Severe carbon monoxide poisoning will show the following typical manifestations: 1. The patient’s mouth and lips will be visibly cherry red, and accompanied by neurological symptoms, such as blurred consciousness, impaired consciousness, and the patient may even experience delirium and coma. 2. The patient’s circulatory system will show obvious arrhythmia, tachycardia, palpitations, chest tightness, shortness of breath, and even chest pain. 3. The patient’s respiratory system will show obvious coughing, coughing sputum, even burning sensation in the respiratory tract and transient dyspnea, and in serious cases, respiratory failure. 4. The patient’s digestive system will also show nausea, vomiting, acid reflux, heartburn and even diarrhea, all of which are clinical manifestations of severe carbon monoxide poisoning.