Bedside assessment of intravascular volume status in critically ill patients is challenging. Fluid management impacts systemic perfusion and may influence the risk of organ failure and mortality. Clinicians often use invasive hemodynamic monitoring as an adjunct to information gathered from the physical examination and laboratory evaluation to arrive at a fluid management strategy. A non-invasive and economical technique like ultrasound in the ICU helps to approach regarding hemodynamic status and treatment of the critically ill patients. The physiologic principle  underlying IVC collapsibility index is that during spontaneous breathing, inspiration leads to negative intrathoracic pressure, which in turn leads to three additional effects. Collapsibility of the inferior vena cava has been found to be useful in monitoring response to therapy as well as assisting in ongoing resuscitation by providing means to measure CVP non-invasively.

Informed consent will be obtained from all the patients, and they will be assured that the identity of the respondents will be kept anonymous. 

Before collection of USG data, study ultra-sonographers will be blinded to CVP monitoring. Bedside ultrasound images will be obtained in a systematic fashion with the patient supine to determine the dimensions and collapsibility of the IVC. 

Immediately following the ultrasound image acquisition, study personnel will obtain a simultaneous recording of the CVP waveform from the distal lumen of the central venous catheter . The CVP will be uniformly measured from a recording at end expiration with the patient supine and the pressure transducer having been zeroed at the mid-thoracic position. A patient with CVP of less than 8 cmH₂O will be considered as hypovolemic. The patients with CVP between 8–12 cmH₂O will be considered as euvolemic and patients having CVP > 12 cmH₂O will be considered as hypervolemic.

Statistical Analysis will be performed using standard statistical methods.