Serial Changes in Arterial Blood Gas Parameters Following Tracheostomy in Mechanically Ventilated ICU Patients

Abstract

Background: Tracheostomy is commonly performed in critically ill patients requiring prolonged mechanical ventilation. However, the temporal pattern of arterial blood gas changes following tracheostomy remains incompletely characterized. This study aimed to evaluate serial changes in arterial blood gas parameters following tracheostomy in mechanically ventilated intensive care unit patients.
Methods: This prospective longitudinal observational study included 21 mechanically ventilated patients undergoing tracheostomy. Arterial blood gas parameters were assessed before tracheostomy and on days 1, 3, 5, 7, and 9 after the procedure. The evaluated parameters included pH, PaO₂, PaCO₂, SaO₂, HCO₃⁻, base excess (BE), total oxygen content (ctO₂), and total carbon dioxide content (ctCO₂). Temporal changes were analyzed using repeated-measures analysis of variance, with Greenhouse–Geisser correction applied when the sphericity assumption was violated and Bonferroni-adjusted pairwise comparisons performed for significant overall effects.
Results: Significant overall temporal changes were observed in all arterial blood gas parameters (all p<0.05). Mean pH increased from 7.33±0.07 at baseline to 7.39±0.03 on day 9, PaO₂ from 79.88±10.95 to 91.89±3.55 mmHg, and SaO₂ from 91.56±1.74% to 97.51±0.82%. PaCO₂ demonstrated significant overall temporal variation (p=0.002), with significant differences from baseline observed on days 5 and 7. Bonferroni-adjusted comparisons showed that SaO₂ and ctO₂ were the earliest parameters to differ significantly from baseline, beginning on day 3, whereas other ventilation and acid–base parameters exhibited later or more variable temporal patterns.
Conclusion: Significant serial changes in arterial blood gas parameters were observed during the nine-day post-tracheostomy period, with the earliest and most consistent changes occurring in oxygen saturation and arterial oxygen content. Serial arterial blood gas monitoring may provide valuable physiological information for characterizing post-tracheostomy respiratory changes in mechanically ventilated ICU patients.