PIP Variances While Ventilating With a Single Limb Ventilator

Abstract

Background:

Bench testing with a single limb circuit vent was needed to evaluate the accuracy of PIP delivery in the adult and pediatric mode. The Ingram ASL 5000 breathing simulator was used to simulate a pediatric patient, connected with a 4.0 mm endotracheal tube and to the EV300 vent. Using the adult mode will allow us to transition more patients to a single limb vent but we wanted to establish the safety and accuracy of using that mode.

Methods:

Testing began using the ASL5000 to simulate a pediatric patient, connected with a 3.0, 3.5, 4.0, 4.5, and 5.5-mm trach tube to the EV300 vent. The simulated ped model used on the ASL was a BPD patient, neuromuscular patient and healthy lung model. We completed testing in all three patient models. The settings used for testing ranged from a PC 10–20 and a PEEP ranging from 5-15.

Results:

While using a simulated patient, in the absence of any other changes except switching the patient category from adult to ped reduces the delivered PIP and delivers lower V_Ts. The EV300 did not display the delivery volume and PIP displayed on the ASL. The pressure and V_Te differences were more pronounced in the NM model than the BPD. The differences were more pronounced with the smaller trachs. The measured leak seemed to be much more affected by PEEP changes than PC changes but the V_Te accuracy seems to be affected by PC changes. As expected an airway leak decreases reliability the same way as the pressure differential was found first with the BPD model. We repeated our testing with a neuromuscular patient model. Pressure and V_Te difference for each set of data including the trach size and settings with each graph.

Conclusions:

The differences in PIPs and V_Te were more pronounced with the smaller trachs. We suspect that the pressure differences are related to flow throttling with the narrowing of the airway combined with the single limb flow pattern. The measured leak seems to be much more affected by PEEP changes than PC changes but the V_Te accuracy seems to be much more affected by PC changes. We suspect the leak compensation is able to work well for the consistent leak from the PEEP but that it struggles with the quick changes during a breath. We think it's helpful to know that trach size and PC both have an effect on the accuracy of the EV300.When transitioning to a home care vent we need to take the PC/trach into consideration when transitioning to the EV300. Also, knowing that EV300 is not always delivering the pressures it reports might give us a lower threshold for increasing settings for patients struggling with vent transitions.