To date, few systematic reviews and meta-analyses on proper inhalation technique have been published. The issues related to the frequency of errors rate made by patients while using the inhalation device were raised36. Also the prevalence and types of device errors37,38 and patients’ preferences regarding inhaler features (including size, medication administration, durability, a dose counter, portability, perceived ease of use and dose preparation) were assessed. Systematic reviews assessed the clinical effectiveness and cost-effectiveness of inhalers are also available39. Furthermore, an attempt was made to assess clinical outcomes and exacerbation rates after provided educational program in older adults40. Meta-analysis data on the impact of pharmacist-delivered education on asthma clinical outcomes, quality of life, and medication adherence were presented41,42.

After review of the literature, we can conclude that issues regarding patient education in systematic reviews and meta-analyses could be continued in further studies because they have not been fully explored. Our meta-analysis brings a new perspective by approaching the issue in the context of the influence of the type of educational approach on the effect of education. Our study included a different methodology by comparing the effect before education to the effect after education regarding the occurrence of any incorrect use events and critical errors, which was not considered in the previously mentioned meta-analyses. This concept makes this study novel but, at the same time, complementary to already published meta-analyses.

Among factors affecting compliance with inhalation therapy, one of the most important is educating patients on the correct inhalation technique43. Inappropriate inhalation observed in patients is a well-known problem but has remained unsolved for many years16,43. A factor affecting the ability to use an inhaler properly may be that patients use different inhalers simultaneously, which differ in the required inhalation technique. Additionally, approximately 30% of these patients have never been educated in this area43. Many different types of inhalers are available and are supposed to be accessible to the patient. However, as we showed in our meta-analysis, most patients made mistakes when using them before education.

Dabrowska et al.43 showed that while a single training session has been shown to reduce errors in the inhalation technique, its effects are not long-lasting. This means that the effect of a single inhalation training is temporary. It was observed that the effect of inhalation training decreased 6 months after the education. The temporary nature of these effects underscores the need for continuous patient education. It has been demonstrated that the benefits of a single training session diminish over time and should be reinforced.

It is also important to consider the time needed to improve the use of inhalation devices and how long the education lasted. Melani et al.44, considering that repeated education is required to ensure the persistence of good inhaler use, investigated whether the time required to achieve the correct inhaler technique differed between devices. In this study, the authors reported that the mean education time required to correct inhaler misuse was shorter for DPIs than for MDIs. After selecting studies for the systematic review and meta-analysis, we noticed that although Melani et al.44 raised important conclusions almost a decade ago about differences in the time required to achieve the correct inhaler technique between devices, many studies fail to mention this factor. Among the studies in our systematic review, only two8,32 consider the time needed to achieve the correct inhalation technique (Supplementary Table 2).

This indicates another knowledge gap, as new studies lack information on an important factor in assessing the effectiveness of education - time. Although our meta-analysis was not designed to assess the time required to achieve the correct inhaler technique, as this was not included in the research question (PICO), after noticing the lack of information regarding the time required to achieve satisfactory educational outcomes and its duration, we decided to briefly discuss this issue.

Although our research question did not include this aspect, the role of the educator should also be emphasized. There are many reports in the literature about medical personnel educating patients in the field of the inhalation technique45. These can be physicians, nurses, and a pharmacist46. Educating medical personnel is also emphasized so they can provide it correctly to the patient. Studies have shown that medical personnel often do not have the appropriate knowledge in this aspect and require training47,48,49. Our systematic review and meta-analysis showed that physicians, pharmacists, trained lung function technicians, and trained research educators. The group of education providers in the studies we analyzed is complex. However, in most cases, they have a common denominator: the prior acquisition of appropriate qualifications to impart knowledge on the correct inhaler technique. Therefore, it can be assumed that the person who provided education did not significantly influence its effect if they had prior training by the applicable standards.

An additional important aspect is the method used to assess the inhaler technique. Our systematic review showed that patients’ skills can be assessed in different ways and configurations depending on the study design. However, as we have shown in our systematic review (Supplementary Tables 1 and 2), the authors used standardized, well-known “checklists” in many of the studies we reviewed. Obviously, “checklists” may differ slightly depending on the device, even within one type of inhaler. However, the concept of operation of devices belonging to one type is the same. Therefore, any differences in checklists do not constitute a bias in comparing the effects of the type of education we conducted in the meta-analysis. When discussing issues related to the assessment of inhaler technique, it is also important to consider the different types of errors and their definitions, and the fact that they may differ between devices. This is particularly crucial for critical errors50. In our meta-analysis (Fig. 3), we combined data from one study for two different inhalers in a single forest plot of critical errors. The study authors defined critical errors, which we have included in the Supplementary Materials in Table 1. If a meta-analysis were to compare different studies using different devices and definitions of critical errors, the risk of bias would be very high. However, we combined the results for critical errors with the exact definition, which significantly reduces this risk.

It should also be emphasized that there are cases where an inhaler device error is not solely related to a lack of knowledge of the proper technique. This can be explained by the example of DPI and pMDI devices included in our meta-analysis. DPI require a forceful and deep inhalation. This approach allows for the dispersion of coarse particles attached to a lactose carrier51. An error in this area can be made by a person who does not know that they are supposed to inhale strongly and deeply and by someone who knows that they are supposed to do so but may not be able to exert a sufficient inhalation effort. This may be related to patients having varying degrees of airflow limitation, meaning they may have lower inspiratory flows compared to healthy individuals. This, in turn, may affect the distribution of active compounds in the lungs51,52. In the case of pMDI inhalers, one of the difficulties associated with effective drug delivery to the lungs and, consequently, with lower therapeutic effects is coordinating the activation of the device with inhalation. This is particularly difficult for small children and the elderly52. No education may solve the problem in such cases, and the prescriber should change the device. This case indicates that each patient should be treated individually when a physician selects an inhaler. The effectiveness of inhalation therapy depends on the correct inhalation technique and the device chosen by the physician51.

The studies in this meta-analysis are diverse because they include both RCTs and prospective, observational, open-label and real-life. However, this approach provides a holistic view of the available results because although RCTs are considered the most reliable, real-life studies’ role is significant in respiratory diseases53,54,55. RCTs cover a homogeneous, strictly selected, and monitored patient population. Therefore, it is difficult to relate the results obtained in RCTs to situations in real medical practice settings. However, real-life studies involving a heterogeneous group of patients who often do not follow medical recommendations and are accompanied by other diseases better reflect the nature of everyday practice55.

The results of our systematic review and meta-analysis, indicate that regardless of the type of device, patients make mistakes when using inhalers. Additionally, regardless of the inhaler, the occurrence of errors made by patients decreases when they receive education, which we were also able to demonstrate. It should be emphasized that in our meta-analysis we managed to demonstrate an important relationship. For pMDI/MDI devices, it was observed that the type of education impacts the number of errors made in the inhalation technique. This conclusion is based on the fact that in our meta-analysis for pMDI, each subgroup is a different type of education; if the subgroup effect is statistically significant, it indicates that, in this case, the type of education influences the result56. We compared two subgroups. The first subgroup included two studies on education using the face-to-face method17,21 in which training was conducted once as a demonstration. In the second subgroup, we included two studies31,32 in which education in the form of a physical demonstration was also used. The training was repeated until the correct technique was achieved. Our meta-analysis showed that better results were achieved in the second subgroup.

Similar conclusions were drawn by Sestini et al.22 who also observed that the type of education is important in achieving better results in inhalation technique (better results are achieved when education is provided in the form of a demonstration and when the education is repeated). However, for DPI devices, we did not demonstrate such an association.

Additionally, in the analysis for DPI in terms of critical errors, due to the limited number of selected studies for comparison, we did not introduce subgroups (the data concerned one type of device and one educational method, so there was no need to introduce a subgroup).

Although more research in this area is needed to be able to apply conclusions to practice, the result we obtained may constitute a premise for conducting further research on this issue.

It should also be added that in this meta-analysis we were only able to perform analyses for two types of inhalers because among the searched studies we did not find enough data that would meet the inclusion criteria and could be used for comparisons in the meta-analysis. The reason for limiting the number of data points for comparison in the meta-analysis was our assumptions to limit the risk of bias and systematic errors. These included not mixing groups in terms of age, educational approach type, and type of the device, and randomized and nonrandomized studies.

The studies compared in a systematic review included different types of inhalers and education approaches (Table 3). However, each type of training contributed to improving patients’ inhalation skills. Kim et al.6 observed that even a five-minute educational session could decrease the number of incorrectly performed inhalations. However, several included studies showed that some methods were more effective than others7,8,10. Important outcomes were reported by Brusselle et al.57 in a study described an educational method involving patient training through the MyPuff app, which improved inhalation technique and adherence when switching inhalation therapy. Ahn et al.58 reported that the face to face method was effective in improving inhaler technique and adherence but did not improve patient quality of life. There are important findings regarding the importance of patient education and shed light on an issue that could be explored more widely. Additionally, Chrystyn et al.34 compared the proportion of patients making serious errors when using three different DPI inhalers and identified the device that was the most accessible to learn. Therefore, the analysis of the collected literature allows us to conclude that based on the comparison of the number of mistakes made by patients while using the inhalation device, conclusions can be drawn as to which device is associated with a greater risk of making errors and is, therefore, less accessible and more difficult for the user to use and master the inhalation technique. Although the authors of the above studies compared inhalers and tried to select the most accessible ones for patients, the results of these studies still need to be consistent. The synthesis of these results in a systematic review and meta-analysis did not allow for a clear definition of which device is most intelligible to patients before and after education in terms of the critical and any incorrect use events errors they make. Nevertheless, the studies included in the meta-analysis provided the necessary information for analysis regarding patients’ results in the field of inhalation technique before and after education. Although we encountered difficulties in selecting this data, as studies mentioned above on inhalation devices and their operation are diverse, the main goal is often not only to assess the device or patients’ skills but also to assess the effectiveness of treatment, factors influencing compliance with therapeutic recommendations or comparison different educational approaches. Therefore, for this meta-analysis, we had to select from these data those relating to the effect of education and the number of errors made by patients during inhalation. The results from the included studies also allowed for an analysis divided into subgroups according to the type of educational approach. Our meta-analysis did not show that the type of inhaler affected the number of errors before and after education. Although these conclusions should be viewed with caution due to the risk of bias, they may have practical applications and provide a basis for further analysis if more and more consistent research emerges, as they show that practitioners should pay particular attention to education and adaptation it to the patient’s needs rather than changing inhalation devices.

The results obtained in this meta-analysis should be interpreted with caution due to limitations probably related to potential confounding factors in some of the studies, such as lack of age standardization (broad age groups), unequal sample size and significant heterogeneity within some subgroups. Attention should also be paid to the risk of bias, which may be caused by the nature of the included studies, which were prospective, real-life, observational, open-label and, in some cases, non-randomized. A limitation of this meta-analysis may be that we could not perform a meta-analysis for a single type of error (included in the device checklists, Supplementary materials Table 2). It was technically not possible because there would be no studies that could be compared with each other. The studies in the comparison must be matched by device type and type of education; otherwise, there would be a risk of confounding. In some cases, authors reported errors collectively, including as critical, overall, or any errors.