Manufacturing and Sterilization for COVID-19

Design, development, prototyping, testing, and validation to help win the fight

Disposable Stethoscopes

Contents

Need Exploration and Identification

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was first identified in December 2019 in Wuhan, the capital of China’s Hubei province, and has since spread globally, resulting in the ongoing 2019–20 coronavirus pandemic. As of 14 April 2020, more than 1.94 million cases have been reported across 210 countries and territories, resulting in over 123,000 deaths(https://coronavirus.jhu.edu/map.html). The pandemic has resulted in travel restrictions and nationwide lockdowns in several countries.  With the sudden surges in patient volume during the COVID-19 outbreak, closing of borders and restrictions on international shipping, and temporary shutdown of manufacturers for medical supplies, personal protective equipment (PPE), ventilators and associated consumables, as well as many other medical supplies have become a scarce resource.

Existing Solutions

Market Analysis

  • As of 4/20/2020, there are 2,458,150 confirmed cases of COVID-19 worldwide
  • The stethoscope is utilized by countless healthcare personnel in various settings and has been shown to harbor potentially pathogenic bacteria and transmit bacteria to human skin.9 Cleaning the plastic diaphragm with standard cleaning solutions found in the healthcare setting can decrease bacterial load.9 Respiratory syncytial virus (RSV) has been shown to survive on stethoscope diaphragms and eradicated with standard alcohol wipes.
  • “Community” stethoscopes used by multiple individuals and sharing of stethoscopes should be avoided, if possible, in the midst of this pandemic in order to prevent nosocomial spread and potential self-inoculation.
  • Supplies for disposable stethoscopes are limited. Many locations have shipping dates in July of 2020 and stores are out of stock.

Alternative Solutions

  • Operational
    • Sterilization and Reuse (from Tom Richard, Director of Institutes of Energy and the Environment)
      • If biological validation is needed, virologists will need to create a test for viral inactivation due to the complex design of the stethoscopes
      • Pulsed UV system would not be appropriate if the interior surfaces such as the tubing were potentially infectious. There is also possible issues with transporting the UV system to an appropriate location due to its size
      • Vaporized hydrogen peroxide (VHP) can possibly be used because the interior surfaces like the tubing have relatively simple physics. The possible success of VHP can be measured by leaving some disposable stethoscopes with the N95 masks in the VHP room and testing if there is any material degradation after running a few cycles
      • Liquid disinfectants (soak, flush, rinse protocol) is another option. A BSL-3 facility is necessary to verify the virus kill on presumed contaminated stethoscopes and work must be done by their trained staff.
      • Red-bagging stethoscopes with dates and creating a cycle of letting the virus inactivate (without disinfectant process) before reintroducing them to the wards
    • Novel Design

Concept Screening

  • Clinical
    • Risk of cross-contamination with traditional stethoscopes is high:
      • Datta P, Kaur M, Rawat S, Gupta V, Chander J. Stethoscope, “the friendly foe” – A study to evaluate bacterial contamination of stethoscopes and disinfection practices. J Infect Dev Ctries. 2018;12(10):887-893.
      • Tschopp C, Schneider A, Longtin Y, Renzi G, Schrenzel J, Pittet D. Predictors of Heavy Stethoscope Contamination Following a Physical Examination. Infect Control Hosp Epidemiol. 2016;37(6):673-679.
    • 3-D printing disposable stethoscopes: done by students at Lafayette College (https://news.lafayette.edu/2020/04/07/engineering-division-creates-medical-equipment-with-3d-printers/)
    • Spaulding criteria:
      • Different levels of sterilization needed to different classification of medical devices:
        • For non-critical equipment (devices that only touch intact skin or don’t directly touch people) (EKG machines, oximeters, bedpans, urinals, etc.) – clean followed by low-level disinfection
        • For semi-critical equipment (devices that touch non-intact skin or mucous membranes without penetrating) (respiratory therapy equipment, anesthesia equipment, etc.) – clean followed by high-level disinfection
        • For critical equipment (devices that enter sterile tissues) (surgical instruments, implants, biopsy instruments, eye/dental equipment, etc.) – clean followed by sterilization
      • Stethoscopes considered “non-critical equipment” so only low-level disinfection needed
        • Ethyl or isopropyl alcohol (70-90%)
        • Sodium hypochlorite (5.25-6.15% household bleach diluted 1:500 provides >100 ppm available chlorine)
        • Germicidal detergents (Phenolic, Iodophore, quaternary ammonium)
  • Engineering Requirements Derived from Previous Designs
    • The stethoscope needs to amplify sounds to at least 20 Hz. Below that, the human ear cannot hear it.
    • In the diaphragm, the person’s body sounds vibrate and travel up the tube and transmit the sound.
    • No regulations found
    • Acoustic ranges of stethoscopes (Weiss D, Erie C, Butera J, et al. An in vitro acoustic analysis and comparison of popular stethoscopes.Med Devices. 2019;12:41-52.)
    • A 3-D printed, low cost, open access stethoscope – $2.40 (Pavlosky A, Glauche J, Chambers S, Al-Alawi M, Yanev K, Loubani T. Validation of an effective, low cost, Free/open access 3D-printed stethoscope. PLoS One. 2018;13(3):e0193087.) https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193087
      • Effective at a range of 86 – 5000 Hz (similar to Littmann Cardiology III)
  • Guiding Engineering Considerations
    • Rapidly manufacturable: When drafting concepts of replacement stethoscopes consider the available manufacturing methods and resources your team may have access to. Work with manufacturers to create concepts that minimize part production time and assembly time; reducing both variables will ultimately increase the speed of production and ensure any new designs are well situated in local manufacturing and supply chain contexts.
    • Low-cost: Current disposable stethoscopes have an incredibly low price-point on the market; as such it can be difficult for manufacturers to make the business case justifying entering this market. Using common off the shelf components and considering material costs in the early stages of concept generation can help reduce overall product costs.
    • Minimize number of parts: Minimizing the number of unique parts can minimize assembly time, thus reducing labor costs and the overall cost of the product. Further, minimizing parts helps designs be more robust to part failure or quality control issues.
  • Regulatory
  • (IP) – Google patent search

Strategic Development

  • As an operational strategy, the respective institution should exhaust all existing channels to procure the disposable stethoscopes. Existing stethoscope products are preferred due to regulatory requirements and extensive testing.
  • If inventory is minimal and existing products cannot be obtained, manufacturing stethoscopes with published specifications can be considered with the following considerations:
  • Depending on the burn rate of the stethoscopes, if additional sourcing is required, discussion can be made with respective infectious control of the institution to determine if sterilization of the stethoscopes is an option.

 

@CDCgov

@Surgeon_General

@PAHealthDept

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