Repeatability of Respiratory Impedance and Bronchodilatory Response in Asthmatic Children
Date
2016-03-23T16:17:06Z
Authors
Alamer, Marwa
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Abstract
Asthma is a chronic illness that affects approximately 10% of children in the developed world. Objective assessment is recommended using spirometry to obtain the forced expired volume in 1 second (FEV1), usually combined with inhaled bronchodilator to assess airway reversibility. However this measurement is often not done, possibly due to the difficulty involved in the test. A potentially easier to perform measurement is oscillometry which obtains the respiratory system resistance, Rrs and reactance, Xrs but little evaluation has been done to compare this to spirometry. This thesis compares the sensitivity and repeatability of oscillometry to spirometry during reversibility and develops a ‘signal to noise’ measure assessed in children with asthma.
Description
We measured 53 school aged children using standard spirometry and oscillometry using the tremoFlo system, with 3 repeated measures both before and after an inhaled bronchodilator. We calculated the sensitivity to BD as the %change in FEV1, Rrs and Xrs, and we calculated the variability of these measures using their coefficient of variation. We developed the signal to noise ratio as the sensitivity normalized to the COV as the SNR_BD_FEV1, SNR_BD_Rrs and the SNR_BD_Xrs. We found that, in response to BD, FEV1 increased by 7.1(6.2)%, while Rrs decreased by 25.3(10.5)% and Xrs became less negative by 26.9 (20.5)%. However both Rrs and Xrs were more variable, with their COVs about 2.5-fold and 6-fold respectively greater than the COV of FEV1. Importantly when we compared the SNR_BD between impedance measurements (FOT) and FEV1, we found that while the SNR_BD for Xrs5 and FEV1 were not significantly different, the SNR_BD for Rrs5 was nearly 2 times greater than SNR_BD for FEV1 (p < 0.0005). This means Rrs at 5 Hz may be a more useful measure of the response to a bronchodilator in children with mild asthma. In conclusion, since oscillometry had better signal-to-noise, and is easier for patients to perform, and because it directly measures the difficulty of moving air in the respiratory system, we recommend oscillometry to assess reversibility in children with asthma.
Keywords
Repeatability, Respiratory Impedance, Bronchodilatory Response, Asthma, oscillometry, spirometry