Characteristics of inspiratory and expiratory reactance in interstitial lung disease.

BACKGROUND: Forced oscillometry is a non-invasive method to measure respiratory resistance and reactance. In this study, we investigated the characteristics of measurements obtained with an impulse oscillation system (IOS) for patients with interstitial lung disease (ILD). METHOD: IOS and spirometry were performed in 64 ILD patients, 54 asthma patients, 49 chronic obstructive pulmonary disease (COPD) patients, and 29 controls. Respiratory resistance and reactance were assessed as measurements averaged over several tidal breaths (whole-breath analysis) and as measurements separately averaged during inspiration and expiration (inspiratory-expiratory analysis). RESULTS: Whole-breath IOS analyses for ILD patients showed increased resistance at 5 Hz and decreased reactance at 5 Hz (X5) compared with controls, although these features were also found in asthma and COPD patients. Inspiratory-expiratory analysis demonstrated that the changes in X5 and reactance area (AX) between inspiration and expiration (ΔX5 and ΔAX, respectively) were significantly different from those in asthma patients, COPD patients, and controls. However, multiple linear regression analysis showed that the presence of ILD was independently associated with ΔX5, but not with ΔAX. Furthermore, ΔX5 was inversely correlated with vital capacity and diffusing capacity of carbon monoxide in ILD patients. CONCLUSIONS: Our results suggest that ΔX5 is a characteristic feature of IOS measurements in ILD patients, which is clearly different from those in asthma and COPD patients. This within-breath X5 change in ILD might be associated with its severity and physiological abnormality, although further studies are needed to investigate its cause.

IL-12p40 is essential for the down-regulation of airway hyperresponsiveness in a mouse model of bronchial asthma with prolonged antigen exposure.

BACKGROUND: We previously reported a mouse model of bronchial asthma showing eosinophilic inflammation, but not airway hyperresponsiveness (AHR), after prolonged antigen exposure. This model showed an increase of IL-12 in the lung. OBJECTIVE: The aim of this study was to investigate the role of IL-12p40 in a murine asthma model with prolonged antigen exposures. METHODS: An ovalbumin (OVA)-induced asthma model was first established in wild-type (WT) and IL-12p40-deficient (IL-12p40(-/-)) mice. Both strains of mice were further exposed to either OVA (prolonged exposure group) or phosphate-buffered saline (positive control group) 3 days per week for 3 weeks. During week 4, both groups of mice were given a final challenge with OVA. RESULTS: Prolonged antigen exposures resulted in marked suppression of airway eosinophilia in both WT and IL-12p40(-/-) mice. However, AHR persisted in IL-12p40(-/-) but not in WT mice. There were no significant differences of IL-5, IL-13 or IFN-gamma levels in bronchoalveolar lavage fluid between WT and IL-12p40(-/-) mice. The hydroxyproline content of the lung and peribronchial fibrosis were, however, significantly increased in IL-12p40(-/-) mice. CONCLUSION: The results suggest that endogenous IL-12p40 is essential for inhibition of AHR and peribronchial fibrosis, but not eosinophilic inflammation, in a murine asthma model with prolonged antigen exposures.