Abstract
The objective of mechanical ventilation used in the management of Acute Respiratory Distress Syndrome (ARDS) is to ensure adequate tissue oxygenation and alveolar ventilation while limiting the patients’ work of breathing and preventing further damage to the lungs. Although the “partial support” ventilation modes were initially developed to assist weaning or liberation from supported ventilation, they have gained increasing popularity as primary ventilation modes, even in patients in with severe acute pulmonary dysfunction. Allowing spontaneous breathing is known to alter both lung mechanics and physiological effects of ventilation, therefore has potential influence on important patho-physiological changes and complications that occur. Spontaneous ventilation has the potential to improve outcomes in ARDS, and therefore is worthy of an intensivist’s attention. A clinical trial of the use of pharmaceutical paralysis suggest a protective effect against worsening respiratory failure by ablating spontaneous breathing in ARDS. Overdistension of alveoli, even at low ventilator driving pressures may be as dangerous as high tidal volume (TV) controlled ventilation and thus naïve use of unrestricted spontaneous breathing techniques may be detrimental. As evidence of both improvement and deterioration exist the hypothesis remains controversial, and warrants a properly conducted randomised trial.
Ross Freebairn, Keith Hickling
