Medication adherence, referring to the level of participation in terms of individuals taking medications as prescribed, is known to be a central health problem, especially important in the treatment of chronic diseases. After half a century of adherence-related research and increased knowledge of the factors involved in its implementation (>200), adherence rates remain fairly stable (Vrijens et al., 2012; Conn and Ruppar, 2017; Ellis et al., 2023). Thus, although the rates observed in clinical trials are considered to be very high (70%–90%), they vary between 10% and 40% in clinical practice (WHO, 2015; Bhattarai et al., 2020). Adherence to medication is essential for individuals to receive the potential therapeutic benefits of the prescription, especially in those conditions where the application of the treatment is much more complex than taking a pill. Lack of adherence is associated with considerable morbidity/mortality (Ellis et al., 2023).

Chronic obstructive pulmonary disease (COPD) is among the significant health challenges worldwide (Duarte-de-Araújo et al., 2019; Lindh et al., 2019) due to its high prevalence (11.7%) (Padmanabhan et al., 2019), the high healthcare costs it leads to (Barja-Martínez et al., 2019; Padmanabhan et al., 2019; Rincon-Montaña and Rosselli, 2019), and the negative effects it has on the quality of life (Rincon-Montaña and Rosselli, 2019). The treatment relies primarily on inhaled medication (Barja-Martínez et al., 2019; Duarte-de-Araújo et al., 2019; Padmanabhan et al., 2019) through currently available devices, which include dry powder inhalers (DPIs), metered-dose inhalers (MDIs), pressurized metered-dose inhalers (pMDIs), and soft mist inhalers (SMIs) (Rincon-Montaña and Rosselli, 2019; Dekhuijzen et al., 2022; Lindh et al., 2022). These devices require many steps, which may be complex, making them difficult to use (Melzer et al., 2017; Takaku et al., 2017; Dekhuijzen et al., 2022). Therefore, the incorrect use of these devices becomes a major problem, leading to reduced therapeutic effects, increased symptoms, and ineffective disease control (Vila Jato, 2020; Dekhuijzen et al., 2022). Increased hospitalization, emergency room visits, and the need for antibiotics and corticosteroids have also been reported, increasing the cost of the disease and leading to adverse effects and a reduction in therapeutic alternatives (Vila Jato, 2020; Dekhuijzen et al., 2022).

To acquire proficiency in handling inhalers, it is essential to provide proper training to patients (Poureslami et al., 2016; Dhadge et al., 2020; Luley et al., 2020; Rodrigues et al., 2021; Lindh et al., 2022; Sulku et al., 2022), since education on the proper use of inhalers is received by only a small number of them (Poureslami et al., 2016; Dekhuijzen et al., 2022).

Furthermore, COPD clinical practice guidelines pay particular attention to proper advice and instruction on inhaler management as a vital part of treatment. They state that the first time a device is prescribed, the IT should be explained and a demonstration should be performed for the patient, training the patient as many times as necessary to achieve a proper IT and confirming that the patient can use it properly. Subsequently, the patient should demonstrate, with their own device, how they perform the IT at each visit to ensure successful execution (Andaluz de Salud, 2019; Global Iniciative for COPD, 2022; Miravitlles et al., 2022). The accessibility of patients to healthcare providers is important for a correct IT because professionals will have more opportunities to assess the patient periodically and train them appropriately (Yawn et al., 2012).

Healthcare professionals (e.g., general practitioners, respiratory physiotherapists, community pharmacists, or health educators) also need to be properly trained, as evidence suggests that their knowledge of the use of inhaled medicines can be improved (Al-Otaibi, 2020; Cvetkovski et al., 2020). IT also improves for them after training, either by attending educational workshops (Al-Otaibi, 2020) or conferences (Takemura et al., 2011), providing explanatory leaflets (Cvetkovski et al., 2020; Matsuyama et al., 2022), or demonstrations with placebo devices (Basheti et al., 2008) or through videos (Cvetkovski et al., 2020; Matsuyama et al., 2022).

This highlights the importance of conducting studies in which the educational intervention is carried out beforehand with public and community health personnel so that they can properly counsel their patients. To the best of our knowledge, no trial of educational intervention concerning the IT has been carried out among general practitioners (GPs) to assess its effectiveness on COPD patient IT performance. Therefore, this study aimed to implement a cluster randomized trial among healthcare professionals at primary care centers (PCCs) to evaluate the effectiveness of an educational intervention on the improvement in the performance of the IT in patients with COPD and prescribed inhaled therapy after the implementation of this educational intervention with their GPs.

The PROF-EPOC study shows that an educational intervention using the teach-back method with GPs has a significant and positive effect on GPs’ performance of the IT and that of their patients after 1 year of follow-up. This improvement was associated not with the characteristics of the GP but with the intervention. This study found that good performance of the IT was related to demonstrating the proper technique with the device, having a good pulmonary function, being among the youngest (≤65) and the oldest (>83) patients, experiencing lower limitation of activity due to dyspnea, and undergoing an intervention lasting more than 25 min. This educational intervention involving GPs could be a promising approach to improving medication adherence and health outcomes in COPD patients.

There are few studies addressing interventions focused on the training of healthcare professionals on the IT, and fewer focused on GPs or COPD patients. Toumas et al. (2009) conducted a study with second-year pharmacy students who were given a brochure and found that 10% of the participants performed the technique properly as a result. However, when they were given a demonstration with the device, this percentage increased to 62%. Al-Otaibi (2020) performed the intervention on physicians, pharmacists, respiratory therapists, and health educators who attended a training course where an improvement in the inhaler handling questionnaire score of almost 40% was observed. Cvetkovski et al. (2020) carried out their study on primary care physicians, showing that only 0.88% of the professionals performed the IT incorrectly after reading a leaflet and witnessing an explanation with a device. The present study showed a similar increase for the proper IT for GPs.

Regarding the improvement of the IT in patients after the training of their GPs, there are few studies in the literature carried out on COPD patients, and most are conducted jointly with asthma patients. Aksu et al. (2016) conducted a prospective study of 108 patients with asthma and COPD. The physician made an initial visit where the patient’s IT was corrected, and after 3 months, the IT was checked again. The percentage of patients with good IT improved (28%), showing how the practical training provided by physicians on the management of inhalers was an effective tool in the improvement of ITs. Takaku et al. (2017) carried out a prospective observational study with 216 subjects with asthma (the majority) and COPD. The counseling was performed by a pharmacist who had received prior training. They reported an improvement of 53% in the IT after the intervention. Takemura et al. (2013) performed a study training 81 community pharmacists to educate patients through a brochure. A review was conducted 4 years later, and it was observed that 39 patients had improved adherence and quality of life, including the IT. These studies show that training HCP improves the IT in their patients, in line with the results of our own study. However, these studies did not include effectiveness parameters. Only the study of Kim et al. (2021) reported an NNT of 3.3, which is similar to our result. Further studies are, thus, necessary to address this topic.

There is apparent agreement on the need to demonstrate the practical management of inhalers by professionals before prescribing them. The IT should be performed appropriately during every appointment at the healthcare center and should be controlled by healthcare professionals (Aksu et al., 2016; Lavorini et al., 2019; Melani, 2021; Global Iniciative for COPD, 2022). When a change in treatment takes place, a new demonstration must be repeated by both the healthcare professional and the patient (Dekhuijzen et al., 2022). Similar results were obtained in the present study by questioning GPs. The IT must also be reviewed periodically in order to be effective (Kim et al., 2021; Dekhuijzen et al., 2022; Global Iniciative for COPD, 2022), as a relationship between regular instruction and adherence has been observed (Martínez Ibán et al., 2019; Ahn et al., 2020; Efil et al., 2020), with an improvement in the quality of life (Martínez Ibán et al., 2019; Efil et al., 2020; Luley et al., 2020; Lindh et al., 2022) and a reduction in the need for hospital admission of up to 80% (Martínez Ibán et al., 2019; Efil et al., 2020). Thus, the professionals considered that the IT should be checked periodically, although they did not agree on how often it should be checked. However, previous studies carried out in the same environment showed that reminders about the IT for COPD patients should take place every 3 months (Barnestein-Fonseca et al., 2023). Other studies suggest the same frequency of 3 months improves IT and adherence (Takaku et al., 2017; Ahn et al., 2020), while another recommends a lesser frequency (Lee et al., 2016; Yoo et al., 2017).

It is clear that suitable instruction can improve IT (Klijn et al., 2017; Barnestein-Fonseca et al., 2023). However, due to varying educational levels, different teaching techniques are used. Essentially, these teaching techniques can be classified into two types: brochures and practical demonstrations. The studies of educational IT interventions (Toumas et al., 2009; Bosnic-Anticevich et al., 2010; Klijn et al., 2017; Jia et al., 2020; Melani, 2021; Barnestein-Fonseca et al., 2023) showed that interventions including a face-to-face or video demonstration showing how to use inhalers are effective. In the same way, after testing which educational interventions were the most appropriate for COPD patients in our environment, it was decided to include an educational intervention based on a practical demonstration of the IT (Barnestein-Fonseca et al., 2011; Barnestein-Fonseca et al., 2023).

Our work shows fewer IT improvements than most studies carried out, although there are some exceptions (Giner et al., 2002; Cabedo García et al., 2010; O’Dwyer et al., 2020). This may be because the analysis was performed considering the intention-to-treat principle, while the other authors did not take into account the dropouts.

Although many patients indicated that they had received IT instruction, the rate of incorrect techniques was high. This fact could be due, in part, to the limited knowledge of the professionals who prescribe these medicines on how to manage inhalers and the teaching techniques (Aksu et al., 2016; Plaza et al., 2018; Al-Otaibi, 2020; Cvetkovski et al., 2020), as well as to a lack of regular IT verification with reminders and to the kind of training chosen (Klijn et al., 2017; Takaku et al., 2017; Kaplan and Price, 2018; Lavorini et al., 2019; Melani, 2021; Lindh et al., 2022). These results agree with the findings of this work, where the GPs manifested a high level of incorrect IT in their patients and where the reminders of the IT were performed with inappropriate periodicity.

In addition, it is essential to consider that reminders are important not only for patients but also for professionals so that the training they provide to their patients will also be correct. Some authors claim that GPs may be served by less frequent updating of skills in the management of particular inhalers compared to others (Takemura et al., 2011; Bosnic-Anticevich et al., 2018; Cvetkovski et al., 2020). Although regular educational interventions do indeed improve the long-lasting consistency of the IT (Takemura et al., 2011), from the perspective of GPs, illness management should be prioritized (Cvetkovski et al., 2020). It is clearly demonstrated that motivation plays an essential role in the IT, as it is not just a physical skill (Bosnic-Anticevich et al., 2018). Whether GPs have the time and disposition to educate COPD patients about the IT and implement strategies to improve adherence and proper use of medicines remains unanswered (Cvetkovski et al., 2020).

Several works indicated that from 50% to 94% of patients are not able to carry out the inhalation technique correctly (Chrystyn et al., 2017; Adib-Hajbaghery and Karimi, 2018; Duarte-de-Araújo et al., 2019; Rincon-Montaña and Rosselli, 2019; Dhadge et al., 2020; Vila Jato, 2020; Dekhuijzen et al., 2022; Sulku et al., 2022), even though the success of the treatment depends on it (Chrystyn et al., 2017; Adib-Hajbaghery and Karimi, 2018; Duarte-de-Araújo et al., 2019; Lindh et al., 2019; Padmanabhan et al., 2019; Rincon-Montaña and Rosselli, 2019; Rodriguez-Garcia et al., 2020; Schreiber et al., 2020; Dekhuijzen et al., 2022). The errors found in all the devices are similar to those reported by Melani (2021) in a review. Previous works revealed that the errors depended on the subject’s preparedness and physical ability to execute the technique. The most common errors found were to achieve lower peak inhalation flow, lower MMSE scores, fewer appointments with the pulmonologist, and not receiving previous educational management of inhalers (Leiva-Fernandez et al., 2013; Barnestein-Fonseca et al., 2022). Errors associated with inhalers are less frequent and are linked to different positions (in the case of Turbuhaler^®) and flows (coordination in the case of pMDI) (Chrystyn et al., 2017; Duarte-de-Araújo et al., 2019; Lindh et al., 2019). Despite improvements and breakthroughs in technology, most subjects do not intuitively reach full competence with the inhaler by themselves (Harb et al., 2020; Melani, 2021). Studies using real-world data inform us that, as of yet, there is no easy-to-use inhaler available.

A poor IT leads to a reduction of its beneficial effect, lower symptom control, and therefore, poor COPD control (Padmanabhan et al., 2019; Vila Jato, 2020; Dekhuijzen et al., 2022). It may also be associated with an increase in the number of emergency room visits, hospitalizations, or the use of antibiotic and corticosteroid treatments, ultimately increasing the cost of COPD management, increasing adverse reactions, and limiting therapeutic alternatives (Martínez Ibán et al., 2019; Efil et al., 2020; Vila Jato, 2020; Dekhuijzen et al., 2022). The performance of the correct IT has been related, in this study as well, to a better FEV1, perhaps because correct performance allows for better FEV1, potentially slowing down functional deterioration, and it then improves the technique because there are steps that are related to good pulmonary function, such as deep inhalation of the aerosol (Melani et al., 2011; Padmanabhan et al., 2019; Efil et al., 2020; Vila Jato, 2020). Among those with poorer lung function, the percentage of those performing the correct IT was influenced by age; specifically, those under 65 and over 83 years of age demonstrated a higher percentage of correct technique. These findings could be associated with a greater concern for the progression of COPD in younger and older people with shorter and longer diagnosis times, respectively. It has been found that the performance of the correct IT is related to QoL measured by SGRQ in both groups. In the CG, the modification is observed at the global scale, and there is a higher percentage of subjects with the correct technique among those who have a poorer quality of life. This could be explained by the fact that, feeling worse, they make a greater effort to take advantage of the benefits that the treatments can provide for them. In the IG, the differences are observed on the activity scale. The subjects with higher scores (bad quality of life) perform the technique less well than those with lower scores. Poor performance of the technique makes it difficult to perform daily activities (Melani et al., 2011; Padmanabhan et al., 2019).

Finally, when the visit lasts longer than 25 min, there is a higher percentage of patients who perform well on the IT (Weheida et al., 2017; Efil et al., 2020; Lindh et al., 2022). This finding correlates with the methods used for training the patients. The intervention includes the feedback of the patients until they develop a correct IT, so to obtain a higher percentage of good results, it is necessary to spend time on correct training. However, when the training is fixed, the time of intervention decreases during the follow-up visits (Kim et al., 2021; Barnestein-Fonseca et al., 2023).

Overall IT performance for GPs showed the same errors as the patients, those related to their preparation before performing the technique. However, when analyzed by devices, the most frequent errors among GPs are related to the device itself, even if the type of error is the same. This is perhaps because they do not have lung capacity problems, as their patients do. The consistency in the type of error over different devices is understandable, given that they have the same characteristics (Dekhuijzen et al., 2022). However, are the errors subject related rather than device related? Could there be a transfer of knowledge between inhalers (Dekhuijzen et al., 2022)? This was partially noted in this study, with GP errors related to their preparation for the technique. Thus, focusing education on the most common known errors could help improve full IT competence, regardless of the inhaler used.

The main strength of this study is the use of an intervention that is quick, easy, and reproducible to improve the IT, based on the practical demonstration of the IT using the teach-back method, previously tested in clinical trials (Barnestein-Fonseca et al., 2011; Barnestein-Fonseca et al., 2023). With these methods, patients can demonstrate their inhaler handling and subsequently receive specific feedback from the instructor. In addition, the dropout percentage was found to be lower than expected, and there were no differences between the initial and final samples. Therefore, the internal validity of the study is guaranteed.

This work also has limitations. First, the missing data lead to a loss of estimation accuracy. To address this, the sample size was increased by 40% (i.e., the expected losses), telephone calls were made to unreachable patients at different times, and extra appointments for clinic visits were scheduled; these resulted in lower losses than expected. Moreover, we applied data imputation to complete the lost data. Second, randomization was applied at the second level before the recruitment of participants from the first level, where the impact of the intervention was measured, which could lead to selection bias at this level. To minimize this bias, external research assumed the patients’ selection and their follow-up; this person did not know the GP randomization. In addition, different motivations among randomized professionals could lead to different recruitment rates, as control GPs may be less willing to cooperate. To counteract this lack of motivation, control professionals received the same training as intervention professionals at the end of the trial (Basheti et al., 2008; Ahn et al., 2020). Another potential bias could have come from the selective correction of only critical errors in the control group patients, which could have worked in favor of the study hypothesis by increasing the rate of the incorrect technique in this group, considering that all the steps indicated in the template had to be fulfilled in the assessment of the technique. Another limitation could be interviewer bias in the measurement of variables based on the application of questionnaires due to the involvement of different interviewers in administering them. To minimize these biases, the interviewer monitors were previously trained to ensure that the visits were as homogeneous as possible. To avoid this bias among the health professionals in the intervention group, who were, therefore, in charge of training their patients in the correct inhalation technique, they were thoroughly trained and provided with a common data collection booklet and an explanatory manual on how to collect each of the variables that were measured in the follow-up visits of their patients.

The results of this research could have a major impact on the prognosis of the disease, making it a promising approach. This is an easy-to-implement intervention with high potential for real-life efficacy in improving medication adherence and health outcomes in COPD patients. As a recommendation for implementation in the clinical setting, this training could be extended to all professionals involved in the care of COPD patients; it would represent a more effective strategy that could benefit a larger number of individuals. It is also important to consider changing the inhaler used or applying a spacer, especially for those who have greater difficulties handling the different devices due to their age and physical and/or mental disability.

As a group of patients still struggled to manage their inhalers, a more detailed analysis of patient characteristics would be necessary to modify certain phases of the training (e.g., frequency of reminders for both professionals and patients). In conclusion, this study shows the efficacy of direct training using the teach-back method in the inhaler technique in patients by a trained professional (general practitioner) with sufficient time (e.g., specific consultation for medication review).