What are the differences between positive-pressure and negative-pressure ventilators for the treatment of respiratory failure?

Updated: Jul 25, 2018
  • Author: Ata Murat Kaynar, MD; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

For air to enter the lungs, a pressure gradient must exist between the airway and the alveoli. This can be accomplished either by raising pressure at the airway (positive-pressure ventilation) or by lowering pressure at the level of the alveolus (negative-pressure ventilation).

The iron lung or tank ventilator is the most common type of negative-pressure ventilator used in the past. These ventilators work by creating subatmospheric pressure around the chest, thereby lowering pleural and alveolar pressure and facilitating flow of air into the patient’s lungs. These ventilators are bulky and poorly tolerated and are not suitable for use in modern critical care units. Positive-pressure ventilation can be achieved via an endotracheal or tracheostomy tube or noninvasively through a nasal mask or face mask.


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