Inductance plethysmography: An alternative signal to servocontrol the airway pressure during proportional assist ventilation in small animals

During proportional assist ventilation (PAV), the ventilator pressure is se rvocontrolled throughout each spontaneous inspiration such that it instanta neously increases in proportion to the airflow (resistive unloading mode), or inspired volume (resistive unloading mode), or both (combined unloading mode). The PAV pressure changes are generated in a closed-loop feedback cir cuitry commonly using a pneumotachographic signal. In neonates, however, a pneumotachograph increases dead space ventilation, and its signal may inclu de a substantial endotracheal tube leak component. We hypothesized that res piratory inductive during proportional assist ventilation (PAV), the ventil ator pressure is servocontrolled throughout each spontaneous inspiration su ch that it instantaneously increases in proportion to the airflow (resistiv e unloading mode), or inspired volume (elastic unloading mode), or both (co mbined unloading mode). The PAV pressure changes are generated in a closed- loop feedback circuitry commonly using a pneumotachographic signal. In neon ates, however, a pneumotachograph increases dead space ventilation, and its signal may include a substantial endotracheal tube leak component. We hypo thesized that respiratory inductive plethysmography (RIP) can replace pneum otachography to drive the ventilator during PAV without untoward effects on ventilation or respiratory gas exchange. Ten piglets and five rabbits were supported for 10-min (normal lungs) or 20-min (meconium injured lungs) per iods by each of the three PAV modes. In each mode, three test periods were applied in random order with the ventilator driven by the pneumotachograph signal, or the RIP abdominal band signal, or the RIP sum signal of rib cage and abdomen. Interchanging the three input signals did not affect the plet hysmography (RIP) can replace pneumotachography to drive the ventilator dur ing PAV without untoward effects on ventilation or respiratory gas exchange . Ten piglets and five rabbits were supported for 10-min (normal lungs) or 20-min (meconium injured lungs) periods by each of the three PAV modes. In each mode, three test periods were applied in random order with the ventila tor driven by the pneumotachograph signal, or the RIP abdominal band signal , or the RIP sum signal of rib cage and abdomen. Interchanging the three in put signals did not affect the regularity of spontaneous breathing, and gas exchange was achieved with similar peak and mean airway pressures (ANOVA). However, the RIP sum signal worked adequately only when the relative gains of rib cage and abdominal band signal were calibrated. We conclude that an RIP abdominal band signal can be used to generate PAV, avoiding increased dead space and endotracheal tube leak problems.