Effect of Different Measurements of End-inspiratory Airway Pressure on Driving Pressure and Mechanical Power in Mechanically Ventilated Patients: the P1-P2 Decay Study

Detailed Summary

Mechanical ventilation may be associated with ventilator-induced lung injury (VILI). Several respiratory variables have been employed to estimate the risk of VILI, such as tidal volumes, plateau pressure, driving pressure, and mechanical power. This dissipation of energy during ventilation can contribute to VILI through two mechanisms, stress relaxation and pendelluft, which can be estimated at the bedside by applying an end-inspiratory pause and evaluating the slow decrease in airway pressure going from the pressure corresponding to zero flow (called pressure P1) and the final pressure at the end of the pause (called plateau pressure P2). The choice of measuring the end-inspiratory airway pressure (PawEND-INSP) at a fixed, although relatively early, timepoint, i.e., after 0.5 second from the beginning of the pause, as prescribed by the indications of the Acute Respiratory Distress Syndrome (ARDS) Network, while assessing the risk of VILI associated with the elastic pressure of the respiratory system, may not reflect the harmful potential associated with the viscoelastic properties of the respiratory system. It is still unclear whether an PawEND-INSP measured at the exact moment of zero flow (P1) is more reliable in the calculation of those variables, such as ΔP and MP, associated with the outcomes of patients with and without ARDS, as compared to the pressure measured at the end of the end-inspiratory pause (plateau pressure P2). This multicenter prospective observational study aims to evaluate whether the use of P1, as compared to P2, affects the calculation of ΔP and MP. The secondary objectives are: 1) verify whether in patients with a lung parenchyma characterized by greater parenchymal heterogeneity, as assessed by EIT, P1-P2 decay is greater than in patients with greater parenchymal homogeneity; 2) evaluate whether patients with both ΔP values calculated using P1 and P2 \<15 cmH2O (or both MP values calculated using P1 and P2 \<17 J/min) develop shorter duration of invasive mechanical ventilation, shorter ICU and hospital length of stay and lower ICU and hospital mortality, as compared to patients with only ΔP calculated with P1 ≥ 15 cmH2O (or only MP calculated with P1 ≥ 17 J/min) and patients with both ΔP values calculated using P1 and P2 ≥ 15 cmH2O (or both MP values calculated using P1 and P2 ≥ 17 J/min).

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