Test & measurement
Flow measurement in smart inhalers for connected drug delivery
With each inhalation through the inhaler, the device delivers a specific amount of medication to the lungs. However, when it comes to proper inhaler use, misuse is the norm. It is well documented that patients often have
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problems adopting the correct inhaler technique and thus receive insufficient medication. This applies equally to both metered dose inhalers (MDIs) and dry powder inhalers (DPIs) and leads to poor disease control and increased healthcare costs, either as a result of uncontrolled disease, increased drug utilisation for relief medication, preventative therapy or emergency department visits. This remains a common problem in both asthma and COPD. Global annual costs associated with asthma
and COPD management is substantial from both the healthcare payer and the societal
nhalers are among the most commonly used devices for treating respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD).
Figure 1. Inhalation flow profile showing the calibrated flow rate in standard liters per minute (l/min) versus the inhalation time in seconds (s).
perspective. Research findings show that healthcare spending for an uncontrolled patient is more than double that of a controlled patient. Studies have also found that patients make
at least one mistake during inhaler drug intake as often as 70 per cent to 90 per cent of the time, resulting in only seven per cent to 40 per cent of the drug being delivered to the lungs The two biggest and most serious errors when using an MDI are both related to patient inhalation. The first error is related to the coordination between inhalation and triggering the dose release of the inhaler. Even a short delay can result in only 20 per cent of the medication being delivered to the lungs. The second most significant error is not breathing deeply enough, which can cause another ten per cent less medication to reach the lungs. The opportunity for technological innovation to reduce these common errors by measuring patient inhalation airflow through the inhaler device is already available today and allows for increased drug delivery efficacy, improved medication adherence, reduced healthcare costs and, ultimately, improved patient outcomes.
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Why Measure the InhalatIon FloW ProFIle?
As discussed, the two biggest and most serious errors in using inhalers are related to patient inhalation. By measuring the inhaled airflow through the inhaler, and additionally registering the point in time when the drug is dispensed for MDIs, allows information on whether the drug was released within the optimal window of the inhalation cycle to be accurately determined (see Figure 1). This dose-trigger timing versus flow correlation is one critical parameter to understanding if the drug carrying flow reached deep into the bronchia and achieved the desired high lung deposition (see Figure 2). The second critical parameter is the inhaled
airflow profile. Borrowing from spirometry, several parameters can be derived from the inhalation airflow profile that provide insights into each patient’s inhalation:
Depth and length of inhalation Entire exhalation before inhaling Slow inhalation according to instructions
Lung function and its development over time
March 2022 Instrumentation Monthly
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