Small airway disease in post-acute COVID-19 syndrome, a non-conventional approach in three years follow-up of a patient with long COVID: a case report

Abstract

Background: Small airways disease (SAD), a novel finding described in post-acute COVID-19 patients, should be suspected when respiratory symptoms continue, air trapping persists on expiratory CT scans, and imaging findings fail to improve despite objectively better conventional pulmonary function test (PFT) parameters. The forced oscillation technique (FOT) and Multiple breathing washout (MBW) are both very sensitive methods for detecting anomalies in the peripheral airways.

Case presentation: We discuss the case of a 60-year-old Hispanic patient who had severe COVID-19 pneumonia and developed dyspnea, fatigue, and limited daily activity a year later. The PFTs revealed restrictive lung disease, as seen by significant diffusing capacity of the lungs for carbon monoxide (DLCO) decrease, severe desaturation, and poor 6-min walk test (6MWT) performance. The patient was treated with lowering corticosteroids as well as pulmonary rehabilitation (PR). During the 24-month follow-up, the dyspnea and fatigue persisted. On PFTs, 6MWT performance and restricted pattern improved slightly, but MBW discovered significant ventilatory inhomogeneity. FOT revealed substantial peripheral airway obstructive abnormalities. On CT scans, air trapping and ground-glass opacities (GGO) improved somewhat. The patient used a bronchodilator twice a day and low-dose inhaled corticosteroids (160 µg of budesonide and 4.5 µg of formoterol fumarate dihydrate) for nine months. PR sessions were resuming. The restricting parameters were stabilized and the DLCO had normalized after 36 months, with a 6MWT performance of 87% but significant desaturation. The CT scan revealed traction bronchiectasis, low GGO, and persistent air trapping. Without normalization, FOT and MBW scores improved, indicating small airway disease.

Conclusions: The necessity of integrating these tests when detecting SAD is emphasized in our paper. This article lays the foundation for future research into the best ways to manage and monitor SAD in post-acute COVID-19 patients.

Keywords: COVID-19; Lung Clearance Index; Multiple breathing washout; Oscillometry; Small airway disease.

Fig. 1

Initial computed tomography (CT) scan showing bilateral consolidations and ground-glass opacities involving most of the lung parenchyma

Fig. 2

12-month follow-up computed tomography scan showing mild, diffuse, bilateral ground-glass opacities associated with bronchiectasis in the upper and lower lobes of the lungs. Air trapping area in the posterior segments of the upper lobes and in the basal segments of the anterior lower lobes, evident in the expiratory phase

Fig. 3

24-month computed tomography scan follow-up with mild, diffuse, bilateral ground-glass opacities associated with septal thickening interlobular as well as traction bronchiectasis in the lower lobes with a right predominance and images dense subpleural lines, compatible with areas of pneumonitis associated with pulmonary interstitial changes, with images of bilateral air trapping

Fig. 4

36-month CT scan follow-up, GGOs of lower density than in a previous study, air trapping in the expiratory phases, thickening of bilateral interlobular septa, traction bronchiectasis