Investigation of the Effect of Inspiratory Muscle Training and Dual-Task Inspiratory Muscle Training on Cognitive Functions in Heart Failure

Global cognitive function will be assessed using the Montreal Cognitive Assessment (MoCA), 0-30 point screening tool evaluating multiple cognitive domains including attention, memory, executive functions, visuospatial abilities, and language. Higher scores indicate better cognitive performance. The assessment will be administered by a certified physiotherapist.

Subjective cognitive function will be assessed using the Cognitive Failures Questionnaire (CFQ), which evaluates perceived cognitive performance over the past 6 months. The questionnaire consists of 25 items rated on a 5-point Likert scale (0-4), with total scores ranging from 0 to 100. Higher scores indicate greater perceived cognitive impairment.

Attention and executive function will be assessed using a Stroop Test (The Scientific and Technological Research Council of Türkiye, Basic Sciences Research Group version), a standardized tool evaluating selective attention, cognitive flexibility, and psychomotor speed. The test consists of five sections, and completion time, as well as the number of correct and incorrect responses, will be recorded for each section. Longer completion times and higher error rates indicate poorer performance.

Verbal memory will be assessed using the Öktem Verbal Memory Processes Test, which evaluates different components of verbal memory including learning, delayed recall, and recognition. The test involves repeated presentation of a target word list, followed by delayed recall and recognition tasks. Performance will be quantified using learning, spontaneous recall, and recognition scores. The learning score reflects total words recalled across repeated trials (maximum 15). Spontaneous recall is assessed approximately 40 minutes after the learning phase, during which participants are asked to recall the words without cueing. Recognition performance is based on identifying previously presented words among distractors. Higher scores indicate better verbal memory performance.

Reaction time will be assessed using a BlazePod reaction kits. Participants, seated in front of a table, will respond to randomly illuminated light stimuli by tapping the lights as quickly as possible for 30 seconds using one hand. The system consists of four reaction pods positioned in a straight line at 20 cm intervals. Outcome measures will include total number of hits, total reaction time, and mean reaction time per stimulus. Missed responses will be recorded when the light deactivates before being tapped within 4 seconds. Lower reaction time indicates better performance.

Forced vital capacity (FVC) will be assessed using spirometry according to American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines. It will be recorded from three acceptable maneuvers performed in a seated position, and the highest value will be used for analysis.

Forced expiratory volume in 1 second (FEV1) will be assessed using spirometry according to ATS/ERS guidelines. It will be recorded from three acceptable maneuvers performed in a seated position, and the highest value will be used for analysis.

FEV1/FVC ratio will be assessed using spirometry according to ATS/ERS guidelines. It will be recorded from three acceptable maneuvers performed in a seated position, and the highest value will be used for analysis.

Peak expiratory flow (PEF) will be assessed using spirometry according to ATS/ERS guidelines. It will be recorded from three acceptable maneuvers performed in a seated position, and the highest value will be used for analysis.

Forced expiratory flow at 25-75% of FVC (FEF25-75) will be assessed using spirometry according to ATS/ERS guidelines. It will be recorded from three acceptable maneuvers performed in a seated position, and the highest value will be used for analysis.

Maximal inspiratory pressure (MIP) will be assessed using a portable electronic mouth pressure device (MicroRPM; Micro Medical, UK), according to ATS/ERS guidelines. It will be measured in the seated position using a mouthpiece with nasal occlusion. Participants will perform maximal inspiratory effort for at least 2 seconds against an occluded airway. The highest value from three acceptable maneuvers with <10% variability will be recorded in cmH₂O and as a percentage of predicted values using Black and Hyatt reference equations. Higher values indicate better inspiratory muscle strength.

Maximal expiratory pressure (MEP) will be assessed using a portable electronic mouth pressure device (MicroRPM; Micro Medical, UK), according to ATS/ERS guidelines. It will be measured in the seated position using a mouthpiece with nasal occlusion. Participants will perform maximal expiratory effort for at least 2 seconds against an occluded airway. The highest value from three acceptable maneuvers with <10% variability will be recorded in cmH₂O and as a percentage of predicted values using Black and Hyatt reference equations. Higher values indicate better expiratory muscle strength.

Respiratory muscle endurance will be assessed using a constant-load threshold loading test with a pressure threshold device (POWERbreathe Classic Light Resistance, POWERbreathe International Ltd., UK). The test will be performed at 60% of MIP. Participants will breathe through the device for up to 10 minutes, and endurance will be recorded as the time sustained (seconds) and achieved pressure load (cmH₂O). Higher endurance time indicates better respiratory muscle endurance.

Exercise capacity will be assessed using the 6-minute walk test (6MWT) according to ATS guidelines. Participants will be instructed to walk as far as possible for 6 minutes along a 30-meter corridor at a self-paced speed. A standardized rest period will be provided prior to testing. Total walking distance will be recorded in meters. Higher walking distance indicates better exercise capacity.

Dyspnea will be assessed using the Modified Medical Research Council (mMRC) Dyspnea Scale, a 0-4 point scale based on the level of physical activity that induces breathlessness. Higher scores indicate greater severity of dyspnea.

Fatigue will be assessed using the Fatigue Severity Scale (FSS), a 9-item scale evaluating fatigue severity over the past week. Each item is rated on a 7-point Likert scale (1-7), and the total score is calculated by averaging item scores. A score ≥4 indicates severe fatigue. Higher scores indicate greater fatigue severity.

Fractional exhaled nitric oxide (FeNO) will be measured using a NObreath® device (Bedfont Scientific Ltd., UK) according to the ATS guidelines. Measurements will be performed with controlled expiratory flow, and mean values will be recorded. Participants will perform controlled exhalation at a constant flow rate (50 mL/s) following standardized pre-test conditions. The mean of two acceptable measurements will be recorded as FeNO (parts per billion, ppb).

Frailty will be assessed using the Edmonton Frail Scale, a 17-point scale evaluating multiple domains including cognition, general health status, functional independence, and social support. Scores range from 0 to 17, with higher scores indicating greater frailty severity.

Physical performance will be assessed using the Short Physical Performance Battery (SPPB), including balance tests, 4-meter gait speed, and chair stand tests. Total scores range from 0 to 12, with higher scores indicating better performance.

Quality of life will be assessed using the Minnesota Living with Heart Failure Questionnaire, a 21-item disease-specific scale evaluating the physical and emotional impact of the disease over the past 4 weeks. Each item is scored from 0 to 5, with total scores ranging from 0 to 105. Higher scores indicate worse quality of life.

Anxiety and depression will be evaluated using the Hospital Anxiety and Depression Scale (HADS), a 14-item questionnaire with two subscales assessing anxiety and depression. Each subscale ranges from 0 to 21, with higher scores indicating greater symptom severity.