Inspiratory muscle dysfunction in patients with severe obstructive sleep apnoea

Area of Science:

• Respiratory Medicine
• Neurology
• Exercise Physiology

Background:

• Obstructive sleep apnoea (OSA) involves airway obstruction and intermittent hypoxia, potentially impairing inspiratory muscle function.
• Peripheral muscle dysfunction may contribute to the overall health impact of severe OSA.

Purpose of the Study:

• To compare the strength, endurance, and fatigability of inspiratory muscles and peripheral limb muscles (knee extensors) in newly diagnosed severe OSA patients versus healthy controls.
• To investigate the neuromuscular response to fatigue in these muscle groups using electromyography and magnetic stimulation.

Main Methods:

• Recruitment of newly diagnosed severe OSA patients and matched healthy controls.
• Assessment of maximal voluntary contraction strength and endurance for inspiratory muscles and knee extensors.
• Fatigue testing with simultaneous surface electromyography (EMG) of the diaphragm and vastus lateralis, alongside magnetic stimulation to evaluate neuromuscular excitability.

Main Results:

• OSA patients demonstrated significantly lower strength and endurance in both inspiratory muscles and knee extensors compared to controls.
• A significant decrease in the fatigue index was observed exclusively in the inspiratory muscles of OSA patients.
• Following fatigue testing, OSA patients showed increased diaphragm activation latencies and decreased amplitudes in response to magnetic stimulation, unlike the vastus lateralis.

Conclusions:

• Severe OSA is associated with generalized peripheral muscle weakness and reduced endurance.
• Inspiratory muscles in severe OSA patients exhibit specific signs of increased fatigability and impaired neuromuscular function, suggesting a direct impact of the condition on these vital muscles.