There's been a robust IPO market thus far in 2018, largely driven by tech unicorns and biotechs. In fact, the first quarter saw the most IPO money raised during a given quarter for the last four years. But med tech has been almost entirely sidelined from participation, until now. Sleep apnea player Inspire Medical Systems Inc. has raised $108 million in an upsized IPO. The Minneapolis-based spinout of Medtronic plc priced at the top of its proposed range at $16 and increased the number of shares sold to 6.75 million from 5 million. Most promisingly, in early trading on its first day Inspire rose by 51 percent to more than $24 a share.