Authored by Ted Ngai & Richard Sarrach (question, comments, and suggestions pertaining to PPE should go to itl@pratt.edu)

Crisis

The medical community is facing a pandemic crisis compounded by a shortage of general medical supplies. Among them, there is a shortage of surgical gowns, test swabs, N95 masks, and face shields. Due to this pervasive problem, there has been a surge in innovative ideas to quickly design, prototype, and fabricate equipment that can protect patients and medical workers. They are generally called Personal Protection Equipment (PPE).

Below is a list of PPEs that have been widely adopted by the open-source community, and a few other projects that go beyond PPE. We will also list some of the design considerations and parameters to help you understand the design requirements of this equipment.

1. P.P.E. Overview

2. Face Shields

3. Face Masks

4. Medical Gowns

5. Intubation Hood

6. Snorkeling Mask

7. PAPR Air Supply Unit

8. Grab-a-lab

9. Swab Test Booth

10. Ventilator

11. Nasal Swabs

1. P.P.E. OVERVIEW

What is PPE:

FDA – PPE stands for Personal Protective Equipment. It is crucial to stopping the spread of COVID-19 and protecting healthcare providers (HCP) on the frontlines of the outbreak. Most PPE is designed to be used one time, by one person before properly disposing of them. It acts as a barrier between a viral/bacterial infection and a person’s skin, eyes, nose, and mouth, and creates an isolation bubble. Common medical protective equipment includes gloves, medical masks, respirators, gowns etc. 

Proper procedure of donning (putting on) and doffing (putting off) PPEs is extremely important. Although Wuhan China was the epicenter, their health care worker infection rate was impressively low, and that is due to their full PPE donning and doffing procedure. Each medical personnel has a donning and doffing partner to ensure every safety precaution is taken. They wear their suits for a full 8 hour shift and wear adult diapers. Also, it takes them 20 mins to doff and properly dispose of the PPEs at the end of their shift. 

Our effort to address the PPE shortage must take into consideration that full PPE is a system and every item must work in conjunction with one another. There is not a single item that can operate sufficiently by itself, the best way to ensure you are contributing positively is to reach out to medical professionals and get feedback, and be ready to meet stringent medical manufacturing requirements.

Overview of 3D printed medical equipment for COVID-19:

CATEGORY COMPONENT CLINICAL PARTNER/ TESTER CLINICAL STEPS COMPLETED CURRENT STATUS WHAT’S NEXT
Test Kits Nasal swabs USF Health, Northwell Health, Tampa General Hospital Emergency IRB approval, PCR test pass, ID sign off and pathology In production Scaling production at hospital partners and Formlabs’ facilities
Ventilators Tubing splitter (1 to 2, 3, and 4 patients) Northwell Health Passed lab testing with standard tubing Awaiting final files and clinical protocols Files and instructions made available later this week
Respiratory Mask (adapter) Snorkel or scuba mask conversion to PPE Several hospitals; MasksOn.org Lab testing Lab testing Additional lab testing
Facial Shield 3D printed frame Several hospitals Successful printing. Clinical fit varies by organization. Designs are available. Please coordinate with local health organizations. Continual monitoring of approved designs
Surgical Masks and Respirators N95 respirators and masks Several hospitals Successful printing. Clinical fit failure Temporarily on hold N/A (See Below)

Source: Formlabs COVID-19 response matrix.

2. FACE SHIELDS

The purpose of a face shield is to create a hard physical barrier between medical workers and patients. Among other important benefits of face shields, it also extends the life of N95 masks by preventing direct spray. This is the most commonly made PPE item by the opensource / maker community.

Design requirements:

  • Material has to be impermeable
  • Material must provide adequate visibility
  • Design need to allow for proper ventilation and avoids fogging
  • Headbands must stay on the wearer’s head and not slip.
  • Headbands should be comfortable.
  • Avoid using foam on the headband unless it is disposable (foam cannot be sterilized)

Common Materials Used:

  • PET, plastic bottle material, durable and does not absorb moisture, highly resistant chemicals and cleaning agents. Reusable.
  • Polycarbonate, common protective eyewear material. Impact, scratch, moisture, and chemical resistant. Reusable.
  • Acrylic and acetate are also common materials for the disposable version. These materials have weak chemical resistance and will deteriorate.

Currently in production at Pratt:

3D printed shield – 3dverkstan

Open Face PPE – Plastic and elastic face shield

Alternatives:

The National Institute of Health (NIH) has a large repository of 3D printed face shields designs

Prusa Protective Face Shield, RC2:

Budmen:

Education:

CBC (article on 3D printed shields)

3. FACE MASKS

The purpose of a N95 mask is to filter particles. Since SARS-COV-2 virus must attach itself to water droplets to transmit, N95 masks are very effective as it is rated to filter out 95% of particulate matter down to 0.3 micron.

The question is, should people make their own mask out of normal fabrica material? A study conducted in 2010 reveals that most common fabrics are ineffective filters. So it must be emphasized that any mask made with non-technical filtering fabric will not effectively filter out particles.

However, that is not to say we should not make masks. Masks provide other means of protection. Another most common route of entry for SAR-COV-2 is via surfaces. A normal fabric mask can act as a barrier if you touch a contaminated surface and then touch your face.

Design requirements:

  • Tight fit
  • Breathable.

 

Common Materials Used:

  • Hanes brand t-shirt and Norma Kamali brand sweatshirt are the highest performing fabric.

 

Masks developed in hospital research facilities:

North Shore Memorial Health (VIDEO LINK)

Olson mask (COVID-19)

4. Medical Gowns

There is a national shortage of surgical gowns due to a large recall in January. In particular, level 3 and level 4 gowns are needed for doctors treating covid-19 patients. Level 3 and 4 are water penetration and pressure rating standards. The primary function of a surgical gown is to mitigate the risk of blood and other fluids splattering onto the health care provider. Therefore, any alternative will need to be able to meet the same stringent requirements.

Design requirements:

  • Fluid impermeable, must adhere to ANSI/AAMI rating.
  • Open back to allow for breathability is a common design. Since Doctors will be wearing this for the full 8 hour shift, any other design must allow for proper ventilation.

 

Common Materials Used:

  • Tyvek Homewrap is manufactured to meet water penetration standards to Level 2, which is only for low risk use. However, one must take precaution when sewing and seaming Tyvek as sewing punctures the fabric. Refer to the official guide for seaming and sealing. Also consider taping the sewn seam as a last resort construction method. 

Designs currently tested by hospitals:

This is an surgical gown alternative for hospitals that are running critically low in supplies. https://www.peekaboopatternshop.com/isolation-gown/

5. Intubation Hood

During the Covid-19 outbreak back in February, a doctor in Taiwan created an acrylic box that shields the patient during intubation / extubation procedure. Doctors are particularly vulnerable during this procedure because patients are very likely to spray. This acrylic box design has been widely adopted and evolved by emergency room, intensive care unit, and operating room doctors. Currently Pratt is among a small group of doctors, engineers, and designers trying to improve the design of this intubation box. 

Design requirements:

  • Fluid impermeable membrane
  • Lightweight
  • Allow enough headroom for doctors to use their instruments
  • Must not contain anything the patient might hit
  • Must allow for air exchange via standard hospital suction tubes
  • Must have glove port
  • Disposable or sterilizable

 

Designs currently being prototyped at Pratt and tested by hospitals:

This design is currently being developed. There is an early prototype that is an evolution of the early acrylic box. Having said this, we do not recommend making these on your own unless you are working with a team of medical professionals.

https://www.youtube.com/watch?v=FYEqKPOAT44&amp=&feature=youtu.be

6. Snorkeling Mask

Snorkeling masks are being tested for 2 different applications, first is on the patient side and the other on the health care provider side. Currently, designs for the patient side involves working closely with the medical community and the mask must be connected to standard ventilators. Do not attempt to design this on your own unless you are in direct contact with health care providers. When parts have been tested and released under open source license, then feel free to help fabricate these. 

This project is much simpler on the health care provider side. The premise of this is due to the dwindling supply of N95 masks. So the primary objective is to find another source of filter that is equal to or better than N95, design a connector piece, and attach it to the mask. 

Design requirements:

  • Must use a filter that is equal to or better than N95. Commercial supply of HEPA filters is a popular choice. 
  • Connector must provide a tight seal between the HEPA filter and the mask.
  • 3D printed parts must not leak air. Common FDM prints are extremely porous, therefore, care must be taken to seal the surface. 

 

Common Materials Used:

  • HEPA filter made for handheld vacuum can easily be adapted to the snorkeling mask 
  • Use SLA 3D prints if you have access to one. 
  • With FDM prints, use ABS and perform vapor polish to create a sealed surface.

Currently in the prototyping phase at Pratt:

7. PAPR Air Supply Unit

PAPR stands for Powered air-purifying respirator. It is composed of 3 components, a hood, a standard connection hose, and a powered air supply unit. All hospitals have a small reserve supply for emergency situations. Hospitals also have an abundant supply of surgical hoods, which are powered with un-filtered air supply. What doctors are trying to do now is to develop a filtered air supply unit that can be retrofitted to surgical hoods. This involves designing a mobile blower fan unit that can be fitted onto a doctor’s belt with replaceable HEPA filters. 

Design requirements:

  • Design must adhere to CDC guidelines for PAPR designs. Pay attention to safety features, clinicians must be alerted when the battery is low and not able to maintain air pressure. 
  • Design integration of blower fan, battery, battery controller, and HEPA filter in a lightweight package that can fit comfortably on a belt.
  • Blower fan need to provide a minimum of 230 liters per minute (~8 CFM)
  • Blower fan need to provide a minimum of static pressure of 249 pa
  • Battery needs to either supply power for over 10hrs or be swappable.

 

Common Materials Used:

  • Computer blower fans usually will meet the flow rate and static pressure requirements. You can find 12v or 5v DC versions, this choice is entirely based on what battery unit you want to pair this with. 
  • Battery pack 12v or 5v. You can consider using off the shelve power drill batteries, which is commonly 12v, or USB battery bank, which is commonly 5v.
  • HEPA filter made for handheld vacuums 

Currently in the prototyping phase at Pratt. Prototype being done at Duke can be found here

8. Grab-a-lab

This is a design idea initiated by health care providers who have to do many test swabs per day. The design premise is, due to the volume of test swabs, they want to find a way to minimize potential cross-contamination by eliminating any unnecessary steps between swabbing someone and putting the swab into a sealed container. This idea being prototyped is similar to a bag dispenser that would allow someone to take out a swab, swab a patient, grab and open a bag in one gesture, drop the swab in, seal the bag, and place the seal sample somewhere safe. So most likely this is a 3 part design, a swab dispenser, a bag dispenser, and a test sample storage. The design challenge comes when considering the person doing this is heavily armored with protective gear and radically limited dexterity. 

Design requirements:

  • Test swab dispenser. 
  • Sealed bag dispenser, ideally allows HCP to grab and open the bag with 1 hand.
  • Test sample storage, foot pedal for opening the unit.

 

Common Materials Used:

  • Designs that are being tested currently are 3D printed. However, this is a product that will see heavy use, final design should be molded for durability. 3D printed mold is a good option.

9. Swab Test Booth 

Currently Pratt is not yet participating in the design / fabrication of this.

South Korea is one of the countries with a very low death rate, many attributed this to the vast network of test sites. To facility fast and safe testing, they have designed a phone booth type facility to allow patients and medical workers to swab 10X more efficiently than most other countries. Hospitals are working with local fabricators to create versions suitable for their own context. 

Design requirements:

  • Booths must be sterilized between patients. 
  • Provide a negative pressure chamber.
  • Glove port must be large enough, min. 7” diameter to accommodate HCP of different heights.

10. Ventilator

Currently Pratt is not yet participating in the design / fabrication of this.

There are many many efforts to make opensource ventilators. Ventilators are very complex machines, 95% of all opensource projects are not suitable for use, and will most likely cause barotrauma, so be very careful how you select the project to contribute. 

A ventilator is not just a pump that pumps air into the patient’s lungs. Health Care Providers need to precisely calibrate the rate of inhalation and exhalation, and more importantly, not have lungs completely deflate during the exhalation cycle. The ventilator unit controls all that with pressure and air flow sensors. If you see a ventilator project, first check and see if they have pressure and volume control. If they don’t, move on. 

If you are still not put off by this, continue reading. Currently there are only 2 viable opensource projects, although more may get closer to viability in the future. They are AmboVent and ApolloBVM. Both designs, like most other projects, employ the use of Bag Valve Mask. However, these ones have additional electronic sensing circuits to make their system viable. You can find some design sketches from their websites and see where you may be able to help. 

There are also several closed-source projects being developed that may become game changers. 

Agva is an Indian company that has made a low cost ventilator by linking controls to a smartphone, thereby eliminating the need of an experienced operator. However, the Indian government has restricted all ventilator exports. Agva is now seeking foreign partners to establish manufacturing lines in other countries to make this ventilator more widely available. 

Medtronic is the biggest ventilator manufacturer in the US, and they have just released the design specifications of one of their lower end ventilator units under a permissive use license. The opensource community is rallying around this now. The company is releasing their design spec in stages. Although incomplete, this is the project that has the highest promise. 

11. Nasal Swabs

Currently Pratt is not yet participating in the design / fabrication of this.

Due to yet another national shortage of nasal swabs, many hospitals are experimenting with 3D printing their own nasal swabs. The manufacturing requirement of this is very stringent and we do not recommend this project to be taken on. Currently Pratt has the ability to 3D print the swabs, but we do not have a capability to ensure the swabs are sterile. Sterilization procedures are still being tested in hospitals around the country. There will be updates regarding the sterilization standards and if we can in fact contribute to this.