As a result of dystrophin deficiency, patients with DMD experience a progressive loss of muscle fibre that eventually affects the respiratory muscles. The resulting respiratory failure is the most common cause of premature death in patients with DMD.
Respiratory muscles are progressively compromised in children with DMD, the expiratory muscles being the most commonly affected. Even short periods of physical inactivity can contribute to muscle weakness and reduced respiratory capacity. There is evidence that breathing exercises can improve respiratory function in patients with DMD.