# An Audio-Based Method for Assessing Proper Usage of Dry Powder Inhalers
###### Abstract  
Critical technique errors are very often performed by patients in the use of Dry Powder Inhalers (DPIs) resulting in a reduction of the clinical efficiency of such medication. Those critical errors include: pure inhalation, non-arming of the device, no exhalation before or after inhalation, and non-holding of breath for 5-10 s between inhalation and exhalation. In this work, an audio-based classification method that assesses patient DPI user technique is presented by extracting the the non-silent audio segments and categorizing them into respiratory sounds. Twenty healthy and non-healthy volunteers used the same placebo inhaler (Bretaris Genuair Inhaler) in order to evaluate the performance of the algorithm. The audio-based method achieved an F1-score of 89.87% in classifying sound events (_Actuation, Inhale, Button Press_, and _Exhale_). The significance of the algorithm lies not just on automatic classification but on a post-processing step of peak detection that resulted in an improvement of 5.58% on the F1-score, reaching 94.85%. This method can provide a clinically accurate assessment of the patient's inhaler use without the supervision of a doctor. audio classification; machine learning; feature extraction; MFCCs; asthma; COPD; DPIs 1  
on visual/aural assessment, where a healthcare professional supervises the whole process [11; 12]. However, this method of assessment is based on the healthcare professional's perception, it gives an equal rating to all errors, it could overestimate patient performance and it cannot be used to monitor how patients use their inhaler outside of clinical visits, without the supervision of a doctor [13; 14]. It is reported that the inhaler user technique from patients can be improved by inhaler training devices [15]. Guiding patients to improve their inhaler usage technique while providing proper feedback to medical personnel could avoid dangerous exacerbation events while facilitating effective self-management of obstructive respiratory diseases [16; 17]. This is the first step in guiding the patients by evaluating the followed procedure from the audio information given through either a smartphone's microphone or through an attachable microphone that is connected to the inhaler. A DPI is a device that disperses a dry powder medication to the lungs. The medication is released only when the patient takes a deep, strong breath in through the inhaler; therefore, it is breath-activated. The difference between Dry Powder Inhalers (DPIs) and Metered Dose Inhalers (MDIs) is that MDIs push medication into the lungs. Dry powder inhalers are the third type of inhaler device, after MDIs and nebulizers, and among these seems to be the most promising devices for future use [18]. Such devices carry the dose into the lungs (actuation) when breathing is performed by the patient and this way there is no need for coordination of patient's breathing and the activation of the device. Furthermore, DPIs have other important attributes that make them preferable among other devices [19]. Promising physical stability associated with DPIs is due to the solid form of the formulation. Proper inhaler use includes the following steps (details can be found in [20]) (shown, also, in Figure 1): remove the cap; hold inhaler horizontally with the colored button facing up; press and release the button; breathe out fully (away from inhaler); breathe in strongly and deeply with mouthpiece in mouth and the lips sealed; hold breath for 5 to 10 s; breathe out gently (away from inhaler); and replace cap. Despite these attributes, as it has been aforementioned, patients often make critical errors, such as pure inhalation, non-arming of the device, no exhalation before or after inhalation and non-holding of the breath for more than 5 s. Those errors prohibit them from receiving full therapeutic effect from their medication. For the scope of this study, the Bretaris Genuair placebo Inhaler [20] was used for the data capture procedure.