Articles: mechanical-ventilation.
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Pulmonary capillary blood volume is a major determinant of lung gas transport efficiency, and also potentially related to ventilator-induced lung injury. Yet, knowledge on how lung expansion influences pulmonary blood volume in injured lungs is scant. We hypothesize that lung expansion produced by positive end-expiratory pressure (PEEP) modulates the global and regional spatial distribution of pulmonary blood volume. ⋯ During low-volume mechanical ventilation and systemic endotoxemia, lung blood volume is markedly heterogeneously distributed, and modulated by PEEP. Nondependent regions are susceptible to low blood volume and capillary closure. Recruitment of pulmonary vascular blood volume with gas volume is nonlinear, limited at intermediate PEEP indicating its advantage to spatial distribution of blood volume.
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Airway mucus is a highly specialised secretory fluid which functions as a physical and immunological barrier to pathogens whilst lubricating the airways and humifying atmospheric air. Dysfunction is common during critical illness and is characterised by changes in production rate, chemical composition, physical properties, and inflammatory phenotype. Mucociliary clearance, which is determined in part by mucus characteristics and in part by ciliary function, is also dysfunctional in critical illness via disease related and iatrogenic mechanisms. ⋯ Mucolytic therapies are designed to decrease viscosity, improve expectoration/suctioning, and thereby promote mucus removal. Mucolytics, including hypertonic saline, dornase alfa/rhDNase, nebulised heparin, carbocisteine/N-Acetyl cysteine, are commonly used in critically ill patients. This review summarises the physiology and pathophysiology of mucus and the existing evidence for the use of mucolytics in critically ill patients and speculates on journey to individualised mucolytic therapy.
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Assessing and quantifying recruitability are important for characterizing ARDS severity and for reducing or preventing the atelectrauma caused by the cyclic opening and closing of pulmonary units. Over the years, several methods for recruitment assessment have been developed, grouped into three main approaches: 1) Quantitative CT Scanning: This method accurately measures the amount of atelectatic lung tissue that regains aeration; 2) Regional Gas Volume Measurement: Based on anatomical markers, this approach assesses gas volume within a specified lung region; 3) Compliance-Based Gas Volume Measurement: This technique compares actual gas volume at a given pressure to expected values, assuming respiratory system compliance is constant within the explored pressure range. ⋯ This paper details the distribution of opening and closing pressures throughout the lung parenchyma, which underpin the concept of recruitability. The distribution of recruitable regions corresponds to atelectasis distribution, with the pressure needed for recruitment varying according to whether the atelectasis is "loose" or "sticky." We also discuss the effects of different PEEP levels on preventing atelectrauma, the importance of keeping some lung areas closed throughout the respiratory cycle, and briefly cover the roles of sigh ventilation, prone positioning, and the closed lung approach.
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Journal of critical care · Feb 2025
LetterElectrical impedance tomography to set high pressure in time-controlled adaptive ventilation.
TCAV (Time controlled adaptive ventilation), a combination of settings applied to the APRV (airway pressure release ventilation) mode, provides personalized ventilation tailored to the lung condition in ARDS (acute respiratory distress syndrome). The objective was to evaluate whether electrical impedance tomography (EIT) could serve as a tool for guiding Phigh level in TCAV for ARDS patients. ⋯ EIT enabled detection of regional ventilation distribution on TCAV during a decremental Phigh trial and thus enabled the determination of a best EIT-derived-Phigh through an individualized approach, achieving best compromise between overdistension and collapse. The observed overdistention variability highlights the necessity of Phigh level personalization on TCAV.