Impact of Material Selection on Sleep Apnea Devices
In addition to being unpleasant to deal with, poor sleep can have significant negative impacts on our overall health and well-being. It increases the risk of accidents and has been linked to various chronic illnesses, including heart disease, high blood pressure, diabetes, depression, stroke, and obesity. Many of these chronic illnesses rank in the top 10 causes for death in the United States.
Research on sleep quality and sleep apnea gained traction in the 1980s. Sleep apnea is a chronic condition where breathing stops during bedrest, leading to a drop in blood oxygen levels. While less than 10% of the population has been diagnosed with clinical sleep apnea, it is believed that 70-80% of people with sleep apnea remain undiagnosed. Considering there are approximately 250 million adults in the United States, there could 75-90 million other adults in the US alone with sleep apnea!
Those diagnosed with sleep apnea often receive a prescription for a CPAP (Continuous Positive Airway Pressure) or Bi-PAP (Bilevel Positive Airway Pressure) machines to support breathing during bedrest. CPAPs provides a constant pressure of air into a mask that covers the nose and/or mouth, while Bi-PAP devise alternate between two pressures for improved comfort. However, these devices can be uncomfortable, costly, and loud, leading to a significant number of them being unused and stored away forgotten in a closet.
The unused CPAP and Bi-PAP machines presented and opportunity during the early stages of the COVID-19 pandemic, when there was concern about hospitals running out of ventilators to treat patients.
Throughout much of 2020, I was part of a COVID response team at Berkeley that included Cal alumni and clinicians at UCSF. A large-scale effort was undertaken to collect donated devices, clean and re0purpose them, and distribute them to low-resourced medical clinics. The project started when there were concerns about ventilator shortages in the US, but later expanded to connect with clinicians across the world who were working with limited resources.
After learning a lot about the various designs and ways to make breathing circuits to reduce aerosolization, I was surprised to learn about a Philips recall on many CPAP and BiPAP machines in June 2021. The recall is based on the use of a particular foam in the devices to reduce noise.
Specifically, the machines used a polyester-based polyurethane (PE-PUR) foam. One of the challenges with selecting an appropriate material for a design is considering the various use cases and long-term material sustainability (i.e., environmental breakdown, fatigue loading, etc.). Polyurethane polymers are prepared through condensation polymerization – meaning water is removed from the solution during formation and the resulting holes in the foam are due to bubbles created during the process. These materials are susceptible to degradation through hydrolysis (the addition of water).
PE-PUR breaks down into smaller pieces of foam particles and this process releases certain chemicals are known to cause serious health issues, including cancer. This degradation process increases at higher temperatures and with greater humidity. Unfortunately, for the user of such a device, the degraded particles or chemicals may be in the airflow path delivered directly into the user’s lungs.
As Philips continues to fix and redesign the recalled devices, we are continuing to learn more about the overall impact of this material design decision on user health. Since the recall was published, over 100,000 medical device reports that include nearly 400 deaths have been released, shedding light on the overall impact of this material design decision.
Sleep is a big multi-billion-dollar market with more ideas and books on how to improve sleep quality and devices to track and medicines to improve sleep quality release every year. For those trying to improve their sleep this is certainly a blow in user trust. This recall serves as a reminder of the crucial importance of considering the long-term sustainability and safety of materials utilized in medical devices.