Experimental validation of a portable tidal volume indicator for bag valve mask ventilation

Benjamin S Maxey; Luke A White; Giovanni F Solitro; Steven A Conrad; J Steven Alexander

doi:10.1186/s42490-022-00066-y

Experimental validation of a portable tidal volume indicator for bag valve mask ventilation

BMC Biomed Eng. 2022 Nov 17;4(1):9. doi: 10.1186/s42490-022-00066-y.

Authors

Benjamin S Maxey^#¹, Luke A White^#¹, Giovanni F Solitro², Steven A Conrad^{3

4

5}, J Steven Alexander^{6

7

8}

Affiliations

¹ Department of Molecular & Cellular Physiology, LSU Health Shreveport, 1501 Kings Highway, Shreveport, LA, 71103-3932, USA.
² Department of Orthopaedic Surgery, LSU Health Shreveport, Shreveport, LA, USA.
³ Department of Medicine, LSU Health Shreveport, Shreveport, LA, USA.
⁴ Department of Emergency Medicine, LSU Health Shreveport, Shreveport, LA, USA.
⁵ Department of Pediatrics, LSU Health Shreveport, Shreveport, LA, USA.
⁶ Department of Molecular & Cellular Physiology, LSU Health Shreveport, 1501 Kings Highway, Shreveport, LA, 71103-3932, USA. jonathan.alexander@lsuhs.edu.
⁷ Department of Medicine, LSU Health Shreveport, Shreveport, LA, USA. jonathan.alexander@lsuhs.edu.
⁸ Department of Neurology, LSU Health Shreveport, Shreveport, LA, USA. jonathan.alexander@lsuhs.edu.

^# Contributed equally.

Abstract

Introduction: Short-term emergency ventilation is most typically accomplished through bag valve mask (BVM) techniques. BVMs like the AMBU^® bag are cost-effective and highly portable but are also highly prone to user error, especially in high-stress emergent situations. Inaccurate and inappropriate ventilation has the potential to inflict great injury to patients through hyper- and hypoventilation. Here, we present the BVM Emergency Narration-Guided Instrument (BENGI) - a tidal volume feedback monitoring device that provides instantaneous visual and audio feedback on delivered tidal volumes, respiratory rates, and inspiratory/expiratory times. Providing feedback on the depth and regularity of respirations enables providers to deliver more consistent and accurate tidal volumes and rates. We describe the design, assembly, and validation of the BENGI as a practical tool to reduce manual ventilation-induced lung injury.

Methods: The prototype BENGI was assembled with custom 3D-printed housing and commercially available electronic components. A mass flow sensor in the central channel of the device measures air flow, which is used to calculate tidal volume. Tidal volumes are displayed via an LED ring affixed to the top of the BENGI. Additional feedback is provided through a speaker in the device. Central processing is accomplished through an Arduino microcontroller. Validation of the BENGI was accomplished using benchtop simulation with a clinical ventilator, BVM, and manikin test lung. Known respiratory quantities were delivered by the ventilator which were then compared to measurements from the BENGI to validate the accuracy of flow measurements, tidal volume calculations, and audio cue triggers.

Results: BENGI tidal volume measurements were found to lie within 4% of true delivered tidal volume values (95% CI of 0.53 to 3.7%) when breaths were delivered with 1-s inspiratory times, with similar performance for breaths delivered with 0.5-s inspiratory times (95% CI of 1.1 to 6.7%) and 2-s inspiratory times (95% CI of -1.1 to 2.3%). Audio cues "Bag faster" (1.84 to 2.03 s), "Bag slower" (0.35 to 0.41 s), and "Leak detected" (43 to 50%) were triggered close to target trigger values (2.00 s, 0.50 s, and 50%, respectively) across varying tidal volumes.

Conclusions: The BENGI achieved its proposed goals of accurately measuring and reporting tidal volumes delivered through BVM systems, providing immediate feedback on the quality of respiratory performance through audio and visual cues. The BENGI has the potential to reduce manual ventilation-induced lung injury and improve patient outcomes by providing accurate feedback on ventilatory parameters.

Keywords: Bag valve mask; Emergency; Low-cost; Lung; Manual ventilation; Monitor; Tidal volume; Ventilation.