Somers - Figure 15
Airflow
FIG. 15: This schematic in this Figure shows what to expect in sympathetic nervous activity levels in patients with OSA. These patients, because they momentarily cease breathing, have a fall in oxygen (O2) (hypoxemia) and a rise in carbon dioxide (CO2) (hypercapnia). Hypoxemia stimulates peripheral chemoreceptors in the internal carotid artery and carotid sinus. Hypercapnia stimulates central chemoreceptors in the brainstem. The result is hyperventilation and sympathetic nervous activation.
At this point the hyperventilation acts by stretching the thoracic afferents to reign in, or inhibit, the level of sympathetic nervous activity. The problem in apnea is low O2, high CO2, but the person is not breathing; as a result the person does not have hyperventilation stretching the chest wall and on thoracic afferents, which would cause inhibition of sympathetic nervous activity, so the result is excessively high levels of sympathetic drive.
