We included children less than 18 years old who were intubated and mechanically ventilated and who received CPT from a physical therapist, but excluded preterm neonates and children who did not receive CPT, were ventilated for longer than 3 months, died within 1 day after extubation, or stopped receiving CPT more than 2 days before extu- bation. When a child was intubated on multiple separate occasions (i.e., not re-intubated within 1 day), each intu- bation was treated as a separate case.