Hypoxemia

Nota:

• - drop in ventilation -depression of resp. centre in brain -airway obstruction -disease of nerves supplying resp. muscles -thoracic wall injury

Nota:

• -most common -blood passes thru pulmonary system without being involved in gas exchange--> unoxygenated blood reenters arterial system & dilutes oxygenated blood -atelectasis, consolidated pneumonia

Nota:

• -pathological changes--> poor O2 transfer into arterial blood -Fick's Law: surface area            -membrane thickness             -Gas solubility- CO2 vs. O2            -pressure gradient

1. High V/Q mismatch= dead space

   Nota:

   • -No blood supply -Ventilation exceeds perfusion -Pulmonary embolism, cardiac failure
2. Low V/Q mismatch: shunt

   Nota:

   • -Perfusion exceeds ventilation -blood passing unventilated alveoli--> doxygenated blood entering arterial system -atelectasis (collapsed alveoli), pneumonia (consolidated alveoli). asthma (fluid filled alveoli)