Clinical characteristics and outcomes of patients with 2009 influenza A(H1N1) virus infection with respiratory failure requiring mechanical ventilation

J Crit Care. 2011 Apr;26(2):186-92. doi: 10.1016/j.jcrc.2010.05.031. Epub 2010 Aug 4.


Purpose: The purpose of the study was to describe the clinical characteristics and outcomes of critically ill patients with 2009 influenza A(H1N1).

Methods: An observational study of patients with confirmed or probable 2009 influenza A(H1N1) and respiratory failure requiring mechanical ventilation was performed.

Results: We studied 96 patients (mean age, 45 [14] years [mean, SD]; 44% female). Shock and acute respiratory distress syndrome were diagnosed during the first 72 hours of admission in 43% and 72% of patients, respectively. Noninvasive positive pressure ventilation was used in 45% of the patients, but failed in 77% of them. Bacterial pneumonia was diagnosed in 33% of cases, 8% during the first week (due to community-acquired microorganisms) and 25% after the first week (due to gram-negative bacilli and resistant gram-positive cocci). Intensive care unit mortality was 50%. Nonsurvivors differed from survivors in the prevalence of cardiovascular, respiratory, and hematologic failure on admission and late pneumonia. Reported causes of death were refractory hypoxia, multiorgan failure, and shock (50%, 38%, and 12% of all causes of death, respectively).

Conclusions: Patients with 2009 influenza A(H1N1) and respiratory failure requiring mechanical ventilation often present with clinical criteria of acute respiratory distress syndrome and shock. Bacterial pneumonia is a frequent complication. Mortality is high and is primarily due to refractory hypoxia.

MeSH terms

  • Adult
  • Female
  • Hospital Mortality
  • Humans
  • Hypoxia / etiology
  • Hypoxia / mortality
  • Influenza A Virus, H1N1 Subtype*
  • Influenza, Human / complications
  • Influenza, Human / mortality*
  • Male
  • Middle Aged
  • Multiple Organ Failure / etiology
  • Multiple Organ Failure / mortality
  • Pneumonia, Bacterial / complications
  • Pneumonia, Bacterial / mortality
  • Positive-Pressure Respiration
  • Respiratory Distress Syndrome / etiology
  • Respiratory Distress Syndrome / mortality*
  • Severity of Illness Index
  • Shock / etiology
  • Shock / mortality*