29-year-old housewife is brought to the emergency department following exposure to smoke during a house fire. she is breathing at a rate of 30 breaths/min. her heart rate is 110 beats/min. blood pressure is 160/110 mm hg. the patient complains of headaches and nausea. the pulse oximeter reading shows a saturation of 99%. why are pulse oximeter readings unreliable in this setting?
