Oscillometry useful in measuring lung function among children with asthma in the ED
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Key takeaways:
- Subjective assessments in the ED are not always related to airway function or course of treatment.
- Airwave oscillometry is considered noninvasive, fast and feasible for children with acute asthma exacerbations.
WASHINGTON — Oscillometry was a successful objective measure of lung function among children presenting to the ED with acute asthma, according to data presented at the American Thoracic Society International Conference.
Also, worse lung function at presentation may correspond with a need to escalate care, Kate Hamlington-Smith, PhD, assistant professor, pediatric pulmonary and sleep medicine, University of Colorado School of Medicine Anschutz Medical Campus, and colleagues wrote.
Current treatment needs
“We need better methods to predict a child’s response to asthma treatments in the ED during acute exacerbation,” Hamlington-Smith said during her presentation. “This is important because asthma exacerbations are a leading cause of emergent health care visits.”
Hamlington-Smith also noted a lack of improvement in clinical management of exacerbations in the ED as well as a need to decrease the time to escalation of care or discharge home.
“Our ED treatment decisions are typically based on subjective clinical severity scores, which aren’t really always related to airway function or ED course,” she said.
Providers at Children’s Hospital Colorado do not perform spirometry or measure peak flow, which are objective lung function measurements, during exacerbations because they are not considered safe, Hamlington-Smith said.
With previous studies indicating that airwave oscillometry (AOS) was noninvasive, fast and feasible among children with acute asthma, the researchers decided to investigate the relationship between oscillometry metrics of lung function and ED course and disposition, Hamlington-Smith said.
Study design, results
The prospective, observational cohort study involved 77 children (mean age, 9.6 years ± 3.8; age range, 4.2-18.4 years; 62% male; 59% Hispanic) who presented to the ED with asthma exacerbations.
Providers measured respiratory system impedance via AOS and Pediatric Asthma Score (PAS) before (T1) and after (T2) standard initial therapies, which included nebulized albuterol/ipratropium bromide and corticosteroids. T2 was an average of 52 minutes ± 20 minutes after T1.
The PAS comprises respiratory rate, oxygen saturation on room air, auscultation, retractions and dyspnea, with each subjectively graded on a 3-point severity scale and then added together for overall scores of mild (5-7), moderate (8-11) or severe (12-15).
The median PAS score for the cohort at presentation was 6 (range, 5-8), with 54% patients considered mild, 43% who were moderate and 3% who were severe. Outcomes included 56% who were discharged home, 21% who had additional treatments and about 23% who were hospitalized.
Additional treatments included continuous albuterol, intravenous magnesium or terbutaline, or intravenous, intramuscular or subcutaneous epinephrine.
“Twice as many that were mild were discharged home without any additional therapies, about half-and-half of mild-moderate received additional therapies, and the remainder, the majority of those that were hospitalized, were initially a moderate PAS score,” Hamlington-Smith said.
In other words, Hamlington-Smith continued, initial PAS severity score was not always aligned with treatment response and clinical outcome, as some patients who were considered mild ultimately were admitted to the hospital. However, she said, AOS was successful among these patients.
At T1, 68 of 77 patients (88%) attempted AOS, including 33 of 42 (79%) who were considered mild. Success included 57 of these 77 patients (74%) including 23 of 33 (70%) of those who were considered moderate. Plus, 52 of 77 (68%) completed AOS at both T1 and T2, including one of the two severe patients.
There was a weak correlation between increased PAS scores at T1 and increased frequency dependence of resistance at T1 (r = 0.34; P = .018), but there was no correlation between PAS scores at T1 and total airway resistance (R7) or reactance area (AX) at T1.
Similarly, there were no correlations between the difference in PAS at T1 and T2 and the differences in R7, R7-19 or AX at T1 and T2.
The researchers also found that 19 of 49 patients (39%) including nine who were mild and 10 who were moderate or severe had R7 totals that were higher than the upper limit of normal (ULN) at T1 before falling to greater than 11% of ULN.
Further, 28 of 47 patients (60%) including 15 who were mild and 13 who were moderate or severe had AX scores that were higher than the ULN at T1 and then fell to greater than 19% of the ULN at T2.
Five of the mild patients and 12 of the moderate or severe patients (17/49; 35%) needed additional therapies, and three of the mild and eight of the moderate (11/49; 22%) required hospitalization.
Based on these findings, the researchers said that there was an association between PAS scores and outcomes, as expected due to the assessment’s clinical use.
Odds for subsequent treatment were greater than 15% with each single-unit increase in totals for R7, R7-19 and AX at T1. Odds for not getting subsequent treatments were greater than 15% with each 1 cm H2O/L/second decrease in R7 and R7-19 from T1 and T2 and with each 10 cm H2O/L decrease in AX from T1 and T2.
The researchers said that results were similar for associations between hospitalization and R7 and R7-19 but they were not statistically significant.
Conclusions
“Overall, oscillometry is a successful objective measure of lung function in children with acute asthma in the ED,” said Hamlington-Smith.
After initial treatments, she continued, the decreases in respiratory impedance varied, indicating that degrees of treatment responsiveness, improvements in lung function and the worst lung function at presentation may correspond with a need to escalate care.
“We think that oscillometry can be useful to inform ED clinical decision-making and expedite the time to disposition,” Hamlington-Smith said.