<unk>  results from inadequate gas exchange by the<unk>  system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia.<unk>  is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of<unk>  usually includes increased<unk>  rate, abnormal blood gases (hypoxemia, hypercapnia, or both), and evidence of increased work of breathing.<unk>  causes an altered mental status due to ischemia in the brain. The typical partial pressure reference values are oxygen Pa O2 more than 80 mmHg (11 kPa) and carbon dioxide Pa CO2 less than 45 mmHg (6.0 kPa).
Respiratory failure
Respiratory compromise
Pulmonary toxicity
Liver failure
Sleep paralysis
Pulmonary insufficiency
Neurotoxicity
Sedation