Quantification of lung recruitment by respiratory mechanics and CT imaging: what are the clinical implications?
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ABSTRACT:
SUBMITTER: McKown AC
PROVIDER: S-EPMC4842401 | biostudies-literature | 2016 Apr
REPOSITORIES: biostudies-literature
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Quantification of lung recruitment by respiratory mechanics and CT imaging: what are the clinical implications?
McKown Andrew C AC Ware Lorraine B LB
Annals of translational medicine 20160401 7
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Project description:BackgroundTo develop and validate classifier models that could be used to identify patients with a high percentage of potentially recruitable lung from readily available clinical data and from single CT scan quantitative analysis at intensive care unit admission. 221 retrospectively enrolled mechanically ventilated, sedated and paralyzed patients with acute respiratory distress syndrome (ARDS) underwent a PEEP trial at 5 and 15 cmH2O of PEEP and two lung CT scans performed at 5 and 45 cmH2O of airway pressure. Lung recruitability was defined at first as percent change in not aerated tissue between 5 and 45 cmH2O (radiologically defined; recruiters: Δ45-5non-aerated tissue > 15%) and secondly as change in PaO2 between 5 and 15 cmH2O (gas exchange-defined; recruiters: Δ15-5PaO2 > 24 mmHg). Four machine learning (ML) algorithms were evaluated as classifiers of radiologically defined and gas exchange-defined lung recruiters using different models including different variables, separately or combined, of lung mechanics, gas exchange and CT data.ResultsML algorithms based on CT scan data at 5 cmH2O classified radiologically defined lung recruiters with similar AUC as ML based on the combination of lung mechanics, gas exchange and CT data. ML algorithm based on CT scan data classified gas exchange-defined lung recruiters with the highest AUC.ConclusionsML based on a single CT data at 5 cmH2O represented an easy-to-apply tool to classify ARDS patients in recruiters and non-recruiters according to both radiologically defined and gas exchange-defined lung recruitment within the first 48 h from the start of mechanical ventilation.
| S-EPMC10322807 | biostudies-literature
Project description:Background: The pathophysiological effects of positive end-expiratory pressure (PEEP) on respiratory mechanics, lung recruitment, and intracranial pressure (ICP) in acute brain-injured patients have not been completely elucidated. The primary aim of this study was to assess the effects of PEEP augmentation on respiratory mechanics, quantitative computed lung tomography (qCT) findings, and its relationship with ICP modifications. Secondary aims included the assessment of the correlations between different factors (respiratory mechanics and qCT features) with the changes of ICP and how these factors at baseline may predict ICP response after greater PEEP levels. Methods: A prospective, observational study included mechanically ventilated patients with acute brain injury requiring invasive ICP and who underwent two-PEEP levels lung CT scan. Respiratory system compliance (Crs), arterial partial pressure of carbon dioxide (PaCO2), mean arterial pressure (MAP), data from qCT and ICP were obtained at PEEP 5 and 15 cmH2O. Results: Sixteen examinations (double PEEP lung CT and neuromonitoring) in 15 patients were analyzed. The median age of the patients was 54 years (interquartile range, IQR = 39-65) and 53% were men. The median Glasgow Coma Scale (GCS) at intensive care unit (ICU) admission was 8 (IQR = 3-12). Median alveolar recruitment was 2.5% of total lung weight (-1.5 to 4.7). PEEP from 5 to 15 cmH2O increased ICP [median values from 14.0 (11.2-17.5) to 23.5 (19.5-26.8) mmHg, p < 0.001, respectively]. The amount of recruited lung tissue on CT was inversely correlated with the change (Δ) in ICP (rho = -0.78; p = 0.0006). Additionally, ΔCrs (rho = -0.77, p = 0.008), ΔPaCO2 (rho = 0.81, p = 0.0003), and ΔMAP (rho = -0.64, p = 0.009) were correlated with ΔICP. Baseline Crs was not predictive of ICP response to PEEP. Conclusions: The main factors associated with increased ICP after PEEP augmentation included reduced Crs, lower MAP and lung recruitment, and increased PaCO2, but none of these factors was able to predict, at baseline, ICP response to PEEP. To assess the potential benefits of increased PEEP in patients with acute brain injury, hemodynamic status, respiratory mechanics, and lung morphology should be taken into account.
| S-EPMC8558243 | biostudies-literature
Project description:PurposeTo quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions.Materials and methodsEqual mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds.ResultsEach element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults-that is, 100 kVp and higher-barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter.ConclusionThe consistently high image contrast produced with 100-140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent.
| S-EPMC4770942 | biostudies-literature
Project description:BackgroundIn sedated and paralyzed children with acute respiratory failure, the compliance of respiratory system and functional residual capacity were significantly reduced compared with healthy subjects. However, no major studies in children with ARDS have investigated the role of different levels of PEEP and tidal volume on the partitioned respiratory mechanic (lung and chest wall), stress (transpulmonary pressure) and strain (inflated volume above the functional residual capacity).MethodsThe end-expiratory lung volume was measured using a simplified closed circuit helium dilution method. During an inspiratory and expiratory pause, the airway and esophageal pressure were measured. Transpulmonary pressure was computed as the difference between airway and esophageal pressure.ResultsTen intubated sedated paralyzed healthy children and ten children with ARDS underwent a PEEP trial (4 and 12 cmH2O) with a tidal volume of 8, 10 and 12 ml/kgIBW. The two groups were comparable for age and BMI (2.5 [1.0-5.5] vs 3.0 [1.7-7.2] years and 15.1 ± 2.4 vs 15.3 ± 3.0 kg/m(2)). The functional residual capacity in ARDS patients was significantly lower as compared to the control group (10.4 [9.1-14.3] vs 16.6 [11.7-24.6] ml/kg, p = 0.04). The ARDS patients had a significantly lower respiratory system and lung compliance as compared to control subjects (9.9 ± 5.0 vs 17.8 ± 6.5, 9.3 ± 4.9 vs 16.9 ± 4.1 at 4 cmH2O of PEEP and 11.7 ± 5.8 vs 23.7 ± 6.8, 10.0 ± 4.9 vs 23.4 ± 7.5 at 12 cmH2O of PEEP). The compliance of the chest wall was similar in both groups (76.7 ± 30.2 vs 94.4 ± 76.4 and 92.6 ± 65.3 vs 90.0 ± 61.7 at 4 and 12 cmH2O of PEEP). The lung stress and strain were significantly higher in ARDS patients as compared to control subjects and were poorly related to airway pressure and tidal volume normalized for body weight.ConclusionsAirway pressures and tidal volume normalized to body weight are poor surrogates for lung stress and strain in mild pediatric ARDS.Trial registrationClinialtrials.gov NCT02036801. Registered 13 January 2014.
| S-EPMC4742456 | biostudies-literature
Project description:Ozone (O3) is a highly potent and reactive air pollutant. It has been linked to acute and chronic respiratory diseases in humans by inducing inflammation. Our studies have found evidence that 0.05 ppm of O3, within the threshold of air quality standards, is capable of inducing acute lung injury. This study was undertaken to examine O3-induced lung damage using [18F]F-FDG (2-deoxy-2-[18F]fluoro-D-glucose) microPET/CT in wild-type mice. [18F]F-FDG is a known PET tracer for inflammation. Sequential [18F]F-FDG microPET/CT was performed at baseline (i.e. before O3 exposure), immediately (0 h), at 24 h and at 28 h following 2 h of 0.05 ppm O3 exposure. The images were quantified to determine O3 induced spatial standard uptake ratio of [18F]F-FDG in relation to lung tissue density and compared with baseline values. Immediately after O3 exposure, we detected a 72.21 ± 0.79% increase in lung [18F]F-FDG uptake ratio when compared to baseline measures. At 24 h post-O3 exposure, the [18F]F-FDG uptake becomes highly variable (S.D. in [18F]F-FDG = 5.174 × 10-4 units) with a 42.54 ± 0.33% increase in lung [18F]F-FDG compared to baseline. At 28 h time-point, [18F]F-FDG uptake ratio was similar to baseline values. However, the pattern of [18F]F-FDG distribution varied and was interspersed with zones of minimal uptake. Our microPET/CT imaging protocol can quantify and identify atypical regional lung uptake of [18F]F-FDG to understand the lung response to O3 exposure.
| S-EPMC7515916 | biostudies-literature
Project description:IntroductionMechanical ventilation (MV) of mice is increasingly required in experimental studies, but the conditions that allow stable ventilation of mice over several hours have not yet been fully defined. In addition, most previous studies documented vital parameters and lung mechanics only incompletely. The aim of the present study was to establish experimental conditions that keep these parameters within their physiological range over a period of 6 h. For this purpose, we also examined the effects of frequent short recruitment manoeuvres (RM) in healthy mice.MethodsMice were ventilated at low tidal volume V(T) = 8 mL/kg or high tidal volume V(T) = 16 mL/kg and a positive end-expiratory pressure (PEEP) of 2 or 6 cm H(2)O. RM were performed every 5 min, 60 min or not at all. Lung mechanics were followed by the forced oscillation technique. Blood pressure (BP), electrocardiogram (ECG), heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, neutrophil-recruitment, microvascular permeability and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) and blood serum as well as histopathology of the lung were examined.ResultsMV with repetitive RM every 5 min resulted in stable respiratory mechanics. Ventilation without RM worsened lung mechanics due to alveolar collapse, leading to impaired gas exchange. HF and BP were affected by anaesthesia, but not by ventilation. Microvascular permeability was highest in atelectatic lungs, whereas neutrophil-recruitment and structural changes were strongest in lungs ventilated with high tidal volume. The cytokines IL-6 and KC, but neither TNF nor IP-10, were elevated in the BAL and serum of all ventilated mice and were reduced by recurrent RM. Lung mechanics, oxygenation and pulmonary inflammation were improved by increased PEEP.ConclusionsRecurrent RM maintain lung mechanics in their physiological range during low tidal volume ventilation of healthy mice by preventing atelectasis and reduce the development of pulmonary inflammation.
| S-EPMC3174196 | biostudies-literature
Project description:Background and Purpose: Intracranial arterial calcification (IAC) has been the focus of much attention by clinicians and researchers as an indicator of intracranial atherosclerosis, but correlations of IAC patterns (intimal or medial) with the presence of atherosclerotic plaques and plaque stability are still a matter of debate. Our study aimed to assess the associations of IAC patterns identified on computed tomography (CT) with the presence of plaque detected on vessel wall magnetic resonance imaging and plaque stability. Materials and Methods: Patients with stroke or transient ischemic attack and intracranial artery stenosis were recruited. IAC was detected and localized (intima or media) on non-contrast CT images. Intracranial atherosclerotic plaques were identified using vessel wall magnetic resonance imaging and matched to corresponding CT images. Associations between IAC patterns and culprit atherosclerotic plaques were assessed by using multivariate regression. Results: Seventy-five patients (mean age, 63.4 ± 11.6 years; males, 46) were included. Two hundred and twenty-one segments with IAC were identified on CT in 66 patients, including 86 (38.9%) predominantly intimal calcifications and 135 (61.1%) predominantly medial calcifications. A total of 72.0% of intimal calcifications coexisted with atherosclerotic plaques, whereas only 10.2% of medial calcifications coexisted with plaques. Intimal calcification was more commonly shown in non-culprit plaques than culprit plaques (25.9 vs. 9.4%, P = 0.008). The multivariate mixed logistic regression adjusted for the degree of stenosis showed that intimal calcification was significantly associated with non-culprit plaques (OR, 2.971; 95% CI, 1.036-8.517; P = 0.043). Conclusion: Our findings suggest that intimal calcification may indicate the existence of a stable form of atherosclerotic plaque, but plaques can exist in the absence of intimal calcification especially in the middle cerebral artery.
| S-EPMC8319500 | biostudies-literature
Project description:ObjectiveThe purpose of this study was to describe the effect of implementing an imaging quality assurance program on CT image quality in the Lung Screening Study component of the National Lung Screening Trial.Materials and methodsThe National Lung Screening Trial is a multicenter study in which 53,457 subjects at increased risk of lung cancer were randomized to undergo three annual chest CT or radiographic screenings for lung cancer to determine the relative effect of use of the two screening tests on lung cancer mortality. Of the 26,724 subjects randomized to the CT screening arm of the National Lung Screening Trial, the Lung Screening Study randomized 17,309 through 10 screening centers. The others were randomized through the American College of Radiology Imaging Network. Quality assurance procedures were implemented that included centralized review of a random sample of 1,504 Lung Screening Study CT examinations. Quality defect rates were tabulated.ResultsQuality defect rates ranged from 0% (section reconstruction interval) to 7.1% (reconstructed field of view), and most errors were sporadic. However, a recurrently high effective tube current-time product setting at one center, excessive streak artifact at one center, and excessive section thickness at one center were detected and corrected through the quality assurance process. Field-of-view and scan length errors were less frequent over the second half of the screening period (p < 0.01 for both parameters, two-tailed, paired Student's t test). Error rates varied among the screening centers and reviewers for most parameters evaluated.ConclusionOur experience suggested that centralized monitoring of image quality is helpful for reducing quality defects in multicenter trials.
| S-EPMC2841058 | biostudies-literature
Project description:Respiratory motion artifacts and partial volume effects (PVEs) are two degrading factors that affect the accuracy of image quantification in PET/CT imaging. In this article, the authors propose a joint motion and PVE correction approach (JMPC) to improve PET quantification by simultaneously correcting for respiratory motion artifacts and PVE in patients with lung/thoracic cancer. The objective of this article is to describe this approach and evaluate its performance using phantom and patient studies.The proposed joint correction approach incorporates a model of motion blurring, PVE, and object size/shape. A motion blurring kernel (MBK) is then estimated from the deconvolution of the joint model, while the activity concentration (AC) of the tumor is estimated from the normalization of the derived MBK. To evaluate the performance of this approach, two phantom studies and eight patient studies were performed. In the phantom studies, two motion waveforms-a linear sinusoidal and a circular motion-were used to control the motion of a sphere, while in the patient studies, all participants were instructed to breathe regularly. For the phantom studies, the resultant MBK was compared to the true MBK by measuring a correlation coefficient between the two kernels. The measured sphere AC derived from the proposed method was compared to the true AC as well as the ACs in images exhibiting PVE only and images exhibiting both PVE and motion blurring. For the patient studies, the resultant MBK was compared to the motion extent derived from a 4D-CT study, while the measured tumor AC was compared to the AC in images exhibiting both PVE and motion blurring.For the phantom studies, the estimated MBK approximated the true MBK with an average correlation coefficient of 0.91. The tumor ACs following the joint correction technique were similar to the true AC with an average difference of 2%. Furthermore, the tumor ACs on the PVE only images and images with both motion blur and PVE effects were, on average, 75% and 47.5% (10%) of the true AC, respectively, for the linear (circular) motion phantom study. For the patient studies, the maximum and mean AC/SUV on the PET images following the joint correction are, on average, increased by 125.9% and 371.6%, respectively, when compared to the PET images with both PVE and motion. The motion extents measured from the derived MBK and 4D-CT exhibited an average difference of 1.9 mm.The proposed joint correction approach can improve the accuracy of PET quantification by simultaneously compensating for the respiratory motion artifacts and PVE in lung/thoracic PET/CT imaging.
| S-EPMC3820620 | biostudies-other
Project description:ObjectivesBoth oxygenation and peak inspiratory pressure are associated with mortality in pediatric acute respiratory distress syndrome. Since oxygenation and respiratory mechanics are linked, it is difficult to identify which variables, pressure or oxygenation, are independently associated with outcome. We aimed to determine whether respiratory mechanics (peak inspiratory pressure, positive end-expiratory pressure, ΔP [PIP minus PEEP], tidal volume, dynamic compliance [Cdyn]) or oxygenation (PaO2/FIO2) was associated with mortality.DesignProspective, observational, cohort study.SettingUniversity affiliated PICU.PatientsMechanically ventilated children with acute respiratory distress syndrome (Berlin).InterventionsNone.Measurements and main resultsPeak inspiratory pressure, positive end-expiratory pressure, ΔP, tidal volume, Cdyn, and PaO2/FIO2 were collected at acute respiratory distress syndrome onset and at 24 hours in 352 children between 2011 and 2016. At acute respiratory distress syndrome onset, neither mechanical variables nor PaO2/FIO2 were associated with mortality. At 24 hours, peak inspiratory pressure, positive end-expiratory pressure, ΔP were higher, and Cdyn and PaO2/FIO2 lower, in nonsurvivors. In multivariable logistic regression, PaO2/FIO2 at 24 hours and ΔPaO2/FIO2 (change in PaO2/FIO2 over the first 24 hr) were associated with mortality, whereas pressure variables were not. Both oxygenation and pressure variables were associated with duration of ventilation in multivariable competing risk regression.ConclusionsImprovements in oxygenation, but not in respiratory mechanics, were associated with lower mortality in pediatric acute respiratory distress syndrome. Future trials of mechanical ventilation in children should focus on oxygenation (higher PaO2/FIO2) rather than lower peak inspiratory pressure or ΔP, as oxygenation was more consistently associated with outcome.
| S-EPMC5474185 | biostudies-literature