Intubation is the procedure in which a tube is passed through a patient's nose or mouth into the airway. This is commonly carried out before an operation when the patient will be attached to a breathing machine. The intubation response is the body's natural reaction to the introduction of a tube into the larynx, or voice box, which forms the entrance to the airways. As the larynx is full of nerve endings, intubation triggers numerous responses involving the heart, circulation and respiratory passages. The heart may beat faster, blood pressure may rise and the airways or larynx may go into spasm as part of the intubation response.
Anesthetists, who administer anesthetics and care for patients during operations, are the doctors who carry out intubation. They receive special training into the effects of intubation and learn intubation techniques and strategies to avoid or minimize an intubation response. The main reasons for intubation are to keep the airway open and to enable breathing assistance during an operation. Breathing assistance is required when the patient's muscles are paralyzed during surgery. A preliminary, fast-acting anesthetic is usually given into a vein before intubation and, during an operation, anesthetic gases are administered via the breathing machine to keep patients unconscious.
One important intubation response is the effect on the patient's heart and circulation. The faster heart rate, increased risk of abnormal heart rhythms and rise in blood pressure could have serious consequences for patients with existing heart problems or high blood pressure. Medication may be given before intubation to reduce the risk of this type of response. For patients with heart disease, the anesthetist ensures patients are anesthetized deeply enough before intubation to suppress any response.
Another intubation response can occur in the airways, when the larynx and respiratory passages go into spasm. This can make it difficult to insert a breathing tube, and is referred to as a difficult intubation. Sometimes the anesthetist can manage a spasm of the larynx by maneuvering the jaw but, if not, medication may be needed to relax the muscles.
Drugs can be used to treat spasming airways. As an intubation response can increase the pressure in the skull, this puts patients with head injuries at risk of a bleed into the brain. Anesthetists try to avoid provoking a response by intubating only when the patient is already deeply anesthetized.
The intubation response in smokers is different from that seen in non-smokers, because smokers experience an even greater increase in heart rate and larger variations in blood pressure. As smokers are more likely to have existing heart disease and to have lower levels of oxygen in the blood, the heightened intubation response leaves them at risk of experiencing angina or a heart attack. Smokers are encouraged to give up their habit at least 48 hours before surgery.