Upper airway stimulator systems for obstructive sleep apnea

A system for treating obstructive sleep apnea comprising:

• an apnea sensor configured to generate an apnea signal;
• a stimulator configured to deliver stimulation to a nerve which innervates an upper airway muscle;
• and
• a controller coupled to the apnea sensor and the stimulator;
• wherein the controller is configured to receive the apnea signal from the apnea sensor;
• wherein the controller is configured to determine whether an apneic event is detected based on the apnea signal;
• wherein the controller is configured to cause the stimulator to apply primary simulation to the nerve if no apneic event is detected;
• and
• wherein the controller is configured to cause the stimulator to apply secondary stimulation to the nerve upon detecting an apneic event.