The product, called NIOX, can be used in a physician's office to monitor changes in the levels of nitric oxide in a patient's breath. These levels change in response to anti-inflammatory treatment, the agency said.
An estimated 15 million Americans, one-third of them children, suffer from asthma, which causes the lungs to become inflamed and constrict, making breathing difficult. The incidence of asthma has increased in recent years.
To use the device, the patient breathes into a mouthpiece which is connected by a tube to a special computer system that can measure levels of nitric oxide and give an instant reading.
The test system is made by Aerocrine AB, of Sweden and was approved following clinical studies on 65 patients, both adults and children, with asthma.
The patients were tested before they began drug treatment and again two weeks later. The studies were conducted at nine medical centers in the United States. The results showed that most patients had a 30 percent to 70 percent decrease of nitric oxide levels after two weeks of treatment with inhaled steroids.