Assessing post-COVID-19 respiratory dynamics: a comprehensive analysis of pulmonary function, bronchial hyperresponsiveness and bronchodilator response

Background: Coronavirus disease 2019 (COVID-19) has a considerable impact on the global healthcare system. Individuals who have recovered from COVID often experience chronic respiratory symptoms that affect their daily lives. This study aimed to assess respiratory dynamics such as airway hyperresponsiveness (AHR) and bronchodilator response in post-COVID patients. Methods: This study included 282 adults with respiratory symptoms who underwent provocation tests. The demographic details, clinical symptoms and medical histories were recorded. Baseline spirometry, methacholine challenge tests (MCT) and post-bronchodilator spirometry were performed. Patients were divided into the following four groups: Group 1: non-COVID-19 and negative MCT; Group 2: post-COVID-19 and negative MCT; Group 3: non-COVID-19 and positive MCT; and Group 4: post-COVID-19 and positive MCT. Results: Most post-COVID-19 patients (43.7%) experienced AHR, and wheezing was more common. Patients in Group 4 exhibited increased intensities of dyspnoea, cough and wheezing with the lowest pulmonary function test (PFT) parameters at baseline. Moreover, significant decreases in PFT parameters after the MCT were observed in these patients. Although the prevalence of a low forced expiratory volume in 1 s to forced vital capacity ratio (<70%) was initially 2% in Group 4, it increased to 29% after MCT. No significant differences in allergic history or underlying diseases were observed between the groups. Conclusions: These findings provide comprehensive insights into the AHR and respiratory symptoms of post-COVID-19 individuals, highlighting the characteristics and potential exacerbations in patients with positive MCT results. This emphasises the need of MCT to address respiratory dynamics in post-COVID-19 individuals.