You may receive endotracheal intubation and mechanical ventilation if you are in an emergency situation involving severe respiratory problems or if you are having general anesthesia during a surgical procedure. When you breathe, air moves into your lungs when a muscle called the diaphragm, along with other muscles nearby, contracts and causes the chest cavity to expand. Air is exhaled when these muscles relax, and the lung tissue passively returns to its original size. This is called respiration. During respiration, oxygen in the air passes through your nose or mouth and into your pharynx, or throat. It then goes into your trachea, or windpipe. Your trachea divides to become the left and right main bronchi, which enter your lungs. Inside your lungs, the main bronchi divide repeatedly and eventually become small tubes called bronchioles. At the end of the bronchioles are tiny air sacs called alveoli. Oxygen in your alveoli is absorbed into nearby blood vessels called capillaries. At the same time, carbon dioxide, a gas in your blood that must be removed, passes into to the alveoli and back out through the airways. This process is called gas exchange. If you have severe respiratory problems, the oxygen levels in your blood may drop too low, or the carbon dioxide levels may rise too high. Either of these conditions can result in damage to your vital organs, including your heart and brain. Some conditions that may lead to severe respiratory problems include: drowning, an obstruction in the trachea, such as a foreign object or tumor, obstructive pulmonary diseases such as asthma, chronic bronchitis, and emphysema, diseases such as pneumonia and acute respiratory distress syndrome, or A-R-D-S, severe weakness of the muscles that control breathing, and damage to the bones and tissues of the chest. Under these circumstances, you may need additional oxygen or breathing support through mechanical ventilation. Mechanical ventilation is also used during surgical procedures for: delivering anesthetic drugs, preventing the aspiration of stomach contents into the lungs, and closely controlling the levels of oxygen and carbon dioxide in the blood during surgery. Before you are intubated and ventilated for a surgical procedure, an intravenous line, or I-V, will be started, and your doctor will give you medication through your IV to put you to sleep. As the medication takes effect, he or she will place an oxygen mask over your nose and mouth and ask you to breathe deeply, ensuring that you will have a reserve of oxygen in your system prior to the procedure. The first step in mechanical ventilation is called endotracheal intubation. Once you are asleep, your doctor will use an instrument called a laryngoscope to perform the intubation. A laryngoscope, which consists of a handle, light, and dull blade, helps guide the endotracheal tube to its proper position. Your doctor will tilt your head back slightly and insert the laryngoscope through your mouth and down into your throat, taking special care to avoid contact with your teeth. Using the blade, your doctor will gently raise the epiglottis, which is a flap of tissue protecting your larynx. He or she will then advance the tip of the endotracheal tube into the trachea. Once the endotracheal tube is in the trachea, your doctor will inflate a small balloon surrounding the tube to make sure it remains snugly in place. Your doctor will remove the laryngoscope and tape the tube to the corner of your mouth to prevent it from being jostled out of position. Your doctor will check to see that the tube is properly positioned in the lower part of the trachea by inflating your lungs with a special bag and listening for breath sounds on both sides of your chest. If the end of the tube is too low, both lungs will not receive the same amount of air. In some cases, an x-ray is taken immediately after intubation to confirm the tube’s placement. Once the endotracheal tube is in the proper position, your doctor will attach it to the mechanical ventilator, a specially designed pump that aids respiration by delivering well-oxygenated air into the lungs and permitting carbon dioxide to escape from the lungs. Levels of oxygen and carbon dioxide will be closely monitored to confirm that the ventilator is working. Once your surgical procedure is complete, your doctor will not remove the endotracheal tube until you are able to safely breathe on your own. He or she will make this determination by measuring how often you take a breath and how much air you breathe in and out with each breath.