Fig. 1

Study protocol. Panel A. Study protocol for group 1. During baseline conditions (A) and after short-term hyperventilation (B) the following parameters were recorded: end-tidal CO₂ (ETCO₂), peripheral capillary oxygen saturation (SpO₂), heart rate (HR), mean arterial pressure (MAP), and auricular temperature (T). Measurements with transcranial color-coded duplex sonography (TCCD) were performed at time points A and B. Panel B. Study protocol for groups 2 and 3. During baseline conditions (A), after short-term hyperventilation (B), stabilization (C), and sustained hyperventilation (D) several parameters were recorded. ETCO₂ remained stable during B, C, and D. TCCD measurements were performed during A, C, and D. An arterial blood gas analysis (ABGA) was obtained during A, C, and D. Only for patients in group 3 were values for intracranial pressure (ICP) and cerebral perfusion pressure (CPP) noted during A, B, C, and D. MV: minute volume