Comparison of Oxygenation Index and Oxygen Stretch Index

Pediatric acute respiratory distress syndrome (pARDS) is a heterogeneous clinical syndrome that causes high rates of mortality and morbidity. The Pediatric Acute Lung Injury Consensus Conference (PALICC) guideline recommends using the oxygenation index (OI = mean airway pressure (MAP) × FiO2 /PaO2) for the diagnosis and classification of pediatric ARDS. In recent years, studies conducted on adult and pediatric populations have emphasized ''driving pressure'' as the most important ventilator parameter associated with mortality. Driving pressure (DP) is calculated by subtracting PEEP from plateau pressure. It is an important determinant of tidal volume in each breath and indirectly reflects lung stress. Lung stress is directly measured with transpulmonary pressure (PL).

Mechanical power (MP) is the amount of energy applied to patients per unit time and its relationship with lung injury has been shown in adult and pediatric studies. Another method that shows lung damage is measured noninvasively at the patient's bedside. It has been validated in many adult, pediatric, and neonatal studies. In an adult study, DP was used instead of MAP inspired by the oxygenation index and defined as the Oxygenation stretch index. It was emphasized that it can better predict oxygenation and mortality.

OI is not used in the ARDS classification in adults. Adding airway pressure to the oxygenation equation is very important to standardize the severity of the disease. However, its effect on patient outcomes has not been determined as much as mean airway pressure, plateau, and driving pressure. In addition, no target recommendation has been presented in the PALICC guidelines. Plateau pressure is the end-inspiratory pressure and does not have a direct effect on PEEP. Since ventilator management is still heterogeneous in pediatric literature in line with the guidelines, it seems more logical to use driving pressure, which includes both inspiratory pressure and expiratory pressure. Within the framework of this information, adding driving pressure to the formula instead of Pmean (MAP) in the oxygenation index may be useful in evaluating both the severity of pARDS and the effectiveness of respiratory dynamics.

In our study, we will compare the Oxygenation Stretch Index with OI in patients with pARDS. We will examine its effects on parameters indicating lung damage, respiratory mechanics and patient outcomes.