Differential Multiventilation

As stated in the section introducing our stainless-steel splitter, adding splitters to the breathing circuits of existing ventilators is the most rudimentary way of achieving multiventilation, but in this way, all systems to monitor and control the parameters for each different patient in the circuit are lost. 

 

Adding specific components to the splitters allows to overcome the issues mentioned and is called differential multiventilation. This document summarizes state-of-the-art findings from the main researches in the field and from the Differential Multiventilation International Working Group. It briefly covers how to implement multiventilation in the safest and most effective way and gives an example that we developed based on our stainless-steel splitter. It is important to note that even assuming the improvements listed below, multiventilation remains by no means anything else than a last resort solution. 

Basic hypotheses 

This individualized split ventilation requires additional components to increase the safety, monitoring and control for each patient. The required approach in designing the complete setup is to keep it simple, especially by excluding electronics, choosing minimal equipment, cheap, readily available or easily manufactured in remote areas. The cost and shortage risks of supplies are important considerations in designing the setup. In terms of functionality, the basic principle is that the final setup should allow multiple-patient ventilation in a way that each patient should have no effect on the ventilation of other patients attached to the ventilator.  

Ventilator settings 

Pressure-cycled mode is preferred to volume-cycled ventilation, in part because it allows to choose pairs of patients that do not have to have a similar size. More information about the best control settings in differential multiventilation are very-well described on [1] and [2], also describing potential ventilation-related pathologies.  

Components required to build a basic setup 

As stated above, the components will be chosen to build a prototype that will allow to control individual patient respiratory parameters (inspiratory volume, FiO2, PEEP pressure), decreasing inter-patient dependency and allow to redress for compliance mismatch between lungs. 

 

The following components must be integrated to the setup and connected according to the scheme below: 

 

  • 2 splitters for 2 patients, placed on the inspiratory and expiratory circuits (6 splitters for 4 patients); 

  • 1 one-way valve per patient, placed on the expiratory and/or inspiratory circuits; 

  • 1 flow control valve per patient on the inspiratory circuit; 

  • 1 flow meter to control the FiO2 on the inspiratory circuit; 

  • 2 filters per patient, one on the inspiratory circuit (just after the splitter) and one at the end of the expiratory circuit; 

  • 1 PEEP valve per patient on the expiratory; 

  • Optional: 1 capnogram per patient, can be connected on the filter added on the expiratory circuit; 

  • Optional: 1 pressure transducer per patient. 

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Which components to choose 

Proposed components are readily available in hospitals, can be bought in medical supply or plumbing stores. Many emerging initiative propose open-source 3D printed components as a back-up plan.

If you need more information, initiatives were listed here

Which patients to group 

The patients don’t need to be the same size, but ideally, they should have roughly similar severity of lung injury (e.g. similar PEEP and FiO2 requirements). Grouping of patients therefore depends on the presence or absence of underlying pulmonary disease.  

We built a differential multiventilation set up on the basis of our splitters, see figure below. 

The setup has successfully been tested at CHC Heusy (Verviers, Beligum).  

  • Valves chez Vanmarc 

  • PEEP valves Assertys; 

  • Flow-meters; 

  • Filters available at the hospital, integrating capnogram connexion. 

 

Proposition of a complete multiventilation prototype based on our stainless steel splitter

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Example : role of a valve 

References : 

[1] A better way of connecting multiple patients to a single ventilator. Hannah Pinson. 26 March 2020. [Accessed 09 April 2020]

Available at URL : https://medium.com/@pinsonhannah/a-better-way-of-connecting-multiple-patients-to-a-single-ventilator-fa9cf42679c6 

 

[2] Joshua D. Farkas. PulmCrit – Splitting ventilators to provide titrated support to a large group of patients. March 15, 2020 

Available at URL : https://emcrit.org/pulmcrit/split-ventilators/ 

 

[3] Shared ventilation: how to do it if you have to.  Simran Kaur Matta, MD. [Accessed 08 March 2020]

Available at URL: https://litfl.com/shared-ventilation-how-to-do-it-if-you-have-to/ 

 

[4] Farkas J. PulmCrit wee – Why the SCCM/AARC/ASA/APSF/AACN/CHEST joint statement on split ventilators is wrong. EMCrit. 29 March 2020. [Accessed 30 March 2020].

Available at URL:https://emcrit.org/pulmcrit/pulmcrit-wee-why-the-sccm-aarc-asa-apsf-aacn-chest-joint-statement-on-split-ventilators-is-wrong/