If the baby suddenly worsens after successful ET intubation, the team must quickly troubleshoot for possible causes and take corrective action. The tube may have been inadvertently displaced, or the airway may be obstructed. The baby may have developed a pneumothorax, or some part of the resuscitation equipment may have ceased to work correctly. 

The DOPE mnemonic helps the team think through possible causes of a sudden deterioration after successful intubation.