Shares in Irvine-based Masimo Corp. fell 4% in midday trading today after the medical-device maker posted mixed first-quarter financial results.

Masimo reported a 12% drop in first-quarter profit from a year earlier to $15.8 million, below the consensus analyst estimate of $16.6 million. Masimo said the decline reflected lower royalty payments by competitor Covidien PLC following a patent-lawsuit settlement.

Masimo’s quarterly revenue rose 6% to $119.2 million. Analysts on average were expecting Masimo to have $118.5 million in first-quarter revenue.

The company, which makes patient monitors and other devices, didn’t give a forecast for the current quarter.

Analysts are looking for Masimo to post a profit of $16.6 million on revenue of $120.4 million.