Mechanical ventilation

Mechanical ventilation is a form of breathing during which the flow of gases through the respiratory system is fully or partially achieved by a mechanical machine. Mechanical ventilation can be used for short or long periods in situations where the support of the patient's respiratory system is necessary due to the development of a severe ventilatory or oxygenation disorder, or if they are at risk of developing it. . Mechanical ventilation can be maintained non-invasively using various masks, or invasively, where the use of adequate advanced airway management utilizing e.g. endotracheal intubation or tracheostomy is necessary.

Indication
Mechanical ventilation should be considered if clinical or laboratory signs of insufficient oxygenation or ventilation are present. The consideration of mechanical ventilation must concern the complete health state of the patient and can vary individually a lot. We assess the character of the underlying disease, the prognosis, risks and the responsiveness to conservative therapy. Criteria for indication can therefore differ source to source.

A specific group of indications is the protection from the risk of aspiration in patients with altered consciousness (overdose, craniotrauma) or in a state increasing the risk of aspiration concerning the gastrointestinal tract (bleeding from esophageal varices).

Mechanical ventilation is also indicated in pharmacologically induced ventilatory insufficiency, notably during the conduction of general anaesthesia (together with the protection of airways during the alteration of consciousness).

==== Examples of states necessitating the mechanical ventilation in intensive care ====


 * Processes filling the alveoli – pneumonitis (infectious, aspiration), non-cardiogenic pulmonary edema/ARDS (infection, inhalation trauma, drowning, after transfusion, contusion, altitude sickness), cardiogenic pulmonary edema, pulmonary hemorrhage, tumor (e.g. choriocarcinoma), pulmonary alveolar proteinosis, intravascular hypervolemia.
 * Diseases of pulmonary vessels – pulmonary thromboembolism, embolism by amniotic fluid, embolism by tumor mass.
 * Central airway obstruction – tumor, laryngeal angioedema, tracheal stenosis.
 * Distal airway obstruction – exacerbation of COPD, severe acute asthma.
 * Hypoventilation from central causes – general anaesthesia, drug overdose.
 * Hypoventilation from peripheral neuro-muscular causes – ALS, tetraplegia, Guillain-Barré syndrome, myasthenia gravis, tetanus, toxins (strychnin), muscular and myotonic dystrophias, myositides.
 * Hypoventilation due to a disease of the chest wall or the pleura – kyphoscoliosis, trauma (flail chest), massive pleural exudate, pneumothorax.
 * Increase in required ventilation – severe sepsis, septic shock, severe metabolic acidosis.

Goals of the ventilation therapy
The ACCP conference in 1993 classified the goals of mechanical ventilation into physiological and clinical in the following way.
 * Physiological goals include:
 * manipulation with the gas exchange in the lungs,
 * support of alveolar ventilation (manipulation with PaCO2 and pH),
 * support of arterial oxygenation (manipulation with PaO2, the saturation of arterial blood by oxygen),
 * influencing the pulmonary volumes,
 * increase of end-inspiratory pulmonary volume or the maintenance of functional residual capacity,
 * decrease of respiratory effort,
 * synergy with respiratory muscle effort.
 * Some of the main clinical goals include:
 * reversal of hypoxemia,
 * reversal of acute respiratory acidosis,
 * reversal of respiratory distress.

In some patients other goals of mechanical ventilation may be established. A special case of utilizing mechanical ventilation is the conduction of inhalational anaesthesia.