Disorders such as myasthenia gravis, amyotrophic lateral sclerosis, muscular dystrophy, poliomyelitis or post-polio syndrome, Guillain-Barre, tetanus, cervical spinal cord injury, botulism etc. may cause ventilatory failure. These usually have a normal ventilatory drive and normal or near-normal lung function. Most of these disorders cause respiratory muscle weakness, so these patients have trouble coughing and clearing secretions. As a result they tend to develop atelectasis and pneumonia. If the glottic response is weak, they may also have a risk of aspiration. Ventilation is most often needed because of progressive respiratory muscle weakness that eventually leads to respiratory failure (e.g., Guillain-Barre and myasthenia gravis).
 
Because these patients often have normal lung function, they are at low risk for barotrauma and are most comfortable when ventilated with higher V T values (12 to 15 mL/kg) and high inspiratory flow rates of >60 L/min using a constant flow or descending ramp when VV is used. Patients with spinal cord injuries such as high quadriplegia require full ventilatory support. Other patients only require partial support until their own breathing capacity returns, such as with myasthenia gravis.