Both gravity and non‐gravity dependent factors determine regional blood flow within the goat lung

Melsom, Morten Nissen; Flatebø, Torun; Kramer‐Johansen, Jo; Aulie, Åse; Sjaastad, Ø. V.; Iversen, Per Ole; Nicolaysen, Gunnar

doi:10.1111/j.1748-1716.1995.tb09872.x

Cited by 62 publications

(65 citation statements)

References 27 publications

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“…The size of these particles (10 -150 m) causes them to become trapped in the pulmonary microcirculation in proportion to regional blood flow, which has been confirmed with other measurement methods (52). A maximum dose of MAA corresponds to ϳ700,000 particles, which occludes Ͻ1 ϫ 10 Ϫ4 % of the pulmonary capillaries (Mallinckrodt Medical, Petten, The Netherlands); according to one manufacturer the particles have a biological half-life of 11 h (Mallinckrodt Medical).…”

Section: Radiotracers For Imaging Of Regional Blood Flowsupporting

confidence: 59%

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

Petersson

Sánchez-Crespo²,

Larsson³

et al. 2007

Journal of Applied Physiology

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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Section: Radiotracers For Imaging Of Regional Blood Flowsupporting

confidence: 59%

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

Petersson

Sánchez-Crespo²,

Larsson³

et al. 2007

Journal of Applied Physiology

120

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“…Additionally, if the body position changes appreciably, this gradient reorients in the appropriate direction relative to the forces of gravity (Chaliki et al, 2002;Romand et al, 1994;Takeda et al, 1987). However, it is important to note that in quadrupeds such as horses (Hlastala et al, 1996), goats (Melsom et al, 1995), dogs (Parker et al, 1995), sheep (Walther et al, 1997), pigs , and ponies (Jarvis et al, 1992), gravity may not be as important a determinant of pulmonary blood flow distribution because the posture of quadrupeds produces a relatively shorter vertical gradient compared with those of humans (Hughes, 1996). In contrast, baboons, like humans, spend most of their time in the upright posture and have remarkably similar pulmonary structures and physiology to humans, where gravity plays a significant role in pulmonary blood flow (Glenny et al, 1999).…”

Section: Effects Of Gravity On Pulmonary Circulationmentioning

confidence: 94%

Pulmonary Hemodynamics

Aggarwal¹,

Groß²,

Porcelli³

et al. 2015

Comparative Biology of the Normal Lung

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“…It has been shown that the number of trapped microsopheres in a piece of lung correlates closely to the pulmonary flow through that piece [9], and that the recovery of infused fluorescent-labelled microspheres is similar to that of radioactively labelled ones [ 101.…”

Section: Blood Flow Tracersmentioning

confidence: 99%

Time Course and Pattern of Pulmonary Flow Distribution following Unilateral Airway Occlusion in Sheep

et al. 1998

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1. Unilateral bronchial occlusion causes ipsilateral hypoxic pulmonary vasoconstriction, which shifts blood flow towards the other lung. We studied the time course of flow diversion following acute bronchial occlusion, and the temporal effect of the latter on blood gases and vertical distribution of blood flow within the two lungs. 2. Serial infusion of radioactive or fluorescent microspheres were given to each of seven adult standing sheep before, during occlusion of the left mainstem bronchus for up to 6 min, and after release of occlusion. Pulmonary and systemic arterial pressures were recorded continuously and arterial and mixed venous blood gases were determined intermittently. Post-mortem, the lungs were inflated, dried and cut into slices. Relative blood flow at the time of infusion was expressed as the weight-normalized intensity of each tracer in each slice or lung divided by the weight-normalized intensity in the two lungs. 3. Within 30 s, 1 min and 2 min after onset of occlusion, flow in the occluded lung had decreased to 68-84% (range), 51-78% and 43-79% respectively, of the initial value. In the contralateral lung, flow increased by 10-24%, 14-37% and 23-39% respectively. The distribution of flow along the gravitational axis within each lung varied widely between animals, both before and during occlusion. The during-occlusion profiles in the occluded lung differed from those in the non-occluded lung. In either lung, during-occlusion profiles could not be predicted with certainty from the pre-occlusion profiles. Two minutes post-occlusion, inter- and intra-lung flow distribution were nearly the same as before occlusion. Arterial oxygen tension fell in the first minute of occlusion, but never below 7.5 kPa, and increased slowly thereafter. Arterial carbon dioxide tension increased slightly throughout the occlusion period. No appreciable changes in systemic or pulmonary artery pressure were observed. Post-occlusion, arterial oxygen tension was still sub-normal, while carbon dioxide tension continued to increase. 4. We conclude that acute unilateral bronchial occlusion diverts blood flow within 30 s towards the contralateral lung. This rapidly occurring flow diversion prevents the development of severe arterial hypoxaemia. The variable and largely unpredictable distribution of blood flow in the hyperfused non-occluded lung might explain some of the gas-exchange abnormalities observed in physiologically hyperfused lungs and in patients with one hyperfused lung.

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Both gravity and non‐gravity dependent factors determine regional blood flow within the goat lung

Cited by 62 publications

References 27 publications

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

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

Pulmonary Hemodynamics

Time Course and Pattern of Pulmonary Flow Distribution following Unilateral Airway Occlusion in Sheep

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