In diabetic ketoacidosis, very frequently severe hyperventilation with deep respiratory breaths are observed, also called Kussmaul-respiration. This is a compensatory mechanism aiming to get rid of CO2 in cases of severe metabolic acidosis. The blood gases show severely lowered pCO2, a relatively high pO2 with relatively high hemoglobin O2 saturation as well as low standard bicarbonate. Respiratory compensation by hyperventilation is a compensatory mechanism; this is the reason why medications which can decrease respiratory capacity or compensatory mechanisms, like sedatives, should be avoided as long as possible. The indication for tracheal intubation of a patient with diabetic coma is mainly the potential of aspiration in the case of severe coma and vomiting. In most cases it is sufficient and most sensible to let the patient respirate by himself after intubation with a closed cuff to prevent aspiration. In case the patient has to be ventilated mechanically, one should take care to keep up the high respiratory minute volume by high respiratory volume and frequency. If one does not pay attention to that, pCO2 can relatively increase to the bicarbonate level which results in severe acidosis, hyperkalemia and cardiovascular insufficiency.
If patients with compensated metabolic acidosis are intubated and ventilated, the rule of thumb is that, a pCO2-level "1.5-fold of the serum bicarbonate level + 8" should be the goal. If the bicarbonate level is increased in the course of treatment, the ventilation should be adapted correspondingly (32).
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