Mean Ventilation Rate Research Articles

Assessing classroom ventilation rates using CO2 data from a nationwide study of UK schools and identifying school-wide correlation factors

Per-person ventilation rates were assessed from data measured in 322 UK schools throughout the Autumn term, 2023. It was found that the overall mean ventilation rate was 5.3 L s−1 p−1; rising to 6.8 L s−1 p−1 during warmer weather and falling to 3.8 L s−1 p−1 during colder weather. Daily mean CO2 levels recorded in the majority of schools consistently fell below the 1500 ppm threshold within government school ventilation guidance but the contribution of relatively few very high CO2 levels in some classrooms shows the need for targeted improvement and highlights the value of large-scale datasets. Exceedance of the 1500 ppm threshold rose to approximately 20% when the daily mean outdoor temperature fell to around 5 °C, indicating a barrier to ventilation. Controlling for outdoor temperature as a covariate, analysis of the CO2 measurements indicated schools in more-deprived regions, state-funded schools (relative to private), and secondary schools (relative to primary) exhibited statistically-significant higher CO2 concentration. Reassuringly, these findings remained unchanged when the analysis was deployed on estimated per-person ventilation rates; except that this enhanced analysis accounted for the greater CO2 production associated with older children and demonstrated that ventilation rates were not significantly different between primary and secondary schools.

Long term monitoring of CO2 levels and ventilation rates in a naturally ventilated residential apartment

Indoor CO2 levels became particularly topical during the recent COVID-19 pandemic. In this study a long-term investigation of indoor CO2 levels in a 1970s built residential apartment in single occupancy is presented. Three NDIR CO2 sensors were used to measure CO2 levels over a one-year period. Mean CO2 levels over this period were 1278 ± 504 ppm, with elevated CO2 levels of greater than 2000 ppm not uncommon. Subsequent investigations used the single zone mass balance model and the decay of CO2 in the absence of occupants to estimate the ventilation rates in various configurations. A mean natural ventilation rate of 0.16 ACH was estimated with all windows closed. Opening fan light windows resulted in a mean ventilation rate of 2.86 ACH whereas opening all windows increased the mean ventilation rate to 19.1 ACH. Evidence was observed of the effect of both wind speed and indoor-outdoor temperature difference on the ventilation rates. It was concluded that with all windows closed the natural infiltration rate was insufficient to maintain optimal indoor air quality even in single occupancy. Opening the fan light windows was sufficient to achieve satisfactory indoor air quality but insufficient for the effective inhibition of airborne disease transmission.

CFD simulation of pumping ventilation with two asymmetrically arranged openings on the rear wall in a three-story isolated building

Pumping ventilation, driven by periodic vortex shedding, can effectively improve the ventilation rate of single-sided ventilation. Previous studies on pumping ventilation mainly considered symmetric opening conditions, while the asymmetric opening distribution has not been well studied. Therefore, this study investigates the pumping ventilation of an isolated three-story building with asymmetric opening conditions using computational fluid dynamics (CFD) simulations. Unsteady Reynolds-averaged Navier-Stokes (URANS) method with SST k-ω turbulent model is adopted to conduct the CFD simulations. The effects of horizontal translation distances, internal partitions, and inter-floor interference on time-averaged and fluctuating ventilation rates are investigated. The simulation results show that the mean ventilation rate is larger than the fluctuating ventilation rate. The mean ventilation rate increases while the fluctuating ventilation rate decreases with the increase of the horizontal translation distance. In addition, the internal partition decreases the pumping ventilation rate primarily by reducing the fluctuating ventilation rate rather than the mean ventilation rate. Furthermore, the ventilation rates of the 2nd floor are promoted by simultaneous pumping ventilation of the 1st and 3rd floors compared to the situation that only the 2nd floor is ventilated. The ventilation rates of the 1st floor are the largest, and of the 3rd floor are the lowest. The findings of this study benefit the deeper understanding of pumping ventilation and provide theoretical guidance on the opening designs of multi-story buildings for better ventilation efficiency.

Effects of acetaminophen exposure on behavior and erythrocyte nuclear morphology of juvenile Oreochromis niloticus

The occurrence of pharmaceuticals in the environment can have undesirable effects on nontarget animals, including fish. The present experiment assessed the effects of subchronic exposure to waterborne acetaminophen (N-acetyl-p-aminophenol) (APAP) on selected behavioral aspects (physical avoidance response, ventilation rate, and food detection rate) and erythrocyte nuclear abnormality (ENA) in juvenile Oreochromis niloticus. Two groups of fish were exposed to APAP dissolved in aged municipal water (T1: 2 mg/L and T2: 10 mg/L) for 8 weeks in three replicates (n = 7 fish per tank), alongside a control group (C) without APAP. APAP-exposed fish spent significantly (p < .05) longer time to detect food (T1: 32.6 ± 4.55 s and T2: 39.6 ± 4.66 s) compared to the control group (19.9 ± 2.46 s). Both APAP-exposed groups exhibited attenuated physical avoidance responses (76.7%, 68.7%, and 87.3% in T1, T2, and C, respectively) and a lower mean ventilation rate compared to the control group (194.5 ± 15.5, 179.1 ± 11.6, and 233.2 ± 19.0 per min in T1, T2, and C, respectively). The frequency occurrence of ENA types such as bi-nucleated, notched nuclei, lobed nuclei, and blebbed nuclei (except micronuclei) was significantly higher (p < .05) in APAP-exposed groups compared to the control, with more pronounced effects in the T2 group. The study concludes that APAP exposure prompts significant alterations in behavior and erythrocyte nuclear morphology, emphasizing the value of monitoring and regulating the entry of pharmaceuticals, including APAP, into aquatic environments to prevent unintended effects on non-target organisms like Oreochromis niloticus.

Association between the presence of an advanced airway and ventilation rate during pediatric CPR: A report from the Videography in Pediatric Resuscitation (VIPER) collaborative

ObjectiveTo determine the association between presence of an advanced airway during pediatric cardiopulmonary resuscitation (CPR) and ventilation rates. MethodsProspective observational study, January 2017 to June 2020. Patients ≤18 years receiving CC for ≥2 minutes were enrolled. Ventilation rate and type of airway (advanced airway (AA), either endotracheal tube (ETT) or supraglottic airway (SGA); or natural airway (NA)) were collected from video review and analyzed in ‘CPR segments’ (periods of CPR by individual providers). Ventilation rate (breaths per minute, bpm) was calculated for each segment; hyperventilation was defined as >12 bpm according to 2015 American Heart Association guidelines. Univariate analysis between airway type was done by χ2 testing. Multivariate regression was used to determine the association between the presence of AA with hyperventilation while controlling for within-patient covariance. Results779 CPR segments from 94 CPR event were analyzed. The mean ventilation rate per CPR segment across all events was 22 bpm (±16 bpm)). Mean ventilation rates were higher with AA, either ETT (24 ± 17 bpm) or SGA (34 ± 19 bpm), than with NA (17 ± 14, p < 0.001). Hyperventilation occurred more often with AA in place (ETT: 68%; SGA: 96%; NA: 43%; p < 0.001). The presence of AA was independently associated with hyperventilation (AOR 9.3, 95% CI 4.3–20.1). ConclusionsDuring pediatric CPR, hyperventilation occurs more often with an AA in place than during CPR with NA. Future research should focus on respiratory physiology during pediatric CPR to determine optimal ventilation rate(s) during pediatric cardiac arrest.

Associations between illness-related absences and ventilation and indoor PM2.5 in elementary schools of the Midwestern United States

This study monitored indoor environmental data in 144 classrooms in 31 schools in the Midwestern United States for two consecutive days every fall, winter, and spring during a two-year period; 3,105 pupils attended classrooms where the measurements were conducted. All classrooms were ventilated with mechanical systems that had recirculation; there were no operable exterior windows or doors. The daily absence rate at the student level and demographic data at the classroom level were collected. The overall mean ventilation rate, using outdoor air, was 5.5 L/s per person (the corresponding mean carbon dioxide concentrations were < 2,000 ppm), and the mean indoor PM2.5 was 3.6 μg/m3. The annual illness-related absence rate at the classroom level was extracted from the student-level absence data and regressed on measured indoor environmental parameters. Significant associations were found. Every 1 L/s per person increase in ventilation rate was associated with a 5.59 decrease in days with absences per year. This corresponds to a 0.15% increase in the annual daily attendance rate. Every additional 1 μg/m3 of indoor PM2.5 was associated with a 7.37 increase in days with absences per year. This corresponds to a 0.19% decrease in the annual daily attendance rate. No other relationships were significant. Present results agree with the previously demonstrated benefits of reduced absence rates when classroom ventilation is improved and provide additional evidence on the potential benefits of reducing indoor inhalable particles. Overall, reduced absence rates are expected to provide socioeconomic benefits and benefits for academic achievements, while higher ventilation rates and reduced particle levels will also contribute to reduced health risks, including those related to airborne respiratory pathogens.

Metabolic Cost and Mechanical Efficiency of a Novel Handle-Based Device for Wheelchair Propulsion.

To investigate differences in metabolic cost and gross mechanical efficiency of a novel handlebased wheelchair propulsion device and to compare its performance with conventional push-rim propulsion. Double-group comparative study between 2 different propulsion methods. Eight paraplegic individuals and 10 non-disabled persons. Participants performed the same exercise using a push-rim device and the novel handle-based device on a wheelchair- based test rig. The exercise consisted of a combined submaximal and maximal test. Power output, oxygen uptake, ventilation, respiratory exchange ratio and heart rate were recorded continuously during the tests. Analysis of variance was performed to determine the effects of group, mode and on power output. Submaximal exercise resulted in a higher efficiency for the novel device and significant main effects of propulsion mode on all investigated parameters, except heart rate. On the respiratory exchange ratio, a significant interaction effect was found for both mode and group. The maximal exercise resulted in a higher peak power output and lower peak heart rate during propulsion using the handle-based device. A significant main effect on mode for mean peak power output, ventilation and heart rate was also observed. Wheelchair propulsion using the handle-based device resulted in lower physical responses and higher mechanical efficiency, suggesting that this novel design may be well suited for indoor use, thereby offering an attractive alternative to pushrim wheelchairs.

Physiological Responses and Performance During a 3-Minute Cycle Time Trial: Standard Paced Versus All-Out Paced.

To compare performance and physiological responses between a standard-paced 3-minute time trial (TTSP, ie,pacing based on normal intention) and a consistently all-out-paced 3-minute time trial (TTAOP). Sixteen well-trained male cyclists completed the TTSP and TTAOP, on separate days of testing, on a cycling ergometer with power output and respiratory variables measured. Time trials were preceded by 7 × 4-minute submaximal stages of increasing intensity with the linear relationship between power output and metabolic rate used to estimate the contribution from aerobic and anaerobic energy resources. The time course of anaerobic and aerobic contributions to power output was analyzed using statistical parametric mapping. Mean power output was not different between the 2 pacing strategies (TTSP = 417 [43] W, TTAOP = 423 [41] W; P = 0.158). TTAOP resulted in higher peak power output (P < .001), mean ventilation rate (P < .001), mean heart rate (P = .044), peak accumulated anaerobically attributable work (P = .026), post-time-trial blood lactate concentration (P = .035), and rating of perceived exertion (P = .036). Statistical parametric mapping revealed a higher anaerobic contribution to power output during the first ∼30 seconds and a lower contribution between ∼90 and 170 seconds for TTAOP than TTSP. The aerobic contribution to power output was higher between ∼55 and 75 seconds for TTAOP. Although there was no significant difference in performance (ie,mean power output) between the 2 pacing strategies, differences were found in the distribution of anaerobically and aerobically attributable power output. This implies that athletes can pace a 3-minute maximal effort very differently but achieve the same result.

Abstract 11488: Ventilation Rate and Sustained Return of Spontaneous Circulation in In-Hospital Cardiac Arrest: Is More Better?

Introduction: Current consensus holds that CPR must balance chest compressions and ventilation rate (VR), with a low VR being essential for venous return and cardiac output. AHA guidelines recommend a VR of 10 ventilations per minute (vpm) after advanced airway placement. We sought to examine VR adherence and its impact on end-tidal CO 2 (ETCO 2 ) and ROSC &gt;20 minutes. Methods: This is a retrospective analysis of data from AWARE II, a multicenter prospective observational study of adult in-hospital cardiac arrest (IHCA) outcomes at 14 US and UK sites. Inclusion criteria were: 1) adult patient in CA, 2) advanced airway already in place or placed during the CA, and 3) at least one minute of VR and ETCO 2 data available after removal of the last minute of CPR in subjects achieving ROSC (due to the rise of ETCO 2 just prior to ROSC). Results: A total of 563 subjects were enrolled in the parent study. Of these, 225 had ETCO 2 and VR tracings available, and 201 had sufficient data for inclusion. Mean age was 69.3 (range 18-100), patients were 63.7% male, and 16.4% had a shockable initial rhythm. A total of 116 subjects (57.7%) achieved ROSC, which was sustained in 76 (37.8%), leading to survival to hospital discharge with favorable neurological outcomes in 9 (4.5%). Mean VR was 16.3 vpm, with 171 (85.1%) subjects being ventilated in excess of guidelines; only 16 (8.0%) subjects received 8-10 vpm. Higher VR had a weak but significant association with increased mean ETCO 2 (linear R 2 = 0.11, p &lt; 1x10 -6 ) and sustained ROSC (OR 1.05; 95% CI: 1.01-1.11; p = 0.02). Patients with sustained ROSC had a significantly higher VR at 17.7 vpm than those without sustained ROSC at 15.6 vpm (p = 0.007). Patients receiving a VR close to AHA guidelines (6-12 vpm) had a significantly lower rate of sustained ROSC (26.1%, n = 46) than patients receiving &gt;12 vpm (42.0%, n = 148) (OR 2.30; 95% CI: 1.08-4.89; p = 0.031 using a multivariate model including patient age, shockable initial rhythm, known cardiac disease, witnessed IHCA, and use of mechanical compressions). Conclusions: VR within AHA guidelines is rare during IHCA. However, ventilation in excess of current guidelines may increase rates of sustained ROSC, an essential predicate to survival. AHA guidelines on VR in CPR with an advanced airway may not yet be optimized.

Indoor air quality in schools in Beijing: Field tests, problems and recommendations

This study investigated indoor CO2 and PM2.5 real-time concentrations together with air temperature, humidity and air-cleaning effectiveness of 33 classrooms in 21 schools in Beijing, China by natural ventilation with air cleaners (NV system) compared to mechanical ventilation with fresh air ventilators (MV system).We found that: (1) The proportions of PM2.5 concentrations >37.5 μg/m3 when the classrooms were occupied were 28 % and 31 % in MV and NV classrooms. (2) During periods of severe ambient pollution, the averaged PM2.5 I/O ratio was 0.47. (3) The proportions of CO2 concentrations >1000 ppm when the classrooms were occupied were 40 % and 60 % in MV and NV classrooms, although we note that the maximum CO2 concentration in NV classrooms occasionally exceeded 5000 ppm. (4)The mean ventilation rate was only 1.9 L/(s⋅person) during class in NV classrooms, and the air exchange rates (AERs) for NV and MV classrooms were smaller by 58 % and 4 % during class in times of severe ambient pollution than during those days that ambient PM2.5 ≤35 μg/m3. (5) During the days close to the beginning or end of central space heating, both MV and NV classrooms had indoor air temperatures lower than the 18 °C mandated by the Chinese Thermal Comfort Standard (GB/T 17225-2017). (6) Although MV systems showed lower energy efficiency than NV systems in removing PM2.5 in classrooms, the benefits of CO2 reduction and ventilation rates increase afforded by MV systems are important. These findings can help to identify or develop a suitable ventilation system (NV or MV system) and an operating strategy in classrooms in severe ambient pollution regions.

Comparison of direct and indirect determinations of dynamic ventilation rate in a modern dairy free stall barn

Reliable estimation of the ventilation rate (VR) in intensive livestock buildings is necessary for studying building environmental control strategies and predicting indoor air quality and air emissions. As direct air exchange measurements are time-consuming and expensive, it is environmentally inefficient to measure livestock building VR continuously in practice. Hence, indirect VR estimation methods have been widely used in modelling environmental control and air emissions, and also to measure airflow in the field. The accuracy of indirect measurement methods needs to be evaluated by comparing with direct measurements. In this study, the direct and indirect methods of determining hourly and daily mean VRs were applied to a mechanically-ventilated dairy free stall barn monitored by the 24-month National Air Emissions Monitoring Study. The direct method was used to continuously monitor fan rotational speeds, and differential static pressures, coupled with periodic in-situ fan performance assessments, to calculate the VR. The indirect method consisted of estimating the VR using CO2 concentration measurements and the CO2 mass balance method. The average daily and hourly means (mean±SD) of directly measured barn ventilation rates for two years were (246±73) m3/s and (245±77) m3/s, respectively. The average daily and hourly means (mean±SD) of barn ventilation rates estimated by the CO2 mass balance method were (287±93.4) m3/s and (287±118) m3/s, respectively. Correlation analyses showed a strong correlation between the indirect CO2 mass balance method and direct measurement methods (r=0.93 for daily means and r=0.85 for hourly means). Keywords: dynamic ventilation rate, modern dairy, free stall barn, carbon dioxide, mass balance, dairy cow, direct and indirect determination, comparison DOI: 10.25165/j.ijabe.20201306.5767 Citation: Zou B, Heber A J, Shi Z X, Du S H, Jin Y, Lim T T. Comparison of direct and indirect determinations of dynamic ventilation rate in a modern dairy free stall barn. Int J Agric & Biol Eng, 2020; 13(6): 41–46.

Comparison of cardiopulmonary resuscitation that applied synchronous 30 compressions–2 ventilations with that applied asynchronous 110/min compression–10/min ventilation: A mannequin study

Background: CPR model of a resuscitation to be ventilated with a bag valve mask constitutes a discussion when evaluated with the current guidance. Objective: This study aims to compare the synchronous (30–2) ventilation–compression method with asynchronous 110/min compression–10/min ventilation in cardiac arrests where an advanced airway management is not applied and where ventilation is provided by a bag valve mask on a mannequin. Methods: This simulation trial was performed using two clinical cardiopulmonary resuscitation scenarios: an asynchronous scenario with 10 ventilations per minute asynchronously when compression is applied as 110 compression per minute and a synchronous scenario in which 30 compressions:2 ventilations were performed synchronously. A total of 100 people in 50 groups applied these two scenarios on mannequin. Ventilation and compression data of both scenarios were recorded. Results: Evaluating the compression criteria in both the scenarios performed by 50 groups in total, in terms of all criteria except compression fraction, there was no statistically difference between the two scenarios (p &gt; 0.05). Compression fraction values in the asynchronous scenario were found to be statistically significantly higher than the synchronous scenario (96.02 ± 2.35, 81.34 ± 4.42, p &lt; 0.001). Evaluating the ventilation criteria in both the scenarios performed by 50 groups in total; there was a statistically significant difference in all criteria. Mean ventilation rate of the asynchronous scenario was statistically higher than the synchronous scenario (7.22 ± 2.42, 5.08 ± 0.75, p &lt; 0.001). Mean ventilation volume of the synchronous scenario was statistically higher than the asynchronous scenario (353.24 ± 45.46, 527.40 ± 96.60, p &lt; 0.001). Ventilation ratio in sufficient volume of the synchronous scenario was statistically higher than the asynchronous scenario (36.84 ± 14.47, 75.00 ± 21.24, p &lt; 0.001). Ventilation ratio below the minimum volume limit of the asynchronous scenario was statistically higher than the synchronous scenario (62.48 ± 14.72, 17.86 ± 19.50, p &lt; 0.001). Conclusion: In our study, we concluded that the cardiopulmonary resuscitation applied by the synchronous method reached better ventilation volumes. Evaluating together with any interruption in compression, comprehensive studies are needed to reveal which patients would benefit from this result.

Stress Responses and Gonadosomatic Index of Red Tilapia (Oreochromis Spp.) Subjected To Visual And Physical Interactions

Red tilapia is a popular cultured species due to its attractive color and excellent growth and feed conversion rates. In this study, the effect of visual and physical interactions on the ventilation rate (VR), eye color pattern (ECP), and Gonadosomatic Index (GSI) of red tilapia was evaluated. There were four treatments in the study: T1 (No Interaction); T2 (Visual Interaction); T3 (Visual and Physical Interactions) and; T4 (Physical Interaction). Changes in VR and ECP were monitored for 15 days, while GSI was computed at the end of the study. The mean VR and ECP of the red tilapia exposed to visual and/or physical interactions were significantly higher compared to those in the control (P˂0.05). However, the fastest VR and darkest ECP were observed in T3. This conforms to the results of GSI wherein T3 had the lowest GSI which may be due to the higher level of stress experienced by fish in T3 compared to other treatments. On the other hand, T4 had the highest female GSI as opposite sex fish were exposed to physical interaction. Communication between sexual partners modulates reproductive behavior.

Particle Mass Concentrations and Number Size Distributions in 40 Homes in Germany: Indoor-to-Outdoor Relationships, Diurnal and Seasonal Variation

Few studies investigated residential particle concentration levels with a full picture of aerosol particles from 10 nm to 10 µm size range with size-resolved information, and none was performed in central Europe in the long-term in multiple homes. To capture representative diurnal and seasonal patterns of exposure to particles, and investigate the driving factors to their variations, measurements were performed in 40 homes for around two weeks each in Leipzig and Berlin, Germany. These over 500 days’ measurements combined PM10 and PM2.5 mass concentrations, particle number concentration and size distribution (PNC and PNSD, 10–800 nm), CO2 concentration, and residential activities diary into a unique dataset. Natural ventilation was dominated, the mean ventilation rate calculated from CO2 measurements was 0.2 h–1 and 3.7 h–1 with closed and opened windows, respectively. The main findings of this study showed that, the residents in German homes were exposed to a significantly higher mass concentration of coarse particles than outdoors, thus indoor exposure to coarse particles cannot be described by outdoors. The median indoor PNC diurnal cycles were generally lower than outdoors (median I/O ratio 0.69). However, indoor exposure to particles was different in the cold and warm season. In the warm season, due to longer opening window periods, indoor sources’ contribution was weakened, which also resulted in the indoor PNC and PNSD being very similar to the outdoors. In the cold season, indoor sources caused strong peaks of indoor PNC that exceeded outdoors, along with the relatively low penetration factor - 0.5 for all size ranges, and indoor particle losses, which was particularly effective in reducing the ultrafine PNC, resulting in a different particle exposure load than outdoors. This study provides a detailed understanding of residential particle exposure in multiple homes, facilitating future studies to assess health effects in residential environments.

Evaluating single-sided natural ventilation models against full-scale idealised measurements: Impact of wind direction and turbulence

Commonly single-sided natural ventilation is used in temperate climates to provide comfortable and healthy indoor environments. However, within built-up areas it is difficult to predict natural ventilation rates for buildings as they depend on many flow factors and opening type. Here, existing models are evaluated using the nine-month Refresh Cube Campaign (RCC). Pressure-based ventilation rates were determined for a small opening (1% porosity) in a cubical test building (side = 6 m). The building was isolated and then sheltered in a limited staggered building array to simulate turbulent flows in dense urban areas. Internal and external flow, temperature and pressure measurements captured a wide range of scales of variability. Although the Warren and Parkins (1985, WP85) model performed best for 30-min mean ventilation rates, all four models tested underestimated ventilation rates by a factor of 10. As wind dominated the stack effect, new coefficients were derived for the WP85 wind-driven model as a function of wind angle. Predictions were mostly improved, except for directions with complex flow patterns during the sheltered case. For the first time, the relation between ventilation rate and turbulence intensity (TI) around a full-scale building was tested. Results indicate that the wind-driven model for single-sided ventilation in highly turbulent flows (0.5 < TI < 4) can be improved by including TI as a multiplicative factor. Although small window openings with highly turbulent flows are common for sheltered buildings in urban areas, future model development should include a variety of configurations to assess the generality of these results.

Comparison of Ventilator’s Work of Breath Cased on Constant Flow Nasal CPAP Through Pressure Limited and Electronic Feedback Pressure Control Mechanisms in the Treatment of RDS in Neonates Weighing About 1000 Grams

Background: Continuous distending pressure (CDP) is considered as standard care in neonates with decreased pulmonary compliance. Concerns regarding the implementation of non-invasive CDP in a respiratory cycle in order to establish an optimal level of functional residual capacity (FRC) abound in the related literature. Examples include how to manage gas leakage in the interface, no imposed increased work of breath (WOB) on patients and prevention of applying trans-pulmonary pressure levels leading to metabolic acidosis. Following the development of autoflow hardware, pressure control (PC) respiratory pattern was defined in the field of mechanical ventilation (MV) in order to compensate for gas leakage in interface or compensate for pressure drop and increased CDP pressure level in respiratory phases of inspiration and expiration. Objectives: The study aimed at decreasing WOB in neonates with RDS using pressure control-nCPAP. Methods: This study was a retrospective clinical trial performed on 70 neonates weighing about 1000 grams with RDS. Participants were randomly assigned into two respiratory support groups based on the use of pressure limited nCPAP (PL-nCPAP) and pressure control nCPAP (PC-nCPAP). Each group consisted of 35 infants compared in terms of their demographic characteristics, duration of non-invasive respiratory support, rapid shallow breathing (RSB) index, ventilator’s WOB, need for MV, need for surfactant administration, chronic lung diseases, pneumothorax, intra-ventricular hemorrhage (IVH) and death. Results: No significant difference was observed between the mean time of non-invasive respiratory support and the need for MV, between the incidence of pneumothorax and IVH and also between the mortality rate and degree of involvement in chronic lung diseases in the two groups. The mean respiratory ventilation rate of ventilator’s WOB in PC-nCPAP group was significantly higher than that of PL-nCPAP group. The mean RSB index was also significantly higher in PL-nCPAP group than in PC-nCPAP group. Finally, the mean of surfactant administration in PL-nCPAP group was significantly higher than that in PC-nCPAP group. Conclusions: In this study, ventilator’s WOB in PC-nCPAP group, which was significantly higher than that of PL-nCPAP group, can be explained by significantly higher RSB index in PL-nCPAP group and significantly lower mean surfactant prescription in PC-nCPAP group.

Ventilation feedback device for manual ventilation in simulated respiratory arrest: a crossover manikin study

BackgroundStudies have shown that providing adequate ventilation during CPR is essential. While hypoventilation is often feared by most caregivers on the scene, the most critical problem remains hyperventilation. We developed a Ventilation Feedback Device (VFD) for manual ventilation which monitors ventilatory parameters and provides direct feedback about ventilation quality to the rescuer. This study aims to compare the quality of conventional manual ventilation to ventilation with VFD on a simulated respiratory arrest patient.MethodsForty healthcare providers were enrolled and instructed to ventilate a manikin simulating respiratory arrest. Participants were instructed to ventilate the manikin for 5 min with and without the VFD in random order. They were divided in two groups of 20 people, one group ventilating through a mask and the other through an endotracheal tube.ResultsVentilation with the VFD improved from 15 to 90% (p < 0.001) with the mask and from 15 to 85% (p < 0.001) with the endotracheal tube (ETT) by significantly reducing the proportion of hyperventilation. The mean ventilation rates and tidal volumes were in the recommended ranges in respectively 100% with the mask and 97.5% of participants with the ETT when using the VFD.ConclusionVFD improves the performance of manual ventilation by over 70% in different simulated scenarios. By providing the rescuer direct feedback and analysis of ventilatory parameters, this device can significantly improve ventilation while performing CPR and thus save lives.

Experimental analysis of a PCM integrated solar chimney under laboratory conditions

The objective of this work is to experimentally investigate the impact of integrating a Phase Change Material (PCM) on the performance of two different laboratory solar chimney prototypes, rendering it a viable option for yearlong use. It has been stated that solar chimneys can provide constant ventilation and increase air quality in a building. This study aims to provide a different approach in means of improving the current performance of solar chimneys as, nowadays, it is mostly pursued through the modification of the inclination, the air gap size or the inlet/outlet dimensions. The solar chimney prototype mainly analysed in this work is built with 2 cm plywood plates with a thermal conductivity of 0.15 W/mK with a volume of 3.50×1.00×0.30 m. After a 6 h charge period, a mean ventilation rate above 70 m3/h can be achieved with a relative low gain of 550 W/m2 provided by a series of 7 halogen lamps directed towards an effective collector area of 3.00 m2. The results obtained in this work show that PCM integration provides a higher ventilation rate and a slower decrease during ventilation only phases (6 h discharge), where the halogen lamps do not provide any energy to the solar chimney. Overall, the implementation of paraffinic PCMs in solar chimneys could be an economically viable option for hybrid design solutions to create a healthy indoor environment within residential buildings through renewable solar energy.

Outdoor measurement of wall pressure on cubical scale model affected by atmospheric turbulent flow

Most studies on indoor ventilation have utilized wind-tunnel experiments (WTEs) or computational fluid dynamics based approaches under well-controlled flow conditions. However, the effects of urban boundary layer flow with variable wind directions and various turbulence scales on the ventilation driven by the pressure differences between the upwind and downwind sides of a building within a block array is still under discussion. Therefore, we conducted outdoor experiments at comprehensive outdoor scale model (COSMO) experiment sites in an urban climate to clarify the relationships between the building wall pressure differences and the approaching flow. The pressure coefficients for the outdoor site were comparable with those obtained during previous WTEs. Accordingly, temporal variations in the wind speed and pressure coefficient on the target block were investigated in detail using low-pass filtering operations. The relationships between the filtered wind speed and the pressure differences indicate that the slower temporal variations in the wall pressure showed good agreement with the filtered approaching flow. In addition, the correlation coefficient between the filtered wind speed and the wall pressure differences quantified the apparent coherence between the turbulent flow and the ventilation rate. Furthermore, the statistics of the ventilation rate were determined based on the conventional model to clarify the effects of the turbulent flow on the natural ventilation rate. The ratios between the mean and short-term ventilation rates imply that the short-term ventilation rate presented dramatic temporal fluctuations owing to the various scale turbulence generated by the atmospheric flow.

The effect of ventilation rate on outcome in adults receiving cardiopulmonary resuscitation

AimTo investigate whether a ventilation rate ≤10 breaths min−1 in adult cardiac arrest patients treated with tracheal intubation and chest compressions in a prehospital setting is associated with improved Return of Spontaneous Circulation (ROSC), survival to hospital discharge and one-year survival with favourable neurological outcome, compared to a ventilation rate >10 breaths min−1. MethodsIn this retrospective study, prospectively acquired data were analysed. Ventilation rates were measured with end-tidal CO2 and ventilation pressures. Analyses were corrected for age, sex, compression rate, compression depth, initial heart rhythm and cause of cardiac arrest. Results337 of 652 patients met the inclusion criteria. Hyperventilation was common, with 85% of the patients ventilated >10 breaths min−1. The mean ventilation rate was 15.3 breaths min−1. The corrected odds ratio (OR) of ventilating >10 breaths min−1 for achieving ROSC was 0.91 (95% CI: 0.49 – 1.71, p = 0.78), the uncorrected OR of ventilating >10 breaths min−1 for survival to hospital discharge was 0.91 (95% CI: 0.30 – 2.77, p = 0.78), and the uncorrected OR of ventilating >10 breaths min1 for one-year survival with a favourable neurological outcome was 0.59 (95% CI: 0.19 – 1.87, p = 0.32). A logistic regression with continuous ventilation rate showed no significant relation with ROSC, and a ROC curve for ROSC showed a poor predictive performance (AUC: 0.52, 95% CI: 0.46 – 0.58), suggesting no other adequate cut-off value for ventilation rate. ConclusionA ventilation rate ≤10 breaths min−1 was not associated with significantly improved outcomes compared to a ventilation rate >10 breaths min−1. No other adequate cut-off value could be proposed.