Categories: Respirology/ ICU

Hypoxia and pulmonary embolism (PE): Mechanism

The clot CAUSES Dead space; which does not cause hypoxia/hypoxemia on its own.
ALWAYS ASK ABOUT: 
  1. Resp Rate (PE creates dead space, reduced alveolar ventilation, CO2 increases and patient attempts to blow off CO2)
  2. Blood pressure (?Obstructive shock from large saddle PE)
  3. Tachycardia (Left heart trying to increase cardiac output because stroke volume low) 
Mechanisms by which a PE might cause Hypoxia/Hypoxemia:
  1. Significant V/Q Mismatch (though usually dead space ventilation, but impaired pulmonary oxygen transfer can occur due to vascular re-distribution and release of vaso-active inflammatory molecules such as: serotonin, histamine, prostaglandins, bradykinin etc.)
  2. Pain -> Splinting and atelectasis [caused by loss of surfactant and alveolar hemorrhage]
  3. Inflammation causing infarction [however may be a matched defect] +/- superimposed pneumonia 
  4. Increased pulmonary vascular resistance; potentiating right heart strain and cardiac stunting if (i.e PFO)

REFERENCES

  1. Huet Y, Lemaire F, Brun-Buisson C, Knaus WA, Teisseire B, Payen D, Mathieu D. Hypoxemia in acute pulmonary embolism. Chest. 1985 Dec;88(6):829-36.
  2. Santolicandro A, Prediletto R, Fornai E, Formichi B, Begliomini E, Giannella-Neto A, Giuntini C. Mechanisms of hypoxemia and hypocapnia in pulmonary embolism. Am J Respir Crit Care Med. 1995 Jul;152(1):336-47.
  3. Torbicki A, Perrier A, Konstantinides S, Agnelli G, Galiè N, Pruszczyk P, Bengel F, Brady AJ, Ferreira D, Janssens U, Klepetko W, Mayer E, Remy-Jardin M, Bassand JP. Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC). Eur Heart J. 2008 Sep;29(18):2276-315. 
Get Medical Pearls directly to your inbox every week!
Weekly posts with high yield medical knowledge, directly to your mailbox!
Dr. C Humphreys

Internal Medicine

Share
Published by
Dr. C Humphreys

Recent Posts

Nocturia and OSA: Mechanism

Nocturia is a common symptom associated with obstructive sleep apnea. [1] Img Cred: Am J…

5 months ago

ASD vs. VSD Murmur Difference

ASD (Atrial Septal Defect) Wide, Fixed split S2 (in contrast to the normal variation in…

5 months ago

Mechanism of a Mixed Apnea

Mixed apneas are characterized by absent respiratory effort and airflow in the first section of…

1 year ago

How Does Hypothyroidism Cause Hypoventilation?

Although rare, the differential diagnosis of hypoventilation and hypercapnia respiratory failure includes hypothyroidism. It is…

1 year ago

Why is Pro-BNP/ BNP lower in Obesity?

B-type natriuretic peptide (BNP) is a hormone created in response to cardiac wall stretch due…

2 years ago

What is Peribronchovascular Distribution on CT imaging?

A common finding described on computed tomography (CT) imaging. A disease with a peribronchovascular distribution…

2 years ago

This website uses cookies.