Assessment of the Repeatability of Sublingual Microcirculation Function Measurements in Healthy Volunteers and Critically Ill Patients

Group 1: Healthy Volunteers Inclusion Criteria: * ASA Physical Status I-II * Age 18-40 years Exclusion Criteria: * Chronic diseases * Chronic medication use * Pregnancy * Use of stimulants (caffeine, nicotine, alcohol) within 12 hours prior to the study * Lack of consent to participate Group 2: Patients Hospitalized in the ICU Inclusion Criteria: * Age \> 18 years * Hospitalization in the Intensive Care Unit (ICU) * Requirement for vasoactive drugs (minimum norepinephrine equivalent dose \>0.1μg/kg / min ) * Mechanical ventilation via an endotracheal tube Exclusion Criteria: * Head and craniofacial trauma * Pregnancy * Intensive fluid therapy (\>200ml/h) * Changes in vasoactive drug dosages within 30 minutes prior to study inclusion * Hypothermia (body temperature \<35.5 oC) * Fever (body temperature \>38.5oC)