Special Operations Forces Medical Handbook

4-23

Respiratory: Pulmonary Embolus

COL Warren Whitlock, MC, USA

Introduction: A pulmonary embolism (PE) is an obstruction of the lung’s arterial circulation. It usually occurs
when a thrombus (blood clot) in the deep venous system of the legs dislodges and travels to the lung, causing
a loss of oxygenation of the blood owing to that area of the lung (hypoxemia). PE presents as three different
syndromes: embolism without infarction (most common and causing acute unexplained dyspnea until clot is
lysed), pulmonary infarction (complete obstruction of a distal branch of the pulmonary arterial circulation) or
acute cor pulmonale (a massive clot obstructing a majority of both the pulmonary arteries and right ventricle
of the heart, causing right heart failure).

Subjective: Symptoms
Three different clinical presentations are possible, depending on which PE syndrome is present.

1. Embolism: Acute unexplained shortness of breath without other significant symptoms.


2. Infarction: Chest pain associated with labored breathing, anxiety, occasional low-grade fever and cough
   (possibly with bloody sputum) for which no other cause (chest trauma, pneumonia, angina, etc.) can
   be determined.


3. Massive PE: Patients that have risk factors for venous thromboembolism (sedentary, post-surgical,
   obese, elderly or infected patients or those with a blood disorder) and have sudden, unexplained loss of
   consciousness.
   Focused History: Did the shortness of breath start suddenly? (PE is an acute condition. Symptoms may
   progress over several days, but it starts suddenly.) Do you feel anxious? (A sense of foreboding or anxiety
   without clear reason is common.) Have you had any recent lower extremity or pelvic injury? (PE is usually
   associated with stasis or an injury to a great vein.) Did you strain with a bowel movement before the symptoms
   began? (Straining can dislodge lower abdominal clot.) Have you had blood clots before? (may be prone to
   form clots—hypercoaguable) Have you recently become active after a time of bedrest? (PE typical after 2-3
   days bedrest)

Objective: Signs
Using Basic Tools: Vital Signs: Low-grade fever if any (< 101°F), respiratory rate >18, resting pulse
over 90 BPM
Inspection: Cyanosis, hypotension and distended neck veins may indicate massive PE; anxiety, dyspnea
and splinted breathing (due to pleuritic chest pain) is typical; peripheral edema suggests source of emboli
or right heart failure
Auscultation: Area of rales or absent breath sounds may indicate location of an infarct or large PE. S3
gallop may indicate PE or CHF. Distant heart sounds with tamponade. Rub suggests pericarditis or pleural
effusion.
Using Advanced Tools: EKG: To rule out other diagnoses including pericarditis or MI; CXR: low infiltrates
suggest infarction, massive PEs cause “pruning” of the lung blood vessels

Assessment:
Differential Diagnosis
Embolism without infarction - anxiety attack or hysteria (dyspnea not typical, although tachypnea may be).
Infarction - septic shock (hypotension and altered mental status typical), MI (typical history and EKG changes),
tamponade (distant heart sounds, elevated neck veins, hypotension)
Massive PE - pneumonia (toxic appearance with auscultory and CXR ndings—see Pneumonia section),
atelectasis (increased density [whitening] in wedge of lung on CXR—see discussion in Pneumonia Section);
congestive heart failure (peripheral edema, orthopnea and other ndings—see Cardiac: CHF); pericarditis
(typical chest pain with EKG ndings and possible pericardial rub)