ResMed Inc., San Diego, reported a 71 percent jump in net income for the second quarter ended December 31, 1998, to $3.9 million, or 25 cents a share, compared with $2.3 million, or 15 cents a share, for the same quarter in 1997.

Revenue for the quarter was up 33 percent to $21.5 million, compared with $16.1 million in 1997.

Respironics Inc., Pittsburgh, has reported revenue for the second quarter of fiscal 1999 ended December 31, 1998, of $90.2 million, compared with $95.5 million for the same period in fiscal 1998. Net income was $7.4 million, or 23 cents per share, compared with $9 million, or 28 cents per share, for the second quarter of fiscal 1998. (Net income and EPS results from fiscal 1998 exclude the impact of costs related to an unsolicited offer to acquire Healthdyne Technologies, which was acquired by Respironics in February 1998.)