Despite of preventive measures, the incidence of deep venous thrombosis (DVT) in ICU patients is estimated to range from 5-31%. While clinical diagnostics is unreliable, ultrasound compression test (UCT) has proven to be a highly sensitive and specific modality for the recognition of lower extremity DVT. Delegating this competence to ICU nurses can increase UCT availability and enable preventive DVT screening. Therefore, the investigators decided to conduct a clinical study to evaluate the sensitivity and specificity of UCT performed by general ICU nurse in ICU patients compared to an investigation by ICU physician certified in ultrasound. Prior to the study, each nurse-investigator participating in the study undergo one-hour training in UCT and examine 5 patients under supervision. Then, ICU patients without known DVT will be investigated by UCT in the femoral and popliteal region of both lower extremities by trained general ICU nurse-investigators. On the same day, the examination will be repeated by an ICU physician-investigator. The results of the examinations of each patient will be blinded to each other for both investigators until both tests are performed. The sensitivity and specificity of the test performed by general nurse will be calculated in comparison with the examination by a specialist.

Inclusion Criteria:

• all ICU patients without known deep venous thrombosis, hospitalised more than 72 hours

Exclusion Criteria:

• contraindication of compression ultrasound testing
• end-of-life decision regimen of care

ICU patients