What's Next In Inhalation Drug Delivery?

By Scott Danhof and Felicia Hobson, Battelle

Millions of people depend on inhalation drug delivery devices to control chronic conditions such as asthma or COPD, as well as treat acute respiratory attacks and infectious diseases. Many of the devices on the market today have not changed significantly in decades. However, a combination of human-centric design and new sensor, analytics, and data transmission technologies may soon make inhalation devices easier to use, more consistent, and more useful for patients and healthcare providers.

Challenges In Inhalation Drug Delivery

Inhalation drug delivery covers many different types of devices: nebulizers, pressurized metered dose inhalers (MDIs), breath-activated inhalers (including dry powder inhalers), and emerging novel delivery systems. While each device has its own unique combination of device design and drug formulation, all inhalation devices share some common challenges.

• Drug formulation and aerosolization — Inhalation devices must be thought of as combination products. In fact, inhalation delivery is a three-part system consisting of the user, the device, and the drug. Most drugs delivered by inhalation are meant to be inhaled deeply into the lungs, requiring particle sizes of less than 5 microns (μm) and proper aerosolization of the drug. Modification to either device design or drug formulation, or differences in the way patients handle and use the devices, can change the way the drug is delivered to the user.
• Consistent drug delivery — Devices must deliver precise, repeatable doses of the drug, from the first use to the last. This means that the device must be engineered to maintain tight tolerances in the drug delivery mechanism across the lifespan of the device. In addition, the drug must be formulated to remain stable across a range of environments and use conditions. This can be especially challenging for devices that are used outside of the clinical environment, where they may be exposed to wide variations in temperature and humidity, or subject to significant physical stresses. Users do not always store and handle devices as intended; for example, they may leave them in a hot car for extended periods of time or toss them into the bottom of a crowded purse or backpack. Damage to the device or changes to the drug (e.g., clumping of dry powders or chemical degradation of the drug) can change the effective dose delivered or the efficacy of the drug.
• Usability — The majority of inhalation devices are used by patients outside of the clinic environment. Even with clear instructions and training, misuse is common; users may exhale into the device, fail to inhale hard enough, or fail to hold their breath long enough. They may also make mistakes in the assembly or use of the physical device. Misuse means that patients may not get the efficacious dose. Adding to the challenge, home users of inhalation devices often include elderly patients who may have additional limitations in vision, strength, dexterity, or cognitive processing. Even in a clinic environment where devices are used by trained professionals, usability can present challenges for nurses working in busy ICU environments or with fragile populations, such as premature infants.

Each of these challenges presents an opportunity for device manufacturers. Increasingly, devices are incorporating sensor technologies, wireless data transmission and analytics to monitor device performance and add functionality for patients and healthcare providers. At the same time, an increased focus on human factors is making devices more user-friendly.   

Monitoring Device Performance

Sensor technologies can help to solve one of the major challenges in inhalation delivery: ensuring consistency of dosage and device performance. For example:  

• Devices can be equipped with sensors to monitor external conditions, such as temperature and humidity, that could affect drug delivery. If the device senses that it has been exposed to extreme conditions that may impact device performance or compromise the drug itself — such as being left in a hot car all day — an alert mechanism (e.g., a warning light, a change in color, or a digital alert) can let the user know that the device should be replaced. If exposure to extreme conditions introduces potential safety concerns, the device could be equipped with a failsafe mechanism that prevents use.
• Sensors (including accelerometers and pressure sensors) can be used to determine if device integrity has been compromised by dropping, crushing, or exhaling into the device.
• Devices can be equipped to read and monitor expiration dates of the medication being used, track the time the drug has been stored in the device, and provide warnings or compensatory action as medication ages.

Improving Patient Adherence And Patient/Doctor Communication

A combination of sensors, analytics, and data transmission technologies could soon help doctors better monitor patients with chronic conditions and nudge patients towards better adherence. Opportunities in this area could include:

• Dose meters with integrated data transmission could automatically alert patients via an mHealth app when medications need to be reordered — or could even automatically place the order with the pharmacy. Smart devices would be able to monitor both drug expiration and how much of the drug remains in the device, ensuring that the patient always has an adequate amount of non-expired medication on hand.
• Devices with integrated spirometers can measure breath strength or inhalation/exhalation rate as the patient uses the device. This would enable the device to let the patient know if breath intake was not adequate for proper dosage, for example.
• Inhalation devices can be equipped with additional sensors to collect data, including how often and at what times the patient uses the device, whether they are getting an adequate dose, or biometrics, such as inhalation/exhalation rate and breath strength. Some of these capabilities already are on the market: the SmartInhaler uses sensor and data transmission technologies to monitor device usage, and to help patients manage chronic conditions via a mobile app with reporting and reminders. Propeller, a monitoring device that users attach to the inhalator, can automatically log usage on a mobile app, or transmit data to doctors or caregivers.
• Adding analytics allows patients and healthcare providers to look for patterns in device usage and biometrics over time. For example, a smart fast-action inhaler could identify a pattern that shows the patient is using the device with increasing frequency, suggesting a need for more aggressive maintenance therapies. Analyzing patterns in spirometer readings or breathing rate could identify early warning signs that a patient is no longer responding adequately to the current medication regimen. Combining sensors, data transmission, and analytics allows for better monitoring of patients with chronic conditions, and could help them stay independent longer.
• Analytics could eventually be used to collect and analyze data from thousands of patients to look for patterns in device performance, patient adherence, and medication efficacy. Analyzing anonymized data collected from patient electronic health records (EHRs) and device sensors would allow pharmaceutical companies and device manufacturers to better demonstrate long-term efficacy, or to identify potential problems that are too rare to show up in standard clinical testing.

The Importance Of Usability

Adding sensor, analytics, and communication technologies to inhalation devices makes them more useful to both patients and providers. However, as we ask inhalation devices to do more, we need to make sure that we are not also adding complexity that makes them more difficult to use. Manufacturers need to maintain a focus on device usability as well as functionality. Here are some specific actions manufacturers of inhalation devices should take when introducing a new device, or making changes to an old one:

• Conduct user research with people in your end user group. If your device is designed for use in a clinical environment, conduct testing with nurses or nursing assistants who will interact with the device. If the device is intended for use by patients in their home environments, it is important to conduct testing with users who are representative of the range of user types, including users with visual, strength, dexterity, or cognitive challenges. Contextual research and task analysis can identify opportunities to introduce changes in device design or instructions that reduce confusion and make the device easier to use.
• Design for usability by integrating human-centric design (HCD) principles throughout the development process. In particular, manufacturers should look for opportunities to integrate design features that prevent or discourage misuse, such as mouthpiece design that limits the ability of a user to exhale into the device, or sensors that provide a warning if they do. Integrating HCD principles from the earliest stages of device development can help manufacturers avoid unwelcome surprises when they get to required human factors (HF) testing.

Many opportunities await manufacturers that find ways to make their devices more useful and usable with emerging sensor, analytics, and data transmission technologies. New, smart inhalation devices designed with human needs in mind could go a long way toward better meeting the needs of fragile populations and helping people with chronic conditions lead more healthy and independent lives.

About The Authors

Scott Danhof is a Research Leader at Battelle with more than 28 years of product development experience, gained from both program management and engineering roles in a variety of medical device and consumer product development programs. He has spent the last 20 years focused on medical product development with an emphasis on in vitro diagnostic equipment and drug delivery devices.

Felicia Hobson has more than 15 years of experience in the design and development of medical products. As a Senior Systems Engineer at Battelle, she leads design teams from concept generation through detailed design and verification of medical devices. She has spent the last five years focused on drug delivery systems, including inhalation drug delivery devices.