Ventilator-induced lung injury: historical perspectives and clinical implications

Mechanical ventilation can produce lung physiological and morphological alterations termed ventilator-induced lung injury (VILI). Early experimental studies demonstrated that the main determinant of VILI is lung end-inspiratory volume. The clinical relevance of these experimental findings received resounding confirmation with the results of the acute respiratory distress syndrome (ARDS) Network study, which showed a 22% reduction in mortality in patients with the acute respiratory distress syndrome through a simple reduction in tidal volume. In contrast, the clinical relevance of low lung volume injury remains debated and the application of high positive end-expiratory pressure levels can contribute to lung overdistension and thus be deleterious. The significance of inflammatory alterations observed during VILI is debated and has not translated into clinical application. This review examines seminal experimental studies that led to our current understanding of VILI and contributed to the current recommendations in the respiratory support of ARDS patients

Pulmonary Gas Transport and Drug Delivery in a Patient Specific Lung Model During Invasive High Frequency Oscillatory Ventilation

The objective of this dissertation research was to investigate gas transport, mixing and aerosol-drug delivery during high frequency oscillatory ventilation (HFOV) for various ventilator specific conditions that are vital to critical care clinicians. A large eddy simulation based computational fluid dynamics approach was used in a patient specific human lung model to analyze the effect of invasive HFOV on patient management. Different HFOV waveform shapes and frequencies was investigated and the square waveform was found to be most efficient for gas mixing; resulting in the least wall shear stress on the lung epithelium layer thereby reducing the risk of barotrauma to both airways and the alveoli for patients undergoing therapy. Traditional (outlet) boundary conditions based on mass fraction or outlet pressures were found to be inadequate in describing the complex flow physics that occurs during HFOV. Physiological boundary conditions that used the time-dependent pressure coupled with the airways resistance and compliance (R&C) were derived and used for the first time to investigate the lung lobar ventilation and gas exchange for accurate HFOV modeling. A Lagrangian approach was then used to model gas-solid two-phase flow that allowed investigation of the potential of aerosol-drug delivery under HFOV treatment. We report, for the first time, computational fluid dynamics studies to investigate the possibilities of aerosol drug delivery under HFOV. Understanding the role of different carrier gases on the gas exchange and particle deposition, which may allow for optimum drug delivery and ventilation strategy during HFOV. Increasing the operating frequency resulted in a significant change in the global and local deposition indicating strong dependency on the frequency, which could be beneficial for the targeted drug delivery. The global deposition as a fraction of the total injected particles at the endotracheal tube inlet was equivalent to the cases of normal breathing and conventional mechanical ventilation signifying a potential for efficient drug delivery during HFOV. In addition, HFOV had a unique characterization of the local particle deposition due to the rapid ventilation process and a strong influence of the endotracheal tube jet. Very often during ventilation therapy, a clinician uses a cocktail of various gases to enhance targeted therapy. To quantify this process for a futuristic HFOV based patient management, we undertook detailed studies to understand the role of carrier gas properties in gas exchange and particle transport during HFOV. A substantial amplification of the pendelluft flow was achieved by utilizing a low-density carrier gas instead of air, which resulted in gas exchange improvement. Reducing the carrier gas density was found to significantly alter the aerosol-drug delivery under HFOV management. As the density decreased, the deposition fraction in the upper tracheobronchial tree decreased, indicating enhancement of the lung periphery delivery. Furthermore, the filtered aerosol-drug in the ventilator circuit could be significantly reduced by using Heliox, and further reduction could be achieved by reducing the operating frequency. In general, high-frequency oscillatory ventilation therapy could be improved under Heliox with greater content of Helium, thereby reducing the lung hyperinflation risk

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 402)

This bibliography lists 244 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during Nov. 1992. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Mechanical Ventilation

The therapeutic alliance has been found to predict psychotherapy outcome in numerous studies. However, critics maintain that the therapeutic alliance is a by-product of prior symptomatic improvements. Moreover, almost all alliance research to date has used differences between patients in alliance as predictor of outcome, and results of such analyses do not necessarily mean that improving the alliance with a given patient will improve outcome (i.e., a within-patient effect). In a sample of 646 patients (76% women, 24% men) in primary care psychotherapy, the effect of working alliance on next session symptom level was analyzed using multilevel models. The Clinical Outcomes in Routine Evaluation–Outcome Measure was used to measure symptom level, and the patient version of the Working Alliance Inventory–Short form revised (Hatcher & Gillaspy, 2006) was used to measure alliance. There was evidence for a reciprocal causal model, in which the alliance predicted subsequent change in symptoms while prior symptom change also affected the alliance. The alliance effect varied considerably between patients. This variation was partially explained by patients with personality problems showing stronger alliance effect. These results indicate that the alliance is not just a by-product of prior symptomatic improvements, even though improvement in symptoms is likely to enhance the alliance. Results also point to the importance of therapists paying attention to ruptures and repair of the therapy alliance. Generalization of results may be limited to relatively brief primary care psychotherapy

Phantom and computational studies towards the clinical translation of gas in scattering media absorption spectroscopy into neonatal respiratory care

Everything except vacuum is heterogeneous to some extent. Even media that we consider homogeneous (such as pure gases and water) can be taken apart into individual heterogeneities (such as atoms and molecules), which can be distinguished with a sufficiently fine probe. Absorption spectroscopy was extensively used by Robert Bunsen and Gustav Kirchhoff in the 1860’s to separate, identify and measure various chemical substances. They defined a line of research, where traces of elements were just detectable with the aid of specialized instruments like the spectroscope, and since then, the absorption lines have been subject of experimental and theoretical developments. Today, we know that the nature of the absorption lines can be described by quantum mechanical changes induced in the atoms or molecules, and with the advances in light sources and sensing technologies, absorption spectroscopy has become a tremendously useful tool with a wide range of applications. The studies presented in this thesis are related to gas absorption spectroscopy, in particular, a technique called GASMAS, which stands for “GAs in Scattering Media Absorption Spectroscopy”. This spectroscopy technique was introduced in Lund University in 2001 by S. Svanberg’s group, to study the spectral features of gases inside porous or hollowed scattering media, combining laser spectroscopy with sensitive modulation techniques. Unlike solids and liquids, which have a smooth absorption and scattering wavelength dependence (1 − 10 nm), gases exhibit sharp absorptive features (10−4 nm). This difference between the absorption spectra of solid state matter and gases, is the corner stone of this technique. In a typical GASMAS measurement, the laser wavelength is scanned across at least one of the absorption lines of the gas of interest. The small gas absorption signal (embedded in the scattered spectrum from the bulk material) is then filtered from the detected signal, making it possible to retrieve the gas concentrations and study their diffusion dynamics using the principles of the Beer-Lambert law. Although there is evidence of the potential of GASMAS to sense oxygen and water vapor in human cavities, such as the ear, nasal sinuses, lungs, intestines and hip bone, one the most promising clinical applications could be the lung function assessment in neonates. The focus of this thesis is to investigate the potential of translating GASMAS into such an application, combining a computational and experimental approach. Most of the work was done in a collaboration between Biophotonics@Tyndall, the Infant Centre (hosted at the Cork University Maternity Hospital-UCC) and the Swedish industry partner, GPX Medical who have built a pioneering GASMAS instrument, suitable for clinical use. The motivation behind this collaborative work, is to assist clinicians in the monitoring of lung function in premature newborns, as their lungs lack structural and biochemical maturation, which can result in respiratory failure. Currently, the use of GASMAS is limited to observational studies with healthy babies. Thus, the improvement and optimization of the technology depends on feasibility tests with tissue-like models. Phantoms mimicking the geometry and optical properties of the main thoracic organs, were created to study the influence of source detector positioning and chest physiognomy in the GASMAS signals. A functional phantom resembling the anatomy, temperature and humidity of the respiratory zone, was also developed to investigate the potential of GASMAS technique in measuring changes in inflated volume. The optimization of source-detector configurations over the thorax is one of the challenges in the clinical translation of GASMAS. It is crucial to define the optimal probe positioning, to obtain the highest possible signal reaching the detector, which also carries information of the gas absorption in lung tissue. Computational studies are then used to simulate the light transport in accurate anthropomorphic models, which contributes with the understanding of near infra-red interaction with the thorax, and most of all, to find the probe locations for which the detection of gas absorption is feasible, and enhance the data acquisition in future clinical studies. This document includes the theoretical background of GASMAS, the basics of respiratory physiology, and the current methods for clinical monitoring and diagnostics of lung pathologies in neonates. The following two chapters, show how the developed phantom and computational models enable the recreation of different clinical scenarios, suitable for GASMAS studies. The main contribute is the identification of the minimum requirements necessary to further improve and advance towards a GASMAS bedside clinical device, that can potentially be used, for lung function assessment and monitoring in neonatal respiratory health

Determination of local oxygen consumption by healthy and diseased lungs in a rabbit model.

Gu Jia-Shi.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 117-148).Abstracts in English and Chinese.Title --- p.iAbstract (English) --- p.iiiAbstract (Chinese) --- p.ivAcknowledgments --- p.vStatement of Originality --- p.viList of Abbreviations --- p.viiiList of Figures --- p.xiList of Tables --- p.xiiiTable of Contents --- p.xivChapter Section One : --- Introduction & Literature ReviewIntroduction & Objective --- p.2IntroductionObjective of the present studyChapter Chapter. 1 --- A Review of Chronic lung disease (CLD) --- p.6Chapter 1. --- BPD 226}0ؤ an example of CLDChapter 2. --- Pathological change & Clinical presentationChapter 3. --- Clinical sequel of CLD infantsChapter 3.1 --- O2 consumption of CLD infantsChapter 3.1-1 --- Oxygen consumptionChapter 3.1-2 --- Oxygen transportationChapter 3.1-2a --- Dissolved O2Chapter 3.1-2b --- HaemoglobinChapter 3.2 --- Energy expenditure of CLD infantsChapter 3.3 --- Growth rate of CLD infantsChapter 4. --- Treatment & Management of CLD infantsChapter 4.1 --- DiureticsChapter 4.2 --- BronchodilatorsChapter 4.3 --- CorticosteroidsChapter 5. --- "Interpretations of the observed phenomena, why does CLD impair growth?"Chapter 5.1 --- The traditional viewChapter 5.2 --- Disagreement with the traditional viewChapter Chapter 2 --- Measurement of oxygen consumption --- p.20Chapter 1. --- Invasive measurement of VO2Chapter 1.1 --- Cardiac outputChapter 1.2 --- Fick methodChapter 1.3 --- Advantages and Disadvantages of Fick method in estimating VO2Chapter 1.4 --- Measurement of cardiac output by thermodilutionChapter 1.4-1 --- Advantages and Disadvantages of Thermodilution MethodChapter 2. --- Non-invasive measurement of VO2Chapter 2.1 --- Metabolic analyzer---DeltatraćёØIIChapter 2.2 --- Paramagnetic sensorChapter 3. --- Measured and calculated oxygen consumptionChapter 3.1 --- Difference between mVO2 and cVO2Chapter 4. --- SummaryChapter Chapter 3 --- Hypothesis --- p.34Chapter 1. --- Possible explanations for the difference between mV02 & cV02Chapter 1.1 --- Measurement variability and Mathematical errorChapter 1.2 --- Oxygen consumption of the lungChapter 1.3 --- VO2pul with lung damageChapter 1.4 --- "Neutrophils, Macrophages and oxygen consumption"Chapter 2. --- HypothesisChapter Section Two : --- Methods & MaterialsChapter Chapter 1 --- Animal Model --- p.41Chapter Chapter 2. --- Materials --- p.43Chapter 1. --- AnimalsChapter 2. --- Chemicals used for inducing lung damageChapter 2.1 --- Acute damage groupChapter 2.1-1 --- N-nitroso-N-methylurethane (NNNMU)Chapter 2.1-2 --- Administrations to rabbitsChapter 2.2 --- Chronic damage groupChapter 2.2-1 --- Bleomycin (BLM)Chapter 2.2-2 --- Pulmonary toxicity of BleomycinChapter 2.2-3 --- Administration to animalsChapter Chapter 3 --- Instruments --- p.50Chapter 1. --- Measurement of VO2 and VCO2 226}0ؤDeltatracIÍёØ Metabolic analzyerMeasurement of cardiac outpu´tؤCardiomax II model85Chapter Chapter 4 --- Methods --- p.58Chapter 1. --- N-nitroso-N-methylurethane (NNNMU) PreparationChapter 2. --- Bleomycin PreparationChapter 3. --- 2.5% pentobarbitone PreparationChapter 4. --- Animal PreparationChapter 4.1 --- Control (Normal) groupChapter 4.2 --- A cute lung damage groupChapter 4.3 --- Chronic lung damage groupChapter 5. --- Preparation of the animals for VO2 measurementChapter 6. --- Measurement of oxygen consumptionChapter 6.1 --- VO2wb measurementChapter 6.2 --- VO2b measurementChapter 7. --- HistopathologyChapter 8. --- StatisticsChapter Section Three : --- Results --- p.69Chapter 1. --- Healthy (Control) groupChapter 1.1 --- Pulmonary histologyChapter 2. --- Acute lung damage groupChapter 2.1 --- Pulmonary histologyChapter 3. --- Chronic lung damage groupChapter 3.1 --- Pulmonary histologyChapter 4. --- Comparison of the pulmonary oxygen consumption among the three groupsChapter Section Four : --- Discussion --- p.97Chapter Section Five : --- Conclusion --- p.111Chapter Section Six : --- Future Studies --- p.114Chapter Section Seven : --- Bibliography --- p.11

Simulation in Nursing: Historical Analysis and Theoretical Modeling in Support of a Targeted Clinical Training Intervention

The use of simulation is widespread in healthcare education, and the potential impact of its use large. This is especially true for nursing education as we look to address problems with obtaining clinical experiences, develop critical thinking skills and create methods to measure the impact of simulation interventions. There is substantial empirical evidence in support of predictive relationships between simulation training interventions and knowledge acquisition. This has been extensively demonstrated with the use of a variety of simulation training modalities from standardized patients to human patient simulators. However, data to support changes in clinical practice and improved patient outcomes are quite limited, including attempts to measure the impact of simulation education on retention and transference of knowledge and skill for more complex healthcare process. Additionally, literature searches reveal that only a handful of authors have engaged in the types of foundational work that any emerging science needs. For example, while pieces of the simulation process have been examined in detail, few have attempted to describe what the process of simulation entails at a macro level. Within the past few years some researchers have begun to ask whether there is a causal or predictive relationship present, but few have explored what these associations may look like structurally and what the evidence for them is. The overall objectives of this current research were to: 1) perform an historical review of simulation in healthcare; 2) use this review to outline a new theoretical model of healthcare simulation; and, 3) conduct a small-scale study aimed at pilot-testing and describing part of that model. Hierarchical Task Analysis (HTA) was used to derive an optimum task set for the standard induction of general anesthesia (OTS-SIGA). New Student Registered Nurse Anesthetists (SRNAs) were trained to this task set, and their adherence to the process steps in the clinical setting was then assessed. We also attempted to measure whether repeating the HTA-derived OTS-SIGA simulation training would have an impact on knowledge and transference of simulation-developed skills to the clinical environment. These measures necessitated the development of associated data collection tools and processes for rater training