Chronic obstructive pulmonary disease (COPD) is often accompanied by various comorbidities, including structural and functional changes in both respiratory and peripheral muscles. Ultrasound offers a non-invasive method for evaluating muscle impairment, providing valuable insights into disease progression. The quadriceps contractility index (Qci), assessed via ultrasound, is a quick, simple, and reliable measure of muscle function. Research indicates a strong correlation between Qci and COPD severity, clinical symptoms, and respiratory muscle performance. Additionally, ultrasound allows for the dynamic assessment of diaphragm function by measuring its movement amplitude, contraction speed, and the duration of each contraction phase. Given its ability to evaluate muscle deterioration, ultrasound presents a promising tool for assessing disease severity in COPD patients.