Posts Tagged ‘hypoxia in acute pulmonary embolism’

Hypoxia is most important feature of acute pulmonary embolism.

It occurs due to variety of mechanisms

  1. Ventilation perfusion mismatch is the major  mechanism  ( Normal ventilation /Reduced perfusion)
  2. Atelectasis of lung  ( Left to right shunt)
  3. Loss of lung volume due to pulmonary infarct  contribute later
  4. Low mixed venous Oxygen saturation  (Tissue hypoxia -more extraction )
  5. One more important cause is right to left shunting  across PFO  due to sudden elevation of right atrial mean pressure reflected from RVEDP .

Can  acute pulmonary embolism be diagnosed  with out Hypoxia ?

Surprisingly many standard text books mention hypoxia is a soft sign . In fact , Braunwald’s  text book of cardiology  do mention about it .

Significant acute pulmonary embolism can not occur without affecting o2 saturation .

However , it is possible sub acute  pulmonary embolism could occur with normal oxygen saturation.

Final message

Hypoxia is indeed a hard sign  for most events  of major pulmonary embolism . It can even be termed as an essential criteria .A hypoxic , tachypenic patient in  sinus tachycardia with echo evidence of  new onset RA or RV dilatation is almost 100 % specific for acute pulmonary embolism . ( This becomes 200 % if he or she has DVT as well !)

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