This study aims to evaluate the effect of respiratory physiotherapy on diaphragm thickness in patients receiving mechanical ventilation support in the intensive care unit. Thinning and dysfunction of the diaphragm muscle observed during mechanical ventilation complicate the extubation process and increase the risk of respiratory failure in patients. Diaphragm dysfunction prolongs ventilator use and increases ICU mortality. The main objective of this research is to determine whether respiratory physiotherapy has protective or ameliorative effects on diaphragm muscle structure and function, to optimize the ventilator weaning process, and to provide scientific contributions to the field of respiratory rehabilitation. Changes in diaphragm thickness will be objectively evaluated using ultrasonography, and the aim is to obtain evidence-based data on the effectiveness of respiratory physiotherapy.

Mechanical ventilation (MV) is a widely used basic life support method to provide respiratory support to individuals with life-threatening illnesses in intensive care units. However, long-term MV application and inability to wean from the ventilator are considered two of the most important risk factors increasing morbidity and mortality rates in intensive care patients. In addition, this situation creates a serious economic burden for the healthcare system. Despite the life-saving effects of MV, complications such as ventilator-associated pneumonia, atelectasis, barotrauma/volutrauma, patient-ventilator asynchrony, and pulmonary embolism can develop during the application process. Furthermore, the weaning process from mechanical ventilation is critical for enabling the patient to transition to spontaneous breathing and requires the fulfillment of objective criteria such as arterial pH, oxygenation, metabolic stability, and elimination of the underlying cause . The diaphragm, the primary muscle of the respiratory system, plays a decisive role in the successful termination of mechanical ventilation. Prolonged mechanical ventilation (MV) support leads to decreased diaphragm activity due to insufficient or excessive ventilator pressure, patient-ventilator mismatch, critical illness polyneuropathy, and systemic infections, resulting in diaphragm atrophy and dysfunction. This condition is defined as ventilator-associated diaphragm dysfunction (VIDD) and leads to prolonged MV duration, extubation failure, and increased mortality. The literature shows that VIDD is one of the most important determinants of long-term MV dependence and negatively affects clinical outcomes .

In recent years, ultrasonography (USG), a non-invasive, reliable, and reproducible method for evaluating diaphragm function, has come to the forefront. Measuring diaphragm thickness with USG provides valuable information both for the detection of VIDD and for planning the timing of extubation. In addition, early mobilization and respiratory physiotherapy applications have been shown to be effective in increasing consciousness levels, reducing complications, and shortening MV duration and ICU stay in intensive care patients . However, the effect of early respiratory physiotherapy on diaphragm structure and function has not yet been sufficiently investigated. Therefore, this study aims to evaluate the effect of respiratory physiotherapy on diaphragm thickness in intensive care patients with objective data and to determine whether it contributes to the prevention of VIDD development.

Inclusion Criteria:

• Age ≥ 18 years
• Mechanically ventilated for at least 5 days
• Hemodynamically stable
• Unconscious (Glasgow Coma Scale indicating impaired consciousness)
• Informed consent obtained from legal representatives

Exclusion Criteria:

• Neuromuscular disease
• Traumatic diaphragm injury
• Thoracic deformity causing mechanical impairment of respiration
• Terminal-stage patients
• Patients in whom respiratory physiotherapy is contraindicated
• Presence of a cardiac pacemaker or implantable cardioverter-defibrillator (ICD)

Adult patients receiving invasive mechanical ventilation in the Anesthesia Intensive Care Unit of Hitit University Faculty of Medicine, Erol Olçok Training and Research Hospital, who meet the inclusion criteria and whose legal representatives have provided informed consent.