title: Chest Radiological Findings of Patients With Severe H1N1 Pneumonia Requiring Intensive Care.
abstract: BACKGROUND
  A new strain of human influenza A (H1N1) virus originated from Mexico in 2009 and spread to more than 190 countries and territories. The World Health Organization (WHO) declared it a level 6 (highest level) pandemic. In August 2010, WHO announced that the H1N1 2009 influenza virus had moved into the postpandemic period. The WHO also declared that this flu strain is expected to continue to circulate as a seasonal virus "for some years to come." The objective of this study is to describe the chest radiographic and computed tomography (CT) findings of patients with severe H1N1 pneumonia admitted to the intensive care unit (ICU) during the 2009 pandemic.
  
  
  OBJECTIVE
  Patients with severe H1N1 pneumonia requiring ICU admission have extensive radiographic and CT abnormalities.
  
  
  METHODS
  Eighteen patients, aged 23 to 62 (mean 41), admitted to the ICU at UCLA-Olive View Medical Center with a primary diagnosis of pandemic H1N1 infection, confirmed either via rapid influenza detection test or by real-time reverse transcriptase polymerase chain reaction assay, formed the study population. All patients had chest x-ray (CXR) within 24 hours of admission and 5 patients had CT examinations. In this retrospective study, images were evaluated for the pattern (ground-glass opacities, consolidation, reticular opacities, and nodular opacities), distribution (unilateral/bilateral, upper/middle/lower lung zone, and central/peripheral/peribronchovascular), and extent (focal/multifocal/diffuse; number of lung zones) of abnormalities.
  
  
  RESULTS
  All (100%) patients had abnormal CXR and CT studies. The predominant radiographic findings were ground-glass opacities (16 of 18; 89%), consolidation (16 of 18; 89%), and reticular opacities (6 of 18, 33%). The radiographic abnormalities were bilateral in 17 (94%) patients; involved lower lung distribution in 18 (100%) patients, and mid and lower lung distribution in 16 (89%) patients. Radiographic abnormalities were peribronchovascular in 11 (61%) patients and multifocal in 10 (56%). Sixteen (89%) patients had extensive abnormalities involving 3 or more lung zones. The patients requiring mechanical ventilation had a higher incidence of bilateral, diffuse consolidation in a peribronchovascular distribution on chest radiographs. The predominant CT abnormalities were consolidation (5 of 5; 100%), ground-glass opacities (5 of 5; 100%), and nodular opacities (3 of 5, 60%). The CT findings were peribronchovascular and multifocal in 4 (80%) patients and extensive and bilateral in all (100%) patients.
  
  
  CONCLUSIONS
  Patients with H1N1 pneumonia admitted to the ICU had bilateral, extensive CXR, and CT abnormalities. Consolidations and ground-glass opacities were the most common imaging findings, predominantly affecting mid and lower lung zones. Imaging abnormalities were peribronchovascular and multifocal in a majority of patients.
authors.affiliation: Department of Medicine, UCLA-Olive View Medical Center, Los Angeles, CA, USA.
authors.forename: Payam
authors.initials: P
authors.lastname: Rohani
authors.affiliation: Department of Radiology, Division of Thoracic Imaging, UCLA-Olive View Medical Center, Los Angeles, CA, USA.
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Jude
authors.affiliation: Department of Medicine, UCLA-Olive View Medical Center, Los Angeles, CA, USA.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Chan
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, UCLA-Olive View Medical Center, Los Angeles, CA, USA.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Barot
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, UCLA-Olive View Medical Center, Los Angeles, CA, USA kamangar@ucla.edu.
authors.forename: Nader
authors.initials: N
authors.lastname: Kamangar
mesh_terms: D000328:Adult; D015897:Comorbidity; D003422:Critical Care; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification / Q000472:pathogenicity*; D007251:Influenza, Human / Q000000981:diagnostic imaging / Q000401:mortality / Q000473:pathology* / Q000628:therapy / Q000821:virology; D008297:Male; D008875:Middle Aged; D011024:Pneumonia, Viral / Q000000981:diagnostic imaging / Q000401:mortality / Q000473:pathology* / Q000628:therapy; D013902:Radiography, Thoracic / Q000379:methods; D012121:Respiration, Artificial / Q000401:mortality; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014481:United States / Q000453:epidemiology
keywords: H1N1 pneumonia; chest radiograph; computed tomography; intensive care; radiographic findings