Correlation of Impulse oscillometry system indices with conventional pulmonary function tests in patients with obstructive pulmonary ventilation dysfunction

Abstract

Objective: To investigate the correlation between impulse oscillometry system examination indicators and conventional pulmonary ventilation function. Methods: The pulmonary ventilation function data of 10 883 patients from January 1, 2020 to December 31, 2022 at Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology were included. The one-second rate [ratio of forced expiratory volume in the first second (FEV1) to forced vital capacity (FVC)] measured as a percentage of the predicted value was ≥92% for the control group (n=3 478) and <92% for the pulmonary obstruction group (n=7 405). The obstruction group was subdivided into five groups according to the degree of pulmonary dysfunction: mild group (n=3 938),moderate group (n=1 142),oderate-severe group (n=917),severe group (n=737),and extremely severe group (n=671). Conventional pulmonary ventilatory function FVC, FEV1, one-second rate, and forced expired flow at 50% of FVC (MEF50%), forced expired flow at 75% FVC (MEF25%), maximal mid-expiratory flow (MMEF), peak expiratory flow (PEF), and pulsed oscillation pulmonary function test were detected in both groups of patients. Impedance at 5 Hz (Z5) means total respiratory resistance, resistance at 5 Hz (R5) means total airway resistance, reactance at 5 Hz (X5) indicates the elastic recoil of the peripheral airways, and resistance at 20 Hz (R20) represents resistance of the central airways. R5-R20 reflects resistance in the small airways. Additionally, peripheral resistance (Rp), respiratory resonance frequency (Frex), and area under the reactance curve (Ax) were also measured. Correlation between the indicators of the two groups and the sensitivity and specificity of the impulse oscillometry system parameters for the diagnosis of obstructive pulmonary ventilation dysfunction were analyzed. Results: Pulmonary function force expiratory volume in the first second as a percentage of predicted value (FEV1%Pre) [80.10 (54.95,97.10)%],one-second rate [62.43(48.67, 67.02)%],MEF50% [1.33 (0.62,1.97)L/s],MEF25% [0.28 (0.17,0.41)L/s], MMEF [0.85 (0.43,1.29)L/s],and PEF [5.64 (3.73,7.50)]L/s in the obstruction group were significantly lower than those in the control group (P<0.05). The differences within the subgroups of the obstruction group were also significant (P<0.05). Pulsed oscillation Z5 [0.42 (0.33,0.55)kPa·L-1·s-1],Rp [0.25 (0.20,0.45)kPa·L-1·s-1], R5 [0.39 (0.31,0.49)kPa·L-1·s-1], R20 [0.28 (0.24,0.34)kPa·L-1·s-1], R5-R20 [0.09 (0.05,0.17)kPa·L-1·s-1],Frex [16.32 (13.07,20.84)Hz], and Ax [0.67 (0.28,1.64)] indices in the obstruction group were significantly higher than those in the control group. X5 [-0.14 (-0.23, -0.10)kPa·L-1·s-1] was significantly lower than that in the control group (P<0.05). Z5, Rp, X5, R5, R5-R20, Frex, and Ax were statistically significant between different degrees of obstruction in the obstruction group (P<0.05). The impulse oscillometry system parameters Z5, Rp, R5, R20, R5-20, Frex, and Ax were negatively correlated with the indices of conventional pulmonary ventilation (r=-0.21-0.68, P<0.05), and the parameter X5 was positively correlated with the indices of conventional pulmonary ventilation (r=0.41-0.68, P<0.05). The pulsed oscillation pulmonary function test parameters X5 (58.60%-95.68%) and Ax (57.08%-98.06%) presented the best sensitivity; X5 (86.29%-98.82%), Frex (86.69%-94.71%), and Ax (88.10%-98.53%) displayed the best specificity; and R20 presented the worst sensitivity and specificity. The sensitivity and specificity were slightly better in female patients than in male patients. Conclusion: The technical parameters of the impulse oscillometry system showed significant correlation with relevant indices of conventional pulmonary ventilation function detection. These well reflect the changes of different degrees of pulmonary ventilation function and have greater significance for reference in evaluating the degree of pulmonary function impairment.