Advantages and challenges of training of inhalation technique with the Vitalograph AIM device

Abstract

Proper inhalation technique is crucial for the effectiveness of inhalation treatment in obstructive lung diseases. However, many patients do not use their inhaler properly. There is a lack of clear guidance on how to effectively train inhalation technique. One of the tools that can be helpful in assessing the inhalation technique and at the same time allows to train correct inhalation technique is the Vitalograph AIM. The aim of the study was to assess the effectiveness of inhalation technique training using Vitalograph AIM in patients with asthma or COPD. This was a prospective, single-centre, interventional, non-randomized study. Patients with asthma and COPD who were treated with any inhaler on a daily basis were enrolled. Inhalation technique was assessed using Vitalograph AIM and then all patients, who did not use their inhaler correctly were trained using this tool. The improvement in inhalation technique and duration of training were measured. 121 patients were enrolled in the study (82 with asthma and 39 with COPD). Only 42 patients (34.7%) used a single type of inhaler while the remaining patients used ≥ 2 inhalers. Ninety-one patients used MDI, and 79 patients used DPI. At baseline, correct inhalation technique was found in only 6/91 (6.6%) patients using MDI and 34/79 patients (43%) using DPI. Training with Vitalograph AIM resulted in improvement and correct inhalation technique in 57/85 patients using MDI (67.1%) (P < 0.001) and 18/45 (40%) using DPI (P = 0.016). After training among patients treated with MDI, correct inhalation technique was found in 46/91 (50.6%) patients using MDI and 50/79 patients (63.3%) using DPI. Training with Vitalograph AIM may be associated with improvement in inhalation technique, especially in patients using MDI.

Trial registration: This study was registered at ClinicalTrials.gov (NCT04349735) on 16-12-19.

Background

Proper inhalation technique is crucial for the effectiveness of inhalation treatment in obstructive lung diseases, most frequently with asthma and chronic obstructive pulmonary disease (COPD). Despite the emphasis on regular training in inhalation skills in patients, progress in the development of novel inhalers and the increasing availability of medical education, many patients still do not take their inhaled drugs optimally^1,2.

Although many recommendations emphasize the importance of correct inhalation technique of inhaled drugs, there is lack of guidance on how to train the inhalation technique to be optimal. Moreover, many health care providers have problem with instructing patients properly and may lack effective tools for such a training^3–5.

According to experts, the key elements for achieving the correct inhalation technique include adjusting the inhaler to the patient’s abilities and preferences, limiting the number of inhalers used, regularly checking inhalation technique during each visit, personal demonstration of how to use the inhaler correctly (using placebo inhalers) by the physician or nurse and repeated, regular checking whether the patient remembers how to use the inhaler correctly^6–8. However, as experience shows, achieving a good training effect is not easy as patients repeat errors and the effect of training is temporary^9–11. There are no consistent guidelines on how inhalation technique should be assessed. In everyday practice, inhalation technique is assessed by a checklist of errors, a few-point scale assessing the correctness of inhalation technique, expressing the total score as a percentage/ ratio, deducting points from the final score when errors were made, and weighting steps within the checklist depending on how crucial the step was¹². Also, peak inspiratory flow measurement may be used both for inhaler technique assessment and to facilitate the choice of the inhaler^13,14.

One of the tools that can be helpful in assessing inhalation skills and at the same time allows to train the correct inhalation technique is the Vitalograph AIM (Aerosol Inhalation Monitor) which simulates inhalation with metered dose inhaler (MDI), MDI with spacer or dry powder inhaler (DPI). The device evaluates the user’s technique, providing visual feedback with the use of colour signalling – green light when inhalation technique is good, orange light for suboptimal and red for definitely improper inhalation maneuver. Vitalograph AIM is designed to identify errors related to actuation of the inhaler, measure if inspiratory flow rate or inhalation time are adequate and if breath-hold time was sufficient¹⁵. The immediate visual feedback highlights the specific element needing adjustment and may encourage patients to keep practicing to improve their inhalation technique.

The aim of the study was to assess whether inhalation technique training using Vitalograph AIM was associated with improvement in inhalation technique in patients with asthma or COPD.

General study design

This was a prospective, single-centre, interventional, non-randomized study performed between 2021 and 2023. Patients with asthma or COPD, who were treated with any inhaler on a daily basis were included. Patients’ inhalation technique was assessed using Vitalograph AIM and then all patients were trained using this tool. The study was a part of the larger project aimed to assessed different methods of evaluation inhalation technique (NCT04349735), the results of this project are in press.

A written informed consent was obtained from all enrolled patients. The study was approved by the Ethics Committee of the Medical University of Warsaw (KB/43/2019).

Patients

Patients diagnosed with asthma or COPD treated on a daily basis with at least one inhaler were invited to participate in this study. Adult patients admitted to the Department of Internal Medicine, Pulmonary Diseases and Allergy, Medical University of Warsaw, or treated in institutional out-patient respiratory clinic, were enrolled.

Inclusion criteria of the study were as follows: (1) Age 18–85 years; (2) COPD or asthma diagnosed at least 3 months prior to enrolment: (3) regular, daily intake of at least one inhaled medication via: DPI, MDI or soft mist inhaler (SMI). Exclusion criteria comprised: (1) Irregular (by recommendations) or only emergency use of inhaled medications; (2) symptoms of acute respiratory infection (up to day 5 from the onset of infection); (3) acute exacerbation of obstructive disease (up to 5 days from the beginning).

Methods

The assessment of inhalation technique and training in inhalation were performed using Vitalograph AIM. The objectives of the study were:

1. Assessment of inhalation technique with Vitalograph AIM in patients with asthma and COPD.

2. Difference in proportion of patients with proper, suboptimal and improper inhalation technique before and after the Vitalograph AIM based training.

None of the patients used MDI with spacer at enrolment.

According to the assessment by Vitalograph AIM, inhalation technique was defined as:

1. Proper (green light placed at the bottom of the image of the lungs on the device) – when all steps of inhalation were properly performed.

2. Suboptimal (orange light placed at the apex of the image of the lungs on the device) – when inhalation time or breath-hold time were too short, which may have resulted in reduced drug deposition in the lungs.

3. Improper (red light placed in the upper airways or in front of the patient in the image on the device) – when the activation of inhaler was missed or too early, or inhalation speed was too high, which may have led to little or no drug administration or drug deposition mainly in mouth.

Fig. 1.

Generic inhalation technique training and assessment device used in the study.

Source: Adapted by the authors from manufacturer-provided product materials.

Inhalation training was delivered face-to-face by a single instructor using the Vitalograph AIM device. The training focused on correct actuation, appropriate inspiratory flow rate, inhalation time, and breath-hold duration — parameters directly assessed by the Vitalograph AIM system. The session continued until the patient achieved proper inhalation technique or became fatigued and was intended to last no longer than 15 min. The instructor explained the type of error made, demonstrated the correct inhalation technique, and provided real-time feedback. Performance feedback was displayed on the Vitalograph AIM screen and confirmed verbally by the trainer. The duration of the training was recorded in the following intervals: <2 min, 2–3 min, 4–5 min, 6–10 min, and 11–15 min.

The improvement in inhalation technique after training was rated as:

1. Good-when patient’s inhalation technique improved and was assessed as proper.

2. Bad-when none or only partial improvement was attained, but proper inhalation technique was not achieved.

Figure 2 presents the design and operation of the Vitalograph AIM device, including the assessment of key steps in the inhalation technique and the feedback provided by the device, which informs patients about the correctness of their inhalation technique and identifies areas for improvement.

Fig. 2.

Schematic representation of the operation of the inhalation training and assessment device in patients.

Source: Authors’ adaptation of manufacturer-provided materials.

Patients who had proper inhalation technique before and after training were not included to either of the two described groups. As majority of the patients used more than 1 inhaler, results were analysed in relation to the types of inhalers used by the patients.

Statistical analysis

Statistical analysis was performed using MedCalc Statistical Software version 23.1.6 (MedCalc Software Ltd, Ostend, Belgium; https://www.medcalc.org; 2025). Since participants may have used more than one inhaler, a per-inhaler based approach was applied for data analysis. Data were given as median and 95%CI or number of patients. Differences in inhalation technique before and after training were measured with Wilcoxon test. Differences between groups were compared using chi-square test for categorical variables and Kruskal Walis test for continuous variables.

Results

The study included 121 patients with asthma (n = 82, 67.8%) or COPD (n = 39, 32.2%). The median age of the study participants was 63 years (IQR 54–72 years), the majority were women (n = 73, 60.3%), the median duration of obstructive disease was 13 years (IQR 7–20 years).

Only 42 patients (34.7%) used a single type of inhaler while the others (79, 75.3%) used 2 or more inhalers in their treatment. Ninety-one patients used MDI inhalers, and 79 patients used DPI.

In the assessment with Vitalograph AIM, correct inhalation technique at baseline was found in only 6 out of 91 (6.6%) patients using MDI and 34 out of 79 patients (43%) using DPI. These patients did not undergo inhalation technique training.

At the group-level comparison training with Vitalograph AIM resulted in improved inhalation technique in patients using MDI (P < 0.001) and DPI (P = 0.016). However, not all individuals improved. Following the training with Vitalograph AIM any improvement in inhalation technique was noted in 57/85 patients using MDI (67.1%) and in 18/45 patients using DPI (40%), while the fully proper inhalation technique was achieved only in 40/85 (47.1%) patients using MDI and 15/45 (33.3%) using DPI.

Finally, in the entire group the fully correct inhalation technique was seen in 46/91 (50.6%) patients using MDI (Fig. 3) and 50/79 patients (63.3%) using DPI (Fig. 4).

Fig. 3.

Inhalation technique assessed by Vitalograph AIM in patients using MDI before and after training.

Fig. 4.

Inhalation technique assessed by Vitalograph AIM in patients using DPI before and after training.

In the group of patients treated with MDI, those who failed to achieve improvement despite training based on Vitalograph AIM were older (69.5 vs. 62 or 63 years, P = 0.043) and initially made more errors during inhalation (P = 0.019) (Table 1).

Table 1.

Comparison of patients treated with MDI according to improvement in inhalation technique after training.

MDI	Patients with improved inhalation technique N = 57	Patients who failed to improve inhalation technique N = 28	Patient with correct inhalation technique before and after training N = 6	P value
Gender F/M	35/22	16/12	4/2	0.884
Asthma/ COPD	44/13	16/12	3/3	0.097
Education (primary/secondary/higher)	3/32/22	3/17/8	0/4/2	0.743
Age (years)	62 (57.6–66)	69.5 (62.4–71.6)	63 (52.4–77)	0.043
Duration of asthma or COPD (years)	15 (10-18.7)	11 (5.4–15)	12 (10-20.6)	0.431
COPD Assessment Test (points)	22 (19.1–26)	21.5 (14.9–28.7)	25 (18-28)	0.94
Asthma Control Test (points)	20 (18–21)	16 (12.6–23.4)	18 (15-19)	0.26
FEV1 (L)	1.88 (1.43–2.1)	1.6 (0.92–2.15)	1.01 (0.75-1.95)	0.454
FEV1 (%N)	74.5% (57.5–80)	56% (41.3–82.3)	44% (27-81)	0.380
Number of inhalers	2.0 (1.76 -2.0)	2.0 (2.0-2.05)	2.0 (2.0-3.0)	0.419
Sum of inhalation errors before training	3.0 (2.0-3.4)	4.0 (3.0–4.0)	1.0 (0-1.0)	0.019

Data are given as median and 95%CI or number of patients.

F female, M male, FEV₁ forced expiratory volume in 1st second, FEV₁ %N forced expiratory volume in 1st second expressed as percentage of predicted value

Among patients using DPI, patients who did not improve despite training had significantly worse parameters of respiratory function (Table 2). A tendency to older age was also observed in this group of patients, the difference in age did not reach statistical significance (P = 0.086).

Table 2.

Comparison of patients treated with DPI according to improvement in inhalation technique after training.

DPI	Patients with improved inhalation technique N = 18	Patients who failed to improve inhalation technique N = 27	Patient with correct inhalation technique before and after training N = 34	P value
Gender F/M	14/4	16/11	17/7	0.152
Asthma/ COPD	12/6	12/15	23/11	0.145
Education (primary/secondary/higher)	2/9/7	1/18/8	3/19/12	0.780
Age (years)	62.5 (52-67.4)	68 (63-74.3)	62.5 (55–66)	0.086
Duration of asthma or COPD (years)	10 (6.4–16.2)	10 (5.9–20)	14.5 (11.7–20)	0.325
COPD Assessment Test (points)	17 (2.4–23.2)	22 (16.3–26)	22 (19.6–28.4)	0.118
Asthma Control Test (points)	19 (12.5–23.5)	15.5 (10.2–22.3)	20 (17–23)	0.264
FEV1 (L)	1.95 (1.4–2.4)	1.15 (0.9–1.8)	1.95 (1.4–2.5)	0.021
FEV1 (%N)	78% (65-89.3)	49% (39.1–65.0)	71% (48.4–80.7)	0.044
Number of inhalers	1.5 1-2.4	2 (2.0–3.0)	2 (2.0–2.0)	0.185
Sum of inhalation errors before training	2.5 (1–3)	2.0 (1–3)	1.0 (0–1)	0.018

Data are given as median and 95%CI or number of patients.

F female, M male, FEV₁ forced expiratory volume in 1st second, FEV₁ %N forced expiratory volume in 1st second expressed as percentage of predicted value.

Training of the correct inhalation with the use of Vitalograph AIM took from 1 to 10 min. In most patients (65/121) it lasted 2–3 min.

In multivariable logistic regression, both older age (OR 0.95, 95% CI 0.91–0.99; P = 0.017) and a higher number of baseline MDI inhalation technique errors (OR 0.65, 95% CI 0.46–0.92; P = 0.015) were independently associated with lower odds of achieving correct inhalation technique. The model showed acceptable discrimination (AUC = 0.76, 95%CI 0.651–0.844) and a borderline Hosmer–Lemeshow goodness-of-fit (P = 0.044) (Table 3). For DPI in logistic regression, higher baseline FEV₁ (L) was the only independent predictor of achieving correct DPI inhalation technique after training (OR 3.38, 95% CI 1.11–10.28; P = 0.032). The model demonstrated acceptable calibration (Hosmer–Lemeshow P = 0.174) and moderate discrimination (AUC = 0.73, 95%CI 0.555–0.867) (Table 3).

Table 3.

Multivariable logistic regression analysis for achieving proper inhalation technique as a result of training with the Vitalograph AIM.

		OR (95%CI)	P value	AUC (95%CI)	Hosmer–Lemeshow
MDI	Age (years)	0.95 (0.91–0.99)	0.017	0.76 (0.65–0.84)	P = 0.044
	Sum of baseline inhalation errors	0.65 (0.46–0.92)	0.015	0.76 (0.65–0.84)
DPI	FEV1 (L)	3.38 (1.11–10.28)	0.032	0.73 (0.56–0.87)	P = 0.174

FEV₁ forced expiratory volume in 1st second

Discussion

In this study, we found that inhalation technique was suboptimal in the majority of patients with asthma or COPD, particularly among users of MDI devices, in whom correct technique at baseline was observed in only 6.6% of cases. Training with the Vitalograph AIM device substantially improved inhalation technique in both MDI and DPI users, although full correction was achieved in only half of the patients using MDI and in approximately two-thirds of those using DPI. Importantly, the determinants of successful improvement differed between inhaler types: older age and a higher number of baseline errors reduced the likelihood of achieving correct technique with MDI, whereas for DPI devices higher baseline FEV₁ was the only independent predictor of improvement. These findings emphasize that although structured training with Vitalograph AIM is effective, patient-related factors significantly influence the ability to acquire correct inhalation technique and may require tailored educational strategies. On the other hand, the lack of improvement despite inhalation training can help to identify these patients who may benefit from switching to another type of inhaler or from adding a spacer in case of MDI use.

In our study, a particularly high effectiveness of training with the Vitalograph AIM was observed among patients using MDIs. This is significant, as patients using MDIs are more likely to make errors during inhalation – according to Chrystyn et al., 86.8% of MDI users make at least one mistake when taking their inhaled medication¹, while our earlier observations showed that 62.9% of patients treated with MDIs were using them incorrectly¹⁶. It constitutes a substantial population of patients who may considerably benefit from training with the Vitalograph AIM. The greater improvement due to inhalation training with Vitalograph AIM may result from our middle-aged population and relatively poor baseline inhalation technique. Both of these factors occurred to be positive predictive factors for improving inhalation technique when training with the Vitalograph AIM. We speculate that for MDI users, the training delivered with Vitalograph AIM is essentially uniform, as the critical steps and coordination requirements are similar across all MDI devices. In contrast, DPI inhalers differ substantially in their internal resistance, dose-release mechanisms and inspiratory flow requirements, meaning that optimal training should be tailored to the specific DPI type used by the patient.

However, the main limitation of assessing inhalation technique using the Vitalograph AIM is that the device evaluates only a subset of the steps performed during inhalation (correct actuation, inspiratory flow rate, inhalation time, breath-hold time) — considerably fewer than when assessing inhalation technique with a checklist of errors. For MDIs, it allows evaluation of 3 out of the 5 steps that the ADMIT project identified as essential for this type of inhaler (correct canister activation, inhalation rates and times, breath-hold time), and for DPIs, 2 out of the 5 steps (a single brisk, deep inhalation; holding the breath for 5–10 s or as long as possible)¹⁷. It does not allow for the assessment of correct inhaler preparation or performing an exhalation before inhaling the medication— the absence of which is one of the most common errors made by patients with asthma and COPD¹⁸. A limitation of assessing DPI inhalation technique with the Vitalograph AIM is that the device defines a correct inspiratory flow rate as > 30 L/min¹⁵. Numerous DPI inhalers are available on the market, each with a different internal resistance (high-, medium-, or low-resistance), and therefore requiring different peak inspiratory flow (PIF) values to achieve adequate powder deaggregation¹⁹. Many devices need a peak inspiratory flow rate (PIFR) > 60 L/min for optimal dispersion, while others achieve sufficient deaggregation at > 30 L/min²⁰. In general, a PIF < 60 L/min is considered suboptimal for most DPI²¹. The resistance of the Vitalograph AIM‑simulated DPI is classified as moderate²². For patients using devices that require higher PIF values, this may lead to an overestimation of inspiratory effort—judged as adequate by Vitalograph AIM despite being insufficient for their actual inhaler. Therefore, the findings should not be generalized to all types of DPIs, particularly those with different internal resistance characteristics.

Suboptimal PIF for low‑ to medium‑high‑resistance DPIs has been reported in 19% to 84% of stable COPD outpatients²³. Older age, lower educational level, use of DPIs, and lower predicted FEV₁% are associated with insufficient PIF²⁴. A reliable assessment of PIF can be performed using the In‑Check Dial^13,21.Despite the above-mentioned limitations the elements assessed by the Vitalograph AIM are crucial for correct inhalation, what helps to identify and eliminate some frequently occurring critical errors: for MDIs, a forceful inspiratory effort (instead of a slow and deep inhalation), and for both inhaler types, an insufficient breath-hold at the end of inhalation²⁵. It is emphasized that errors related to inhaler preparation and handling are easier to observe, whereas errors related to the inhalation maneuver itself are difficult to assess without the assistance of a quantification tool²⁶.

In this study, patients who did not improve despite training differed by inhaler type. Among MDI users, non-responders were older and made more baseline errors, suggesting that both age-related factors and the initial severity of technique deficits may hinder effective learning. In contrast, DPI non-responders had significantly poorer lung function, indicating that insufficient inspiratory capacity may limit their ability to perform the technique correctly even after instruction. These findings highlight that barriers to improvement are device-specific and may require tailored training approaches.

There are only a few previous studies that have evaluated the utility of the Vitalograph AIM in assessing and training inhalation technique. In the study by Lin et al., which evaluated the agreement between a checklist-based assessment and the Vitalograph AIM, the authors found that the checklist tended to overestimate the accuracy of critical steps, including actuation and inhalation time in MDIs, and inspiratory flow in DPIs¹⁵. This was confirmed by Shealy et al., who documented that only 13% of patients who made no errors according to the checklist were confirmed to have correct inhalation technique when evaluated with the Vitalograph AIM. Notably, in that study, correct MDI technique as assessed by the Vitalograph AIM was observed in only 6% of participants, which is consistent with the findings of our study²⁷. However, most checklists used to assess inhalation technique have not undergone validation.

The use of the Vitalograph AIM to assess inhalation technique is not widespread in clinical practice, resulting in limited evidence on the effectiveness of this training method. Although the device has been available for many years and is FDA-approved for evaluating inhalation technique, it has never been included in Global Initiative for Asthma or Global Initiative for Chronic Obstructive Lung Disease recommendations^6,7. In the study by Alotabi et al., similar to our findings, correct inhalation technique was observed in 58% of DPI users and only 18% of MDI users²⁸. Hardwell et al. reported that among 1,291 asthma patients using MDI, 85.6% initially demonstrated incorrect technique. Training with the Vitalograph AIM improved performance, but error rates remained high (78.4% at the second assessment and 65.7% at the third). In our study, training resulted in correct technique in 50.6% of MDI users. It is important to note that the effectiveness of inhaler-technique training, regardless of the method used, has inherent limitations^29,30.

Some studies, however, indicate additional benefits of using the Vitalograph AIM. Blum et al. found that 61% of patients were using an inhaler inappropriate for their abilities, and switching to a more suitable device led to significant improvements in Asthma Control Test / COPD Assessment Test scores, self-reported inhaler use, and adherence³¹. In contrast, Nixon et al. reported that most patients did not require a change of inhaler after assessment with the Vitalograph AIM. Although many initially demonstrated suboptimal technique with both MDI and DPI, training alone was sufficient to achieve improvement³². One well-known factor that is associated with a higher number of inhalation errors in patients with obstructive lung diseases is the simultaneous use of both MDI and DPI devices. This creates difficulty in learning the appropriate inspiratory force required for these two inhaler types. In this group of patients, training with the Vitalograph AIM may be particularly beneficial, as it is the only device currently available that allows assessment of three inhaler categories (DPI, MDI, and MDI with spacer).

Although the Vitalograph AIM is designed primarily for clinicians, an important advantage is the immediate visual feedback displayed to the patient, which helps identify the specific step of inhalation that requires correction. In our study, we also observed that this feedback motivated some patients to continue practicing and improve their technique.

It should be noted that inhalation technique training with Vitalograph AIM requires the use of disposable plastic inhaler simulators which are for single use, what may raise environmental concerns.

Some limitations to our study need to be acknowledged. First, the limited number of patients may have affected the results, however, our findings are consistent with the findings in other reports on larger groups. Second, we analyzed patients using MDIs or DPIs only, we did not study patients using MDIs with spacer although such an option is possible in Vitalograph AIM. This was because the number of patients using an MDI with spacer is relatively small. Third, we did not analyze the durability of the training effect. This may be an interesting direction of future studies as there are data showing that the positive effect of a single inhalation technique training is transient^10,33 and the optimal approach is repeated education^6,7. A further limitation is that the present study did not include a detailed analysis of the frequency of individual inhalation errors detected by the Vitalograph AIM before and after training, as these data are part of a larger project comparing different methods of inhalation technique assessment and are reported in a separate manuscript. Another limitation is that the study did not report the number of training attempts required to achieve proper inhalation technique, defined by the green light signal, separately for MDI and DPI users. Finally, we did not adjust the analyses for patients using multiple inhalers or for potential clustering effects, which may have influenced the precision of the estimates.

In conclusion, the assessment and training of the inhalation technique by Vitalograph AIM allows for the improvement of inhalation technique in the majority of patients incorrectly using inhalers. At the same time it highlights that barriers to improvement inhalation technique are device-specific and may require tailored training approaches. Another advantage of training with Vitalograph AIM is that it allows to identify patients in whom it is not possible to achieve improvement and in whom it may be worth considering switching to a different type of inhaler or adding a spacer to MDI. This is vital in clinical practice as inhalation technique has a key impact on the effectiveness of inhaled treatment. Considering the abundance of DPI types available on the market, future directions should focus on developing inhaler training devices which would enhance inhalation technique for different DPIs.

Abbreviations

COPD

Chronic obstructive pulmonary disease

MDI

Metered dose inhaler

DPI

Dry powder inhaler

SMI

Soft mist inhaler

FEV ₁

Forced expiratory volume in 1st second

FEV ₁%N

Forced expiratory volume in 1st second expressed as percentage of predicted value

ACT

Asthma control test

CAT

COPD assessment test

GINA

Global initiative for asthma

GOLD

Global initiative for chronic obstructive lung disease

FDA

Food and drug administration

Author contributions

MMC and MD conceived the concept of the study. All authors contributed to the design of the research. All authors were involved in data collection. All authors analyzed the data. All authors edited and approved the final version of the manuscript and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data availability

The datasets analyzed during the current study contain sensitive patient information and are therefore not publicly available. Anonymized data are available from the corresponding author on request and subject to institutional and ethical approvals.

Declarations

Ethics approval and consent to participate

Informed consent was obtained from all subjects involved in the study. The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board of Medical Warsaw University (KB/43/2019).

Consent for publication

Not applicable.

Competing interest

The authors declare no competing interest.