The main purpose of the study is to compare two ultrasound-guided arterial cannulation procedures: in-plane infraclavicular axillary artery cannulation and out-of-plane femoral artery cannulation.

Inclusion Criteria:

mechanically ventilated critically ill patients with indications for artery cannulation:

• in whom radial artery cannulation is unable to perform or
• in order to conduct hemodynamic monitoring using transpulmonary thermodilution

Exclusion Criteria:

• age less than 18 years
• trauma and hematoma at the catheterization site
• clinically significant coagulation disorders
• infection at the catheterization site
• lack of patients or closest relatives contents
• precedent surgery operation into the femoral and axillary arteries
• clinically significant ischemia of the limb at the cannulation side