Impulse Oscillometry
A Jaeger MasterScreen IOS system (Jäeger, Wurzburg, Germany) was used to
measure the input impedance of the respiratory system. This was
performed in line with American Thoracic Society/ European Respiratory
Society guidelines.23 The IOS technique is used to
measure pulmonary resistance (R) and reactance (X). The flow signals
were evaluated for 30s in a frequency range of 5 to 20Hz for amplitude
differences to determine R and X values. The main parameters of IOS
include resistances [R5, R20 R5‐20 (resistance at 5 Hz minus
resistance at 20Hz)] and reactance [X5, X20, resonant frequency
(Fres) and reactance area (AX)].18 Higher
frequencies of R (~20Hz), reflecting the larger airways,
were regarded as representing resistance in central airways. Lower
frequencies of R (~5Hz) provided information about the
totality of airways (both small and large). Peripheral (small) airway
resistance was defined as R5-20. Acceptable variability was 15%. The
coherence thresholds were set to ≥0.6 at 5Hz and ≥0.8 at
20Hz.24,25 R5, R20, X5, and X20 were transformed into
z-scores from reference data to adjust the values for age and gender.
R5-20, Fres, and AX were used as measured crude values because of the
lack of references.26
Spirometry
The spirometry test was performed using a Jaeger MasterScreen IOS system
(Erich Jaeger, Hochberg, Germany). The precise technique employed for
this study was based on the recommendation in the American Thoracic
Society official statement on the standardization of
spirometry.27 The acceptable coefficient of variation
was <10%. Lung function parameters were expressed as
percentage values (%) predicted using Hankinson’s
formula.28 Z-scores for spirometric parameters (zFVC,
zFEV1, zFEV1/FVC, zFEF25-75) were elicited using Global Lung Initiative
equations.29
Ethics
The study was approved by our institution’s local research ethics
committee (2022/121). All participants took part voluntarily, and
written informed consent was obtained from the parents of all children
and also personally from children older than 12.
Sample Size
For statistical power analysis, due to the lack of previous studies
evaluating lung functions with IOS in children with cat sensitization
and respiratory allergic diseases; sample size was measured according to
the effect size (Cohen’s d) as 0.5. Analysis using G*Power 3.1.9.7
revealed that at an effect rate of 0.71, a margin of error of 0.05, and
a critical t value of 1.65 at an effect power of 85%, least 59 patients
would be required in each group. In the light of potential losses of
10% that might occur during the lung function measurements, we planned
to include at least 65 patients in both groups, yielding a total of 130
participants.
Statistical Analysis
SPSS version21.0 statistical software (SPSS for Windows 21.0, IBM SPSS
Inc., Chicago, IL, USA) was used for statistical analysis. Categorical
variables are presented as numbers (%) and continuous variables as
mean±SD and median values (interquartile range-IQR). Univariate analyses
involving categorical data were performed using thex2 test. Data from pulmonary function tests
exhibiting parametric variables according to the Shapiro-Wilk normality
test, were analyzed using Student’s t-test, and nonparametric variables
using the Mann-Whitney U test (comparison between the patient and
healthy groups and Groups Do+ and Do-). Kruskal-Wallis test was applied
to compare differences among groups asthma, allergic rhinitis and
coexistent of both as they were nonparametric data. Spearman’s
correlation analysis was applied to non-parametric continuous variables.
A value of p<0.05 were considered statistically significant.