Simple Ventilation Research Articles

Ventilation effectiveness and incomplete mixing in air distribution design for airborne transmission

How ventilation should be arranged to be effective at reasonable air change rates is one key question as ventilation criteria and standard airborne disease transmission models are based on the well-mixed assumption, but air distribution patterns lead to non-uniform spatial concentrations. In this study a new method for ventilation effectiveness application in ventilation design for airborne transmission was developed and tested with tracer gas measurements in 22 rooms. Contrary to existing ventilation effectiveness values measured with distributed source, the developed method uses a couple of point source locations corresponding to an infector to quantify infection risk for each occupant. Novelty of the method is new ventilation effectiveness indicator that makes it possible to describe the effect of spatial variation of concentration and risk with single parameter. Quanta were used as input data to calculate the ventilation rate supplied by air distribution system corresponding to a specified risk level, but the differences between studied cases do not significantly depend on the quanta values. Application of the method to measured rooms showed that simple ventilation effectiveness calculation from average concentration at the breathing height, not requiring quanta data, provided lower ventilation effectiveness and higher ventilation rate in all cases. In many cases the difference in required ventilation rates was only a few percent, but in some large spaces it exceeded 10% with maximum of 39% in large open plan office with high concentration differences. Measured ventilation effectiveness values ranging from 0.5 to 1.4 indicate a substantial improvement potential in many cases.

CFD Analysis of Indoor Ventilation for Airborne Virus Infection

CFD Analysis of Indoor Ventilation for Airborne Virus Infection Indoor airflow patterns and air residence times significantly influence the spread of airborne infectious viruses, such as COVID-19. These factors can be quantified using computational fluid dynamics (CFD). In this study, CFD was utilized to assess the indoor airflow patterns and calculate air residence times in a typical restroom with high personnel flow and low ventilation efficiency. The results identified regions with high air residence times, indicating potential risk areas for airborne virus retention. Furthermore, the effects of different ventilation strategies on these high-risk areas were analyzed. Despite meeting air change standards, certain regions were found to potentially pose a higher risk due to prolonged air residence times. Based on these findings, recommendations for improving ventilation systems to reduce the risk of airborne virus infection were proposed. This study highlights the necessity of a more nuanced approach to indoor air assessment than simply calculating air changes per hour. It was concluded that (1) different ventilation strategies can greatly affect the air residence time in the room and (2) the variance of air residence time in the air circulation area are large in some locations, even with simple ventilation adjustments.

Novel design of inspiratory flow generation and gas mixing for critical care ventilators suitable for rapid production and mass casualty incidents

Scarcity of medical resources inspired many teams worldwide to design ventilators utilizing different approaches during the recent COVID-19 pandemic. Although it can be relatively easy to design a simple ventilator in a laboratory, a large scale production of reliable emergency ventilators which meet international standards for critical care ventilators is challenging and time consuming. The aim of this study is to propose a novel and easily manufacturable principle of gas mixing and inspiratory flow generation for mechanical lung ventilators. Two fast ON/OFF valves, one for air and one for oxygen, are used to control the inspiratory flow generation using pulse width modulation. Short gas flow pulses are smoothed by low-pass acoustic filters and do not propagate further into the patient circuit. At the same time, the appropriate pulse width modulation of both ON/OFF valves controls the oxygen fraction in the generated gas mixture. Tests focused on the accuracy of the delivered oxygen fractions and tidal volumes have proved compliance with the international standards for critical care ventilators. The concept of a simple construction using two fast ON/OFF valves may be used for designing mechanical lung ventilators and thus suitable for their rapid production during pandemics.

The Modified Medial Maxillectomy as a Radical or Extended,-yet Still Functional,-Technique in Sinus Surgery.

Endoscopic sinus surgery with a middle meatal antrostomy is a common intervention in the treatment algorithm for maxillary sinus pathologies. However, this procedure has its origins in a time when simple ventilation of the sinus cavity was the primary (and only often) goal of surgery. In some patients, persistent mucociliary dysfunction occurs despite ventilatory surgery. Although the endoscopic modified medial maxillectomy (MMM) was originally described for tumour surgery, it provides a radical yet still functional option to overcome chronic sinus dysfunction. The goal of this study was to describe the functional status of a post-MMM sinus cavity. A consecutive series of patients who underwent at least a unilateral MMM by three tertiary rhinologists were retrospectively reviewed. Prospectively collected data included patient demographics (including age, gender, smoking status and comorbidities), disease-specific factors, microbiology, and preoperative patient-reported symptoms based on the 22-item Sinonasal Outcome Test-22 (SNOT-22) and radiology. The primary outcome of the study was the presence of sinus dysfunction, defined by mucostasis or pooling on endoscopic examination at the last follow-up. Secondary outcomes included the need for revision surgery as a result of sinus dysfunction and the improvement in SNOT-22 score. A total of 551 medial maxillectomies (47.0% female, 52.9 ± 16.8 years) were performed. Very few patients experienced post-operative sustained mucostasis following MMM (10.2%) and even fewer required revision surgery (5.0%). Chronic obstructive pulmonary disease (odds ratio (OR) = 6.82, P < 0.002.) and asthma (OR = 2.48, P = 0.03) were associated with mucostasis. Patients who underwent an MMM experienced a notable postoperative improvement in SNOT-22 score (45.9 ± 23.7 (pre-op) vs. 23.6 ± 19.4 (post-op); paired t-test, P < 0.0001). The MMM, whether performed for access to pathology or with the intent to avoid mucous 'sumping' with the sinus, can provide a long-term functional maxillary sinus cavity with minimal morbidity.

Linear regression model and least square method for experimental identification of AMBU bag in simple ventilator

PurposeIn the COVID-19 outbreak periods, people's life has been deranged, leading to disrupt the world. Firstly, the number of deaths is growing and has the potential to surpass the highest level at any time. Secondly, the pandemic broke many countries' fortified lines of epidemic prevention and gave people a more honest view of its seriousness. Finally, the pandemic has an impact on life, and the economy led to a shortage in medical, including a lack of clinicians, facilities and medical equipment. One of those, a simple ventilator is a necessary piece of medical equipment since it might be useful for a COVID-19 patient's treatment. In some cases, the COVID-19 patients require to be treated by modern ventilators to reduce lung damage. Therefore, the addition of simple ventilators is a necessity to relieve high work pressure on medical bureaucracies. Some low-income countries aim to build a simple ventilator for primary care and palliative care using locally accessible and low-cost components. One of the simple principles for producing airflow is to squeeze an artificial manual breathing unit (AMBU) iterative with grippers, which imitates the motion of human fingers. Unfortunately, the squeezing angle of grippers is not proportional to the exhaust air volume from the AMBU bag. This paper aims to model the AMBU bag by a mathematical equation that enables to implement on a simple controller to operate a bag-valve-mask (BVM) ventilator with high accuracy performance.Design/methodology/approachThis paper provides a curvature function to estimate the air volume exhausting from the AMBU bag. Since the determination of the curvature function is sophisticated, the coefficients of the curvature function are approximated by a quadratic function through the experimental identification method. To obtain the high accuracy performance, a linear regression model and a least square method are employed to investigate the characteristic of the BVM ventilator's grippers angle with respect to the airflow volume produced by the AMBU bag.FindingsThis paper investigates the correlation between the exhausting airflow of the AMBU bag and the grippers angle of the BVM ventilator.Originality/valueThe experimental results validated that the regression model of the characteristic of the exhausting airflow of the AMBU bag with respect to the grippers' angle has been fitted with a coefficient over 98% within the range of 350–750 ml.

Measurement and Control of Surgical Smoke to Enhance Surgical Team Safety.

Amid the coronavirus disease 2019 era, concern about the safety of surgical teams related to surgical smoke (SS) is rising. As simple ventilation improvement methods (SVIMs), we replaced 4 of the 8 supply diffusers with a direction-adjustable louver-type, closed 2 of the 4 exhaust grills, and strengthened the sealing of the doorway. Dynamic changes in the concentration of particulate matter (PM) with sizes of < 1.0 μm (PM1.0) were measured using low-cost PM meters (LCPMs) at eight locations in the operating room (OR). SS concentration up to 4 minutes at the location of the surgeon, first assistant, and scrub nurse before and after SVIMs application decreased from 65.4, 38.2, 35.7 µg/m3 to 9.5, 0.1 and 0.7 µg/m3 respectively. A similar decrease was observed in the other 5 locations. SVIMs could effectively control SS and the LCPM was also effective in measuring SS in the OR or other spaces of the hospital.

A Simple Ventilator Designed To Be Used in Shortage Crises: Construction and Verification Testing

BackgroundThe COVID-19 pandemic has demonstrated the possibility of severe ventilator shortages in the near future.ObjectiveWe aimed to develop an acute shortage ventilator.MethodsThe ventilator was designed to mechanically compress a self-inflating bag resuscitator, using a modified ventilator patient circuit, which is controlled by a microcontroller and an optional laptop. It was designed to operate in both volume-controlled mode and pressure-controlled assist modes. We tested the ventilator in 4 modes using an artificial lung while measuring the volume, flow, and pressure delivered over time by the ventilator.ResultsThe ventilator was successful in reaching the desired tidal volume and respiratory rates specified in national emergency use resuscitator system guidelines. The ventilator responded to simulated spontaneous breathing.ConclusionsThe key design goals were achieved. We developed a simple device with high performance for short-term use, made primarily from common hospital parts and generally available nonmedical components to avoid any compatibility or safety issues with the patient, and at low cost, with a unit cost per ventilator is less than $400 US excluding the patient circuit parts, that can be easily manufactured.

COVID-19 Transmission during Transportation of 1st to 12th Grade Students: Experience of an Independent School in Virginia.

BackgroundIn‐school transmission of COVID‐19 among K‐12 students is low when mitigation layers are used, but the risk of acquiring COVID‐19 during school bus transportation is not well defined. Given the operational limitations of many school districts, more data is needed to determine what mitigation is required to keep COVID‐19 transmission low during bus transport.MethodsAn independent school in Virginia monitored 1154 students in grades 1 to 12 with asymptomatic PCR testing every 2 weeks from August 24, 2020 to March 19, 2021, during the highest community transmission. Fifteen buses served 462 students while operating at near capacity of 2 students in every seat, using a physical distancing minimum of 2.5 ft, universal masking, and simple ventilation techniques.ResultsA total of 39 individuals were present on buses during their COVID‐19 infectious period, which resulted in the quarantine of 52 students. Universal testing and contact tracing revealed no transmission linked to bus transportation.ConclusionsThis study demonstrates a model for the safe operation of school buses while near capacity. COVID‐19 transmission can be low during student transport when employing mitigation including simple ventilation, and universal masking, at minimal physical distances and during the highest community transmission.

Influence of gas outburst dynamic flow on mine ventilation system

This study was conducted to analyze the influence of outburst power from coal and gas on mine ventilation systems in order to avoid damage from secondary disasters to mine ventilation systems. Through the outburst dynamic experiment of a simple ventilation network system, the unsteady movement characteristics of mine air flow under the combined action of gas outburst source flow and fan ventilation are studied. In this study, the “11.8” coal and gas outburst accident that occurred in the Qunli Coal Mine was simulated numerically. The TF1M simulation program was used to analyze the entire process of the diffuse flow of the countercurrent and outburst gas in the mine ventilation system as well as the dynamic change process of the natural wind pressure in each stage. The results indicate that the power of the outburst source causes the ventilation system to run against the current, the gas in the air intake system of the mine exceeds the limit, and the airflow disturbance of the mine ventilation system is influenced by natural gas pressure and fan pressure. The air pressure of the fan cannot change the rate of air flow but can reduce the time of air flow disorder and promote the gas discharge in the ventilation system. In a word, the research achievements do have important theoretical and practical significance for disaster prevention and aid in outburst mine as well as effectively preventing the occurrence of secondary disasters.

Patient-ventilator dyssynchrony in the intensive care unit: A practical approach to diagnosis and management.

Patient-ventilator dyssynchrony or asynchrony occurs when, for any parameter of respiration, discordance exists between the patient's spontaneous effort and the ventilator's provided support. If not recognised, it may promote oversedation, prolong the duration of mechanical ventilation, create risk for lung injury, and generally confuse the clinical picture. Seven forms of dyssynchrony are common: (a) ineffective triggering; (b) autotriggering; (c) inadequate flow; (d) too much flow; (e) premature cycling; (f) delayed cycling; and (g) peak pressure apnoea. 'Reverse triggering' also occurs and may mimic premature cycling. Correct diagnosis of these phenomena often permits management by simple ventilator optimisation rather than by less desirable measures.

Concept and Prelimnary Design of an Economical Bag Valve Mask Compressor as a Prototype for Simple Ventilator During COVID-19.

The pandemic of COVID 19 has taken a massive toll of lives since its outbreak. Throughout the world with a large number of people being affected by covid 19, the need for the ventilators has risen. However, there is disproportionate ratio of demand versus supply of ventilators due to the menace caused by Covid 19 which has become unmanageable. This paper describes the design of the low cost portable mechanical bag valve mask compressor which could serve as a preliminary ventilator for the patients needing ventilator support in COVID 19. This prototype ventilator delivers breaths by compressing a conventional bag-valve mask (BVM) with a motor, eliminating the need for a human operator for the BVM. It is driven by a wind shield wiper electric motor powered by a 12 V battery. Additionally it can be used to deliver oxygen through either Laryngeal mask or compact face masks or nasopharyngeal airways where intubation is awaited in early breathlessness. Future additions for our prototype ventilator will include a controllable inspiration to expiration time ratio, a pressure relief valve, PEEP capabilities and an LCD screen. With a prototyping cost of only $150, the concept of BVM compressor is a low-cost, low-power portable ventilator technology that will provide essential ventilator features at a fraction of the cost of existing technology.

Single-channel blowing-in longitudinal ventilation method and its application in the road tunnel

The longitudinal ventilation method is widely used in extra-long tunnels because of its simple ventilation mode and lower construction and operation costs. This paper originally proposes a new longitudinal ventilation method, the single-channel blowing-in longitudinal method. Only one ventilation channel is set between uphill line and downhill line of main tunnel, and relatively fresh air near the entrance of the downhill line is sent to the section close to the uphill line exit through the ventilation channel. The authors deduced the ventilation theory, design method and applicable conditions in detail, analyzing six cases to reveal the variation regulation of optimal location of single-channel xfit, one-year ventilation energy consumption Pone, total ventilation energy consumption Ptotal, and applicable scope of the tunnel length Lmax. The results suggest the following. (1) The optimal location of single-channel xfit enable the total ventilation energy consumption in serving period Ptotal to be the minimal, but usually it cannot let one-year energy consumption Pone reach the minimum. (2) The single-channel system makes full use of the surplus fresh air and the piston effect of traffic wind in the tunnel, showing a better energy-efficient property from a long-term perspective (3) For the whole serving period, xfit and Ptotal is relatively fixed when the traffic volume changes linearly. Meanwhile, this method has been successfully applied to China Mingtang Mountain Tunnel, and the relevant engineering application experience would be helpful for the similar projects.

Simple Ventilators for Emergency Use Based on Bag-Valve Pressing Systems: Lessons Learned and Future Steps

As part of a plethora of global efforts to minimize the negative effects of the SARS-CoV2 (COVID-19) pandemic, we developed two different mechanisms that, after further development, could potentially be of use in the future in order to increase the capacity of ventilators with low-cost devices based on single-use-bag-valve mask systems. We describe the concept behind the devices and report a characterization of them. Finally, we make a description of the solved and unsolved challenges and propose a series of measures in order to better cope with future contingencies.

A Gas-Powered, Patient-Responsive Automatic Resuscitator for Use in Acute Respiratory Failure: A Bench and Experimental Study.

During the COVID-19 pandemic, a need for innovative, inexpensive, and simple ventilator devices for mass use has emerged. The Oxylator (CPR Medical Devices, Markham, Ontario, Canada) is an FDA-approved, fist-size, portable ventilation device developed for out-of-hospital emergency ventilation. It has not been tested in conditions of severe lung injury or with added PEEP. We aimed to assess the performance and reliability of the device in simulated and experimental conditions of severe lung injury, and to derive monitoring methods to allow the delivery of safe, individualized ventilation during situations of surge. We bench-tested the functioning of the device with an added PEEP valve extensively, mimicking adult patients with various respiratory mechanics during controlled ventilation, spontaneous breathing, and prolonged unstable conditions where mechanics or breathing effort was changed at every breath. The device was further tested on a porcine model (4 animals) after inducing lung injury, and these results were compared with conventional ventilation modes. The device was stable and predictable, delivering a constant flow (30 L/min) and cycling automatically at the inspiratory pressure set (minimum of 20 cm H2O) above auto-PEEP. Changes in respiratory mechanics manifested as changes in respiratory timing, allowing prediction of tidal volumes from breathing frequency. Simulating lung injury resulted in relatively low tidal volumes (330 mL with compliance of 20 mL/cm H2O). In the porcine model, arterial oxygenation, CO2, and pH were comparable to conventional modes of ventilation. The Oxylator is a simple device that delivered stable ventilation with tidal volumes within a clinically acceptable range in bench and porcine lung models with low compliance. External monitoring of respiratory timing is advisable, allowing tidal volume estimation and recognition of changes in respiratory mechanics. The device can be an efficient, low-cost, and practical rescue solution for providing short-term ventilatory support as a temporary bridge, but it requires a caregiver at the bedside.

Effect of new simple breathing apparatus on oxygen therapy in patients with severe and critical coronavirus disease 2019

To make a new simple respirator and observe the oxygen therapy effect of the respirator on patients with severe and critical coronavirus disease 2019 (COVID-19). Based on the infectivity and hospital requirements of COVID-19, a new simple respirator was designed by the medical staff of the Department of Anesthesiology of the Second Affiliated Hospital of Nanchang University, which was applied on the 22 patients with severe and critical COVID-19 who needed oxygen therapy admitted to the Cancer Center of Tongji Medical College of Huazhong University of Science and Technology from February 15th to March 15th in 2020. The new simple respirator contained two National Utility Model Patents (a respirator: ZL 2015 2 0410623.6, a fluid switch and oxygen suction device: ZL 2017 2 0873509.6), which was mainly composed of anesthesia mask and filter, L-shaped connecting tube, soft breathing bladder, connecting tube and elastic fixing belt. When in use, the anesthesia mask was fixed to the patient's mouth and nose with elastic straps, the connecting tube was inserted into the oxygen meter interface, the oxygen flow was adjusted to 6-10 L/min, and the L-shaped connecting tube was opened immediately after the soft breathing bag was full. The carbon dioxide and excess oxygen in the body was discharged from exhaust port. The oxygen flow was lowered to 2-3 L/min, the patient's respiratory rate (RR) was observed through the soft breathing bag fluctuations, and the oxygen flow was adjusted at any time. The changes of pulse oxygen saturation (SpO2), RR and heart rate (HR) before and after application of new simple respirator were observed, and the blood gas test results of part of the patients were collected. Twenty-two patients with severe and critical COVID-19 had significantly higher SpO2 at 10 minutes after application of the new simple ventilator than before application (0.994±0.007 vs. 0.952±0.017, P < 0.01), and RR was significantly lower than that before application (times/min: 27.59±3.63 vs. 29.64±3.81, P < 0.01); after 1 day of application, each index was further improved. All 13 patients who received blood gas analysis indicated no carbon dioxide accumulation. The new simple respirator can significantly improve the oxygen therapy effect of patients with severe and critical COVID-19. At the same time, 2019 novel coronavirus (2019-nCoV) can be filtered through the filter to reduce the formation of aerosol and protect the medical staff and patients.

Control of light gas releases in ventilated tunnels

The release of buoyant harmful gases within enclosed spaces, such as tunnels and corridors, may engender specific health, industrial and transportation risks. For safety, a simple ventilation strategy for these spaces is to impose a flow along the tunnel, whose velocity is defined as ‘critical’, that confines the front of harmful buoyant gases immediately downstream of the source of emission. Determining the critical velocity as a function of the geometrical and dynamical conditions at the source is a fundamental fluid mechanics problem which has yet to be elucidated; this problem concerns the dynamics of non-Boussinesq releases relating to large differences between the densities of the buoyant and the ambient fluids. We have investigated this problem theoretically, by means of a simplified model of a top-hat plume in a cross-flow, and in complementary experiments by means of tests in a reduced-scale ventilated tunnel, examining releases from circular sources. Experimental results reveal: (i) the existence of two flow regimes depending on the plume Richardson number at the source $\unicode[STIX]{x1D6E4}_{i}$, one for momentum-dominated releases, $\unicode[STIX]{x1D6E4}_{i}\ll 1$, and a second for buoyancy-dominated releases, $\unicode[STIX]{x1D6E4}_{i}\gg 1$, with a smooth transition between the two; and (ii) the presence of relevant non-Boussinesq effects only for momentum-dominated releases. All these features can be conveniently predicted by the plume-based model, whose validity is, strictly speaking, limited to releases issuing from ‘small’ sources in ‘weak’ ventilation flows. Analytical solutions of the model are generally in good agreement with the experimental data, even for values of the governing parameters that are beyond the range of validity for the model. The solutions aid to clarify the effect of the source radius, and reveal interesting behaviours in the limits $\unicode[STIX]{x1D6E4}_{i}\rightarrow 0$ and $\unicode[STIX]{x1D6E4}_{i}\rightarrow \infty$. These findings support the adoption of simplified models to simulate light gas releases in confined ventilated spaces.

Application of simple respirator combined with respiratory function training in airway management of patients with cerebral apoplexy after tracheotomy

Objective To observe the application effect of simple respirator combined with respiratory function training in airway management of patients with cerebral apoplexy after tracheotomy. Methods Totally 93 patients with stroke tracheotomy from May 2017 to April 2018 were randomly divided into the intervention group (45 cases) and thecontrol group (48 cases). The control group was treated with routine nursing after tracheotomy, and the intervention group was trained by simple ventilator combined with breathing function on the basis of the control group.The incidence of pulmonary infection during the tracheal cannula in two groups was observed, the total retention time of the trachea cannula, the incidence of blood oxygen saturation < 94% from 24 h to 48 h, the number of cases of catheterization, and the incidence of pulmonary infection were observed. Results In the intervention group and the control group, the pulmonary infection rate was 6.67% (3/45) in the intervention group, which was lower than the control group. The lung infection rate was 20.83% (10/48). The significance of learning (χ2=3.89, P=0.04); the total indwelling time of tracheal intubation in the intervention group (25.73±6.51) d was shorter than that in the control group (28.28±4.79) d, the difference was statistically significant (t=-2.16, P=0.03); within the intervention group and the control group, within 24-48 hours, the oxygen saturation of the intervention group was <0.94 (6.6% (3/45), and the incidence of pulmonary infection was 2.22% (1/45). The incidence rate of re-intubation was 0 (0/45), which was lower than 22.92% (11/48), 14.58% (7/48), and 10.42% (5/48) of the control group. The difference was statistically significant (χ2= 4.80, 4.51, 4.75, P= 0.03, 0.03, 0.03). Conclusions The simple breathing apparatus combined with respiratory function training can effectively improve the respiratory function of the patients, reduce the occurrence of pulmonary infection and re tube after the tracheal tubing and tubing, shorten the retention time of the trachea cannula, reduce the patient's pain and economic burden, and reduce the risk of nursing. It is scientific and effective. Airway management measures should be widely applied in clinical practice. Key words: Stroke; Tracheotomy; Simple respirator; Respiratory function training; Nursing care

IMPROVING INDOOR AIR QUALITY OF NATURALLY VENTILATED CLASSROOMS IN THE NORTHEAST OF PORTUGAL

This article addresses CO2 dynamics in school classrooms and analyses the improvement of ventilation and indoor air quality resulting from the simple window-opening ventilation strategies. CO2, temperature and relative humidity were measured in four different naturally ventilated classrooms of a Northeastern Portuguese education institution for a wide range of environmental conditions. Indoor CO2 levels were also simulated with a numerical model to help manage the indoor air quality of these spaces through scenario analysis. The results stressed that the occupants were potentially exposed to uncomfortable and unhealthy indoor air quality conditions, since ventilation occurs primarily through infiltration. Under low ventilation conditions, CO2 concentrations easily exceeded the standard of 1250 ppm, even for occupation rates lower than 50%. To provide healthy indoor air to the occupants, acceptable and affordable ventilation rates can be assured by opening at least a small window for a few minutes over the typical 60 minute class period or during class breaks. For occupation rates close to the nominal capacity of classrooms, longer periods and larger opening areas are required to reduce the discomfort and health risks from potential exposure to indoor air pollutants.

Effects of Ventilation Improvement on Measured and Perceived Indoor Air Quality in a School Building with a Hybrid Ventilation System.

Ventilation system design and operation may significantly affect indoor air quality (IAQ). The aims of this case study were to investigate the functionality of a supply air fan-assisted hybrid ventilation system in a newly built school building with reported IAQ problems and to determine the effects of ventilation improvement on measured and perceived IAQ. The ventilation system function was researched simultaneously with IAQ measurements, with an analysis of total volatile organic compounds (TVOC), single volatile organic compounds (VOCs), and indoor mycobiota, and with questionnaires about perceived IAQ. At the baseline, an operational error of the ventilation system was found, which prevented the air from coming into the classrooms, except for short periods of high carbon dioxide (CO2) concentrations. After the ventilation operation was improved, a significant change in indoor mycobiota was found; the dominant, opportunistic human pathogenic species Trichoderma citrinoviride found in settled dust in the classroom before the improvement was no longer detected. In addition, the concentrations of CO2, TVOC, and some single VOCs, especially toluene and decamethylcyclopentasiloxane, decreased. The analysis of the questionnaire results indicated that the perceptions of unpleasant odors and stuffy air decreased, although a statistically significant improvement in perceived IAQ was not observed. The results provided evidence that the properly controlled hybrid ventilation system operating in mechanical supply mode provided adequate ventilation and was effective in decreasing the concentrations of some indoor-generated pollutants. With simple ventilation adjustments, microbiological exposure from building structures might be prevented.

Effect of lateral position ventilation combined with vibration sputum drainage on patients with acute respiratory distress syndrome: a prospective randomized controlled trial

To investigate the curative effect of lateral position ventilation combined with vibration sputum drainage on the patients with acute respiratory distress syndrome (ARDS). A prospective randomized controlled trial was conducted. The patients with ARDS undergoing mechanical ventilation (MV) admitted to intensive care unit (ICU) of Linyi Central Hospital from January 2013 to June 2017 were enrolled, and they were divided into simple ventilation group and combined treatment group according to random number table. The patients in both groups received etiological treatment, protective ventilation strategy, sensitive antibiotics for anti-infection, and calefacient and humidifying treatment. The patients in the simple ventilation group received bilateral discontinuous alternative lateral position ventilation [pressure controlled ventilation (PCV), tidal volume (VT) ≤ 6 mL/kg, the inhaled oxygen concentration (FiO2) and positive end expiratory pressure (PEEP) was adjusted to maintain the airway plateau pressure (Pplat) ≤ 30 cmH2O (1 cmH2O = 0.098 kPa)], and those in the combined treatment group received lateral position ventilation combined with vibration sputum drainage, twice a day, 15 minutes each time. The parameters of respiratory function and inflammation as well as excretion of sputum before and after treatment were compared between the two groups, and the complication and prognosis were recorded. A total of 200 patients with ARDS were included, 4 patients were excluded because of severe pneumothorax, massive hemorrhage of the digestive tract, or elevated intracranial pressure, so 196 patients were finally enrolled in the analysis. There were 98 patients in the simple ventilation group and the combined treatment group, respectively. There were no significant differences in parameters of respiratory function and inflammation as well as excretion of sputum before treatment between the two groups. After treatment, the above parameters in both groups were improved, and the effect of combined treatment was more significant. Compared with the simple ventilation group, white blood cell count (WBC), procalcitonin (PCT), C-reactive protein (CRP) at 24 hours of treatment in the combined treatment group were significantly decreased [WBC (×109/L): 9.1±1.6 vs. 11.8±3.6, PCT (μg/L): 14.5±2.4 vs. 22.7±3.2, CRP (mg/L): 32.2±6.3 vs. 67.2±7.2, all P < 0.01], the quantity of sputum excretion was significantly increased (mL: 49.3±12.5 vs. 36.8±11.8, P < 0.01); 72 hours after treatment, the oxygenation index (PaO2/FiO2) in the combined treatment group was significantly increased [mmHg (1 mmHg = 0.133 kPa): 278±28 vs. 238±39, P < 0.01], and PEEP, FiO2, airway resistance (Raw) were significantly lowered [PEEP (cmH2O): 5±2 vs. 7±3, FiO2: 0.40±0.11 vs. 0.49±0.12, Raw (cmH2O): 12.8±0.7 vs. 16.2±0.8, all P < 0.01]. There was no significant difference in static lung compliance (Cst) or Pplat between the two groups. Compared with the simple ventilation group, the duration of MV (days: 5.5±3.0 vs. 8.6±2.1), the length of ICU stay (days: 7.5±5.4 vs. 11.3±4.6) and the extraction time of artificial airway (days: 6.6±2.8 vs. 9.4±3.3) in the combined treatment group were significantly shortened (all P < 0.01). However, there was no significant difference in the 28-day mortality rate [4.1% (4/98) vs. 3.1% (3/98)], the rate of tracheotomy [2.0% (2/98) vs. 3.1% (3/98)] or the incidence of I-II skin pressure sore [1.0% (1/98) vs. 2.0% (2/98)] between simple ventilation group and the combined treatment group (all P > 0.05). No artificial airway disappearance, pneumothorax, grade III or IV pressure sore was found in the two groups. Compared with lateral position ventilation alone, the treatment of combined with vibration sputum drainage is more effective for improving the respiratory function of patients with ARDS, reducing infection action, shortening the duration of MV and the length of ICU stay, and improve the recovery, promote the rehabitation of patients.