Effect of the Y-piece of the ventilation circuit on ventilation requirements in extremely low birth weight infants

Abstract

Volutrauma caused by high tidal volumes contributes considerably to the development of bronchopulmonary dysplasia. Yet high tidal volumes are required to overcome dead space. In an experimental arrangement we tested whether reduction of dead space might reduce ventilation requirements and thus reduce volutrauma in preterm infants. The time required to eliminate CO2 by standardized mechanical ventilation from a preterm infant's test lung flooded with CO2 was measured. Four different Y-pieces and flow sensor combinations were tested with and without a device for closed suction: Y-piece without flow sensor; integrated flow sensor; small dead-space flow sensor; and a new dead-space free-flow sensor for preterm infants. CO2 concentrations were measured by a capnograph. Mean CO2 elimination times (+/-SD) were compared. Mean CO2 elimination time was 37.5 s (+/-1.18 s) with and 37.4 s (+/-0.97 s) without closed suction device for the Y-piece without flow sensor, 47.7 s (+/-0.82 s) and 45.5 s (+/-1.18 s) for the integrated flow sensor, 42.5 s (+/-1.27 s) and 41.1 s (+/-0.99 s) for the small dead-space flow sensor and 38.3 s (+/-1.16 s) and 36.8 s (+/-0.79 s) for the dead-space free-flow sensor. CO2 elimination time with and without closed suction device was nearly identical for the Y-piece without flow sensor and for the dead-space free-flow sensor. With both systems, ventilation requirements were significantly lower than for the integrated flow sensor and for the small dead-space flow sensor (integrated flow sensor vs dead-space free-flow sensor 23.6 and 24.5%, respectively, small dead-space flow sensor vs dead-space free flow sensor 11.7 and 10.9%, respectively); thus, we think that introduction of the innovative dead-space free-flow sensor into clinical practice might reduce incidence and severity of bronchopulmonary dysplasia by reduction of volutrauma.