Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs.
Some people with respiratory failure need a mechanical ventilator (a machine that helps air get in and out of the lungs) to aid breathing. Mechanical ventilation can be lifesaving.
Mechanical ventilation can be delivered many ways. Usually a plastic tube is inserted through the nose or mouth into the windpipe (trachea). If people need mechanical ventilation for more than a few days, doctors may insert the tube directly into the trachea through a small incision in the front of the neck (tracheostomy). A tracheostomy is safer and more comfortable for long-term ventilation. The tube is then attached to the ventilator. A ventilator can push air into the lungs even if the person does not inhale.
Many types of ventilators and modes of operation may be used, depending on the underlying disorder. Depending on the person’s needs, the ventilator delivers pure oxygen or a mixture of oxygen and air.
Alternatives to Mechanical Ventilation
Some people do not require complete support of their breathing. These people may be treated with a tight-fitting mask placed over the nose or nose and mouth. A mixture of oxygen and air is delivered under pressure through the mask. The pressure assists the person’s own breathing efforts and prevents fatigue of the respiratory muscles. In about half of the people with respiratory failure, this technique (called bilevel positive airway pressure [BPAP], or continuous positive airway pressure [CPAP]) can help people avoid the need for a tracheostomy.
Use of bilevel positive airway pressure at night can help people whose respiratory failure is caused by muscle weakness, because after resting at night, the respiratory muscles are able to function more effectively during the day.
Complications of Mechanical Ventilation
Pushing air into the lungs under too much pressure or with too high a volume can overstretch the lungs and cause lung damage. Sometimes the fragile alveoli (small air sacs in the lungs) rupture, allowing air to accumulate around the lung and collapse it, a condition called pneumothorax. To avoid these problems, doctors try to limit the volume and pressure of air delivered by the ventilator. On the other hand, too little pressure and volume may not move enough air in and out, causing the level of carbon dioxide in the blood to become too high and letting the small airways and alveoli close. Doctors constantly monitor and adjust the frequency and size of breaths delivered by the ventilator and the ventilator pressure to strike a careful balance.
Although most people undergoing mechanical ventilation need extra oxygen, too much oxygen actually can damage the lungs. Doctors monitor the person’s oxygen level to ensure that just the right amount is given.
When the trachea is intubated, bacteria from the nose and mouth can easily enter the lungs and cause serious infection. These infections must be diagnosed and treated as quickly as possible.
Because people on mechanical ventilation cannot eat, nutritional support is usually provided by giving liquid supplements through a tube positioned in the stomach (tube feeding).
Stopping Mechanical Ventilation
As the person recovers from the disorder that led to lung dysfunction, doctors try to decrease the support for breathing. They may temporarily turn the ventilator off to see whether the person's lungs are able to function without support. Such trials are done with careful monitoring so that the ventilator can be quickly restarted should the need arise.
