同: V/Q
関: Ventilation-per fusion

WordNet

the 17th letter of the Roman alphabet (同)q
the last imperial dynasty of China (from 1644 to 1912) which was overthrown by revolutionaries; during the Qing dynasty China was ruled by the Manchu (同)Qing dynasty, Ch''ing, Ch''ing dynasty, Manchu, Manchu dynasty
the 22nd letter of the Roman alphabet (同)v

PrepTutorEJDIC

(チェスの)queen
vanadium の化学記号
verb / verso / 《話》very / velocity / volt[s] / volume / vide

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2018/06/27 05:15:49」(JST)

wiki en

In respiratory physiology, the ventilation/perfusion ratio (V̇/Q̇ ratio or V/Q ratio) is a ratio used to assess the efficiency and adequacy of the matching of two variables:

V̇ or V – ventilation – the air that reaches the alveoli
Q̇ or Q – perfusion – the blood that reaches the alveoli via the capillaries

The V/Q ratio can therefore be defined as the ratio of the amount of air reaching the alveoli per minute to the amount of blood reaching the alveoli per minute—a ratio of volumetric flow rates. These two variables, V & Q, constitute the main determinants of the blood oxygen (O₂) and carbon dioxide (CO₂) concentration.

The V/Q ratio can be measured with a ventilation/perfusion scan.

A V/Q mismatch can cause a type 1 respiratory failure.

Physiology

Ideally, the oxygen provided via ventilation would be just enough to saturate the blood fully. In the typical adult, 1 litre of blood can hold about 200 mL of oxygen; 1 litre of dry air has about 210 mL of oxygen. Therefore, under these conditions, the ideal ventilation perfusion ratio would be about 0.95. If one were to consider humidified air (with less oxygen), then the ideal v/q ratio would be in the vicinity of 1.0, thus leading to concept of ventilation-perfusion equality or ventilation-perfusion matching. This matching may be assessed in the lung as a whole, or in individual or in sub-groups of gas-exchanging units in the lung. On the other side Ventilation-perfusion mismatch is the term used when the ventilation and the perfusion of a gas exchanging unit are not matched.

The actual values in the lung vary depending on the position within the lung. If taken as a whole, the typical value is approximately 0.8.^[1]

Because the lung is centered vertically around the heart, part of the lung is superior to the heart, and part is inferior. This has a major impact on the V/Q ratio:^[2]

apex of lung – higher
base of lung – lower

In a subject standing in orthostatic position (upright) the apex of the lung shows higher V/Q ratio, while at the base of the lung the ratio is lower but nearer to the optimal value for reaching adequate blood oxygen concentrations. While both ventilation and perfusion increase going from the apex to the base, perfusion increases to a greater degree than ventilation, lowering the V/Q ratio at the base of the lungs. The principal factor involved in the creation of this V/Q gradient between the apex and the base of the lung is gravity (this is why V/Q ratios change in positions other than the orthostatic position).

Ventilation

Gravity and the weight of the lung act on ventilation by increasing pleural pressure at the base (making it less negative) and thus reducing the alveolar volume. The lowest part of the lung in relation to gravity is called the dependent region. In the dependent region smaller alveolar volumes mean the alveoli are more compliant (more distensible) and so capable of more oxygen exchange. The apex, though showing a higher oxygen partial pressure, ventilates less efficiently since its compliance is lower and so smaller volumes are exchanged.

Perfusion

The impact of gravity on pulmonary perfusion expresses itself as the hydrostatic pressure of the blood passing through the branches of the pulmonary artery in order to reach the apical and basal areas of the lungs, acting respectively against or synergistically with the pressure developed by the right ventricle. Thus at the apex of the lung the resulting pressure can be insufficient for developing a flow (which can be sustained only by the negative pressure generated by venous flow towards the left atrium) or even for preventing the collapse of the vascular structures surrounding the alveoli, while the base of the lung shows an intense flow due to the higher resulting pressure.

Pathology

Extreme alterations of V/Q

An area with perfusion but no ventilation (and thus a V/Q of zero) is termed "shunt".
An area with ventilation but no perfusion (and thus a V/Q undefined though approaching infinity) is termed dead space.^[3]

Of note, few conditions constitute "pure" shunt or dead space as they would be incompatible with life, and thus the term V/Q mismatch is more appropriate for conditions in between these two extremes.

Pathophysiology

A lower V/Q ratio (with respect to the expected value for a particular lung area in a defined position) impairs pulmonary gas exchange and is a cause of low arterial partial pressure of oxygen (paO₂). Excretion of carbon dioxide is also impaired, but a rise in the arterial partial pressure of carbon dioxide (paCO₂) is very uncommon because this leads to respiratory stimulation and the resultant increase in alveolar ventilation returns paCO₂ to within the normal range. These abnormal phenomena are usually seen in chronic bronchitis, asthma, hepatopulmonary syndrome, and acute pulmonary edema.
A high V/Q ratio decreases PACO₂ and increases PAO₂. Because of the increased dead space ventilation, the PaO2 is reduced and thus also the peripheral oxygen saturation is lower than normal, leading to tachypnea and dyspnea. This finding is typically associated with pulmonary embolism (where blood circulation is impaired by an embolus). Ventilation is wasted, as it fails to oxygenate any blood. A high V/Q can also be observed in emphysema as a maladaptive ventilatory overwork of the undamaged lung parenchyma. Because of the loss of alveolar surface area, there is proportionally more ventilation per available perfusion area. As a contrast, this loss of surface area leads to decreased arterial pO₂ due to impaired gas exchange (see Fick's laws of diffusion).

References

^ VQ Ratio
^ Physiology of capnography
^ Respiratory Physiology (page 2)

External links

Overview at anaesthesiauk.com
ventilation-perfusion ratio at the US National Library of Medicine Medical Subject Headings (MeSH)
Physiology: 4/4ch4/s4ch4_24 - Essentials of Human Physiology
RT Corner (Educational Site for RT's and Nurses) at rtcorner.net

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English Journal

A rare case of acute respiratory distress syndrome secondary to acute lithium intoxication.

Kansagra AJ1, Yang E, Nambiar S, Patel PS, Karetzky MS.Author information 11Department of Internal Medicine, North Shore Medical Center, Salem, MA; and 2Department of Pulmonary and Critical Care, Newark Beth Israel Medical Center, Newark, NJ.AbstractLithium carbonate is a widely administered antimanic drug used for the treatment of bipolar disorder, schizoaffective disorder, and depression. Despite the established clinical efficacy of lithium, its usage must be approached with caution due to its narrow therapeutic index. Lithium poisoning results in multisystem toxicity, and characteristic clinical manifestations are directly correlated to serum lithium concentration. We describe a rather rare but fatal side effect of lithium: acute respiratory distress syndrome (ARDS) in a 46-year-old female on lithium for the treatment of bipolar disease. She was referred for generalized weakness, found in hemodynamic compromise, and had laboratory data significant for a lithium level of 3.3 mmole/L, needing emergent hemodialysis. Subsequently, she developed hypoxic respiratory failure requiring intubation. Her chest x-rays showed new bilateral pulmonary edema, the computed tomography scan showed extensive alveolar consolidation and V/Q scan of low probability for pulmonary embolism. She underwent 3 dialysis sessions and supportive care and was able to be extubated in 5 days. To our knowledge, 4 cases of ARDS after the onset of lithium toxicity have been documented. All patients presented with altered mental status at serum lithium levels ranging from 3.8 to 4.9 mmole/L and cardiogenic etiologies in addition to other likely causes of ARDS were ruled out in each case. The patients were treated with saline hydration (50%) or hemodialysis (50%), indicating that hemodialysis may be a permissive factor in lithium-associated ARDS development rather than a required component. Taken together, we believe that lithium is a likely culprit in the initiation of ARDS and propose the addition of ARDS to the family of clinical manifestations of severe lithium toxicity.
American journal of therapeutics.Am J Ther.2014 Mar-Apr;21(2):e31-4. doi: 10.1097/MJT.0b013e3182204feb.
Lithium carbonate is a widely administered antimanic drug used for the treatment of bipolar disorder, schizoaffective disorder, and depression. Despite the established clinical efficacy of lithium, its usage must be approached with caution due to its narrow therapeutic index. Lithium poisoning resul
PMID 21734531

Optimizing the ventilation-perfusion lung scan for image quality and radiation exposure.

Hur S1, Bauer A, McMillan N, Krupinski EA, Kuo PH.Author information 1Department of Medical Imaging, University of Arizona, Tucson, Arizona.AbstractOur purpose was to compare the performance of an initial ventilation-perfusion (V/Q) scan protocol with that of a data-driven modified protocol to improve diagnostic quality without increasing radiation dose to the patient.
Journal of nuclear medicine technology.J Nucl Med Technol.2014 Mar;42(1):51-4. doi: 10.2967/jnmt.113.128900. Epub 2014 Jan 30.
Our purpose was to compare the performance of an initial ventilation-perfusion (V/Q) scan protocol with that of a data-driven modified protocol to improve diagnostic quality without increasing radiation dose to the patient.METHODS: The initial V/Q scan protocol consisted of a ventilation scan after
PMID 24480918

Spinal dural AV fistula: an unusual cause of chest pain.

Bioh G1, Bogle R.Author information 1Department of Cardiology, St Helier Hospital, Surrey, UK.AbstractA 22 -year-old man presented with 6 months of sudden onset, incapacitating, left-sided chest pain occurring 1-2 times a week. The severity of the pain caused loss of consciousness several times leading to multiple fractures. Investigation with echocardiogram, exercise tolerance test, Holter monitor, chest X-ray and V/Q scan revealed no abnormality as did EEG and 48 h video telemetry. MRI of the thoracic and lumbar spine showed a spinal dural arteriovenous fistula (SDAVF) at the level of T6, confirmed on angiogram. The patient underwent division of the left T6 AV fistula. Following the operation, the patient has been completely pain free. Our patient, presenting in his early 20s does not fit the usual age demographic for SDAVF. A second atypical feature is his presentation with chest pain alone and no neurological symptoms. This case represents a rare presentation of SDAVF.
BMJ case reports.BMJ Case Rep.2014 Feb 14;2014(feb14_2). pii: bcr2013202038. doi: 10.1136/bcr-2013-202038.
A 22 -year-old man presented with 6 months of sudden onset, incapacitating, left-sided chest pain occurring 1-2 times a week. The severity of the pain caused loss of consciousness several times leading to multiple fractures. Investigation with echocardiogram, exercise tolerance test, Holter monitor,
PMID 24532234

Japanese Journal

$(GL(1)\times SO(q),V(q))$上の超関数の保型対 : 佐藤文広氏との共同研究 (保型形式および関連するゼータ関数の研究)

宮崎直
数理解析研究所講究録 1934, 90-103, 2015-02
NAID 110009883303

LITHIUM tert-BUTOXIDE-MEDIATED CARBOXYLATION REACTIONS OF UNPROTECTED INDOLES AND PYRROLES WITH CARBON DIOXIDE (Dedicated to Professor Isao Kuwajima on the occasion of his 77th birthday)

Yoo Woo-Jin,Nguyen Thanh V. Q.,Capdevila Montse Guiteras [他]
Heterocycles : an international journal for reviews and communications in heterocyclic chemistry 90(2), 1196-1204, 2015-01-01
NAID 40020330489

バックスパッタによる微細針状ダイヤモンド電極の表面形状と二次電子放出特性

比嘉司,小野志門,三栖貴行 [他],後藤みき,荒井俊彦,Higa Tsukasa,Ono Shimon,Misu Takayuki,Goto Miki,Arai Toshihiko
神奈川工科大学研究報告. B, 理工学編 (36), 41-44, 2012-03
NAID 120005325272

Related Pictures

Mediastinum, emphysema Slide 17 of 37 Overview VQMismatch 2 Small V/Q = 1 conditions that cause low v q atelectasis Ventilation Perfusion Scan

★リンクテーブル★

リンク元	「換気血流比」「ventilation-perfusion mismatch」「ventilation-perfusion ratio」
拡張検索	「V/Q mismatch」
関連記事	「Vd」「Q」「V」

「換気血流比」

　　[★]

英: ventilation perfusion ratio, ventilation-perfusion ratio
同: 換気-血流比、v/q比、V/Q
関: 換気血流不均等

換気血流比の正常値：0.8？

肺胞の換気量(V_A)と肺血流量(Q)の比　→　V_A/Q

肺の上部ほど肺胞の換気量(V_A)は小さく、下部は大きい。
肺の上部ほど肺血流量(Q)は小さいく、下部では大きいが、その度合いはは肺胞の換気量より大きい。
このため、肺上部のV_A/Q　＞　肺下部のV_A/Q　となる (SP.648)

V_A/Q = 0 　：シャント：換気のない肺胞に血流が流れるということ。
V_A/Q = ∞　：肺胞死腔：血流のない肺胞が換気されるということ。

「ventilation-perfusion mismatch」

　　[★] 換気血流不均等

同: V/Q

「ventilation-perfusion ratio」

　　[★] 換気血流比

同: V/Q

「V/Q mismatch」

　　[★]

関: Ventilationfper fusion mismatch

「Vd」

　　[★]

「Q」

　　[★]

「V」

　　[★]

[1] VQ Ratio

[2] Physiology of capnography

[3] Respiratory Physiology (page 2)

v t e Respiratory physiology
Respiration	breath inhalation exhalation respiratory rate respirometer pulmonary surfactant compliance elastic recoil hysteresivity airway resistance bronchial hyperresponsiveness constriction dilatation mechanical ventilation
Control	pons pneumotaxic center apneustic center medulla dorsal respiratory group ventral respiratory group chemoreceptors central peripheral pulmonary stretch receptors Hering–Breuer reflex
Lung volumes	VC FRC Vt dead space CC PEF calculations respiratory minute volume FEV1/FVC ratio Lung function tests spirometry body plethysmography peak flow meter nitrogen washout
Circulation	pulmonary circulation hypoxic pulmonary vasoconstriction pulmonary shunt
Interactions	ventilation (V) Perfusion (Q) Ventilation/perfusion ratio V/Q scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–haemoglobin dissociation curve (Oxygen saturation 2,3-BPG Bohr effect Haldane effect) carbonic anhydrase (chloride shift) oxyhemoglobin respiratory quotient arterial blood gas diffusion capacity (DLCO)
Insufficiency	high altitude oxygen toxicity hypoxia

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V/Q