We report a case in which morphine in combination with intravenous diazepam delivered via patient-controlled analgesia resulted in complete apnea and carbon dioxide narcosis in a patient admitted for cervical traction. A patent airway and high flow oxygen face mask maintained oxygenation despite complete apnea, thus rendering the pulse oximeter useless in detecting the respiratory depression. The case illustrates the limitations of pulse oximetry in detecting opioid induced respiratory depression when the conditions necessary for apneic oxygenation are present.