Over the 2-year follow-up period, 48 patients died, and 52 underwent heart transplantation (of which 25 were urgent). HFSS showed the weakest (c-statistic 0,625; 95% [CI] 0,54–0,71) and MECKI score the strongest (c-statistic 0,819; 95% [CI] 0,76–0,88) discriminatory ability. Contrasting with NTproBNP value, the presence of OVP predicted the study endpoint independently of the HF prognosis score used (see table). Adding the occurrence of OVP to the HFSS and the MAGGIC scores significantly improved their prognostic performance (see Table). Conclusion An OVP is a common finding in HFrEF patients undergoing CPET, and adds prognostic information to contemporary HF prognosis scores. Systematic evaluation of this easily available criterion may assist the decision on the appropriate timing for heart transplantation listing.

A reliable simulation for hydrodynamic performance prediction of surface-piercing propellers using URANS method

Surface Piercing Propellers (SPPs) are a particular kind of propellers which are partially submerged operating at the interface of air and water. They are more efficient than submerged propellers for the propulsion system of high-speed crafts because of larger propeller diameter, replacing cavitation with ventilation, decreasing the torque and higher efficiency. This study presents a reliable numerical simulation to predict SPP performance using Unsteady Reynolds-Averaged Navier–Stokes (URANS) method. A numerical study on 841-B SPP is performed in open water condition. The free surface is modeled by Volume of Fluid (VOF) approach and the sliding mesh technique is implemented to model the propeller rotational motion. The sliding mesh allows capturing the process of water entry and water exit of blades. The propeller hydrodynamic characteristics, the ventilation pattern and the time history of blade loads are validated through the comparison with available experimental data. For the studied case, it was found that the common grid independence study approach is not sufficient. The grid should be elaborately generated fine enough based on the flow pattern and turbulence modeling parameters in regions near the blade's tip, trailing and leading edges and over the suction side. Details of URANS simulations including optimal time-step size based on propeller revolution rate and the required number of propeller revolutions for periodical results are presented and discussed.

The displacement ventilation patterns in two parallel-connected chambers with a mechanical extraction device

This research studies the mechanical extraction ventilation in two parallel-connected chambers. A buoyancy source is located in one chamber, denoted as the forced room, and there is an extraction device in the other chamber, denoted as the extraction room. Two chambers have their own connecting openings to the ambient in the parallel-connected model. This paper focuses on the displacement ventilation pattern with a mechanical extraction device in the steady state. The flow driving forces include the buoyant and inertia forces in the mechanically ventilated space. The buoyant force results from a buoyancy source, and the inertia force, or suction force, is due to the mechanical extraction device. In this research, two different flow regimes are found in two parallel-connected chambers depending on the control extraction flow rate magnitude, and the upstream forced chamber is found to have a certain maximum flow rate limit in this configuration. When the control extraction flow rate is less than or equal to the limit value, both of the forced and extraction chambers have the same flow rate as the control extraction flow rate and the supply fluid from the exterior only goes through the forced chamber into the interior space. However, when the extraction flow rate is larger than the limit value, the enhancement flow rate of the forced chamber is more than the maximum flow rate limit, and the extraction chamber starts to bring some complementary flow rate from the exterior.

IoT network-based ANN for ventilation pattern prediction and actuation to optimize IAQ in educational spaces

Nowadays, in a user centered design approach, one of the main parameters for assessing the well-being of building spaces is Indoor Air Quality (IAQ), which can assure a crucial level of comfort and optimal conditions to preserve users’ productivity and cognitive performance. Research works in this direction mention that with 1000 ppm of CO2 concentration, a reduction of the users’ cognitive performance about 11-23% is reported and, for a concentration of 2500 ppm, the decrease reaches 44-94% compared to the performance at 600 ppm. Consequently, a correct buildings ventilation is crucial. The use of mechanical systems seems possibly to avoid the problem but indeed the existing buildings often have outdated and not flexible systems to face changing needs. Thereby, the ventilation rates are not related to people density and the static setup of HVAC systems might be an issue to maintain an acceptable level of CO2 concentration. Moreover, in school buildings, mechanical ventilation is not diffusely adopted and insufficient rates of fresh air supplied to the classrooms are connected with inappropriate IAQ, occurrence of SBS symptoms among pupils. Current technology provides easy measurement of CO2 through dedicated sensors networks. The present research uses the pilot educational building eLUX, located in the Smart Campus of the University of Brescia, to investigate the possibility to integrate IAQ data generated by IoT sensors to improve the estimation of occupancy rate in the educational spaces. The aim is to underline the relevance of the parameter to regulate properly the HVAC systems and to define opening/closing patterns for automated windows to enhance IAQ. The data collected during the monitoring phase are useful to train an Artificial Neural Network (ANN) that through an IoT communication protocol could actuate the ventilation rate control.

An assessment of the impact of natural ventilation strategies and window opening patterns in office buildings in the mediterranean basin

The paper presents the key findings of a quantitative field research examining the impact of natural ventilation on the passive cooling of an office unit, in the Mediterranean region. The relevant unit was an open-plan office unit of a typical, medium-weight office building, in the urban centre of Nicosia—the capital of Cyprus—which is located in the Eastern Mediterranean Sea. During the fieldwork, air and globe temperature as well as air velocity—in both the indoor and the outdoor environment of the unit—were in-situ measured to evaluate the impact of different ventilation strategies on passive cooling, during the summer season. The first phase of the research aimed to assess the effectiveness of three ventilation strategies: daytime, night-time, and full-day ventilation. The outcomes confirmed that night ventilation is the most effective strategy in terms of passive cooling. The second, phase of the study was an in-depth examination of night-time ventilation using four different window and/or door opening patterns, i.e., two patterns of single-sided ventilation and two patterns of cross-ventilation. To complete the fieldwork, a third, and final, phase of the research examined the impact of the airflow on the thermal comfort zone in the case study building. By using quantitative indicators of thermal performance, including the Cooling Degree-Hours (CDH), the research showed that night-time cross-ventilation window patterns, as well as elevated airflow, drastically improved the indoor thermal conditions.

The physiological phenotype of obstructive sleep apnea differs between Caucasian and Chinese patients.

The mechanisms responsible for the development of obstructive sleep apnea (phenotypic "traits") are known to differ between individuals and may differ across ethnicities. We aimed to examine whether loop gain, arousal threshold, pharyngeal collapsibility and muscle compensation differ between Chinese and Caucasian individuals with OSA. We noninvasively determined the relative contribution of loop gain, arousal threshold, pharyngeal collapsibility, and muscle compensation from the ventilatory flow pattern recorded during a standard clinical polysomnography in a cohort of age and AHI matched Caucasian and Chinese patients with moderate-severe OSA (n = 90). Chinese participants had significantly more collapsible pharyngeal airways as indicated by a lower Vpassive (68.9 [51.5-75.2] vs. 74.0 [65.1-80.4] %Veupnea, U = 703, p = 0.012), but less ventilatory control instability as indicated by a lower loop gain (0.60 [0.50-0.67] vs. 0.63 [0.57-0.81], U = 762, p = 0.043) compared with Caucasian participants. Further, multiple logistic regression analyses demonstrated that the combined pharyngeal collapsibility (Vpassive) and loop gain traits help to better explain the differences between the groups beyond upper-airway collapsibility alone. No statistically significant group differences were found in muscle compensation or arousal threshold traits between groups. Individuals of Chinese descent appear to have OSA that is driven much more by the relative contribution of their anatomical predisposition and to a lesser extent nonanatomical causes compared with Caucasians. Future research should focus on determining if Chinese versus Caucasian ethnicity is an important contributing factor to clinical outcomes and therapeutic responses in OSA.