Table 1

Specific research questions with add-on measurements53

Short titleResearch questions
Basic studyWhich combination of clinical variables obtainable through physical examination is associated with cardiac output measured by critical care ultrasonography (CCUS)53?
Which combination of clinical and haemodynamic variables is associated with 7-day, 30-day and 90-day mortality?
1. NIRSWhat is the association of clinical and haemodynamic variables and tissue (muscle) oxygen saturation (StO2) measured by near-infrared spectroscopy (NIRS)?
Does the kneecap NIRS measurement have a better association with the clinical and haemodynamic variables than the NIRS measurement at the thenar muscle?
2. Pulmonary ultrasoundWhat is the association of a B-profile* measured with pulmonary ultrasonography and auscultation for pulmonary crackles with the diagnosis of pulmonary oedema by chest radiograph?
Is there a difference in cardiac output between the group with and without the presence of a B-profile?
3. PEEP-challengeDoes an increase in positive end-expiratory pressure (PEEP) correlate with a decrease in cardiac output?
4. RV-function + mortalityWhat is the association between right ventricular (RV)-function assessed with tricuspid annular plane systolic excursion and peak tissue Doppler systolic velocity in the tricuspid annulus (RV S’) with 90-day mortality?
What is the association between RV-function and clinical variables obtained from through physical examination?
5. Abdominal flowIs there a correlation between cardiac output and peripheral blood flow measured with CCUS?
Can we calculate a proxy for abdominal organ blood flow by subtraction of peripheral flow to head and extremities from the cardiac output?
6. FloTrac†What is the level of agreement between cardiac output measured by the FloTrac compared with cardiac output measured with CCUS?
Do the levels of agreement change when factors that might influence FloTrac measurements are present?
7. Repeated measuresWhat is the association of clinical variables with the cardiac output measured on two different time-points: one within the first 24 hours of admission and a second 24 hours thereafter
8. RV-function + AKIIs RV volume overload measured by tricuspid insufficiency and RV diameter associated with acute kidney injury (AKI) ?
9. Fluid responsivenessDo variations in end-tidal carbon dioxide (EtCO2), heart rate and blood pressure induced by the passive leg raising (PLR) test predict fluid responsiveness?
Does a PLR test without lowering the head of the bed have a similar accuracy compared with the standard PLR test?
Will a temporary increase of PEEP lead to a greater decrease in cardiac output in fluid responders compared with non-responders?
10. ARDSWhat is the association between CCUS measurements and the presence or development of acute respiratory distress syndrome (ARDS) during the first 24 hours of ICU stay?
11. Myocardial strainIs left ventricular and RV myocardial strain measured with tissue Doppler imaging a predictor of 90-day mortality?
What is the association betweenmyocardial strain measured with tissue Doppler imaging and conventional CCUS measurements?
  • *B-profile: A B-profile is a strong indicator of pulmonary oedema and is present when three or more B lines are seen in at least three of the six BLUE points, or in two of the four lower BLUE points.54

  • †FloTrac: the FloTrac (Edwards Lifesciences, Irvine, California, USA) is a pulse contour technique that analyses the arterial pressure waveform to compute stroke volume and cardiac output. The technique consists a dedicated pressure sensor (FloTrac) and a monitor to compute stroke volume and cardiac output (Vigileo).55