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

Recent Posts

Trapped Lung vs. Lung Entrapment

Though often used synonymously; Trapped Lung and Lung Entrapment technically describe separate entities along the…

5 months ago

Cause of Pericardial Effusion in Pulmonary Hypertension: Pathogenesis

It is not clearly understood why patients with pulmonary hypertension (PH) develop pericardial effusions. However,…

6 months ago

Difference between Mycophenolate Mofetil vs. Mycophenolate Sodium

The two drugs are not interchangeable nor dose equivalents. Mycophenolate mofetil (Cellcept) is a semi…

7 months ago

What is an “Anephric” Creatinine Rise?

Serum Creatinine can be a deceptive surrogate during an acute kidney injury. It may lag…

1 year ago

Macrophage activation syndrome vs. Hemophagocytic lymphohistiocytosis

Macrophage activation syndrome (MAS) is a life-threatening complication of rheumatic diseases (i.e SLE, Juvenile idiopathic…

2 years ago

When does a Tracheostomy mature?

After creation of a percutaneous tracheotomy site for prolonged ventilation, one of the immediate complications…

2 years ago

This website uses cookies.