Effect of tracheostomy on pulmonary mechanics: An observational study

This study was undertaken to find out the effect of early tracheostomy on weaning from mechanical ventilation. Pulmonary mechanics and arterial blood gases were assessed before and after tracheostomy in patients with severe head injury (Glasgow coma score < 8) requiring prolonged mechanical ventilation.

The study included 20 mechanically ventilated patients of either sex between 20 and 45 years of age, who had suffered brain injury due to head trauma during admission (Glasgow coma scores of < 8). Mean airway pressure, peak airway pressure, plateau pressure, PaO(2) and PaCO(2) were measured 24 h before and after tracheostomy. Static and dynamic compliances were calculated.

Plateau airway pressures were not affected by tracheostomy, but peak airway pressure was reduced (29.90 +/- 3.21 cm H(2)O before tracheostomy versus 24.30 +/- 1.83 cm H(2)O after tracheostomy, P < 0.001). Dynamic compliance, but not static compliance, was improved by tracheostomy. Tracheostomy did not affect PaCO(2), but it improved PaO(2) (83.09 +/- 5.99 mmHg before versus 90.84 +/- 5.61 mmHg after, P < 0.001).

The work of breathing through a tracheostomy tube may be less than through an endotracheal tube of same internal diameter.