Community-acquired pneumonia: evidence of functional inactivation of alpha 1 proteinase inhibitor.
 Quantitative and qualitative elastase inhibitory capacity (EIC) alpha 1 proteinase inhibitor (alpha 1 PI) 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 alpha 1 PI was demonstrated in all patients.
 A significant functional inactivation of alpha 1 PI was demonstrated in the ICU-treated patients that was not apparent in the uncomplicated CAP patients (p less than .01).
 This low EIC returned to normal 4 wk after hospital discharge in all survivors.
 A significant (p less than .02) difference in EIC between the pulmonary arterial and systemic arterial blood was found in the nonsurvivors on admission, which suggests that alpha 1 PI is inactivated in the lungs of patients with fulminating CAP.
 The present data demonstrate that alpha 1 PI is functionally inactivated in patients with fulminating CAP.
 This low serum functional alpha 1 PI may result in proteolytic lung damage and an unfavorable outcome.
