With the information given above it is obvious the patient is dyspneic due to the hemoglobin being 5.8 grams. The hemoglobin molecule on erythrocytes transports oxygen throughout the body. A hemoglobin count of 5.8 is severely low (normal for adult is 12-14 grams/dl). The patient doesn't have enough red blood cells/hemoglobin to supply the needs of the body. The patient is dyspneic and probably tachypneic in an effort to pull in more oxygen.
Initial treatment of this patient would include administration of supplemental oxygen probably by non re-breather mask at 15L/min. to increase the pAO2 and decrease the PCO2. Second, you must find out why the hemoglobin is so low. Is the patient bleeding? If so, it must be stopped. This patient will also require infusion of at least three units of PRBC's (packed red blood cells). This must be carried out immediately. This situation is a true emergency. If the hemoglobin is not corrected very soon, this patient will go into respiratory failure and may die.