Nutritional Risk and Diaphragmatic Thickness in Mechanically Ventilated COPD Patients

Malnutrition is a prevalent comorbidity in chronic obstructive pulmonary disease (COPD) associated with lower exercise tolerance, decreased pulmonary function, and increased mortality. In the intensive care unit (ICU), acute exacerbations requiring invasive mechanical ventilation frequently lead to accelerated muscle wasting and ventilator-induced diaphragmatic dysfunction. Combining bedside clinical risk scoring, peripheral anthropometry, and diaphragmatic ultrasonography provides a comprehensive approach to evaluating nutritional and functional reserve.

Eligible patients aged 60 years or older admitted with acute exacerbations of COPD requiring invasive mechanical ventilation for at least 48 hours will be prospectively enrolled.

Clinical and Severity Scoring (Day 1): Within the first 24 hours of admission and ventilation initiation, baseline demographic data, arterial blood gases, and severity scores will be recorded. Scores include the modified Nutrition Risk in the Critically Ill (mNUTRIC; range 0-9, where ≥ 5 defines high nutritional risk), Sequential Organ Failure Assessment (SOFA; range 0-24), and Acute Physiology and Chronic Health Evaluation II (APACHE II; range 0-71).

Anthropometric Measurements: Mid-upper arm circumference (MUAC) and calf circumference (CC) will be performed by a single investigator using a non-stretchable measuring tape recorded to the nearest 0.1 cm. Values will be obtained at baseline (within 24 hours), day 7 (or at extubation/discharge if earlier), and on the day of weaning.

Diaphragmatic Ultrasonography: Bedside point-of-care ultrasound using a high-frequency linear probe (7-13 MHz) will evaluate the diaphragm in the zone of apposition at the 8th-9th intercostal space on the right hemithorax. Diaphragm thickness at end-expiration (Tdi,ee) and end-inspiration (Tdi,pi) will be measured in B-mode/M-mode (averaging three consecutive cycles) at baseline, day 7, and during spontaneous breathing trials/weaning attempts.

Inclusion criteria

• Adult patients aged ≥ 60 years
• Confirmed diagnosis of Chronic Obstructive Pulmonary Disease (COPD) according to GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria
• Admission to the intensive care unit (ICU) or respiratory ICU for acute exacerbation of COPD
• Requirement for invasive mechanical ventilation for ≥ 48 hours
• Provision of informed consent by the patient or a first-degree relative/legal guardian

Exclusion criteria

• Pre-existing neuromuscular disease affecting diaphragmatic or peripheral muscle function (e.g., myasthenia gravis, muscular dystrophy, poliomyelitis, motor neuron disease)
• Known diaphragmatic paralysis or phrenic nerve injury predating admission
• Severe limb edema, amputation, or lower-limb deformity precluding valid anthropometric measurement
• Terminal illness or malignancy with an expected survival of < 48 hours
• Duration of mechanical ventilation < 48 hours, or death/extubation occurring before baseline assessment completion
• Subcutaneous emphysema or thoracic/abdominal wall pathology precluding adequate diaphragmatic ultrasound acoustic windows