Changes in the work of breathing induced by tracheotomy in ventilator-dependent patients

Tracheotomy is widely performed on ventilator-dependent patients, but its e ffects on respiratory mechanics have not been studied. We measured the work of breathing (WOB) in eight patients before and after tracheotomy during b reathing at three identical levels of pressure support (PS): baseline lever (PS-B), PS + 5 cm H2O (PS+5), and PS - 5 cm H2O (PS-5). After the procedur e, we also compared the resistive work induced by the patients' endotrachea l tubes (ETTs) and by a new tracheotomy cannula in an in vitro bench study. A significant reduction in the WOE was observed after tracheotomy for PS-B (from 0.9 +/- 0.4 to 0.4 +/- 0.2 J/L, p < 0.05), and for PS-5 (1.4 +/- 0.6 to 0.6 +/- 0.3 J/L, p < 0.05), with a near-significant reduction for PS+5 (0.5 +/- 0.5 to 0.2 +/- 0.1 J/L, p = 0.05). A significant reduction was als o observed in the pressure-time index of the respiratory muscles (181 +/- 9 2 to 80 +/- 56 cm H2O s/min for PS-B, p < 0.05). Resistive and elastic work computed from transpulmonary pressure measurements decreased significantly at PS-B and PS-5. A significant reduction in occlusion pressure and intrin sic positive end-expiratory pressure (PEEP) was also observed for all condi tions, with no significant change in breathing pattern. Three patients had ineffective breathing efforts before tracheotomy, and all had improved sync hrony with the ventilator after the procedure. In vitro measurements made w ith ETTs removed from the patients, with new ETTs, and with the tracheotomy cannula showed that the cannula reduced the resistive work induced by the artificial airway. Part of these results was explained by a slight, subtle reduction of the inner diameter of used Errs. We conclude that tracheotomy can substantially reduce the mechanical workload of ventilator-dependent pa tients.