Children with asthma who have a baseline forced expiratory volume in 1 second (FEV1) of ≤80% of predicted (LFEV1) — that is, diminished lung function — display distinct lung mechanical properties compared with patients with an FEV1 value of ≥100% of predicted (HFEV1). A controlled study was conducted in children with asthma who were recruited from the Day Program Unit and the outpatient clinic at the National Jewish Health in Denver, Colorado. Results of the analysis were published in the journal Clinical & Experimental Allergy.
The objective of the study was to characterize the lung mechanical properties of these 2 asthma phenotypes, along with the mechanisms that could explain the inconsistency in children with severe asthma, which is that when clinically stable, these patients can have an FEV1 >100% of predicted, but during an acute bronchospastic episode, the same patients can experience life-threatening asthmatic event.
The lung mechanics were assessed in 3 groups of children: children with asthma and FEV1 ≥100 (HFEV1 group; n=13), children with asthma and FEV1 ≤80% (HFEV1 group; n=14), and children without asthma (n=10; control group). The relationships between volume and static transpulmonary pressures obtained at total lung capacity (TLC); actual TLC percent predicted and flow; and static transpulmonary pressure and flow were all evaluated via the use of a linear mixed model.
Participants in the HFEV1 group had significantly larger airways (P <.05), greater lung volumes (mean percent predicted TLC, 134.8% vs 109.6%, respectively; P <.0001), and lower airway resistance measured at functional residual capacity mean percent predicted (raw 101.9% vs 199.9%, respectively; P =.005) compared with participants in the LFEV1 group.
Furthermore, participants in the HFEV1 group had significantly decreased elastic recoil pressure (with the pressure-volume curve being displaced upward and to the left) and higher lung compliance (0.21 L/cm H2O vs 0.09 L/cm H2O, respectively; P =.002) compared with those in the LFEV1 group. According to pressure-volume curves, the LFEV1 group had significantly increased resistance to flow in the upstream segment of the airways at all lung volumes compared with the HFEV1 group.
The investigators concluded that the lung mechanical properties of children with severe asthma and normal lung function are distinct from those of children with severe asthma and impaired lung function. Future analyses should include a larger number of children with severe asthma characterized by normal lung function to undergo physiologic studies at centers with expertise in performing pressure-volume studies.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Comberiati P, Spahn JD, Paull K, Faino A, Cherniack R, Covar RA. Lung mechanical properties distinguish children with asthma with normal and diminished lung function [published online January 18, 2020]. Clin Exp Allergy. doi:10.1111/cea.13573