4DPRR- Index for predicting mortality in COVID-19 ARDS

Abstract Background Mortality in ARDS was reduced significantly after the introduction of the low tidal volume ventilation strategy. It has been recently shown that lung-protective ventilation strategies should primarily target driving pressure rather than Vt and that ventilator induced lung injury is not just dependent on tidal volume but also other factors like respiratory rate and driving pressure. Ventilator induced lung injury is also thought to be dependent on the amount of energy transferred by the ventilator to the patient which in turn is dependent on tidal volume size (VT), plateau pressure (Pplat), respiratory rate (RR). Mechanical power can be calculated accurately through power equations which can increase their applicability in clinical practice. One simple composite equation (driving pressure multiplied by four plus respiratory rate [4DPRR]) has been recently suggested as a simple surrogate for the power equation. This equation also doesn’t include PEEP as it has been theorized that it is the only elastic dynamic component of driving energy which affects the outcome and not the elastic static component (i.e., PEEP) and the resistive power (related to flow and airway resistance). Objectives To assess the mechanical power as measured by 4DPRR in mechanically ventilated patients who have moderate to severe COVID-19 ARDS. Methods: We obtained data on ventilatory variables and mechanical power from the patients who were admitted with moderate to severe COVID ARDS in our hospital from March 2021 to June 2021. Results We included 34 patients (28% women; mean age, 57 ± 17 yrs.). The average ΔP was 21.44 ± 3.98 cmH2O, the RR was 23.8 ± 3.84 breaths/min, and the mean driving pressure was 21.4 cmH2O. 28% (n = 10) of patients expired. There was no significant association of 4DPRR (P 0.72), Pplat (P 0.79).and RR (P 0.21) with mortality as predicted by area under ROC curves. Conclusions Driving power and plateau pressure were associated with mortality during controlled mechanical ventilation in COVID ARDS, but a simpler model of mechanical power using only the driving pressure and respiratory rate was found to be a poor predictor of mortality. Keywords: COVID-19, ARDS, Mechanical power, Driving pressure, Plateau pressure