Flow-controlled ventilation decreases mechanical power in postoperative ICU patients

Abstract

Background: Mechanical power (MP) is the energy delivered by the ventilator to the respiratory system and combines factors related to the development of ventilator-induced lung injury (VILI). Flow-controlled ventilation (FCV) is a new ventilation mode using a constant low flow during both inspiration and expiration, which is hypothesized to lower the MP and to improve ventilation homogeneity. Data demonstrating these effects are scarce, since previous studies comparing FCV with conventional controlled ventilation modes in ICU patients suffer from important methodological concerns. Objectives: This study aims to assess the difference in MP between FCV and pressure-controlled ventilation (PCV). Secondary aims were to explore the effect of FCV in terms of minute volume, ventilation distribution and homogeneity, and gas exchange. Methods: This is a physiological study in post-cardiothoracic surgery patients requiring mechanical ventilation in the ICU. During PCV at baseline and 90 min of FCV, intratracheal pressure, airway flow and electrical impedance tomography (EIT) were measured continuously, and hemodynamics and venous and arterial blood gases were obtained repeatedly. Pressure–volume loops were constructed for the calculation of the MP. Results: In 10 patients, optimized FCV versus PCV resulted in a lower MP (7.7 vs. 11.0 J/min; p = 0.004). Although FCV did not increase overall ventilation homogeneity, it did lead to an improved ventilation of the dependent lung regions. A stable gas exchange at lower minute volumes was obtained. Conclusions: FCV resulted in a lower MP and improved ventilation of the dependent lung regions in post-cardiothoracic surgery patients on the ICU. Trial registration Clinicaltrials.gov identifier: NCT05644418. Registered 1 December 2022, retrospectively registered.