Collapsibility (CI-IVC), distensibility (dIVC) and delta (ΔIVC) indices, which are dynamic measures of inferior vena cava (IVC) diameter, are used to assess the intravascular volume status in critically ill patients. Positive pressure support (PS) has been shown to induce IVC diameter distention by increasing intrathoracic pressure, and high positive expiratory pressure (PEEP) decreases the CI-IVC percentage (4). During Triggered positive pressure support it is necessary to clarify which IVC index is valid for measuring the volume status.it is aimed to compare the IVC indexes (CI-IVC, DIVC, ΔIVC), positive rate of change with pressure, correlation with central venous pressure and accurate prediction of volume status in patients with different positive pressure support.

The IVC diameters at different pressure supports were measured by the same clinician after obtaining a clear image of where the US and IVC measurements were made and the probe stabilization was achieved. He performed the procedure of changing the pressure supports, a blind independent intensive care physician without working, and recorded the applied pressure supports respectively. The different pressure supports applied are as follows:

1. PS 10 mmHg-PEEP 5 mmHg,
2. PS 0 mmHg- PEEP 5 mmHg
3. PS 10 mmHg- PEEP 0 mmHg.
4. T-tube (PS 0 mmHg-PEEP 0 mmHg)

Inclusion Criteria:

• Age>18 years
• Current use of mechanical ventilation through an endotracheal tube.

Exclusion Criteria:

• Profound Hypoxia defined as a fraction of inspired oxygen requirement >90% or a PEEP >10 mmHg
• Patient-ventilator desynchrony or active agitation
• Unstable O2 requirement
• Cardiovascular instability
• Current PEEP requirements of >10 mmHg
• Current oxygen saturation (SpO2) of <88%.
• High intra abdominal pressure
• Right cardiac failure
• Morbid obesity

Inpatient sample