Spatial distribution of bioaerosols and evaluation of four ventilation method on controlling their diffusion in a typical enhanced biosafety level 2 laboratory.

Biosafety laboratories are critical in many fields. However, experimenters associated the infection risk from biological aerosols. In this study, by conducting experiments on the release and collection of bioaerosols within a typical BSL-2 + laboratory, the spatial distribution of bioaerosols was tracked. Numerical calculations were employed to obtain and visualize the airflow patterns and aerosol dispersion paths of four ventilation methods. The results indicated that equipment and tables led to uneven airflow distribution within the laboratory. The comparison results of the four evaluation indicators showed that the air age distribution of UU (Upward supply and upward return) mode and CD (Cross-supply and downward return) mode was superior, with air change efficiency values of 0.595 and 0.603, respectively. Additionally, the contaminant removal index of CD mode was 1.48, significantly higher than the other ventilation methods. The statistical results of the contaminant dispersion index also indicated that CD mode was most conducive to diluting aerosols in the spatial environment. The LD (lateral supply and downward return) mode may lead to airflow short-circuiting. The UD (upward supply and downward return) mode can provide balanced protection for laboratory. Overall, CD mode performed the best among the four ventilation methods, followed by UU mode.

Theoretical model for calculating and adjusting radon activity concentration in ventilation networks of uranium mines considering pressure drop effect.

The radiation dose of workers in underground uranium mines mainly comes from radon and radon progeny. To ensure a healthy and safe work environment, it is necessary and urgent to optimize the design of ventilation systems. As such, based on the simplified radon diffusion-advection migration model of the rocks, this paper proposes 1) two methods for determining the radon exhalation rate modified by pressure drop, 2) three methods for calculating radon activity concentration of single-branch, and 3) the novel adjustment algorithm and solving procedures for calculating and adjusting the radon activity concentration in ventilation networks by modifying the radon exhalation rate, demonstrated on a specific ventilation network in a simulated underground uranium mine with calculation and analysis via MATLAB. The results show that 1) the radon exhalation rate of different branches can be modified by their pressure drop, and 2) the proposed method can be used to reveal the influences of different ventilation methods and fan pressures on the radon activity concentration in the ventilation network and the radon release rate to the atmosphere.

Comparison of Pressure Control Ventilation and Palpation Methods to Protect the Endotracheal Tube Cuff During Tracheotomy: A Manikin Simulation Study.

Objective This study aims to evaluate and compare the suitability and safety of palpation and pressure control ventilation (PCV) methods for the accurate positioning of an endotracheal tube (ETT) cuff. Methods We conducted a pilot simulation randomized crossover study using a medical manikin. Twenty junior resident physicians who had completed anesthesiology training participated in the study. Airway management was performed using a modified manikin designed to simulate palpation and PCV methods. Participants performed both methods in a randomized order. The primary outcome was the number of successful ETT placements. The secondary outcomes were procedure duration and the perceived difficulty of each procedure. Results Five successful procedures were observed in the palpation method group (PALG), while 19 were observed in the PCV method group (PCVG). The duration of the trial was 98 s (standard deviation [SD], 41) in the PALG and 93 s (SD, 49) in the PCVG. The visual analog scale score for difficulty encountered during the trial was 30 (SD, 21) in the PALG and 69 (SD, 19) in the PCVG. Conclusions Our findings suggest that the PCV method had a higher success rate than the palpation method. Thus, the PCV method may be more suitable for inexperienced physicians to perform the procedure with greater confidence.

Critical Case of a Preterm Infant Infected With Respiratory Syncytial Virus Managed in the Pediatric Intensive Care Unit: A Case Report.

We describe a critical case of a respiratory syncytial virus (RSV) infection in a preterm infant resulting in respiratory failure with advanced respiratory interventions and discharge from our hospital without the requirement for home oxygen therapy or tube feeding. The infant, delivered at 35 weeks gestation due to a premature rupture of the membranes with a birth weight of 2 kg, initially demonstrated a stable postnatal course. The baby required no resuscitation, with Apgar scores of 8 and 9 at one and five minutes, respectively. The infant was discharged in good condition after four days of hospitalization. This report presents a critical case of RSV infection in a preterm infant requiring intensive care. The infant, born at 35 weeks gestation, initially appeared healthy but developed severe symptoms at 22 days old. The emergency evaluation revealed significant respiratory distress and confirmed RSV pneumonia. Following extensive interventions, including mechanical ventilation to manage severe symptoms, along with complications such as pneumothorax and a cardiac arrest episode, the infant exhibited a positive response to subsequent treatments. The infant responded positively to high-frequency oscillatory ventilation and inhaled nitric oxide. Gradual weaning from advanced ventilation led to successful extubation, followed by recovery with high-flow nasal cannula therapy. The case highlights the challenges of managing severe RSV infections in preterm infants and the efficacy of intensive care interventions in facilitating the infant's remarkable recovery and discharge.

Surgical mask-to-mouth ventilation as an alternative ventilation technique during CPR: A crossover randomized controlled trial.

INTRODUCTION: Chest compression with rescue breathing improves outcomes in cardiac arrest. However, the efficacy of rescue breathing through surgical masks has not been investigated. OBJECTIVE: We aimed to compare the tidal volume generated by mouth-to-mouth ventilation (MMV) with that generated by surgical mask-to-mouth ventilation (SMV), mouth-to-surgical mask ventilation (MSV), and surgical mask-to-surgical mask ventilation (SSV) in a manikin. METHODS: A crossover randomized controlled trial was conducted in 42 medical personnel volunteers randomly assigned to perform four ventilation techniques: MMV (no protective equipment), SMV (participant wearing a mask), MSV (manikin wearing a mask), and SSV, (both participant and manikin wearing a mask). The average tidal volume and the proportion of adequate ventilation, evaluated using a manikin, were compared across different ventilation methods. RESULTS: The average tidal volume of MMV (828 ± 278 ml) was significantly higher than those of the MSV (648 ± 250 ml, P < 0.001) and SSV (466 ± 301 ml, P < 0.001), but not SMV (744 ± 288 ml, P = 0.054). Adequate ventilation was achieved in 144/168 (85.7%) cases in the MMV group, a proportion significantly higher than in the SMV (77.4%, P = 0.02), MSV (66.7%, P < 0.001) and SSV (39.3%, P < 0.001) groups. The willingness to perform SMV was higher than that to perform MMV. CONCLUSIONS: MMV resulted in a superior average tidal volume when compared to both MSV and SSV. However, SMV achieved a comparable average tidal volume to MMV.

The metabolic cost of breathing in red-eared sliders: An attempt to resolve an old controversy.

Accurately measuring the metabolic cost of breathing in turtles has been a challenge with cost estimates varying greatly between different studies and/or methods used. To determine the source of discrepancy, we calculated costs using two methods in a single group of red-eared sliders (Trachemys scripta elegans). The unidirectional ventilation method yielded an estimate of 3.3ml O2/L air ventilated while the regression method (using hypoxia as a respiratory stimulus) produced an estimate of 0.8ml O2/L air ventilated when corrected for hypoxia-induced metabolic suppression. Cost differences may be in part due to the non-linear nature of the relationship between metabolic cost and ventilation. They are also likely due to the challenge of accurately estimating costs from irregular, episodic breathing pattern of turtles and the buffering capacity of their large lungs that lead to inconsistency in the amount of O2 extracted from each breath/breathing episode. Given the difficulty in obtaining consistent measures, the values reported here must be taken cautiously.

Effects of mechanical ventilation method on inflammatory factors and pulmonary surfactant associated protein A of bronchoalveolar lavage fluid in newborn piglets with acute lung injury / 中华实用儿科临床杂志

Objective To investigate the effects of 3 different ventilation methods,including conventional mechanical ventilation (CMV),high frequency oscillatory ventilation(HFOV) and partial liquid ventilation (PLV),on the changes of inflammatory factors and pulmonary surfactant associated protein A (SP-A) in bronchoalveolar lavage fluid (BALF) in newborn piglets with acute lung injury(ALI).Methods Twenty-four newborn piglets,no more than 3 days old,were enrolled.After ALI made with saline lavage(38 ℃,35 mL/kg),newborn piglets were randomly assigned to 4 groups:control group (n =6,no ventilation),CMV group(n =6),HFOV group(n =6),and PLV group(n =6).Piglets were sacrificed after being ventilated for 24 h.Tumor necrosis factor-α (TNF-α),interleukin-8 (IL-8),interleukin-1 (IL-1) and SP-A in BALF were measured quantitatively by using enzyme-linked immunosorbent assay.Results In 3 groups using different ventilation methods,the population mean of TNF-o,IL-8,IL-1 and SP-A were statistically different (all P =0.000).SP-A in PLV group and HFOV group were higher than that in CMV group (all P ＜ 0.05),while IL-8,IL-1 and TNF-α in PLV group were lower than those in CMV group (all P ＜ 0.05),IL-8 and TNF-α in PLV group were lower than those in HFOV group (all P ＜ 0.05),IL-8 and TNF-α in HFOV group were lower than those in CMV group (all P ＜ 0.05).Conclusions Pulmonary inflammatory reaction was different in 3 ventilation groups.Compared with CMV and HFOV,PLV attenuated inflammatory reaction,so it could increase the expression of SP-A and decrease the degradation of SP-A.

Characteristics of physical blocking on co-occupant's exposure to respiratory droplet residuals.

Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome (SARS) and H1N1 pandemic. Non-pharmaceutical approaches, including ventilation system and personal protection, are believed to have certain positive effects on the reduction of co-occupant's inhalation. This work then aims to numerically study the performances of mouth covering on co-occupant's exposure under mixing ventilation (MV), under-floor air distribution (UFAD) and displacement ventilation (DV) system, using drift-flux model. Desk partition, as one generally employed arrangement in plan office, is also investigated under MV. The dispersion of 1, 5 and 10 µm droplet residuals are numerically calculated and CO2 is used to represent tracer gas. The results show that using mouth covering by the infected person can reduce the co-occupant's inhalation greatly by interrupting direct spread of the expelled droplets, and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person. The researches under MV show that the two interventions, mouth covering and desk partition, achieve almost the same inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.