Dynamic POCUS of Diaphragm Function to Predict Respiratory Failure in Septic Shock

Septic shock remains a major cause of morbidity and mortality among critically ill patients. Respiratory failure is a frequent and serious complication, resulting from a combination of sepsis-induced lung injury, acute respiratory distress syndrome, respiratory muscle dysfunction, and sepsis-induced myopathy. The diaphragm is the principal muscle of respiration and may be significantly affected during sepsis. Systemic inflammation, altered microcirculation, mitochondrial dysfunction, electrolyte abnormalities, prolonged immobilization, sedation, and mechanical ventilation can contribute to diaphragmatic dysfunction. Such dysfunction may impair spontaneous breathing, increase the risk of respiratory failure, prolong mechanical ventilation, and contribute to unsuccessful weaning and adverse clinical outcomes. Point-of-care ultrasound (POCUS) provides a non-invasive, bedside, radiation-free method for assessing diaphragmatic structure and function. The most commonly used parameters include diaphragmatic excursion (DE), diaphragmatic thickness, and diaphragmatic thickening fraction (DTF). Most available studies have assessed diaphragmatic function at a single point in time, particularly during weaning from mechanical ventilation. However, limited evidence exists regarding the prognostic value of serial dynamic assessment of diaphragmatic function in patients with septic shock from the early stages of ICU admission.

Dynamic changes in diaphragmatic function may provide more clinically meaningful information than a single measurement. Therefore, serial POCUS assessment may help identify patients at high risk of respiratory failure and predict important clinical outcomes.

Inclusion criteria

• Age ≥ 18 years old.
• Patients with septic shock.
• Patients with ICU admission during study period.
• Expected ICU stay for at least 72 hours.
• Informed consent from the patient or legal guardian when required.

Exclusion criteria

• Age less than 18 years old.
• Pre-existing neuromuscular disorders affecting respiratory muscles.
• Known diaphragmatic paralysis or diaphragmatic palsy.
• Significant phrenic nerve injury.
• Cervical spinal cord injury.
• Advanced chronic neuromuscular disease.
• Previous major thoracic or diaphragmatic surgery.
• Severe chest wall deformity.
• Conditions preventing adequate diaphragmatic ultrasound assessment.
• Pregnancy, if required by local ethical policy.
• Patients with limitations of care that preclude full respiratory support.
• Refusal of consent where consent is required.