Type 1 Type 1<unk>  is defined as a low level of oxygen in the blood (hypoxemia) with either a standard (normocapnia) or low (hypocapnia) level of carbon dioxide (PaCO2) but not an increased level (hypercapnia). It is typically caused by a ventilation/perfusion (V/Q) mismatch; the volume of air flowing in and out of the lungs is not matched with the flow of blood to the lungs. The fundamental defect in type 1<unk>  is a failure of oxygenation characterized by: ::: PaO2 decreased (aCO2 normal or decreased (A-aO2 increased This type of<unk>  is caused by conditions that affect oxygenation, such as: * Low ambient oxygen (e.g. at high altitude) * Ventilation-perfusion mismatch (parts of the lung receive oxygen but not enough blood to absorb it, e.g. pulmonary embolism) * Alveolar hypoventilation (decreased minute volume due to reduced<unk>  muscle activity, e.g. in acute neuromuscular disease); this form can also cause type 2<unk>  if severe. * Diffusion problem (oxygen cannot enter the capillaries due to parenchymal disease, e.g. in pneumonia or ARDS) * Shunt (oxygenated blood mixes with non-oxygenated blood from the venous system, e.g. right to left shunt) Type 2 Hypoxemia (PaO2 2 >6.0kPa). The basic defect in type 2<unk>  is characterized by: ::: PaO2 decreased (aCO2 increased (> ) PA-aO2 normal pH aCO2) that has been generated by the body but cannot be eliminated. The underlying causes include: * Increased airways resistance (chronic obstructive pulmonary disease, asthma, suffocation) * Reduced breathing effort (drug effects, brain stem lesion, extreme obesity) * A decrease in the area of the lung available for gas exchange (such as in chronic bronchitis) * Neuromuscular problems (Guillain–Barré syndrome, motor neuron disease) * Deformed (kyphoscoliosis), rigid (ankylosing spondylitis), or flail chest. Type 3<unk> : This form of<unk>  results from lung atelectasis. Because atelectasis occurs so commonly in the perioperative period, this form is also called perioperative<unk> . After general anesthesia, decreases in functional residual capacity leads to collapse of dependent lung units. Type 4<unk> : This form results from hypoperfusion of<unk>  muscles as in patients in shock. Patients in shock often experience<unk>  distress due to pulmonary edema (e.g., in cardiogenic shock). Lactic acidosis and anemia can also result in type 4<unk> . However, type 1 and 2 are the most widely accepted.
Respiratory failure
Respiratory compromise
Pulmonary toxicity
Liver failure
Sleep paralysis
Pulmonary insufficiency
Neurotoxicity
Sedation