Effects of Forceful Breathing Maneuvers of Spirometry on Respiratory Impedance Measured by Oscillometry

Deep inspiratory maneuvers can modify airway diameter, leading to shortterm fluctuations in respiratory impedance (Zrs). However, the impact of the forceful breathing maneuvers used in spirometry on Zrs has not been systematically investigated. This study was designed to assess and compare the effects of spirometry maneuvers on Zrs, as measured by oscillometry, in adult patients with obstructive airway diseases (group I) versus those presenting with respiratory symptoms but without airflow obstruction on spirometry (group II).

All participants underwent oscillometry assessments both before and immediately following spirometry. Paired t-tests and unpaired t-tests were conducted to compare differences within and between groups, respectively. Bland-Altman plots were utilized to display the percentage change in Zrs parameters against the mean, along with the limits of agreement (LoA).

In this cross-sectional study, 166 patients were enrolled (53% male), with a mean age of 40.4 years. Group I accounted for 62% of cases, while group II composed 38%. Patients in group I demonstrated greater impairment in both spirometry and Zrs parameters. Nearly all patients experienced changes in Zrs after spirometry compared to pre-spirometry values, regardless of group assignment. Except for R5 in group I, statistically significant paired differences in Zrs parameters were not observed between pre- and post-spirometry in either group. The cohort demonstrated mean biases between pre- and post-spirometry as follows: R5 4.6% (LoA: -44.8%, 54%); X5 5.8% (LoA: -69.5%, 81.2%); AX 4.3% (LoA: -93.9%,102.6%); and Fres 0.5% (LoA: -30.8%, 31.8%). The broad and random LoA reflect marked inter-individual variability.

Spirometry maneuvers cause fluctuations in Zrs parameters, especially in R5. Oscillometry performed after spirometry may cause clinically meaningful changes in Zrs parameters.