Background: This study aimed to evaluate the efficacy and reliability of maintaining a constant tidal volume (VT) using a square-wave flow pattern in currently available turbine-based ventilators (TBVs) compared with a bellows-based ventilator (BBV), under conditions of abrupt changes in ventilator load. Such changes frequently occur in ventilator-dependent patients during mouthpiece ventilation and sleep with a mask, including events such as air stacking (AS), leakage, disconnection for speaking or eating/drinking, and complete obstruction. Methods: Five TBVs and one BBV were assessed in a bench test simulating 4 distinct transient events (AS, leakage, disconnection, and complete obstruction) across 3 consecutive cycles. Results: During AS, only one TBV maintained VT as effectively as the BBV, whereas the others showed a significant decrease in VT when the elastic load increased because of the preceding stacked breath(s). During leakage, the same TBV again maintained VT as effectively as the BBV, both during and after the leak. In contrast, the other TBVs exhibited a transient increase in delivered VT at the onset of leakage, followed by a decrease once it ended. Except for the BBV, disconnection resulted in continuous air flow, with flow peaks occurring at the moments when VT was expected to be delivered. Following the termination of obstructive apnea, all devices maintained the targeted VT, except for one BBV, which delivered a VT above baseline during the 2 subsequent cycles. Conclusions: At least one BBV consistently maintained a stable VT under various conditions, including AS, leakage, postapnea recovery, and postdisconnection. However, disconnection was associated with continuous air flow in the TBVs, which could be disruptive during mouthpiece ventilation disconnection for speaking, eating, or drinking. This unintended effect warrants further investigation.
Delord et al. (Thu,) studied this question.