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Few noninvasive biomarkers for pulmonary inflammation are currently available that can assess the lung-specific response to antiinflammatory treatments. Positron emission tomography with [(18)F]fluorodeoxyglucose (FDG-PET) is a promising new method that can be used to quantify pulmonary neutrophilic inflammation.To evaluate the ability of FDG-PET to measure the pulmonary antiinflammatory effects of hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) and recombinant human activated protein C (rhAPC) in a human model of experimentally-induced lung inflammation.Eighteen healthy volunteers were randomized to receive placebo, lovastatin, or rhAPC before intrabronchial segmental endotoxin challenge. FDG-PET imaging was performed before and after endotoxin instillation. The rate of [(18)F]FDG uptake was calculated as the influx constant K(i) by Patlak graphical analysis. Bronchoalveolar lavage (BAL) was performed to determine leukocyte concentrations for correlation with the PET imaging results.There was a statistically significant decrease in K(i) in the lovastatin-treated group that was not seen in the placebo-treated group, suggesting attenuation of inflammation by lovastatin treatment despite a small decrease in BAL total leukocyte and neutrophil counts that was not statistically significant. No significant decrease in K(i) was observed in the rhAPC-treated group, correlating with a lack of change in BAL parameters and indicating no significant antiinflammatory effect with rhAPC.FDG-PET imaging is a sensitive method for quantifying the lung-specific response to antiinflammatory therapies and may serve as an attractive platform for assessing the efficacy of novel antiinflammatory therapies at early phases in the drug development process. Clinical trial registered with www.clinicaltrials.gov (NCT00741013).

Objective: Acute respiratory distress syndrome is an abrupt inflammatory illness that involves damage from reactive oxygen species. We examined the efficacy and safety of oxothiazolidine-4-carboxylic acid (OTZ), a free radical scavenger, in treating acute respiratory distress syndrome. Design: Double-blind, placebo-controlled trial. Setting: Multicentered study. Patients: Patients with a Pa0 2 /FiO 2 ≤200 and bilateral infiltrates on chest radiograph, and requiring mechanical ventilation. Interventions: We randomized 215 patients to receive OTZ, 210 mg/kg per day every 8 hrs for 14 days or placebo. Measurements and Main Results: Ventilator-free days (the number of days alive and free from ventilator requirement) during the first 30 days of study were 8.3 vs. 13.5 days for the OTZ and placebo groups, respectively (p

Current methodologies for quantifying radiolabeled nucleoside monophosphates and nucleoside analogues result in high retention of unphosphorylated guanosine nucleosides in the case of lanthanum chloride precipitation or inconsistent retention of nucleotides in the case of DEAE cellulose filter papers. This study describes an innovative method for quantifying thymidine kinase (TK) activity that is compatible with both purine and pyrimidine nucleoside analogues by using lanthanum phosphate coprecipitation at pH 4.0. This methodology maintains quantitative precipitation of nucleoside monophosphates and yields minimal background binding from a variety of nucleoside analogues. In addition, use of PCR thermocyclers enhances the temporal precision of TK assays. This method was shown to be useful for assaying TK activity in a broad range of biochemically relevant systems, including purified enzymes, stable cell lines, and virally infected cells. Use of this methodology should aid researchers in the evaluation of novel nucleoside analogues and TK enzymes while decreasing radioactive waste, minimizing assay time, increasing accuracy, and enhancing dynamic range.

Recent advances in imaging offer exciting opportunities to develop and validate lung-specific biomarkers as valuable adjuncts to diagnosis, tests of treatment efficacy, and/or treatment monitoring. State-of-the-art structural, functional, and molecular imaging methods allow the lungs to be visualized noninvasively in vivo at submillimeter and subsecond spatial and temporal scales. However, the development and validation of imaging biomarkers present some special challenges, including the following: equipment evaluation, procedure standardization, data regarding reproducibility and replication, interrater variability, the production and measurement of reference standards, sensitivity to interventions or disease progression, intersubject variance, choice of image reconstruction and segmentation algorithms, automated versus observer-dependent image analysis, data acquisition during conditions of standardized lung volume, whether a reliable association can be demonstrated between the imaging biomarker and a clinical endpoint, and whether its use will have a favorable cost-effective impact on drug development or disease management. Establishing such performance characteristics, especially for single investigators at single institutions, can be daunting if not impossible for costly biomarkers such as imaging. Therefore, to take full advantage of the opportunities presented by state-of-the-art imaging methods, new approaches to analytic and clinical validation must be developed in collaboration with industry, foundation, and federal funding agencies.

This article reviews the potential use of positron emission tomography (PET), alone and in combination with computed tomography, for evaluating the severity of disease in cystic fibrosis. PET scanning using injected 18F-fluorodeoxyglucose provides visual and quantitative information for the rate at which glucose is taken up by the lung, a process that should relate to the presence of inflammation and reflect the extent of the disease. The computed tomography scan gives highly accurate density and anatomic information to locate areas of inflammation seen on the PET scan, increasing the accuracy of the interpretation. Until recently, the scanners have been single systems, often located in separate hospital departments. Combined systems are now commercially available, with major advantages for patients and in the quality of analytical information obtained for interpretation by the physician. The use of 18F-fluorodeoxyglucose uptake and PET scanning has been suggested as a biomarker of progressive pulmonary inflammation in cystic fibrosis. Although promising, the data so far are limited. Further studies will be needed to validate this measurement for this purpose.

The recently completed Fluid and Catheter Treatment Trial conducted by the National Institutes of Health ARDSNetwork casts doubt on the value of routine pulmonary artery catheterization for hemodynamic management of the critically ill. Several alternatives are available, and, in this review, we evaluate the theoretical, validation, and empirical databases for two of these: transpulmonary thermodilution measurements (yielding estimates of cardiac output, intrathoracic blood volume, and extravascular lung water) that do not require a pulmonary artery catheter, and hemodynamic measurements (including estimates of cardiac output and ejection time, a variable sensitive to intravascular volume) obtained by esophageal Doppler analysis of blood flow through the descending aorta. We conclude that both deserve serious consideration as a means of acquiring useful hemodynamic data for managing shock and fluid resuscitation in the critically ill, especially in those with acute lung injury and pulmonary edema, but that additional study, including carefully performed, prospective clinical trials demonstrating outcome benefit, is needed.

Rationale: Although infection contributes to morbidity in patients with cystic fibrosis (CF), the host inflammatory response is also an important cause of progressive pulmonary function deterioration. Quantifying the inflammatory burden in these patients is challenging and often requires invasive procedures. Positron emission tomographic imaging with [18F]fluorodeoxyglucose ([18FDG]) could be used as a noninvasive alternative to quantify lung inflammation. Objective: To determine the relationships among lung [18F]FDG uptake, bronchoalveolar lavage (BAL) neutrophil concentrations, and pulmonary function in patients with CF. Methods: Twenty patients and seven healthy volunteers were studied. A subset of seven patients also consented to undergo BAL. The uptake of [18F]FDG by the lungs was measured as the net influx rate constant Ki. Patients were stratified by rate of decline in pulmonary function into stable, intermediate, and rapidly declining groups. Ki was compared among groups and was correlated against neutrophil concentrations in BAL fluid. Results: Ki was significantly elevated (p < 0.05) among patients with CF as a whole compared with healthy control subjects (0.0015 ± 0.0009 versus 0.0007 ± 0.0002 ml blood/ml lung/min) but especially in patients with rapidly declining pulmonary function (0.0022 ± 0.0011 ml blood/ml lung/min). Ki correlated positively with the number of neutrophils present in BAL fluid. Conclusion: Imaging with [18F]fluorodeoxyglucose and positron emission tomography can be used to assess inflammatory burden in patients with CF. Elevations in Ki may be able to identify patients with more aggressive disease and may be useful in monitoring changes in inflammatory burden in response to novel treatments.

An emerging suite of new imaging techniques offer the ability to monitor and quantify molecular and cellular processes in the lungs noninvasively. These techniques take advantage of dramatic advances in both imaging technology as well as molecular and cell biology. Molecular imaging is being used with increasing regularity in research protocols, and forms of molecular imaging have found their way into the patient care setting (eg, positron emission tomography imaging in cancer). Such techniques will afford the basic scientist as well as the clinician an unprecedented opportunity for in vivo study of the lung biology that drives normal pulmonary physiology as well as pathophysiology.

To determine risk factors associated with an accelerated decline in lung function in cystic fibrosis (CF), and whether longitudinal changes in FEV(1) would be a better predictor of the need for referral for lung transplantation than any single value for FEV(1.)The rate of decline in pulmonary function was determined by standard linear regression from each patient's calendar year's best percentage of predicted FEV(1) (%FEV(1)) over at least 4 years, and patients were classified into three cohorts based on their rate of decline. Differences between groups in age, weight-for-age z score, gender, genotype, pancreatic status, diabetes, and the presence of various lung microbial isolates were analyzed. A subset of 30 patients referred for lung transplantation were further analyzed, and a prediction model for lung transplantation referral was created using the patient's rate of decline in lung function, the mean waiting time for donor organs, and the average level of lung function of patients prior to lung transplantation.One hundred fifty-three patients with CF followed up at the Washington University Adult Cystic Fibrosis Center.Younger age, malnutrition, and concurrent infection with both Pseudomonas aeruginosa and Staphylococcus aureus were significant (p0.05) risk factors for rapidly declining lung function. Among patients with rapidly declining lung function, referral for lung transplantation would have occurred 8.4 months earlier than actual referral age (p0.05) if the prediction model had been used, possibly resulting in additional patient salvage in several cases.Rate of decline in lung function should be routinely evaluated in patients with CF, and a prediction model utilizing the rate of decline in %FEV(1), and the median regional waiting period for donor lungs for patients with CF may assist in the timing of referral for lung transplantation and more rapidly declining lung function.

Bronchiolitis obliterans syndrome (BOS) is the major obstacle to long-term survival after lung transplantation, in part because its pathogenesis is poorly understood and treatment options are limited. To identify unique risk factors for BOS and death, we performed a retrospective cohort study on 259 consecutive adult lung transplant recipients over a 5-year period. The demographic and clinical characteristics of this population were analyzed for an association between BOS or death and potential risk factors, including community-acquired respiratory viral (CARV) infections, acute rejection, and cytomegalovirus pneumonitis. Respiratory syncytial virus, parainfluenza, influenza, and adenovirus accounted for 21 CARV infections. Univariate and multivariate time-dependent Cox regression analyses demonstrated that this CARV group was more likely to develop BOS, death, and death from BOS. Furthermore, these trends were more pronounced in patients with evidence of lower respiratory tract-CARV (lower-CARV) infections. Notably, the CARV and lower-CARV infections were risk factors for BOS, death, and death from BOS distinct from the risk attributable to acute rejection. Identification of CARV and lower-CARV infections as BOS and mortality risk factors has important clinical implications and may provide insight into disease pathogenesis and accelerate the development of novel treatment strategies to modify post-CARV BOS.

Molecular imaging is a rapidly developing multidisciplinary field that combines advances in contrast agent development, instrumentation, and molecular/cell biology to follow cellular and sub-cellular events in intact organisms. Platforms for molecular imaging include radionuclide-based methods, optical methods, and magnetic resonance. To date, molecular imaging studies of the lungs have been used to monitor the effectiveness of gene transfer, neutrophilic inflammation, and cell trafficking. Eventually, the goal will be to translate these new techniques to clinical settings such as cystic fibrosis.

Summary Characterization and non-invasive measurement of host–pathogen interactions in living cells, animal models and humans at the cellular and molecular levels is now possible using remote imaging detectors. Positron emission tomography scanners, highly sensitive cooled charge-coupled device cameras for bioluminescence and fluorescence imaging as well as high-magnetic-field magnetic resonance imaging scanners can be used to study such diverse processes as pathogen tropism, pathogen life cycle, signal transduction, host response, cell trafficking and gene transfer. In many cases, images from more than one modality can be fused, allowing structure–function and multifunction relationships to be studied on a tissue-restricted or regional basis. These new instruments, when used in conjunction with targeted contrast agents, reporter substrates and radiopharmaceuticals, enable ‘molecular imaging’ with enormous potential for elucidating host–pathogen interactions in intact animal models.

A new generation of imaging devices now make it possible to generate both structural and functional images for the study of lung biology in small animals, including common laboratory mouse and rat models. "Micro" X-ray computed tomography and positron emission tomography scanners, highly sensitive cooled charge coupled device cameras for bioluminescence and fluorescence imaging, high magnetic field magnetic resonance imaging scanners, and recent advances in ultrasound system technology can be used to study such diverse processes as ventilation, perfusion, pulmonary hypertension, lung inflammation, and gene transfer, among others. Images from more than one modality can also be fused, allowing structure-function and function-function relationships to be studied on a regional basis. These new instruments, part of an emerging suite of techniques collectively known as "molecular imaging," provide an enormous potential for elucidating lung biology in intact animal models and systems.

UNLABELLED: Small-dose endotoxin (Etx) prevents pulmonary perfusion redistribution away from edematous dorsal lung regions after oleic acid (OA)-induced injury in dogs, causing a significant deterioration in oxygenation. We hypothesized that small-dose Etx might mediate this effect via polymorphonuclear neutrophil (PMN) priming with release of inflammatory mediators such as platelet activating factor (PAF) or secretory phospholipase A(2) (sPLA(2)). To test this hypothesis, we administered specific inhibitors directed against each mediator and used two strategies to generate neutropenia. PAF and sPLA(2) inhibitors were administered before OA injury, followed 2 h later by small-dose Etx (n = 4 each group). PMN depletion was achieved by hydroxyurea administration for 5 days before the study to achieve absolute neutrophil counts

We evaluated positron emission tomographic imaging of pulmonary transgene expression, using an enhanced mutant herpes simplex virus-1 thymidine kinase as the reporter gene, in the lungs of normal rats. Sixteen rats were studied 3 days after an intratracheal administration of 5 x 10(9) to 1 x 10(11) viral particles of a replication-incompetent adenovirus containing a fusion gene of the mutant kinase and green fluorescent protein. Three rats infected with adenovirus containing no insert (null vector) served as control subjects. Images were obtained 1 hour after an intravenous injection of 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)guanine, an imaging substrate for the viral kinase. After euthanasia, tissue radioactivity was determined in a gamma counter, and thymidine kinase activity and green fluorescent protein levels were measured in lung tissue samples. Imaging and gamma counting radioactivity measurements were strongly and linearly correlated (r2 = 0.96, p0.001). Imaging detected thymidine kinase expression above background (null vector) in 15 of 16 rats, even at low viral doses that produced little to no measurable green fluorescent protein expression. Lung 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)guanine uptake (as assessed by imaging) correlated with in vitro assays of both kinase activity (r(2) = 0.48, p0.001) and fluorescent protein (r(2) = 0.46, p0.001). We conclude that positron emission tomographic imaging is a sensitive and quantitative method for detecting pulmonary reporter gene expression noninvasively.

We tested the hypothesis that the uptake of [18F]fluorodeoxyglucose (FDG), as measured by positron emission tomography (PET) imaging, would correlate with inflammation caused by increasing doses of instilled Pseudomonas aeruginosa (PA) into the lungs of mice. PA-laden agarose beads were instilled via the trachea into 1 lung of each mouse (dose range 0.5-15 x 10(4) CFU) and imaging was performed 3 days later (at the peak of the inflammatory response). Lung uptake of [18F]FDG correlated significantly with the dose of bacteria instilled in mice infected with the M57-15 strain of PA (n = 18) (r2 = .62), but not in mice infected with the PA01 strain (n = 20). The overall lung uptake of [18F]FDG was higher in mice infected with the M57-15 strain than in those infected with the PA01 strain (P.05). Total white blood cell concentrations in bronchoalveolar lavage were also higher in the M57-15-infected mice. We conclude that PET imaging can detect and quantify differences in host inflammatory response to 2 different strains of PA. The combination of PET imaging with murine models should be a useful new tool to study neutrophil trafficking and kinetics in lung inflammation.

Current entry rules for clinical trials of acute lung injury (ALI) depend on clinical criteria and arterial blood gas measurements. The objective of this study was to determine whether estimates of pulmonary vascular permeability could be used to more accurately identify patients with ALI for this purpose.Cross-sectional study in a university hosptial in a large metropolitan city.21 patients with noncardiogenic pulmonary edema, 7 patients with hydrostatic forms of pulmonary edema, and 10 healthy volunteers.Positron emission tomographic (PET) imaging with (68)Ga-labeled transferrin, or gamma-camera scintigraphy (gamma-S) with (99m)Tc-labeled albumin. All patients were studied within 24 h of onset, and all were selected exclusively on the basis of radiographic, not clinical, criteria. PET estimates of PTCER were used as a "gold standard."Radioactivity data were analyzed to compute the pulmonary transcapillary escape rate (PTCER) and the normalized slope index. PTCER by gamma-S was more strongly correlated to PTCER(PET) than normalized slope index by gamma-S. Although PTCER(gamma) was significantly correlated with PaO2/FIO2, it did not distinguish patients with noncardiogenic pulmonary edema from those with hydrostatic pulmonary edema.These data cast doubt on whether the gamma-S method can be used as a screening tool in clinical trials of ALI.

To investigate the role of hypoxic pulmonary vasoconstriction in the intrapulmonary blood flow redistribution and gas exchange protection during oleic acid acute lung injury.Prospective, controlled animal study.Research laboratory of an academic institution.Three groups of five mongrel dogs.Induction of acute lung injury by 0.08 mL/kg oleic acid intravenously. Hypoxic pulmonary vasoconstriction inhibition by Escherichia coli endotoxin microdose (15 microg/kg) pretreatment or by metabolic alkalosis (pH 7.60).Pulmonary arterial and venous resistances were determined by flow-pressure curves and by capillary pressure estimation. Regional lung water and pulmonary blood flow were assessed by positron emission tomography. Oleic acid alone increased the arterial and venous resistances, redistributed blood flow away from edematous areas, and decreased the Pao2 from 507 +/- 16 to 373 +/- 60 torr. on Fio2 1.0 and positive end-expiratory pressure 5 cm H2O. Endotoxin pretreatment inhibited the increase in arterial resistance, suppressed the redistribution, and decreased the Pao2 to 105 +/- 22 torr. Alkalosis inhibited the increase in arterial and venous resistances, suppressed the redistribution, and decreased the Pao2 to 63 +/- 12 torr. Reversal of the alkalosis increased the arterial and venous resistances, restored the perfusion redistribution, and improved the Pao2 to 372 +/- 63 torr. Changes in blood gases conformed to predictions of a computer lung model in which hypoxic pulmonary vasoconstriction was suppressed by endotoxin and alkalosis.We conclude that in oleic acid-induced lung injury, a) pulmonary hypertension results from increases in both arterial and venous resistances; b) the increase in arterial resistance is the primary mechanism responsible for the perfusion redistribution and the gas exchange protection; and c) the increase in arterial resistance is most consistent with hypoxic pulmonary vasoconstriction.

Recent studies have demonstrated significant synergistic physiological and biochemical effects between low-dose endotoxin (Etx) administration and oleic acid (OA)-induced canine lung injury. To evaluate whether this interaction depends on Etx priming of some key cell population, we compared the effects of giving low-dose Etx both after as well as before inducing lung injury with OA. In addition to hemodynamic and blood-gas measurements, positron emission tomographic imaging was used to measure edema accumulation and intrapulmonary blood flow distribution. Biochemical measurements of the stable metabolites of prostacyclin and thromboxane were obtained as well as measurements of isoprostanes and reactive sulfhydryls as evidence for possible concomitant oxidant production. We found that the physiological and biochemical effects of low-dose Etx developed 30–45 min after its administration, regardless of whether Etx was administered before or after OA. No increase in either isoprostane or reactive sulfhydryl production after Etx and/or OA was detected. These data suggest that the synergistic effect of low-dose Etx and OA-induced lung injury is not due to a priming effect of Etx.

Study objectives: To evaluate the chest radiographic filling pattern associated with partial liquid ventilation (PLV) with the perfluorochemical perflubron (LiquiVent; Alliance Pharmaceutical Corp; San Diego CA) as a function of dose and timing. Design: Post hoc review of chest radiographs by three independent observers with correlation to clinical variables. Setting: Phase II randomized, uncontrolled, prospective, multicenter clinical trial. Patients: Sixteen adult patients with diffuse bilateral infiltrates consistent with acute lung injury and a Pa o 2 /fraction of inspired oxygen (F io 2 ) ratio 2 O and F io 2 ≥ 0.5. Interventions: All patients were treated with either a 10-mL/kg or 20-mL/kg loading dose of perflubron followed by maintenance dosing at 3-h intervals to protocol-determined levels. Results: There was a significant relationship between inhomogeneous radiographic filling during the first 48 h of treatment and the use of the lower loading dose of perflubron. Inhomogeneous radiographic filling (in 5 patients) was associated with a lower high-dose/F io 2 ratio at 24 h compared with the remaining patients. These differences resolved by 48 h. There were no other statistically significant correlations identified. Conclusions: The radiographic appearance of PLV with perflubron appears to depend on the dose administered. Lower doses can be associated with both inhomogeneous radiographic filling and a transient deterioration in oxygenation during the first 24 to 48 h of treatment.

In many ways, the lung is an ideal organ for study with positron emission tomography (PET). First, structure-function relations are homogeneous over larger areas than in other organs (reducing problems associated with otherwise relatively poor spatial resolution and partial-volume averaging). Second, many physiologic and metabolic processes can be studied, including pulmonary blood flow, ventilation, vascular permeability, endothelial receptor and enzyme function, among others. A variety of radiotracers have been used to evaluate pulmonary blood flow with PET, including 68Ga- or 11C-albumin microspheres administered intravenously, H2 15O administered by i.v. infusion, and 13N-N2 administered by inhalation. Pulmonary ventilation has been evaluated with both 13N-N2 and 19Ne gas, also administered by inhalation. In general, the relative advantage of one approach over another depends on site-specific cyclotron capacity and experience, and on the nature and timing of concomitant studies with other positron-emitting radiopharmaceuticals. The various blood flow methods have been used primarily in studies of pulmonary gas exchange, in both experimental animals and in humans. Acute lung injury is usually defined by both an increase in extravascular water (pulmonary edema) and an increase in the permeability of the pulmonary endothelium to protein. Both processes can easily be evaluated with PET. Extravascular water is measured by a combination of scans with i.v. H2 15O and C15O. The latter is administered by inhalation to label the blood pool (to calculate intravascular water concentrations). Pulmonary vascular permeability has been evaluated with dynamic sequential imaging after either 68Ga-transferrin or 11C-methylalbumin infusions. The rate of uptake of either tracer into the pulmonary extravascular space is an index of "leakiness" of the pulmonary endothelium, and is quantified as the pulmonary transcapillary escape rate, or PTCER. PTCER appears to be a highly sensitive index of acute lung injury. Two receptor/ enzyme systems that have been evaluated include the beta-adrenergic receptor system (using 11CGP-12177 as the ligand) and angiotensin converting enzyme (using 18F-fluorocaptopril). In each case, the object is to measure Bmax, or the maximum binding-capacity for the ligand in question. Changes in Bmax can be used to infer changes in protein expression of the receptor or enzyme, or can be used to quantify adequacy of therapy with inhibitor drugs. Given the highly active nature of the pulmonary endothelium, it is likely that many other pulmonary receptor or enzyme systems can be studied in a similar fashion.

Primary pulmonary hypertension (PPH) is a disease characterized pathologically by pulmonary artery medial hypertrophy, adventitial thickening, and neointimal proliferation. Increasing recognition of the importance of remodeling to the pathogenesis of PPH suggests new therapeutic possibilities, but it will be necessary to (1) identify essential mediators of remodeling, and (2) demonstrate that inhibiting those mediators suppresses remodeling before new antiremodeling therapies can be considered feasible. The effect of angiotensin-converting enzyme (ACE) inhibition on pulmonary vascular remodeling was studied in a newly developed rat model in which neointimal lesions develop between 3 and 5 wk after monocrotaline injury is coupled with increased pulmonary artery blood flow after contralateral pneumonectomy. Neointimal formation was significantly suppressed at 5 wk by ACE inhibition whether it was started 10 d before or 3 wk after remodeling was initiated, although medial hypertrophy and adventitial thickening still developed. By 11 wk, the extent of neointimal formation in rats treated with ACE inhibition was similar to rats without ACE inhibition at 5 wk. Pulmonary artery pressures and right ventricular weights correlated with the extent of neointimal formation. Northern blot analysis and in situ hybridization demonstrated marked suppression of lung tropoelastin and type I procollagen gene expression in the presence of ACE inhibition. An angiotensin II type I receptor antagonist partially, but not completely, replicated the effects of ACE inhibition. These data suggest that the tissue angiotensin system may be a target for therapeutic efforts to suppress the vascular remodeling that is characteristic of primary pulmonary hypertension.

We evaluated the effects of low-dose endotoxin (15 microg/kg) on the pulmonary and systemic responses to oleic acid (OA)-induced acute lung injury in dogs. Animals given endotoxin alone (n = 5) showed a modest decrease in arterial blood pressure, but no effects on pulmonary hemodynamics, blood gases, cardiac output, or lung water accumulation. Animals (n = 6) given only OA (0.08 ml/kg) showed the expected development of mild-moderate pulmonary hypertension, a comparable reduction in arterial blood pressure, hypoxemia, increased lung water concentration, and an altered intrapulmonary perfusion pattern, as assessed by positron emission tomography. Animals (n = 7) given the same dose of endotoxin, followed 30 min later by the same dose of OA, developed a similar increase in lung water concentration as the group given OA alone, but failed to develop pulmonary hypertension or to redistribute pulmonary blood flow away from the edematous lung regions. In addition, arterial blood pressure fell significantly more than in the other groups. These responses were associated with a 30-fold increase in circulating prostacyclin (assayed as 6-keto prostaglandin F1 alpha [PGF1alpha]). The effects on systemic blood pressure, intrapulmonary blood flow redistribution, and eicosanoid production were eliminated by pretreating (n = 5) animals with meclofenamate (2 mg/kg). The results are consistent with a "priming" effect of low-dose endotoxin on the pulmonary endothelium, with exaggerated prostacyclin production in response to a subsequent lung injury. This interaction leads to altered intrapulmonary hemodynamics that exacerbate the development of hypoxemia, and to significant decreases in systemic blood pressure. To the extent that the lung is the most likely source of the increased prostacyclin production, the synergistic effects of low-dose endotoxin and lung injury may produce a kind of "lung shock."

In experimental models of acute lung injury, cyclooxygenase inhibition improves oxygenation, presumably by causing a redistribution of blood flow away from edematous lung regions. This effect on perfusion pattern could also reduce alveolar edema formation. On the other hand, pulmonary pressures usually increase after cyclooxygenase inhibition, an effect that could exacerbate edema accumulation. Therefore we tested the following hypothesis: the total accumulation of pulmonary edema in dogs during a 24- to 28-h period of observation after acute lung injury caused by oleic acid will be less in a group of animals treated with meclofenamate (n = 6) or with the thromboxane-receptor blocker ONO-3708 (n = 5) than in a group of animals treated with oleic acid alone (placebo, n = 6). Lung water concentrations (LWC), the regional pattern of pulmonary perfusion, and protein permeability were measured with the nuclear medicine imaging technique of positron emission tomography. After 24-28 h, LWC was significantly less (P < 0.05) in the ONO-3708 group than in the meclofenamate group (a similar trend was seen compared with the placebo group, P = 0.12). After 24-28 h, pulmonary arterial pressures were highest in the meclofenamate group. Regardless of group, the only significant correlation with the change in LWC was with the integral of pulmonary pressures over the 24- to 28-h period. The data suggest that thromboxane inhibition will reduce edema accumulation in acute lung injury but that this effect depends on reducing as much as possible the simultaneous development of pulmonary hypertension from other causes.

We measured pulmonary angiotensin-converting enzyme (ACE) kinetics with fluorine-18 captopril and positron emission tomographic (PET) imaging in five control dogs and in five dogs after 20–30 min of left caudal lobe (LCL) hypoxic ventilation. Time-activity data obtained with PET were interpreted with a compartmental receptor model relating changes in tissue and blood activity to one another within the region. In control dogs, the mean ratio of regional blood flow (measured by PET) between left and right dorsal lung regions was 0.90 +/- 0.16 (SD) vs. 0.54 +/- 0.24 (P < 0.05) in LCL hypoxic dogs. In control dogs, the amount of perfused unbound enzyme normalized to regional extravascular water concentration (Bmax/EVLW) averaged 13.3 +/- 8.9 x 10(-6) mmol ACE/ml EVLW; the ratio of regional values between the left and right sides was 1.02 +/- 0.18. In the LCL hypoxic dogs, Bmax/EVLW was 9.7 +/- 11.3 x 10(-6) mmol/ml hypoxic lung region and the ratio was 0.47 +/- 0.31 (P < 0.05). In control dogs, the coefficient of variation for Bmax/EVLW among regions was only 19 +/- 10%, although the between-dog variation was greater (64 +/- 4%). We conclude that this completely noninvasive method appears to be a promising approach for evaluating the expression of pulmonary ACE in vivo.

Although recent X-ray computed tomography (CT) data show that ventral-dorsal gradients in density are common in the adult respiratory distress syndrome (ARDS), we hypothesized that the ventral-dorsal gradient of pulmonary vascular permeability would be evenly distributed in patients with ARDS. We tested this hypothesis by analyzing previously reported data (Am Rev Respir Dis 1991; 143:150–154) obtained by the nuclear medicine imaging technique of positron emission tomography (PET). Measurements of regional lung density (LD), extravascular density (EVD), and the pulmonary transcapillary escape rate (PTCER; an index of vascular permeability) were obtained in eight patients with ARDS and in 10 normal subjects. The data from four contiguous tomographic slices were organized into 20 anatomically oriented “bins” from the ventral (Bin #1) to dorsal (Bin #20) position. Mean overall LD, ERD, and PTCER were all significantly higher (p < 0.05) in the ARDS patients than in normal subjects. Regression slopes of LD ver...

Purpose: To determine whether positive end-expiratory pressure (PEEP) would change the altered regional pulmonary perfusion pattern caused by oleic acid (OA)-induced acute lung injury was the aim of this study. Our hypothesis was that fixed intravascular obstruction would not be affected by PEEP, leaving the perfusion pattern unchanged if this was the principal cause of perfusion redistribution after lung injury. Methods: Regional measurements of pulmonary perfusion and lung water concentration (LWC) were obtained both before and after lung injury and before and after PEEP (10 cm H2O) with the nuclear medicine imaging technique of positron emission tomography after injections of H215O in 7 supine anesthetized dogs. Four animals were also treated with meclofenamate to enhance perfusion redistribution after acute lung injury. Results: The application of PEEP before lung injury did not significantly affect the regional perfusion pattern. After administration of OA, LWC increased and fractional flow (without PEEP) decreased to the most edematous lung regions, consistent with perfusion redistribution. With the reapplication of PEEP, the perfusion pattern reverted toward the baseline pattern. The magnitude of this effect was roughly proportional to the effect of PEEP on regional inflation (r = .53), as evidenced by changes in LWC. Conclusions: The reversibility with PEEP of the perfusion pattern caused by acute lung injury suggests that fixed intravascular obstruction is not the principal determinant of perfusion redistribution after OA-induced injury.

The accurate prediction of patient-specific outcomes is, and will continue to be, an important area of medical investigation. Physicians, health care administrators, government agencies, and insurance companies all require accurate and assessable data on which to base their decision-making processes. Within intensive care units, refinements in our ability to identify important data, collect and process the data accurately and inexpensively, and make the data readily available to those wishing access to it will be the focus of future research efforts. Advances in computer technology and the application of outcome research methods to critical care should assist in achieving these goals.

Perfusion redistribution (PR) after acute oleic acid (OA) lung injury may be the result of changes in the tissue concentration ratio of thromboxane (Tx) and prostacyclin (A. H. Stephenson et al. J. Appl. Physiol. 73: 2126–2134, 1992). We tested this hypothesis by determining whether the Tx mimetic U-46619 would mimic PR caused by cyclooxygenase inhibition with meclofenamate and whether the Tx receptor antagonist ONO-3708 would inhibit PR even in the presence of meclofenamate. Measurements of regional pulmonary blood flow (PBF) and lung water concentration were made with the nuclear medicine imaging technique of positron emission tomography. Measurements were made at baseline and 2 h after OA. At baseline, the spatial distribution of PBF was similar in all experimental groups. Two hours after OA, fractional PBF was reduced to the edematous lung in all groups given OA, but the magnitude of change was greater in those groups receiving meclofenamate or U-46619 compared with the change in the group given OA only. Thus, although the Tx mimetic produced the same amount of PR as meclofenamate, Tx inhibition did not prevent PR after meclofenamate. Therefore, the ratio of Tx to prostacyclin per se is not the critical determinant of PR.

Positron emission tomography (PET) can be used to evaluate pulmonary vascular endothelial permeability by measuring the pulmonary transcapillary escape rate (PTCER) for radiolabeled transferrin. Because epithelial permeability, as evaluated by other techniques, is significantly affected by cigarette smoking, we used PET to compare the effects of smoking on extravascular lung density (EVD) and PTCER in seven normal chronic cigarette smokers within 30 min of smoking a cigarette and seven normal nonsmokers. We found no difference in PTCER and EVD between the two groups. We conclude that the interpretation of acute or chronic lung injury studies with PET should not be affected by cigarette smoking in the subject population.

Study Objective: To evaluate the importance of fluid balance and changes in extravascular lung water (EVLW) on survival in the ICU and short-term outcome in patients with pulmonary edema. Design: Retrospective analysis of data (sorting by survival and “treatment received”) from a recent randomized controlled trial of fluid restriction in this population. Setting: Medical ICU of a university-affiliated, tertiary-care medical center. Patients: Eighty-nine patients (from the previously mentioned study) requiring pulmonary artery catheterization with abnormally high EVLW (>7 ml/kg). Measurements and Results: When analyzed by survival, the survivors had no significant fluid gain or change in EVLW but decreased wedge pressure and body weight, compared to nonsurvivors. When analyzed by fluid balance, patients who gained less than 1 L of fluid by 36 hours into the study had a better rate of survival (74 percent) than the rest (50 percent; p Conclusions: These data support the concept that positive fluid balance per se is at least partially responsible for poor outcome in patients with pulmonary edema and defend the strategy of attempting to achieve a negative fluid balance if tolerated hemodynamically.

Many principles that originate in the operating room and in fluid mechanics modeling are relevant to endotracheal intubation in the pulmonary and critical care setting. These factors should be appreciated by pulmonologists and intensivists, as they may contribute to improved safety during the process of airway access. The usual reflex responses to stimulation of oropharyngeal and upper airway receptors include glottic closure, hypertension, tachycardia, and reflex bronchoconstriction. These reflexes can be modified by technical or pharmacologic reduction of sensory receptor stimulation or by parenteral agents, which diminish efferent responses, including anesthetics, vasoactive drugs, and adrenergic blockers. Topical anesthesia and parenteral sedatives may be the preferred agents when overall risk and benefit are considered. Intubation also has consequences related to a reduction in airway caliber, to changes in respiratory mechanics, and to the creation of turbulent airflow in the endotracheal tube.

The effect of body position on regional pulmonary blood flow (rPBF) and lung water concentration (rLWC) was studied before and after canine oleic acid (OA)-induced acute lung injury. Regional measurements were made with positron emission tomography. Eleven supine and five prone dogs were studied. In supine animals, LWC increased significantly 60 minutes after OA, primarily in gravity-dependent dorsal lung regions, with a small but still significant additional change over the next 75 minutes. Despite some redistribution, a disproportionate amount of blood flow continued to go to regions with the greatest lung water accumulation. In the prone group, LWC and rPBF were more evenly distributed than in the supine animals, both before and after lung injury. Furthermore, in the prone position, and in contrast to the supine position, regions with the greatest LWC had the least fractional flow. Thus, the benefits of the prone position on oxygenation are related to both the spatial distribution of lung water accumulation and regional pulmonary blood flow.

Biopharmaceuticals, such as proteins and DNA, have demonstrated their potential to prevent and cure diseases. The success of such therapeutic agents hinges upon their ability to cross complex barriers in the body and reach their target intact. In order to reap the full benefits of these therapeutic agents, a delivery vehicle capable of delivering cargo to all cell types, both phagocytic and non-phagocytic, is needed. This article presents the synthesis and evaluation of a microparticle delivery vehicle capable of cell penetration and sub-cellular triggered release of an encapsulated payload. pH-sensitive polyacrylamide particles functionalized with a polyarginine cell-penetrating peptide (CPP) were synthesized. The incorporation of a CPP into the microparticles led to efficient uptake by non-phagocytic cells in culture. In addition, the CPP-modified particles showed no cytotoxic effects at concentrations used in this study. The results suggest that these particles may provide a vehicle for the successful delivery of therapeutic agents to various cell types.

In 11 supine dogs, we related regional lung water concentration (rLWC) measurements made with positron emission tomography (PET) after canine oleic acid (OA)-induced acute lung injury to extravascular lung water measurements by the thermal-green dye indicator dilution technique (EVLW-TGD), and to measurements of vascular permeability (also by PET) and hydrostatic pressure. The rLWC measurements correlated well with EVLW-TGD (R 2 = 97%). Changes in LWC did not correlate with either the pulmonary wedge pressure or PET measurements of protein leak (as an index of vascular permeability), but were related when both variables were considered together (R 2 = 73%). Lung water concentration increased significantly 60 minutes after OA, primarily in dorsal, gravity-dependent lung regions, with a small, but statistically significant, change over the next 75 minutes. These data suggest that PET measurements of LWC or EVLW on one tomography slice can be representative of changes in EVLW in the lung as a whole after diffuse lung injury. Furthermore, the magnitude of edema accumulation after acute lung injury can be accurately predicted by quantitative measurements of hydrostatic pressure and of protein leak using PET.

We used positron emission tomography to evaluate the effects of nitroprusside or prostacyclin (NP/Prost) on regional pulmonary blood flow (rPBF) in 21 dogs after oleic acid- (OA) induced acute pulmonary edema and compared the results with data from 11 dogs given OA only and 5 given meclofenamate after OA. After OA only, a progressive decrease in rPBF occurred in edematous gravity-dependent lung regions, but only in 6 of 11 dogs. In these six dogs, rPBF fell 41 +/- 12% compared with base line or with the other five dogs (3 +/- 19%) (P less than 0.05). In the NP/Prost group, the vasodilators failed to reverse any change in rPBF after OA but did prevent additional derecruitment until the drug infusion was stopped, after which rPBF to the edematous regions decreased further. In contrast, meclofenamate after OA temporally accelerated but did not quantitatively enhance rPBF reduction in edematous lung regions. Thus, in this model, vessels in edematous lung regions remain vasoreactive only until derecruited. We speculate that the mechanism of derecruitment involves an interaction between edema accumulation and vasoconstriction, in which the actual pattern of rPBF after lung injury represents a balance between mechanisms responsible for vascular derecruitment and vasodilation from prostacyclin production.

Using techniques of mathematical simulation, we compared two methods of evaluating pulmonary vascular permeability, i.e., transvascular protein flux. Both methods calculate a transport rate constant [pulmonary transcapillary escape rate (PTCER)] after making external radiation detection measurements of an intravenously administered radiolabeled protein. With one method, lung tissue time-activity data are acquired by positron emission tomography (PET) and are interpreted with a two-compartment model. With the other method, the time-activity data are acquired with simple detector probes and are interpreted by linear regression after normalizing for various physical factors (slope-intercept or SI method). The results show that significant errors in calculating PTCER can result from using the SI method, because it ignores the effects of back-flux on the tissue time-activity measurements. Both methods produce errors if the data analysis includes activity from vascular volumes not involved in tracer exchange with the extravascular compartment. Significant errors can also occur with the PET method, particularly when permeability is nearly normal, if pulmonary vascular volume changes significantly during the period of data collection. On balance, the PET method appears to be the method of choice for accurately evaluating pulmonary vascular permeability by protein flux measurements, although both methods may be useful in clinical applications.

Nanoparticles (NPs) targeting the intercellular adhesion molecule 1 (ICAM-1) hold promise as a mean of delivering therapeutics to the pulmonary endothelium in patients with acute and chronic respiratory diseases. As these new materials become available, strategies are needed to understand their behavior in vivo. We have evaluated the use of 64Cu and PET to noninvasively image the lung uptake and distribution of NPs coated with an anti-ICAM antibody. Methods: Model fluorescent NPs were coated with a mixture of an anti-ICAM antibody (or nonspecific IgG) and 64Cu-DOTA-IgG (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). Biodistribution and small-animal PET and CT studies were performed in healthy mice and in mice pretreated with lipopolysaccharides (LPSs). Metabolism studies were also performed to evaluate the stability of 64Cu-labeled NPs in lungs in vivo. Results: The lungs of mice administered anti-ICAM NPs labeled with 64Cu were clearly imaged by small-animal PET 1, 4, and 24 h after administration. Both biodistribution and small-animal imaging showed a 3- to 4-fold higher uptake in the lungs of mice injected with ICAM-targeted NPs relative to that of the control group. Lung uptake was further enhanced by pretreating the mice with LPS, presumably because of ICAM-1 upregulation. However, an approximately 2-fold decrease in lung signal was observed in each experimental group over 24 h. Metabolism studies in lung tissues harvested from mice injected with 64Cu-labeled anti-ICAM NPs showed considerable release of a small 64Cu-radiometabolite from the NPs beginning as early as 1 h after injection. A decrease in lung fluorescence was also observed, most likely reflecting partial release of NPs from the lungs in vivo. Conclusion: The use of small-animal PET to track 64Cu-labeled nanostructures in vivo shows potential as a strategy for the preclinical screening of new NP drug delivery agents targeting the lung endothelium and other tissues. Future design optimization to prolong the stability of the radiolabel in vivo will further improve this promising approach.