Emergency ventilator circuit splitter

3D Printable & Free

The COVID-19 Pandemic is pushing the world’s availability of ventilators to the limit. In response, our team of doctors designed this FDA approved for emergency use 3D printed ventilator circuit splitter in case we run out of ventilators. 

It’s free for everyone in the world to use.

VentSplitter is FDA approved for emergency use during the COVID-19 pandemic.

ventilator shortage?
Ventilator splitting!

  The rapid spread of SARS-CoV2 throughout the world has put an unimaginable strain on the healthcare system. Patients are at risk of facing the consequences of not enough ventilators, which in dealing with respiratory failure is fatal. This is a last resort, emergency-only device for use if ever faced with a critical shortage of ventilators. 

   The concept of ventilator sharing to our knowledge was first written by Dr. Neyman and Dr. Irvin in 2006 (Ac Emergency Medicine 2006). They demonstrated that by using T-tubes and adapters, a ventilator circuit could be divided such that four simulated patients could share a single ventilator in emergency circumstances. Although only simulated in the original article, this technique was successfully used by Dr. Menes in the 2017 Las Vegas shooting mass casualty incident. This technique saved the lives of patients, buying time until more ventilators could arrive. 

   Some hospitals do not have the T-tubes or other parts readily available to setup a ventilator for multiple patients. This free 3D printed part can be used in such situations.

   Our goal is to have an easily printed 3D part so that anyone in the world, who may need it in dire circumstances, can use it to save lives.  

This is for emergency, last resort use only! This 3D design has only been simulated with ventilators and bags, not humans (yet). 

respiratory failure

2-4% of all COVID-19 patients will require mechanical ventilation.


The USA has approximately 160,000+ ventilators. Some projections suggest we will need 600,000+ at the peak of the COVID-19 outbreak.

“Our goal is to have an easily printed 3D part so that anyone in the world, who may need it in dire circumstances, can use it to save lives.”

how it works

First, please read Dr. Neyman’s paper here.

Two patients

To ventilate two patients on one ventilator, place one splitter on the inspiratory limb and one on the expiratory limb as shown. 

Four patients

To ventilate four patients, you need a total of 6 splitters arranged such that each of the splitters in the “Two Patient” scenario has an additional splitter on each limb.

more than four?

It may be possible to ventilate more patients, however the flow limits of a ventilator cap the total volume that can be delivered. With that said, since this is a modular design, you can ventilate 3,4,5,6,7+ patients.

Flow limiters

Ideally, similar patients (ideal body weight, lung compliance, etc) should be on the same ventilator.  However you may be forced to pair patients with mismatched lung compliances. In this case we designed flow limiters of varying sizes to offer adjustability. These are to be added immediately downstream of the inspiratory splitter. Anytime a limiter is placed the ventilatory system, one way valves must be placed on all expiratory limb connections to prevent backward flow through the system. 

In general, all attempts should exhausted to match patient lung compliance when ventilator splitting, before attempting to use the Flow Limiters. The exact effects of the the Flow Limiters on pressure and flow vary greatly, depending on the difference in lung compliance of the patients, total inspiratory time, mode of ventilation, flow rates, peak pressures. Use of flow limiters can have varied effects, and thus extreme caution and constant monitoring is required. 

who we are

the ventilator circuit splitter team

bryan lai, md

Anesthesiologist, Pain Medicine Physician
San Antonio, Texas, USA
University of Texas Health Science Center at San Antonio

scott pew circle

scott pew, md

Anesthesiology Resident PGY-4
San Antonio, Texas, USA
University of Texas Health Science Center at San Antonio

jennifer circle

jennifer erian, md

Anesthesiologist, Pain Medicine Physician
San Antonio, Texas, USA
Consultants in Pain Medicine


Max eckmann, md

Anesthesiologist, Pain Medicine Physician
San Antonio, Texas, USA
University of Texas Health Science Center at San Antonio

DOwnload ventilator circuit splitter

start printing now


Circuit Splitter & Flow Limiter Pack in STL format Version 2.0 (4/1/2020)

WARNING! Use at your own risk, and if loss of life is otherwise inevitable!

The original flow limiter pack has 10-18mm orifices, which we found not that useful in practice, but can still be downloaded here.


  • 4/2/20 – Limiters 2.0a – #7 was missing the number “7”
  • 4/1/20 – V2.0 – Splitter has refined dimensions, elongated connectors for better connection grip, stronger walls. Major improvement in Flow Limiter design and strength.
  • 3/26/20 – Limiters 1.1a – added more useful sizes of the limiters 2-9mm. Fixed mesh bug.
  • 3/25/20 – Splitter 1.1. FIXED: A small bug in the mesh of the wall may cause errors slicing the STL.  


Recommended Print Settings:

  • Everything was modeled on  0.4mm nozzles
  • Use biocompatible filament
  • 100% infill for strength and leak reduction
  • 0.2-0.3mm layer height. Smaller layer heights might be related to less leakage around connections
  • No supports are needed for any print
  • The Circuit Splitter should be printed in an upside down “Y” shape on  FDM (fused deposition modeling) printers
  • The Limiters should be printed in an upright position like a drinking cup
  • Consider a brim for the splitter


Reasons to Reject Prints

  • The single port should have an inside diameter >22.1mm & <22.75mm measured at the outermost point
  • The dual ports should have an outside diameter of >21.5mm &  <22.0mm measured at the outermost point
  • Of course the standard would be to have your prints test fitted on the actual machines intended for use.
  • If your print does not meet these specifications, please scale your prints so that they are in specification. Do not distribute to hospitals or put into circulation.

warnings & Limitations

  • Always use inline filters to reduce cross-contamination & filament migration.
  • One way valves are recommended are recommended to also reduce cross-contamination.
  • One way valves are REQUIRED on the expiratory limbs if using flow limiters to prevent unintended backward flow through the system. 
  • All patients must be fully relaxed, and not spontaneously breathing.
  • You must use caution to avoid hyperventilation and barotrauma if you have significantly mismatched patients attached to one ventilator.
  • 3D printing across many users is inherently variable. Check the printed piece on the intended ventilator for fit before mass production.
  • 3D printed parts can break. Be gentle and cautious for failures while in use.
  • Return to single patient ventilation as soon as ventilators become available.
  • If you do not have a strong understanding of ventilator/lung mechanics, do not use this. 
  • VentSplitter is FDA approved for emergency use during the COVID-19 pandemic, however you must register with VentSplitter and the FDA to obtain FDA approval process for manufacturing.

We hope you never have to use it.


We want to see and hear from you! Any comments or feedback is greatly appreciated! Shows us your prints!

Most importantly we need to know if you are running into any problems or compatibility issues!