Impulse Oscillometry Offers Hope of Early Diagnosis of Asthma
A study led by researchers at NIAID suggests that impulse oscillometry (IOS), a non-invasive method for measuring lung function, is more effective in detecting asthma in children than spirometry, the commonly used method. The results appear in the August 2011 issue of Pediatric Pulmonology.
Background
A child uses an IOS machine to measure lung function. Credit: NIAID
Jason1 was only 3 years old when he first arrived at the Pediatric Allergy Clinic at the National Institutes of Health (NIH), in Bethesda, Maryland. He had a history of severe allergic reactions to food and suffered from chronic atopic dermatitis, also called eczema. Recently, he had developed recurrent coughing and wheezing. His doctor suspected asthma and prescribed daily use of inhaled corticosteroids.
Before adding another drug to Jason’s daily regimen, his parents wanted conclusive proof that he had asthma. The standard test used to diagnose asthma, called spirometry, requires that a person exhale vigorously into a machine for 10 to 15 seconds. As a result, younger children and some adults with physical impairment may not be able to use the test. Because of Jason’s age, he would have to wait two to three years before he could take a lung function test to confirm his doctor’s diagnosis.
“A challenge for clinicians is how to make an accurate diagnosis in cases when the patient is not capable of performing the test required for that diagnosis,” said Hirsh D. Komarow, M.D., of the NIAID Laboratory of Allergic Diseases.
New Technology
IOS is a newer method of measuring lung function that has gradually been gaining acceptance by clinicians. The IOS machine works by producing small-pressure oscillations (vibrations) that are applied at the mouth and transmitted into the lungs. Measuring how the respiratory system responds to these impulses during natural breathing provides an indirect analysis of lung function. Unlike spirometry, IOS is non-invasive and easy-to-perform and requires minimal assistance from the patient.
“IOS offers several advantages over spirometry in the evaluation of young children in clinical practice,” said Dr. Komarow, “We sought to answer the question: Are the test results obtained from IOS as accurate as those produced by spirometry.”
Study Results and Significance
Dr. Komarow’s study compared results from lung function tests measured by IOS and by spirometry in 117 children who already were receiving medical care at the NIH Pediatric Allergy Clinic.
“The data were conclusive,” said Dean Metcalfe, M.D., chief of the Laboratory of Allergic Diseases, “In these children, IOS was not only more sensitive than spirometry, it was more specific in identifying children with asthma.”
This is a promising advance in asthma care. Asthma is a chronic lung disease that affects more than 22 million people in the United States, including nearly 7 million children under age 6. Early diagnosis of asthma promises several benefits: parents are able to more closely monitor their child for respiratory symptoms that may worsen asthma; doctors can track the course of the disease over a longer time period to better predict its outcome; and there are studies that indicate that beginning asthma treatment at a younger age improves long-term control of the illness.
Dr. Komarow examined Jason using IOS and in moments confirmed that Jason had asthma.
“I was pleased that Jason could be evaluated with IOS at the clinic,” said Dr. Komarow, “We made an objective diagnosis and he is receiving appropriate treatment to manage his asthma. This would not have been possible without IOS.”
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