Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by rigidity, tremor, postural instability, bradykinesia, and autonomic dysfunction. It is a common movement disorder worldwide. Motor impairments in PD patients are not limited to the muscles of the extremities; the neck, upper respiratory tract, and respiratory muscles are also affected. The resulting pulmonary dysfunction is one of the main factors contributing to morbidity and mortality in PD patients.

Respiratory muscle exercise programs have been used to improve lung and swallowing function in patients with Parkinson's disease and other similar neurodegenerative disorders. Studies of inspiratory muscle exercise in Parkinson's patients have reported improvements in inspiratory muscle strength and endurance. Similarly, expiratory muscle exercise protocols have been shown to increase maximum expiratory pressure (MEP) and cough effectiveness. However, studies on expiratory muscle strengthening are lacking in the literature.

Positive expiratory pressure (PEP) devices are used to clear airway secretions and feature a resistance that provides resistance during exhalation. This creates a positive pressure that stabilizes the airways during exhalation and prevents airway collapse. Although there are many PEP devices available on the market, the bottle-PEP, a therapist-made device, is used because it can be produced easily and at low cost. The bottle-PEP device consists of a bottle filled with at least 10 cm of water and a tube placed inside the bottle. Although information on strengthening expiratory muscles is traditionally found in the literature, there is no data in the literature on the effect of bottle-PEP use on expiratory muscle strength, especially in Parkinson's patients. A review of the literature shows that the effect of expiratory strengthening on balance has not been studied before.

This study aimed to demonstrate the effects of the bottle-PEP device, used in addition to expiratory muscle strengthening, on expiratory muscle thickness, strength, and balance.

Our study was designed as a single-blind prospective study. Patients enrolled in the study will be divided into two groups using a computer-assisted list.

Group 1: Neurological rehabilitation program + expiratory strengthening exercises Group 2: Neurological rehabilitation program + bottle-PEP (Positive expiratory pressure (PEP))

The first group will undergo expiratory breathing strengthening exercises, which are part of routine practice, five days a week in addition to the neurological rehabilitation program for Parkinson's disease. The expiratory muscle strengthening exercises are detailed in Appendix 2. The second group will undergo bottle-PEP exercises 5 days a week, performing 25 forced expirations after deep inspirations using a homemade bottle-PEP device, in addition to the neurological rehabilitation program for Parkinson's disease. The bottle-PEP device is created by filling a 1.5-liter plastic, empty, and clean bottle with 10 cm of water and then immersing an aspiration tube into this water. After deep inspiration, the patient takes the aspiration tube into their mouth and performs forced expiration against the water. The exercises are designed as an 8-week home program. Both the neurological rehabilitation program and expiratory breathing strengthening exercises are routine programs.

Patients will be taught how to use the bottle-PEP and perform the exercises face-to-face during the first visit.

To monitor the implementation of this program, a researcher will confirm that the exercises are being performed correctly via video calls with the participants over the internet.

Patients will be evaluated at the beginning of the study, at the end of the 8th week, and 8 weeks after completing the exercise program.

Data to be Evaluated for Patients:

1. Patients' demographic data (age, gender, height, weight, etc.), comorbidities, and medications used will be recorded on the follow-up form.

2. Respiratory Function Test:

   Respiratory function tests are a method used to detect diseases of the respiratory tract and lungs and to examine the mechanical properties of these organs. The main purposes of this test are to obtain numerical data related to respiratory tract and lung diseases and to differentiate between obstructive and restrictive disorders. During a simple spirometric measurement, the mouthpiece is placed in the patient's mouth so that no air can enter. The spirometric measurement is then performed as follows: First, the patient takes a deep breath, followed by a forceful and deep exhalation. The forced exhalation is repeated several times within a specific time interval. Numerical data is obtained with the help of an electronic device connected to the mouthpiece, and volume-time and flow-volume curves for the patient are obtained. These curves are used by physicians. Some of the data obtained from these curves are as follows:

   Forced vital capacity (FVC): This refers to the amount of air expelled with a forced and rapid exhalation after taking a deep breath following quiet breathing. This test is mostly performed to determine expiratory capacity. The procedure is repeated several times, and the results obtained are used to create volume-time or flow-volume curves.

   FEV1(Forced Expiratory Volume in 1 second): This is the forced vital capacity value measured during the first second of a forced exhalation. This value, expressed as volume, is actually an indicator of flow rate. In healthy individuals, 75-80% of the lung gas volume is expelled based on this value measured in the first second, while in diseases associated with large airway obstruction, the FEV1 value is lower than normal.

   The FEV₁/FVC ratio is an important parameter in distinguishing between obstructive and restrictive lung diseases.

3. Maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) measurements:

   An electronic mouth pressure measurement device (Micro Medical MicroMPM, UK) is used to measure respiratory muscle strength. During MIP measurement, the patient is asked to perform maximum expiration, followed by 1-3 seconds of maximum inspiration after the patient's nose is closed with a clip. During MEP measurement, the patient is asked to perform maximum inspiration, followed by 1-3 seconds of maximum expiration after the patient's nose is closed with a clip. Black and Hyatt's equations are used as a reference for interpreting the measurements. The measurements are repeated three times with no difference greater than 10 cmH2O or 10%, and the highest value is used for statistical analysis.

4. Ultrasonographic measurement of diaphragm thickness and intercostal muscle thickness Diaphragm thickness: All patients will be placed in the supine position, and the probe will be positioned in the subcostal area between the right midclavicular line and the anterior axillary line. The probe will be directed toward the head and back to reach the middle and posterior third of the diaphragm. After obtaining an ideal 2D image, the diaphragm will be evaluated and measured at the end points of inspiration and expiration. A low-frequency convex probe of 2-5 MHz will be used during measurements.

   Diaphragm contractility can be assessed by changes in diaphragm thickness (diaphragm thickness ratio (TR) measured using ultrasonography or diaphragm thickness fraction (DTf)).

   TR = end-inspiration diaphragm thickness / end-expiration diaphragm thickness DTf = (end-inspiration diaphragm thickness - end-expiration diaphragm thickness) / end-expiration diaphragm thickness x 100

   Intercostal muscle thickness: All patients will be placed in the supine position, and data will be obtained from the 2nd intercostal space-2 to 4 cm lateral to the sternum-which, as previously demonstrated by De Troyer, A, and colleagues, is the most stable and prominent interval for evaluating the parasternal intercostal muscles. After obtaining an ideal 2D image, the intercostal muscles will be evaluated and measured at the end points of inspiration and expiration. A 6-13 MHz high-frequency linear probe placed vertically against the chest wall and applied with minimal pressure will be used.

   Intercostal muscle contractility can be assessed by changes in muscle thickness (fraction of intercostal thickness measured using ultrasonography (ICTf)).

   ICTf = (end-inspiration intercostal muscle thickness - end-expiration intercostal muscle thickness) / end-expiration intercostal muscle thickness x 100%

5. Berg Balance Scale:

   This scale consists of 14 tests that measure the ability to maintain balance during different positions, postural changes, and movement. The assessment is based on the person's ability to perform each test independently and/or within a specific time or distance. Scoring ranges from 0 to 4 points. 0 = unable to perform, 4 = normal performance. The highest score is 56.

   A score between 0 and 20 indicates that the person is wheelchair-dependent and has a 100% risk of falling.

   A score between 21 and 40 indicates that the person can walk with assistance due to the risk of falling.

   A score between 41 and 56 indicates that the person can walk independently with a very low risk of falling.

6. Parkinson's Disease Quality of Life Questionnaire (PDQ-39):

This scale, used to assess patients' quality of life, consists of 39 multiple-choice items covering 8 factors (mobility, activities of daily living, emotional well-being, stigma, social support, cognition, communication, physical discomfort). Participants are asked to answer the questions based on their experiences in the past month. The total score for each dimension ranges from 0 (never had difficulty) to 100 (always had difficulty). Lower scores reflect better health status.

Inclusion Criteria:

• Patients with a confirmed Parkinson's diagnosis who are being monitored
• Those aged 18-75
• Patients who are ambulatory

Exclusion Criteria:

• Patients with acquired primary motor neuron disease (ischemic/hemorrhagic stroke, intracranial mass) and additional neurological diagnoses
• Patients with hearing and cognitive impairments that prevent them from understanding or performing the exercise program
• Presence of concomitant acute or chronic lung disease
• History of thoracic or abdominal surgery
• Severe heart disease
• Active cancer
• Mini-Mental State Examination (MMSE) score ≤ 24
• Active smoking

Patients aged 18-75 with a diagnosis of Parkinson's disease who are ambulatory