# Critical care terminology and unit conventions

> **Educational work by a pre-medical student — not medical advice.** Not a clinical protocol, prescription, or patient handout, and not for patient care. See [DISCLAIMER](../DISCLAIMER.md).

Revised 27 October 2026. This concise glossary replaces the earlier expanded list where shorthand could be mistaken for a diagnostic or treatment rule.

| Term | Educational meaning and limit |
|---|---|
| CO / CI | Cardiac output / output indexed to body surface area; measurement method matters |
| MAP / RAP / CVP | Mean arterial / right atrial / central venous pressure; filling pressures are not stand-alone fluid tests |
| SVR | Systemic vascular resistance; specify units and the pressure/flow calculation |
| EF | Ejection fraction; loading-dependent and not a complete measure of perfusion or intrinsic contractility |
| CaO2 / DO2 | Arterial oxygen content / systemic oxygen delivery; see the linked formulas |
| ScvO2 / SvO2 | Central / mixed venous oxygen saturation; sampling locations differ and values are not interchangeable |
| IVC | Inferior vena cava; its appearance depends on ventilation and cardiovascular context |
| AKI / RRT / CRRT | Acute kidney injury / renal replacement therapy / continuous therapy; none follows automatically from a creatinine value |
| ARDS / P:F | A clinical syndrome / arterial oxygen tension divided by inspired oxygen fraction; all diagnostic criteria matter |
| PBW | Predicted body weight, distinct from actual body weight |
| PEEP / Pplat / DP | End-expiratory / plateau / driving pressure; interpret measurement conditions and total PEEP |
| NIV / HFNC / SBT | Non-invasive ventilation / high-flow nasal cannula / spontaneous breathing trial; they refer to different support contexts |
| ICP / CPP | Intracranial / cerebral perfusion pressure; the simplified relationship is not a universal target |
| VA / VV ECMO | Venoarterial / venovenous extracorporeal support; mode and configuration determine interpretation |
| LVAD / PI | Left ventricular assist device / pulsatility index; displayed values are device/context dependent |
| RASS | Richmond Agitation-Sedation Scale; a score is not an analgesia or amnesia guarantee |
| DNR / DNI | Limits on resuscitation / intubation as documented; neither alone means comfort-only care |

See [physiology formulas](../references/icu_physiology_notes.md), [source guide](../references/bibliography.md) and [case exercises](../README.md). No copyrighted clinical scale items or questionnaire forms are reproduced.