Mechanical Ventilation in the Critically Ill Patient

Gianluigi Li Bassi, MD, PhD

John G. Laffey, BSc, MB, MD, MA, DSc

Critically ill patients frequently require invasive ventilatory support to maintain gas exchange, optimize oxygen consumption and delivery, protect the airways, avoid secondary brain injury, and in many cases to support respiratory failure and buy time until lungs recover. Mechanical ventilation (MV) has been particularly beneficial in patients with life-threatening conditions, such as acute respiratory distress syndrome (ARDS) and other causes such as acute hypoxemic respiratory failure. In the last few decades, we have also learned that in this context MV could also be detrimental and cause iatrogenic lung injury and damage to other vital organs. In this special issue of Seminars in Respiratory and Critical Care Medicine, we invited world-renowned experts in the fields of MV, ARDS, respiratory physiotherapy, nosocomial infections, and extracorporeal membrane oxygenation (ECMO) to provide insights on the most recent developments in the physiopathology, epidemiology, monitoring, and treatment of patients who require MV. In addition, considering that Seminars in Respiratory and Critical Care Medicine Editorial Board planned this special issue while a ravaging pandemic caused by SARS-CoV-2 was challenging intensive care units (ICUs) worldwide, MV for patients with coronavirus disease 2019 (COVID-19) is also a key topic of this issue.

This collection starts with an in-depth discussion by Pelosi and colleagues of the physiologic and pathophysiologic consequences of MV in the critically ill patients. Bates and collaborators demonstrate how high quality data streams, obtained from patients on MV can also be utilized to develop advanced physiologic compartmental in silico models of the lung in patients with ARDS. These models enable a greater understanding of underlying mechanisms by which MV may lead to harm, in the context of specific lung pathophysiologic conditions, and how such harm might be avoided. Thereby, the reader will recognize the value and limitless capabilities of data acquired from mechanically ventilated patients. Rezoagli and colleagues critically assess the utility and clinical applications of both standard and more recently described parameters and indices, measurable at or near the bedside, to assess lung injury severity and the MV intensity. These emerging indices provide the potential to detect injurious ventilation approaches in real time, offering the potential to adjust ventilation and thereby reducing risks of ventilation-induced lung injury. Bastia and collaborators familiarize the readers with the concept of asymmetry in lung injury, such as can be seen during severe unilateral pneumonia or asymmetrical ARDS. This concept is surprisingly underrated and understudied in the management of mechanically ventilated patients. As clearly explained by the authors, MV in this context is particularly challenging with increased iatrogenic risks due to the substantial imbalance in pulmonary mechanics between the compliant and stiffer sick lung regions. Hanley et al discuss the challenges presented by the syndromic “Berlin” definition of ARDS, examine novel insights into the epidemiology of ARDS, the impact of failures in ARDS diagnosis, the role of lung imaging in ARDS diagnosis, sex differences that exist in ARDS management and outcomes, and the progression of ARDS following initial diagnosis. They challenge the utility of distinguishing ARDS from other causes of acute hypoxemic respiratory failure and identify issues that may need to be addressed in a revised definition. Tronstad and colleagues assess the role of cardiorespiratory physiotherapy in optimizing secretion clearance, gas exchange, lung recruitment, and aiding with weaning from MV for critically ill patients receiving MV in ICU. They provide information that should inform and enable clinicians to deliver personalized and optimal patient care, based on the patients' unique needs and guided by accurate interpretation of assessment findings and the current evidence. As this evidence base develops and physiotherapists become more integrated into the ICU multidisciplinary team, the potential for improved short- and long-term outcomes in patients receiving MV is clear. Given the COVID-19 pandemic, the study from Brioni and colleagues, describing the state-of-the art of non-invasive ventilation (NIV) and MV setting and usage for acute hypoxemic respiratory failure of COVID-19 patients, is timely. They discuss widely adopted strategies, such as awake prone positioning, which now has good evidence for its potential to reduce the need for invasive MV. Other areas of debate include the use of NIV outside the ICU, the risk and incidence of NIV failure, the risk and impact of patient self-induced lung injury, and the management of invasive MV in COVID-19 patients. Fior and colleagues discuss MV during ECMO. In this context, clinicians are frequently challenged to optimize the ventilatory strategy for improving gas exchange, while avoiding ventilator-induced lung injury. Thus, Fior et al explain in detail the dynamics of ventilatory adjustments throughout the various stages of ECMO treatment, from full support to weaning from ECMO and recovery. Fanning and collaborators provide novel insights regarding ventilator-associated pneumonia, which remains a very frequent complication of MV that increases patient morbidity and mortality. They emphasize controversial dissimilarities between the American and European guidelines for the management of this complication. As for adjunctive therapies during MV, Gianni and collaborators detail applications of therapeutic gases, while Guerin et al provide a comprehensive account of the role of neuromuscular blocking agents (NMBA) and prone position in the management of ARDS. Interestingly, Gianni systematically describe biology, pharmacokinetics, and clinical use of inhaled nitric oxide, from the discovery by Ignarro/Furchgott/Murad of nitric oxide as a signaling molecule in the cardiovascular system, which was awarded with the 1998 Nobel Prize in Physiology or Medicine to novel uncharted clinical applications. Many other therapeutic gases are outlined by the authors, such as helium, carbon monoxide, inhaled anesthetics and gases at very early phase of investigation, i.e., hydrogen. Guérin et al instead characterize the pathophysiological rationale and indications for NMBA and prone position, carefully reviewing current evidence and commenting on conflicting trials to assist the reader in understanding advantages and limitations of these adjunctive measures, when routinely applied in clinical practice. Finally, taking into account benefits and disadvantages of MV, intensive care doctors are well aware of the importance of early discontinuation of ventilatory support, when patients have appropriately recovered. Thus, in this special issue, it was crucial to have a chapter on liberation from MV and you will find key recommendations by Burns et al and the most recent evidence to identify, very early, candidates for liberation from MV, and detailed and practical advice on how to optimize, monitor and support patients pre and post discontinuation of MV.

In conclusion, we are confident that the readers of Seminars of Respiratory and Critical Care Medicine will enjoy this special issue and will find several new insights that can readily be applied at the bedside of critical patients receiving MV to ultimately improve outcomes.

Publication History

Article published online:
01 June 2022