3.Results
3.1Study searches and characteristics of the included studies
The detailed process of the literature search is shown in Fig. 1. A
total of 6 eligible studies[15-20], published
between 2016 and 2020, were enrolled in the present meta-analysis.
The
studies were conducted in the following geographical
regions:USA(n=2),Germany(n=1), Turkey(n=1), China(n=2). All studies used
well-controlled asthma as the control group, and 4 studies also added
healthy people as the control group[15, 17, 18,
20]. Our study focused on the role of IOS in predicting asthma
exacerbations or loss of control, so we did not include healthy people.
The sample size ranged from 54 to 192, including 615 children with an
average age of 3.65-11.20 years. They were all case-control studies. All
participants performed IOS. Meaningful pulse oscillation parameters
varied among the trials. The quality scores of these studies were
evaluated by the NOS ranging from 7 to 8. The characteristics of all
studies were summarized in Table1.
3.2Association between pulse oscillation parameters and asthma
exacerbations
The included six studies revealed that IOS may be able to identify the
risk of acute attack or loss of control of asthma. We further analyzed
the value of IOS common parameters in predicting the loss of asthma
control. In terms of resistance, we found that elevated levels of R5 may
indicate the risk of asthma exacerbations (WMD = − 1.21, 95%CI: −1.55
to −0.87, P<0.001)(Fig.2a).However, as for R20(WMD = − 0.81, 95%CI:
−1.95 to 0.32, P=0.161), R5-20 (WMD = − 0.68, 95%CI: −1.61 to 0.25,
P=0.151), the results did not show a good correlation with the acute
attack of asthma (Fig.2b-2c). In terms of reactance, we found X5 (WMD
=0.81, 95%CI: 0.56 to 1.01, P<0.001) were significantly related to the
loss of asthma control(Fig.2d). Moreover, the Fres (WMD = − 1.34,
95%CI: −2.03 to −0.65,P=0.018) and AX (WMD = − 7.35, 95%CI: −9.94 to
−4.76,P<0.001) can also identify the risk of acute attack or loss of
control of asthma(Fig.2e-2f).
3.3 Sensitivity analysis and publication bias
Sensitivity analysis confirmed that no individual study influenced the
overall results. There was no evidence of publication bias in this
meta-analysis indicated by Begg’s funnel plot and Egger’s tests (Fig3).