Serial Diaphragm Ultrasound Evaluation During Inspiratory Muscle Training in Prolonged Mechanical Ventilation

Diaphragm dysfunction contributes to prolonged mechanical ventilation (PMV) and difficult weaning. Inspiratory muscle training (IMT) may improve respiratory muscle performance, while serial diaphragm ultrasound offers a bedside method for monitoring diaphragmatic recovery. This study used diaphragm ultrasound to evaluate the effects of high- versus low-intensity IMT in patients with PMV and diaphragm dysfunction. In this prospective study, patients received high- or low-intensity IMT for up to 2 weeks or until ventilator liberation. Respiratory mechanics, including respiratory rate, tidal volume, minute ventilation, rapid shallow breathing index, and maximal inspiratory pressure, were assessed twice weekly. Diaphragm excursion and thickening fraction were also measured serially after IMT initiation. Changes in respiratory physiological parameters and diaphragm ultrasound measurements were compared between the two IMT groups, and differences in ventilator liberation outcomes were evaluated.

Inclusion Criteria: 1. Willing and able to provide written informed consent. 2. Adults aged \>20 years. 3. Patients requiring mechanical ventilation for \>21 days and admitted to the Respiratory Care Center (RCC). 4. Hemodynamically stable and not receiving vasopressor therapy. 5. Clinically stable and considered by the attending physician to be ready to begin weaning from mechanical ventilation. Ventilator settings must meet all of the following criteria: (1) Fraction of inspired oxygen (FiO₂) \< 0.60. (2) Positive end-expiratory pressure (PEEP) ≤10 cmH₂O. (3) Able to trigger spontaneous breaths on the ventilator. (4) Respiratory rate \