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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/02 21:28:14」(JST)

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Fraction of inspired oxygen (FiO₂) is the fraction or percentage of oxygen in the space being measured. Medical patients experiencing difficulty breathing are provided with oxygen-enriched air, which means a higher-than-atmospheric FiO₂. Natural air includes 20.9% oxygen, which is equivalent to FiO₂ of 0.21. Oxygen-enriched air has a higher FiO₂ than 0.21, up to 1.00, which means 100% oxygen. FiO₂ is typically maintained below 0.5 even with mechanical ventilation, to avoid oxygen toxicity.^[1] If a patient is wearing a nasal cannula or a simple face mask, each additional liter of oxygen adds about 4% to their FiO2 (for example, a patient with a nasal cannula with 2L of oxygen attached would have an FIO2 of 21% + 8% =29%).

Often used in medicine the FiO₂ is used to represent the percentage of oxygen participating in gas-exchange. If the barometric pressure changes, the FiO₂ may remain constant while the partial pressure of oxygen changes with the change in barometric pressure.

Equations

Abbreviated alveolar air equation

P_AO₂, P_EO₂, and P_iO₂ are the partial pressures of oxygen in alveolar, expired, and inspired gas, respectively, and VD/VT is the ratio of physiologic dead space over tidal volume.

Medicine

In medicine the FiO₂ is the assumed percentage of oxygen concentration participating in gas exchange in the alveoli.^[2]

Uses

The ratio between partial pressure of oxygen in arterial blood (PaO2) and FiO₂ is used as an indicator of hypoxemia per the American-European Consensus Conference on lung injury. A high FiO₂ has been shown to alter the ratio of PaO2/FiO₂.^[2]

PaO2/FiO2 ratio

The ratio of partial pressure arterial oxygen and fraction of inspired oxygen, sometimes called the Carrico index, is a comparison between the oxygen level in the blood and the oxygen concentration that is breathed. This helps to determine the degree of any problems with how the lungs transfer oxygen to the blood.^[3] A sample of arterial blood is collected for this test.^[4] A PaO2/FiO2 ratio less than or equal to 200 mmHg is necessary for the diagnosis of acute respiratory distress syndrome by the AECC criteria.^[5] The more recent Berlin criteria defines mild ARDS at a ratio of <300.

A PaO2/FiO2 ratio less than or equal to 250 mmHg is one of the minor criteria for severe community acquired pneumonia (i.e., possible indication for inpatient treatment).

A PaO2/FiO2 ratio less than or equal to 333 mmHg is one of the variables in the SMART-COP risk score for intensive respiratory or vasopressor support in community-acquired pneumonia.

Related mathematics

Alveolar air equation

The alveolar air equation is the following formula, used to calculate the partial pressure of alveolar gas:

References

^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688103/
^ ^a ^b Allardet-Servent J, Forel JM, Roch A, Guervilly C, Chiche L, Castanier M et al. (2009). "FIO2 and acute respiratory distress syndrome definition during lung protective ventilation.". Crit Care Med 37 (1): 202–7, e4–6. doi:10.1097/CCM.0b013e31819261db. PMID 19050631.
^ Toy P, Popovsky MA, Abraham E, Ambruso DR, Holness LG, Kopko PM et al. (2005). "Transfusion-related acute lung injury: definition and review.". Crit Care Med 33 (4): 721–6. doi:10.1097/01.ccm.0000159849.94750.51. PMID 15818095.
^ Tietz NW (Ed): Clinical Guide to Laboratory Tests, 3rd ed. W. B. Saunders, Philadelphia, PA, 1995.
^ Mason, R. Murray and Nadel's Textbook of Respiratory Medicine, 5th ed. Philadelphia, PA 2010

External links

FiO2 by Delivery Device - Shows FiO2 by common oxygen deliver systems.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 低酸素血症の酸素供給およびメカニズム oxygenation and mechanisms of hypoxemia
2. 機械的人工換気の概要 overview of mechanical ventilation
3. 酸素毒性 oxygen toxicity
4. 眼の待機手術に対する麻酔 anesthesia for elective eye surgery
5. 急性呼吸窮迫症候群：成人における臨床的特徴および診断 acute respiratory distress syndrome clinical features and diagnosis in adults

English Journal

Sublingual microcirculatory effects of enalaprilat in an ovine model of septic shock.

Salgado DR, He X, Su F, de Sousa DB, Penaccini L, Maciel LK, Taccone F, Rocco JR, Silva E, De Backer D, Vincent JL.Source*Department of Intensive Care, Erasme Hospital, Universite Libre de Bruxelles, Belgium; and †Department of Internal Medicine, Clementino Fraga Filho University Hospital, Universidade Federal do Rio de Janeiro, Rio de Janeiro; ‡Department of Experimental Surgery, Universidade Federal do Estado de Sao Paulo; and §Intensive Care Unit, Albert Einstein Hospital, Sao Paulo, Brazil.
Shock (Augusta, Ga.).2011 Jun;35(6):542-9.
Severe sepsis is frequently associated with microcirculatory abnormalities despite seemingly adequate hemodynamic resuscitation. As increased serum angiotensin II levels may play a role in this dysfunction, we evaluated the microcirculatory effects of enalaprilat in an experimental model of septic s
PMID 21283060

Beneficial effects of concomitant neuronal and inducible nitric oxide synthase inhibition in ovine burn and inhalation injury.

Lange M, Hamahata A, Enkhbaatar P, Cox RA, Nakano Y, Westphal M, Traber LD, Herndon DN, Traber DL.Source*Department of Anesthesiology, Investigational Intensive Care Unit, The University of Texas Medical Branch, and Shriners Hospitals for Children, Galveston, Texas; †Department of Anesthesiology and Intensive Care, University of Muenster, Muenster, Germany; and Departments of ‡Pathology and §Surgery, Investigational Intensive Care Unit, The University of Texas Medical Branch, and Shriners Hospitals for Children, Galveston, Texas.
Shock (Augusta, Ga.).2011 Jun;35(6):626-31.
Different isoforms of nitric oxide (NO) synthase are critically involved in the development of pulmonary failure secondary to acute lung injury. Here we tested the hypothesis that simultaneous blockade of inducible and neuronal NO synthase effectively prevents the pulmonary lesions in an ovine model
PMID 21263377

Japanese Journal

Reduction of the PaO_2/FiO_2 Ratio in Acute Aortic Dissection : Relationship Between the Extent of Dissection and Inflammation

KURABAYASHI Manabu,OKISHIGE Kaoru,AZEGAMI Koji,UESHIMA Daisuke,SUGIYAMA Koji,SHIMURA Tsukasa,MAEDA Minetaka,AOYAGI Hideshi,ISOBE Mitsuaki
Circulation journal : official journal of the Japanese Circulation Society 74(10), 2066-2073, 2010-09-25
… C-reactive protein (CRP) levels, white blood cell (WBC) counts, body temperature and arterial partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio were measured serially. … Oxygenation impairment was defined as a PaO2/FiO2 ratio ≤200. … It was found that there were inverse correlations between the PaO2/FiO2 ratio and AAD% (r=-0.604, P<0.001), and between peak CRP levels and the PaO2/FiO2 ratio (r=-0.635, P<0.001). …
NAID 10026640078

Effect of Neutrophil Elastase Inhibitor (Sivelestat Sodium) in the Treatment of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS): A Systematic Review and Meta-Analysis

Iwata Kentaro,Doi Asako,Ohji Goh,Oka Hideaki,Oba Yuichiro,Takimoto Kohei,Igarashi Wataru,Gremillion David H.,Shimada Toshihiko
Internal Medicine 49(22), 2423-2432, 2010
… There was no difference in mechanical ventilation days (standardized mean difference -0.43, -1.12 to 0.27), but sivelestat was associated with a better short term PaO2/FiO2 ratio (0.30, 0.05 to 0.56). …
NAID 130000413370

Related Pictures

schematic demonstrates the physical Nasal Cannula Fio2 Calculation FIO2 “T” Adapter GOod luck in school! FiO2 50%, increasing FiO2 will not change SaO2 Fio2 The lung ventilator incorporates dual

★リンクテーブル★

リンク元	「急性呼吸促迫症候群」「肺胞気動脈血酸素分圧較差」「fraction of inspired oxygen」「inspired oxygen fraction」
拡張検索	「PaO2/FIO2」

「急性呼吸促迫症候群」

　　[★]

distress
英: acute respiratory distress syndrome, ARDS
同: 急性呼吸窮迫症候群、成人呼吸促迫症候群 adult respiratory distress syndrome
関: 肺水腫

概念

様々な原因に続発する急性の肺損傷であり、その本態は血管内皮細胞が傷害されて生じた透過性肺水腫
侵襲により肺の非特異的炎症と肺微小血管内皮の透過性が亢進した非心原性肺水腫
心不全は除外する必要がある

病因

IMD.743

直接肺障害

胃内容物の誤嚥：22-36%
肺挫傷：17-22%

間接肺障害

敗血症：35-45%
頻回の輸血：5-36%
多発性長管骨骨折：-%

ICU.364

頭蓋内圧亢進、血液製剤・カテーテル関連敗血症・薬物、肺炎・肺挫傷、人工心肺、膵炎、bacterial translocation、エンドトキシン血症、尿路感染症からの敗血症、羊水塞栓、長管骨骨折

ARDSの原因と死亡率

ICU.364

	発生率(%)	死亡率(%)
敗血症	41	50
大量輸血	36	35
肺挫傷	22	12
胃内容誤嚥	22	21
多発骨折	11	9
薬物過量	9	4
全ての高リスク状態	26	19

疫学

病理

病理学的にはびまん性肺胞障害(DAD)である。

肺胞隔壁の損傷　←　炎症による

血管内皮

血管透過性亢進　→　肺水腫

血管内皮細胞の障害による血管透過性の亢進

症状

診断

診断基準

1. 急性発症，
2. 胸部X線写真で両側浸潤影，
3. PaO2/FIO2≦200　　50%O2を吸入させてもPaO2 100 mmHgにしかならないというイメージか
4. 左心不全の否定

上記を満たし、PaO2/FIO2≦300の軽症例は急性肺損傷 ALI acute lung injury、

ARDSとALI

	経過	酸素化	単純胸部X線	肺動脈楔入圧
ALI	急性	PaO2/FIO2≦300mmHg	両側性の浸潤影	≦18mmHg or 理学的に左房圧上昇を認めない
ARDS	急性	PaO2/FIO2≦200mmHg	両側性の浸潤影	≦18mmHg or 理学的に左房圧上昇を認めない

鑑別診断

検査

治療

ICU.368- YN.I-121 参考3

呼吸管理：気管挿管し人工呼吸管理とする。　⇔　急性肺障害ではNIPPVでよい(低いPEEPで良いから。ARDSの場合はは高いPEEPが要求されるのであろう)。

低容量換気とする(機能している肺は減少しており、高用量換気では過膨張による末梢の肺胞を破壊しうる)。
管理目標：予測体重を利用した6ml/kgの一回換気量を維持する。30cmH2O未満の呼気終末プラトー圧を維持する。重症呼吸性アシドーシスを避ける。
高二酸化炭素許容：Paco2が60-70mmHgで動脈血pH 7.2-7.25ならば大多数の患者で安全。
PaO2=50-80 or SpO2=88-95%となるように管理。
PEEP：5-7cmH2Oを付与。

Oxygenation will be maintained in the target ranges using the following PEEP/FiO2 combinations:
FiO2	0.3	0.4	0.4	0.5	0.5	0.6	0.7	0.7	0.7	0.8	0.9	0.9	0.9	1	1
PEEP(cmH2O)	5	5	8	8	10	10	10	12	14	14	14	16	18	18	20-24