Inspire Medical Systems, maker of an implanted device to treat sleep apnea, said Thursday that it has raised $40 million in venture capital funding.

The Maple Grove-based firm, which recently won approval for the treatment from the Food and Drug Administration, will use this fifth round of funding to get the treatment into hospitals and doctors' offices across the country.

"This is to fund the commercialization of therapy in the United States, which is really exciting," Tim Herbert, the company's CEO, said.

Inspire has 40 employees, Herbert said, and will hire a sales force of 12 to work with hospitals and insurance companies.

The latest round of funding was led by OrbiMed in New York, with Johnson & Johnson Development Corp. and ­Aperture Venture Partners as new investors in this round.

Kleiner Perkins Caufield & Byers, US Venture Partners, Synergy Life Science Partners, Medtronic, GDN Holdings and TGap Ventures have all invested in the firm, which was spun off by Medtronic in 2007.

Inspire also announced Thursday that Richard Buchholz, a medical device industry veteran, has been appointed chief financial officer.

Sleep apnea, a condition in which people stop breathing while asleep because their airways temporarily close, causes people to sleep poorly and raises the long-term risk of heart attack, stroke, high blood pressure and heart failure.

Inspire's "Upper Airway Stimulation" therapy uses an implantable device that stimulates a nerve in the neck to move the tongue slightly forward, which keeps breathing passageways open without waking the patient.

A small, handheld remote is used to turn the therapy on before bed. When activated, the device senses breathing patterns and delivers mild stimulation to key airway muscles, which keeps the airway open.

At around $30,000, the method is considerably more expensive than existing treatments for sleep apnea and, as a result, is intended only for patients who can't adapt to those treatments, Herbert said.

The most common sleep apnea treatment is a $2,000 device prescribed to about 2 million Americans a year that uses a breathing mask and an air-pressure machine to keep breathing passages open.

Inspire's device and therapy will be available for U.S. patients in the second half of this year, the company said.