Blood gas tension - wikipedia Blood gas tension Blood gas tension refers to the partial pressure of gases in blood. There are several significant purposes for measuring gas tension ; the most common gas tensions measured are oxygen tension ( P O ), the carbon dioxide tension ( P CO ) and carbon monoxide tension ( P CO ). The subscript x in each symbol represents the source of the gas being measured ; `` a '' meaning arterial, `` A '' being alveolar, `` v '' being venous, `` c '' being capillary. Blood gas tests ( such as arterial blood gas tests ) measure these partial pressures. Contents 1 Oxygen tension 2 Carbon dioxide tension 3 Carbon monoxide tension 4 Significance 5 Equations 5.1 Oxygen content 5.2 Oxygen saturation 6 See also 7 References Oxygen tension Arterial blood oxygen tension ( normal ) P O -- Partial pressure of oxygen at sea level ( 765 mmHg ) in arterial blood is between 75 mmHg and 100 mmHg. Venous blood oxygen tension ( normal ) P O -- Oxygen tension in venous blood at sea level is between 30 mmHg and 40 mmHg. Carbon dioxide tension Carbon dioxide is a by - product of food metabolism and in high amounts has toxic effects including : dyspnea, acidosis and altered consciousness. Arterial blood carbon dioxide tension P CO -- Partial pressure of carbon dioxide at sea level ( 765 mmHg ) in arterial blood is between 35 mmHg and 45 mmHg. Venous blood carbon dioxide tension P CO -- Partial pressure of carbon dioxide at sea level in venous blood is between 40 mmHg and 50 mmHg. Carbon monoxide tension Arterial carbon monoxide tension ( normal ) P CO -- Partial pressure of CO at sea level ( 765 mmHg ) in arterial blood is approximately 0.02. It can be slightly higher in smokers and people living in dense urban areas. Significance The partial pressure of gas in blood is significant because it is directly related to ventilation and oxygenation. When used alongside the pH balance of the blood, the P CO and HCO ( and Lactate ) suggest to the health care practitioner which interventions, if any, should be made. Equations Oxygen Content C a O 2 = 1.36 ∗ H g b ∗ S a O 2 100 + 0.0031 ∗ P a O 2 ( displaystyle C_ ( a ) O_ ( 2 ) = 1.36 * Hgb * ( \frac ( S_ ( a ) O_ ( 2 ) ) ( 100 ) ) + 0.0031 * P_ ( a ) O_ ( 2 ) ) The constant, 1.36, is the amount of oxygen ( ml at 1 atmosphere ) bound per gram of hemoglobin. The exact value of this constant varies from 1.34 to 1.39, depending on the reference and the way it is derived. The constant 0.0031 represents the amount of oxygen dissolved in plasma. The dissolved - oxygen term is generally small relative to the term for hemoglobin - bound oxygen, but becomes significant at very high P O ( as in a hyperbaric chamber ) or in severe anemia. Oxygen saturation S O 2 = ( 23, 400 p O 2 3 + 150 p O 2 + 1 ) − 1 ( displaystyle SO_ ( 2 ) = ( ( \frac ( 23,400 ) ( pO_ ( 2 ) ^ ( 3 ) + 150pO_ ( 2 ) ) ) + 1 ) ^ ( - 1 ) ) This is an estimation and does not account for differences in temperature, pH and concentrations of 2, 3 DPG. See also Alveolar air equation Fick 's laws of diffusion References Jump up ^ Severinghaus JW, Astrup P, Murray JF ( 1998 ). `` Blood gas analysis and critical care medicine ''. Am J Respir Crit Care Med. 157 ( 4 Pt 2 ) : S114 -- 22. PMID 9563770. doi : 10.1164 / ajrccm. 157.4. nhlb1 - 9. Jump up ^ Bendjelid K, Schütz N, Stotz M, Gerard I, Suter PM, Romand JA ( 2005 ). `` Transcutaneous PCO2 monitoring in critically ill adults : clinical evaluation of a new sensor ''. Crit Care Med. 33 ( 10 ) : 2203 -- 6. PMID 16215371. doi : 10.1097 / 01. ccm. 0000181734.26070. 26. ^ Jump up to : Yildizdaş D, Yapicioğlu H, Yilmaz HL, Sertdemir Y ( 2004 ). `` Correlation of simultaneously obtained capillary, venous, and arterial blood gases of patients in a paediatric intensive care unit ''. Arch Dis Child. 89 ( 2 ) : 176 -- 80. PMC 1719810. PMID 14736638. doi : 10.1136 / adc. 2002.016261. Jump up ^ Shapiro BA ( 1995 ). `` Temperature correction of blood gas values ''. Respir Care Clin N Am. 1 ( 1 ) : 69 -- 76. PMID 9390851. Jump up ^ Malatesha G, Singh NK, Bharija A, Rehani B, Goel A ( 2007 ). `` Comparison of arterial and venous pH, bicarbonate, PCO2 and PO2 in initial emergency department assessment ''. Emerg Med J. 24 ( 8 ) : 569 -- 71. PMC 2660085. PMID 17652681. doi : 10.1136 / emj. 2007.046979. ^ Jump up to : Chu YC, Chen CZ, Lee CH, Chen CW, Chang HY, Hsiue TR ( 2003 ). `` Prediction of arterial blood gas values from venous blood gas values in patients with acute respiratory failure receiving mechanical ventilation ''. J Formos Med Assoc. 102 ( 8 ) : 539 -- 43. PMID 14569318. Jump up ^ Walkey AJ, Farber HW, O'Donnell C, Cabral H, Eagan JS, Philippides GJ ( 2010 ). `` The accuracy of the central venous blood gas for acid - base monitoring ''. J Intensive Care Med. 25 ( 2 ) : 104 -- 10. PMID 20018607. doi : 10.1177 / 0885066609356164. Jump up ^ Adrogué HJ, Rashad MN, Gorin AB, Yacoub J, Madias NE ( 1989 ). `` Assessing acid - base status in circulatory failure. Differences between arterial and central venous blood ''. N Engl J Med. 320 ( 20 ) : 1312 -- 6. PMID 2535633. doi : 10.1056 / NEJM198905183202004. ^ Jump up to : Williams AJ ( 1998 ). `` ABC of oxygen : assessing and interpreting arterial blood gases and acid - base balance ''. BMJ. 317 ( 7167 ) : 1213 -- 6. PMC 1114160. PMID 9794863. doi : 10.1136 / bmj. 317.7167. 1213. ^ Jump up to : Hansen JE ( 1989 ). `` Arterial blood gases ''. Clin Chest Med. 10 ( 2 ) : 227 -- 37. PMID 2661120. Jump up ^ Tobin MJ ( 1988 ). `` Respiratory monitoring in the intensive care unit ''. Am Rev Respir Dis. 138 ( 6 ) : 1625 -- 42. PMID 3144222. doi : 10.1164 / ajrccm / 138.6. 1625. Jump up ^ `` Oxygen Content ''. Retrieved October 7, 2014. Jump up ^ Severinghaus, J.W. ( 1979 ). `` Simple, accurate equations for human blood O dissociation computations '' ( PDF ). J Appl Physiol. 46 ( 3 ) : 599 -- 602. PMID 35496. 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Question: the partial pressure of carbon dioxide in arterial blood is approximately
Answer: at sea level (765 mmHg) in arterial blood is between 35 mmHg and 45 mmHg