During Proportional Assist Ventilation (PAV), the ventilator is servocontrolled throughout each spontaneous inspiration so that the airway pressure increases either in proportion to the airflow (resistive unloading), or inspired volume (elastic unloading), or both (combined unloading). To accomplish this, the ventilator utilizes a pneumotach (PT) signal as reference to generate the proportional airway pressure changes. In neonates, however, the PT may impose a significant dead space load and its signal may include a substantial endotracheal tube leak component. We investigated whether Respiratory Inductive Plethysmography (RIP) can replace pneumotachography as input signal to the ventilator during PAV. Spontaneously breathing animals were supported for 10-minute (normal lungs) or 20-minute periods (meconium injured lungs) by each of the three PAV modes. In each mode, three test periods were applied in random order with the ventilator servo-controlled either by the PT signal, the RIP abdominal band signal (AB), or the RIP sum signal of rib cage and AB (SUM). The gain of the servo was adjusted to achieve equal peak inspiratory pressures within each mode. Five piglets, five rabbits and five guinea pigs were studied to test different chest configurations and sizes. Minute ventilation and arterial blood gases were not significantly different between the three driving signals (ANOVA). Best airway pressure profiles were achieved with the raw abdominal signal alone, especially in the presence of chest wall distortion. We conclude that a RIP raw signal from a single abdominal band can be used to generate PAV avoiding dead space and endotracheal tube leak problems associated with pneumotachography.Table

Table 1
Full size table