284 - Does Leak Matter? A Novel Dynamic Leak Model to Simulate Leak for Performance Testing of Manual Neonatal Resuscitation Devices. A Bench Study

Publication Number: 284.4720

Stephanie Morakeas, University of Sydney and Westmead Hospital, Sydney, New South Wales, Australia; Mark B. Tracy, Westmead Hosptial NICU and the University of Sydney, Sydney, New South Wales, Australia; Murray Hinder, The University of Sydney, Westmead Children's Hospital, Leura, New South Wales, Australia; Viktoria Gruber, Medical University Graz, Department of Paediatrics and Adolescent Medicine, Division of Neonatology, Graz, Austria, Sydney, New South Wales, Australia; Alistair Mcewan, University Of Sydney, Sydney, New South Wales, Australia; Thomas Drevhammar, Karolinska Institutet, Stockholm, Stockholms Lan, Sweden

Background: Newborn resuscitation is commonly performed in the presence of face mask leak. Leak is highly variable, pressure-dependent and often unrecognised. The effectiveness of resuscitation devices to deliver adequate inflations in the presence of leak is unknown. Bench models simulating continuous leak have the disadvantage of not accurately reflecting leak occurring during clinical resuscitation. A dynamic leak model based on pressure-release valves was thus developed.

Objective: To assess self-inflating bag (SIB) and T-piece resuscitator (TPR) ventilation performance in the presence of dynamic (DLM) compared to continuous (CLM) leak models in a bench study.

Design/Methods: Five predefined leak levels were tested for each leak model (0-87%). Resuscitation devices were connected to a test lung (compliance 0.6 mL/cmH2O) and respiratory parameters were measured using respiratory function monitors before (patient interface) and after (actual) an induced leak at 40, 60, 80 inflations/min.

Results: 3,600 inflations were analysed. DLM showed a decrease in actual tidal volumes from 0%-87% leak with tidal volume differences (SIB 4.8mL, TPR 2.9mL), contrasting to minimal change for CLM (SIB -0.6mL, TPR 0.3mL) (Fig1 & Fig2). CLM demonstrated larger differences between patient interface and actual leak. The absolute difference at 60 inflations/min at 87% leak were SIB 37.5%, TPR 18.2% for CLM compared to SIB 4.6%, TPR 1.4% for DLM (Fig 3).

Conclusion(s): Continuous leak models may underestimate the impact of resuscitation device performance with poor correlation between patient interface and actual delivered volume. Dynamic leak models demonstrate several advantages with a more accurate representation of face mask leak and will prove useful in modelling all systems delivering PPV.

Figure 1
Figure 1: Mean actual respiratory parameters measured at the test lung (A) PIP, (B) PEEP, (C) Tidal volume for all manual resuscitation devices (Self-inflating bag (SIB) and t-piece resuscitator (TPR)), leak models (continuous leak model (CLM) and dynamic leak model (DLM)) and leak levels for an inflation rate of 60/min.

Figure 2
Figure 2: Expiratory tidal volume at the patient interface (Vte) versus the actual tidal volume (VtActual) for all rates, device and leak model combinations separated into model and device. Different colours represent the five different leak levels (0, 22, 46, 68, 87%).

Figure 3
Figure 3: Mean patient interface leak and actual leak for all manual resuscitation devices (Self-inflating bag (SIB) and t-piece resuscitator (TPR)), leak models (continuous leak model (CLM) and dynamic leak model (DLM) and leak levels for an inflation rate of 60/min.