Absolute electrical impedance tomography (aEIT) guided ventilation therapy in critical care patients: simulations and future trends

Thoracic electrical impedance tomography (EIT) is a noninvasive, radiation-free monitoring technique whose aim is to reconstruct a cross-sectional image of the internal spatial distribution of conductivity from electrical measurements made by injecting small alternating currents via an electrode array placed on the surface of the thorax. The purpose of this paper is to discuss the fundamentals of EIT and demonstrate the principles of mechanical ventilation, lung recruitment, and EIT imaging on a comprehensive physiological model, which combines a model of respiratory mechanics, a model of the human lung absolute resistivity as a function of air content, and a 2-D finite-element mesh of the thorax to simulate EIT image reconstruction during mechanical ventilation. The overall model gives a good understanding of respiratory physiology and EIT monitoring techniques in mechanically ventilated patients. The model proposed here was able to reproduce consistent images of ventilation distribution in simulated acutely injured and collapsed lung conditions. A new advisory system architecture integrating a previously developed data-driven physiological model for continuous and noninvasive predictions of blood gas parameters with the regional lung function data/information generated from absolute EIT (aEIT) is proposed for monitoring and ventilator therapy management of critical care patients

An Integrated Physiological Model of the Lung Mechanics and Gas Exchange Using Electrical Impedance Tomography in the Analysis of Ventilation Strategies in ARDS Patients

Mouloud Denai, M. Mahfouf, A. Wang, D. A. Linkens, and G. H. Mills, 'An Integrated Physiological Model of the Lung Mechanics and Gas Exchange Using Electrical Impedance Tomography in the Analysis of Ventilation Strategies in ARDS Patients'. Paper presented at the 3rd International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2010), 20 - 23 January 2010, Valencia, Spain.Peer reviewedFinal Published versio

Is inspiratory muscle training (IMT) an acceptable treatment option for people with chronic obstructive pulmonary disease (COPD) who have declined pulmonary rehabilitation (PR) and can IMT enhance PR uptake? A single-group prepost feasibility study in a home-based setting

Objectives This feasibility study aimed to assess the acceptability of inspiratory muscle training (IMT) in people with chronic obstructive pulmonary disease (COPD) who declined pulmonary rehabilitation (PR) as a potential treatment option or precursor to PR. Objectives were to assess attitudes to IMT, PR and alternatives to PR; factors influencing adherence with IMT and acceptability of outcome measures, research tools and study protocol. Design A pragmatic, mixed methods, prepost feasibility study was conducted. Recruitment took place over a 4-month period. Participants were followed up for a period of 6 months. Settings IMT sessions and assessments were conducted in the domiciliary setting. Participants Inclusion criteria: people over the age of 35, stable COPD, Medical Research Council Dyspnoea scale of 3 or above, declined PR. Exclusion criteria: history of spontaneous pneumothorax, incomplete recovery from a traumatic pneumothorax, asthma, known recently perforated eardrum, unstable angina, ventricular dysrhythmias, cerebrovascular event or myocardial infarction within the last 2 months. Participants were selected from a purposive sample. Of the 22 potential participants screened, 11 were recruited and interviewed. Ten participants commenced IMT. Seven participants completed the follow-up assessment. Intervention Eight weeks of IMT twice a day, 5 days a week with visits once weekly by a physiotherapist. Unsupervised IMT twice a day three times a week until follow-up at 6 months. Outcomes Acceptability of IMT and the study process was explored via semi-structured interviews. Adherence with IMT was assessed by the Powerbreathe K3 device and participant diaries. Uptake of PR was identified. Results IMT was found to be acceptable. Adherence was explored. Four people went on to participate in PR. Conclusions Feasibility was established. A randomised controlled trial is warranted to establish efficacy and cost-effectiveness of IMT in those who decline PR and IMT as an intervention to promote uptake of PR

Derivation and validation of a prognostic model for postoperative risk stratification of critically ill patients with faecal peritonitis

Background Prognostic scores and models of illness severity are useful both clinically and for research. The aim of this study was to develop two prognostic models for the prediction of long-term (6 months) and 28-day mortality of postoperative critically ill patients with faecal peritonitis (FP). Methods Patients admitted to intensive care units with faecal peritonitis and recruited to the European GenOSept study were divided into a derivation and a geographical validation subset; patients subsequently recruited to the UK GAinS study were used for temporal validation. Using all 50 clinical and laboratory variables available on day 1 of critical care admission, Cox proportional hazards regression was fitted to select variables for inclusion in two prognostic models, using stepwise selection and nonparametric bootstrapping sampling techniques. Using Area under the receiver operating characteristic curve (AuROC) analysis, the performance of the models was compared to SOFA and APACHE II. Results Five variables (age, SOFA score, lowest temperature, highest heart rate, haematocrit) were entered into the prognostic models. The discriminatory performance of the 6-month prognostic model yielded an AuROC 0.81 (95% CI 0.76–0.86), 0.73 (95% CI 0.69–0.78) and 0.76 (95% CI 0.69–0.83) for the derivation, geographic and temporal external validation cohorts, respectively. The 28-day prognostic tool yielded an AuROC 0.82 (95% CI 0.77–0.88), 0.75 (95% CI 0.69–0.80) and 0.79 (95% CI 0.71–0.87) for the same cohorts. These AuROCs appeared consistently superior to those obtained with the SOFA and APACHE II scores alone. Conclusions The two prognostic models developed for 6-month and 28-day mortality prediction in critically ill septic patients with FP, in the postoperative phase, enhanced the day one SOFA score’s predictive utility by adding a few key variables: age, lowest recorded temperature, highest recorded heart rate and haematocrit. External validation of their predictive capability in larger cohorts is needed, before introduction of the proposed scores into clinical practice to inform decision making and the design of clinical trials

Predicting outcomes of hematological malignancy patients admitted to critical care

Background: Critical care (CC) admission has traditionally been viewed as likely to result in a poor outcome for hematological malignancy (HM) patients. Such a view can have implications for decisions surrounding CC admission. Recent studies have challenged this poor prognostication, however, there still remains limited data to support CC admission and escalation decisions and to elucidate risk factors which independently predict short- and longer-term survival outcomes. Methods: We retrospectively analyzed a large cohort of adult HM patients (n=437) admitted to CC over a sixteen-year period, with the specific aim of identifying risk factors present at CC unit admission that could help to predict outcome. We assessed all-cause mortality at CC discharge (CC mortality, primary outcome) and at further time points (hospital discharge and 12-months post-discharge from CC). Single variable and multivariate analyses were performed to identify independent predictors of outcome. Results: CC unit and hospital mortality rates were 33.4% (146 patients) and 46.2% (202 patients) respectively. At six-month and one-year follow-up, mortality increased to 59.5% and 67.9% respectively. At single variable adjusted regression analysis, eight factors were associated with CC mortality: APACHE II score, the number of organs supported, requirement for continuous renal replacement therapy (CRRT), cardiovascular support, or respiratory support (invasive and non-invasive), the ratio between arterial partial pressure of oxygen (PaO2) and the inspired oxygen concentration (FiO2) (P/F ratio) on CC admission, and the lowest P/F ratio during CC admission. However, only three factors showed independent predictive capacity for CC outcome at multivariate logistic regression analysis; APACHE II score on admission, requirement for ventilation and lowest P/F ratio. Conclusion: One third of HM patients admitted to CC died on the unit and, following admission to CC, approximately one-third of HM patients survived over 1 year. Our data show that, while a diagnosis of HM should not preclude admission of patients who might otherwise benefit from CC support, the prognosis of those with a high APACHE II score upon admission, or those requiring IMV remains poor, despite considerable advances in IMV techniques

Critical care outcomes in patients with pre-existing pulmonary hypertension: insights from the ASPIRE registry

Pulmonary Hypertension (PH) is a life-shortening condition characterised by episodes of decompensation precipitated by factors such as disease progression, arrhythmias and sepsis. Surgery and pregnancy also place additional strain on the right ventricle. Data on critical care management in patients with pre-existing PH are scarce. We conducted a retrospective observational study of a large cohort of patients admitted to the critical care unit of a national referral centre between 2000–17 to establish acute mortality, evaluate predictors of in-hospital mortality and establish longer-term outcomes in survivors to hospital discharge. 242 critical care admissions involving 206 patients were identified. Hospital survival was 59.3%, 94% and 92% for patients admitted for medical, surgical or obstetric reasons. Medical patients had more severe physiological and laboratory perturbations than patients admitted following surgical or obstetric interventions. Higher APACHE II score, age and lactate, and lower SpO2/FiO2, platelet count and sodium level were identified as independent predictors of hospital mortality. An exploratory risk score, OPALS (Oxygen (SpO2:FiO2), ≤185; Platelets, ≤196×109·L−1; Age, ≥37.5 years; Lactate, ≥2.45 mmol·L−1; Sodium, ≤130.5 mmol·L−1), identified medical patients at increasing risk of hospital mortality. One of nine patients (11%) who were invasively ventilated for medical decompensation and 50% of patients receiving renal replacement therapy left hospital alive. There was no significant difference in exercise capacity or functional class between follow-up and pre-admission in patients who survived to discharge. These data have clinical utility in guiding critical care management of patients with known PH. The exploratory OPALS score requires validation

‘Stepping away from the computer and into the sweats': The construction and negotiation of exercise identities in a Norwegian public company

While research has found that a developed exercise identity enables individuals to view exercise participation as self- reinforcing, the social barriers to such exercise identity development and participation have not been fully addressed. The subsequent aim of this study was to explore some of the social complexities at play in terms of how company employees construct and manage their exercise identities within a work place setting. A case-study method was used to address the research issue over a nine-month period. The case to be studied included a sample of 72 employees from a Norwegian public company who participated in an on-going work-based exercise programme called ‘Exercise for all’. The principal means of data collection comprised participant observation, individual interviews and exercise logbooks. The data were subject to inductive analysis. The primary barriers to exercise participation included high levels of social comparison in a competitive working context, particularly in relation to ‘competent colleagues’, and feelings of guilt associated with partaking in ‘recreational’ activities during work hours. Strategies engaged with to overcome and negotiate such obstacles included justifying participation through a health-related discourse, and constructing a more distinct ‘worker-exerciser’ identity

Ionization of the Venusian atmosphere from solar and galactic cosmic rays

The atmospheres of the terrestrial planets are exposed to solar and galactic cosmic rays, the most energetic of which are capable of affecting deep atmospheric layers through extensive nuclear and electromagnetic particle cascades. In the Venusian atmosphere, cosmic rays are expected to be the dominant ionization source below ∼100 km altitude. While previous studies have considered the effect of cosmic ray ionization using approximate transport methods, we have for the first time performed full 3D Monte Carlo modelling of cosmic ray interaction with the Venusian atmosphere, including the contribution of high-Z cosmic ray ions (Z=1-28). Our predictions are similar to those of previous studies at the ionization peak near 63 km altitude, but are significantly different to these both above and below this altitude. The rate of atmospheric ionization is a fundamental atmospheric property and the results of this study have wide-reaching applications in topics including atmospheric electrical processes, cloud microphysics and atmospheric chemistry

Star Formation and Dynamics in the Galactic Centre

The centre of our Galaxy is one of the most studied and yet enigmatic places in the Universe. At a distance of about 8 kpc from our Sun, the Galactic centre (GC) is the ideal environment to study the extreme processes that take place in the vicinity of a supermassive black hole (SMBH). Despite the hostile environment, several tens of early-type stars populate the central parsec of our Galaxy. A fraction of them lie in a thin ring with mild eccentricity and inner radius ~0.04 pc, while the S-stars, i.e. the ~30 stars closest to the SMBH (<0.04 pc), have randomly oriented and highly eccentric orbits. The formation of such early-type stars has been a puzzle for a long time: molecular clouds should be tidally disrupted by the SMBH before they can fragment into stars. We review the main scenarios proposed to explain the formation and the dynamical evolution of the early-type stars in the GC. In particular, we discuss the most popular in situ scenarios (accretion disc fragmentation and molecular cloud disruption) and migration scenarios (star cluster inspiral and Hills mechanism). We focus on the most pressing challenges that must be faced to shed light on the process of star formation in the vicinity of a SMBH.Comment: 68 pages, 35 figures; invited review chapter, to be published in expanded form in Haardt, F., Gorini, V., Moschella, U. and Treves, A., 'Astrophysical Black Holes'. Lecture Notes in Physics. Springer 201