O3309: In Vitro and In Vivo Analysis of a Novel Field-Expedient Bubble BiPAP

Background: Respiratory distress syndrome is a leading cause of death among infants born prematurely in low-income countries. A major contributing factor is a lack of access to noninvasive respiratory support devices. Although designs for low-cost bubble continuous positive airway pressure (CPAP) devices have been published for use in resource-limited settings, there exists a need for a low-cost bubble bilevel positive airway pressure (BiPAP) device that could sustain neonates who require additional ventilatory support. Our objective is to evaluate the ability of a novel low-cost bubble BiPAP device to deliver specific respiratory parameters both in vitro and in vivo in a piglet model.

Methods: A bubble BiPAP was constructed using a modified RAM (Neotech) nasal cannula, extension tubing, microcontroller, servo motor, stick, bucket of water, and foam tape. A simulated nasopharynx was constructed with a defined nare size and nasopharyngeal volume. Intrapharyngeal pressures were measured with every 0.1 s during operation of the device at pressures of 20/10 cmH2O. Performance of the bubble BiPAP was compared to a standard RAM cannula driven by a modern hospital ventilator in nasal intermittent positive pressure ventilation (NIPPV) mode. After ensuring the device could meet targets in vitro, a pilot study was performed in 2 anesthetized 8 kg piglets. Venous blood gases, continuous pulse oximetry, and end-tidal capnography values were recorded every 5-10 min, and pressure at the nares was recorded continuously.

Results: The bubble BiPAP outperformed RAM NIPPV in vitro in reaching goal pressure values of 20/10 cmH2O (iTime 1 s, RR 30 breaths/min) when measured within the nasopharynx and this difference was more profound as leak increased (appropriate leak, mean pressures 15.1 vs 13.1, p< 0.001; larger leak, 12.4 vs 7.5, p< 0.001; major leak, 5.6 vs 1.8, p< 0.001). During the in vivo evaluation, the bubble BiPAP functioned reliably over 90 min without pause. The most effective bubble BiPAP parameters in vivo were set pressures of 20/10 cmH20, RR 30, and iTime of 1 s; however, the piglet slowly became more hypercarbic over a 45-min period with ETCO2 increasing from 59-66 mmHg with a rate of rise (RoR) of 0.15 mmHg/min. In contrast, on bubble CPAP, ETCO2 levels increased from 35-59 mmHg after 4 min with a RoR of 6 mmHg/min. ETCO2 values correlated well with blood gas pCO2 levels (Pearson r=0.97, p< 0.001).

Conclusion: The novel bubble BiPAP consistently delivered bilevel pressures at the nares close to goal parameters and functioned reliably in a piglet model. Although the bubble BiPAP ventilated a piglet in vivo, the inability to reduce CO2 levels may be due to the piglets having larger tidal volumes than the device was originally intended for and/or the piglets’ anesthetized state.