Introduction
Lung function testing for assessment of severity in wheezing preschool children is challenging. Forced oscillation technique (FOT) is quick, performed during tidal breathing and may be useful in this age group.
Aim
Assess the feasibility of pre- and post-bronchodilator (BD) FOT measurements in preschool children attending the Emergency Department (ED) with acute wheeze.
Methods
Children aged 2-4 years presenting to our Paediatric ED were recruited and FOT measurements attempted pre- and post-BD using TremoFlo C-100 (Thorasys Inc). Parameters measured included respiratory resistance (Rrs7), reactance (Xrs7) and area under the curve (AX).
Results
31 children recruited to date (mean age 3.62±1.1 years). Measurements at 5-37Hz frequency attempted in 6 children. No valid pre- and post-BD measurements were obtained. Measurements at 7-41Hz frequency attempted in the subsequent 25 children. Valid pre- and post-BD FOT measurements were obtained in 8 children (32%). Children able to perform FOT were significantly older (p<0.01, mean age 4.46 vs 3.26 years).
| Participant | ?Rrs7 | ?Xrs7 | ?AX |
| 1 | -35% | 27% | -36% |
| 2 | -24% | 40% | -19% |
| 3 | -22% | 48% | -40% |
| 4 | -5% | 29% | -20% |
| 5 | -1% | 25% | -18% |
| 6 | 4% | 32% | -1% |
| 7 | 5% | 29% | -15% |
| 8 | 21% | -36% | 19% |
Table 1: Percentage change in FOT parameters post-BD.
Discussion
Obtaining valid FOT measurements in preschoolers is possible using 7-41Hz frequency. Poor co-operation and the inability to form a seal around the mouthpiece were limiting factors. Methods of overcoming this such as the use of mouth-masks should be explored. In children able to perform FOT, results show decreased respiratory resistance and increased reactance post-BD although, considerable variation exists in published cut-off levels.