Short answers, pulled from the story.
Respiratory failure is a state of inadequate gas exchange where the body's oxygen and carbon dioxide exchange ceases to function. This condition occurs when arterial oxygen drops below 80 mmHg or carbon dioxide rises above 45 mmHg.
Type 1 respiratory failure is defined by blood oxygen levels falling below 60 mmHg while carbon dioxide levels remain normal or drop too low. This type of failure occurs when oxygen cannot cross from air sacs into the bloodstream or when blood bypasses the oxygenation process through a right-to-left shunt.
Type 2 respiratory failure causes hypercapnia which drives blood pH below 7.35. This form of failure occurs due to increased airway resistance from chronic obstructive pulmonary disease or asthma, or when breathing muscles are paralyzed by neuromuscular diseases like Guillain Barré syndrome.
Type 3 respiratory failure is also known as peri-operative respiratory failure and emerges as a specific subset of Type 1 failure tied to the operating room. This condition occurs frequently after general anesthesia when the administration of anesthesia reduces the functional residual capacity of the lungs causing dependent lung units to collapse.
Type 4 respiratory failure is a metabolic crisis where the body's demand for oxygen exceeds the capacity of the cardiopulmonary system to provide it. This type of failure is frequently seen in cases of cardiogenic shock or hypovolemic shock where the heart's inability to pump blood effectively leads to pulmonary edema.
The diagnosis of respiratory failure requires arterial blood gas assessment which measures the partial pressure of oxygen and carbon dioxide in the blood. Alternative methods such as capnometry and pulse oximetry serve as supporting tools while imaging techniques including ultrasonography and radiography determine the underlying cause.