Inductive plethysmography to control volume-targeted ventilation for leak compensation

Abstract

Volume-targeted ventilation is associated with poor compensation for leaks yet is frequently used in neuromuscular patients, many of whom experience mouth leaks. Our objective was to test the feasibility and efficacy of a prototype ventilator designed to achieve leak compensation by feed-back control of the actual tidal volume based on either the volume blown to the expiratory circuit (VTEVC-compensation) or the tidal volume measured by inductive plethysmography (VTplet-compensation). Randomized, cross-over, physiological study in a physiological ward of a university teaching hospital. Nine normal individuals. Subjects tested volume-targeted assist-control ventilation without compensation, with VTEVC-compensation, and with VTplet-compensation. Tests were done with the mouth closed, with mouth leaks during inspiration, and with mouth leaks during expiration. With inspiratory mouth leaks compared to mouth closed, the delivered volume remained unchanged without leak compensation, increased to 143 +/- 30% with VTEVC-compensation, and increased to 132 +/- 17% with VTplet-compensation; the expired tidal volume decreased to 46 +/- 24% without compensation, 66 +/- 20% with VTEVC-compensation, and 68 +/- 23% with VTplet-compensation. With expiratory mouth leaks, the ventilator-delivered volume and expired tidal volume were unchanged with no compensation and with VTplet-compensation; they increased with VTEVC-compensation. Leak compensation can be achieved during volume-targeted ventilation. VTEVC-compensation and VTplet-compensation were equally effective in compensating for inspiratory leaks, and VTplet-compensation also performed well when expiratory leaks occurred.