Vibration-Based Detection for the Monitoring of bCPAP to Minimize Duration of Disconnections in the NICU

Introduction: Bubble-CPAP (bCPAP) is a minimally invasive respiratory support modality used to encourage lung development in neonates with respiratory distress syndrome. For a year, we carried out field research and worked with a team of NICU nurses (RN), respiratory therapists (RRT), and clinicians at the blinded institution’s hospital to identify the issues with the existing technology. In interviews with NICU personnel, we found that the bCPAP workflow requires high vigilance from nursing staff, as the movement of neonates causes frequent involuntary disconnections at the nasal interface. One RN described that disconnections at the nasal interface happened about 3 to 5 times per shift. To monitor for disconnections, NICU staff look for cessation of bubbling in the bCPAP water canister, which is checked every 3 to 4 hours by RRTs and every 2 to 4 hours by RNs. While bubbling in the canister is a direct indicator of bCPAP activity, it is difficult to monitor since both visible and audible bubbling signs might be obscured by nearby machinery and alarms. Thus, disconnections can go unnoticed for hours, decreasing the efficacy of the respiratory support and possibly leading to hypoxia. To minimize the time between the onset of disconnections to intervention, we propose a monitor to augment the existing Fisher & Paykel bCPAP system that immediately alerts NICU staff to the cessation of bubbling in the bCPAP water canister.

Materials and

Methods: Monitor Construction: Through a vibration-based bubbling monitor system, automated detection of bubbling status can assure staff that neonates are actively receiving respiratory support. The monitor system consists of two components: an accelerometer sensor that attaches to the bCPAP water canister to detect bubbling and a display system to process data from the accelerometer and showcase the bubbling status. Once a disconnection is detected, an alarm activates from the display system to alert the NICU staff.

Testing Model: We aimed to verify the detection sensitivity of the bCPAP monitor and determine a false alarm rate. A model bCPAP circuit was constructed from a Fisher & Paykel bCPAP, the preferred bCPAP system at the blinded institution’s hospital, and an airflow generator. Bubbling in the bCPAP system was initiated by occluding the nasal prongs, simulating insertion into the nares of a neonate. We tested the time it took for the monitor to alarm after a disconnection occurred by performing 10 trials at each system parameter, varying the airflow and pressure in clinically relevant ranges (5 to 10 L/min airflow, and 3 to 10 cmH2O pressure). To measure false alarms, the bCPAP system was allowed to bubble uninterrupted for 5 minutes, and the frequency of false alarms was recorded with 4 trials for each pressure level from 3 to 10 cmH2O, at a fixed airflow of 10 L/min. ANOVA was used for statistical analysis.

Results, Conclusions, and Discussions: The average time to alarm at each setting combination ranged between 3.59 and 4.91 seconds across trials. There is no statistically significant difference in the monitor’s time to alarm when varying the pressure or airflow rate across clinically relevant ranges. False alarms occurred only at pressures of 3 and 4 cmH20. These settings are not frequently used in the NICU, since recommended settings are between 5 to 8 cmH2O.

Preliminary verification results indicate that the monitor is effective in detecting the cessation of bubbling under recommended bCPAP operation conditions, in the pressure range of 5 to 10 cmH2O. Further trials are necessary to optimize the alarm delay time, and an increased trial duration is desired to determine false alarm rates and monitor function changes with continuous use of the monitor. In future work, we plan to investigate alarm fatigue and select an alarm modality that reduces sensory stress for NICU staff and neonates.

Our initial findings show that the vibration-based bCPAP monitor can accurately detect bCPAP disconnections. This device can improve the quality of care for neonates receiving bCPAP therapy by reducing the time to intervention after a disconnection event. Improving the continuity of respiratory support may result in a faster recovery for neonates and may reduce the need to escalate to more invasive forms of respiratory support due to desaturation events.

Acknowledgements (Optional):