51
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van der Zee P, Gommers D. Recruitment Maneuvers and Higher PEEP, the So-Called Open Lung Concept, in Patients with ARDS. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2019; 23:73. [PMID: 30850004 PMCID: PMC6408810 DOI: 10.1186/s13054-019-2365-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.
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Affiliation(s)
- Philip van der Zee
- Department of Adult Intensive Care Medicine, Erasmus MC, Erasmus University Rotterdam, Rotterdam, The Netherlands
| | - Diederik Gommers
- Department of Adult Intensive Care Medicine, Erasmus MC, Erasmus University Rotterdam, Rotterdam, The Netherlands.
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52
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Characterizing Spatial Lung Function for Esophageal Cancer Patients Undergoing Radiation Therapy. Int J Radiat Oncol Biol Phys 2018; 103:738-746. [PMID: 30612962 DOI: 10.1016/j.ijrobp.2018.10.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 10/11/2018] [Accepted: 10/19/2018] [Indexed: 12/25/2022]
Abstract
PURPOSE Patients with esophageal cancer treated with chemoradiation and surgery can develop pulmonary complications. Four-dimensional computed tomography-ventilation (4DCT-ventilation) is a developing imaging modality that uses 4DCT data to calculate lung ventilation. 4DCT-ventilation has been studied in the lung-cancer population but has yet to be extended to patients with esophageal cancer. The purpose of this study was to characterize 4DCT-ventilation-based spatial lung function for patients with esophageal cancer. METHODS AND MATERIALS Thirty-five patients with esophageal cancer who underwent 4DCT scans participated in the study. A 4DCT-ventilation map was calculated using the patient's 4DCT imaging and a density change-based algorithm. To assess each patient's ventilation profile, radiologist interpretations and quantitative metrics were used. A radiologist interpreted the 4DCT-ventilation images for lobar-based defects and gravity-dependent atelectasis. The 4DCT-ventilation maps were reduced to single metrics intended to reflect the degree of ventilation heterogeneity. The quantitative metrics included the coefficient of variation and metrics based on the ventilation in each lung and each lung third (superior-inferior ventilation [Vent-SI] and anteroposterior ventilation). The functional profile of patients with esophageal cancer was characterized and compared (using the Mann-Whitney test) for cohorts based on thoracic comorbidities and radiologist-identified defects. RESULTS Radiologist observations revealed that 26% of patients with esophageal cancer had lobar-based defects and 46% had gravity-dependent atelectasis. The baseline values were 0.52 ± 0.20 (mean ± SD), 11.2 ± 12.5, and 72.5 ± 14.6 for the coefficient of variation, the ventilation ratio of right to left lung, and Vent-SI metrics, respectively. The Vent-SI values were significantly different between patients with and without thoracic comorbidities (P = .05), and the anteroposterior ventilation metric was able to delineate patients with and without gravity-dependent atelectasis (P < .01). CONCLUSIONS Our data demonstrate that approximately 30% of patients with esophageal cancer have significant ventilation heterogeneities. The current work uses radiologist observations and quantitative metrics to characterize 4DCT ventilation-based lung function for patients with esophageal cancer and presents data that can be used for future applications of 4DCT-ventilation to reduce thoracic toxicity for patients with esophageal cancer.
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53
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Mechanical Ventilation in Adults with Acute Respiratory Distress Syndrome. Summary of the Experimental Evidence for the Clinical Practice Guideline. Ann Am Thorac Soc 2018; 14:S261-S270. [PMID: 28985479 DOI: 10.1513/annalsats.201704-345ot] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
RATIONALE The American Thoracic Society/European Society for Intensive Care Medicine/Society of Critical Care Medicine guidelines on mechanical ventilation in adult patients with acute respiratory distress syndrome (ARDS) provide treatment recommendations derived from a thorough analysis of the clinical evidence on six clinical interventions. However, each of the recommendations contains areas of uncertainty and controversy, which may affect their appropriate clinical application. OBJECTIVES To provide a critical review of the experimental evidence surrounding the pathophysiology of ventilator-induced lung injury and to help clinicians apply the clinical recommendations to individual patients. METHODS We conducted a literature search and narrative review. RESULTS A large number of experimental studies have been performed with the aim of improving understanding of the pathophysiological effects of mechanical ventilation. These studies have formed the basis for the design of many clinical trials. Translational research has fundamentally advanced understanding of the mechanisms of ventilator-induced lung injury, thus informing the design of interventions that improve survival in patients with ARDS. CONCLUSIONS Because daily management of patients with ARDS presents the challenge of competing considerations, clinicians should consider the mechanism of ventilator-induced lung injury, as well as the rationale for interventions designed to mitigate it, when applying evidence-based recommendations at the bedside.
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54
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Foy BH, Gonem S, Brightling C, Siddiqui S, Kay D. Modelling the effect of gravity on inert-gas washout outputs. Physiol Rep 2018; 6:e13709. [PMID: 29845761 PMCID: PMC5974727 DOI: 10.14814/phy2.13709] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 04/11/2018] [Accepted: 04/15/2018] [Indexed: 11/24/2022] Open
Abstract
Multiple-breath washout (MBW) is a pulmonary function test (PFT) that is used to infer lung function through measurement of ventilation heterogeneity (VH). However, the body position that a test is taken in may also influence VH, due to the "Slinky" effect of gravity on the lungs. In healthy subjects this has minimal effect, but in unhealthy groups, PFT outputs have been seen to change drastically with body position. In this study, we used a combined computational and clinical approach to better understand the response of outputs from the MBW to body position. A patient-specific model of the MBW was developed, then validated against clinically measured washout data, as well as broader results in the literature. This model was then used to compare changes in MBW outputs with respect to body position, showing that output changes sensitively predict regional airway size differences between lobes. We then highlight cases in which body position effects may bias MBW outputs, leading to elevated or masked responses to bronchoconstriction. We close by placing this result in context with broader clinical practice, and showing how it can help improve interpretation of test outputs.
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Affiliation(s)
- Brody H. Foy
- Department of Computer ScienceUniversity of OxfordOxfordOxfordshireUnited Kingdom
| | - Sherif Gonem
- Respiratory Biomedical Research CentreUniversity of Leicester/National Institute of Health ResearchLeicesterLeicestershireUnited Kingdom
| | - Chris Brightling
- Respiratory Biomedical Research CentreUniversity of Leicester/National Institute of Health ResearchLeicesterLeicestershireUnited Kingdom
| | - Salman Siddiqui
- Respiratory Biomedical Research CentreUniversity of Leicester/National Institute of Health ResearchLeicesterLeicestershireUnited Kingdom
| | - David Kay
- Department of Computer ScienceUniversity of OxfordOxfordOxfordshireUnited Kingdom
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55
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Radermacher P, Maggiore SM, Mercat A. FiftyYears ofResearch inARDS.Gas Exchange in Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med 2017; 196:964-984. [DOI: 10.1164/rccm.201610-2156so] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Peter Radermacher
- Institute of Anaesthesiological Pathophysiology and Process Engineering, University Medical School, Ulm, Germany
| | - Salvatore Maurizio Maggiore
- Section of Anesthesia, Analgesia, Perioperative, and Intensive Care, Department of Medical, Oral, and Biotechnological Sciences, School of Medicine and Health Sciences, “SS. Annunziata” Hospital, “Gabriele d’Annunzio” University of Chieti-Pescara, Chieti, Italy; and
| | - Alain Mercat
- Department of Medical Intensive Care and Hyperbaric Medicine, Angers University Hospital, Angers, France
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56
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Michaelides SA, Michailidis AR, Bablekos GD, Analitis A, Michalatou M, Koulouris N. Does size matter concerning impact of position on oxygenation status in spontaneously breathing patients with unilateral effusion? Postgrad Med J 2017; 94:81-86. [PMID: 28972098 DOI: 10.1136/postgradmedj-2017-135164] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/31/2017] [Accepted: 09/09/2017] [Indexed: 11/03/2022]
Abstract
BACKGROUND Inconsistent and contradictory findings have appeared in the literature concerning the impact of body position on oxygenation in pleural effusion. METHODS We attempted to elucidate whether the size of the pleural effusion in patients with no parenchymal disease is the main determinant of posture-induced alterations in oxygenation parameters. We studied 62 spontaneously breathing patients aged 65.3±7.8 years (mean±SD), of whom 36 had large and massive-sized effusions (Group A) and 26 had small and moderate-sized effusions (Group B). Arterial blood gases were determined in four different body positions: sitting (SIT), supine (SUP), ipsilateral (IPS) and contralateral (CON) to the effusion side, after remaining relaxed for at least 20 min in each position. Separation into groups A and B was deliberately set from the position of the fluid meniscus line on a posteroanterior chest film just above the upper costal margin of the sixth anterior rib. A two-way ANOVA model with outcome variables PaO2, PaCO2 and [A-a] DO2 was used. RESULTS In both groups the best oxygenation was found in SIT. The worst oxygenation (highest [A-a] DO2 value) occurred in group A in CON compared with IPS (59.4±7.6 vs 49.0±7.5 mm Hg, p<0.001) and in group B in IPS compared with CON (51.0±8.7 vs 39.5±9.2 mm Hg, p<0.001). Also, PaCO2 showed significant differences in both groups in IPS compared with CON (p=0.002). CONCLUSIONS Patients with large-sized effusions exhibit the worst oxygenation when lying on the side contralateral to the effusion, while those with small-sized effusions exhibit the worst oxygenation when lying on the side ipsilateral to the effusion.
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Affiliation(s)
- Stylianos A Michaelides
- Department of Occupational Lung Diseases and Tuberculosis, Sismanogleio-Amalia Fleming General Hospital, Athens, Greece
| | - Avgerinos-Romanos Michailidis
- Department of Occupational Lung Diseases and Tuberculosis, Sismanogleio-Amalia Fleming General Hospital, Athens, Greece.,Department of Medical Laboratories, Faculty of Health and Caring Professions, University of Applied Sciences / Technological Educational Institute (TEI) of Athens, Athens, Greece
| | - George D Bablekos
- Department of Medical Laboratories, Faculty of Health and Caring Professions, University of Applied Sciences / Technological Educational Institute (TEI) of Athens, Athens, Greece
| | - Antonis Analitis
- Department of Hygiene, Epidemiology and Medical Statistics, Medical School National and Kapodistrian University of Athens, Athens, Greece
| | - Maria Michalatou
- Department of Physiotherapy, Sismanogleio-Amalia Fleming General Hospital, Athens, Greece
| | - Nikolaos Koulouris
- First Department of Thoracic Medicine, Medical School, National and Kapodistrian University of Athens, Hospital for Diseases of the Chest (Sotiria), Athens, Greece
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57
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Abstract
The management of the acute respiratory distress syndrome (ARDS) patient is fundamental to the field of intensive care medicine, and it presents unique challenges owing to the specialized mechanical ventilation techniques that such patients require. ARDS is a highly lethal disease, and there is compelling evidence that mechanical ventilation itself, if applied in an injurious fashion, can be a contributor to ARDS mortality. Therefore, it is imperative for any clinician central to the care of ARDS patients to understand the fundamental framework that underpins the approach to mechanical ventilation in this special scenario. The current review summarizes the major components of the mechanical ventilation strategy as it applies to ARDS.
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Affiliation(s)
- Oleg Epelbaum
- a Division of Pulmonary, Critical Care, and Sleep Medicine , Westchester Medical Center, New York Medical College , Valhalla , NY , USA
| | - Wilbert S Aronow
- b Division of Cardiology , Westchester Medical Center, New York Medical College , Valhalla , NY , USA
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58
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Hopkins SR, Elliott AR, Prisk GK, Darquenne C. Ventilation heterogeneity measured by multiple breath inert gas testing is not affected by inspired oxygen concentration in healthy humans. J Appl Physiol (1985) 2017; 122:1379-1387. [PMID: 28280107 DOI: 10.1152/japplphysiol.01013.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/03/2017] [Accepted: 03/08/2017] [Indexed: 11/22/2022] Open
Abstract
Multiple breath washout (MBW) and oxygen-enhanced MRI techniques use acute exposure to 100% oxygen to measure ventilation heterogeneity. Implicit is the assumption that breathing 100% oxygen does not induce changes in ventilation heterogeneity; however, this is untested. We hypothesized that ventilation heterogeneity decreases with increasing inspired oxygen concentration in healthy subjects. We performed MBW in 8 healthy subjects (4 women, 4 men; age = 43 ± 15 yr) with normal pulmonary function (FEV1 = 98 ± 6% predicted) using 10% argon as a tracer gas and oxygen concentrations of 12.5%, 21%, or 90%. MBW was performed in accordance with ERS-ATS guidelines. Subjects initially inspired air followed by a wash-in of test gas. Tests were performed in balanced order in triplicate. Gas concentrations were measured at the mouth, and argon signals rescaled to mimic a N2 washout, and analyzed to determine the distribution of specific ventilation (SV). Heterogeneity was characterized by the width of a log-Gaussian fit of the SV distribution and from Sacin and Scond indexes derived from the phase III slope. There were no significant differences in the ventilation heterogeneity due to altered inspired oxygen: histogram width (hypoxia 0.57 ± 0.11, normoxia 0.60 ± 0.08, hyperoxia 0.59 ± 0.09, P = 0.51), Scond (hypoxia 0.014 ± 0.011, normoxia 0.012 ± 0.015, hyperoxia 0.010 ± 0.011, P = 0.34), or Sacin (hypoxia 0.11 ± 0.04, normoxia 0.10 ± 0.03, hyperoxia 0.12 ± 0.03, P = 0.23). Functional residual capacity was increased in hypoxia (P = 0.04) and dead space increased in hyperoxia (P = 0.0001) compared with the other conditions. The acute use of 100% oxygen in MBW or MRI is unlikely to affect ventilation heterogeneity.NEW & NOTEWORTHY Hyperoxia is used to measure the distribution of ventilation in imaging and MBW but may alter the underlying ventilation distribution. We used MBW to evaluate the effect of inspired oxygen concentration on the ventilation distribution using 10% argon as a tracer. Short-duration exposure to hypoxia (12.5% oxygen) and hyperoxia (90% oxygen) during MBW had no significant effect on ventilation heterogeneity, suggesting that hyperoxia can be used to assess the ventilation distribution.
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Affiliation(s)
- Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; and .,Department of Radiology, University of California, San Diego, La Jolla, California
| | - Ann R Elliott
- Department of Medicine, University of California, San Diego, La Jolla, California; and
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California; and.,Department of Radiology, University of California, San Diego, La Jolla, California
| | - Chantal Darquenne
- Department of Medicine, University of California, San Diego, La Jolla, California; and
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59
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Sá RC, Henderson AC, Simonson T, Arai TJ, Wagner H, Theilmann RJ, Wagner PD, Prisk GK, Hopkins SR. Measurement of the distribution of ventilation-perfusion ratios in the human lung with proton MRI: comparison with the multiple inert-gas elimination technique. J Appl Physiol (1985) 2017; 123:136-146. [PMID: 28280105 DOI: 10.1152/japplphysiol.00804.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 02/23/2017] [Accepted: 03/07/2017] [Indexed: 11/22/2022] Open
Abstract
We have developed a novel functional proton magnetic resonance imaging (MRI) technique to measure regional ventilation-perfusion (V̇A/Q̇) ratio in the lung. We conducted a comparison study of this technique in healthy subjects (n = 7, age = 42 ± 16 yr, Forced expiratory volume in 1 s = 94% predicted), by comparing data measured using MRI to that obtained from the multiple inert gas elimination technique (MIGET). Regional ventilation measured in a sagittal lung slice using Specific Ventilation Imaging was combined with proton density measured using a fast gradient-echo sequence to calculate regional alveolar ventilation, registered with perfusion images acquired using arterial spin labeling, and divided on a voxel-by-voxel basis to obtain regional V̇A/Q̇ ratio. LogSDV̇ and LogSDQ̇, measures of heterogeneity derived from the standard deviation (log scale) of the ventilation and perfusion vs. V̇A/Q̇ ratio histograms respectively, were calculated. On a separate day, subjects underwent study with MIGET and LogSDV̇ and LogSDQ̇ were calculated from MIGET data using the 50-compartment model. MIGET LogSDV̇ and LogSDQ̇ were normal in all subjects. LogSDQ̇ was highly correlated between MRI and MIGET (R = 0.89, P = 0.007); the intercept was not significantly different from zero (-0.062, P = 0.65) and the slope did not significantly differ from identity (1.29, P = 0.34). MIGET and MRI measures of LogSDV̇ were well correlated (R = 0.83, P = 0.02); the intercept differed from zero (0.20, P = 0.04) and the slope deviated from the line of identity (0.52, P = 0.01). We conclude that in normal subjects, there is a reasonable agreement between MIGET measures of heterogeneity and those from proton MRI measured in a single slice of lung.NEW & NOTEWORTHY We report a comparison of a new proton MRI technique to measure regional V̇A/Q̇ ratio against the multiple inert gas elimination technique (MIGET). The study reports good relationships between measures of heterogeneity derived from MIGET and those derived from MRI. Although currently limited to a single slice acquisition, these data suggest that single sagittal slice measures of V̇A/Q̇ ratio provide an adequate means to assess heterogeneity in the normal lung.
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Affiliation(s)
- Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - A Cortney Henderson
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Tatum Simonson
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Harrieth Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Peter D Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California.,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; .,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
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60
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Yamamoto T, Kent MS, Wisner ER, Johnson LR, Stern JA, Qi L, Fujita Y, Boone JM. Single-energy computed tomography-based pulmonary perfusion imaging: Proof-of-principle in a canine model. Med Phys 2017; 43:3998. [PMID: 27370118 PMCID: PMC5438244 DOI: 10.1118/1.4953188] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Purpose: Radiotherapy (RT) that selectively avoids irradiating highly functional
lung
regions may reduce pulmonary toxicity, which is substantial in lung
cancer RT.
Single-energy computed
tomography
(CT)
pulmonary perfusion imaging has several advantages
(e.g., higher resolution) over other modalities and has great potential for
widespread clinical implementation, particularly in RT. The purpose of this study
was to establish proof-of-principle for single-energy CT perfusion
imaging. Methods: Single-energy CT perfusion imaging is based on the following:
(1) acquisition of end-inspiratory breath-hold CT scans before and
after intravenous injection of iodinated contrast agents, (2)
deformable image
registration (DIR) for spatial mapping of
those two CT
image
data sets,
and (3) subtraction of the precontrast image
data set
from the postcontrast image
data set,
yielding a map of regional Hounsfield unit (HU) enhancement, a surrogate for
regional perfusion. In a protocol approved by the institutional animal care and
use committee, the authors acquired CT scans in the prone position for a total of 14
anesthetized canines (seven canines with normal lungs and seven
canines with diseased lungs). The elastix algorithm was used for DIR. The accuracy
of DIR was evaluated based on the target registration error (TRE) of 50 anatomic
pulmonary landmarks per subject for 10 randomly selected subjects as well as on
singularities (i.e., regions where the displacement vector field is not
bijective). Prior to perfusion computation, HUs of the precontrast end-inspiratory
image were corrected for variation in the lung inflation level
between the precontrast and postcontrast end-inspiratory CT scans, using a
model built from two additional precontrast CT scans at
end-expiration and midinspiration. The authors also assessed spatial heterogeneity
and gravitationally directed gradients of regional perfusion for normal
lung
subjects and diseased lung subjects using a two-sample two-tailed
t-test. Results: The mean TRE (and standard deviation) was 0.6 ± 0.7 mm (smaller than the voxel
dimension) for DIR between pre contrast and postcontrast end-inspiratory
CT
image
data sets.
No singularities were observed in the displacement vector fields. The mean HU
enhancement (and standard deviation) was 37.3 ± 10.5 HU for normal lung subjects and 30.7
± 13.5 HU for diseased lung subjects. Spatial heterogeneity of regional perfusion was
found to be higher for diseased lung subjects than for normal lung subjects, i.e., a
mean coefficient of variation of 2.06 vs 1.59 (p = 0.07). The
average gravitationally directed gradient was strong and significant
(R2 = 0.99, p < 0.01) for
normal lung dogs, whereas it was moderate and nonsignificant
(R2 = 0.61, p = 0.12) for diseased
lung
dogs. Conclusions: This canine study demonstrated the accuracy of DIR with subvoxel TREs on average,
higher spatial heterogeneity of regional perfusion for diseased
lung
subjects than for normal lung subjects, and a strong gravitationally directed gradient
for normal lung subjects, providing proof-of-principle for single-energy
CT
pulmonary perfusion imaging. Further studies such as
comparison with other perfusion imaging modalities will be necessary
to validate the physiological significance.
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Affiliation(s)
- Tokihiro Yamamoto
- Department of Radiation Oncology, University of California Davis School of Medicine, Sacramento, California 95817
| | - Michael S Kent
- Department of Surgical and Radiological Sciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Erik R Wisner
- Department of Surgical and Radiological Sciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Lynelle R Johnson
- Department of Medicine and Epidemiology, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Joshua A Stern
- Department of Medicine and Epidemiology, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Lihong Qi
- Department of Public Health Sciences, University of California Davis, Davis, California 95616
| | - Yukio Fujita
- Department of Radiation Oncology, Tokai University, Isehara, Kanagawa 259-1193, Japan
| | - John M Boone
- Department of Radiology, University of California Davis School of Medicine, Sacramento, California 95817
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61
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Fain SB, Eldridge MW. Exploring new heights with pulmonary functional imaging: insights into high-altitude pulmonary edema. J Appl Physiol (1985) 2017; 122:853-854. [PMID: 28235856 DOI: 10.1152/japplphysiol.00168.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 02/21/2017] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sean B Fain
- University of Wisconsin-Madison Medical School, Wisconsin; and
| | - Marlowe W Eldridge
- Pediatric Critical Care Medicine Departments of Pediatrics, Kinesiology and Biomedical Engineering, University of Wisconsin-Madison, Wisconsin
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62
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Mase K, Noguchi T, Tagami M, Imura S, Tomita K, Monma M, Nozoe M, Takashima S, Kawakatsu K. Compression of the lungs by the heart in supine, side-lying, semi-prone positions. J Phys Ther Sci 2016; 28:2470-2473. [PMID: 27799672 PMCID: PMC5080154 DOI: 10.1589/jpts.28.2470] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/23/2016] [Indexed: 11/24/2022] Open
Abstract
[Purpose] Clarification of the differences in the compression volume of the lungs by the
heart (CVLH) between postures may facilitate the selection of optimal postures in
respiratory care. Determining CVLH in the supine, semi-prone (Sim’s position), and
side-lying positions was the aim of this study. [Subjects and Methods] Eight healthy
volunteers (six males, two females; mean age, 29.0 ± 9.2 years) were enrolled in the
study. Measurements were performed in the supine, right and left semi-prone, and right and
left side-lying positions. semi-prone position was inclined 45° ventrally from the
side-lying position. A 1.5-T system with a fast advanced spin-echo sequence in the coronal
plane was used for magnetic resonance imaging. [Results] CVLH and heart compression ratio
were significantly lower in the semi-prone position on both sides than the other
positions. The heart was displaced ventrally when semi-prone and a larger area of the
heart leaned on the ventral chest wall, localizing compression to part of the ventral
region of the dependent lung. [Conclusion] The region of lungs compressed by the heart is
reduced in the semi-prone position due to ventral displacement of the heart. These results
suggest that maintaining expansion of the dependent lung is easier in the semi-prone
position.
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Affiliation(s)
- Kyoushi Mase
- Department of Physical Therapy, Faculty of Nursing and Rehabilitation, Konan Women's University, Japan
| | - Tisa Noguchi
- Department of Rehabilitation, Konan Hospital, Japan
| | - Miki Tagami
- Department of Physical Therapy, Uekusa Gakuen University, Japan
| | - Shigeyuki Imura
- Department of Physical Therapy, Uekusa Gakuen University, Japan
| | - Kazuhide Tomita
- Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, Japan
| | - Masahiko Monma
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Japan
| | - Masafumi Nozoe
- Department of Physical Therapy, Faculty of Nursing and Rehabilitation, Konan Women's University, Japan
| | - Sachie Takashima
- Department of Physical Therapy, Faculty of Nursing and Rehabilitation, Konan Women's University, Japan
| | - Kunihiro Kawakatsu
- Department of Physical Therapy, Faculty of Nursing and Rehabilitation, Konan Women's University, Japan
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63
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Arai TJ, Theilmann RJ, Sá RC, Villongco MT, Hopkins SR. The effect of lung deformation on the spatial distribution of pulmonary blood flow. J Physiol 2016; 594:6333-6347. [PMID: 27273807 PMCID: PMC5088230 DOI: 10.1113/jp272030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/31/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes. The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution. Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. ABSTRACT Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P = 0.10). The greatest expansion was seen in the dependent region (P < 0.0001: dependent vs non-dependent, P < 0.0001: dependent vs middle) and RLL (P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = -0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = -0.058(0.126), +1 litre = -0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500 ml = -0.075(0.152), +1 litre = -0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] (P = 0.01). However, there was no significant lobar redistribution (P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung.
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Affiliation(s)
- Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Michael T Villongco
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA.
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.
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Abstract
As pulmonary functional imaging moves beyond the realm of the radiologist and physicist, it is important that imagers have a common language and understanding of the relevant physiology of the lung. This review will focus on key physiological concepts and pitfalls relevant to functional lung imaging.
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Johansson MJ, Kvitting JPE, Flatebø T, Nicolaysen A, Nicolaysen G, Walther SM. Inhibition of Constitutive Nitric Oxide Synthase Does Not Influence Ventilation-Perfusion Matching in Normal Prone Adult Sheep With Mechanical Ventilation. Anesth Analg 2016; 123:1492-1499. [PMID: 27622722 DOI: 10.1213/ane.0000000000001556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Local formation of nitric oxide in the lung induces vasodilation in proportion to ventilation and is a putative mechanism behind ventilation-perfusion matching. We hypothesized that regional ventilation-perfusion matching occurs in part due to local constitutive nitric oxide formation. METHODS Ventilation and perfusion were analyzed in lung regions (≈1.5 cm) before and after inhibition of constitutive nitric oxide synthase with N-nitro-L-arginine methyl ester (L-NAME) (25 mg/kg) in 7 prone sheep ventilated with 10 cm H2O positive end-expiratory pressure. Ventilation and perfusion were measured by the use of aerosolized fluorescent and infused radiolabeled microspheres, respectively. The animals were exsanguinated while deeply anesthetized; then, lungs were excised, dried at total lung capacity, and divided into cube units. The spatial location for each cube was tracked and fluorescence and radioactivity per unit weight determined. RESULTS After administration of L-NAME, pulmonary artery pressure increased from a mean of 16.6-23.6 mm Hg, P = .007 but PaO2, PaCO2, and SD log(V/Q) did not change. Distribution of ventilation was not influenced by L-NAME, but a small redistribution of perfusion from ventral to dorsal lung regions was observed. Perfusion to regions with the highest ventilation (fifth quintile of the ventilation distribution) remained unchanged after L-NAME. CONCLUSIONS We found minimal or no influence of constitutive nitric oxide synthase inhibition by L-NAME on the distributions of ventilation and perfusion, and ventilation-perfusion in prone, anesthetized, ventilated, and healthy adult sheep with normal gas exchange.
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Affiliation(s)
- Mats J Johansson
- From the *Department of Cardiothoracic Anesthesia and Intensive Care; †Division of Cardiovascular Medicine, Department of Medical and Health Sciences; ‡Department of Cardiothoracic Surgery, Linköping University Hospital, Linköping, Sweden; and §Department of Physiology, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway
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Scholten EL, Beitler JR, Prisk GK, Malhotra A. Treatment of ARDS With Prone Positioning. Chest 2016; 151:215-224. [PMID: 27400909 DOI: 10.1016/j.chest.2016.06.032] [Citation(s) in RCA: 221] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/11/2016] [Accepted: 06/29/2016] [Indexed: 12/15/2022] Open
Abstract
Prone positioning was first proposed in the 1970s as a method to improve gas exchange in ARDS. Subsequent observations of dramatic improvement in oxygenation with simple patient rotation motivated the next several decades of research. This work elucidated the physiological mechanisms underlying changes in gas exchange and respiratory mechanics with prone ventilation. However, translating physiological improvements into a clinical benefit has proved challenging; several contemporary trials showed no major clinical benefits with prone positioning. By optimizing patient selection and treatment protocols, the recent Proning Severe ARDS Patients (PROSEVA) trial demonstrated a significant mortality benefit with prone ventilation. This trial, and subsequent meta-analyses, support the role of prone positioning as an effective therapy to reduce mortality in severe ARDS, particularly when applied early with other lung-protective strategies. This review discusses the physiological principles, clinical evidence, and practical application of prone ventilation in ARDS.
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Affiliation(s)
- Eric L Scholten
- Division of Pulmonary and Critical Care Medicine, University of California, San Diego, La Jolla, CA.
| | - Jeremy R Beitler
- Division of Pulmonary and Critical Care Medicine, University of California, San Diego, La Jolla, CA
| | - G Kim Prisk
- Departments of Medicine and Radiology, University of California, San Diego, La Jolla, CA
| | - Atul Malhotra
- Division of Pulmonary and Critical Care Medicine, University of California, San Diego, La Jolla, CA
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Saure EW, Bakke PS, Lind Eagan TM, Aanerud M, Jensen RL, Grydeland TB, Johannessen A, Nilsen RM, Thorsen E, Hardie JA. Diffusion capacity and CT measures of emphysema and airway wall thickness - relation to arterial oxygen tension in COPD patients. Eur Clin Respir J 2016; 3:29141. [PMID: 27178139 PMCID: PMC4867045 DOI: 10.3402/ecrj.v3.29141] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 03/15/2016] [Accepted: 03/21/2016] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Decreased diffusing capacity of the lung for carbon monoxide (DLCO) is associated with emphysema. DLCO is also related to decreased arterial oxygen tension (PaO2), but there are limited data on associations between PaO2 and computed tomography (CT) derived measures of emphysema and airway wall thickness. OBJECTIVE To examine whether CT measures of emphysema and airway wall thickness are associated with level of arterial oxygen tension beyond that provided by measurements of diffusion capacity and spirometry. METHODS The study sample consisted of 271 smoking or ex-smoking COPD patients from the Bergen COPD Cohort Study examined in 2007-2008. Emphysema was assessed as percent of low-attenuation areas<-950 Hounsfield units (%LAA), and airway wall thickness as standardised measure at an internal perimeter of 10 mm (AWT-Pi10). Multiple linear regression models were fitted with PaO2 as the outcome variable, and %LAA, AWT-Pi10, DLCO and carbon monoxide transfer coefficient (KCO) as main explanatory variables. The models were adjusted for sex, age, smoking status, and haemoglobin concentration, as well as forced expiratory volume in one second (FEV1). RESULTS Sixty two per cent of the subjects were men, mean (SD) age was 64 (7) years, mean (SD) FEV1 in percent predicted was 50 (15)%, and mean PaO2 (SD) was 9.3 (1.1) kPa. The adjusted regression coefficient (CI) for PaO2 was -0.32 (-0.04-(-0.019)) per 10% increase in %LAA (p<0.01). When diffusion capacity and FEV1 were added to the model, respectively, the association lost its statistical significance. No relationship between airway wall thickness and PaO2 was found. CONCLUSION CT assessment of airway wall thickness is not associated with arterial oxygen tension in COPD patients. Emphysema score measured by chest CT, is related to decreased PaO2, but cannot replace measurements of diffusion capacity in the clinical evaluation of hypoxaemia.
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Affiliation(s)
- Eirunn Waatevik Saure
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway;
| | - Per Sigvald Bakke
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway
| | - Tomas Mikal Lind Eagan
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway.,Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway
| | - Marianne Aanerud
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
| | - Robert Leroy Jensen
- Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, Utah, USA
| | | | - Ane Johannessen
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway
| | - Roy Miodini Nilsen
- Centre for Clinical Research, Haukeland University Hospital, Bergen, Norway
| | - Einar Thorsen
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway
| | - Jon Andrew Hardie
- Department of Clinical Science, Pulmonary Division, University of Bergen, Bergen, Norway
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Pesenti A, Musch G, Lichtenstein D, Mojoli F, Amato MBP, Cinnella G, Gattinoni L, Quintel M. Imaging in acute respiratory distress syndrome. Intensive Care Med 2016; 42:686-698. [DOI: 10.1007/s00134-016-4328-1] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 03/11/2016] [Indexed: 11/30/2022]
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Abstract
The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed.
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Affiliation(s)
- Karthik Suresh
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Larissa A. Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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Hurtado DE, Villarroel N, Retamal J, Bugedo G, Bruhn A. Improving the Accuracy of Registration-Based Biomechanical Analysis: A Finite Element Approach to Lung Regional Strain Quantification. IEEE TRANSACTIONS ON MEDICAL IMAGING 2016; 35:580-588. [PMID: 26441413 DOI: 10.1109/tmi.2015.2483744] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Tissue deformation plays an important role in lung physiology, as lung parenchyma largely deforms during spontaneous ventilation. However, excessive regional deformation may lead to lung injury, as observed in patients undergoing mechanical ventilation. Thus, the accurate estimation of regional strain has recently received great attention in the intensive care community. In this work, we assess the accuracy of regional strain maps computed from direct differentiation of B-Spline (BS) interpolations, a popular technique employed in non-rigid registration of lung computed tomography (CT) images. We show that, while BS-based registration methods give excellent results for the deformation transformation, the strain field directly computed from BS derivatives results in predictions that largely oscillate, thus introducing important errors that can even revert the sign of strain. To alleviate such spurious behavior, we present a novel finite-element (FE) method for the regional strain analysis of lung CT images. The method follows from a variational strain recovery formulation, and delivers a continuous approximation to the strain field in arbitrary domains. From analytical benchmarks, we show that the FE method results in errors that are a fraction of those found for the BS method, both in an average and pointwise sense. The application of the proposed FE method to human lung CT images results in 3D strain maps are heterogeneous and smooth, showing high consistency with specific ventilation maps reported in the literature. We envision that the proposed FE method will considerably improve the accuracy of image-based biomechanical analysis, making it reliable enough for routine medical applications.
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72
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Kjørstad Å, Corteville DM, Henzler T, Schmid-Bindert G, Zöllner FG, Schad LR. Non-invasive quantitative pulmonary V/Q imaging using Fourier decomposition MRI at 1.5T. Z Med Phys 2015; 25:326-332. [DOI: 10.1016/j.zemedi.2015.02.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 02/18/2015] [Accepted: 02/19/2015] [Indexed: 10/23/2022]
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Thompson BR, Ellis MJ, Stuart-Andrews C, Lopez M, Kedarisetty S, Snell GI, Prisk GK. Early bronchiolitis obliterans syndrome shows an abnormality of perfusion not ventilation in lung transplant recipients. Respir Physiol Neurobiol 2015; 216:28-34. [DOI: 10.1016/j.resp.2015.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 05/04/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
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Miller GW, Mugler JP, Sá RC, Altes TA, Prisk GK, Hopkins SR. Advances in functional and structural imaging of the human lung using proton MRI. NMR IN BIOMEDICINE 2014; 27:1542-56. [PMID: 24990096 PMCID: PMC4515033 DOI: 10.1002/nbm.3156] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/30/2014] [Accepted: 06/01/2014] [Indexed: 05/05/2023]
Abstract
The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and oxygen-enhanced imaging techniques to quantify regional perfusion and ventilation, respectively, in standard units of measurement. By combining these techniques into a single scan, it is also possible to quantify the local ventilation-perfusion ratio, which is the most important determinant of gas-exchange efficiency in the lung. To demonstrate potential for accurate and meaningful measurements of lung function, this technique was used to study gravitational gradients of ventilation, perfusion, and ventilation-perfusion ratio in healthy subjects, yielding quantitative results consistent with expected regional variations. Such techniques can also be applied in the time domain, providing new tools for studying temporal dynamics of lung function. Temporal ASL measurements showed increased spatial-temporal heterogeneity of pulmonary blood flow in healthy subjects exposed to hypoxia, suggesting sensitivity to active control mechanisms such as hypoxic pulmonary vasoconstriction, and illustrating that to fully examine the factors that govern lung function it is necessary to consider temporal as well as spatial variability. Further development to increase spatial coverage and improve robustness would enhance the clinical applicability of these new functional imaging tools. In the realm of structural imaging, pulse sequence techniques such as ultrashort echo-time radial k-space acquisition, ultrafast steady-state free precession, and imaging-based diaphragm triggering can be combined to overcome the significant challenges associated with proton MRI in the lung, enabling high-quality three-dimensional imaging of the whole lung in a clinically reasonable scan time. Images of healthy and cystic fibrosis subjects using these techniques demonstrate substantial promise for non-contrast pulmonary angiography and detailed depiction of airway disease. Although there is opportunity for further optimization, such approaches to structural lung imaging are ready for clinical testing.
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Affiliation(s)
- G. Wilson Miller
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
- Address correspondence to: Wilson Miller, Radiology Research, 480 Ray C. Hunt Dr., Box 801339, Charlottesville, VA 22908, Phone: 434-243-9216, Fax: 434-924-9435,
| | - John P. Mugler
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
| | - Rui C. Sá
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
| | - Talissa A. Altes
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
| | - G. Kim Prisk
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
| | - Susan R. Hopkins
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
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Couch MJ, Ball IK, Li T, Fox MS, Ouriadov AV, Biman B, Albert MS. Inert fluorinated gas MRI: a new pulmonary imaging modality. NMR IN BIOMEDICINE 2014; 27:1525-1534. [PMID: 25066661 DOI: 10.1002/nbm.3165] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 06/06/2014] [Accepted: 06/12/2014] [Indexed: 06/03/2023]
Abstract
Fluorine-19 ((19)F) MRI of the lungs using inhaled inert fluorinated gases can potentially provide high quality images of the lungs that are similar in quality to those from hyperpolarized (HP) noble gas MRI. Inert fluorinated gases have the advantages of being nontoxic, abundant, and inexpensive compared with HP gases. Due to the high gyromagnetic ratio of (19)F, there is sufficient thermally polarized signal for imaging, and averaging within a single breath-hold is possible due to short longitudinal relaxation times. Therefore, the gases do not need to be hyperpolarized prior to their use in MRI. This eliminates the need for an expensive polarizer and expensive isotopes. Inert fluorinated gas MRI of the lungs has been previously demonstrated in animals, and more recently in healthy volunteers and patients with lung diseases. The ongoing improvements in image quality demonstrate the potential of (19)F MRI for visualizing the distribution of ventilation in human lungs and detecting functional biomarkers. In this brief review, the development of inert fluorinated gas MRI, current progress, and future prospects are discussed. The current state of HP noble gas MRI is also briefly discussed in order to provide context to the development of this new imaging modality. Overall, this may be a viable clinical imaging modality that can provide useful information for the diagnosis and management of chronic respiratory diseases.
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Affiliation(s)
- Marcus J Couch
- Lakehead University, Thunder Bay, Ontario, Canada; Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada
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Asadi AK, Sá RC, Kim NH, Theilmann RJ, Hopkins SR, Buxton RB, Prisk GK. Inhaled nitric oxide alters the distribution of blood flow in the healthy human lung, suggesting active hypoxic pulmonary vasoconstriction in normoxia. J Appl Physiol (1985) 2014; 118:331-43. [PMID: 25429099 DOI: 10.1152/japplphysiol.01354.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxic pulmonary vasoconstriction (HPV) is thought to actively regulate ventilation-perfusion (V̇a/Q̇) matching, reducing perfusion in regions of alveolar hypoxia. We assessed the extent of HPV in the healthy human lung using inhaled nitric oxide (iNO) under inspired oxygen fractions (FiO2 ) of 0.125, 0.21, and 0.30 (a hyperoxic stimulus designed to abolish HPV without the development of atelectasis). Dynamic measures of blood flow were made in a single sagittal slice of the right lung of five healthy male subjects using an arterial spin labeling (ASL) MRI sequence, following a block stimulus pattern (3 × 60 breaths) with 40 ppm iNO administered in the central block. The overall spatial heterogeneity, spatiotemporal variability, and regional pattern of pulmonary blood flow was quantified as a function of condition (FiO2 × iNO state). While spatial heterogeneity did not change significantly with iNO administration or FiO2 , there were statistically significant increases in Global Fluctuation Dispersion, (a marker of spatiotemporal flow variability) when iNO was administered during hypoxia (5.4 percentage point increase, P = 0.003). iNO had an effect on regional blood flow that was FiO2 dependent (P = 0.02), with regional changes in the pattern of blood flow occurring in hypoxia (P = 0.007) and normoxia (P = 0.008) tending to increase flow to dependent lung at the expense of nondependent lung. These findings indicate that inhaled nitric oxide significantly alters the distribution of blood flow in both hypoxic and normoxic healthy subjects, and suggests that some baseline HPV may indeed be present in the normoxic lung.
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Affiliation(s)
- Amran K Asadi
- Department of Medicine, University of California, San Diego, La Jolla, California; and
| | - Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, California; and
| | - Nick H Kim
- Department of Medicine, University of California, San Diego, La Jolla, California; and
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, California
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; and Department of Radiology, University of California, San Diego, La Jolla, California
| | - Richard B Buxton
- Department of Radiology, University of California, San Diego, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California; and Department of Radiology, University of California, San Diego, La Jolla, California
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Yamamoto T, Kabus S, Lorenz C, Mittra E, Hong JC, Chung M, Eclov N, To J, Diehn M, Loo BW, Keall PJ. Pulmonary ventilation imaging based on 4-dimensional computed tomography: comparison with pulmonary function tests and SPECT ventilation images. Int J Radiat Oncol Biol Phys 2014; 90:414-22. [PMID: 25104070 DOI: 10.1016/j.ijrobp.2014.06.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 05/28/2014] [Accepted: 06/01/2014] [Indexed: 12/25/2022]
Abstract
PURPOSE 4-dimensional computed tomography (4D-CT)-based pulmonary ventilation imaging is an emerging functional imaging modality. The purpose of this study was to investigate the physiological significance of 4D-CT ventilation imaging by comparison with pulmonary function test (PFT) measurements and single-photon emission CT (SPECT) ventilation images, which are the clinical references for global and regional lung function, respectively. METHODS AND MATERIALS In an institutional review board-approved prospective clinical trial, 4D-CT imaging and PFT and/or SPECT ventilation imaging were performed in thoracic cancer patients. Regional ventilation (V4DCT) was calculated by deformable image registration of 4D-CT images and quantitative analysis for regional volume change. V4DCT defect parameters were compared with the PFT measurements (forced expiratory volume in 1 second (FEV1; % predicted) and FEV1/forced vital capacity (FVC; %). V4DCT was also compared with SPECT ventilation (VSPECT) to (1) test whether V4DCT in VSPECT defect regions is significantly lower than in nondefect regions by using the 2-tailed t test; (2) to quantify the spatial overlap between V4DCT and VSPECT defect regions with Dice similarity coefficient (DSC); and (3) to test ventral-to-dorsal gradients by using the 2-tailed t test. RESULTS Of 21 patients enrolled in the study, 18 patients for whom 4D-CT and either PFT or SPECT were acquired were included in the analysis. V4DCT defect parameters were found to have significant, moderate correlations with PFT measurements. For example, V4DCT(HU) defect volume increased significantly with decreasing FEV1/FVC (R=-0.65, P<.01). V4DCT in VSPECT defect regions was significantly lower than in nondefect regions (mean V4DCT(HU) 0.049 vs 0.076, P<.01). The average DSCs for the spatial overlap with SPECT ventilation defect regions were only moderate (V4DCT(HU)0.39 ± 0.11). Furthermore, ventral-to-dorsal gradients of V4DCT were strong (V4DCT(HU) R(2) = 0.69, P=.08), which was similar to VSPECT (R(2) = 0.96, P<.01). CONCLUSIONS An 18-patient study demonstrated significant correlations between 4D-CT ventilation and PFT measurements as well as SPECT ventilation, providing evidence toward the validation of 4D-CT ventilation imaging.
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Affiliation(s)
- Tokihiro Yamamoto
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California; Department of Radiation Oncology, University of California Davis School of Medicine, Sacramento, California.
| | - Sven Kabus
- Department of Digital Imaging, Philips Research Europe, Hamburg, Germany
| | - Cristian Lorenz
- Department of Digital Imaging, Philips Research Europe, Hamburg, Germany
| | - Erik Mittra
- Departments of Radiology, Stanford University School of Medicine, Stanford, California
| | - Julian C Hong
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Melody Chung
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Neville Eclov
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Jacqueline To
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Maximilian Diehn
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Billy W Loo
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California
| | - Paul J Keall
- Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
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Hu SL, He HL, Pan C, Liu AR, Liu SQ, Liu L, Huang YZ, Guo FM, Yang Y, Qiu HB. The effect of prone positioning on mortality in patients with acute respiratory distress syndrome: a meta-analysis of randomized controlled trials. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2014; 18:R109. [PMID: 24887034 PMCID: PMC4075407 DOI: 10.1186/cc13896] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 05/13/2014] [Indexed: 12/31/2022]
Abstract
Introduction Prone positioning (PP) has been reported to improve the survival of patients with severe acute respiratory distress syndrome (ARDS). However, it is uncertain whether the beneficial effects of PP are associated with positive end-expiratory pressure (PEEP) levels and long durations of PP. In this meta-analysis, we aimed to evaluate whether the effects of PP on mortality could be affected by PEEP level and PP duration and to identify which patients might benefit the most from PP. Methods Publications describing randomized controlled trials (RCTs) in which investigators have compared prone and supine ventilation were retrieved by searching the following electronic databases: PubMed/MEDLINE, the Cochrane Library, the Web of Science and Elsevier Science (inception to May 2013). Two investigators independently selected RCTs and assessed their quality. The data extracted from the RCTs were combined in a cumulative meta-analysis and analyzed using methods recommended by the Cochrane Collaboration. Results A total of nine RCTs with an aggregate of 2,242 patients were included. All of the studies received scores of up to three points using the methods recommended by Jadad et al. One trial did not conceal allocation. This meta-analysis revealed that, compared with supine positioning, PP decreased the 28- to 30-day mortality of ARDS patients with a ratio of partial pressure of arterial oxygen/fraction of inspired oxygen ≤100 mmHg (n = 508, risk ratio (RR) = 0.71, 95 confidence interval (CI) = 0.57 to 0.89; P = 0.003). PP was shown to reduce both 60-day mortality (n = 518, RR = 0.82, 95% CI = 0.68 to 0.99; P = 0.04) and 90-day mortality (n = 516, RR = 0.57, 95% CI = 0.43 to 0.75; P < 0.0001) in ARDS patients ventilated with PEEP ≥10 cmH2O. Moreover, PP reduced 28- to 30-day mortality when the PP duration was >12 h/day (n = 1,067, RR = 0.73, 95% CI = 0.54 to 0.99; P = 0.04). Conclusions PP reduced mortality among patients with severe ARDS and patients receiving relatively high PEEP levels. Moreover, long-term PP improved the survival of ARDS patients.
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Sá RC, Asadi AK, Theilmann RJ, Hopkins SR, Prisk GK, Darquenne C. Validating the distribution of specific ventilation in healthy humans measured using proton MR imaging. J Appl Physiol (1985) 2014; 116:1048-56. [PMID: 24505099 DOI: 10.1152/japplphysiol.00982.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Specific ventilation imaging (SVI) uses proton MRI to quantitatively map the distribution of specific ventilation (SV) in the human lung, using inhaled oxygen as a contrast agent. To validate this recent technique, we compared the quantitative measures of heterogeneity of the SV distribution in a 15-mm sagittal slice of lung obtained in 10 healthy supine subjects, (age 37 ± 10 yr, forced expiratory volume in 1 s 97 ± 7% predicted) using SVI to those obtained in the whole lung from multiple-breath nitrogen washout (MBW). Using the analysis of Lewis et al. (Lewis SM, Evans JW, Jalowayski AA. J App Physiol 44: 416-423, 1978), the most likely distribution of SV from the MBW data was computed and compared with the distribution of SV obtained from SVI, after normalizing for the difference in tidal volume. The average SV was 0.30 ± 0.10 MBW, compared with 0.36 ± 0.10 SVI (P = 0.01). The width of the distribution, a measure of the heterogeneity, obtained using both methods was comparable: 0.51 ± 0.06 and 0.47 ± 0.08 in MBW and SVI, respectively (P = 0.15). The MBW estimated width of the SV distribution was 0.05 (10.7%) higher than that estimated using SVI, and smaller than the intertest variability of the MBW estimation [inter-MBW (SD) for the width of the SV distribution was 0.08 (15.8)%]. To assess reliability, SVI was performed twice on 13 subjects showing small differences between measurements of SV heterogeneity (typical error 0.05, 12%). In conclusion, quantitative estimations of SV heterogeneity from SVI are reliable and similar to those obtained using MBW, with SVI providing spatial information that is absent in MBW.
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Affiliation(s)
- Rui Carlos Sá
- Pulmonary Imaging Laboratory, Department of Medicine, University of California, San Diego, La Jolla, California
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Gattinoni L, Taccone P, Carlesso E, Marini JJ. Prone position in acute respiratory distress syndrome. Rationale, indications, and limits. Am J Respir Crit Care Med 2014; 188:1286-93. [PMID: 24134414 DOI: 10.1164/rccm.201308-1532ci] [Citation(s) in RCA: 268] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the prone position, computed tomography scan densities redistribute from dorsal to ventral as the dorsal region tends to reexpand while the ventral zone tends to collapse. Although gravitational influence is similar in both positions, dorsal recruitment usually prevails over ventral derecruitment, because of the need for the lung and its confining chest wall to conform to the same volume. The final result of proning is that the overall lung inflation is more homogeneous from dorsal to ventral than in the supine position, with more homogeneously distributed stress and strain. As the distribution of perfusion remains nearly constant in both postures, proning usually improves oxygenation. Animal experiments clearly show that prone positioning delays or prevents ventilation-induced lung injury, likely due in large part to more homogeneously distributed stress and strain. Over the last 15 years, five major trials have been conducted to compare the prone and supine positions in acute respiratory distress syndrome, regarding survival advantage. The sequence of trials enrolled patients who were progressively more hypoxemic; exposure to the prone position was extended from 8 to 17 hours/day, and lung-protective ventilation was more rigorously applied. Single-patient and meta-analyses drawing from the four major trials showed significant survival benefit in patients with PaO2/FiO2 lower than 100. The latest PROSEVA (Proning Severe ARDS Patients) trial confirmed these benefits in a formal randomized study. The bulk of data indicates that in severe acute respiratory distress syndrome, carefully performed prone positioning offers an absolute survival advantage of 10-17%, making this intervention highly recommended in this specific population subset.
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Affiliation(s)
- Luciano Gattinoni
- 1 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy
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