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Mechanical ventilation


Description


Mechanical ventilation is the process by which room air or oxygen-enriched air is moved in and out of the lungs by a mechanical ventilator. Mechanical ventilation is not curative. It is a means of supporting patients until they recover the ability to breathe independently, as a bridge to long-term mechanical ventilation, or until a decision is made to withdraw ventilatory support. Indications for mechanical ventilation include (1) apnea or an impending inability to breathe, (2) acute respiratory failure, (3) severe hypoxia, and (4) respiratory muscle fatigue.


Types of mechanical ventilators


The two major types of mechanical ventilation are negative pressure and positive pressure ventilation.



■ Negative pressure ventilation involves the use of chambers that encase the chest or body and surround it with intermittent subatmospheric or negative pressure. Intermittent negative pressure around the chest wall causes the chest to be pulled outward. This reduces intrathoracic pressure. Air rushes in through the upper airway, which is outside the sealed chamber. Expiration is passive; the machine cycles off, allowing chest retraction. This type of ventilation is similar to normal ventilation in that decreased intrathoracic pressures produce inspiration and expiration is passive. Negative pressure ventilation delivers noninvasive ventilation and does not require an artificial airway.


■ Several portable negative pressure ventilators are available for home use for patients with neuromuscular diseases, central nervous system disorders, diseases and injuries of the spinal cord, and severe chronic obstructive pulmonary disease (COPD). Negative pressure ventilators are not used extensively for acutely ill patients.


■ Positive pressure ventilation (PPV) is the primary method used with acutely ill patients. During inspiration, the ventilator pushes air into the lungs under positive pressure. Unlike spontaneous ventilation, intrathoracic pressure is raised during lung inflation rather than lowered. Expiration occurs passively as in normal expiration. PPVs are categorized into volume and pressure ventilators.

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Oct 26, 2016 | Posted by in NURSING | Comments Off on M

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