Endotracheal Intubation refers to the placement of a tube directly into the trachea, or windpipe, and is done for a variety of reasons. Its use is not limited to anesthesia; it is often used in the Intensive Care Unit for patients requiring assisted breathing or lung protection. These same two reasons are why endotracheal intubation is commonly used during general anesthesia.

When assistance with breathing is required, the endotracheal tube allows for the use of "positive pressure" ventilation, where gas mixtures are pushed into the lungs as opposed to normal breathing where air is pulled into the lungs. In order for positive pressure ventilation to work in a controllable and predictable fashion, we must be assured that all of the gas that we are trying to put into the lungs actually gets there, and doesn't leak out into the atmosphere or go somewhere else such as the stomach. To this end, the placement of an endotracheal tube essentially ensures a closed system that connects us directly to the lungs.

Endotracheal tubes are also used to help prevent a complication known as pulmonary aspiration. Most endotracheal tubes have a "cuff," or inflatable balloon-like structure, that surrounds the tip of the tube within the trachea. When this cuff is inflated, it expands to contact the wall of the trachea thus sealing it off from the remainder of the throat. In this manner an endotracheal tube can help provide "artificial reflexes" to prevent entry of foreign materials into the lungs.

Placement of endotracheal tubes

The standard method of placing an endotracheal tube is the oral route, i.e., through the mouth, under direct visualization. This is by far the most widespread method of intubation. In the setting of anesthesia, the patient is anesthetized, either intravenously or by breathing a mixture of anesthetizing gases. Then, the mouth is opened and an instrument called a laryngoscope is placed within the mouth. The laryngoscope can be thought of as a lighted tongue blade; it lifts the tongue and sweeps it out of the way, and a small light source illuminates the inside of the mouth so that the larynx ("voice box") can be seen. The larynx encloses the vocal cords and is the gateway to the lungs. Under direct visualization the endotracheal tube is inserted in between the vocal cords and into the trachea, where the cuff is inflated and the proper position of the tube is confirmed.

Sometimes, though, the oral route is either not possible or not preferred. For surgery within the mouth, an endotracheal tube placed orally might be in the surgeon's way. And some patients, due to abnormalities in their mouth, throat, or jaw, may not allow adequate opening of their mouth for successful placement of the endotracheal tube by routine methods. Thus there are alternatives to the direct oral route. Endotracheal tubes may be placed nasally (through the nostrils) if it is desired to keep them out of the mouth; and there are a variety of techniques for successfully placing them when patient factors preclude direct visualization of the larynx, some using fiber optics. If the direct visualization method is not feasible, the patient is usually not as deeply anesthetized during placement, so that the patient continues to breathe normally until the tube is correctly located and assisted breathing can be instituted. In this case local anesthetics are used to numb the mouth, nose, and throat, and IV sedation is given as tolerated. The sedation typically induces amnesia of the procedure, so patients usually don't remember it.

Most people who are intubated don't encounter major problems as a result, however, as with any medical procedure, there can be complications. In general these complications involve trauma to structures within the mouth and throat, including teeth and vocal cords. Persons with loose or diseased teeth are more prone to having one become dislodged during intubation. In like manner, those with dental work such as crowns are at increased risk for problems. The upper front teeth are usually the ones involved.