Sensohaler: Inhaler compliance monitor
Sensohaler is an exciting new technology that monitors key performance characteristics of an inhaler, providing valuable feedback to the user, clinician, doctor or provider, consequently promoting correct use.
Over recent years there has been broad discussion regarding user compliance of various medical products with numerous ideas and potential solutions to improve ease of use and product efficacy. Which costs more – a simple, unintelligent inhaler that is often used incorrectly and consequently does not perform as efficiently as intended; or an intelligent inhaler that has various features to increase user compliance? It’s clear that the simple inhaler costs less to produce – but the real cost is the total cost to treat the patient, which is unfortunately likely to require many inhalers over a period of months or even years. Recent studies have demonstrated that patients can be treated more efficiently with a delivery device that is being used as intended – clearly benefiting the patient and potentially saving costs over the complete treatment period.
Our technology uses advanced acoustic analysis to measure/monitor key performance characteristics accurately during the inspiratory manoeuvre, such as flowrate, inhaled volume, peak inspiratory flowrate, together with confirmation of events such as the firing of a breath actuation mechanism (BAM) and delivery of formulation through the air path of the inhaler.
How does it work?
Acoustic signals are recorded using an inexpensive condenser microphone, then analysed using a set of algorithms that are tailored for a particular inhaler type.
This technique is completely non-invasive, having no effect upon the airflow or the aerosolisation performance of the inhaler, and (if required) could be imperceptible to the user. There is a vast amount of information available in the acoustic signal produced during the use of many products – particularly inhalers. If you’re able to physically hear an event, it’s possible to characterise it and detect it using inexpensive electronics. The processing power available for very little size and cost enables complex data analysis to be performed quickly and efficiently. This allows us to design a device that has minimal effect upon the form of an existing inhaler – potentially fitting inside some inhaler products – which can confidently detect or quantify the various functions of the inhaler together with the time at which they occurred.
The feasibility study we have undertaken demonstrated flowrate accuracy with two different inhaler types to be on par with that of a thermal mass flowmeter.
Analysis of the energy in the acoustic signal produced by airflow through a metered dose inhaler (MDI) enables very accurate and reproducible prediction of volumetric flowrate – ±2.5%. Analysis of the tonal response of a dry powder inhaler (DPI), which utilises swirl as a means to deagglomerate the formulation, produced a linear relationship between peak frequency and volumetric flowrate. This has excellent inter-device consistency, with an accuracy of ±2%.
Using band-pass filtering it is possible to confidently detect events such as the firing of the MDI canister, even at high airflow rates. The breath actuation mechanism (BAM) of the Novolizer can be triggered by the user even if they forget to include the drug cartridge – this can be detected acoustically over and above the signal produced by the airflow. If the user forgets to reinsert the dispensing slide after cleaning their Novolizer then no swirl is created as air is drawn through the inhaler, resulting in a completely different tonal response. In addition, the passage of formulation through the swirl chamber temporarily affects the tonal response and can be characterised as an anomaly in the flow profile. This enables five salient scenarios to be monitored with confidence: i) flowrate profile, ii) BAM did not fire, iii) the dispensing slide was not present, iv) BAM fired but nothing was delivered and v) BAM fired and medicament was delivered.
We believe this technology could offer significant improvement to the usability of almost all inhaler products – increasing compliance through positive and immediate user feedback; helping doctors to work with patients to manage the use of their medication; and helping drug providers learn how they can improve the efficacy of their product during the clinical trials process. With the trend towards the convergence of diagnostics and drug delivery, the ability to provide ‘intelligence’ in a device could create the opportunity to allow patients to adjust their dosage regime to reflect their current disease status and hence reduce the risk of a costly hospital admission.