Changes in PaO2 may occur during airway clearing. A decrease below ten kPa is associated with patients with VAP. The relationship between a decrease in PaO2 and the type of suctioning was not established. Lasocki et al.(2006) conducted a study in which they confirmed a statistically significant relationship (p < 0.05) with respect to the type of suction system. In patients with OSS a decrease in PaO2 and an increase in PaCO2 occurred during suctioning and these changes persisted for more than 15 minutes after the suctioning procedure was completed.