Increased airways resistance (chronic obstructive pulmonary disease, asthma, suffocation) Reduced breathing effort (drug effects, brain stem lesion, extreme obesity) A decrease in the area of the lung available for gas exchange (such as in chronic bronchitis) Neuromuscular problems (Guillain–Barré syndrome,[3] motor neuron disease) Deformed (kyphoscoliosis), rigid (ankylosing spondylitis), or flail chest.[3]