Community-acquired pneumonia: Evidence of functional inactivation of α1 proteinase inhibitor
Quantitative and qualitative elastase inhibitory capacity (EIC) α1 proteinase inhibitor (α1PI) was measured in pulmonary arterial and systemic arterial blood of patients with community-acquired pneumonia (CAP). Eleven patients with uncomplicated CAP were compared with 16 patients with fulminating pneumonia requiring intensive care management. An appropriate increase in quantitative α1PI was demonstrated in all patients. A significant functional inactivation of α1PI was demonstrated in the ICU-treated patients that was not apparent in the uncomplicated CAP patients (p < .01). This low EIC returned to normal 4 wk after hospital discharge in all survivors. A significant (p < .02) difference in EIC between the pulmonary arterial and systemic arterial blood was found in the nonsurvivors on admission, which suggests that α1PI is inactivated in the lungs of patients with fulminating CAP. The present data demonstrate that α1PI is functionally inactivated in patients with fulminating CAP. This low serum functional α1PI may result in proteolytic lung damage and an unfavorable outcome.