Driving pressure (ΔP = plateau pressure [Pplat] minus positive endexpiratory pressure [PEEP]) has generated increasing interest in recent years since it is considered the measure that best stratifies mortality risk in critically ill adults with acute respiratory distress syndrome (ARDS) (1). Consequently, ΔP is a potential predictor of ventilator-induced lung injury and a possible target to define the safety limits of mechanical ventilation (2, 3). In children, similar results have recently been published: Díaz et al (4) reported that ΔP is the formula that best discriminated patients with pediatric ARDS (PARDS) from those without, and van Schelven et al (5) showed that ΔP was independently associated with increased time to extubation.Pplat measurement is performed in adults in the static condition when gasflow reaches zero using the volume-controlled mode (1). Contrasting with adult critical care, pressure controlled modes with decelerating flow are predominantly used in the PICU (6), and peak inspiratory pressure (PIP) is used in some studies to estimate Pplat in PARDS for ΔP calculation (7-9). In this issue of Pediatric Critical Care Medicine, Patel et al (10) address a knowledge gap in the reliability of Pplat estimation using PIP in pressure controlled mode. The authors show that in a cohort of 52 patients with PARDS (median age of 8.6 yr old [3.2-16.0 yr old]), PIP was close to Pplat measured in the static condition, that is, PIP was 1.0 ± 0.6 cm H 2 O above Pplat (95% limits of agreement of -0.3 to 2.2). Therefore, Patel et al (10) concluded that PIP measured during decelerating flow ventilation may be an adequate surrogate of Pplat in PARDS when inspiratory flow approaches zero.This new study by Patel et al ( 10) is well designed, including a cohort of PARDS children with an oxygenation index of 15.7 (9.0-21.0) and bilateral infiltrates on chest radiograph. In such a cohort, inspiratory airway resistance (Raw) is most likely low, which is the ideal condition for a zero flow plateau at the end of inspiratory time. Indeed, the inspiratory time constant (τ) in such circumstances is estimated to be 0.04 seconds. That is, since τ = respiratory system compliance × Raw, which is the same as this equation: (Vt [mL/kg] × weight [kg])/(Plat-PEEP) (cm H 2 O) × R (cm H 2 O/L / s) (11). τ is arrived at by using median tidal volume = 6.4 mL/kg, mean body weight = 27 kg at 8.6 years old (12), Pplat = 29.5 cm H 2 O, PEEP = 12 cm H 2 O (see article Supplemental Table in reference [10]), normal inspiratory resistance = 4 cm H 2 O/L / s (13). As zero flow is obtained at five time constants (≈ 0.2 s) (11), an inspiratory time set at more than 0.8 seconds (see the Supplemental Table in reference [10])

As pediatricians, we all have to deal with new childhood inflammatory disorder due to COVID 19: the Multisystem Inflammatory Syndrome in Children (MIS-C). The recent article by Savorgnan et al. on the physiologic profiles associated with MIS-C proposed a classification through the “MIS-C severity score” (MSS). The authors also identified a combination of seven variables collected during the first 3 h of admission in the PICU that contributes to stratify MIS-C severity with an area under the receiver operating characteristic curve (AUC) >0.90. This work represents an important first step in the development of a MIS-C severity score and is a call for collaborative groups to validate the prediction model through multicenter studies and thereby refine the management of MIS-C. Impact The recent article by Savorgnan et al. on physiologic profile associated with MIS-C represents an important first step in the development of an MIS-C severity score and is a call for collaborative groups to validate the prediction model through multicenter studies and thereby refine the management of MIS-C. Our manuscript helps in the methodology interpretation of the manuscript by Savorgnan et al. And our manuscript promotes collaborative work on MIS-C.