IMPULSE OSCILLATION SYSTEM IN PREOPERATIVE PULMONARY FUNCTION TEST: EVALUATION BY REGRESSION ANALYSIS

Abstract

Preoperative lung function tests are useful to evaluate the preoperative pulmonary condition and to detect a high risk of postoperative pulmonary complications. But, maximum expiratory effort by patients is necessary to determine lung function. On the other hand, it is believed that respiratory system impedance using an impulse oscillatory system (IOS) can quickly evaluate total airway resistance (R₅), large airway resistance (R₂₀), small airway resistance (R₅-R₂₀) and capacitive reactance (X₅) under breathing at rest. In this study we used regression analysis to evaluate the relationship between parameters in IOS and non-IOS. Six hundred-twenty patients (20 to 89 year of age) scheduled for elective surgery were studied. IOS and non-IOS, such as spirometry, maximum expiratory flow-volume curve and single N₂ washout curve were preoperatively measured to investigate the relationship between parameters in IOS and non-IOS. We examined the relationship between IOS and non-IOS by calculating Pearson's product-moment correlation coefficient. Regression equations obtained between IOS and non-IOS parameters were statistically significant (p<0.05). In the linear regression equation, the highest correlation coefficient (R²) was 0.267 between X₅ and FEV_1.0. Similarly, in the regression equation curve, the highest R² value was 0.293 between X₅ and FEV_1.0. In the linear regression equation in the set of 45 a significant difference was observed, the combination R² value did not reach 0.1 was 22 pairs and it was equivalent to about half of. In the evaluation using the regression equation curve between each parameter of the IOS and the conventional inspection methods a high linear regression analysis correlation was observed. However, the correlation was not high enough to substitute the test with IOS.