Background. Chronic cough (CC) is highly prevalent with a significant burden on morbidity and health status. Limited data are available about structural changes underlying CC. Oscillometry by applying forced oscillation technique (FOT) measures the respiratory system?s impedance(Z) and is sensitive to small airway changes. Our study aims to detect changes in Z in subjects with CC and chronic bronchitis (CB).
Methods.We included subjects of the Austrian LEAD general population cohort without any respiratory pathology except CC and CB who underwent FOT measurements. We compared FOT parameters among i) subjects without any respiratory symptoms or pathologies, ii) subjects with only CC, iii) subjects with CC and other respiratory symptoms (wheezing and/or breathlessness), and iv) subjects with CB. CC was defined as cough >8 weeks. CB was assessed by questionnaire based on doctor?s diagnosis. Resistance (R) and reactance (X) at 5 Hz as well as the area under X (AX) and frequency dependence of R (R5-R19) were analysed.
Results.
| No respiratory symptoms nor pathologies (n=5389) | Only CC (n=175) | CC and other symptoms (n=134) | CB (n=154) | |
| R5 %pred | 83 (69;101)° | 86 (73;109) | 87 (71; 108) | 89(72;111) |
| X5 %pred | 81 (60;108)° | 82 (61;106)° | 84(59;125) | 94(65;126) |
| AX %pred | 132 (78;219)°* | 138(76;245)° | 160(77;278) | 195(106;315) |
| R5-R19 %pred | 63 (-91;222) | 84 (-64;212) | 102 (-9; 245) | 103 ( -9;280) |
* p<0.05 with CB. °p<0.05 with CC and other symptoms.
Abnormal FOT defined according to Berger et al, ERJopen 2021
Conclusion. Subjects with only CC did not present altered FOT parameters, indicative of absence of structural airway changes. Otherwise, Z data in CB are inidicative for presence of SAD.FOT seems a reliable and sensitive technique to assess airway pathology in CC and CB.