Allergy and Airway |

Is There Still Any Role for Impulse Oscillometric Lung Function in Clinical Practice in Detecting Small Airways Abnormalities in Asthma? FREE TO VIEW

Rudina Ndreu; Ivana Pavlickova; Edo Fornai; Simonetta Monti, MD; Renato Prediletto, MD
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Institute of Clinical Physiology, National Research Council and Gabriele Monasterio Foundation, CNR and Tuscany Region, Pisa, Italy

Chest. 2014;146(4_MeetingAbstracts):3A. doi:10.1378/chest.1991486
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SESSION TITLE: Asthma Posters I

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 29, 2014 at 01:30 PM - 02:30 PM

PURPOSE: That in asthma there is a certain involvement of small airways is out of doubt. One question arises if the technique of impulse oscillometriy (IOS) is able to reveal with enough sensitivity the inflammatory abnormalities in small airways, as detected from the increase of flow resistances, in asthma. To do this consecutive asthmatic patients were enrolled during a stable phase of their disease.

METHODS: IOS were measured according the standard technique on the basis of tidal breathing by means of small impulses-shaped signals continuously superimposed on the patient's breathing flow utilizing the Jager Impulse Oscillating System (Care Fusion Product). After a minimum of 4 regular breaths the data recordings were collected at functional residual capacity, in a seated position. Parameters included resistances at oscillation-frequencies of 5 Hz (R5) and 20 Hz (R20), frequency dependence of resistance calculated as the difference between resistance at 5 and 20 Hz (R5-20) and reactance at 5 Hz (X5). R5 and R20 were assumed to reflect respiratory resistance at 5 and 20 Hz, respectively, R5-R20 reflecting the non uniform distribution of airflow in the distal airways and X5 reflecting the dynamic elastance. Spirometry was also executed. Seventyfour patients with asthma (21 males and 53 female, age range 19-73 years) performed the test. Moreover, a group control consisting of 13 healthy subjects was considered. Sensitivity and specificity, as well as positive and negative predictive values (PPV and NPV) and accuracy were calculated according to treshold values of R5-R20 ≥ to 0.07 Kpa/lL/s and X5 > -0.12 Kpa/L/s

RESULTS: Mostly of patients exhibited spirometry above normal range (FEV1/FVC > 70%). Out of 74 pts with asthma 48 resulted positive for the test whereas 26 patients had values of R5-R20 below the treshold limit. It turned out that sensitivity was 65 % whereas specificity resulted 100%. PPV resulted 100% whereas NPV resulted 33%, and, finally, the real prevalence of the test was 55%. Accuracy was 70%. As to X5, 65% of patients had values below the threshold, which is specular to R5-R20 values.

CONCLUSIONS: Our preliminary results seem to suggest that values of R5-R20 < to 0.07 and of X5 > -0.12 Kpa/L/s may allow to exclude with extreme accuracy the presence of increased flow resistances at the level of small airways and thus the existence of inflammation.

CLINICAL IMPLICATIONS: These observations suggest caution to interpret this test in the clinical work-up, when employed as unique tool to evaluate the disease.

DISCLOSURE: The following authors have nothing to disclose: Rudina Ndreu, Ivana Pavlickova, Edo Fornai, Simonetta Monti, Renato Prediletto

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