- Physiology:
- Mountaineers,
- Exercise,
- Hyperpyrexia
- Anemia.
- Respiratory:
- Airway obstruction
- Bronchial asthma
- Chronic obstructive lung disease
- Pulmonary infections
- Pulmonary edema
- Pulmonary embolism
- Bronchogenic carcinoma
- Pleural effusion
- Pneumothorax
- Cardiac:
- Acute myocardial infarction
- Valvular heart disease
- Left ventricular failure
- Congenital cyanotic heart disease
- Metabolic:
- Diabetes
- Uremia
- Hypokalemia
- Neurological
- Respiratory center depression as in syringobulbia
- Motor neuron disease
- Guillain Barre syndrome
- Bulbar polio
- Myasthenia gravis
- Psychogenic