Challenges and controversies in COVID-19 respiratory failure
COVID-19 pneumonia presents distinctive questions and challenges traditional conventions of management of respiratory failure. The trajectory of recommendations on customary intubation practices has undertaken significant paradigm shifts. This review will discuss the role of high flow nasal cannula oxygenation in mitigating respiratory distress in SARS-COV2 pneumonia and will explore the indices that can aid in the timely recognition of failure of non-invasive respiratory support modalities and escalation to mechanical ventilation. The work of breathing is a valuable yardstick for understanding increasing lung elastance. Quantifying work of breathing, though, has its own unique challenges. This article also discusses the emerging controversial proposals of employing high tidal volumes and low PEEP in mechanical ventilation of COVID-19 pneumonia and will review the key concepts of lung stress and strain and the implications of “static” versus “dynamic” strain in ventilator induced lung injury. It considers the established facts of inducing lung strain with larger dynamic deformations caused by high tidal volumes and the benefit of high PEEP in homogenizing the strain distribution. The review suggests that the isolated ground glass opacities could pose as “stress raisers.” The effects of these regional lung homogeneities in amplifying local and global lung stress are also discussed as well as the benefits of PEEP beyond its effect as a pressure barrier against alveolar filling and its utility in lungs with near normal compliance. A physiologic approach is presented to counter the non-uniform and heterogeneous presentations of this unique disease rather than conforming to rigid protocols. One size probably
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