Artificial Intelligence or Human Hand? Evaluating Inferior Vena Cava Imaging for Hydration Status

Inclusion Criteria: * Healthy adults aged 18 years or older, 50% biological women Exclusion Criteria: * Pregnant or lactating women * History of thrombosis of the inferior vena cava * Major cardiovascular event in the last 3 months * History of peripheral arterial disease of the legs * History of heart failure of any grade * History of atrial fibrillation or atrial flutter * History of severe valvular disease * History of renal failure * History of liver cirrhosis * History of chronic obstructive lung disease (COPD), chronic bronchitis, pulmonary emphysema * History of diabetes mellitus * History of arginine-vasopressin (AVP) disturbance * Abdominal surgery within the last 3 month * Volume loss (diarrhoea, vomiting, or bleeding) within the past 3 days * Respiratory distress of any grade * Any diuretic therapy, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) * Inability to follow procedures or insufficient proficiency in the study language * Inability to provide informed consent * Vital signs outside normal limits: tachycardia \>100 bpm, systolic blood pressure \<85 mmHg, or SpO2 \< 92% * Employees or colleagues in a direct supervisory, subordinate, or collaborative relationship with the study team