Background: Critically ill patients with acute respiratory failure submitted to an intensive care unit (ICU) are at high risk of cerebral hypoxia. We hypothesized that continuous positive airway pressure (CPAP) therapy may increase regional cerebral oxygenation (rSO2).
Methods: Forty post operative ICU patients requiring oxygen (O2) therapy due to acute respiratory failure were examined in a prospective randomized before after trial. Near-infrared spectroscopy (NIRS, Invos 5100C, Covidien, USA) was used to continuously detect bilateral rSO2 for 15 minutes during classical O2 insufflation via facemask (6 L O2/min = control) and for 15 minutes during the administration of CPAP therapy (40% O2, 8 mbar = intervention), using a randomized cross-over study design where each patient served as own control. Hemodynamic and respiratory routine monitoring and blood gas analysis were performed. A mixed linear model was fitted to test the influence of CPAP therapy and assessed variables on rSO2.
Results: The median rSO2 in the control group was lower (57.3912%) than in the intervention group (63.3113.1%; p<0.0001). The median arterial partial pressure of carbon dioxide (PaCO2) levels were higher in the control group (46.745.1 mmHg) than in the intervention group (43.055 mmHg; p=0.003). Median arterial partial pressure of oxygen (PaO2) and median peripheral hemoglobin oxygen saturation (SpO2) remained unchanged. In total, 23% of patients showed critical rSO2 levels <50%.
Conclusion: Our results reveal that CPAP therapy improves rSO2 compared to classical O2-insufflation therapy in ICU patients with acute respiratory failure. Further, critical rSO2 values <50% can be detected commonly in this patient cohort. Findings suggest that NIRS monitoring may be used to help to detect critical rSO2 and CPAP-therapy may improve rSO2 in ICU patients with acute respiratory failure.