Proxy voting advisor Institutional Shareholder Services (ISS) has said electing Politan Capital Management candidates Michelle Brennan and Quentin Koffey could help to repair Masimo’s relationship with its shareholders.

Masimo ‘‘is a public company that operates like a private business, and is disregarding shareholders in the process,’’ said ISS in a note backing the activist’s campaign, according to Politan.

Though Masimo recently signaled openness to adding Brennan, a former Johnson & Johnson executive, to its board, it said electing Politan Managing Partner Koffey would be a mistake. The company accused Koffey of planning to ‘‘meddle’’ in its R&D strategy, which the medical device maker says would endanger its future.

However, ISS insisted that Masimo’s board ‘‘needs to repair its relationship with shareholders, and needs to credibly establish an ability to effectively oversee management,’’ saying electing Koffey, as the representative of a 9% shareholder, would help the company in those key areas.

Another of the company’s arguments against Koffey’s appointment to the board is that he intends to push out CEO Joe Kiani and take control of the business, Masimo said in a letter this week. ISS criticized Masimo for ‘‘framing a fight for a minority position as a referendum on the CEO’’ and said Kiani may have too much influence over the board. Kiani is the company’s founder and chairman.

Two seats are up for grabs at Masimo’s June 26 annual meeting. The company is seeking to expand the size of its board from five to seven members. ‘’Two seats on a seven-member board would still provide the dissident with an adequate presence, as long as the two future additions are truly independent,” said ISS in its note.