Acute respiratory distress syndrome is as important as inhalation injury for the development of respiratory dysfunction in major burns.

Respiratory dysfunction is common after major burns. The pathogenesis is, however, still under debate. The aim was to classify and examine underlying reasons for respiratory dysfunction after major burns. Consecutive adult patients (n=16) with a total burned body surface area of 20% or more who required mechanical ventilation were assessed for acute respiratory distress syndrome (ARDS), inhalation injury, sepsis, ventilator-associated pneumonia (VAP), ventilator-induced lung injury (VILI), using conventional criteria, together with measurements of cardiovascular variables and viscoelastic properties of the lung including extravascular lung water. Nine patients developed ARDS within 6 days of injury. ARDS was characterized by a large reduction in the PEEP-adjusted PaO(2):FiO(2) ratio, pulmonary compliance, and increased extra vascular lung water together with increased renal dysfunction rates. Seven patients fulfilled the criteria for inhalation injury. They also had decreased PaO(2):FiO(2) ratios. There was an increase in extra vascular lung water and a decrease in compliance measures though not to the same extent as in the ARDS group. White blood cell counts dropped from (mean) 21.4x10(9)l(-1) (95% CI 15.3-27.5) in day 1 to 4.3x10(9)l(-1) (2.2-6.5) on day 3, and lower values tended to correlate with the development of ARDS. Sepsis occurred before onset of ARDS in only three cases. One patient fulfilled the criteria for VAP, but none was thought to have VILI. We found that respiratory dysfunction after burns is multifactorial, and ARDS and inhalation injury are most important. The early onset of ARDS, together with the changes in white blood cell count and organ dysfunction, favours a syndrome in which respiratory distress is induced by an inflammatory process mediated by the effect of the burn rather than being secondary to sepsis. The power of these conclusions is, however, hampered by the small number of patients in this study.