Abnormality of the chest wall

A chest wound, deformities resulting from chest surgery, injury, morbid obesity, or scoliosis

Abnormality of lung tissue

Acute respiratory distress syndrome (ARDS), a reaction to a medication or illicit drug pneumonia, pulmonary edema (excess fluid in the lungs) due to heart failure or kidney failure, pulmonary fibrosis, radiation, sarcoidosis, or widespread tumors

Airflow obstruction

Asthma, bronchiectasis, bronchiolitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, or inhaled foreign objects

Muscle weakness

Amyotrophic lateral sclerosis (ALS), certain strokes, Guillain-Barré syndrome, muscular dystrophy, myasthenia gravis, polio, polymyositis, or spinal cord injury

Poor breathing (decrease in the drive to breathe)

Intoxication with alcohol, illicit drugs, or a medication, hypothyroidism, obesity, or sleep apnea