A sterile suspension composed of an extract of bovine pulmonary surfactant with surfactant activity. Calfactant contains phospholipids, neutral lipids, and hydrophobic surfactant-associated proteins B (SP-B) and C (SP-C). Upon intratracheal administration, this agent, mimicking endogenous pulmonary surfactant, lines the alveoli and smallest bronchioles, keeping alveoli open during expiration by lowering surface tension. Resulting improvements in lung compliance and respiratory gas exchange may lead to improvements in ventilation and oxygenation.