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J Appl Physiol 86: 1135-1141, 1999;
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Vol. 86, Issue 4, 1135-1141, April 1999

Pulmonary perfusion is more uniform in the prone than in the supine position: scintigraphy in healthy humans

Sven Nyrén1, Margareta Mure2, Hans Jacobsson3, Stig A. Larsson3, and Sten G. E. Lindahl2

Departments of 1 Diagnostic Radiology, 2 Anesthesiology and Intensive Care, and 3 Hospital Physics, Karolinska Hospital and Institute, SE-171 76 Stockholm, Sweden


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

The main purpose of this study was to find out whether the dominant dorsal lung perfusion while supine changes to a dominant ventral lung perfusion while prone. Regional distribution of pulmonary blood flow was determined in 10 healthy volunteers. The subjects were studied in both prone and supine positions with and without lung distension caused by 10 cmH2O of continuous positive airway pressure (CPAP). Radiolabeled macroaggregates of albumin, rapidly trapped by pulmonary capillaries in proportion to blood flow, were injected intravenously. Tomographic gamma camera examinations (single-photon-emission computed tomography) were performed after injections in the different positions. All data acquisitions were made with the subject in the supine position. CPAP enhanced perfusion differences along the gravitational axis, which was more pronounced in the supine than prone position. Diaphragmatic sections of the lung had a more uniform pulmonary blood flow distribution in the prone than supine position during both normal and CPAP breathing. It was concluded that the dominant dorsal lung perfusion observed when the subjects were supine was not changed into a dominant ventral lung perfusion when the subjects were prone. Lung perfusion was more uniformly distributed in the prone compared with in the supine position, a difference that was more marked during total lung distension (CPAP) than during normal breathing.

continuous positive airway pressure; gravity dependence; human volunteers; lung perfusion; prone position; single-photon-emission computed tomography; supine position


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

RECENTLY, A DRAMATICALLY IMPROVED gas exchange was reported in mechanically ventilated patients with severe acute lung insufficiency when they were treated in the prone position (19). Similar findings were published 20 years ago (21) and were later confirmed by others (1, 6, 14, 15, 18). These clinical studies raise questions on underlying mechanisms. Regional differences in lung perfusion resulting in improved ventilation-perfusion ratios in the prone position may be one explanation (23). The traditional and common theory (3, 5, 12, 13, 28), that pulmonary blood flow largely follows gravitational forces, resulting in higher perfusion to dependent parts of the lungs irrespective of anatomic regions, has now been challenged (1, 4, 7-9, 14, 17).

To further investigate this, lung perfusion scintigraphy was performed in healthy volunteers, using tomographic gamma camera examination [single-photon-emission computed tomography (SPECT)]. Regional pulmonary perfusion was investigated after injection of technetium-99m (99mTc)-labeled macroaggregates of albumin in both prone and supine positions at normal breathing and at lung distension caused by a continuous positive airway pressure (CPAP) of 10 cmH2O. In a supine posture, atelectasis could develop in dorsal parts of the lungs. Using CPAP would minimize that risk and maintain similar lung volumes between supine and prone postures. Transverse tomographic sections representing lung perfusion at the different conditions were achieved and compared. The primary purpose of the investigation was to find out whether the dominant dorsal lung perfusion in supine positions changes to a dominant ventral perfusion when the position becomes prone. We also wanted to examine whether lung distension due to CPAP changed positional variations in lung perfusion.


    METHODS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Subjects. Ten healthy volunteers, five men and five women, were included in this investigation. Their mean age was 39 yr (range 24-57 yr). Seven subjects underwent examination at both normal breathing and at a CPAP of 10 cmH2O, one at normal breathing only, and two at CPAP only. The seven subjects, investigated during both CPAP and normal breathing, were examined on two different occasions. The study was approved by the local ethical and radiation protection committees. Written information about the entire procedure was given to all volunteers.

Experimental design. All examinations were performed as illustrated in Fig. 1. With the subject in the prone position on the gamma camera couch, 50 MBq 99mTc-labeled macroaggregates of albumin were injected in the right arm via a vein catheter. Some minutes after the completed injection, the subject turned to the supine position, and a SPECT acquisition of the lungs was made (acquisition 1). This was followed by another injection of 100 MBq of the tracer and an identical SPECT acquisition with the subject in the supine position (acquisition 2).


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  		Fig. 1.   Schematic presentation of study sequence for single-photon-emission computed tomography (SPECT) assessment of pulmonary perfusion distribution in prone and supine positions using iv injections of 99mTc-labeled albumin macroaggregates [administrations (Adm) 1 and 2]. At each examination (SPECT 1 and 2), both injections of radiotracer were made at either normal breathing or continuous positive airway pressure (CPAP).

The volunteers studied during CPAP breathing were also examined 2 wk later during normal breathing. The CPAP of 10 cmH2O was achieved via a modification of an Engström 2000 ventilator (Datex Engström, Solna, Sweden). Air was used, and a tight seal was accomplished by the use of a specialized face mask. Mouth pressures were recorded continuously thoughout the CPAP breathing. There was a 10-min equilibration period between application of CPAP breathing and tracer injection. SPECT acquisitions were all made at normal breathing without CPAP, but both injections of the radiotracer were made at CPAP breathing (Fig. 1). From the point of turning to the supine position and to the end of the entire examination, the subject remained supine and stable in relation to the gamma camera, to allow subtraction between the two acquisitions.

Radiotracer. Macroaggregates of human serum albumin were labeled with 99mTc (TechneScan LyoMAA, Mallinckrodt Medical, Petten, The Netherlands) according to the clinical routine. The manufacturer guarantees that 95% of the particles are between 10 and 100 µm. No particles are larger than 150 µm (largest diameter). The preparation was made so that 50 MBq represented ~1.25 × 105 particles.

SPECT examination. A three-headed Triad XLT gamma camera (Trionix, Twinsburg, OH) with high-resolution, low-energy collimators was used. Each acquisition was performed with 90 steps during a 360° rotation and during a total examination time of 11 min. A 128 × 128 matrix with a pixel size of 3.6 × 3.6 mm2 was used for data acquisition and reconstruction. Each transverse row of the projection matrix was used for reconstruction, thus giving sections with a nominal voxel (volume element) size of 3.6 × 3.6 × 3.6 mm3. To match the spatial resolution of the system (~15 mm, full-width half-maximum), a weighing of the actual row for reconstruction was performed, with the two closest consecutive rows on each side before filtering and reconstruction. The weighing kernel was 1, 2, 5, 2, and 1, with a weight of 5 given to the central row. Reconstructions were made, respectively, from data obtained during acquisition 1 (representing the perfusion in the prone position) and that obtained by subtracting acquisition 1 data from acquisition 2 (representing the perfusion in the supine position).

Data analysis. The activity distribution in the right lung was evaluated at three different levels. Therefore, the lateral two-dimensional reprojected image of the right lung was first divided into five segments of equal height from the top to the base, where the last segment was omitted. At each of the three borderlines between the remaining four segments, three consecutive 3.6-mm-thick transverse sections were added, thus giving three ~10-mm-thick sections. The location of the section closest to the upper part of the lung was denoted "apical," the next "intermediate," and the third, closest to the base, "diaphragmatic." In no subject did the diaphragm interfere with the diaphragmatic section.

The activity distribution along the ventral-dorsal direction of these three selected transverse sections of the right lung was assessed by plotting activity profiles of a 40-mm-wide row of voxel data at the center of each section (Fig. 2). Each curve was subsequently "divided" into three equal parts, with average data in each part representing the activity (in percentage of the total in the actual 40-mm row) in the ventral, mid-, and dorsal region of the section.


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  		Fig. 2.   Principle for evaluation of regional perfusion in right lung. Definition of 3 transverse sectional images (left), definition of a ventral-dorsal slice (middle; stippled, hatched, and open section of bar: ventral, mid-, and dorsal region, respectively), and construction of activity profile at various levels (right) are shown. Examination was performed with subject in supine position.

Nuclear medicine images suffer from low spatial resolution and disturbing influence from attenuation and contribution of unwanted scattered photons. Therefore, an accurate (mm) definition of an organ outline may often be difficult to make. In this investigation, we made use of an approximative method, whereby we defined the outline as the intersection between the mean of the data in the 128-voxel-long profile and the actual activity profile. These defined border outlines agreed with those from visual inspection.

By using this method, identical lung portions were assessed in each individual at the two registrations. This allowed comparison of regional perfusion at two different postural positions. Nine examinations comparing the prone and supine positions at CPAP and eight similar examinations at normal breathing were performed. Similar analyses were made comparing CPAP with normal breathing.

Statistics. Mean and SD values of regional activities across subjects were calculated. Comparisons between the percent activity of the same portion of the slice were made by the standard double-tailed paired and unpaired t-test. P < 0.05 was considered statistically significant.


    RESULTS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

A representative example of activity profiles in the gravitational plane for both lungs together from one individual during normal breathing and CPAP is shown in Fig. 3. At CPAP breathing, the distribution of perfusion was more uniform in the prone than in the supine position (Figs. 3 and 4). The corresponding profiles obtained at normal breathing are similar but less pronounced (Fig. 3).


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  		Fig. 3.   Activity profiles in ventral-dorsal direction (gravitational plane) of both lungs of a representative healthy volunteer. Left: entire lung perfusion at normal breathing; right, entire lung perfusion at CPAP.


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  		Fig. 4.   Representative transverse tomographic (SPECT) pictures of diaphragmatic sections of both lungs in a volunteer (same as in Fig. 3) representing perfusion in prone (left) and supine positions (right) at normal breathing (top) and CPAP (bottom).

The following data analysis was done on the slices made in the three transverse sections (apical, intermediate, and diaphragmatic) of the right lung (Fig. 2). From each of these slices, the activity in the ventral-dorsal direction (gravitational plane) was evaluated.

Lung perfusion in the prone and supine positions. During normal breathing, there were no differences between prone and supine positions in mid-, dependent, or nondependent vertical regions of apical and intermediate sections of the lung. In the diaphragmatic section, dependent regions were better perfused in the supine than in the prone position. The opposite was observed for nondependent regions, indicating a more uniformly distributed lung perfusion in diaphragmatic sections of the lung while the subjects were in the prone position (Fig. 5).


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  		Fig. 5.   Analysis of effect of postural position on distribution of lung perfusion in right lung at normal breathing (left; n = 8) and at CPAP (right; n = 9). Mean percent activity of identical slice portion was compared between prone and supine positions at 3 different lung levels (apical, intermediate, and diaphragmatic). For statistical analysis, standard double-tailed paired t-test was used: NS, not significant, * 0.01 < P < 0.05, ** 0.001 < P < 0.01.

During CPAP breathing, as during normal breathing, there were no differences between prone and supine positions in the apical and the intermediate sections of the lung (Fig. 5). In the diaphragmatic section of the lung, perfusion was greater in dependent regions while the subjects were in the supine position (P < 0.01, Fig. 5). In this lung section, perfusion decreased from 49 ± 7 (SD) % in dependent to 16 ± 4% in nondependent regions in the supine position and only from 39 ± 4% in dependent to 24 ± 5% in nondependent regions in the prone position.

Normal breathing vs. CPAP in the prone posture. In the prone position lung perfusion was more uniformly distributed during normal breathing than during CPAP. In the apical section of the lung, the perfusion was similar during CPAP and normal breathing in dependent and nondependent regions. Intermediate and diaphragmatic sections of the lung had, during CPAP, a greater perfusion in dependent regions (P < 0.01, Fig. 6). Hence lung perfusion was more uniform during normal breathing in the prone position.


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  		Fig. 6.   Analysis of effect of CPAP on distribution of lung perfusion in right lung while subject was in prone (left) or supine position (right). Mean percent activity of identical slice portion was compared between CPAP and normal breathing at 3 different lung levels. For statistical analysis, standard double-tailed unpaired t-test was used: * 0.01 <=  P < 0.05, ** 0.001 <=  P < 0.01, *** P < 0.001.

Normal breathing vs. CPAP in the supine posture. In the supine position, the CPAP effect on gravitational blood flow dependence was more pronounced, particularly in the diaphragmatic section of the lung, compared with normal breathing (P < 0.001, Fig. 6). During CPAP breathing, perfusion of the diaphragmatic section of the lung decreased from 49 ± 7% in dependent to 16 ± 4% in nondependent regions (Fig. 6). Corresponding values during normal breathing only decreased from 38 ± 3 to 25 ± 3%.


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

The main finding in this study was that the dominant dorsal lung perfusion in the supine position did not change into a dominant ventral perfusion in the prone position. Lung perfusion was more uniformly distributed in the prone compared with the supine position. CPAP breathing enhanced perfusion differences along the gravitational axis, a result that was more pronounced in the supine than in the prone position.

Methodological issues. Perfusion scintigraphy of the lung (SPECT) is accomplished by microembolization of radionuclide-labeled particles in the arterial pulmonary circulation. It is based on the concept that the number of particles that are trapped in a particular lung volume is proportional to the pulmonary arterial blood flow to that region (16, 26). Studies comparing the distribution of N,N,N'-trimethyl-N-[2-hydroxy-3-methyl-5-iodobenzyl]-1,3-propanediamine, a diamine with a near-complete first-pass extraction by the lungs, have shown that the principle used in the present study reflects regional pulmonary blood flow (17). SPECT is now an established technique for tomographic investigations of radiotracer distribution, allowing reconstruction of sectional images in any plane. Several previous investigations on the present topic have also been based on this technique (10, 14, 22, 25).

The subtraction technique used in the present study was appropriate because the removal of albumin macroaggregates of the actual size is very slow (24). However, increased image noise affects our subtracted data. This unwanted effect was reduced by injecting twice as much radiotracer before acquisition 2. Another problem, photon scattering, may explain why a higher activity was measured in midlung regions compared with in dependent and nondependent regions, in the apical and intermediate sections of the lung (Figs. 5 and 6). Yet another explanation is that perfusion is higher in midregions of the lung, which are closer to the hilus. Walther et al. (27) found that the blood flow was larger in hilar than in peripheral regions in awake prone sheep.

The present study was designed to answer whether the pattern for perfusion varies between prone and supine postures. The experimental design, including assessment of the same individual at the two occasions, is considered adequate to reduce biological variations and to allow evaluation of results by using paired comparisons of perfusion at different postural positions (Fig. 5). Evaluations of CPAP influence (Fig. 6) could, however, only be carried out by unpaired comparisons.

Anatomic considerations. To assess the perfusion, the right lung was chosen to avoid interference with the heart. Comparing the perfusion in prone and supine positions, there was no difference in the apical and intermediate sections (Fig. 5), and there was no effect of CPAP in the apical section (Fig. 6), whereas differences occurred in the diaphragmatic sections. A similar discrepancy between various levels of the lung has also been reported previously (13). It may be explained by the fact that, for anatomic reasons, upper ventral-dorsal slices are too short for gravitational influences to be expressed, compared with slices from diaphragmatic sections of the lung with a longer distance in the gravitational plane.

The evaluation of the three lung sections was based on small-volume units of identical size and shape, without consideration for the total perfusion or configuration of the lung. This allowed the direct comparison of activity between different pulmonary regions, i.e., ventral vs. dorsal portions of the lung. When the net effect of all lung sections is given, it must be governed by the characteristics of the diaphragmatic lung sections, because they strongly dominate quantitatively.

Distribution of lung perfusion. It is known that lung volumes increase at a CPAP of 10 cmH2O. It is also known that large lung volumes, above functional residual capacity, are related to increased vascular resistance of small vessels, creating zone 1 and zone 2 conditions in nondependent regions (12, 28). The West model of blood flow distribution within the lung, which is based on gravity (28), can no longer act as the only explanatory model for lung perfusion. In contrast, several reports from experiments in various quadruped animals, in baboons as well as in upright humans, have indicated that gravity is a minor rather than a major determinant of regional pulmonary blood flow. Instead, intrinsic factors, possibly regional differences in vascular conductance, may be of importance (2, 4, 7-11, 20, 22, 29). These opinions are also supported by results in the present study. The blood flow to dependent lung regions, particularly in the diaphragmatic sections of the lungs, was, during normal breathing, relatively greater in the supine than in the prone position. The more uniformly distributed perfusion between dependent and nondependent regions in the prone position is in accordance with gravity being only of minor importance for determination of regional lung perfusion (7). The well-maintained perfusion in nondependent lung regions in the prone position supports the finding of Beck and Rehder (4), who, in an in vitro study of dog lungs, found that there were regions with higher vascular conductance. These regions were always located dorsocaudally. This is purposeful in dogs, which walk on four legs, where gravity acts on blood flow in one direction, to be offset by higher vascular conductance dorsocaudally to achieve an even lung perfusion. In the present series, the prone position clearly resulted in a more even lung perfusion, which is in conformity with the reasoning above on the basis of Beck and Rehder's findings in dogs. The question is whether regional variation in resistance to blood flow exists also in upright humans. In light of evolution, such similarities between species are not surprising, and certainly these matters must be further elucidated in future studies.

At CPAP, lung volumes increase. In the supine position, blood flow is enhanced to dependent parts of the lung in the diaphragmatic section. An explanation for this could be increased lung regions in zone 1 and zone 2 conditions in nondependent regions (28). This means more blood to dorsal regions while in the supine position. Higher vascular conductance in the dorsocaudal regions, independent of posture, is probably the reason the effect of gravity dependence on blood flow distribution was more pronounced in the supine than in the prone position during CPAP breathing compared with normal breathing. Still, however, lung perfusion was more homogeneous in the prone than the supine position (Figs. 5 and 6). From a clinical point of view, this is of interest for patients suffering from lung insufficiency demanding mechanical ventilation. The prime clinical goal for these patients is to reach the best match of ventilation and perfusion to get an optimal gas exchange. A major complication is that, in anesthetized, mechanically ventilated patients, distribution of inspired gas to nondependent lung regions is greater (25). At the same time, as shown in this study, positive airway pressures result in a higher blood flow to dependent regions, particularly when in the supine position. The summation of these effects reinforces a ventilation-perfusion mismatch in the supine position. In the prone position, however, the more uniformly distributed lung perfusion, also during positive airway pressures, offers conditions for better matching, with the resultant improved gas exchange.

It was concluded that pulmonary blood flow distribution during normal breathing was more uniform in the prone than in the supine position. The combination of gravity and other factors, such as vascular anatomy, results in a greater vertical gradient of perfusion in the supine compared with in the prone posture. Positive pressure breathing at a CPAP of 10 cmH2O resulted in a more marked gravity dependence on blood flow in the supine position and now also, but to a much lesser degree, while in the prone position. Because the distribution of inspired gas at positive airway pressure preferably goes to nondependent lung regions, ventilation-perfusion matching during positive pressure breathing is most probably less favorable in the supine than in the prone position.


    ACKNOWLEDGEMENTS

The authors are greatly indebted to Anne-Marie Danielsson, Anette Ebberyd, Ingeborg Gottlieb-Inacio, Robert Hatherly, Ringvor Hägglöf, and Shahrokh Kimiaei for excellent technical assistance.


    FOOTNOTES

This work was financed in part by grants from the Swedish Medical Research Council (project no. 17X-10401).

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Address for reprint requests and other correspondence: M. Mure, Dept. of Anesthesiology and Intensive Care, Karolinska Hospital, SE-171 76 Stockholm, Sweden (E-mail: m.mure{at}kir.ks.se).

Received 1 June 1998; accepted in final form 27 October 1998.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Albert, R. K., D. Leasa, M. Sanderson, H. T. Robertson, and M. P. Hlastala. The prone position improves arterial oxygenation and reduces shunt in oleic-acid-induced acute lung injury. Am. Rev. Respir. Dis. 135: 628-633, 1987[Medline].

2.   Amis, T. C., H. A. Jones, and J. M. B Hughes. Effect of posture on inter-regional distribution of pulmonary perfusion and ventilation-perfusion ratios in man. Respir. Physiol. 56: 169-182, 1984[Medline].

3.   Ball, W. C., P. B. Stewart, L. G. S. Newsham, and D. V. Bates. Regional pulmonary function studied with xenon. J. Clin. Invest. 41: 519-531, 1962.

4.   Beck, K. C., and K. Rehder. Differences in regional vascular conductances in isolated dog lungs. J. Appl. Physiol. 61: 530-538, 1986[Abstract/Free Full Text].

5.   Bryan, A. C., L. G. Bentivoglio, F. Beerel, H. MacLeish, A. Zidulka, and D. V. Bates. Factors affecting regional distribution of ventilation and perfusion in the lung. J. Appl. Physiol. 19: 395-402, 1964[Abstract/Free Full Text].

6.   Douglas, W. W., K. Rehder, F. M. Beynen, A. D. Sessler, and H. M. Marsh. Improved oxygenation in patients with acute respiratory failure: the prone position. Am. Rev. Respir. Dis. 115: 559-566, 1977[Medline].

7.   Glenny, R. W., S. Bernard, H. T. Robertson, and M. P. Hlastala. Gravity is an important but minor determinant of pulmonary blood flow heterogeneity in the baboon (Abstract). FASEB J. 11: A344, 1997.

8.   Glenny, R. W., W. J. E. Lamm, R. K. Albert, and H. T. Robertson. Gravity is a minor determinant of pulmonary blood flow distribution. J. Appl. Physiol. 71: 620-629, 1991[Abstract/Free Full Text].

9.   Glenny, R. W., and H. T. Robertson. Fractal properties of pulmonary blood flow: characterization of spatial heterogeneity. J. Appl. Physiol. 69: 532-545, 1990[Abstract/Free Full Text].

10.   Hakim, T. S., R. Lisbona, and G. W. Dean. Gravity-independent inequality in pulmonary blood flow in humans. J. Appl. Physiol. 63: 1114-1121, 1987[Abstract/Free Full Text].

11.   Hogg, J. C., P. Holst, P. Corry, F. Ruff, E. Housley, and E. Morris. Effect of regional lung expansion and body position on pulmonary perfusion in dogs. J. Appl. Physiol. 31: 97-101, 1971[Free Full Text].

12.   Hughes, J. M. B., J. B. Glazier, J. E. Maloney, and J. B. West. Effect of lung volume on the distribution of pulmonary blood flow in man. Respir. Physiol. 4: 58-72, 1968[Medline].

13.   Kaneko, K., J. Milic-Emili, M. B. Dolovich, A. Dawson, and D. V. Bates. Regional distribution of ventilation and perfusion as a function of body position. J. Appl. Physiol. 21: 767-777, 1966[Free Full Text].

14.   Lamm, W. J. E., M. M. Graham, and R. K. Albert. Mechanism by which the prone position improves oxygenation in acute lung injury. Am. J. Respir. Crit. Care Med. 150: 184-193, 1994[Abstract].

15.   Langer, M., D. Mascheroni, R. Marcolin, and L. Gattinoni. The prone position in ARDS. A clinical study. Chest 94: 103-107, 1988[Abstract/Free Full Text].

16.   Lowe, V. J., and H. D. Sostman. Pulmonary embolism. In: Nuclear Medicine in Clinical Diagnosis and Treatment, edited by I. P. C. Murray, and P. J. Ell. London: Churchill Livingstone, 1994, p. 29-46.

17.   Melsom, M. N., T. Flatebø, J. Kramer-Johansen, A. Aulie, Ø. V. Sjaastad, P. O. Iversen, and G. Nicolaysen. Both gravity and non-gravity dependent factors determine regional blood flow within the goat lung. Acta Physiol. Scand. 153: 343-353, 1995[Medline].

18.   Murdoch, I. A., and M. O. Storman. Improved arterial oxygenation in children with the adult respiratory distress syndrome: the prone position. Acta Paedriatica 83: 1043-1046, 1994.

19.   Mure, M., C.-R. Martling, and S. G. E. Lindahl. Dramatic effect on oxygenation in patients with severe acute lung insufficiency treated in the prone position. Crit. Care Med. 25: 1539-1544, 1997[Medline].

20.   Orphanidou, D., J. M. B. Hughes, M. J. Myers, A.-R. Al-Suhali, and B. Henderson. Tomography of regional ventilation and perfusion using krypton 81m in normal subjects and asthmatic patients. Thorax 41: 542-551, 1986[Abstract].

21.   Piehl, M. A., and R. S. Brown. Use of extreme position changes in acute respiratory failure. Crit. Care Med. 4: 13-14, 1976[Medline].

22.   Reed, J. H., and E. H. Wood. Effect of body position on vertical distribution of pulmonary blood flow. J. Appl. Physiol. 28: 303-311, 1970[Free Full Text].

23.   Rehder, K., T. J. Knopp, and A. D. Sessler. Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed prone man. J. Appl. Physiol. 45: 528-535, 1978[Abstract/Free Full Text].

24.   Taplin, G. V., and N. S. MacDonald. Radiochemistry of macroaggregated albumin and newer lung scanning agents. Semin. Nucl. Med. 1: 132-152, 1971[Medline].

25.   Tokics, L., G. Hedenstierna, L. Svensson, B. Brismar, T. Cederlund, H. Lindquist, and Å. Strandberg. V/Q distribution and correlation to atelectasis in anesthetized paralyzed humans. J. Appl. Physiol. 81: 1822-1833, 1996[Abstract/Free Full Text].

26.   Wagner, H. N., Jr. Regional ventilation and perfusion. In: Principles of Nuclear Medicine, edited by H. N. Wagner, Jr., Z. Szabo, and J. W. Buchanan. Philadelphia, PA: Saunders, 1995, p. 881-895.

27.   Walther, S. M., K. B. Domino, R. W. Glenny, N. L. Polissar, and M. P. Hlastala. Pulmonary blood flow distribution has a hilar-to-peripheral gradient in awake, prone sheep. J. Appl. Physiol. 82: 678-685, 1997[Abstract/Free Full Text].

28.   West, J. B., C. T. Dollery, and A. Naimark. Distribution of blood flow in isolated lung: relation to vascular and alveolar pressures. J. Appl. Physiol. 19: 713-724, 1964[Abstract/Free Full Text].

29.   Wiener, C. W., W. Kirk, and R. K. Albert. Prone position reverses gravitational distribution of perfusion in dog lungs with oleic acid-induced injury. J. Appl. Physiol. 68: 1386-1392, 1990[Abstract/Free Full Text].

J APPL PHYSIOL 86(4):1135-1141
8570-7587/99 $5.00 Copyright © 1999 the American Physiological Society


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 J. Appl. Physiol.Home page
J. Petersson, A. Sanchez-Crespo, S. A. Larsson, and M. Mure
Physiological imaging of the lung: single-photon-emission computed tomography (SPECT)
J Appl Physiol, January 1, 2007; 102(1): 468 - 476.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
R. S. Harris and D. P. Schuster
Visualizing lung function with positron emission tomography
J Appl Physiol, January 1, 2007; 102(1): 448 - 458.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
J. Petersson, M. Rohdin, A. Sanchez-Crespo, S. Nyren, H. Jacobsson, S. A. Larsson, S. G. E. Lindahl, D. Linnarsson, R. W. Glenny, and M. Mure
Paradoxical redistribution of pulmonary blood flow in prone and supine humans exposed to hypergravity
J Appl Physiol, January 1, 2006; 100(1): 240 - 248.
[Abstract] [Full Text] [PDF]

Home page
 Proc Am Thorac SocHome page
E. A. Hoffman and D. Chon
Computed Tomography Studies of Lung Ventilation and Perfusion
Proceedings of the ATS, December 1, 2005; 2(6): 492 - 498.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
S. M. Walther, M. J. Johansson, T. Flatebo, A. Nicolaysen, and G. Nicolaysen
Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung
J Appl Physiol, September 1, 2005; 99(3): 909 - 914.
[Abstract] [Full Text] [PDF]

Home page
 ChestHome page
F.-C. Lin, Y.-C. Chen, H.-I. Chang, and S.-C. Chang
Effect of Body Position on Gas Exchange in Patients With Idiopathic Pulmonary Alveolar Proteinosis: No Benefit of Prone Positioning
Chest, March 1, 2005; 127(3): 1058 - 1064.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
D. Rimeika, S. Nyren, N. P. Wiklund, L. R. Koskela, A. Torring, L. E. Gustafsson, S. A. Larsson, H. Jacobsson, S. G. E. Lindahl, and C. U. Wiklund
Regulation of Regional Lung Perfusion by Nitric Oxide
Am. J. Respir. Crit. Care Med., August 15, 2004; 170(4): 450 - 455.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
G. Peces-Barba, M. J. Rodriguez-Nieto, S. Verbanck, M. Paiva, and N. Gonzalez-Mangado
Lower pulmonary diffusing capacity in the prone vs. supine posture
J Appl Physiol, May 1, 2004; 96(5): 1937 - 1942.
[Abstract] [Full Text] [PDF]

Home page
 RadiologyHome page
C. Fink, M. Puderbach, M. Bock, K.-P. Lodemann, I. Zuna, A. Schmahl, S. Delorme, and H.-U. Kauczor
Regional Lung Perfusion: Assessment with Partially Parallel Three-dimensional MR Imaging
Radiology, April 1, 2004; 231(1): 175 - 184.
[Abstract] [Full Text] [PDF]

Home page
 ChestHome page
A. F. Broccard
Prone Position in ARDS: Are We Looking at a Half-Empty or Half-Full Glass?
Chest, May 1, 2003; 123(5): 1334 - 1336.
[Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
G. Musch, J. D. H. Layfield, R. S. Harris, M. F. V. Melo, T. Winkler, R. J. Callahan, A. J. Fischman, and J. G. Venegas
Topographical distribution of pulmonary perfusion and ventilation, assessed by PET in supine and prone humans
J Appl Physiol, November 1, 2002; 93(5): 1841 - 1851.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
M. J. Rodriguez-Nieto, G. Peces-Barba, N. Gonzalez Mangado, M. Paiva, and S. Verbanck
Similar ventilation distribution in normal subjects prone and supine during tidal breathing
J Appl Physiol, February 1, 2002; 92(2): 622 - 626.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
M. Mure, K. B. Domino, S. G. E. Lindahl, M. P. Hlastala, W. A. Altemeier, and R. W. Glenny
Regional ventilation-perfusion distribution is more uniform in the prone position
J Appl Physiol, March 1, 2000; 88(3): 1076 - 1083.
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