Abnormality of the chest wall

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

Abnormality of lung tissue

Acute respiratory distress syndrome (ARDS), a drug reaction, 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)

Drug or alcohol intoxication, hypothyroidism, obesity, or sleep apnea