Dynamic Transpulmonary Pressure in Covid-19 Pneumonia: Effects of Positive Pressure, Inspired Oxygen Fraction and Decubitus

In spite of the overwhelming numbers of the current pandemic, many questions remain open regarding the pathophysiology of Covid-19 associated pneumonia. While some features of the disease (such as the oxygenation improvement associated with proning and/or continuous positive airway pressure) seem to line up with other causes of pneumonia characterized by primary alveolar damage, specific characteristics have been reported about Sars-CoV-2 lung infection which suggest a certain degree of parenchymal preservation and a predominant role of vascular impairment: the dissociation between lung volume and gas exchange, and the so called "happy hypoxemia" both evoke the possibility of mechanisms other than the loss of aeration as causes of hypoxia. Accordingly, evidence are now growing on the role of vascular dysregulation in this regard. It is probable, as previously put forward, that different stages exist in the disease which may account for the discordant findings of previous studies seeking to either associate or separate Covid-19 pneumonia and other causes of respiratory failure. In the present study we will compare the effects of three currently used approaches to improve gas exchange (continuous positive airway pressure, external oxygen administration and decubiti variations) in three different populations (1) early Covid-19 pneumonia, 2) severe late Covid-19 pneumonia and 3) non-Covid-19 pneumonia) in terms of breathing effort as assessed by esophageal pressure swings: our aim is to evaluate, in these populations, the real benefits (beyond the previously reported ones on gas exchange) of such strategies on lung rest. Our hypothesis is that, at least in the early stages of Covid-19 (and as opposed to other causes of respiratory failure), the application of positive pressure might be deleterious if no potential for recruitment, but rather a primary vascular impairment, is associated with hypoxia. If this will be the case the same (or a similar) degree of oxygenation improvement and a safer pattern of ventilation might be attained with the simple administration of oxygen or decubiti variations without the application of positive pressure, thus completely changing the current standards for the treatment of Covid-19 pneumonia.