How to build a Better Respirator – Faster and Cheaper Robert Ferrand 3/26/2020
A Report to the Army Corps of Engineers
The CDC is reporting that the Covid-19 Pandemic could require as many as 1,000,000 respirators. The US has 170,000 respirators in hospitals and another 8,000 in the strategic stock pile. We cannot get there from here, without a different strategy. This document outlines that “different” strategy to build thousands of respirators in a short amount of time. Coronavirus ventilator dependent mortality rates are high. However, ventilator dependent mortality rates are always high. “Positive Pressure” Respirators are damn dangerous, because they are “Invasive” and almost always do some damage. Among critically ill COVID-19 patients in China, the reported case fatality proportion was 49%. In a report from one hospital, 61.5% of critically ill patients with COVID-19 had died by day 28 of ICU admission. [9,15] Ventilator-associated pneumonia (VAP) is the most common lethal infection observed in patients who require treatment in intensive care units (ICUs).i The crude mortality rate for VAP has been cited to be as high as 70%. Those are similar rates to Coronavirus mortality. Are the respirators killing the patients or COVID-19. This is an important question as we embark on building 1,000,000 respirators. Quoting the President in a different context, “Is the Cure worse than the Disease?” Are these Respirators the design we should be building? Fair Question. These respirators required knowledgeable trained critical-care nursing staff. There are 500,000 critical care nurses of which 250,000 work in ICU. There are an additional 100,000 Respiratory Therapists. If we could build enough the respirators there are enough knowledgeable personnel to operate these “Positive Pressure” respirators. Assuming that the parts can be sourced, in such a short term, when many companies are sourcing the same technically demanding parts…. The number of respirators that can be built is limited. Significantly, these Respirators cost $50,000 each. In this emergency they will cost even more. Most Importantly, Hospitals cannot afford the Millions of Dollars required for a piece of equipment that will then not be used after the crisis. There is another strategy. While “Positive Pressure” ventilation is the current preferred method, there is another way to provide mechanical ventilation – “Negative Pressure”. This was the preferred method in the last major epidemic – During the polio epidemic in the 1950’s negative pressure respirators saved countless lives. (Ed Roberts in his Iron Lung) This “Non-Invasive” technology may apply today, because it does not require Critical Care Nursing support.
To accomplish ventilation, a pressure difference must be developed phasically across the lung. This difference can be generated by negative pressure in the pleural space, by positive pressure applied to the airway opening, or by a combination of both. Negative-pressure ventilation (NPV) can be defined as a type of ventilation in which the surface of the thorax is exposed to subatmospheric pressure (i.e. negative pressure) during inspiration (fig. 1⇓). This subatmospheric pressure causes thoracic expansion and an attendant decrease in pleural and alveolar pressures, thereby creating a pressure gradient for air to move from the airway opening into the alveoli. When the pressure surrounding the thorax increases and becomes atmospheric (or greater than atmospheric), expiration occurs passively owing to the elastic recoil of the lung and chest wall.ii While America chose to make these Iron Lungs from steel, England choose a different material: Wood. With a rich history of building boats, ships and airplanes from wood, small shops all over Britain made simple wooden respirators. This design effort saved the lives of countless numbers of people. Amazing as it may be, Popular Mechanics actually published such a design for an “Emergency Wooden Respirator” in the Golden Anniversary issue in January 1952. The Journal of the American Medical Association also published an article on the same subject. JAMA. 1951;145(7):485. doi:10.1001/jama.1951.72920250005008b. In 2011, The Rotary Club built a wooden respirator to this design. Video Link https://www.youtube.com/watch?v=wmwKo4BQ5rs
It might be possible to employ this design and mobilize Rotary Club, the Carpenters Unions, and ordinary citizens to build these respirators locally from locally sourced materials. However, there might be a more effective strategy. The attached An Historical Perspective of Respirators was written by this author, in 1985. This report was generated from a feasibility study to reinvent the Iron Lung, originally commissioned by David Crosby and Graham Nash: The Wooden Lung Project. Both musicians’ intent was to provide a more esthetic environment for one of their road manager’s father, who had been living in an Iron Lung for 25 years. The Crosby Nash Wooden Lung video shows this elegant wooden respirator actually being built. However, the significance of the Wooden Lung Project is not the wood …..it is the “Computer Controlled Calibrated Feed-back Loop” to drive the system. This white paper provides the History and “Clinical” rationale for making respirators from wood. It outlines the numerous dangers of employing “Positive Pressure” and the numerous benefits of employing Negative Pressure. The real significance of this Project was: instead of using the bellows technique employed on the Iron Lung, this author employed a new designed Apple II computer with a turbine blower generating a vacuum. By using a simple pressure transducer with an Analog to Digital Converter measuring the pressure inside the chamber a high-volume valve can modulate the internal negative pressure between atmospheric and sub atmospheric with a stepper motor controlling a high-volume valve – thereby creating a “calibrated pressure “feed-back” loop. A Voice Activated Turbo Charged Superlight Wooden Lung with Intelligence.
This paper became the foundation for the design of the most advanced specialty hospital bed, AirLogic Specialty Hospital Bed. Video Link https://www.youtube.com/watch?v=kXGUIlVb7uM&t=72s Now an improved version of this system could be made from readily available technology, today, for a cost of goods in the $1,000’s maybe less, in quantity. COMPUTER CONTROLLED CALIBRATED “FEED-BACK” LOOP WITH VACUU CLEANER Negative Pressure Respirator Stepper Driver
Stepper Motor Vacuum
Computer
Carburetor Pressure Transducer
Vacuum Cleaner A/D Converter
COMPUTER CONTROLLED CALIBRATED “FEED-BACK” LOOP WITH DIGITAL MOTOR
Stepper Driver Vacuum Digital Motor
PC Motherboard
Pressure Transducer A/D Converter
The Challenge is creating the Chamber for the Patient. The attached An Historical Perspective of Respirators has a dozen conceptual designs, however one in particular the “Tunic” Design is relevant. This design is basically a Roman Centurion Chest Plate. This is not a new idea, it has been used in various forms for decades. Thus the FDA must have “Protocols” readily available that can be quickly adapted to expedite 510K approval as “Substantially Equivalent” to existing technology.
These legacy designs cannot generate the larger vacuums of the Iron Lung, however, by using some Fancy Dancy Engineering, we might be able to get close to the performance of the Iron Lung, without the inherent dangers of “Positive Pressure” and save thousands of lives.
Legacy Design
Conceptual Design
Centurion Breastplate
Looking at available resources: think baby “Quonset hut”.. Take any 18 inch pipe and gauge. Cut the pipe in half. Place the patient in a “Korean War Poncho” and you have a mini-respirator chamber. We have all the other components, “readily available” mother boards, pressure sensors, A/D converters, stepper motors, stepper driver controllers. And even vacuum cleaners. Think Liberty Ships…..fall back technology, simple easy to build. FAST. A significant improvement to the History of Respirators could to made here, that will have a lasting impact beyond this Pandemic. Now this virus may crest too fast for us to react. However, if “Out of the Box” thinking is required, this strategy is a good candidate. Robert Ferrand Inventor/Filmmaker 650-576-3334 producer@thelastliberty.com
i
https://academic.oup.com/cid/article/38/8/1141/2118237
ii
https://erj.ersjournals.com/content/20/1/187
www.thelastliberty.com
. (Ed Roberts in his Iron Lung) https://www.youtube.com/watch?v=pJB7WPmVKec&t=88s “Emergency Wooden Respirator” https://issuu.com/saddlefittinginfo/docs/pm_emergency_wooden_respirator?fr=sY2VjZDEyOTc1NA Crosby Nash Wooden Lung https://drive.google.com/file/d/1XkFH4v68ll80WJRXLS6k2RgT-LyMAksb/view An Historical Perspective of Respirators https://issuu.com/saddlefittinginfo/docs/an_historical_perspective_of_respirators__optimize?fr=sYTJlYjEyOTc1NA AirLogic Specialty Hospital Bed. https://www.youtube.com/watch?v=kXGUIlVb7uM&t=72s