Impulse oscillometry may predict asthma, impaired lung function in children

Key takeaways:

• Preschool IOS results were found to have significant association with active asthma development later in childhood.
• Children who had active asthma also had increased parental asthma and allergic sensitivity.

Increased respiratory resistance in preschool children is associated with respiratory symptoms and the onset of childhood asthma, according to a study published in The Journal of Allergy and Clinical Immunology.

Findings indicate that impulse oscillometry (IOS) can serve as an objective measure for early identification of children who might be at a high risk for respiratory illness, Hanna M. Knihtila, MD, PhD, pediatrics resident at Stanford University School of Medicine and postdoctoral research fellow in the Channing Division of Network Medicine at Brigham and Women’s Hospital and Harvard Medical School, and colleagues wrote.

Study design

The study included 220 children. Researchers recruited pregnant women whose children were followed from birth to 8 years of age. All of the mothers and/or fathers of the children in the study had a history of asthma, eczema or allergic rhinitis. The mothers were given vitamin D supplements during pregnancy, and the children were followed for the primary endpoints at ages 3 and 6 years and continued until age 8 years.

The children were monitored for their health, respiratory use, and medication use by telephone every 3 months and in person annually from birth to age 8 years. IOS was performed at age 4 years (n = 220) and then spirometry at ages 5 (n = 114), 6 (n = 126), 7 (n = 132) and 8 years (n = 124). Asthma status was available from 219 children at age 8 years and data for respiratory symptoms and asthma attack medication use at age 4 years (n = 220).

Results

In total, 55 (25%) of preschool aged children reported bothersome respiratory symptoms such as wheezing, coughing or shortness of breath within the past months and 14 (6%) of children reported short-acting beta 2 agonist (SABA) use within the past 3 months.

Increased respiratory resistance in IOS at age 4 years was associated with frequent respiratory symptoms and SABA use and decreased spirometric lung function throughout the follow-up. Recent respiratory symptoms and SABA use were linked to increased respiratory resistance at 5 Hz at age 4 years (B = 2.6; 95% CI, 1-4.4 and B = 3.4; 95% CI, 0.7-6.2, respectively).

The follow-up consisted of splitting the children into tertiles based on their respiratory resistance at 5 Hz (R5) at age 4 years. A decreasing lung function was assessed with spirometry from age 5 to 8 years and with increasing respiratory resistance. Children in the highest R5 tertile at age 4 years had 23 mL (14%) lower FEV₁ at age 8 years (1.42 L vs. 1.65 L; adjusted P < .001) vs. the lowest R5 tertile.

Longitudinal IOS trajectories showed that the difference between the age 4 years R5 tertiles was the same at ages 5 and 6 years. Multivariable models adjusted for child height, sex, race, study site, trial intervention, and inhaled corticosteroid use were used to find significant association between respiratory resistance in age 4 years IOS and lung function assessed by spirometry at age 8 years. They showed decreasing lung function at age 8 years with increasing respiratory resistance at age 4 years. Respiratory resistance in IOS at ages 5 and 6 years was also significantly associated with lung function assessed by spirometry at age 8 years (B = –0.3; 95% CI, –0.5 to –0.1 for FEV₁ at 8 years).

In total, 43 (20%) of the children in the study developed asthma at age 8 years and reported at least one episode of wheezing. Forty children (93%) reported using asthma medication after age 7 years. When comparing children aged 8 years with active asthma with those without, researchers found the active asthma group had increased parental asthma (74% vs. 52%) and increased allergic sensitization (86% vs. 52%). The active asthma group also showed a significant association to respiratory resistance at age 4 years IOS compared with the non-asthma group years (B = 2; 95% CI, 0.2-3.8).

Researchers concluded that increased respiratory resistance in IOS was significantly associated with frequent respiratory symptoms and SABA use at age 4 years and that increased respiratory resistance at that age was also associated with active asthma and impaired lung function at age 8 years. These findings suggest that IOS has the potential to be used as an objective measure of early life identification for children at increased risk for respiratory illness.