Introduction Tracheotomy is widely performed in the intensive care unit
after long-term oral intubation. The present study investigates the
immediate influence of tracheotomy on respiratory mechanics and blood
gases during mechanical ventilation.
Methods Tracheotomy was performed in 32 orally intubated patients for
10.5 +/- 4.66 days (all results are means +/- standard deviations).
Airway pressure, flow and arterial blood gases were recorded immediately
before tracheotomy and half an hour afterwards. Respiratory system
elastance (E-rs), resistance (R-rs) and end-expiratory pressure (EEP)
were evaluated by multiple linear regression. Respiratory system
reactance (X-rs), impedance (Z(rs)) and phase angle (phi(rs)) were
calculated from E-rs and R-rs. Comparisons of the mechanical parameters,
blood gases and pH were performed with the aid of the Wilcoxon
signed-rank test (P = 0.05).
Results E-rs increased (7 +/- 11.3%, P = 0.001), whereas R-rs (-16 +/-
18.4%, P = 0.0003), X-rs (-6 +/- 11.6%, P = 0.006) and phi(rs) (-14.3
+/- 16.8%, P = < 0.001) decreased immediately after tracheotomy. EEP,
Z(rs), blood gases and pH did not change significantly.
Conclusion Lower R-rs but also higher E-rs were noted immediately after
tracheotomy. The net effect is a non-significant change in the overall
R-rs (impedance) and the effectiveness of respiratory function. The
extra dose of anaesthetics (beyond that used for sedation at the
beginning of the procedure) or a higher FiO(2) (fraction of inspired
oxygen) during tracheotomy or aspiration could be related to the
immediate elastance increase
