The intubated and mechanically ventilated patient who has an abruptly increased oxygen requirement, is hypoxic, hypotensive, and tachycardic has likely suffered from a pneumothorax that is pressing on the heart, decreasing cardiac output. Therefore, the nurse’s first action is to auscultate breath sounds in all lung fields. Absent breath sounds in one lung field may indicate improper tube placement or the presence of a pneumothorax. The nurse must assess before performing further interventions. It may be necessary to suction the patient’s endotracheal tube, provide manual bag-endotracheal tube ventilation, or call a code blue if the patient’s condition further deteriorates, but these are not the initial actions.