Surfactant protein-A levels in patients with acute respiratory distress syndrome.

BACKGROUND & OBJECTIVES: The decrease in surfactant protein-A (SP-A level) has recently been implicated in the pathophysiology of acute respiratory distress syndrome (ARDS). Mechanical ventilation is the main modality of treatment of ARDS. But information on the SP-A levels after mechanical ventilation is scanty. We therefore studied the effect of mechanical ventilation on SP-A levels in patients with ARDS. METHODS: In a prospective, observational study conducted in the Respiratory Intensive Care Unit of a tertiary care hospital in north India, 13 patients with ARDS requiring mechanical ventilation were included. SP-A levels in the bronchial aspirates were serially estimated by ELISA at the start of mechanical ventilation and after 24 and after 48 h. RESULTS: The SP-A level at the start of mechanical ventilation was 3.06 +/- 2.56 microg/ml. The levels gradually increased to 3.99 +/- 2.39 and 6.64 +/- 2.72 microg/ml, at 24 and 48 h respectively, and this increase was statistically significant (P < 0.05). Patients having an infectious etiology had lower SP-A levels compared to those with non-infections causes. Neither the initial SP-A level nor the increase in SP-A level correlated with the improvement in lung function or duration of ventilation. INTERPRETATION & CONCLUSION: The present study showed a progressive increase in the SP-A levels in patients with ARDS on mechanical ventilation. Further studies are required to confirm that the increase in SP-A levels may be one of the contributors for recovery in ARDS.