Small airway disease (SAD) in asthma in pregnancy evaluated by impulse oscillometry: A cross-sectional study.

Background and objective: Asthma is a common respiratory disease in pregnancy, with approximately 18% of cases worsening. Small airway disease (SAD) with a reported prevalence of up to 70% is now recognised as a principal indicator of poor asthma control. Impulse oscillometry (IOS) is a non-invasive, technically easier, and patient-friendly tool for detecting SAD. We aimed to assess the prevalence of SAD in pregnant women with asthma and the acceptance of the IOS across different trimesters of pregnancy.

Methods: This cross-sectional study was conducted among pregnant women aged ≥18 years with clinically diagnosed asthma. All patients underwent IOS following manufacturer and European Respiratory Society guidelines. A questionnaire was used to assess their satisfaction with the technique.

Results: Out of 78 patients who underwent IOS, SAD was present in 55.1% (95% CI = 43.4 to 66.4%). Post-bronchodilator reversibility was observed in 37.2% of patients. Abnormal total (R5) and larger (R20) airway resistance were found in 79.5% and 64.1% of patients, respectively. Other IOS parameters (Fres, AX, and X5) were abnormal in 58.9%, 30.7%, and 39.7% of patients, respectively. Bivariate and multivariate logistic regression analyses indicated longer duration of asthma (OR = 1.1; 95% CI = 1.05-1.18; P < 0.001) and passive smoking (OR = 4.2; 95% CI = 1.58-11.1; P = 0.004) were significantly associated with SAD. All participants tolerated the IOS well, with a satisfaction score of 4.75 ± 0.72.

Conclusion: The IOS is a helpful tool for the evaluation of SAD, a significant comorbidity in pregnant women with asthma. Factors such as longer disease duration and exposure to passive smoking, akin to risk factors for chronic airflow obstruction, are significantly associated with SAD. Future research should explore SAD's impact on clinical management and overall asthma outcomes.