Small Airway Dysfunction by Impulse Oscillometry in Symptomatic Patients with Preserved Pulmonary Function

Hwa-Yen Chiu; Yi-Han Hsiao; Kang-Cheng Su; Yu-Chin Lee; Hsin-Kuo Ko; Diahn-Warng Perng

doi:10.1016/j.jaip.2019.06.035

Small Airway Dysfunction by Impulse Oscillometry in Symptomatic Patients with Preserved Pulmonary Function

J Allergy Clin Immunol Pract. 2020 Jan;8(1):229-235.e3. doi: 10.1016/j.jaip.2019.06.035. Epub 2019 Jul 10.

Authors

Hwa-Yen Chiu¹, Yi-Han Hsiao², Kang-Cheng Su², Yu-Chin Lee³, Hsin-Kuo Ko⁴, Diahn-Warng Perng⁵

Affiliations

¹ Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
² Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
³ Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Sijhih Cathay General Hospital, New Taipei City, Taiwan.
⁴ Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: hkkao@vghtpe.gov.tw.
⁵ Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: dwperng@vghtpe.gov.tw.

PMID: 31299351
DOI: 10.1016/j.jaip.2019.06.035

Abstract

Background: Asthma and chronic obstructive pulmonary disease are characterized by persistent airway inflammation and airflow limitation. Early detection of these diseases in patients with respiratory symptoms and preserved pulmonary function (PPF) defined by spirometry is difficult. Impulse oscillometry (IOS) may have better sensitivity than effort-dependent forced expiratory flow between 25% and 75% (FEF_25%-75%) to detect small airway dysfunction (SAD).

Objective: To identify SAD in patients with respiratory symptoms and PPF using IOS.

Methods: Medical records of symptomatic patients without acute or known structural lung diseases were evaluated. Patients had bronchodilator testing and IOS in the outpatient clinic between March 1 and July 31, 2017. Correlations between respiratory symptoms, spirometry, and IOS parameters were determined.

Results: Among 349 patients enrolled to the study, 255 (73.1%) patients met the criteria of PPF. The IOS parameters-difference in resistance at 5 Hz and resistance at 20 Hz , reactance at 5 Hz, resonant frequency (F_res), and area under reactance curve between 5 Hz and resonant frequency-were significantly correlated with FEF_25%-75%. The cutoffs for SAD were difference in resistance at 5 Hz and resistance at 20 Hz greater than 0.07 kPa/(L/s), reactance at 5 Hz less than -0.12 kPa/(L/s), F_res greater than 14.14 Hz, and area under reactance curve between 5 Hz and resonant frequency greater than 0.44 kPa/L. Of the IOS parameters, F_res and reactance at 5 Hz had the highest sensitivity and specificity. When compared with FEF_25%-75%, F_res had greater sensitivity to detect SAD in patients with PPF. Patients with IOS-defined SAD had a significantly higher incidence of wheeze or sputum production than did those defined by FEF_25%-75%.

Conclusions: Patients with respiratory symptoms and PPF may have SAD, which can be identified with the aid of IOS in addition to spirometry.

Keywords: Forced expiratory flow; Impulse oscillometry; Preserved pulmonary function; Small airway dysfunction; Spirometry.

MeSH terms

Forced Expiratory Volume
Humans
Lung*
Oscillometry
Pulmonary Disease, Chronic Obstructive* / diagnosis
Respiratory Function Tests
Spirometry