medical devices – Prof. Klapperich et al.

From the Dalkon Shield to Britney’s IUD

The answer is that the reproductive health of people who can get pregnant is simply not a high enough priority in our society. We settle for good enough when we could have great.

Last week Britney Spears described how under her conservatorship, she was required to be fitted with an intrauterine device and is prohibited from removing it without her father’s permission or the permission of the court. Presumably the goal was to stop Ms. Spears from becoming pregnant with additional children without the express authorization of her custodian.

There are many discussions to have about Ms. Spears’ rights, disability rights, and forced reproductive control. The topic is an intersectional minefield. An amazing discussion with a journalist who is an expert in the field and who has a disability was broadcast on What Next this week. My own thoughts on the subject would require me to use profanity on a blog that I know is read by my program manager at the NIH, and when I resort to profanity, that usually means I am out of comfortable intellectual waters. What I can discuss with a fair amount of authority is the IUD itself, its history in modern times, and how it has succeeded and failed as a medical device for people who want to avoid pregnancy.

If you are my age (49) or older, you first learned about the IUD from horror stories told about the Dalkon Shield. The Dalkon Shield was an IUD invented in the early 1970’s by a gynecologist. Hugh J. Davis, was known as an “intellectually arrogant” person who didn’t take criticism well. So, it wasn’t a very inclusive design team – just one man. He later recruited Irwin Lerner, an electrical engineer, to help him finalize and market the device. The device was rushed to market with insufficient clinical data, and the inventors published their pre-market data without acknowledging their financial interests in the device. They sold the device design to the A.H. Robins company, and Davis continued to act as a consultant and proponent of the device for many years.

At the time, the birth control was popular, but the high levels of hormones in those pills were concerning to many. The side effects of the pill were and still are troublesome and sometimes very serious. In the 1970’s, the available pills nearly 100 times more progestin and 3 to five times as much estrogen as what typical combination pills contain today. Second, and probably more important, is the fact that the A.H. Robbins company did something new that we now take for granted: they marketed the ever loving heck out of that device.

Before 1976, you could invent and patent a new medical device that was meant to be inserted inside a uterus and worn for years at a time with absolutely no federal oversight. As a result, there were no regulations that limited or specified the set of materials to be used to construct the device. So, when the company decided to use a new material for the string, they were able to make that change without consulting any oversight body or performing additional testing to make sure that it was safe.

It turns out that the filament they used for the string was made up of several smaller filaments, like a cable consisting of several smaller wires wrapped together. The little spaces in between the multi-filament string were small enough to give bacteria from the vagina a pathway into the uterus. These bacteria caused infections in people wearing the device that were later recognized as pelvic inflammatory disease. All told, the Dalkon Shield resulted in the injury of hundreds of thousands of women and the documented deaths of at least 18.

The Dalkon Shield disaster is why medical devices are now regulated by the FDA, due to a federal law passed in 1976. Prior to 1976, only drugs were regulated.

As a result of the Dalkon Shield injuries, deaths, and related lawsuits and finally recall, IUDs fell out of fashion in the US. Even though many other non-Dalkon devices existed, the market for IUDs was non-existent. The FDA approved the first new generation IUD in 1984, and that device was available in the US in 1988. Then several years passed before the current crop of modern IUDs began to come on the market from 2001-2016. These are considered Class III medical devices and require pre-market approval before they can be sold in the US.

If a device failure occurs, doctors and patients are encouraged to report the failure to the FDA. Only distributors and manufacturers are required to report. The FDA compiles a database of these failures and though the reporting system is largely voluntary, the FDA does investigate to see if they are part of a pattern. Even the devices containing copper are considered to contain a drug, so must undergo stricter regulations required of drug/device combination products. Most agree that this has led to a very safe but short list of new generation IUDs available in the US. The downside of this enhanced regulation is that many devices approved in other countries that may be more appropriate for some people are not available here. The cost of obtaining FDA approval is too high to make selling in the US market attractive to foreign manufacturers.

The stain of the Dalkon Shield has faded a bit. Younger people are more likely to seek and IUD as a long-term reversible form of birth control. However, the legacy of birth control designed, developed, and marketed by people who cannot become pregnant is still a part of medical care today. All the highly effective birth control methods have undesirable side effects. (Well, maybe not vasectomies, but that requires a monogamous relationship with someone with a good amount of self-knowledge and foresight for maximum efficacy – a rare situation).

Everyone else must figure out what side effects and inconveniences we are willing to deal with to manage when we do and do not want to bear children, if at all. Why is the situation so dire? Why do we take the pill and risk life threatening blood clots at rates that are higher than those that temporarily stopped the use of some vaccines during a global pandemic? The answer is that the reproductive health of people who can get pregnant is simply not a high enough priority in our society. We settle for good enough when we could have great.

One way to make better contraceptive choices a priority is to have people who can become pregnant directly involved with the design and development of contraceptive devices. Involved from the earliest stages. We need the viewpoints of these people as patients and as clinicians, designers, and engineers. And we all need to think just a little more about each other’s healthcare.

Simply, when the people who are the main users of a technology are not consulted in the design phase of that technology, the results for the end users are subpar and sometimes outright harmful.

Diverse teams can save lives.

As for Ms. Spears, it seems clear that her autonomy has been robbed without due process. Since you cannot remove an IUD on your own, she is effectively at the mercy of the state with respect to her ability to bear more children. Medical science may have given her a safer device than was available in the 70’s, but disability law has kept her rights in the 1920’s.

You are going to stick what up my nose? [Update with TikTok links!]

These are not your grandmother’s nasal swabs.

To continue our recent discussions on disease testing, today we’re talking about swabbing and swabs.

Perhaps you’ve been lucky enough to experience a swab test firsthand. As testing becomes more widespread, we are all likely to have a nasopharyngeal swab taken for a COVID-19 test. When I was a child, maybe around seven, I remember going to the doctor’s office to be tested for influenza, another virus that replicates in the nasopharynx. When the nurse first pulled the slim, wire swab out of the packaging, I thought no way. No way that daunting, 5-cm long wire will fit up my nose. Sadly, I was mistaken. I won’t lie – it wasn’t the most pleasant experience. The tickling sensation lingered in my throat long after the swab had been removed. I still felt it even after my results had come back – negative, luckily for me. Just a common cold!

This kind of swab is referred to as a nasopharyngeal swab, which I learned many years later. Nasopharyngeal swabs are used to collect samples from the back wall of the nasopharynx (hence the name), which is where the nasal passages meet the throat. Other common swab tests include nasal swabs and oropharyngeal (throat) swabs.

Nasal swabbing vs. nasopharyngeal swabbing from link.

Swabs are made out of a number of different materials. Since the nasopharynx is much farther back in the nasal passage, the swab needed to get there must be longer and somewhat bendable. The swabs used for sampling the nostrils and throat are generally stiffer and shaped like long Q-tips. The materials that comprise the tips of these swabs are different, too. If you are trying to get material out of the oral or nasal cavities for testing, you need a surface at the tip that is good at grabbing that material. It is also important to be able to wash the material off and into the testing solution when needed. Thus, regular cotton is often not suitable.

In terms of COVID-19 testing, the swabs you’re most likely to encounter are nasopharyngeal and nasal swabs. Nasal swabs are less invasive. The swab only needs to be inserted 1 cm into the nostril and rubbed along the septum for a few seconds. Nasopharyngeal swabs, on the other hand, require a longer swab, which is inserted about 4-6 cm back into the nostrils (about half-way between the entrance to the nares and the base of the ear). The swab is then rotated inside the nasal passages and left in place for a few seconds to absorb the sample.

Check out Dr. Klapperich demonstrating anterior nares swabbing (AN) here and here on TikTok!

More fun with nostril swabbing! pic.twitter.com/3TyKUbqogu
— Cathie Klapperich (@DrKlapperich) July 25, 2020

Swabs made to sample the nasopharynx usually have a tip made of plastic foam, or another material with lots of surface area. These are called “flocked” swabs. Only a few factories in the world make these swabs, which is why you regularly hear about swab shortages for testing. Sadly, using a version of a regular Q-tip would not be a suitable replacement. There are a number of innovative groups around the world looking for ways around this shortage. Some of them include 3D printing swabs made from medical grade plastics. All swabs that are used to apply topical medications or collect fluid samples are considered Class I medical devices by the FDA.

In studies comparing the sensitivity of nasal vs nasopharyngeal swabs for influenza, nasopharyngeal swabs were found to be slightly more sensitive (94% vs. 89% sensitivity). This means that for the flu, a nasal swab sample will lead to a false-negative test result more often than a nasopharyngeal swab. But despite their inferior sensitivity, nasal swabs are simpler and useful for “self-swabbing”- taking your own sample to send or have delivered to a testing facility. According to the most recent update to the CDC’s COVID-19 specimen collection guidelines, nasal swabs taken by a healthcare worker or via self-swabbing are acceptable if taking a nasopharyngeal swab is not possible. But these guidelines are sure to change as more information comes out about how swab type affects false-negative rates for COVID-19. Early indications are that nostril swabs are not as good as nasopharyngeal swabs for this new virus.

Are pulse ox devices racist?

Black communities are already faced with substandard healthcare, so when a medical device that monitors vital signs, such as the pulse ox, is developed without Black and dark-skinned people in mind, it is much more than just a design flaw.

In our last blog post, we went into detail about pulse oximeters and their mechanism of action. As we touched on briefly, blood oxygen measurement varies greatly from person to person since it relies on light passing through tissue, which behaves differently depending on a number of biological factors. This seemingly objective method actually serves as an example of biomedical technology that fails to account for all of these factors.

We couldn’t find a single stock shot of a pulse oximeter being used on someone with dark skin at bigstock.com, we checked.

Low oxygen saturation levels, the type of sensor in the device, gender, and skin color have all been shown to cause errors in pulse oximetry, but the discrepancies relating to skin color may be the most glaring. Studies and extensive anecdotal evidence from clinicians have shown that any errors due to low oxygen saturation were more dramatically skewed in Black patients when compared to their white counterparts. More specifically, at oxygen saturation levels below 80%, pulse oximetry measurements are significantly overestimated in dark-skinned patients.

At saturation levels below 80%, patients begin to experience oxygen deprivation to the point of organ failure (hypoxia). So, if a pulse ox reading is overestimated in a dark-skinned patient, a healthcare professional could easily miss the onset of hypoxia. This limitation of the technology is critical especially now, during the COVID-19 pandemic, which is killing Black people at a rate three times higher than that of any other racial group in America. Black communities are already faced with substandard healthcare, so when a medical device that monitors vital signs, such as the pulse ox, is developed without Black and dark-skinned people in mind, it is much more than just a design flaw.

As engineers, we are taught that device design of any kind cannot be successful unless the product meets all necessary requirements. Just like designing a building requires every environmental condition to be taken into consideration, designing a medical device requires every kind of person to be taken into consideration.

Nevertheless, in the 1980s, when the pulse ox first underwent FDA screening, accuracy and calibration testing was conducted primarily on light-skinned people; this has not changed since then. Despite the major functional disparity, the FDA has yet to require further research and testing dedicated to developing a pulse ox that produces accurate measurements on darker skin.

To pulse ox, or not to pulse ox?

Another day, another COVID-19 discussion…

With each passing week, we are learning more and more about how to deal with this pandemic, both individually and as a community. We are now well-versed with preventative measures like washing our hands frequently and wearing masks, but what happens if you actually start feeling sick? While the symptoms of this viral infection are varied, they usually include high body temperatures, dry cough, and shortness of breath. Most of us have a thermometer at home, with which we can easily diagnose abnormal temperatures. But, is that enough to detect the early stages of a COVID-19 infection?

Pulse oximeters (pulse ox) are getting a lot of attention right now. If you have ever had surgery or if you have a respiratory condition like asthma, you likely know that a pulse oximeter is the little medical device that clips onto your finger and informs your doctor of your heart rate and how much oxygen is in your blood. Monitoring blood oxygen levels has been critical for COVID-19 patients because a drop in the amount of oxygen in your blood indicates the need for more aggressive interventions. Since you can buy a pulse oximeter at the drugstore, many people are wondering if they need one at home. So why exactly do respiratory issues warrant the use of a pulse oximeter?

When your lungs are functioning properly, around 95% – 98% of the blood in your arteries should be “oxygenated,” or carrying oxygen. Your blood carries oxygen with the help of hemoglobin, a protein that has the ability to bind to oxygen molecules. Hemoglobin is what makes blood a great transporter of oxygen from your lungs to the other organs in your body. Without oxygen, your organs cannot function because they rely on a process called oxidative phosphorylation, which uses oxygen to produce the energy that drives all organ functions. When your lungs are compromised, like they are during a COVID-19 infection, they are unable to efficiently take oxygen in from the air and pass it into your bloodstream. As a result, your other organs don’t get enough of it to do their jobs. This condition is called hypoxia.

*The circulatory system. Red vessels are the ones that carry oxygenated blood.*

Now, let’s get back to the pulse oximeters. A pulse oximeter measures the percentage of oxygen saturation in your blood by shining both a red light and an infrared light into the top of your finger. The bottom of the device has a sensor that detects the amount of light that passes all the way through your finger. You can visualize this mechanism by doing a quick little science experiment on yourself. Turn on your cell phone flashlight, put your finger on it, and see what happens. If red light shines through, your blood is probably not deprived of oxygen. Good for you! Oxygenated blood absorbs every wavelength of visible light except red, which is why the red light can go all the way through your finger. Deoxygenated blood, however, is really good at absorbing red light. Now, we can see how the pulse oximeter takes advantage of these properties of blood to give a measurement of oxygen levels.

So, why is infrared light also necessary? Blood vessel width varies from person to person, making the volume of blood in the vessels vary as well. Only using red light would result in misleading oxygen levels because the readings would be affected by these varying blood volumes in different people. For that reason, infrared light is used alongside red light to normalize the measurement and adjust it to each user’s body. Infrared is not well-absorbed by either oxygenated or deoxygenated blood, so it is a good baseline comparison measurement. The pulse oximeter calculates the ratio of absorbed infrared light to absorbed red light to get the percentage of blood saturation. In oxygen-rich blood, the low level of infrared absorption divided by the similarly low level of red absorption results in a ratio close to 1, which is equivalent to a percentage close to 100%. As blood oxygen levels decrease, this ratio also decreases because the red light absorption (the denominator) increases while infrared absorption stays relatively constant. Readings below 92% indicate the beginning of a hypoxic state.

The ability to detect hypoxia is what makes pulse oximeters critical for COVID-19 patients. Healthcare professionals who are currently treating these patients are finding that oxygen levels can drop well below 92% before patients have any trouble breathing. When a patient does finally go to the doctor complaining of shortness of breath, their infection and hypoxia may be very advanced. Often, symptoms like fever and fatigue can also mask early hypoxia symptoms. It is easy to get used to the mild shortness of breath or pass it off as fatigue while blood oxygen levels continue to drop. For these reasons, some doctors are suggesting that everyone should get a pulse oximeter to use at home so the onset of hypoxia can be caught early.

A big disclaimer that many physicians are making however, is that pulse oximeters should be used at home along with thermometers and calls to your doctor. There are still many cases in which COVID patients do not present with any hypoxia, but have high fever and the telltale dry cough. So, blood oxygen level, while helpful, is not the only metric used in diagnosis.

So, should you buy a pulse oximeter? To put it plainly, it’s really up to you. If you are sick, you called the doctor, and they said you’re not sick enough to go to the hospital, it may be helpful to have one and monitor your own blood oxygen so you know if you ever do need to go in. You may want one in that situation just to keep your peace of mind. Even if you aren’t sick, and just want to be prepared, it definitely can’t hurt to get one. However, all the stories about hypoxia going unnoticed paint a scary picture. It’s important to remember that, if you can’t get your hands on a pulse oximeter right now since the demand is high, it’s not the end of the world. The vast majority of COVID patients are able to get diagnosed and get to the hospital in time if necessary just by calling a doctor. So, you really don’t need to buy that $200 pulse oximeter you found on Amazon. You can find them for about $30 at your pharmacy, but if they’re sold out, don’t panic! Just keep washing your hands, keep that 6-foot distance, and if you are sick, call your doctor. Here at the blog, however, we are device geeks – so any opportunity to have a new medical device around the house we’ll take!