The MADVent Ventilator

The COVID-19 pandemic has produced critical shortages of ventilators worldwide.

There is an unmet need for rapidly deployable, emergency-use ventilators with sufficient functionality to manage COVID-19 patients with severe Acute Respiratory Distress Syndrome. We have developed and validated a simple, portable, and low-cost ventilator that may be rapidly manufactured with minimal susceptibility to supply chain disruptions. This single-mode continuous, mandatory, closed-loop, pressure-controlled, time-terminated emergency ventilator offers robust safety and functionality absent in existing solutions to the ventilator shortage. Validated using certified test lungs over a wide range of compliances, pressures, volumes and resistances to meet U.S. Food and Drug Administration standards of safety and efficacy, an Emergency Use Authorization is in review for this system.

Recently accepted in Wiley's Medical Devices & Sensors (DOI: 10.1002/mds3.10106), the details of the ventilator are provided below; the capabilities are summarized here.

table MADVentcapabilities
fig1 MADVentphoto

### Advantages of our approach

Our ventilator design offers novel advantages over the current panoply of commercial, emergency-use FDA-approved, and FDA-unapproved but widely publicized ventilator designs as follows:

1. The MADVent ventilator is tailored to treat COVID-19 patients as, formally (ISO 19223), a single-mode continuous, mandatory,
pressure-controlled, time-terminated design. Most low-cost ventilators function instead as volume-control ventilators,
delivering air into the lungs even to excessive pressure, which can lead to lung injury, especially in ARDS lung-compromised patients
typical in this COVID-19 pandemic.

2. The MADVent has a novel torque conversion mechanism via a simple pulley and lanyard system to convert the relatively low-torque, high speed rotation of the motor to a high-torque, reduced speed resuscitation bag compression mechanism. This is superior to the
ubiquitous geared rack-and-pinion mechanisms of other low-cost ventilators as it offers greater pressure, at least doubles the
maximum ventilation rate, has no backlash,, and is far quieter. It is also much more durable, as the nylon geared mechanisms used in
other systems are subject to wear and failure much faster than our approach.

3. Unlike all low-cost ventilators known to us, we offer a fully alarmed ventilation operation suitable for life support, commensurate with the strict requirements of the FDA for life-support ventilators, even in a pandemic.

4. We uniquely determine the volume of air delivered through knowledge of the resuscitation bag characteristics and a model of its compression based on the rotation angle of the motor. This obviates the need for expensive airflow sensors and the complex algorithms necessary to compute the volume from airflow. It also drastically reduces the cost of our ventilator, to about $300 in parts and less than $500 including assembly; an airflow sensor approved for use in ventilators is  $150 alone. This furthermore offers the possibility of offering other ventilation modes in the future, such as volume-control or patient-initiated ventilation.

5. We have pursued a comprehensive strategy of low cost, worldwide accessible parts in the design. In this pandemic, supply lines are disrupted and the complex designs of many ventilators, open source designs included, are simply not produceable due to parts shortages. Our design avoids this problem, from the ability to use 3.3 VDC or 5 VDC pressure sensors to the exclusion of valves and motors that are simply unavailable.

Fabrication, parts, and assembly information

fig5 MADVentrender

A complete set of files are provided here to enable you to make the ventilator from this design. This information includes the drafting files, computer code, and assembly information suitable for your use per the copyright statement at the bottom of this web page.

- Computer-aided drafting files (CAD) in SolidWorks format are available here; some basic information on the parts and circuit is here.
- Code for the Arduino controller are available here.
- Detailed assembly instructions are provided here.
Product labelingoperating instructions, and the technical description of the ventilator are also provided; these have been prepared for FDA Emergency Use Authorization.

fig3 tidalvolume

Volume-driven alarms for COVID-19 patients' life support

The MADVent Mark V has alarms for high and low volume that may be set between 200 and 1000 mL. In the example at right, the system was run at a rate of 13 breaths per minute, a PEEP value of 15 cmH2O, and a compliance of 0.03 L-cmH2O.

(A) The high-volume alarm threshold was set to 500 mL for the first case. PEEP was decreased from 15 cmH2O to 5 cmH2O in order to increase the tidal volume delivered to the lung simulator. A high-volume alarm was triggered when the calculated tidal volume exceed the limit set by the healthcare provider. A relevant clinical scenario for this alarm would be a leak in the inspiratory circuit leading to an increase in volume delivered without the target pressure being reached.

(B) The low-volume alarm is triggered once the calculated volume drops below the lower limit set by the healthcare provider. This was simulated here by increasing the PEEP up to 17 cmH2O. A relevant clinical scenario for this alarm would be the inspiratory line being kinked.

(C) The high-pressure scenario was simulated by interrupting the expansion of the lung simulator during inspiration to simulate a patient coughing. The high-pressure alarm was triggered when the pressure exceeded the set value of 30 cmH2O.

Other scenarios include a 24-hour operation test and twelve adverse ventilation situations per ISO80601-2-80:2018 table 201.105, as required by the FDA.

fig3 tidalvolume

Ventilator-delivered volume is related to the motor's rotation

Tidal volume delivered by the ventilator is related to the rotation of the motor via compression of the bag, as indicated (A) by the experimental results compared with a model constructed from the geometry. 

In (B) the volume corresponding to a given motor rotation is seen to increase with compliance---accounting for the spread in the data along with experimental error.

In (C), the difference between peak pressure and PEEP is seen to increase along the model, as expected due to the ideal gas law.

This eliminates the need for airflow sensors. Airflow sensors are extremely expensive, require advanced algorithms to produce delivered air volume estimates, and are difficult to obtain in a pandemic.

fig3 tidalvolume

Pressure-driven alarms for COVID-19 patients' life support

The MADVent also has alarms for high and low pressure that can be set between 0 and 50 cmH2O defined by the caregiver. Using a ventilation rate of 34 breaths per minute, a PEEP value of 5 cmH2O, and a lung compliance of 0.03 L-cmH2O, volume alarms were set on the MADVent to identify adverse ventilation.

(A) The low and high-pressure alarm thresholds were set to 2 cmH2O and 42 cmH2O respectively. PEEP values were increased from 5 cmH2O to 20 cmH2O and lowered back down to 5.0 cmH2O to ensure that the in-line pressure sensor could detect and display changes in pressure values. A high-pressure condition was simulated by decreasing patient lung compliance. The system triggered an alarm once the pressure exceeded 42 cm H2O.

(B) The low-pressure alarm is triggered once the in-line pressure value drops below the lower limit. A low-pressure situation was simulated by disconnecting the endotracheal tube to trigger an alarm which results in the system immediately stopping.

(C) In the event that the tubing is kinked or there is a blockage in the endotracheal tube, the pressure begins to rise until the upper threshold is reached. This triggers a high-pressure alarm and causes the system to resume ventilation at a lower volume, but at an increased rate according to the set minute ventilation.

Team responsible for this effort

Aditya Vasan

MADLab PhD student
Mechanical and Aerospace Engineering, UCSD

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William Connacher

MADLab PhD student
Mechanical and Aerospace Engineering, UCSD

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Reiley Weekes

PhD student
Mechanical and Aerospace Engineering, UCSD

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Jeremy Sieker

School of Medicine, UCSD

Mark Stambaugh

Circuit superhero
Qualcomm Institute, UC San Diego

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Daniel Lee

Professor, Departments of Anaesthesiology and Pediatrics, UCSD

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Preetham Suresh

Department of Anaesthesiology, UCSD

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William Mazzei

Professor, Department of Anaesthesiology
UC San Diego

Eric Schlaepfer

Independent Researcher, Sunnyvale CA

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Johan Petersen

Post-doc, Department of Anaesthesiology, UCSD

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Theodore Vallejos

Manager of Technology, Department of Respiratory Care, School of Medicine, UCSD

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Sidney Merritt

Associate Clinical Professor, Department of Anaesthesiology, UCSD

Lonnie Petersen

MADLab, Center for Medical Devices, Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering, UCSD

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James Friend

Professor, MADLab, Center for Medical Devices, Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering; Department of Surgery, School of Medicine, UCSD

Gratefully supported by

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with funding, facilities, and staff

Our Leadership Team

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Lonnie Petersen

Lonnie (MD,PhD) completed her MD from the University of Copenhagen, Denmark in 2007 and has worked in Emergency Medicine and Intensive Care. Dr. Petersen received her PhD in Gravitational Physiology and Space Medicine in 2016. Currently an assistant Professor the University of California, San Diego and supported by NASA, DoD, and the Novo Nordic Foundation as well as being a Sapera Aude Fellow (National Research Council). Her research is rooted in cardiovascular, cerebral and exercise physiology always with an integrative physiology approach.

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Casper Petersen

Casper “Johan" (MD) graduated from University of Copenhagen in 2008 and has worked in Cardiology and Emergency Medicine. He has focused on research in renal physiology and sympathetic reflexes as well as physiological fluid shifts in regard to space and aviation medicine and countermeasure development for long term space travel. Dr. Petersen is supported by NASA , Kratos and ONR and currently holds a position as Assistant Project Scientist at University of California, San Diego.

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James Friend

James (BSAero, MSME, PhD) leads the Medically Advanced Devices Laboratory in the Center for Medical Devices at the University of California-San Diego. He is a professor in both the Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering, and the Department of Surgery, School of Medicine. He has over 270 peer-reviewed research publications, including 140 journal papers and eight book chapters, and 29 patents in process or granted, completed 34 postgraduate students and supervised 20 postdoctoral staff, and been awarded over $25 million in competitive grant-based research funding over his career. He is a fellow of the IEEE.

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