🏠 Study Hub 🖼️ Infographics
Nursing Field Notes / Respiratory · Med-Surg Course

Pulmonary Embolism 🫁

A clot in the lung · sudden dyspnea · the one you anticoagulate

NG-394 Respiratory ADHD-friendly visual edition

A clot travels from a leg vein, wedges in a pulmonary artery, and that part of the lung is ventilated but no longer perfused. The presentation is sudden — that suddenness is the whole clue.

The classic threeSudden dyspnea, pleuritic chest pain, tachycardia
Where it came fromA DVT in the leg, 90% of the time
The gas patternLow O₂ AND low CO₂ — she is blowing off CO₂
PositionHigh Fowler’s, oxygen, then call

🧨 What starts it

The route a clot takes from a leg vein up through the right heart into a pulmonary artery, and two lung segments compared - a normal one and the blocked one that still gets air but no blood, which is dead space.
Air arrives and blood does not. Once you can see the segment that is ventilated but not perfused, the low oxygen with low carbon dioxide stops being a puzzle. Swipe it sideways if it is cut off, or tap to open it full size.
How a leg clot becomes a lung emergency
  • A thrombus forms in a deep vein — Virchow’s triad: stasis, endothelial injury, hypercoagulability.
  • It breaks loose, travels up the vena cava, through the right heart, and wedges in a pulmonary artery.
  • That lung segment still gets air but no blood — dead space. Gas exchange stops there.
  • The right ventricle now pumps against a blocked bed. A large clot causes right heart strain, then obstructive shock.
Who gets one
  • Immobility — surgery, long flights, bed rest
  • Recent orthopedic surgery, especially hip and knee
  • Cancer, pregnancy, estrogen-containing contraception
  • Obesity, smoking, previous DVT or PE
  • Fractures of long bones — think fat embolism too
The one that is not a clot

A fat embolism follows a long-bone fracture and brings petechiae across the chest and axillae plus confusion. An amniotic fluid embolism happens during labor. Same obstruction, different source.

🔎 What you will see

What she looks like
  • Sudden shortness of breath — the commonest sign, and the word that matters.
  • Pleuritic chest pain — sharp, worse on inspiration.
  • Tachycardia and tachypnoea, anxiety, a sense of impending doom.
  • Cough, sometimes hemoptysis.
  • Low-grade fever. Hypotension means it is massive.
  • Check the legs: unilateral swelling, warmth, a hard cord.
What the tests show
  • ABG: low PaO₂ and low PaCO₂ — she is hyperventilating. Respiratory alkalosis first.
  • D-dimer: rules PE out when normal. A high one proves nothing.
  • CT pulmonary angiography is the gold standard.
  • V/Q scan if contrast or the kidneys are a problem.
  • ECG: sinus tachycardia is commonest. S1Q3T3 is famous and rare.
The trap

An oxygen saturation that is still normal does not rule it out early on. Sudden dyspnea in someone with a risk factor is enough to escalate.

🩺 What you do

What you do, in order
  1. Stay with her. High Fowler’s — sitting up drops the work of breathing.
  2. Oxygen straight away, titrated to keep the saturation up.
  3. Call the provider / rapid response. This is a stat call.
  4. IV access, continuous pulse oximetry and cardiac monitoring.
  5. Prepare for anticoagulation and get her to CT.

Notice that oxygen and position come before the phone. Airway and breathing first.

The drugs
  • Heparin IV — monitor aPTT; antidote is protamine sulfate.
  • Enoxaparin subcut — no routine monitoring.
  • Warfarin long term — monitor INR, target 2 to 3; antidote is vitamin K.
  • DOACs (apixaban, rivaroxaban) — no routine monitoring, fewer interactions.
  • Alteplase for a massive PE with shock. Bleeding is the risk.
Preventing the next one
  • Early ambulation after surgery is the single best measure.
  • Sequential compression devices and prophylactic anticoagulation.
  • Never massage a leg that is swollen and painful — that is how a clot is dislodged.
  • On warfarin: keep vitamin K intake consistent, not absent. Green vegetables are fine as long as the amount does not swing.
  • Soft toothbrush, electric razor, report black stools or bleeding gums.
  • An IVC filter is for people who cannot be anticoagulated.

⚡ Quick recall

The classic threeSudden dyspnea, pleuritic chest pain, tachycardia
Where it came fromA DVT in the leg, 90% of the time
The gas patternLow O₂ AND low CO₂ — she is blowing off CO₂
PositionHigh Fowler’s, oxygen, then call
Sudden dyspnea after hip surgery — what is it until proven otherwise?
A pulmonary embolism. Sit her up, oxygen on, call.
What does the ABG show early?
Low oxygen and low carbon dioxide — respiratory alkalosis from hyperventilating.
What is a normal D-dimer good for?
Ruling PE out. A raised one is non-specific and proves nothing on its own.
Which anticoagulant goes with aPTT, and which with INR?
Heparin with aPTT. Warfarin with INR.
The leg is swollen and painful. What must you not do?
Do not massage it. That can send the clot to the lung.