Updated July 2026 · 11 min read
Part of the ICU Devices Hub — browse every related guide in one place.
The Swan-Ganz catheter is used far less than it once was, but when a patient with cardiogenic shock or mixed, unclear hemodynamics has one, it becomes the most information-dense line in the room. Understand what each port measures and how the waveform changes as it passes through the heart, and a PA catheter turns confusing shock into a set of numbers you can act on.
| Measurement | Normal | What it tells you |
|---|---|---|
| CVP / right atrial pressure | 2 – 6 mmHg | Right-heart preload / volume status |
| PA systolic / diastolic | 15–25 / 8–15 mmHg | Pulmonary artery pressure (right afterload, PA hypertension) |
| PA occlusion (wedge, PAOP/PCWP) | 6 – 12 mmHg | Estimate of left atrial / LV filling pressure (left preload) |
| Cardiac output (CO) | 4 – 8 L/min | Total forward flow |
| Cardiac index (CI) | 2.5 – 4.0 L/min/m² | CO indexed to body size — the more useful number |
| SVR | 800 – 1200 dyn·s/cm&sup5; | Systemic afterload / "tone" — high in cold shock, low in warm/septic shock |
| SvO2 (mixed venous) | 60 – 80% | Balance of oxygen delivery vs consumption |
One of the most useful skills is recognizing where the tip is by its waveform, because the pressures change character in each chamber:
| Location | Waveform |
|---|---|
| Right atrium | Low, small a/c/v waves (~2–6 mmHg) |
| Right ventricle | Sharp rise, steep drop, low diastolic near zero (~25/0–5) — watch for ectopy here |
| Pulmonary artery | Systolic similar to RV but with a higher diastolic and a dicrotic notch (~25/10) |
| Wedge (balloon up) | Damped, low tracing with a/v waves (~6–12) — the balloon has occluded a branch |
To "wedge," you inflate the balloon and let the catheter float forward until it occludes a small PA branch; the tip then reads a pressure that reflects the left atrium through the pulmonary capillaries. It's useful, but it carries the catheter's single most feared complication, so:
The reason a PA catheter earns its risk is that CO and SVR together sort the shock states that look similar at the bedside:
| Shock type | CO / CI | SVR | Wedge (preload) |
|---|---|---|---|
| Hypovolemic | Low | High | Low |
| Cardiogenic | Low | High | High |
| Septic / distributive | High (or normal) | Low | Low/normal |
| Obstructive (e.g., tamponade, massive PE) | Low | High | Varies (equalized pressures in tamponade) |
That single table is the whole argument for the line: a cold, clamped-down, low-output heart (cardiogenic) needs a completely different plan than a warm, wide-open, high-output vasodilated patient (septic), and their blood pressures can look identical.
Mixed venous oxygen saturation is a real-time gauge of whether oxygen delivery is keeping up with demand. A falling SvO2 means the tissues are extracting more because delivery is dropping (low CO, anemia, hypoxemia) or demand is surging (fever, shivering, agitation). A high SvO2 can mean the tissues can't use the oxygen (severe sepsis) or a wedged/contaminated sample. Trend it — it often moves before the pressures do.
A PA catheter isn't routine anymore, and that's the point: when one is in, the patient is complex enough that the numbers matter. Know the normals, read the tip by its waveform, wedge gently and briefly, and let CO and SVR name the shock. Above all, protect the patient from the wedge — a balloon that stays up is the fastest way this line turns from tool to injury.
This article is general educational information for licensed clinicians and students, not medical advice or a substitute for your institution's protocols or a provider's orders. Always follow facility policy.
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