Sleep disorder equipment supplier ResMed is disappointed with the financial performance of its business in the United States, despite a profit rise.

The company began in 1989, selling a device developed at the University of Sydney to treat sleep apnea.

It now develops and sells a range of devices around the world to treat sleep and respiratory disorders.

ResMed’s net income in the three months to December 31 of $US86.6 million was up 11 per cent from the same period a year earlier.

Net income in the first half of the 2013/14 financial year grew by 12 per cent to $US167.56 million.

However, quarterly revenue in the Americas fell two per cent compared to the prior corresponding period, to $US206.6 million.

“In the Americas, clearly we had some external headwinds, and we were not satisfied with the results,” ResMed chief executive Mick Farrell said.

Sales in the key US market were affected by restructuring due to competitive bidding, and increased competitor activity on pricing and the release of new products.

Sales revenues from masks were flat, and air flow generator sales revenue fell by five per cent.

Mr Farrell said ResMed was also up against some very tough prior year comparisons – flow generators were up 16 per cent in the same period in 2012, and masks were also up 16 per cent 12 months ago.

It would be a number of months before the US market stabilises, he said but the number of new sleep disorder patients continued to grow in the US and many of ResMed’s US customers were picking them up.

ResMed will also release three new masks in 2014, including one launched last week.

Mr Farrell said ResMed would continue to evaluate its pricing of products in the Americas to reflect market conditions and ResMed’s belief that its products offered patients better value.

Shares in ResMed were down 26.5 cents, or five per cent, at $4.995 at 1300 AEDT.