Measurement of lung water in inhalation injury

Pulmonary inhalation injury is a major cause of morbidity and mortality rates in burn victims. But the pathophysiology of parenchymal inhalation injury has not been fully elucidated. In this study, extravascular lung water volume (EVLW) was measured in burn patients with and without inhalation injury. Patients with parenchymal inhalation injury (group II) had elevated admission extravascular lung water volumes (10.12 +/- 3.43 ml/kg), whereas patients without parenchymal injury (group I) had significantly lower lung water values (3.91 +/- 1.49 ml/kg). Both accumulation of EVLW and ventilation-perfusion abnormalities in the group II patients occurred within hours of smoke inhalation. But the severity of inhalation injury did not consistently correlate with the elevation of EVLW. This indicated that both interstitial edema and ventilation-perfusion imbalance contributed, in varying degrees, to the pathophysiology of inhalation injury. In this study, the general clinical criteria for inhalation injury--presence of facial or oropharyngeal burns, carboxyhemoglobin levels, carbonaceous sputum, or closed space injury--did not differentiate patients with airway injury only from those with parenchymal injury. Patients in both groups who died of sepsis had significant (P less than 0.01) increases in EVLW 24 to 48 hours after the clinical onset of sepsis. The normal hydrostatic pressures in these septic patients suggested that the increase in EVLW observed with sepsis was due to an increase in pulmonary capillary membrane permeability.