Muscle Oxygenation in Patients With COPD Exacerbation

Chronic obstructive pulmonary disease (COPD) is characterized by recurrent acute exacerbations that negatively affect patients' quality of life and accelerate lung function decline. Severe exacerbations requiring hospitalization pose a significant mortality risk both during admission and in the following year.

During acute exacerbations, maximal pressure generation by respiratory muscles declines, and respiratory muscle efficiency-particularly of the diaphragm-is significantly reduced. Acute dynamic hyperinflation further shortens the inspiratory muscles, leading to functional muscle weakness. Consequently, accessory respiratory muscles are recruited maximally, often causing notable alterations in chest-wall and abdominal kinematics. Due to the requirement of spending a higher proportion of their maximum capacity with each breath, these patients face an elevated risk of developing respiratory muscle fatigue. Exacerbations lead to severe hypoxemia caused by impaired pulmonary gas exchange, driven primarily by ventilation-perfusion mismatch and increased tissue oxygen consumption. Acute hypoxemia exacerbates muscle weakness and impairs skeletal muscle function. Even after discharge from respiratory intensive care units following severe exacerbations, persistent respiratory muscle dysfunction is observed in more than a third of patients, requiring additional care and rehabilitation.

Physiological factors such as impaired gas exchange, reduced perfusion, and systemic inflammation during exacerbations substantially impact muscle oxygenation. Reduced arterial oxygen content diminishes oxygen availability to peripheral tissues and muscles. Simultaneously, the metabolic demands of both respiratory and peripheral muscles increase due to the heightened work of breathing and systemic stress.

This study aims to investigate respiratory and peripheral muscle oxygenation in patients with AECOPD and stable COPD, evaluating underlying physiological changes and assessing the impact of exacerbations on muscle function and oxygenation dynamics.

The aim of study is to investigate respiratory and peripheral muscle oxygenation in patients with AECOPD.

Inclusion criteria

Acute Exacerbation Group: 1. Diagnosis of Chronic Obstructive Pulmonary Disease (COPD) 2. Hospital admission or presentation due to an acute exacerbation of COPD 3. Age 40 years or older 4. Voluntary agreement to participate with signed written informed consent Clinically Stable Group: 1. Diagnosis of COPD (GOLD Stage 1, 2, 3, or 4) 2. Age 40 years or older 3. Clinically stable condition for at least the past 4 weeks without acute exacerbations 4. Voluntary agreement to participate with signed written informed consent

Exclusion criteria

Acute Exacerbation Group: 1. Active participation in a formal pulmonary rehabilitation program 2. Co-existing neurological disorders 3. Heart failure classified as New York Heart Association (NYHA) Class III or IV 4. Unstable mental or cognitive status (Mini-Mental State Examination [MMSE] score ≤24) 5. History of surgical intervention within the past three months 6. Presence of malignant conditions .

Clinically Stable Group: 1. History of lung cancer, sarcoidosis, tuberculosis, and/or prior lung surgery 2. Known mental or cognitive impairment.