A new expiratory support system for resolving air trapping in lungs during mechanical ventilation: A lung model study

Abstract

The aim of the study was to assess a new expiratory support (ES) system in resolving air trapping in the lungs during mechanical ventilation. The ES system consisted of a cylinder and two valves that were connected to the ventilatory circuit. The movements of them were synchronized with the ventilator. The cylinder aspirated gas during expiration. We compared the effects of the ES on air trapping between a narrower and an ordinary size endotracheal tube (ETT) (internal diameter (ID): 5 and 8 mm). In addition, we compared the effects of the ES on air trapping between normal and high airway resistance of the lungs (5 and 20 cm H₂O/L/s). The ventilatory settings were as follows: volume controlled ventilation with constant inspiratory flow rate; tidal volume, 0.5 L; inspiratory time, 1.0 s; expiratory time, 1.0, 1.5, or 2.0 s; and PEEP, 0 cm H₂O. The ES normalized the end-expiratory alveolar pressure of the 5 mm ID ETT at a level similar to that of the 8 mm ID ETT. The ES also resolved the air trapping induced by the high airway resistance of the lungs. In conclusion, the ES system resolved the air trapping associated with a narrow endotracheal tube and high airway resistance of the lungs.