A ventilator with low-cost and accessible components that can be quickly replicated anywhere. It implements the pressure-controlled continuous mandatory ventilation mode (PC-CMV) with settable breathing rates and expiration/inspiration time ratios.

Minimalist Pressure-controlled  Emergency Ventilator

The development of this project is possible due to the contribution of LIP, UNIDEMI, FCT NOVA, Nova Medical School, ICNAS, Harvard University and two Portuguese engineers working for the F&oacute;rmula 1 teams.The design tries to minimize the use of technical components and those used are common in industry, so its construction may be possible in times of logistical disruption or in areas with reduced access to technical materials and at a moderate cost. Most of the device can be manufactured with modest technical means.It should be clear that the devices presented are meant to be for proof-of-concept only &nbsp;and &nbsp;it &nbsp;is &nbsp;not &nbsp;implied &nbsp;that &nbsp;they &nbsp;may &nbsp;be &nbsp;suitable &nbsp;as &nbsp;bedside &nbsp;instruments. &nbsp;Further engineering will be required for that purpose, adapted to the local conditions. As the components proposed are not medical-grade, the use of a ventilator made on this basis should be considered only as a last resort solution. &nbsp;Principle of operation&nbsp;The &nbsp;schematic &nbsp;representation &nbsp;of &nbsp;the &nbsp;proposed &nbsp;emergency &nbsp;ventilator &nbsp; is &nbsp;shown &nbsp;in Figure 1. Pure oxygen at the standard pressure of 4 bar (400 kPa) is fed from the hospital supply to an adjustable pressure regulator with output range of 10 to 40 mbar, allowing the PIP pressure to be set by just turning a knob. The &nbsp;regulator &nbsp;output &nbsp;is &nbsp;fed &nbsp;to &nbsp;the &nbsp;inspiration &nbsp;electrovalve &nbsp;V1. &nbsp;This &nbsp;valve &nbsp;should &nbsp;have enough of an aperture for the air to pass through easily at normal breathing flows. &nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1586374766412-Schematic+Ventilator.png">Figure 1 &ndash; Schematic representation of the proposed emergency ventilator. &nbsp; A closed deposit (R1) may be placed on this line to provide a reserve of pressurized air for &nbsp;faster &nbsp;pressurization &nbsp;of &nbsp;the &nbsp;lungs &nbsp;upon &nbsp;inspiration. &nbsp;This &nbsp;helps &nbsp;to &nbsp;make &nbsp;the &nbsp;pressure profile more rectangular in shape, which is clinically desirable. The output of V1 connects to the C1 water column, to the M1 water manometer and to the &nbsp;patient &nbsp;inspiration &nbsp;tube, &nbsp;which &nbsp;is &nbsp;a &nbsp;consumable &nbsp;item &nbsp;normally &nbsp;provided &nbsp;by &nbsp;the hospital. The &nbsp;C1 &nbsp;water &nbsp;column &nbsp;provides &nbsp;a &nbsp;safety &nbsp;purge &nbsp;to &nbsp;the &nbsp;atmosphere &nbsp;in &nbsp;case &nbsp;of &nbsp;any malfunction that may cause a dangerous overpressure of oxygen to the patient. It can be set by adjusting the water level H1 to be slightly &nbsp;above the maximum intended PIP. &nbsp;In normal &nbsp;operation &nbsp;there &nbsp;should &nbsp;be &nbsp;no &nbsp;gas &nbsp;flowing &nbsp;through &nbsp;this &nbsp;column. &nbsp;To &nbsp;fulfill &nbsp;its safety &nbsp;purpose, &nbsp;the &nbsp;connecting &nbsp;and &nbsp;inner &nbsp;tubes &nbsp;should &nbsp;have &nbsp;sufficient &nbsp;diameter &nbsp;for &nbsp;a considerable gas flow to pass through without overpressure.&nbsp;The &nbsp;M1 &nbsp;U-tube &nbsp;water &nbsp;manometer &nbsp;measures &nbsp;the &nbsp;PIP &nbsp;and &nbsp;PEEP &nbsp;pressures &nbsp;directly &nbsp;in cmH2O by mere observation of the water height difference H3. The tube length should comfortably &nbsp; exceed &nbsp; the &nbsp; intended &nbsp; maximum &nbsp; PIP. &nbsp; Optionally, &nbsp; for &nbsp; more precise measurement, near critical damping of the water column oscillations can be achieved by adjusting the needle valve V3. Even then, it was observed that the column only reached a &nbsp;stationary &nbsp;state &nbsp;in &nbsp;each &nbsp;breathing &nbsp;stage &nbsp;for &nbsp;the &nbsp;12 bpm &nbsp;rate, &nbsp;so &nbsp;the &nbsp;absolute &nbsp;pressure adjustments &nbsp;should &nbsp;be &nbsp;made &nbsp;at &nbsp;such &nbsp;rate &nbsp;or &nbsp;lower. &nbsp;A &nbsp;more &nbsp;viscous &nbsp;liquid would probably also improve this characteristic.&nbsp;If filled with a conductive liquid (e.g. salted water), the sustained presence or absence of the &nbsp;liquid &nbsp;at &nbsp;certain &nbsp;levels &nbsp;is &nbsp;perceptible &nbsp;(with &nbsp;the &nbsp;help &nbsp;of &nbsp;simple &nbsp;electronics) &nbsp;by electrodes &nbsp;placed &nbsp;across &nbsp;the &nbsp;tube. &nbsp;Both &nbsp;high &nbsp;and &nbsp;low &nbsp;PIP &nbsp;and &nbsp;PEEP &nbsp;alarms &nbsp;can &nbsp;be implemented.&nbsp;From &nbsp;the &nbsp;patient &nbsp;&quot;Y-piece&quot; &nbsp;the &nbsp;expiration &nbsp;tube &nbsp;connects &nbsp;to &nbsp;the &nbsp;expiration &nbsp;electrovalve V2, similar to V1.&nbsp;Finally, the expiration air is vented to the atmosphere through the water column C2. The water level H2 directly determines the PEEP pressure.&nbsp;The &nbsp;valves &nbsp;must &nbsp;be &nbsp;electrically &nbsp;commanded &nbsp;with &nbsp;adjustable &nbsp;rate and &nbsp;duty-cycle &nbsp;in &nbsp;the ranges &nbsp;stated &nbsp;in &nbsp;the &nbsp;introduction. &nbsp;There &nbsp;are &nbsp;several &nbsp;electronical &nbsp;solutions &nbsp;for &nbsp;this functionality, adjustable to the availability of components.&nbsp;Two slightly different devices were built independently for cross-check purpose.A note is in order here to justify the extensive use of water columns in this design:&nbsp; The &nbsp;water &nbsp;column &nbsp;is &nbsp;a &nbsp;device &nbsp;with &nbsp;many &nbsp;interesting &nbsp;flow-control characteristics: &nbsp;(a) &nbsp;it has no moving parts except the water itself, so it is very reliable and easy to build; (b) it regulates &nbsp;air &nbsp;pressure &nbsp;in &nbsp;the &nbsp;tens &nbsp;of &nbsp;cmH2O &nbsp;range &nbsp;accurately, &nbsp;adjustably, &nbsp;and &nbsp;quite independently &nbsp;of &nbsp;the &nbsp;flow; &nbsp;(c) &nbsp;if &nbsp;made &nbsp;of &nbsp;transparent &nbsp;materials &nbsp;the &nbsp;observation &nbsp;of &nbsp;the difference &nbsp;in &nbsp;water &nbsp;levels &nbsp;between &nbsp;the &nbsp;two &nbsp;vessels &nbsp;provides &nbsp;direct &nbsp;information &nbsp;of &nbsp;the differential pressure; and (d) it provides check-valve functionality up to a certain reverse pressure. &nbsp;Besides &nbsp;being &nbsp;bulky, &nbsp;the &nbsp;main &nbsp;drawback &nbsp;of &nbsp;the &nbsp;water &nbsp;column &nbsp;is &nbsp;the &nbsp;water &nbsp;itself, &nbsp;as &nbsp;its level &nbsp;must &nbsp;be &nbsp;adjusted/monitored &nbsp;and &nbsp;may &nbsp;become &nbsp;bacterially &nbsp;contaminated, &nbsp;requiring anti-bacterial treatment. The water may be replaced by other suitable substances such as low viscosity oils. It is clear that the functionality provided by the water columns can be performed more conveniently by traditional pneumatic components, if available.The details have been systematized in a scientific paper that is now available for consultation: Proof-of-concept of a minimalist pressure-controlled emergency ventilator for COVID-19. The patent has been registered in the name of Humanity, so that no one can benefit from this innovation.

This research paper describes two designs of the emergency ventilator.

Proof-of-concept of a minimalist pressure-controlled  emergency ventilator for COVID-19

Homepage of the volunteer project that formed the basis for the Minimalist Pressure-controlled Emergency Ventilator. 

Project Open Air

Positive Inspiratory Pressure (PIP) 

Positive End Expiratory Pressure (PEEP) 

Pure oxygen operation

Safety  pressure  relief  valve 

Breathing rate

Inspiration/expiration time ratio (I/E)

A ventilator with low-cost and accessible components that can be quickly replicated anywhere.
The simple ventilator implements the pressure-controlled continuous mandatory ventilation mode (PC-CMV) with settable breathing rates and expiration/inspiration time ratios.

Positive Inspiratory Pressure (PIP)	10-40	cmH2O
Positive End Expiratory Pressure (PEEP)	0-20	cmH2O
Pure oxygen operation
Safety pressure relief valve	0-45	cmH20
Breathing rate	12-25	breaths per minute (bpm)
Inspiration/expiration time ratio (I/E)	1:1 to 1:3