Bronchodilator response by interrupter technique to guide management of preschool wheeze.

OBJECTIVE: We examined relationships between clinical features and pulmonary function before and after inhaled corticosteroid (ICS) treatment in wheezy preschool children, and specifically, whether measuring bronchodilator response (BDR) could predict benefit from ICS. DESIGN: Clinical non-randomised intervention study SETTING: Secondary care. PATIENTS: Preschool children (2 years to <6 years) with recurrent wheeze. INTERVENTIONS: Inhaled beta-agonist, ICS. OUTCOME MEASURES: We measured prebronchodilator and postbronchodilator interrupter resistance (Rint) and symptom scores at 0 (V1), 4 (V2) and 12 (V3) weeks. At V2, those with a predetermined symptom level commenced ICS. Modified Asthma Predictive Index (mAPI) and parental perception of response to bronchodilator were recorded. Response to ICS was defined as a reduction in daily symptom score of >0.26. Positive BDR was defined as fall in Rint of ≥0.26 kPa.s/L, ≥35% predicted or ≥1.25 Z Scores. RESULTS: Out of 138 recruited children, 67 completed the full study. Mean (SD) prebronchodilator Rint at V2 was 1.22 (0.35) kPa.s/L, and fell after starting ICS (V3) to 1.09 (0.33) kPa.s/L (p<0.001), while mean (SD) daily symptom score fell from 0.56 (0.36) to 0.28 (0.36) after ICS (p<0.001). Positive Rint BDR before ICS (at V1 and/or V2), using all three threshold criteria, was significantly associated with response to ICS on symptom scores at V3 (p<0.05). mAPI was not significantly associated with response to ICS, and parents' perception of response to bronchodilator was not related to measured Rint BDR . CONCLUSIONS: Rint BDR may be helpful in selecting which wheezy preschool children are likely to benefit from ICS.

The effect of pre-industrial and predicted atmospheric CO2 concentrations on the development of diazotrophic and non-diazotrophic cyanobacterium: Dolichospermum circinale and Microcystis aeruginosa.

Photoautotrophs are capable of consuming high quantities of CO2, yet scant research exists examining the influence of different CO2 concentrations on the growth of freshwater diazotrophic or non-diazotrophic cyanobacteria. In this study, we cultured two cyanobacteria taxa (Dolichospermum circinale and Microcystis aeruginosa) within controlled atmospheric CO2 chambers at pre-industrial, and post-industrial concentrations. Biovolume and chlorophyll a (Chl-a) differed as a consequence of the adjusted CO2 gradients. Significantly higher biovolume measurements were observed in the elevated CO2 treatment for the diazotrophic species in the initial experiment. However, a follow-up experiment, with a corrected culture replenishment regime showed Chl-a measurements were greater for the diazotrophic and non-diazotrophic species in the elevated CO2 treatment. Increasing CO2 presents a risk to already compromised eutrophic and hyper-eutrophic ecosystems, and we reason increasing CO2 concentrations could affect photosynthetic performance and CO2 assimilation of surface dwelling cyanobacteria. Further experimental work is required to establish ecological thresholds for freshwater ecosystems, as pH levels showed a measurable reduction within the elevated CO2 treatments. As cyanobacteria species may respond quite differently to future CO2 concentrations similar comparative studies should be carried out that focus on CO2 dynamics and pH. The findings of the study indicate diazotrophic cyanobacteria growth in particular may benefit from elevated atmospheric CO2 concentrations.