Novel Endotracheal Tube for Monitoring Static Lung Compliance in Real Time

Background:Ventilated patients in ICUs are susceptible to alveolar barotrauma due to unrecognized alterations in lung compliance. In order to evaluate lung compliance accurately, clinicians must conduct inspiratory holds and prevent spontaneous inspiration to determine airway plateau pressure (PPlat) and static lung compliance (CS). Although monitoring CS is advised for optimal lung-protective ventilation strategies, it is rarely done due to the patient burden of inspiratory holds. We hypothesize that a novel endotracheal tube (ETT) with a distal airway pressure (PD) sensor that bypasses flow-dependent airway resistance can report PD equivalent to PPlat for the real-time monitoring of CS. Methods:The prototype ETT has an embedded PD sensor (MS5637-30BA) and was tested within an artificial trachea connected to a test lung. Control tests were conducted using a mechanical ventilator under volume control (VC) from 100-1000 mL tidal volumes (VT) with no mucus. To evaluate device performance, VC tests were conducted from a VT of 100-300 mL with varying levels of airway resistance/obstruction, which were simulated by distributing 5, 10, and 15 mL of 3% SentryTM POLYOXTM WSR Coagulant NF Grade synthetic mucus within the ETT. For each trial, the PD, peak inspiratory pressure (PIP), and PPlat were recorded, and the corresponding compliances were calculated. A t-test was performed on compliance averages from 100-200 mL VT with 10 mL and 15 mL mucus. Results:The trends between the obtained pressures during VC testing can be visualized in Fig. 1. Compliances calculated at a VT of 100-200 mL at varying mucus levels demonstrated no statistically significant differences between CS obtained from PD and PPlat (8.85 and 9.01 and 9.05 and 9.01 mL/cm H2O at 10 and 15 mL mucus, respectively), but showed statistically significant differences (p < 0.05) between these two values and compliances obtained from PIP (5.81 and 5. 12 mL/cm H2O at 10 and 15 mL mucus, respectively). Conclusions:During testing, differences in PD and PIP increased in correlation with mucus levels, while PD and PPlat differences remained similar (Fig. 1). At 10 and 15 mL of mucus, the PD peaked at PPlat with no statistically significant difference between the CS obtained from these readings, demonstrating that the device can accurately monitor PD as a surrogate for PPlat with no need for inspiratory pause. Therefore, this device allows for breath-to-breath evaluation of CS without interruption of mechanical ventilation.