The benefits of Tracheal Gas Insufflation (TGI) as an adjunct to mechanical ventilation are well known. 1 TGI reduces dead space and CO2 rebreathing in mechanically ventilated patients, thereby reducing PaCO2 with no change in minute ventilation, or maintaining PaCO2 with 10-20% reductions in minute ventilation.2 These improvements in ventilation efficiency are beneficial in avoiding or reducing the volutrauma associated with Acute Respiratory Distress Syndrome (ARDS). 3 Unfortunately, therapists are reluctant to adopt TGI as a conventional lung protection strategy. Reluctance to adopt TGI as a routine protocol is due primarily to the complexity and confusion surrounding its safe use, and to the lack of a simple and reliable patient interface.4 This study will define the feasibility of an integrated and easy-to-use patient interface system designed to improve the safety, ergonomics, compliance, ease of use, and costs associated with TGI. A simple add-on circuit will be designed to flush exhaled CO2 from the dead-space of conventional breathing circuits and thereby reduce the risk of morbidity typically associated with the misuse of complex self-made devices in clinical settings. Prototypes of the integrated TGI patient interface circuit will be designed, fabricated, and tested for performance and potential injury using a novel lung and trachea simulator. Design improvements will address issues identified by the FDA CDRH Anesthesiology Guidance Panel, December 1998.5 Safety features will include 1) a means to prevent over pressurization and barotrauma, 2) a simple means to provide heated and humidified flush gas, and 3) a means to safely integrate the multitude of pneumotachometer conduits, sensors, insufflations catheter, and gas humidifier with the patient breathing circuit and tracheal tube in an ergonomically effective package. Input requirements will be identified before the initiation of system design. Bench studies with the novel lung and tracheal model will verify design compliance to the input requirements and potentially reduce the number of future animal and human clinical studies needed to validate compliance to these requirements. This Phase I work will help justify a Phase II IDE clinical protocol with IRB approval for human-use clinical studies in the future. Development of this advanced TGI system will potentially lead to routine clinical use to help reduce or prevent the lung injury associated with mechanical ventilation and ARDS.
