*4.1.1 Acute hypoxemic respiratory failure*

Main component is The alveolar–arterial oxygen gradient = PAO2 – PaO2. The normal value is between 10 and 15 mm Hg and is influenced by age, i.e. increases by approximately 3 mm Hg every decade after the age of 30 years. For an FiO2 = 21%, it should be 5 to 25 mm Hg and for an FiO2 = 100%, it should be <150 mm Hg. Hypoxemic respiratory failure with a widened alveolar–arterial oxygen gradient is caused by V/Q mismatching or shunt pathophysiology. Hypoxemia due to V/Q mismatch improves with supplemental oxygen, while no improvement in cases with shunt.

Disease which result in the flooding of airspace, complete or partial collapse of the lung, pulmonary vascular abnormalities or airway disease are the common source of hypoxemic respiratory failure.

Principles for managing the patients suffering from hypoxemic respiratory failure mainly include:-

