What Is New In Small Airways Research
Ves Dimov, MD
Allergist/Immunologist at Cleveland Clinic
Clinical Associate Professor
FAU Charles E. Schmidt College of Medicine
Small airways disease is highly prevalent in asthma, even in patients with milder disease: A systematic literature review
Small airways dysfunction and inflammation contribute to the clinical impact of asthma, yet conventional methods of assessing airways function in the clinic cannot reliably evaluate its presence. This systematic literature review included 15 publications that focused on determining the prevalence of small airways disease in asthma.
Methods of assessments included:
- impulse oscillometry
- body plethysmography
- multiple-breath nitrogen washout
- high-resolution computed tomography
These studies collectively reported an overall prevalence of small airways disease of 50-60%. Small airways disease was present across all asthma severities, with evidence of distal airway disease even in the absence of proximal airway obstruction.
Small airways disease is highly prevalent in asthma, even in patients with milder disease.
Source: Usman OS, Singh D, Spinola M, Bizzi A, Barnes PJ. The prevalence of small airways disease in adult asthma: A systematic literature review. Respiratory Medicine 2016; 116:19-27. (doi:10.1016/j.rmed.2016.05.006)
Image Source: Wikipedia, Asthma, public domain.
Combination of roflumilast with montelukast improves lung function and asthma control in moderate-to-severe asthma
Roflumilast is a selective phosphodiesterase 4 inhibitor that provides modest improvements in lung function in patients with mild-to-moderate asthma. The study authors investigated if this drug might provide benefit if combined with montelukast, a leukotriene receptor antagonist, in patients whose symptoms are uncontrolled by inhaled corticosteroids and long-acting beta-agonists.
This double-blind, placebo-controlled, multiple-dose study included 64 patients who were randomized to receive 500 micrograms of roflumilast plus montelukast followed by placebo plus 10 mg of montelukast (sequence AB) or placebo plus 10 mg of montelukast followed by 500 micrograms of roflumilast plus 10 mg of montelukast (sequence BA).
FEV1 at week 4 showed a treatment difference of 100 mL for roflumilast plus montelukast. A reduction in urinary leukotriene E4 levels were also observed.
The combination of roflumilast with montelukast improved lung function and asthma control in patients with moderate-to-severe asthma and deserves further study for this indication.
Source: Bateman ED, Goehring UM, Richard F, Watz H. Roflumilast combined with montelukast versus montelukast alone as add-on treatment in patients with moderate-to-severe asthma. Journal of Allergy and Clinical Immunology 2016; 138(1): 142–149. (doi:10.1016/j.jaci.2015.11.035)
Single-breath washout (SBW) tests assess small airway disease in COPD, largely independent of spirometry
Current functional assessments do not allow a reliable assessment of small airways, a major site of disease in COPD. Single-breath washout (SBW) tests are feasible and reproducible methods for evaluating small airway disease.
This cross-sectional study included 65 patients with moderate to severe COPD. Phase III slope of N2 (SIIIN2) and double tracer gas (SIIIDTG) SBW tests were used as a measure of ventilation inhomogeneity.
Ventilation inhomogeneity was increased in COPD patients compared to healthy subjects. SIIIN2 was associated with FEV1 predicted, RV/TLC and DLCO. SIIIN2 was related to dyspnea, exercise-induced desaturation and exercise capacity. SIIIDTG was associated with TLC, DLCO and cough. These associations were largely independent of FEV1. In contrast, FEV1 was superior in predicting emphysema severity.
The study authors concluded that SIIIN2 and SIIIDTG are two fast and clinically applicable measures of small airway disease that reflect different physiological and clinical aspects of COPD, independent of spirometry.
Source: Boeck L, Gensmer A, Nyilas S, Stieltjes B, Re TJ. Single-breath washout tests to assess small airway disease in COPD. Chest 2016; published online ahead of print, May 30. (doi:10.1016/j.chest.2016.05.019)