Oxygenation

# Overview
Oxygenation refers to the amount of oxygen in a medium.  In blood it may be taken to be synonymous with saturation, which describes the degree to which the oxygen-carrying capacity of haemoglobin is utilised, normally 98-100%.
Oxygenation also refers to the process of adding oxygen to a medium such as water or body tissue. Claims have been made that oxygenation of human tissue prevent diseases, including cancer, however some regard these claims as unverifiable.  Oxygenation of various fluorocarbon liquids has been used successfully in liquid breathing systems, allowing air-breathing animals, including humans, to breathe via liquids for short periods of time.

# Monitoring

## Respiration and oxygenation
An example in a healthy person:
A higher ratio indicates better gas exchange:
- Normal is 500
- ARDS is < 200
Comparative studies suggest this measure correlates better with pulmonary shunts than does the A-a gradient.

### Oxygenation index
-r
A lower oxygenation index indicates better gas exchange. The oxygenation index, which includes the mean airway pressure, may better correlate with intrapulmonary shunting than the PF ratio

### Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO2D)
- 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.
Among outpatients with possible pulmonary embolism, the A-a gradient may be a better test.
An online calculator for the A-a gradient is at .

### ROX
The respiratory rateoxygenation (ROX) index by dividing the oximetry-derived oxygen saturation by the respiratory rate.
- The ROX predicts respiratory failure from COVID-19 when 1.4 ("with a sensitivity of 85%, a specificity of 86%, and an AUC of 0.86").

## Tissue perfusion
In patients with septic shock, maintaining the central venous oxygen saturation (ScvO2) > 70% is a health care quality assurance measure for the Institute for Healthcare Improvement.  This is measured from the superior vena cava. This is hard to predict by physical examination.
In patients with septic shock, maintaining the mixed venous oxygen saturation (ScvO2) > 65% is a health care quality assurance measure for the Institute for Healthcare Improvement that is an alternative to the central venous oxygen saturation. This is measured from a pulmonary artery catheter.  This is hard to predict by physical examination.
The mixed venous pressure may be lower than the central venous pressure due to mixing with blood from the splanchnic circulation or carotid sinuses that has lower oxygen content.
Tissue oxygen saturation (StO2) at the thenar eminence may be an alternative, non-invasive measurement.
Maintaining lactate clearance about 10% may be an easier alternative than invasive measurements of oxygenation according to a randomized controlled trial by EMShockNet.
Capnography, which is "continuous recording of the carbon dioxide content of expired air," may detect respiratory depression before hypoxemia occurs. Proposed criteria for respiratory depression are:
- End tidal CO2 (ETCO2)  level  50 mm Hg
- ETCO2 change from baseline of 10%
- Loss of waveform for  15 seconds

# See Also
- Oxygenate
-  Jump up to: 1.0 1.1 Covelli HD, Nessan VJ, Tuttle WK (1983). "Oxygen derived variables in acute respiratory failure". Crit. Care Med. 11 (8): 6469. PMID 6409506.CS1 maint: Multiple names: authors list (link) .mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
-  Jump up to: 2.0 2.1 2.2 El-Khatib MF, Jamaleddine GW (2004). "A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery". Chest. 125 (2): 5926. PMID 14769743.
-  Jump up to: 3.0 3.1 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): 12435. PMID 3191742.CS1 maint: Multiple names: authors list (link)
-  Marini JJ, Ravenscraft SA (1992). "Mean airway pressure: physiologic determinants and clinical importance--Part 1: Physiologic determinants and measurements". Crit Care Med. 20 (10): 146172. PMID 1395670.
-  Marini JJ, Ravenscraft SA (1992). "Mean airway pressure: physiologic determinants and clinical importance--Part 2: Clinical implications". Crit Care Med. 20 (11): 160416. PMID 1424706.
-  McFarlane MJ, Imperiale TF (1994). "Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism". Am. J. Med. 96 (1): 5762. PMID 8304364.
-  Mukhtar A, Rady A, Hasanin A, Lotfy A, El Adawy A, Hussein A;  et al. (2021). "Admission SpO2 and ROX index predict outcome in patients with COVID-19". Am J Emerg Med. 50: 106110. doi:10.1016/j.ajem.2021.07.049. PMC 8313790 Check |pmc= value (help). PMID 34332217 Check |pmid= value (help).CS1 maint: Multiple names: authors list (link)
-  Maintain Adequate Central Venous Oxygen Saturation Institute for Healthcare Improvement
-  Jump up to: 9.0 9.1 Grissom CK, Morris AH, Lanken PN, Ancukiewicz M, Orme JF, Schoenfeld DA;  et al. (2009). "Association of physical examination with pulmonary artery  catheter parameters in acute lung injury". Crit Care Med. 37 (10): 27206. PMID 19885995.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
-  Maintain Adequate Central Venous Oxygen Saturation Institute for Healthcare Improvement
-  Kopterides P, Mavrou I, Kostadima E (2005). "Central or mixed venous oxygen saturation?". Chest. 128 (2): 10734, author reply 1074-5. doi:10.1378/chest.128.2.1073. PMID 16100219.CS1 maint: Multiple names: authors list (link)
-  Podbregar M, Mozina H (2007). "Skeletal muscle oxygen saturation does not estimate mixed venous oxygen saturation in patients with severe left heart failure and additional severe sepsis or septic shock". Crit Care. 11 (1): R6. doi:10.1186/cc5153. PMC 2147710. PMID 17227587.CS1 maint: PMC format (link)
-  Leone M, Blidi S, Antonini F, Meyssignac B, Bordon S, Garcin F;  et al. (2009). "Oxygen tissue saturation is lower in nonsurvivors than in survivors after early resuscitation of septic shock". Anesthesiology. 111 (2): 36671. doi:10.1097/ALN.0b013e3181aae72d. PMID 19602965.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
-  Jones AE, Shapiro NI, Trzeciak S, Arnold RC, Claremont HA, Kline JA;  et al. (2010). "Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial". JAMA. 303 (8): 73946. doi:10.1001/jama.2010.158. PMID 20179283.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
-  Anonymous (2023), Capnography (English). Medical Subject Headings. U.S. National Library of Medicine.
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