Methods and systems for treating sleep apnea using electrical stimulation to a patient's upper and/or lower respiratory nerve or muscle are described. A stimulation regimen can be used to achieve upper airway patency and/or rhythmic air flow in a coordinated fashion during sleep. In some cases, diaphragm activity is monitored to determine whether sufficient upper airway patency and/or rhythmic air flow is achieved and maintained. The stimulation regimen may be adjusted based on the diaphragm activity. In some cases, the system includes modularized components so that the components can be customized to an individual's needs.
