Citation: Welch B, “Systems Engineering for Complex Portable Drug Delivery Device Development”. ONdrugDelivery Magazine, Issue 66 (Apr 2016), pp 8-11.

Bill Welch explains how a systems-engineering approach provides an efficient method of developing smaller, smarter and more complex inhaler devices. 

As the demand for complex, portable drug delivery devices continues to grow, reducing risk and increasing efficiency during the development of these products should be paramount.

“While adopting an SE approach to product development does not totally eliminate development risk, it does reduce risk significantly…”

Taking a systems-engineering (SE) approach to development provides a holistic, organised and deliberate method for identifying as well as reducing both patient and business risks early in the process.

The latest inhalers on the market reflect the relentless industry-wide drive towards smarter, smaller and more portable drug delivery devices. To ensure reliability and repeatability, however, such complex devices demand a greater number of requirements, as well as more testing and validation during their development, than do the larger, simpler devices of previous decades. In turn, they also carry with them greater technical and schedule risk. Applying systems engineering to the development of these devices addresses the whole device system and determines the following features:

  • All subsystems (a discrete selection of components that work together to per form a function) that make up the full system
  • Each subsystem-to-subsystem dependency
  • All of the rules that will need to be drawn up in order for the subsystems to work together, or integrate
  • The order in which those rules will be drawn up so that subsystem integration occurs correctly.

Figure 1: Key steps in the process for using a systems-engineering approach.

This approach differs from the traditional linear product development approach, typically in that it breaks the whole product idea into subsystems and – beyond simply establishing requirements for those subsystems – devises an order in which each subsystem must be defined. It also determines which dependencies between subsystems are needed for proper operation. Systems engineering requires both subsystem-specific engineers and the overall systems engineer, who focuses on establishing the requirements for the interactions and integration of the subsystems – that is, what makes the whole system work together.


To kick off the SE process for a complex, portable inhaler, the user and stakeholder needs must first be determined by the client (the device company), then communicated to the product development (PD) team. Once the PD team has a firm grasp of what the client wants, the team members will typically brainstorm ways in which those wishes can be fulfilled. Next up after brainstorming are the crucial steps shown in Figure 1.


The SE approach can be illustrated using a hypothetical complex portable drug delivery device: an automatic-dosing albuterol inhaler, which represents an upgrade of the traditional manually dosed albuterol inhaler. This mechanical upgrade features automatic dosing triggered by the user’s inhalation as well as a dose counter that tracks the number of doses that have been administered.

In early brainstorming, the team decided the order of operation would occur as shown in Figure 2.

Several subsystems are present in the entire device, including canister design and drug formulation, user interface, drive-mechanism cocking, drive mechanism (spring), stem and opening, canister activation, dose-counter mechanism and an inhalation-activated trigger. Rather than jumping right to the creation of a total-product concept that incorporates all of these subsystems at once – thereby making it difficult to define what is critical about each subsystem and its components – the SE approach first establishes the individual subsystems, determines the links between them, prioritises those links, defines and tests in a logical order, and then finally, integrates the subsystems.

Figure 2: Order of operation for upgrading an automatic-dosing inhaler device.

Figure 3 depicts the links that have been established between the subsystems of the hypothetical automatic-dosing inhaler, along with how the links have been prioritised.

As is illustrated, the PD team has determined that defining the requirements for the canister design and drug formulation are the most important, followed by the stem and opening from which the drug will exit the canister.

These two subsystems and their interaction can then be studied on their own, independent of other variables, such as the drive mechanism. Subsystems 1 and 2 are used to define the requirements for Subsystems 3, 4, and 5.

Finally, Figure 4 illustrates the structured, deliberate manner in which integration of the inhaler’s subsystems  occurs.

Figure 3: The links between the subsystems in order of priority


While adopting an SE approach to product development does not totally eliminate development risk, it does reduce risk significantly. By defining each subsystem and specifying the order in which those subsystems must be characterised, troubleshooting during subsystem integration becomes more efficient and straightforward. Engineering teams can work backwards through the system, if needed, to determine where gaps may have occurred.

Patients, ultimately will benefit from a product that does not cause harm and that functions as intended while the manufacturer will benefit from a timely product launch.

“Learn early and inexpensively” is a useful mantra here: by focussing on subsystem- and system-level requirements during the proof-of-concept phase, the team will set up a solid foundation for the moreexpensive development work that follows.


Although SE for complex portable drug delivery devices demands a greater expense up front, it is well worth it in the long run. A less-seasoned drug delivery device manufacturer that has no experience with problematic late-stage PD issues, for example, may not immediately understand the value of the SE approach. However, medical device makers should have faith that the extra up-front costs required by SE will pay off in reduced risk, more timely development schedules and greater efficiency.

Figure 4: Integration of the inhaler’s subsystems.

“Healthcare products continue to shrink, feature greater connectivity and grow more complex. These trends are not going away, and the SE approach to product development is the best choice for firms creating these devices … reducing user, patient, product, financial and schedule risk and improving PD lifecycle efficiency…”

Medical device makers that understand SEs’ high value should listen carefully to the language potential vendors use. Such SE terms as subsystem, integration, subsystem interactions, and system-level requirements and specifications indicate that the vendor’s SE approach is sound and credible.

Additionally, when asked about how it approaches proof of concept, the vendor should be able to explain that its engineers work out the functional aspects of the device in question “on the bench” first, rather than jumping straight to a fully integrated product concept.


Healthcare products continue to shrink, feature greater connectivity and grow more complex. These trends are not going away, and the SE approach to development is the best choice for firms creating these devices. Delivery device manufacturers can stay current and competitive by taking the SE approach to product development for reduced user, patient, product, financial and schedule risk and improved PD lifecycle efficiency. Those who don’t, may find themselves falling behind.