Inverse Ratio Ventilation (IRV) is a subset of (Pressure-controlled ventilation)PCV in which inflation time is prolonged (In IRV, I:E ratio of 1:1, 2:1, or 3:1 may be used) A decrease in inspiratory flow rate is used to prolong the time for lung inflation. This lowers peak airway pressures but increases mean airway pressures. The prolonged inflation time can help prevent alveolar collapse.
However, prolonged inflation times also increase the tendency for inadequate emptying of the lungs, which can lead to hyperinflation and auto-PEEP. Drawback - The tendency to produce auto-PEEP can lead to a decrease in cardiac output Indication - patients with ARDS who have refractory hypoxemia during conventional modes of mechanical ventilation.
