Overview
The IVC schematic reflects right atrial pressure, remodeling and breathing. In spontaneous breathing, it ranges from a small collapsible vein to a dilated vein with poor sniff collapse. Sniff previews the modeled maximal inspiratory change.
NIPPV and intubation use positive-pressure variation instead of spontaneous-sniff rules. PEEP can increase measured pressure and IVC size without increasing true preload; the graphic is not a fluid-responsiveness measurement.
The compact JVP column gradually changes from blue to crimson as RAP rises; colour is an illustrative cue. Its fixed 0–10 cm H₂O display makes elevated heights easier to see. Above 10, the column stays full with a 10+ marker; the numerical reading still shows the actual height. The display limit is not a clinical cutoff. It approximates height above the sternal angle as RAP × 1.36 − 5 cm, floored at zero. The anatomical offset varies with posture and body habitus. ASE 2025 right-heart guidance and Seth et al. are in Works cited.