Respiratory Mechanics, Respiratory Muscle Strength, Control of Ventilation and Gas Exchange in Patients with Autoimmune Liver Disease

Objectives: To assess respiratory elastance and resistive properties in patients with autoimmune liver disorders using the passive relaxation expiration technique and compare findings to a group of patients with non-autoimmune liver disease and control subjects. These findings were then related to control of ventilation and gas exchange. A secondary objective was to assess respiratory muscle strength and gas exchange and their relation to respiratory mechanics. Methods: Measurements included respiratory elastance and resistance using the passive relaxation method. Pulmonary function, gas exchange and control of ventilation were assessed using standard methods. Results: a) Compared to control subjects, Ers in patients with liver disease was on average 50% greater than in controls;b) mean respiratory resistance, expressed as the respiratory constants, K1 and K2 in the Rohrer relationship, Pao/V’ = K1 + K2V’, was not different from control resistance;c) mean maximal inspiratory and maximal expiratory pressures averaged 36% and 55% of their respective control values;d) inspiratory occlusion pressure in 0.1 sec (P0.1) was increased and negatively associated with FVC;and e) increases in P0.1, mean inspiratory flow (Vt/Ti) and presence of respiratory alkalosis confirmed the increase in ventilatory drive. Despite inspiratory muscle weakness in patients, P0.1/Pimax averaged 5-fold higher than in control subjects. Conclusions: Despite inspiratory muscle weakness and a V’E similar to that in normal subjects, central drive is increased in patients with chronic liver disease. The increase in ventilatory drive is related to smaller lung volumes and weakly associated with increase in respiratory elastance. Findings confirm that P0.1 is a reliable measure of central drive and is an approach that can be used in the evaluation of control of ventilation in patients with chronic liver disease.

A comparative study of dust control practices in Chinese and Australian longwall coal mines

Mine dust is one of the main hazards in underground longwall mines worldwide.In order to solve the mine dust problem,a significant number of studies have been carried out regarding longwall mine dust control,both in China and Australia.This paper presents a comparative study of dust control practices in Chinese and Australian longwall mines,with particular references to statutory limits,dust monitoring methods and dust management practices,followed by a brief discussion on the research status of longwall mine dust control in both countries.The study shows that water infusion,face ventilation controls,water sprays,and deep and wet cutting in longwall shearer operations are commonly practiced in almost all underground longwall mines and that both Chinese and Australian longwall mine dust control practices have their own advantages and disadvantages.It is concluded that there is a need for further development and innovative design of more effective dust mitigation products or systems despite the development of various dust control technologies.Based on the examinations and discussions,the authors have made some recommendations for further research and development in dust control in longwall mines.It is hoped that this comparative study will provide beneficial guidance for scholars and engineers who are engaging in longwall mine dust control research and practice.

The effect of different inflation volumes of laryngeal mask airway on efficacy of closed circuit controlled ventilation in pediatric cancer patients

Objective： The laryngeal mask airway （LMA） is an established way for airway control during spontaneous ventila- tion. Its ability to deliver positive pressure ventilation without leakage especially in low flow states is still controversy. The aim of this study is to test the possibility of using LMA in pediatric closed circuit controlled ventilation, and to find out the optimum cuff volume to perform closed system ventilation. Methods： Twenty children scheduled for elective surgeries were enrolled in a crossover study. Laryngeal mask airway was used. In stage I, the cuff was inflated with the maximum volume of air as rec- ommended by the manufacturers. Adjustment of volume of air inflated into the LMA cuff to the minimum volume to obtain the effective seal was done at stage II. The leak pressure, intracuff pressure and the leak volume were measured in both stages. Results： The cuff filling volume was significantly lower compared to the maximum cuff inflation volume in stage I. Leakage values showed significantly less values in stage II of the study with smaller cuff inflation volumes. The airway leakage pressure was significantly lower in stage fl in comparison to stage I. Cuff inflation pressure in stage I showed marked elevation which dropped significantly after adjustment of cuff volume in stage I1. Conclusion： Laryngeal mask airway is an effective tool to provide closed circuit controlled ventilation in pediatrics. Inflation of the cuff by the minimum volume of air needed to reach the just sealing pressure is suggested to minimize the leakage volume.

Effect of Rectus Plication during Abdominoplasty on the Mechanical Power and Airway Pressures: Comparison of Two Ventilatory Strategies

Background: Abdominoplasty is a commonly requested procedure for aesthetic improvement of the affected soft tissue layers of skin, fat, and muscle through the slightest incision feasible. The degree of plicature generates an increase in intraabdominal pressure that causes an increase in intrathoracic pressure. Pressure, volume, flow, and respiratory rate are components of a unique physical variable, the mechanical power (MP), and is an integrated variable linked to most factors related to postoperative pulmonary complications. Purpose: To assess the effect of rectus plication (RP) during abdominoplasty on lung pressures and the contribution to increasing the MP. Method: A open-label study was conducted at TJ Plast Advanced Center for Plastic Surgery in Tijuana, México, from September 2021 to May 2022. The study included forty-six female patients subjected to abdominoplasty or liposuction with abdominoplasty. After the induction of general anesthesia and neuromuscular blockade, they were allocated into two groups: Group 1 pressure control ventilation-volume guaranteed (PCV-VG) and Group 2 volume control ventilation (VCV). Respiratory pressures and MP were assessed before and after RP. Results: During VCV, patients had a greater increase in peak pressure (PIP) (P 0.000). Plateau pressure (Pplat) increased 1.78 ± 0.35 cmH2O in group 2 after RP (P = 0.001). MP had a greater increase in group 2 after RP (P 0.01). Conclusion: This prospective study showed that RP is related to an increase in PIP and Pplat and an increase in the MP better controlled with PCV-VG ventilation.

Experimental Investigation of Demand Controlled Ventilation Systems： A Suitable Alternative for Controlling Ventilation in Dwellings

Indoor CO2 concentration depends on the number of persons, their metabolic rates, other sources of indoor pollution, ventilation rate and ventilation efficiency. These factors are not considered by the Spanish technical building code since ventilation is set only by a fixed air change rate. This paper aims to explore the possibilities of DCVS （demand controlled ventilation systems） to ensure adequate and sustainable ventilation. It is based on a research project carried out by the University of the Basque Country （EHU-UPV） and Euskadi Public Housing and Soil Join-Stock Company （VISESA）： the living rooms of 90 dwellings were provided with DCVS, where CO2 sensors were used to dynamically control the ventilation rate. Tests were carried out using tracer gas techniques, with results showing the air age to be adequate at every point of the occupied zones and free of stagnant areas, therefore proving the system＇s effectiveness and rapid response, and its energy savings.

Determination of Effectiveness of Energy Management System in Buildings

Building Energy Management Systems(BEMS)are computer-based systems that aid in managing,controlling,and monitoring the building technical services and energy consumption by equipment used in the building.The effectiveness of BEMS is dependent upon numerous factors,among which the operational characteristics of the building and the BEMS control parameters also play an essential role.This research develops a user-driven simulation tool where users can input the building parameters and BEMS controls to determine the effectiveness of their BEMS.The simulation tool gives the user the flexibility to understand the potential energy savings by employing specific BEMS control and help in making intelligent decisions.The simulation is developed using Visual Basic Application(VBA)in Microsoft Excel,based on discrete-event Monte Carlo Simulation(MCS).The simulation works by initially calculating the energy required for space cooling and heating based on current building parameters input by the user in the model.Further,during the second simulation,the user selects all the BEMS controls and improved building envelope to determine the energy required for space cooling and heating during that case.The model compares the energy consumption from the first simulation and the second simulation.Then the simulation model will provide the rating of the effectiveness of BEMS on a continuous scale of 1 to 5(1 being poor effectiveness and 5 being excellent effectiveness of BEMS).This work is intended to facilitate building owner/energy managers to analyze the building energy performance concerning the efficacy of their energy management system.

Smoke movement in a tunnel of a running metro train on fire

Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.

Altered diaphragmatic contractile properties after high airway pressure controlled mechanical ventilation

Acute respiratory failure is the most frequent indication for the application of mechanical ventilation. As commonly used in clinical settings, lung protective strategies and recruitment manoeuvres are applications of higher than normal airway pressure to open the collapsed alveoli and prevent lung atelectasis caused by minimal vital ventilation. Under those conditions, we pay more attention to the lung injury and circulatory failure,

Real-time ventilation control based on a Bayesian estimation of occupancy

Demand-controlled ventilation(DCV)is commonly implemented to provide variable amounts of outdoor air according to an internal ventilation demand.The objective of the present study is to investigate the applicability and the performance of occupancy-based DCV schemes in comparison with time-based and CO_(2)-based DCV schemes.To do this,we apply the occupancy estimation method by the Bayes theorem to control the ventilation rate of an office building in real-time.We investigated six cases in total(two cases for each control scheme).Experiments were conducted in a small office room with controllable ventilation equipment and relevant sensors.The observed results indicated that the occupancy-based schemes relying on Bayes theorem could be applied successfully to perform continuous control of ventilation rates without causing recursive problems.Additionally,we discussed the time delays associated with the control procedure,including dispersion time,sensor-response time,and data processing time.Finally,we compared the performance of the proposed approach in six DCV cases in terms of a resultant indoor CO_(2) level and the total ventilation-air volume.We concluded that DCV control based on both occupancy and floor area provided the best conformity to the ASHRAE standard among the analyzed schemes.

Assessing ventilation control strategies in underground parking garages

Enclosed parking garages require mechanical ventilation fans to dilute concentrations of pollutants emitted from vehicles,which contributes to energy use and peak electricity demand.This study develops and applies a simulation framework combining multi-zone airflow and contaminant transport modeling,fan affinity laws,and realistic assumptions for vehicle traffic patterns and carbon monoxide(CO)emissions to improve our ability to predict the impacts of various ventilation control strategies on indoor air quality and fan energy use in parking garages.The simulation approach is validated using measured data from a parking garage case study and then applied to investigate fan energy use,peak power demand,and resulting CO concentrations for four different ventilation control strategies in a model underground parking garage under a variety of assumptions for model inputs.The four ventilation control strategies evaluated include one simplistic schedule(i.e.,Always-On)and three demand-based strategies in which fan speed is a function of CO concentrations in the spaces,including Linear-Demand Control Ventilation(DCV),Standardized Variable Flow(SVF),and a simple On-Off strategy.The estimated annual average fan energy consumption was consistently lowest with the Linear-DCV strategy,resulting in average(±standard deviation)energy savings across all modeled scenarios of 84.3%±0.4%,72.8%±3.6%,and 97.9%±0.1%compared to SVF,On-Off,and Always-On strategies,respectively.The utility of the framework described herein is that it can be used to model energy and indoor air quality impacts of other parking garage configurations and control scenarios.

Evaluation of the performance of demand control ventilation system for school buildings located in the hot climate of Saudi Arabia

The advantages of the demand control ventilation system(DCV)have been widely discussed in previous research studies.However,the literature has not addressed the benefits of DCV on controlling indoor CO_(2)concentration and minimizing cooling energy consumption for school buildings located in extremely hot climates.Therefore,this paper contributes to the development of DCV and mechanical ventilation systems through a comprehensive evaluation of these systems to maintain acceptable indoor air quality(IAQ)while minimizing cooling energy demands for school buildings located in the harsh hot climate of Saudi Arabia.The evaluation is based on a calibrated whole-building energy model and validated IAQ predictions using field data obtained from a school case study in Jeddah.The results of this research study confirm that hourly and sub-hourly monitoring of indoor CO_(2)concentration is required to ensure optimal design and operation of the ventilation systems in schools.In addition,the analyses indicate that a 13%increase in cooling energy end-use can result for any additional 0.1 students/m^(2)density increase in the classrooms.However,the energy penalties related to ventilation needs can be reduced by up to 25%using DCV instead of conventional mechanical ventilation systems for school buildings located in Saudi Arabia’s hot climate.

Influence of staff number and internal constellation on surgical site infection in an operating room

Prediction of bacteria-carrying particle （BCP） dispersion and particle distribution released from staffmem- bers in an operating room （OR） is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staffwithin the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking （LPT） for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration （cfu/ms） was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles （5-10 i^m）. Risk factors for surgical site infections （SSls） must be well understood to develop more effective prevention programs.