The aetiology, consequences and prevention of barotrauma: a critical review of the literature

Dexamethasone and transdehydroandrosterone significantly reduce pulmonary epithelial cell injuries associated with mechanical ventilation

Many patients who suffer from pulmonary diseases cannot inflate their lungs normally, as they need mechanical ventilation (MV) to assist them. The stress associated with MV can damage the delicate epithelium in small airways and alveoli, which can cause complications resulting in ventilation-induced lung injuries (VILIs) in many cases, especially in patients with acute respiratory distress syndrome (ARDS). Therefore, efforts were directed to develop safe modes for MV. In our work, we propose a different approach to decrease injuries of epithelial cells (EpCs) upon MV. We alter EpCs' cytoskeletal structure to increase their survival rate during airway reopening conditions associated with MV. We tested two anti-inflammatory drugs dexamethasone (DEX) and transdehydroandrosterone (DHEA) to alter the cytoskeleton. Cultured rat L2 alveolar EpCs were exposed to airway reopening conditions using a parallel-plate perfusion chamber. Cells were exposed to a single bubble propagation to simulate stresses associated with mechanical ventilation in both control and study groups. Cellular injury and cytoskeleton reorganization were assessed via fluorescence microscopy, whereas cell topography was studied via atomic force microscopy (AFM). Our results indicate that culturing cells in media, DEX solution, or DHEA solution did not lead to cell death (static cultures). Bubble flows caused significant cell injury. Preexposure to DEX or DHEA decreased cell death significantly. The AFM verified alteration of cell mechanics due to actin fiber depolymerization. These results suggest potential beneficial effects of DEX and DHEA for ARDS treatment for patients with COVID-19. They are also critical for VILIs and applicable to future clinical studies.NEW & NOTEWORTHY Preexposure of cultured cells to either dexamethasone or transdehydroandrosterone significantly decreases cellular injuries associated with mechanical ventilation due to their ability to alter the cell mechanics. This is an alternative protective method against VILIs instead of common methods that rely on modification of mechanical ventilator modes.

Protocolized versus non-protocolized weaning for reducing the duration of mechanical ventilation in critically ill adult patients

BACKGROUND

Reducing weaning time is desirable in minimizing potential complications from mechanical ventilation. Standardized weaning protocols are purported to reduce time spent on mechanical ventilation. However, evidence supporting their use in clinical practice is inconsistent.

OBJECTIVES

To assess the effects of protocolized weaning from mechanical ventilation on the total duration of mechanical ventilation for critically ill adults; ascertain differences between protocolized and non-protocolized weaning in terms of mortality, adverse events, quality of life, weaning duration, intensive care unit (ICU) and hospital length of stay (LOS); and explore variation in outcomes by type of ICU, type of protocol and approach to delivering the protocol.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2010), MEDLINE (1950 to 2010), EMBASE (1988 to 2010), CINAHL (1937 to 2010), LILACS (1982 to 2010), ISI Web of Science and ISI Conference Proceedings (1970 to 2010), Cambridge Scientific Abstracts (inception to 2010) and reference lists of articles. We did not apply language restrictions.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials of protocolized weaning versus non-protocolized weaning from mechanical ventilation in critically ill adults.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed trial quality and extracted data. A priori subgroup and sensitivity analyses were performed. We contacted study authors for additional information.

MAIN RESULTS

Eleven trials that included 1971 patients met the inclusion criteria. The total duration of mechanical ventilation geometric mean in the protocolized weaning group was on average reduced by 25% compared with the usual care group (N = 10 trials, 95% CI 9% to 39%, P = 0.006); weaning duration was reduced by 78% (N = 6 trials, 95% CI 31% to 93%, P = 0.009); and ICU LOS by 10% (N = 8 trials, 95% CI 2% to 19%, P = 0.02). There was significant heterogeneity among studies for total duration of mechanical ventilation (I(2) = 76%, P < 0.01) and weaning duration (I(2) = 97%, P < 0.01), which could not be explained by subgroup analyses based on type of unit or type of approach.

AUTHORS' CONCLUSIONS

There is some evidence of a reduction in the duration of mechanical ventilation, weaning duration and ICU LOS with use of standardized protocols, but there is significant heterogeneity among studies and an insufficient number of studies to investigate the source of this heterogeneity. Although some study authors suggest that organizational context may influence outcomes, these factors were not considered in all included studies and therefore could not be evaluated.

Protocolized vs. non-protocolized weaning for reducing the duration of mechanical ventilation in critically ill adult patients: Cochrane review protocol

AIM

This paper is a report of the protocol for a review to identify, critically appraise and synthesize the best current evidence supporting the use of weaning protocols compared to non-protocolized practice in liberating patients from mechanical ventilation.

BACKGROUND

Patients experiencing difficulty in weaning require a longer hospital stay and have higher morbidity and mortality. Consequently, efforts to reduce weaning time are desirable to reduce the duration of ventilation and related complications. Standardized weaning protocols are safe and effective in reducing the time spent on mechanical ventilation.Notwithstanding, the evidence supporting their use in practice is inconsistent. The discordant results of studies may reflect the fact that protocols vary in composition and are implemented in different environments by various healthcare providers.

DESIGN

The objectives of this review are to compare the total duration of mechanical ventilation between patients weaned using protocols vs. non-protocolized practice; to ascertain differences between protocolized and non-protocolized weaning with regards to mortality, adverse events, quality of life, weaning duration, ICU and hospital stay; and to explore variation in outcomes by the type of ICU, the type of protocol and approach to delivering the protocol. We will search the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE, CINAHL, ISI Web of Science and LILACS. In addition, we will endeavour to identify unpublished data and contact first authors of studies included in the review to obtain information on unpublished studies or work in progress.

CONCLUSION

This review will provide much needed direction for healthcare professionals in intensive care in terms of both research and practice.

How to use articles about harm: the relationship between high tidal volumes, ventilating pressures, and ventilator-induced lung injury

BACKGROUND

Intensivists commonly encounter patients who may be inadvertently harmed by critical care interventions. This article is designed to guide clinicians in the evaluations of an individual article assessing a question of harm, as well as the sum of multiple pieces of evidence.

OBJECTIVES

To assess the vaidity of a group of articles about the relationship between high tidal volumes and ventilating pressures on ventilator-induced lung injury; to interpret the results of these studies; and to consider whether they apply in practice.

DATA SOURCES

Issues of harm are sometimes measured in randomized trials, but are evaluated more often in myriad observational studies.

DATA EXTRACTION

We use critical appraisal guides for experimental studies (e.g., randomized trials) and observational studies (e.g., cohort studies, case-control studies and case series) that evaluate the potentially harmful exposure of high tidal volumes and ventilating pressures. This involves assessing the validity of the research, then determining the strength of association between the putative harmful exposure and adverse outcomes. These study designs and their interpretation using relative risks and odds ratios are reviewed. Finally, the relevance of this information (or lack thereof) to clinical practice needs to be determined.

DATA SYNTHESIS

Examining these studies individually and in totality, there appears to be a relationship between high tidal volumes and ventilating pressures, although the strength of inference from this research is limited by design issues and sample sizes.

CONCLUSIONS

Critically appraising a body of literature is more challenging than evaluating a single study, but often gives a broader view of the available evidence. Future large, rigorous, randomized trials of different approaches to mechanical ventilation will help to advance our understanding and to better inform our practice.

High-level positive end expiratory pressure management in the surgical patient with acute respiratory distress syndrome

Although the exact incidence of ARDS is not know, it is frequently reported that there are 150,000 cases in the United States each year. Despite major advances in medical and respiratory intensive care, the mortality for patients with ARDS remains exceedingly high and has not changed appreciably from the 50% to 75% reported during the last 25 years. Currently there is no widespread, acceptable, specific therapeutic approach or agent available for the prevention or treatment of ARDS. Clinical management remains entirely supportive in nature. Although most practitioners agree that patients with severe ARDS require mechanical ventilation to maintain adequate gas exchange, controversies center on the amount of supplemental oxygen, level of positive end expiratory pressure (PEEP), and mode of ventilation needed to increase patient survival but reduce ventilator-associated complications. This review provides supportive evidence for the use of high-level PEEP (more than 15 cm H20) in the care of the surgical patient with severe ARDS.