Prior studies examining the prognostic value of V D/V T have had limitations that prevent the generalizability of their results to subjects eligible for therapeutic clinical trials, including the fact that subjects were studied at only 1 or 2 hospitals. 5, 6Ī pulmonary-specific physiologic variable such as V D/V T, which is strongly associated with mortality, could be useful in assessing the efficacy of new therapies for ARDS in prospective clinical trials. 2– 8 Moreover, sustained elevation of V D/V T in ARDS has been associated with higher mortality. 1 However, newer evidence indicates that V D/V T is markedly elevated within 24 h of ARDS onset and is significantly elevated in non-survivors.

Historically, elevated V D/V T in patients with ARDS was thought to be a late-occurring phenomenon associated with the fibroproliferative stage of injury. Physiologic dead-space fraction (ratio of dead space to tidal volume ) is the portion of tidal volume that does not participate in gas exchange and therefore consists of expired gas without carbon dioxide. Over the past two decades, there has been increasing interest in dead space since the publication by Nuckton et al. Dead space ventilation-related indices remain hampered by several deflects notwithstanding, for this catastrophic syndrome, they may facilitate better stratifications and identifications of subphenotypes, thereby providing therapy tailored to individual needs.Ī hallmark of classical ARDS is an increased shunt caused by alveolar collapse and/or alveolar flooding from a physiological viewpoint.

These parameters have already been applied to positive end expiratory pressure titration, prediction of responses to the prone position and the field of extracorporeal life support for patients suffering from ARDS. Thus, new attention has been given to this group of dead space ventilation-related indices, such as physiological dead space fraction, ventilatory ratio, and end-tidal-to-arterial PCO 2 ratio, which, albeit distinctive, are all global indices with which to assess the relationship between ventilation and perfusion. Cumulative evidence has demonstrated that the ventilatory ratio closely correlates with mortality in acute respiratory distress syndrome (ARDS), and a primary feature in coronavirus disease 2019 (COVID-19)-ARDS is increased dead space that has been reported recently.

Physiologic dead space ratio