The BathRC model: a method to estimate flow restrictor size for dual ventilation of dissimilar patients

Andrew R Plummer; Jonathan l du Bois; Siu Man Lee; Patrick Magee; Jens Roesner; Harinderjit S Gill

• and I:E (inspiration to expiration time ratio). In PCV, the ventilator effectively controls the driving pressure to transition between PEEP and Pinsp+PEEP as quickly as possible at the required switching times; any limits or triggers which might alter this profile need to be disabled for dual patient use. 2. Silverknight 22mm breathing tube system (Intersurgical Ltd, Wokingham, UK, Figure 2 ) and Heat and Moisture Exchange (HME) filters (Clear-Therm 3, Intersurgical, Figure 3 ). 3. Non-return valves (Ref: 1950000, Intersurgical) -also known as one-way valves or check valves (Figures 2 and 3 ). As will be seen, these have a significant resistance and so have a notable effect of on the ventilation behaviour. 4. Two fixed test lungs (Test Lung 190, Siemens Healthineers, Erlangen, Germany) with different characteristics (Figures 2 and 3 ). 5. Two Fluke VT Plus HF Gas Flow Analysers (Fluke Biomedical, Everett, Washington, USA, Figure 3 ) 6. Flow restrictors. Two alternatives are used in the tests included here: a. A fixed restriction provided by an additional Intersurgical non-return valve of the same type as above. This has the benefit of medical approval. b. An adjustable flow restriction device of novel design, 3D-printed at the University of Bath ( Figure 4 ). Only results for the second of 5 discrete positions are shown in this paper.