Difficult Weaning Which Mechanisms Are Associated with Long-Term Ventilator Dependence

Loyola Univetsity of Chicago Stritch School of Medicine and Edward Hines, Jr. Veterans Administration Hospital, Maywood, Illinois, U.S.A. 

Each year, over 400,000 patients in the United States receive mechanical ventilation as a result of acute or acute-on-chronic respiratory failure (1,2). About a quarter of acutely ventilated patients repeatedly fail attempts at weaning and may require prolonged mechanical ventilation (PMV) (Fig. 1) (3,4). The proportion of patients experiencing PMV ranges between 0% and 20% (5-13). Out of patients who survive PMV, 9-66% become dependent on long-term mechanical ventilation (LTMV) (4,9,14-21). Two factors account for these wide variations in the outcome. The first factor is differences in patient population. The second one is the nosology of what constitutes PMV and what constitutes LTMV is unsatisfactory. 

Due to the current limitations in nosology and the paucity of research in the field, 1 will discuss potential mechanisms associated with LTMV based on principles of pulmonary pathophysiology recorded in patients requiring mechanical ventilation for variable periods of time, including those in the acute care setting. Whether it is valid to extrapolate pathophysiological data recorded in the acute care setting to the chronic one is, however, unknown. 

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Causes of Difficult Weaning Which Mechanisms Are Associated with Long-Term Ventilator Dependence ... 

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