Influenza A virus H1N1 associated pneumonia - acute and late aspects evaluated with tomography high resolution in hospitalized patients

Abstract

Background: Influenza A (H1N1) virus often compromises the respiratory tract, leading to pneumonia, which is the principal cause of death in these patients. The purpose of this study was to review the acute and late phase pulmonary findings in influenza A(H1N1) associated pneumonia using high resolution computed tomography (HRCT), and to determine the importance of performing end expiration series. Methods: Between July and August 2009, 140 patients presented with influenza A (H1N1) confirmed by real-timepolymerase chain reaction. Out of these, 27 patients underwent HRCT in the acute and late phases of pneumonia, allowing for a comparative study. Late phase exams were performed due to clinical worsening and up to 120 days later in patients with persistent complaints of dyspnea.Results: Ground glass opacities, consolidations, and the combination of both were associated with the acute phase, whereas persistence or worsening of the lesions, lesion improvement, and air trapping in the end expiration series (as seen using HRCT, n=6) were observed in the late phase.Conclusions: In the HRCT end expiration series, air trapping was found in the late phase of H1N1 associated pneumonia. Generally, these exams are not evaluated in research articles, and air trapping has not previously been studied using the end expiration series. Our study brings more scientific knowledge about aspects of pulmonary involvement by influenza A (H1N1), through evaluation with end expiration series, which makes the CT exam dynamic, translating the respiratory movement, and showing bronchial alteration.

Differences in clinical characteristics and chest CT findings between severe and critical H1N1 pneumonia

“…Air trapping was depicted in three critical patients, among whom one patient had multiple pneumatoceles in bilateral lung and right hydropneumothorax during treatment. Cristina et al 21 reported that the appearance of air trapping was due to airway obstruction which was an essential factor in patients with dyspnea. Furthermore, we found that pulmonary parenchyma involvement was more common than airway involvement in both severe and critical patients, which may be related to the fact that the H1N1 virus is more likely to involve the alveolar rather than the bronchiolar epithelium 16 …”