atelectasis FRCIt is extremely important to recognize the time frame of these changes. After surfactant administration, there may be very rapid improvements in pulmonary function that necessitate rapid weaning of ventilator settings. Close attention must be paid to tidal volume, blood gas tensions, transcutaneous CO2 and pulse oximetry values in order to avoid inadvertent hyperventilation, hyperoxia and overdistension of the lung, all of which can result in lung injury.