The Ultrasonographic Evaluation of Abdominal Accessory Respiratory Muscle Thickness in Patients With Parkinson's Disease: Correlation With Disease Severity and Expiratory Respiratory Muscle Strength

Maximal Expiratory Pressure (MEP) Measurement

MEP assesses the strength of abdominal and accessory expiratory muscles. During the maneuver, the patient is asked to blow forcefully into the mouthpiece for at least 1.5 seconds, as if inflating a balloon. The pressure generated during rapid expiration is measured by sensors, and after 1.5-2.0 seconds the shutter opens, ending the test. If multiple tests are conducted, the patient rests for at least 1 minute between trials, and a maximum of 3-5 trials are performed. Differences greater than 10 cmH₂O between trials are not accepted. The highest measurement is reported together with the predicted value. The MicroRPM Respiratory Pressure Meter (MicroDirect, USA) will be used.

Maximal Inspiratory Pressure (MIP) Measurement

MIP is used to assess the strength of inspiratory respiratory muscles. During the test, the patient is instructed to exhale down to residual volume. MIP is defined as the maximum negative pressure measured during a maximal inspiratory effort performed after reaching residual volume. Measurements will be taken using the MicroRPM Respiratory Pressure Meter (MicroDirect, USA).

Ultrasonographic Assessment of Abdominal Accessory Respiratory Muscles

Ultrasound measurements of the rectus abdominis, external oblique, internal oblique, and transversus abdominis muscles will be performed. Measurements will be taken in the supine position with the patient lying on their back, eyes facing upward, arms resting symmetrically beside the trunk, and lower extremities in full knee extension with an intermalleolar distance of 10 cm. Muscle thickness will be recorded at the end of normal expiration and at the end of forced expiration.

Six Minute Walk Test (6MWT)

The 6MWT is performed in a corridor with a flat, firm surface that is at least 30 meters long and marked at 3-meter intervals. Turning points should be indicated with a colored object. Start and finish lines are designated. The patient is asked to walk the longest distance possible within 6 minutes. The distance walked is measured and recorded.

Modified Hoehn and Yahr Staging

This scale, developed by Margaret Hoehn and Melvin Yahr in 1967, is used to determine the severity of Parkinson's disease. It evaluates patient functionality, symptom laterality, pattern of involvement, and balance. The scoring ranges from 1 to 5. The Modified Hoehn \& Yahr staging system includes additional stages 1.5 and 2.5. As the stage progresses, symptoms become more widespread, balance impairment and functional limitation increase; in the later stages, the patient becomes dependent on assistance or care.