Regulation of Regional Lung Perfusion by Nitric Oxide

Rimeika, D; Nyrén, Sven; Wiklund, Peter; Koskela, Lotta Renström; Tørring, Anders; Gustafsson, Lars E.; Larsson, Stig; Jacobsson, Hans; Lindahl, Sten G. E.; Wiklund, Claes U.

doi:10.1164/rccm.200312-1663oc

Cited by 29 publications

(34 citation statements)

References 41 publications

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“…Pulmonary vascular endothelium production of nitric oxide is substantially greater in the dorsal versus the ventral lung. 61 Also, because more lung tissue resides in the dorsal plane, there is more pulmonary vasculature available and a higher capacitance to accommodate cardiac output compared with the ventral lung, regardless of gravitational forces. Therefore, regional pulmonary vascular resistance would remain lower in the dorsal lung.…”

Section: Pulmonary Perfusion In Ppmentioning

confidence: 99%

A Comprehensive Review of Prone Position in ARDS

2015

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Prone position (PP) has been used since the 1970s to treat severe hypoxemia in patients with ARDS because of its effectiveness at improving gas exchange. Compared with the supine position (SP), placing patients in PP effects a more even tidal volume distribution, in part, by reversing the vertical pleural pressure gradient, which becomes more negative in the dorsal regions. PP also improves resting lung volume in the dorsocaudal regions by reducing the superimposed pressure of both the heart and the abdomen. In contrast, pulmonary perfusion remains preferentially distributed to the dorsal lung regions, thus improving overall alveolar ventilation/perfusion relationships. 1660RESPIRATORY CARE • NOVEMBER 2015 VOL 60 NO 11Moreover, the larger tissue mass suspended from a wider dorsal chest wall effects a more homogeneous distribution of pleural pressures throughout the lung that reduces abnormal strain and stress development. This is believed to ameliorate the severity or development of ventilator-induced lung injury and may partly explain why PP reduces mortality in severe ARDS. Over 40 years of clinical trials have consistently reported improved oxygenation in approximately 70% of subjects with ARDS. Early initiation of PP is more likely to improve oxygenation than initiation during the subacute phase. Maximal oxygenation improvement occurs over a wide time frame ranging from several hours to several days. Meta-analyses of randomized controlled trials suggest that PP provides a survival advantage only in patients with relatively severe ARDS (P aO 2 /F IO 2 <150 mm Hg). Moreover, survival is enhanced when patients are managed with a smaller tidal volume (<8 mL/kg), higher PEEP (10 -13 cm H 2 O), and longer duration of PP sessions (>10 -12 h/session). Combining adjunctive therapies (high PEEP, recruitment maneuvers, and inhaled vasodilators) with PP has an additive effect in improving oxygenation and may be particularly helpful in stabilizing gas exchange in very severe ARDS.

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Section: Pulmonary Perfusion In Ppmentioning

confidence: 99%

A Comprehensive Review of Prone Position in ARDS

2015

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“…In a recent study, Rimeika et al (70) used SPECT to demonstrate that local production of nitric oxide (NO) influences the distribution of lung blood flood in normal subjects. In the supine posture inhibition of NO synthase caused a redistribution of blood flow from dorsal to ventral regions.…”

Section: Active Regulation Of Lung Blood Flowmentioning

confidence: 99%

Physiological imaging of the lung: single-photon-emission computed tomography (SPECT)

Petersson

Sánchez-Crespo²,

Larsson³

et al. 2007

Journal of Applied Physiology

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120

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Petersson J, Sá nchez-Crespo A, Larsson SA, Mure M. Physiological imaging of the lung: single-photon-emission computed tomography (SPECT). J Appl Physiol 102: 468 -476, 2007. First published September 21, 2006; doi:10.1152/japplphysiol.00732.2006.-Emission tomography provides threedimensional, quantitative images of the distribution of radiotracers used to mark physiological, metabolic, or pathological processes. Quantitative single photon emission computed tomography (SPECT) requires correction for the imagedegrading effects due to photon attenuation and scatter. Phantom experiments have shown that radioactive concentrations can be assessed within some percentage of the true value when relevant corrections are applied. SPECT is widely spread, and radiotracers are available that are easy to use and comparably inexpensive. Compared with other methods, SPECT suffers from a lower spatial resolution, and the time required for image acquisition is longer than for some alternative methods. In contrast to some other methods, SPECT allows simultaneous imaging of more than one process, e.g., both regional blood flow and ventilation, for the whole lung. SPECT has been used to explore the influence of posture and clinical interventions on the spatial distribution of lung blood flow and ventilation. Lung blood flow is typically imaged using macroaggregates of albumin. Both radioactive gases and particulate aerosols labeled with radioactivity have been used for imaging of regional ventilation. However, all radiotracers are not equally suited for quantitative measurements; all have specific advantages and limitations. With SPECT, both blood flow and ventilation can be marked with radiotracers that remain fixed in the lung tissue, which allows tracer administration during conditions different from those at image registration. All SPECT methods have specific features that result from the used radiotracer, the manner in which it is administered, and how images are registered and analyzed. respiratory physiology; regional blood flow; pulmonary ventilation; pulmonary gas exchange; radionuclide imaging THE NONUNIFORM DISTRIBUTIONS of regional lung blood flow and ventilation were first demonstrated utilizing radioactive tracers (radiotracers) and external scintillation detectors that registered the distribution of radioactivity within the lung (10,14,43,93). Later the development of the gamma camera allowed twodimensional imaging of the distribution of radiotracers (58). In the mid to late 1970s, both single-photon-emission computed tomography (SPECT) and positron emission tomography (PET) were developed, offering three-dimensional images of the in vivo distribution of radioactivity. These techniques can be used to study, for example, the three-dimensional distribution of regional blood flow or regional ventilation with a high spatial resolution. In this article we will first briefly explain the principles and characteristics of the SPECT method and second review studies that exemplifies how SPECT has been used to increase our unde...

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“…Furthermore, if NO was formed preferentially in dorsal lung as suggested by prior research (Pelletier et al, 1998 andRimeika et al, 2004), redistribution of Q to ventral lung should result with blockage of cNOS. However, we found a small but significant redistribution of Q from ventral to dorsal regions, Figure 10, contrary to what would be expected (Pelletier et al, 1998, Rimeika et al, 2004, Rimeika et al, 2006. There was no difference in total V/Q heterogeneity as a result of this small redistribution, which was also supported by a preserved PaO 2 and (A-a)O 2 difference.…”

Section: Minimal Change In V/q Distributions By L-namementioning

confidence: 84%

“…Beck and Rehder (Beck and Rehder, 1986) showed that vascular conductance was higher in dorsal lung in dogs in the supine, lateral and head-up positions, but the prone position was not examined. Evidence for uneven formation of NO in the lung was provided by in vitro studies showing greater eNOS activity in dorsal than in ventral lung regions in animals and humans, and similar regional differences in NO-mediated vasorelaxation in equine and porcine pulmonary arteries (Pelletier et al, 1998, Rimeika 2004et al, Rimeika et al, 2006. Rimeika et al (Rimeika et al, 2004) tried to confirm this by examining humans with SPECT in the prone and supine positions after inhibition of NO production.…”

Section: Endogenous No and V/q Matching Paper Iv: Inhibition Of Constmentioning

confidence: 99%

“…Evidence for uneven formation of NO in the lung was provided by in vitro studies showing greater eNOS activity in dorsal than in ventral lung regions in animals and humans, and similar regional differences in NO-mediated vasorelaxation in equine and porcine pulmonary arteries (Pelletier et al, 1998, Rimeika 2004et al, Rimeika et al, 2006. Rimeika et al (Rimeika et al, 2004) tried to confirm this by examining humans with SPECT in the prone and supine positions after inhibition of NO production. They found a small redistribution of Q to nondependent ventral lung in the supine position after inhibition of nitric oxide synthase (NOS), but in the prone position there was no redistribution.…”

Section: Endogenous No and V/q Matching Paper Iv: Inhibition Of Constmentioning

confidence: 99%

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Gas Exchange in the Normal Lung : Experimental studies on the effects of positive end-expiratory pressure and body position

Johansson¹

2014

Linköping University Medical Dissertations

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BACKGROUND:The principal function of the lung is gas exchange requiring adequate ventilation and perfusion at the level of the alveoli. The efficiency of gas exchange is depending on the distributions of regional ventilation (V) and pulmonary blood flow (Q) and their correlation. AIMS:To validate a high-resolution method to quantify regional V and to investigate the Radioactive microspheres, 15 m in diameter, were used for determining regional Q. Nitric oxide synthase (NOS) was inhibited with Nω-nitro-L-arginine methyl ester (L-NAME) to evaluate the role of NO on regional V/Q matching. The right lung was dried at total lung capacity and diced in approx. 1000 regions tracking the spatial location of each region. CONCLUSION: There were marked differences in redistribution of regional ventilation and regional pulmonary blood flow between prone and supine position when PEEP was applied. RESULTS:NO was not an active mechanism for V/Q matching in normal sheep lungs. VII List of original papershis thesis is based on the following four papers, which will be referred to by their Roman numerals: I.Positive end-expiratory pressure affects regional redistribution of ventilation differently in prone and supine sheep.

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Regulation of Regional Lung Perfusion by Nitric Oxide

Cited by 29 publications

References 41 publications

A Comprehensive Review of Prone Position in ARDS

A Comprehensive Review of Prone Position in ARDS

Physiological imaging of the lung: single-photon-emission computed tomography (SPECT)

Gas Exchange in the Normal Lung : Experimental studies on the effects of positive end-expiratory pressure and body position

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