A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia.

Respiratory failure causes an altered state of consciousness due to ischemia in the brain.

[citation needed] Below is a diagram that provides a general overview of the 4 types of respiratory failure, their distinguishing characteristics, and major causes of each.Type 1 respiratory failure is characterized by a low level of oxygen in the blood (hypoxemia) (PaO2) < 60 mmHg with a normal (normocapnia) or low (hypocapnia) level of carbon dioxide (PaCO2) in the blood.

After general anesthesia, decreases in functional residual capacity leads to collapse of dependent lung units.

[1] Type 4 respiratory failure occurs when metabolic (oxygen) demands exceed what the cardiopulmonary system can provide.

For instance, if respiratory failure is caused by cardiogenic shock (decreased perfusion due to heart dysfunction, symptoms of heart dysfunction (e.g., pitting edema) are also expected.Arterial blood gas (ABG) assessment is considered the gold standard diagnostic test for establishing a diagnosis of respiratory failure.

The treatment of acute respiratory failure may involve medication such as bronchodilators (for airways disease),[7][8] antibiotics (for infections), glucocorticoids (for numerous causes), diuretics (for pulmonary oedema), amongst others.

[14] Lack of oxygen response may indicate other modalities such as heated humidified high-flow therapy, continuous positive airway pressure or (if severe) endotracheal intubation and mechanical ventilation.

[citation needed] Type 2 respiratory failure often requires non-invasive ventilation (NIV) unless medical therapy can improve the situation.