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. 2020 Nov 16;15(11):e0242123.
doi: 10.1371/journal.pone.0242123. eCollection 2020.

A simple method to estimate flow restriction for dual ventilation of dissimilar patients: The BathRC model

Andrew R Plummer  1 , Jonathan L du Bois  1 , Joseph M Flynn  1 , Jens Roesner  1 , Siu Man Lee  2 , Patrick Magee  3 , Malcolm Thornton  2 , Andrew Padkin  2 , Harinderjit S Gill  1   4
Affiliations

A simple method to estimate flow restriction for dual ventilation of dissimilar patients: The BathRC model

Andrew R Plummer et al. PLoS One. .

Abstract

Background: With large numbers of COVID-19 patients requiring mechanical ventilation and ventilators possibly being in short supply, in extremis two patients may have to share one ventilator. Careful matching of patient ventilation requirements is necessary. However, good matching is difficult to achieve as lung characteristics can have a wide range and may vary over time. Adding flow restriction to the flow path between ventilator and patient gives the opportunity to control the airway pressure and hence flow and volume individually for each patient. This study aimed to create and validate a simple model for calculating required flow restriction.

Methods and findings: We created a simple linear resistance-compliance model, termed the BathRC model, of the ventilator tubing system and lung allowing direct calculation of the relationships between pressures, volumes, and required flow restriction. Experimental measurements were made for parameter determination and validation using a clinical ventilator connected to two test lungs. For validation, differing amounts of restriction were introduced into the ventilator circuit. The BathRC model was able to predict tidal lung volumes with a mean error of 4% (min:1.2%, max:9.3%).

Conclusion: We present a simple model validated model that can be used to estimate required flow restriction for dual patient ventilation. The BathRC model is freely available; this tool is provided to demonstrate that flow restriction can be readily estimated. Models and data are available at DOI 10.15125/BATH-00816.

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Conflict of interest statement

No conflict of interest. The support from BMI Bath Clinic does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Simple RC network model of ventilator system and patient, with linear resistance (Rv) and compliance (Cv) for the ventilator tubing system, and linear resistance (R) and compliance (C) for the patient.
The RC model calculates tidal volume as a function of variations in patient R and C values. It also gives the relationships between airway flow rate, q, airway pressure, pp, and ventilator pressure, p.
Fig 2
Fig 2. Ventilators circuits used for testing and validation.
HME = heat and moisture exchanger, VT+ HF = Fluke VT+ HF flow meter, INSP. = inspiration, EXP. = expiration.
Fig 3
Fig 3. Characterisation plots from testing data using Circuit 1.
a. is for the non-return valve, b is for the SOR device.
Fig 4
Fig 4. Plots of measured data, together with model prediction for the validation tests made using Circuit 3.
a. Test 1, b. Test 2, c. Test 3, d. Test 4, e. Test 5.
See this image and copyright information in PMC

References

    1. Neyman G, Irvin CB. A single ventilator for multiple simulated patients to meet disaster surge. Acad Emerg Med. 2006;13(11):1246–9. Epub 2006/08/04. 10.1197/j.aem.2006.05.009 - DOI - PMC - PubMed
    1. Paladino L, Silverberg M, Charchaflieh JG, Eason JK, Wright BJ, Palamidessi N, et al. Increasing ventilator surge capacity in disasters: ventilation of four adult-human-sized sheep on a single ventilator with a modified circuit. Resuscitation. 2008;77(1):121–6. Epub 2008/01/01. 10.1016/j.resuscitation.2007.10.016 - DOI - PubMed
    1. Joint Statement on Multiple Patients Per Ventilator. Anesthetic Patient Safety Foundation; 2020.
    1. Beitler JR, Kallet R, Kacmarek R, Branson R, Brodie D, Mittel AM, et al. Ventilator Sharing Protocol: Dual-Patient Ventilation with a Single Mechanical Ventilator for Use during Critical Ventilator Shortages Columbia University College of Physicians & Surgeons NY-PH; 2020.
    1. Tronstad C, Martinsen T, Olsen M, Rosseland LA, Pettersen FJ, Martinsen ØG, et al. Splitting one ventilator for multiple patients—a technical assessment. arXiv. 2020;arXiv:2003.12349

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