What Is New In Small Airways Research
By Ves Dimov, MD
Assistant Professor of Medicine and Pediatrics
University of Chicago
Near-roadway air pollutants decrease children's lung function
Lung function was measured on 1,811 children from 8 Southern Californian communities. Exposure to regional ozone (O3), NO2, particulate matter with aerodynamic diameter less than 10 µm (PM10) and 2.5 µm (PM2.5) was measured continuously at community monitors.
An increase in near-roadway total nitrogen oxides (NOx) of 17.9 ppb was associated with deficits of 1.6% in forced vital capacity (FVC) (p=0.005) and 1.1% in forced expiratory volume in 1 s (FEV1) (p=0.048).
Residential proximity to a freeway was associated with a reduction in FVC. Lung function deficits of 2–3% were associated with regional PM10 and PM2.5 (FVC and FEV1) and with O3 (FEV1).
Near-roadway air pollution (NRAP) and regional air pollution have independent adverse effects on childhood lung function.
Source: Urman R, McConnell R, Islam T, Avol EL, Lurmann FW, Vora H, Linn WS et al. Associations of children's lung function with ambient air pollution: joint effects of regional and near-roadway pollutants. Thorax 2013; published online before print 19 November (doi:10.1136/thoraxjnl-2012-203159)
Nebulizer delivery was not better than metered-dose inhalers with spacer in adults or children
In acute asthma, inhaled beta 2-agonists are often administered by nebulizer to relieve bronchospasm, but some have argued that metered-dose inhalers (MDI) with a holding chamber (spacer) can be equally effective. Nebulizers require a power source and need regular maintenance, and they are more expensive in the community setting.
This Cochrane review includes a total of 1,897 children and 729 adults with asthma in 39 trials (33 trials in the emergency room and 6 trials on inpatients).
The method of delivery of beta 2-agonist did not show a significant difference in hospital admission rates. In adults, the risk ratio (RR) of admission for spacer versus nebulizer was 0.94. The risk ratio for children was 0.71.
In children, length of stay in the emergency department was significantly shorter when the spacer was used. Length of stay in the emergency department for adults was similar for the two delivery methods.
Peak flow and forced expiratory volume were also similar for the two delivery methods.
Nebulizer delivery produced outcomes that were not significantly better than metered-dose inhalers (MDI) delivered by spacer in adults or children. Spacers may have some advantages compared to nebulizers for children with acute asthma.
Source: Cates CJ, Welsh EJ, Rowe BH. Holding chambers (spacers) versus nebulisers for beta-agonist treatment of acute asthma. Cochrane Database of Systematic Reviews 2013; Issue 9. Article Number: CD000052. (doi: 10.1002/14651858.CD000052.pub3)
Helpful diagnostic tool: Modified Asthma Predictive Index (mAPI) increases future asthma probability from 30% to 90%
This study aimed to confirm the predictive ability of the modified Asthma Predictive Index (mAPI). The current version of mAPI requires 4 wheezing episodes for a positive test. The authors tested a modification of the index with a 2-wheezing episode requirement (m2API).
Modified Asthma Predictive Index (mAPI) is calculated in children under the age of 3 with ALL of the following:
- 4 wheezing exacerbations in past year
- with one physician-confirmed episode
- plus one major criteria OR 2 minor criteria
Major criteria – one of the following: parental history (mother who had childhood asthma only, father with exercise-induced asthma); physician-diagnosed atopic eczema; allergic sensitization to one aeroallergen.
Minor criteria – two of the following: allergic sensitization to milk, eggs, or peanuts (positive skin or blood test sufficient); wheezing unrelated to respiratory illness (i.e., cold); blood eosinophilia 4% of total white blood cell (WBC) count.
This study included 289 children with a family history of allergy and/or asthma who were evaluated for asthma at age 6, 8, and 11 years with the use of characteristics collected during the first 3 years of life.
For the mAPI and m2API, school-age asthma prediction improved from 1 to 3 years of age. The mAPI had high predictive value after a positive test for asthma development at years 6, 8, and 11. Lowering the number of wheezing episodes to 2 (m2API) lowered the predictive value.
Post-test probabilities for a positive mAPI were 72% and 90% in unselected and high-risk populations, respectively.
In a high-risk cohort, a positive mAPI greatly increased future asthma probability (e.g., 30% pretest probability to 90% post-test probability). The mAPI helps decision making in assessing future asthma risk for preschool-age children.
Source: Chang TS, Lemanske RF Jr, Guilbert TW, Gern JE, Coen MH, Evans MD, Gangnon RE et al. Evaluation of the modified Asthma Predictive Index in high-risk preschool children. JACI: In Practice 2013;1(2). (doi: 10.1016/j.jaip.2012.10.008)