Respiratory failure

Respiratory failure
Classification and external resources
Specialty Pulmonology, Intensive care medicine
ICD-10 J96
ICD-9-CM 518.81
DiseasesDB 6623
eMedicine med/2011
MeSH D012131

Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide or both cannot be kept at normal levels. A drop in the oxygen carried in blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type I or Type II, based on whether there is a high carbon dioxide level. The definition of respiratory failure in clinical trials usually includes increased respiratory rate, abnormal blood gases (hypoxemia, hypercapnia, or both), and evidence of increased work of breathing.[1]

The normal partial pressure reference values are: oxygen PaO2 more than 80 mmHg (11 kPa), and carbon dioxide PaCO2 lesser than 45 mmHg (6.0 kPa).

Types

Type 1

Type 1 respiratory failure is defined as a low level of oxygen in the blood (hypoxemia) without an increased level of carbon dioxide in the blood (hypercapnia), and indeed the PaCO2 may be normal or low. 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 basic defect in type 1 respiratory failure is failure of oxygenation characterized by:

PaO2 decreased (< 60 mmHg (8.0 kPa))
PaCO2 normal or decreased (<50 mmHg (6.7 kPa))
PA-aO2 increased

This type of respiratory failure is caused by conditions that affect oxygenation such as:

Type 2

Hypoxemia (PaO2 <8kPa) with hypercapnia (PaCO2 >6.0kPa).

The basic defect in type 2 respiratory failure is characterized by:

PaO2 decreased (< 60 mmHg (8.0 kPa))
PaCO2 increased (> 50 mmHg (6.7 kPa))
PA-aO2 normal
pH decreased

Type 2 respiratory failure is caused by inadequate alveolar ventilation; both oxygen and carbon dioxide are affected. Defined as the buildup of carbon dioxide levels (PaCO2) that has been generated by the body but cannot be eliminated. The underlying causes include:

Treatment

Mechanical ventilator

Treatment of the underlying cause is required. Endotracheal intubation and mechanical ventilation are required in cases of severe respiratory failure (PaO2 less than 50 mmHg). Respiratory stimulants such as doxapram are rarely used, and if the respiratory failure resulted from an overdose of sedative drugs such as opioids or benzodiazepines, then the appropriate antidote (naloxone or flumazenil, respectively) will be given.

There is tentative evidence that in those with respiratory failure identified before arrival in hospital, continuous positive airway pressure can be useful when started before conveying to hospital.[3]

See also

References

  1. Tulaimat, A; Patel, A; Wisniewski, M; Gueret, R (August 2016). "The validity and reliability of the clinical assessment of increased work of breathing in acutely ill patients.". Journal of critical care. 34: 111–5. PMID 27288621. doi:10.1016/j.jcrc.2016.04.013.
  2. 1 2 Burt, Christiana C.; Arrowsmith, Joseph E. (1 November 2009). "Respiratory failure". Surgery (Oxford). 27 (11): 475–479. doi:10.1016/j.mpsur.2009.09.007.
  3. Bakke, SA; Botker, MT; Riddervold, IS; Kirkegaard, H; Christensen, EF (22 November 2014). "Continuous positive airway pressure and noninvasive ventilation in prehospital treatment of patients with acute respiratory failure: a systematic review of controlled studies.". Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. 22 (1): 69. PMC 4251922Freely accessible. PMID 25416493. doi:10.1186/s13049-014-0069-8.
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