In some cases, if the mouth or throat is being operated upon, the tube is threaded through the nose instead of the mouth, which is called a nasal intubation, which is then threaded into the airway. This is done to keep the mouth empty and allow the surgery to be performed.
Intubation is required when general anesthesia is given. The anesthesia drugs paralyze the muscles of the body, including the diaphragm, which makes it impossible to take a breath without a ventilator.
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