Siren Care, a California-based technology company that developed smart textiles for remote patient monitoring (RPM) applications, has raised an extra $9m for its series B financing.

Siren raised $11.8m earlier this year, in a round led by Anathem Ventures with participation from existing investors DCM, Khosla Ventures, 500 Startups and Founders Fund. This final close puts the total series B at nearly $21m and included participation by all existing investors as well as new investors Manta Ray, Mighty Capital, Portfolia and David Helgason.

Since the beginning of the year, Siren has seen a drastic increase in monthly subscriptions, up almost 20 times. This increase is reflected across Siren’s user base for patients and ordering clinics. To date, the number of patients with signed contracts has increased by 340% and the number ordering clinics has more than tripled, increasing 216%. One of these ordering clinics is StrideCare, the largest podiatry network in Texas.

Siren’s rapid growth was further fuelled by the increased demand for RPM and decrease in in-person office visits due to Covid-19. This decrease may have helped generate a spike in telehealth services early on by as much as 300-fold but has since flattened, according to the Epic Health Research Network.

“The majority of clinics have seen a 90% decrease of in-person visits,” said Ran Ma, CEO and co-founder of Siren. “Now, more than ever, it’s important for patients to stay connected to their doctors and for doctors to stay connected to their patients. Because Siren allows doctors and healthcare workers to transition to remote monitoring, we have forecasted inbound demand from clinics to well above 400% of expectations. The future of digital healthcare is RPM, giving healthcare providers insights they can’t glean from telehealth alone.”

Siren’s first product is an FDA-registered temperature monitoring sock that connects wirelessly to a software application that serves at-risk populations. With Siren’s product, healthcare practitioners can detect early signs of inflammation in patients at risk of developing diabetic foot ulcers.

RPM capabilities are especially valuable for older patients and those with chronic or underlying medical conditions, such as diabetes, both of which are higher-risk populations for Covid-19. During the first two months of the pandemic, the UCSF’s limb preservation programme showed the number of major amputations for high-risk populations nearly tripled from pre-pandemic levels. In fact, the same study reports that while there was a 32% decrease in operating room (OR) visits for patients, OR rooms still saw a 44% increase in amputations.

“Our patients are some of the most vulnerable and underserved populations,” said Ma. “To further serve our patients, Siren is also rolling out cellular connectivity, which means users can use the product anywhere with access to an electrical plug; no smartphone, wifi or setup required.”

DCM is a global venture capital firm based in Silicon Valley, Beijing and Tokyo with over $4.2bn under management. It has invested in more than 400 early-stage technology companies globally and provides hands-on operational guidance and a global network of business and financial resources.

“DCM has been early supporters of Siren, and we look forward to the company’s growth as it continues to bring its FDA-registered SaaS product to millions of at-risk diabetic neuropathy patients,” said Jason Krikorian, general partner at DCM and Siren board member.

To support Siren’s accelerated product demand, the company continues to grow its team and is still actively hiring. In the past 12 months, the company has brought on several engineering, sales and executive new hires.

Siren was founded in 2015 by Ran Ma, Henk Jan Scholten and Jie Fu and has developed proprietary technology to embed microsensors into fabric, allowing for the mass production of affordable, washable smart textiles. Siren’s products seamlessly integrate into their users’ everyday lives while providing real-time biofeedback to patients and their doctors.

Siren’s first commercial product is an FDA-registered temperature monitoring sock for the early detection of inflammation that leads to diabetic foot ulcers, which costs the health system over $43bn a year and leads to more than 100,000 lower limb amputations annually in the USA.