| 1. |
- Mure, M, et al.
(författare)
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Regional ventilation-perfusion distribution is more uniform in the prone position
- 2000
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 88:3, s. 1076-1083
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Tidskriftsartikel (refereegranskat)abstract
- The arterial blood[Formula: see text] is increased in the prone position in animals and humans because of an improvement in ventilation (V˙a) and perfusion (Q˙) matching. However, the mechanism of improvedV˙a/Q˙ is unknown. This experiment measured regionalV˙a/Q˙ heterogeneity and the correlation between V˙a andQ˙ in supine and prone positions in pigs. Eight ketamine-diazepam-anesthetized, mechanically ventilated pigs were studied in supine and prone positions in random order. RegionalV˙a and Q˙ were measured using fluorescent-labeled aerosols and radioactive-labeled microspheres, respectively. The lungs were dried at total lung capacity and cubed into 603–967 small (∼1.7-cm3) pieces. In the prone position the homogeneity of the ventilation distribution increased ( P = 0.030) and the correlation betweenV˙a and Q˙ increased (correlation coefficient = 0.72 ± 0.08 and 0.82 ± 0.06 in supine and prone positions, respectively, P = 0.03). The homogeneity of the V˙a/Q˙distribution increased in the prone position ( P = 0.028). We conclude that the improvement inV˙a/Q˙ matching in the prone position is secondary to increased homogeneity of theV˙a distribution and increased correlation of regional V˙a andQ˙.
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| 2. |
- Petersson, J, et al.
(författare)
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Gas exchange and ventilation-perfusion relationships in the lung
- 2014
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Ingår i: The European respiratory journal. - : European Respiratory Society (ERS). - 1399-3003 .- 0903-1936. ; 44:4, s. 1023-1041
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Tidskriftsartikel (refereegranskat)abstract
- This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2andPCO2) are determined by the ratio of alveolar ventilation to blood flow (V′A/Q′) for each unit. Shunt and lowV′A/Q′ regions are two examples ofV′A/Q′ mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspiredPO2cause hypoxaemia, even in the absence ofV′A/Q′ mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (highV′A/Q′ regions) result in alveolar dead space and increased wasted ventilation,i.e.less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterialPCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar–arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect ofV′A/Q′ mismatch on gas exchange. The types ofV′A/Q′ mismatch causing impaired gas exchange vary characteristically with different lung diseases.
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| 3. |
- Petersson, J, et al.
(författare)
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Gas Exchange in the Lung
- 2023
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Ingår i: Seminars in respiratory and critical care medicine. - 1098-9048. ; 44:055, s. 555-568
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Petersson, J, et al.
(författare)
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Imaging regional PAO2 and gas exchange
- 2012
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 113:2, s. 340-352
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Tidskriftsartikel (refereegranskat)abstract
- Several methods allow regional gas exchange to be inferred from imaging of regional ventilation and perfusion (V/Q) ratios. Each method measures slightly different aspects of gas exchange and has inherent advantages and drawbacks that are reviewed. Single photon emission computed tomography can provide regional measure of ventilation and perfusion from which regional V/Q ratios can be derived. PET methods using inhaled or intravenously administered nitrogen-13 provide imaging of both regional blood flow, shunt, and ventilation. Electric impedance tomography has recently been refined to allow simultaneous measurements of both regional ventilation and blood flow. MRI methods utilizing hyperpolarized helium-3 or xenon-129 are currently being refined and have been used to estimate local PaO2 in both humans and animals. Microsphere methods are included in this review as they provide measurements of regional ventilation and perfusion in animals. One of their advantages is their greater spatial resolution than most imaging methods and the ability to use them as gold standards against which new imaging methods can be tested. In general, the reviewed methods differ in characteristics such as spatial resolution, possibility of repeated measurements, radiation exposure, availability, expensiveness, and their current stage of development.
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| 5. |
- Petersson, J, et al.
(författare)
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Paradoxical redistribution of pulmonary blood flow in prone and supine humans exposed to hypergravity
- 2006
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 100:1, s. 240-248
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesized that exposure to hypergravity in the supine and prone postures causes a redistribution of pulmonary blood flow to dependent lung regions. Four normal subjects were exposed to hypergravity by use of a human centrifuge. Regional lung perfusion was estimated by single-photon-emission computed tomography (SPECT) after administration of 99mTc-labeled albumin macroaggregates during normal and three times normal gravity conditions in the supine and prone postures. All images were obtained during normal gravity. Exposure to hypergravity caused a redistribution of blood flow from dependent to nondependent lung regions in all subjects in both postures. We speculate that this unexpected and paradoxical redistribution is a consequence of airway closure in dependent lung regions causing alveolar hypoxia and hypoxic vasoconstriction. Alternatively, increased vascular resistance in dependent lung regions is caused by distortion of lung parenchyma. The redistribution of blood flow is likely to attenuate rather than contribute to the arterial desaturation caused by hypergravity.
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| 6. |
- Petersson, J, et al.
(författare)
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Physiological evaluation of a new quantitative SPECT method measuring regional ventilation and perfusion
- 2004
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 96:3, s. 1127-1136
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a new quantitative single-photon-emission computed tomography (SPECT) method that uses 113mIn-labeled albumin macroaggregates and Technegas (99mTc) to estimate the distributions of regional ventilation and perfusion for the whole lung. The multiple inert-gas elimination technique (MIGET) and whole lung respiratory gas exchange were used as physiological evaluations of the SPECT method. Regional ventilation and perfusion were estimated by SPECT in nine healthy volunteers during awake, spontaneous breathing. Radiotracers were administered with subjects sitting upright, and SPECT images were acquired with subjects supine. Whole lung gas exchange of MIGET gases and arterial Po2 and Pco2 gases was predicted from estimates of regional ventilation and perfusion. We found a good agreement between measured and SPECT-predicted exchange of MIGET and respiratory gases. Correlations ( r2) between SPECT-predicted and measured inert-gas excretions and retentions were 0.99. The method offers a new tool for measuring regional ventilation and perfusion in humans.
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