Artificial ventilation

Artificial ventilation, also called artificial respiration, is a means of assisting or stimulating respiration. Respiration is the overall metabolic process that exchanges gases in the body through pulmonary ventilation, external respiration, and internal respiration. Artificial ventilation may take the form of manually providing air for a person who is not breathing or is not making sufficient respiratory effort, or it may take the form of mechanical ventilation involving the use of a ventilator to move air in and out of the lungs when an individual is unable to breathe on their own, such as during surgery with general anesthesia or when an individual is in a coma or trauma.

Pulmonary ventilation is done by manual insufflation of the lungs either by the rescuer blowing into the patient's lungs (mouth-to-mouth resuscitation), or by using a mechanical device. Mouth-to-mouth resuscitation is also part of cardiopulmonary resuscitation (CPR) making it an essential skill for first aid. In some situations, mouth to mouth is also performed separately, for instance in near-drowning and opiate overdoses. The performance of mouth to mouth on its own is now limited in most protocols to health professionals, whereas lay first aiders are advised to undertake full CPR in any case where the patient is not breathing. This method of insufflation has been proved more effective than methods which involve mechanical manipulation of the patient's chest or arms, such as the Silvester method.

Mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This involves the use of ventilator assisted by a registered nurse, physician, physician assistant, respiratory therapist, paramedic, or other suitable person compressing a bag valve mask. Mechanical ventilation is termed "invasive" if it involves any instrument penetrating through the mouth (such as an endotracheal tube) or the skin (such as a tracheostomy tube). There are two main modes of mechanical ventilation within the two divisions: positive pressure ventilation, where air (or another gas mix) is pushed into the trachea, and negative pressure ventilation, where air is, in essence, sucked into the lungs.

Tracheal intubation is often used for short-term mechanical ventilation. It's when a tube is inserted through the nose (nasotracheal intubation) or mouth (orotracheal intubation) and advanced into the trachea. In most cases tubes with inflatable cuffs are used for protection against leakage and aspiration. Intubation with a cuffed tube is thought to provide the best protection against aspiration. Downside of tracheal tubes is the pain and coughing that follows. Therefore, unless a patient is unconscious or anesthetized, sedative drugs are usually given to provide tolerance of the tube. Other disadvantages of tracheal intubation include damage to the mucosal lining of the nasopharynx or oropharynx and subglottic stenosis.

In an emergency a cricothyrotomy can be used by health care professionals, where an airway is inserted through a surgical opening in the cricothyroid membrane. This is similar to a tracheostomy but a cricothyrotomy is reserved for emergency access. This is usually only used when there is a complete blockage of the pharynx or there is massive maxillofacial injury, preventing other adjuncts being used.

A rhythmic pacing of the diaphragm is caused with the help of electrical impulses. Diaphragm pacing is a technique used by persons with spinal cord injuries who are on a mechanical ventilator to aid with breathing, speaking, and overall quality of life. It may be possible to reduce reliance on a mechanical ventilator with diaphragm pacing. Historically, this has been accomplished through the electrical stimulation of a phrenic nerve by an implanted receiver/electrode, though today an alternative option of attaching percutaneous wires to the diaphragm exists.

The Greek physician Galen may have been the first to describe artificial ventilation: "If you take a dead animal and blow air through its larynx through a reed, you will fill its bronchi and watch its lungs attain the greatest distention." Vesalius too describes ventilation by inserting a reed or cane into the trachea of animals.

It wasn't until 1773, when an English physician William Hawes (1736–1808) began publicizing the power of artificial ventilation to resuscitate people who superficially appeared to have drowned. For a year he paid a reward out of his own pocket to any one bringing him a body rescued from the water within a reasonable time of immersion. Thomas Cogan who was another English physician had become interested in the same subject during a stay at Amsterdam.