The Respiratory Physics and Mechanics of Flow-Controlled Ventilation

Abstract

Flow-controlled ventilation (FCV) represents a significant advancement in ventilatory support, focusing on the precise control of gas flow to optimize respiratory mechanics and improve patient outcomes. This ventilation strategy employs a constant flow of gas during the inspiratory phase, which differs fundamentally from traditional volume or pressure-controlled modes. The constant flow approach helps in achieving a more linear and predictable pressure-volume relationship, potentially reducing peak inspiratory pressures and the risk of ventilator-induced lung injury (VILI). The mechanics of FCV are centred around maintaining a steady flow, which facilitates uniform lung inflation and potentially enhances alveolar gas exchange. Additionally, FCV can incorporate mechanisms like flow-controlled expiration, which utilizes principles such as the Bernoulli effect to aid in active deflation, further optimizing the expiratory phase and improving CO<inf>2</inf> elimination. The physics underlying FCV involves a detailed understanding of fluid dynamics within the airways, where maintaining a constant flow can influence the distribution of ventilation and the mechanical power applied to the lung tissue. By reducing fluctuations in airway pressure and volume, FCV aims to minimize the mechanical stress on lung structures, thereby reducing the risk of VILI and improving overall respiratory system compliance.