Achieving New Heights in Subcutaneous Drug Delivery with Liquid Flow Sensors

The COVID-19 pandemic has accelerated the push for digitalization and patient-centered approaches in healthcare. The growing demand for self-treatment and advances in biotechnology and precision medicine offers new meaning to smart drug tracking.

Advances in subcutaneous drug delivery can be achieved via the utilization of miniaturized liquid flow sensors in wearable devices. This would provide advantages for patients, doctors, and nursing staff, as well as pharmaceutical companies and the healthcare system.

Digital drug delivery solutions, such as digital pills, smart injectors, and infusion pumps, are transforming the medical and pharmaceutical industry and rapidly enhancing self-care.

As changes in demographics cause an increase in patients with chronic diseases, the demand for more digitalized home care therapies is evident.

Digitalization trends have been relieving the healthcare system that was suffering from a nursing shortage even before the COVID-19 pandemic. However, since its onset, the shift towards self-administration in healthcare has accelerated.

Keep moving: Thanks to the flow sensor in your medical patch

Keep moving: Thanks to the flow sensor in your medical patch. Image Credit: Sensirion AG

COVID-19 Accelerating Patient-centricity

The COVID-19 pandemic has caused challenges for hospitals worldwide. Scheduled therapies and surgeries have been postponed because of a shortage of beds, overburdened staff, and fear of infection.

Patients became cautious about visiting doctors’ offices and hospitals, using telemedicine appointments when possible.

However, the healthcare system requires a rethink. Minimizing the number of hospital visits for routine checks and treatments of patients that are chronically ill is critical, as well as enhancing the efficiency of medical staff to decrease overall treatment costs.

Digital helpers can serve a vital function by improving collaboration between doctors, nurses, and management, offering additional safety by monitoring drug delivery and treatment, facilitating more data-driven interpretation of treatment plans, and offering a quicker response to changing patient conditions.

However, it is assumed that the effect of COVID-19 on the healthcare system will continue to accelerate and relieve obstacles to the development of modern healthcare solutions.

New portable or wearable designs provide the opportunity for patients to safely manage their conditions in their own homes, with more customized and flexible treatment options available due to remote monitoring.

From a macroeconomic perspective, digitalization is linked with reduced prices for electronic components. This justifies the pricing of new equipment, enabling medical device manufacturers to innovate and enhance designs, thus adding new value to their products.

Directly documented feedback about ongoing treatment for patients and doctors is one example. For example, the electronic health record (EHR) of hospital treatments and diagnoses is also likely to become mandatory in care someday.

Another factor is the increasing trends from health insurers. Pharmaceutical and insurance companies have been moving towards proof of use or effectiveness of therapy (e.g. continuous positive airway pressure devices - CPAPs) and drugs, in order to receive full payment or reimbursement.

For instance, smart inhalers measure the inhaled flow profile and dose actuation, which proves whether the drug was taken properly. In general, digital data solutions like this are helping to develop the Internet of Medical Things (IoMT) to benefit patients, caregivers, and payers.

Biopharmaceuticals as a Driving Force

Developments in biotechnology precision medicine for personalized or participatory patient care influence trends in self-care. The utilization of high-value drugs allows the treatment of diseases to be more targeted and to cause fewer side effects relative to conventional medicines.

Unlike chemically synthesized drugs, biopharmaceuticals are comprised of complex structures from microorganisms, plant extracts, or mammalian cells. For instance, they include proteins that trigger the formation of blood cells, insulin, or antibodies that prevent the growth of cancer cells.

Additionally, these high-value drugs provide opportunities to cure other diseases that were previously untreatable, such as diabetes, cardiovascular diseases, autoimmune disorders, or neurological disorders.

However, because they must be administered parenterally, biopharmaceuticals are still not well accepted. Due to the large size of the molecules, the most prevalent mode is intravenous infusion. Large-volume administration requires clinical support, which means that therapy costs are added to already high production costs.

A further disadvantage is the complicated handling that is required of high-volume and viscous formulations, and devices for conventional drug delivery are not capable of this.

Some new drugs demand specific dose timing regarding starting time or flow rate, while others are in a lyophilized state and need reconstitution. Novel drug delivery mechanisms are needed to address these challenges with administration.

Connected Large-Volume Injectors

Large-volume injectors (LVIs), also referred to as patch pumps, on-body delivery systems, or wearable drug-delivery devices, have been used for a few years to replace intravenous infusion with subcutaneous injection.

The application is less painful, and their use allows the treatment of chronic disorders to take place at home by patients themselves. Prefilled drug-device combinations offer a reliable and convenient option instead of outpatient treatment.

In addition to allowing patients to receive treatment at home, wearable smart injectors allow the real-time remote monitoring of treatment and reduce both cost and effort for patients, insurers, and healthcare providers.

Due to the high volumes and viscosities, biopharmaceutical delivery must be controlled, confirmed, and tracked. Automatic drug-delivery systems with flow rates between 1.5 to 300 milliliters per hour provide the continuous delivery of drugs from a vial over a specified period.

Additionally, LVIs enable lyophilized drugs that must be delivered by the user soon after reconstitution to be filled at the point of use.

Challenging Device Design

The market for LVIs for non-insulin drugs is predicted to grow quickly within this decade. More than 50 wearable products and 10 drug-device combinations with high storage capacities are either already commercialized or in the process of development.

The drug-delivery industry faces many challenges related to the design of these devices, regardless of whether the devices include medication or not. These challenges include the optimization of usability, the improvement of handling viscous formulations, and the minimization of the costs of the devices.

As a result, most LVIs are made of a combination of disposable and reusable parts, which makes sense in environmental terms. The motor, battery, connectivity module, readout electronics, and display are reusable, while the drug compartment, patch, needle, and wetted sensors are disposable.

LVIs may also be designed for already existing drugs. While a patent on a drug expires, such as Amgen’s Neulasta in 2015, the availability of a new on-body injector can result in the drug’s lifetime being extended, as well as the related business for Amgen.

This means that new revenue streams can be produced from new lifecycle management strategies in the medical and pharmaceutical industries.

Miniaturized, Cost-Effective, Disposable Sensors

As there are various biopharmaceuticals with different properties, designers of LVIs must individually guarantee that the devices function reliably and precisely and are easy to use. Until now, these devices have employed audio, visual, or tactile indicators for needle positioning and on-body attachment.

The detection of failures such as occlusions is possible to some extent, but only in an indirect manner at present. This means that the possibility of false positives persists.

More importantly, these devices offer direct flow measurement and delivered volumes as well as bidirectional measurement capability, which conventional sensors do not provide.

The sensor solutions offered by Sensirion enable the integration of miniaturized, disposable liquid flow sensors into LVIs for the real-time control, confirmation, and tracking of subcutaneous drug delivery.

LVIs facilitate precise dosing regarding flow rate and administered volume, as well as the automatic detection of failures, including occlusion or air-in-line, economically and directly.

When these next-generation sensors are integrated into a connected LVI, they enable the patient to monitor administration using a smartphone app. They also allow communication, such as telemetry, with stakeholders that are involved in the care of the patient, such as parents or other relatives.

Doctors, nursing staff, pharmaceutical companies (for research), and health insurers (for proof) can receive updates and metrics regarding drug administration and device status.

Programmable features can alter or optimize the process of subcutaneous drug delivery. If an injection device displays issues, a flow sensor offers peace of mind to patients and their relatives.

Put simply: implementing a tiny smart sensor improves therapy outcomes, patient adherence, and quality of life. Miniaturized liquid flow sensors address the above-mentioned market trends and provide a great value-to-cost ratio.

In summary, miniaturized liquid flow sensors allow LVIs to:

  • Directly and bidirectionally measure the flow rate for real-time confirmation of the administered fluid volume
  • Monitor the performance of the system and guarantee the reliable detection of failures
  • Provide connected solutions for monitoring and tracking therapies by all stakeholders

Sensor, Pump, and Beyond

In the design of LVIs, a holistic perspective is advised regarding the liquid flow sensor and the pumping mechanism.

Medical device manufacturers should seek the best possible combination to identify the ideal design of the flow control system regarding performance, size, manufacturability, ease of integration, and cost.

Traditionally, the pump technology is chosen first, and this is frequently independent of the flow sensor, particularly when there are unique requirements and related intellectual property of the device manufacturer involved.

Using a previously selected pump in combination with a liquid flow sensor may be difficult, particularly when the performance of the pump needs to be improved, as the sensor must deliver failure detection and resilience.

This may be made more challenging by the specific working principle, flow profile, fluidic connectors, and mechanical design of the pump.

Sensirion has conducted a design study involving the assembly of a small-footprint liquid flow sensor with a single-use micropump acquired from Quantex Arc.

This resulted in a highly compact flow controller that delivered a steady flow in different flow regimes with very little energy being consumed.

Sensirion’s technology also works well with pumps from other manufacturers. As this was only a concept study, there is room for further improvements and customizations, also considering the requirements of different devices.

Test Design

The lightweight in-line pump CS-3 was utilized in this study, equipped with barbed inlet and outlet connectors for easy fitting to tubing. This makes it well-suited to precise microdosing at flow rates of up to 100 milliliters per hour.

Taking up only 0.5 cm3 of space (12 x 6 mm), Sensirion’s liquid flow sensor stands out due to its millisecond-fast response times and direct as well as bidirectional flow rate measurement.

Drug delivery patch.

Drug delivery patch. Image Credit: Sensirion AG

This information has been sourced, reviewed and adapted from materials provided by Sensirion AG.

For more information on this source, please visit Sensirion AG.


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