Respiratory failure

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This editable Main Article is under development and subject to a disclaimer.

[edit intro]

In medicine, respiratory failure is "failure to adequately provide oxygen to cells of the body and to remove excess carbon dioxide from them."[1]

## Contents

* 1 Diagnosis
* 2 Treatment
* 2.1 Artificial respiration
* 2.2 Extracorporeal membrane oxygenation
* 3 References

## Diagnosis[edit]

PaO2/FiO2 ratio (PF ratio)
P/F ratio=(PaO2Fi02)×100

* Normal is 500
* ARDS is < 200

This measure is easier to calculate. Comparative studies suggest it correlates better with pulmonary shunts than does the A-a gradient.[2][3][4]

Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO2D)
A-a gradient=PAO2 − PaO2
PAO2=Fi02*(760−47) − PaCO20.8

* Normal is < 10 mm Hg

The A-a gradient is harder to calculate, but accounts for changes in respiration as measured by the partial pressure of carbon dioxide. However, this calculation relies on the respiratory quotient being constant in the prediction of alveolar CO2 When compared to the PF ratio, the A-a gradient is found to correlate less well with pulmonary shunting.[2][3][4]

Among outpatients with possible pulmonary embolism, the A-a gradient may be a better test.[5]

An online calculator for the A-a gradient is at http://www.mdcalc.com/aagrad.

## Treatment[edit]

### Artificial respiration[edit]

For more information, see: Artificial respiration.

### Extracorporeal membrane oxygenation[edit]

Extracorporeal membrane oxygenation (ECMO) is "application of a life support system that circulates the blood through an oxygenating system, which may consist of a pump, a membrane oxygenator, and a heat exchanger. Examples of its use are to assist victims of smoke inhalation injury, respiratory failure, and cardiac failure."[6] ECMO may increase survival in respiratory failure.[7]

## References[edit]

1. ↑ Anonymous (2025), Respiratory failure (English). Medical Subject Headings. U.S. National Library of Medicine.
2. ↑ 2.0 2.1 Covelli HD, Nessan VJ, Tuttle WK (1983). "Oxygen derived variables in acute respiratory failure". Crit. Care Med. 11 (8): 646–9. PMID 6409506. [e]
3. ↑ 3.0 3.1 El-Khatib MF, Jamaleddine GW (2004). "A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery". Chest 125 (2): 592–6. PMID 14769743. [e]
4. ↑ 4.0 4.1 Cane RD, Shapiro BA, Templin R, Walther K (1988). "Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients". Crit. Care Med. 16 (12): 1243–5. PMID 3191742. [e]
5. ↑ McFarlane MJ, Imperiale TF (1994). "Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism". Am. J. Med. 96 (1): 57–62. PMID 8304364. [e]
6. ↑ Anonymous (2025), Extracorporeal membrane oxygenation (English). Medical Subject Headings. U.S. National Library of Medicine.
7. ↑ Peek GJ, Mugford M, Tiruvoipati R, Wilson A, Allen E, Thalanany MM et al. (2009). "Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial.". Lancet. DOI:10.1016/S0140-6736(09)61069-2. PMID 19762075. Research Blogging.