Long-term mechanical ventilation dependence mechanism

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. 

Purro A, Appendini L, De Gaetano A, et al. Physiologic determinants of ventilator dependence in long-term mechanically ventilated patients. Am J Respir Crit Care Med 2000 161(4 pt 1) 1115-1123. 

The risks and benefits of distal tubular diuretics have been assessed in preterm infants under 3 weeks of age with or developing chronic lung disease (36). Acute and chronic administration of distal diuretics improved pulmonary mechanics adverse effects were not reported. However, additional studies are needed to assess whether thiazide administration improves mortality, duration of oxygen dependency, ventilator dependency, length of hospital stay, and long-term outcome in patients exposed to corticosteroids and bronchodilators, and whether adding spironolactone to thiazides or adding metolazone to furosemide has any beneficial effect. 

Scheinhorn D, Hassenpflug M, Votto J, et al. Ventilator-dependent survivors of catastrophic illness transferred to 23 long-term care hospitals for weaning from prolonged mechanical ventilation. Chest 2007 131(l) 76-84. 

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

Figure 1 Conceptual framework linking acute or acute-on-chronic lespiratray failure to jaolonged mechanical ventilation and long-term ventilator dependence. Differences in patient population, imprecise nosology, and paucity of research make it difficult to provide solid indications for when patients may transition from one condition to the next.

Meanwhile, years of productive research have demonstrated that patients with chronic respiratory insufficiency can also benefit from mechanical ventilation. As the Preface of this volume mentions their survival as well as their health status may be dependent on long-term ventilatory support. The ever increasing incidence and prevalence of chronic respiratory disease suggests that the use of ventilatory support will markedly increase. However, the techniques and strategies to use it, and when and where (non-intensive care unit, or home), are very different from treating the respiratory failure resulting from acute conditions and in patients with structurally near normal lungs. 

---