The American-European Consensus Conference on ARDS, part 2: Ventilatory, pharmacologic, supportive therapy, study design strategies, and issues related to recovery and remodeling. Acute respiratory distress syndrome

Centers for disease control and prevention expert panel meetings on prevention and treatment of anthrax in adults

The Centers for Disease Control and Prevention convened panels of anthrax experts to review and update guidelines for anthrax postexposure prophylaxis and treatment. The panels included civilian and military anthrax experts and clinicians with experience treating anthrax patients. Specialties represented included internal medicine, pediatrics, obstetrics, infectious disease, emergency medicine, critical care, pulmonology, hematology, and nephrology. Panelists discussed recent patients with systemic anthrax; reviews of published, unpublished, and proprietary data regarding antimicrobial drugs and anthrax antitoxins; and critical care measures of potential benefit to patients with anthrax. This article updates antimicrobial postexposure prophylaxis and antimicrobial and antitoxin treatment options and describes potentially beneficial critical care measures for persons with anthrax, including clinical procedures for infected nonpregnant adults. Changes from previous guidelines include an expanded discussion of critical care and clinical procedures and additional antimicrobial choices, including preferred antimicrobial drug treatment for possible anthrax meningitis.

Can we optimize long-term outcomes in acute respiratory distress syndrome by targeting normoxemia?

Since its original description in 1967, acute respiratory distress syndrome (ARDS) has been recognized as a devastating condition associated with significant morbidity and mortality. Advances in critical care medicine and ARDS management have led to a substantial increase in the number of ARDS survivors. Long-term cognitive impairment after critical illness is a significant public health concern. ARDS survivors frequently experience long-term cognitive impairment, as well as physical impairment, psychiatric morbidity, and reduced health-related quality of life. At present, no intensive care unit-based intervention has been proven to reduce the risk of long-term cognitive impairment after ARDS. To address the urgent need to identify strategies to preserve long-term health, investigators have advocated the measurement of short- and long-term outcomes in clinical trials. Maintaining adequate oxygen delivery to preserve organ function is of vital importance in ARDS management. The optimal target range for arterial oxygenation in ARDS remains unknown, due in part to the challenge to maintain adequate tissue oxygenation and to minimize harm, such as oxygen toxicity. An approach targeted to subnormal oxygenation values (partial pressure of arterial oxygen, 55-80 mm Hg) has emerged as a means to accomplish these aims. In this perspective, we critically evaluate this strategy from short- and long-term perspectives, with a focus on the potential long-term cognitive effects of the strategy. We conclude with a proposal to consider resetting the target range for arterial oxygenation higher (85-110 mm Hg) as a potential strategy to improve the long-term outcomes of ARDS survivors.

Respiratory and hemodynamic effects of a stepwise lung recruitment maneuver in pediatric ARDS: a feasibility study

BACKGROUND

Little is known about the efficacy and safety of recruitment maneuvers (RMs) in pediatric patients with acute respiratory distress syndrome (ARDS). We therefore assessed the effects on gas exchange and lung mechanics and the possible detrimental effects of a sequential lung RMs and decremental positive end-expiratory pressure (PEEP) titration in pediatric ARDS patients.

METHODS

We enrolled patients <15 years of age with ARDS, progressive hypoxemia, <72 hr of mechanical ventilation, and hemodynamic stability. A step-wise RM and decremental PEEP trial were performed. Safety was evaluated as the occurrence of hypotension and low pulse oxymeter oxygen saturation during the maneuver and development of airleaks after. Efficacy was evaluated as changes in lung compliance (Cdyn ) and gas exchange 1, 12, and 24 hr after the RM.

RESULTS

We included 25 patients, of median age 5 (1-16) months, median weight 7.0 (4.1-9.2) kg, median PaO2 /FIO2 117 (96-139), and median Cdyn 0.48 (0.41-0.68) ml/cmH2 O/kg at baseline. Thirty RM were performed, with all completed successfully. No airleaks developed. Mild hypotension was detected during four procedures. Following RM, Cdyn , and PaO2 /FIO2 increased significantly (P < 0.01 each), without changes in PaCO2 (P = 0.4). A >25% improvement in lung function (Cdyn or PaO2 /FIO2 ) was observed after 90% of the RM procedures. Gas exchange worsening over the next 24 hr resulted in HFOV use in 36% of patients, while the remaining subjects sustained improvements in oxygenation at 12 and 24 hr. The 28-day mortality rate was 16%.

CONCLUSIONS

Sequential RMs were safe and well tolerated in hemodynamically stable children with ARDS. RMs and a decremental PEEP trial may improve lung function in pediatric patients with ARDS and severe hypoxemia.

Protective effects of alpha-lipoic Acid on oleic Acid-induced acute lung injury in rats

BACKGROUND

Oxidative stress is believed to be an important factor in the pathogenesis of acute lung injury (ALI).

AIMS

The aim of this study was to investigate the possible protective role of alpha-lipoic acid (α-LA) on oleic acid (OA)-induced ALI in rats.

STUDY DESIGN

Animal experiment.

METHODS

A total of thirty-five rats were divided into five groups in the study. Group 1 served as a control group. Rats in Group 2 (α-LA) were administered α-LA intraperitoneally at a dose of 100 mg/kg body weight (BW). Rats in Group 3 (OA) were administered OA intravenously at a dose of 100 mg/kg BW. In Group 4 (pre-OA-α-LA), α-LA was given 15 minutes prior to OA infusion, and in Group 5 (post-OA-α-LA), α-LA was given two hours after OA infusion. Four hours after the OA infusion, rats were decapitated. Blood samples were collected to measure serum levels of malondialdehyde (MDA) and glutathione (GSH), and the levels of activity for superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). Lung tissue samples were taken for histopathological examination.

RESULTS

Exposure to OA resulted in increases in serum MDA levels (p<0.001), as well as histopathological lesions in lung tissue, and decreases in CAT (p<0.05), GSH-Px (p<0.05) activities and GSH (p<0.05) levels. On the other hand, MDA levels were decreased significantly (p<0.001), while CAT (p<0.05), GSH-Px (p<0.01) activities and GSH (p<0.05) levels were increased significantly in the pre-OA-α-LA group compared with the OA group.

CONCLUSION

α-LA was found to lessen oxidative stress and to have positive effects on antioxidants in cases of OA-induced ALI. In conclusion, α-LA appears to have protective effects against ALI and potential for the prevention of ALI.

Impact of immunoreactive substances contained in apheresis platelet concentrate on postoperative respiratory function in surgical patients receiving platelet transfusion: a prospective cohort study

OBJECTIVES

To construct an alternative policy for the donor selection of platelet concentrate (PC), a clinical study exploring the features of lung injury following PC administration is needed.

BACKGROUND

Although a male-donor-only policy for plasma products appears to have efficiently reduced transfusion-related acute lung injury (TRALI), this policy may not be applied to PC because of supply shortages.

METHODS AND MATERIALS

We prospectively examined pulmonary function after the transfusion of PC in informed surgical patients treated at a tertiary university hospital in Japan. The contributions of immunoreactive substances contained in the PC to respiratory function after PC transfusion was then statistically examined.

RESULTS

Eighty-six patients (56 men, 30 women) were enrolled in the analysis. Fifty-four cases experienced respiratory failure (PaO2 /FiO2 <300 mmHg) after transfusion. Five cases were diagnosed as possible TRALI based on permeability pulmonary oedema, while 23 cases were diagnosed as transfusion-associated circulatory overload (TACO) based on chest radiograph findings. A multivariate logistic regression analysis identified the presence of anti-granulocyte antibody as a significant predictor of possible TRALI [P = 0.023; odds ratio (OR), 13.0; 95% confidence interval (CI), 1.4-118.3]. Meanwhile, anti-leukocyte antibody class II was identified as a significant independent predictor of TACO (P = 0.010; OR, 18.4; 95% CI, 2.0-170.1).

CONCLUSIONS

Our data suggest that antibodies contained in PC may contribute to the deterioration of respiratory function after PC transfusion, although the diagnoses of TACO and TRALI may have overlapped among the patients with pulmonary distress in this cohort.

Vitamin D to prevent acute lung injury following oesophagectomy (VINDALOO): study protocol for a randomised placebo controlled trial

Background

Acute lung injury occurs in approximately 25% to 30% of subjects undergoing oesophagectomy. Experimental studies suggest that treatment with vitamin D may prevent the development of acute lung injury by decreasing inflammatory cytokine release, enhancing lung epithelial repair and protecting alveolar capillary barrier function.

Methods/Design

The ‘Vitamin D to prevent lung injury following oesophagectomy trial’ is a multi-centre, randomised, double-blind, placebo-controlled trial. The aim of the trial is to determine in patients undergoing elective transthoracic oesophagectomy, if pre-treatment with a single oral dose of vitamin D₃ (300,000 IU (7.5 mg) cholecalciferol in oily solution administered seven days pre-operatively) compared to placebo affects biomarkers of early acute lung injury and other clinical outcomes. The primary outcome will be change in extravascular lung water index measured by PiCCO® transpulmonary thermodilution catheter at the end of the oesophagectomy. The trial secondary outcomes are clinical markers indicative of lung injury: PaO₂:FiO₂ ratio, oxygenation index; development of acute lung injury to day 28; duration of ventilation and organ failure; survival; safety and tolerability of vitamin D supplementation; plasma indices of endothelial and alveolar epithelial function/injury, plasma inflammatory response and plasma vitamin D status. The study aims to recruit 80 patients from three UK centres.

Discussion

This study will ascertain whether vitamin D replacement alters biomarkers of lung damage following oesophagectomy.

Trial registration

Current Controlled Trials ISRCTN27673620

Chlamydial pneumonitis: a creepy neonatal disease

We present a case of neonatal chlamydial pneumonitis to illustrate that a high index of suspicion is necessary to make the diagnosis so that treatment can be promptly instituted. The child was afebrile and the only symptom was a cough. The respiratory equations are calculated to understand the respiratory physiology. There was no overt abnormality with ventilation, oxygenation, compliance, resistance, or ventilation-perfusion mismatch despite radiographic abnormality. The literature is searched to review if treatment with a systemic macrolide antibiotic is needed in an otherwise asymptomatic neonate with chlamydial pneumonitis.

Emergency neurological life support: airway, ventilation, and sedation

Airway management is central to the resuscitation of the neurologically ill. These patients often have evolving processes that threaten the airway and adequate ventilation. Therefore, airway, ventilation, and sedation were chosen as an Emergency Neurological Life Support (ENLS) protocol. Reviewed topics include airway management; the decision to intubate; when and how to intubate with attention to cardiovascular status; mechanical ventilation settings; and the use of sedation, including how to select sedative agents based on the patient's neurological status.

High-frequency ventilation versus conventional ventilation for treatment of acute lung injury and acute respiratory distress syndrome

BACKGROUND

High frequency oscillation is an alternative to conventional mechanical ventilation that is sometimes used to treat patients with acute respiratory distress syndrome, but effects on oxygenation, mortality and adverse clinical outcomes are uncertain. This review was originally published in 2004 and was updated in 2011.

OBJECTIVES

To determine clinical and physiological effects of high frequency oscillation (HFO) in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) compared to conventional ventilation.

SEARCH METHODS

We electronically searched CENTRAL (Ovid), MEDLINE (Ovid), EMBASE (Ovid), and ISI (from inception to March 2011). The original search was performed in 2002. We manually searched reference lists from included studies and review articles; searched conference proceedings of the American Thoracic Society (1994 to 2010), Society of Critical Care Medicine (1994 to 2010), European Society of Intensive Care Medicine (1994 to 2010), and American College of Chest Physicians (1994 to 2010); contacted clinical experts in the field; and searched for unpublished and ongoing trials in clinicaltrials.gov and controlled-trials.com.

SELECTION CRITERIA

Randomized controlled clinical trials comparing treatment using HFO with conventional mechanical ventilation for children and adults diagnosed with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data on clinical, physiological, and safety outcomes according to a predefined protocol. We contacted investigators of all included studies to clarify methods and obtain additional data. We used random-effects models in the analyses.

MAIN RESULTS

Eight RCTs (n = 419) were included; almost all patients had ARDS. The risk of bias was low in six studies and unclear in two studies. The quality of evidence for hospital and six-month mortality was moderate and low, respectively. The ratio of partial pressure of oxygen to inspired fraction of oxygen at 24, 48, and 72 hours was 16% to 24% higher in patients receiving HFO. There were no significant differences in oxygenation index because mean airway pressure rose by 22% to 33% in patients receiving HFO (P < 0.01).  In patients randomized to HFO, mortality was significantly reduced (RR 0.77, 95% CI 0.61 to 0.98; P = 0.03; 6 trials, 365 patients, 160 deaths) and treatment failure (refractory hypoxaemia, hypercapnoea, hypotension, or barotrauma) was less likely (RR 0.67, 95% CI 0.46 to 0.99; P = 0.04; 5 trials, 337 patients, 73 events). Other risks, including adverse events, were similar. We found substantial between-trial statistical heterogeneity for physiological (I(2) = 21% to 95%) but not clinical (I(2) = 0%) outcomes.  Pooled results were based on few events for most clinical outcomes.

AUTHORS' CONCLUSIONS

The findings of this systematic review suggest that HFO was a promising treatment for ALI and ARDS prior to the uptake of current lung protective ventilation strategies. These findings may not be applicable with current conventional care, pending the results of large multi-centre trials currently underway.

Cyclic arginine-glycine-aspartate attenuates acute lung injury in mice after intestinal ischemia/reperfusion

Introduction

Intestinal ischemia is a critical problem resulting in multiple organ failure and high mortality of 60 to 80%. Acute lung injury (ALI) is a common complication after intestinal ischemia/reperfusion (I/R) injuries and contributes to the high mortality rate. Moreover, activated neutrophil infiltration into the lungs is known to play a significant role in the progression of ALI. Integrin-mediated interaction is involved in neutrophil transmigration. Synthetic peptides containing an arginine-glycine-aspartate sequence compete with adhesive proteins and inhibit integrin-mediated interaction and signaling. Thus, we hypothesized that the administration of a cyclic arginine-glycine-aspartate peptide (cRGD) inhibited neutrophil infiltration and provided protection against ALI induced by intestinal I/R.

Methods

Ischemia in adult male C57BL/6 mice was induced by fastening the superior mesenteric artery with 4-0 suture. Forty-five minutes later, the vascular suture was released to allow reperfusion. cRGD (5 mg/kg body weight) or normal saline (vehicle) was administered by intraperitoneal injection 1 hour prior to ischemia. Blood, gut, and lung tissues were collected 4 hours after reperfusion for various measurements.

Results

Intestinal I/R caused severe widespread injury to the gut and lungs. Treatment with cRGD improved the integrity of microscopic structures in the gut and lungs, as judged by histological examination. Intestinal I/R induced the expression of β₁, β₂ and β₃ integrins, intercellular adhesion molecule-1, and fibronectin. cRGD significantly inhibited myeloperoxidase activity in the gut and lungs, as well as neutrophils and macrophages infiltrating the lungs. cRGD reduced the levels of TNF-α and IL-6 in serum, in addition to IL-6 and macrophage inflammatory protein-2 in the gut and lungs. Furthermore, the number of TUNEL-staining cells and levels of cleaved caspase-3 in the lungs were significantly lowered in the cRGD-treated mice in comparison with the vehicle mice.

Conclusions

Treatment with cRGD effectively protected ALI and gut injury, lowered neutrophil infiltration, suppressed inflammation, and inhibited lung apoptosis after intestinal I/R. Thus, there is potential for developing cRGD as a treatment for patients suffering from ALI caused by intestinal I/R.

Oleic acid induces lung injury in mice through activation of the ERK pathway

Oleic acid (OA) can induce acute lung injury in experimental models. In the present work, we used intratracheal OA injection to show augmented oedema formation, cell migration and activation, lipid mediator, and cytokine productions in the bronchoalveolar fluids of Swiss Webster mice. We also demonstrated that OA-induced pulmonary injury is dependent on ERK1/2 activation, since U0126, an inhibitor of ERK1/2 phosphorylation, blocked neutrophil migration, oedema, and lipid body formation as well as IL-6, but not IL-1β production. Using a mice strain carrying a null mutation for the TLR4 receptor, we proved that increased inflammatory parameters after OA challenges were not due to the activation of the TLR4 receptor. With OA being a Na/K-ATPase inhibitor, we suggest the possible involvement of this enzyme as an OA target triggering lung inflammation.

Distinct and replicable genetic risk factors for acute respiratory distress syndrome of pulmonary or extrapulmonary origin

BACKGROUND

The role of genetics in the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) from direct or indirect lung injury has not been specifically investigated. The aim of this study was to identify genetic variants contributing to ALI/ARDS from pulmonary or extrapulmonary causes.

METHODS

We conducted a multistage genetic association study. We first performed a large-scale genotyping (50K ITMAT-Broad_CARe Chip) in 1717 critically ill Caucasian patients with either pulmonary or extrapulmonary injury, to identify single nucleotide polymorphisms (SNPs) associated with the development of ARDS from direct or indirect insults to the lung. Identified SNPs (p≤0.0005) were validated in two separated populations (Stage II), with trauma (Population I; n=765) and pneumonia/pulmonary sepsis (Population II; n=838), as causes for ALI/ARDS. Genetic variants replicating their association with trauma related-ALI in Stage II were validated in a second trauma-associated ALI population (n=224, Stage III).

RESULTS

In Stage I, non-overlapping SNPs were significantly associated with ARDS from direct/indirect lung injury, respectively. The association between rs1190286 (POPDC3) and reduced risk of ARDS from pulmonary injury was validated in Stage II (p<0.003). SNP rs324420 (FAAH) was consistently associated with increased risk of ARDS from extrapulmonary causes in two independent ALI-trauma populations (p<0.006, Stage II; p<0.05, Stage III). Meta-analysis confirmed these associations.

CONCLUSIONS

Different genetic variants may influence ARDS susceptibility depending on direct versus indirect insults. Functional SNPs in POPDC3 and FAAH genes may be driving the association with direct and indirect ALI/ARDS, respectively.

Reversal of dependent lung collapse predicts response to lung recruitment in children with early acute lung injury

OBJECTIVE

To describe the resolution of regional atelectasis and the development of regional lung overdistension during a lung-recruitment protocol in children with acute lung injury.

DESIGN

Prospective interventional trial.

SETTING

Pediatric intensive care unit.

PATIENTS

Ten children with early (<72 hrs) acute lung injury.

INTERVENTIONS

Sustained inflation maneuver (positive airway pressure of 40 cm H2O for 40 secs), followed by a stepwise recruitment maneuver (escalating plateau pressures by 5 cm H2O every 15 mins) until physiologic lung recruitment, defined by PaO2 + PaCO2 ≥400 mm Hg, was achieved. Regional lung volumes and mechanics were measured using electrical impedance tomography.

MEASUREMENTS AND MAIN RESULTS

Patients that responded to the stepwise lung-recruitment maneuver had atelectasis in 54% of the dependent lung regions, while nonresponders had atelectasis in 10% of the dependent lung regions (p = .032). In the pressure step preceding physiologic lung recruitment, a significant reversal of atelectasis occurred in 17% of the dependent lung regions (p = .016). Stepwise recruitment overdistended 8% of the dependent lung regions in responders, but 58% of the same regions in nonresponders (p < .001). Lung compliance in dependent lung regions increased in responders, while compliance in nonresponders did not improve. In contrast to the stepwise recruitment maneuver, the sustained inflation did not produce significant changes in atelectasis or oxygenation: atelectasis was only reversed in 12% of the lung (p = .122), and there was only a modest improvement in oxygenation (27 ± 14 mm Hg, p = .088).

CONCLUSIONS

Reversal of atelectasis in the most dependent lung region preceded improvements in gas exchange during a stepwise lung-recruitment strategy. Lung recruitment of dependent lung areas was accompanied by considerable overdistension of nondependent lung regions. Larger amounts of atelectasis in dependent lung areas were associated with a positive response to a stepwise lung-recruitment maneuver.

The Berlin definition of ARDS: an expanded rationale, justification, and supplementary material

PURPOSE

Our objective was to revise the definition of acute respiratory distress syndrome (ARDS) using a conceptual model incorporating reliability and validity, and a novel iterative approach with formal evaluation of the definition.

METHODS

The European Society of Intensive Care Medicine identified three chairs with broad expertise in ARDS who selected the participants and created the agenda. After 2 days of consensus discussions a draft definition was developed, which then underwent empiric evaluation followed by consensus revision.

RESULTS

The Berlin Definition of ARDS maintains a link to prior definitions with diagnostic criteria of timing, chest imaging, origin of edema, and hypoxemia. Patients may have ARDS if the onset is within 1 week of a known clinical insult or new/worsening respiratory symptoms. For the bilateral opacities on chest radiograph criterion, a reference set of chest radiographs has been developed to enhance inter-observer reliability. The pulmonary artery wedge pressure criterion for hydrostatic edema was removed, and illustrative vignettes were created to guide judgments about the primary cause of respiratory failure. If no risk factor for ARDS is apparent, however, objective evaluation (e.g., echocardiography) is required to help rule out hydrostatic edema. A minimum level of positive end-expiratory pressure and mutually exclusive PaO(2)/FiO(2) thresholds were chosen for the different levels of ARDS severity (mild, moderate, severe) to better categorize patients with different outcomes and potential responses to therapy.

CONCLUSIONS

This panel addressed some of the limitations of the prior ARDS definition by incorporating current data, physiologic concepts, and clinical trials results to develop the Berlin definition, which should facilitate case recognition and better match treatment options to severity in both research trials and clinical practice.

Goal-oriented respiratory management for critically ill patients with acute respiratory distress syndrome

This paper, based on relevant literature articles and the authors' clinical experience, presents a goal-oriented respiratory management for critically ill patients with acute respiratory distress syndrome (ARDS) that can help improve clinicians' ability to care for these patients. Early recognition of ARDS modified risk factors and avoidance of aggravating factors during hospital stay such as nonprotective mechanical ventilation, multiple blood products transfusions, positive fluid balance, ventilator-associated pneumonia, and gastric aspiration can help decrease its incidence. An early extensive clinical, laboratory, and imaging evaluation of “at risk patients” allows a correct diagnosis of ARDS, assessment of comorbidities, and calculation of prognostic indices, so that a careful treatment can be planned. Rapid administration of antibiotics and resuscitative measures in case of sepsis and septic shock associated with protective ventilatory strategies and early short-term paralysis associated with differential ventilatory techniques (recruitment maneuvers with adequate positive end-expiratory pressure titration, prone position, and new extracorporeal membrane oxygenation techniques) in severe ARDS can help improve its prognosis. Revaluation of ARDS patients on the third day of evolution (Sequential Organ Failure Assessment (SOFA), biomarkers and response to infection therapy) allows changes in the initial treatment plans and can help decrease ARDS mortality.

Optimal unified approach for rare-variant association testing with application to small-sample case-control whole-exome sequencing studies

We propose in this paper a unified approach for testing the association between rare variants and phenotypes in sequencing association studies. This approach maximizes power by adaptively using the data to optimally combine the burden test and the nonburden sequence kernel association test (SKAT). Burden tests are more powerful when most variants in a region are causal and the effects are in the same direction, whereas SKAT is more powerful when a large fraction of the variants in a region are noncausal or the effects of causal variants are in different directions. The proposed unified test maintains the power in both scenarios. We show that the unified test corresponds to the optimal test in an extended family of SKAT tests, which we refer to as SKAT-O. The second goal of this paper is to develop a small-sample adjustment procedure for the proposed methods for the correction of conservative type I error rates of SKAT family tests when the trait of interest is dichotomous and the sample size is small. Both small-sample-adjusted SKAT and the optimal unified test (SKAT-O) are computationally efficient and can easily be applied to genome-wide sequencing association studies. We evaluate the finite sample performance of the proposed methods using extensive simulation studies and illustrate their application using the acute-lung-injury exome-sequencing data of the National Heart, Lung, and Blood Institute Exome Sequencing Project.

Regional pulmonary inflammation in an endotoxemic ovine acute lung injury model

The regional distribution of inflammation during acute lung injury (ALI) is not well known. In an ovine ALI model we studied regional alveolar inflammation, surfactant composition, and CT-derived regional specific volume change (sVol) and specific compliance (sC). 18 ventilated adult sheep received IV lipopolysaccharide (LPS) until severe ALI was achieved. Blood and bronchoalveolar lavage (BAL) samples from apical and basal lung regions were obtained at baseline and injury time points, for analysis of cytokines (IL-6, IL-1β), BAL protein and surfactant composition. Whole lung CT images were obtained in 4 additional sheep. BAL protein and IL-1β were significantly higher in injured apical vs. basal regions. No significant regional surfactant composition changes were observed. Baseline sVol and sC were lower in apex vs. base; ALI enhanced this cranio-caudal difference, reaching statistical significance only for sC. This study suggests that apical lung regions show greater inflammation than basal ones during IV LPS-induced ALI which may relate to differences in regional mechanical events.

Acute lung injury induced by Staphylococcal enterotoxin B: disruption of terminal vessels as a mechanism of induction of vascular leak

The current hypothesis of alveolar capillary membrane dysfunction fails to completely explain the severe and persistent leak of protein-rich fluid into the pulmonary interstitium, seen in the exudative phase of acute lung injury (ALI). The presence of intact red blood cells in the pulmonary interstitium may suggest mechanical failure of pulmonary arterioles and venules. These studies involved the pathological and ultrastructural evaluation of the pulmonary vasculature in Staphylococcal enterotoxin B (SEB)-induced ALI. Administration of SEB resulted in a significant increase in the protein concentration of bronchoalveolar lavage fluid and vascular leak in SEB-exposed mice compared to vehicle-treated mice. In vivo imaging of mice demonstrated the pulmonary edema and leakage in the lungs of SEB-administered mice. The histopathological studies showed intense clustering of inflammatory cells around the alveolar capillaries with subtle changes in architecture. Electron microscopy studies further confirmed the diffuse damage and disruption in the muscularis layer of the terminal vessels. Cell death in the endothelial cells of the terminal vessels was confirmed with TUNEL staining. In this study, we demonstrated that in addition to failure of the alveolar capillary membrane, disruption of the pulmonary arterioles and venules may explain the persistent and severe interstitial and alveolar edema.

A positive response to a recruitment maneuver with PEEP titration in patients with ARDS, regardless of transient oxygen desaturation during the maneuver

Recruitment maneuvers (RMs) can expand collapsed alveoli in ventilated patients. The optimal method for delivering RMs is unknown.

PURPOSE

To evaluate the safety and the respiratory and hemodynamic effects of a staircase recruitment maneuver (SRM) with decremental positive end expiratory pressure (PEEP) titration and the consequences of desaturation during the SRM in patients with early acute lung injury (ALI).

METHODS

In total, 20 consecutive patients with early ALI were enrolled and received an SRM. Patients were given 15 ± 3 cm H(2)O pressure-controlled ventilation. Positive end expiratory pressure was increased from baseline (range 10-18) to 20, 30, and 40 cm H(2)O every 2 minutes to achieve maximum alveolar pressure of 55 ± 3 cm H(2)O, then decreased at 3-minute intervals to 25, 22.5, 20, 17.5, and 15 cm H(2)O until a decrease of 1% to 2% oxygen saturation from maximum was detected. Positive end expiratory pressure was left at the level where the fall in oxygen saturation occurred. Standard respiratory and circulatory variables, arterial and central venous gases were measured before, during, and after the SRM.

RESULTS

There were significant improvements in shunt fraction (36.3% ± 10% to 26.4% ± 14%, P < .001), oxygen saturation (93.4% ± 2% to 96.8% ± 3%, P = .007), partial pressure of oxygen, arterial (PaO(2))/fraction of inspired oxygen ([FIO(2)]; 150 ± 42 to 227 ± 100, P = .004), lung compliance (33.9 ± 9.1 to 40.1 ± 11.4 mL/cm H(2)O, P < .01), and chest x-ray (CXR) after the SRM. Briefly, 80% of the patients responded and the response was maintained at 1 hour. In total, 8 patients desaturated 6.1% ± 2.8% in SaO(2) during the SRM but 5 of those improved SaO(2) relative to baseline by the end of the SRM.

CONCLUSIONS

In all, 80% of the patients with early ALI responded to the SRM with decremental PEEP titration. Desaturation during the SRM did not indicate a failed response 1 hour later.

Effects of early administration of a novel anticholinergic drug on acute respiratory distress syndrome induced by sepsis

Background

Acute respiratory distress syndrome (ARDS) is the inflammatory disorder of the lung most commonly caused by sepsis. It was hypothesized that treating the lung with penehyclidine hydrochloride (PHC), a new type of hyoscyamus drug, early in the development of sepsis could diminish the lung dysfunction.

Material/Methods

Sprague-Dawley rats were divided into 4 groups: 1) a control group; 2) a sham-operated group; 3) a cecal ligation and puncture (CLP) group; 4) a PHC-treated group. One hour after CLP surgery, rats were either untreated or treated with PHC via intraperitoneal injection. Lung wet/dry weight ratio, bronchoalveolar lavage fluid (BALF), serum tumor necrosis factor (TNF-α), interleukin 6 (IL-6), interleukin 10 (IL-10), total nitrite/nitrate (NOx), superoxide dismutase (SOD), malondialdehyde (MDA) in lung tissues, and pulmonary functions were examined 24 hour after surgery. Another 60 rats were randomly assigned to 4 equal groups to observe survival status 96 hours after surgery.

Results

Treatment of PHC markedly decreased TNF-α, IL-6, NOx, SOD, MDA content, protein concentration in BALF, and lung wet/dry weight ratio and enhanced SOD activity (p<0.05), which are indicative of PHC-induced suppression in the pathogenesis of ARDS caused by sepsis. In comparison to group CLP/saline, plasma IL-10 level markedly increased in group CLP/PHC. In PHC-treated groups, the administered PHC had a significant protective effect on the lung dysfunction induced by sepsis.

Conclusions

We conclude that administration of PHC at the time of a systemic insult can protect the lung from the damaging effects of sepsis.

The matri-cellular proteins 'cysteine-rich, angiogenic-inducer, 61' and 'connective tissue growth factor' are regulated in experimentally-induced sepsis with multiple organ dysfunction

Organ failure is a severe complication in sepsis for which the pathophysiology remains incompletely understood. Recently, the matri-cellular cysteine-rich, angiogenic induced, 61 (Cyr61/CCN1); connective tissue growth factor (Ctgf/CCN2); and nephroblastoma overexpressed gene (Nov/CCN3) (CCN)-protein family have been attributed organ-protective properties. Their expression is sensitive to mediators of sepsis pathophysiology but a potential role in sepsis remains elusive. To provide an initial assessment, 50 rats were subjected to 18 h of cecal-ligation and puncture or sham operation. Hepatic and pulmonary CCN1 mRNA displayed an average 7.4- and 3.3-fold induction, while its cardiac expression was unchanged. The changes coincided with excessive hepatic and pulmonary inflammatory gene activation and a restricted cardiac inflammation. Furthermore, hepatocytes displayed a dosage-dependent CCN1 mRNA response in vitro, supporting a cytokine-mediated CCN1 regulation in sepsis. CCN2 mRNA was 2.2-fold induced in the liver, while 2.0-fold and 1.4-fold repressed in the heart and lung. Meanwhile, it did not respond to TNF-α exposure in vitro, which indicates different means of regulation than for CCN1. Taken together, this study provides the first evidence for multi-organ regulation of CCN1 and CCN2 in early stages of sepsis, and implies the eruption of inflammatory mediators as a potential mechanism behind the observed CCN1 regulation.

Characterization of pediatric patients receiving prolonged mechanical ventilation

OBJECTIVE

To describe the characteristics and risk factors of pediatric patients who receive prolonged mechanical ventilation, defined as ventilatory support for >21 days.

DESIGN

Prospective cohort.

SETTING

Four medical-surgical pediatric intensive care units in four university-affiliated hospitals in Argentina.

PATIENTS

All consecutive patients from 1 month to 15 yrs old admitted to participating pediatric intensive care units from June 1, 2007, to August 31, 2007, who received mechanical ventilation (invasive or noninvasive) for >12 hrs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic and physiologic data on admission to the pediatric intensive care units, drugs and events during the study period, and outcomes were prospectively recorded. A total of 256 patients were included. Of these, 23 (9%) required mechanical ventilation for >21 days and were assigned to the prolonged mechanical ventilation group. Patients requiring prolonged mechanical ventilation had higher mortality (43% vs. 21%, p < .05) and longer pediatric intensive care unit stay: 35 days [28-64 days] vs. 10 days [6-14]). There was no difference between the groups in age and gender distribution, reasons for admission, incidence of immunodeficiencies, or Paediatric Index of Mortality 2 score. The only difference at admission was a higher rate of genetic diseases in prolonged mechanical ventilation patients (26% vs. 9%, p < .05). There was a higher incidence of septic shock (87% vs. 34%, p < .01), acute respiratory distress syndrome (43% vs. 20%, p < .01), and ventilator-associated pneumonia (35% vs. 8%, p < .01) and higher utilization of dopamine (78% vs. 42%, p < .01), norepinephrine (61% vs. 15%, p < .01), multiple antibiotics (83% vs. 20%, p < .01), and blood transfusions (52% vs. 14%, p < .01). The proportion of extubation failure was higher in the prolonged mechanical ventilation group with similar rates of unplanned extubations in both groups. Variables remaining significantly associated with prolonged mechanical ventilation after multivariate analysis were treatment with multiple antibiotics, septic shock, ventilator-associated pneumonia, and use of norepinephrine.

CONCLUSIONS

Patients with prolonged mechanical ventilation have more complications and require more pediatric intensive care unit resources. Mortality in these patients duplicates that from those requiring shorter support.

Novel interventional approaches for ALI/ARDS: cell-based gene therapy

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), continue to be a major cause of morbidity and mortality in critically ill patients. The present therapeutic strategies for ALI/ARDS including supportive care, pharmacological treatments, and ventilator support are still controversial. More scientists are focusing on therapies involving stem cells, which have self-renewing capabilities and differentiate into multiple cell lineages, and, genomics therapy which has the potential to upregulate expression of anti-inflammatory mediators. Recently, the combination of cell and gene therapy which has been demonstrated to provide additive benefit has opened up a new chapter in therapeutic strategy and provides a basis for the development of an innovative approach for the prevention and treatment of ALI/ARDS.

Respiratory complications in critical illness of small animals

The percentage of emergency patients with respiratory problems treated at veterinary emergency and critical care facilities is poorly defined. Regardless of whether an animal has a primary lung disease or develops a secondary lung disease during hospitalization, acute respiratory distress syndrome (ARDS) is a common sequela to the failing lung. ARDS is a frequent sequela to sepsis, systemic inflammatory response (SIRS), and disseminated intravascular coagulation and is frequently the pulmonary manifestation of multiple organ dysfunction syndrome (MODS). ARDS, acute lung injury, SIRS, sepsis, and MODS are serious syndromes with grave consequences. Understanding the pathophysiology and consequences of these syndromes is imperative to early recognition.

A randomised controlled trial of an open lung strategy with staircase recruitment, titrated PEEP and targeted low airway pressures in patients with acute respiratory distress syndrome

INTRODUCTION

Tidal volume and plateau pressure minimisation are the standard components of a protective lung ventilation strategy for patients with acute respiratory distress syndrome (ARDS). Open lung strategies, including higher positive end-expiratory pressure (PEEP) and recruitment manoeuvres to date have not proven efficacious. This study examines the effectiveness and safety of a novel open lung strategy, which includes permissive hypercapnia, staircase recruitment manoeuvres (SRM) and low airway pressure with PEEP titration.

METHOD

Twenty ARDS patients were randomised to treatment or ARDSnet control ventilation strategies. The treatment group received SRM with decremental PEEP titration and targeted plateau pressure < 30 cm H2O. Gas exchange and lung compliance were measured daily for 7 days and plasma cytokines in the first 24 hours and on days 1, 3, 5 and 7 (mean ± SE). Duration of ventilation, ICU stay and hospital stay (median and interquartile range) and hospital survival were determined.

RESULTS

There were significant overall differences between groups when considering plasma IL-8 and TNF-α. For plasma IL-8, the control group was 41% higher than the treatment group over the seven-day period (ratio 1.41 (1.11 to 1.79), P = 0.01), while for TNF-α the control group was 20% higher over the seven-day period (ratio 1.20 (1.01 to 1.42) P = 0.05). PaO2/FIO2 (204 ± 9 versus 165 ± 9 mmHg, P = 0.005) and static lung compliance (49.1 ± 2.9 versus 33.7 ± 2.7 mls/cm H2O, P < 0.001) were higher in the treatment group than the control group over seven days. There was no difference in duration of ventilation (180 (87 to 298) versus 341 (131 to 351) hrs, P = 0.13), duration of ICU stay (9.9 (5.6 to 14.8) versus 16.0 (8.1 to 19.3) days, P = 0.19) and duration of hospital stay (17.9 (13.7 to 34.5) versus 24.7 (20.5 to 39.8) days, P = 0.16) between the treatment and control groups.

CONCLUSIONS

This open lung strategy was associated with greater amelioration in some systemic cytokines, improved oxygenation and lung compliance over seven days. A larger trial powered to examine clinically-meaningful outcomes is warranted.

TRIAL REGISTRATION

ACTRN12607000465459.

A randomised controlled trial of an open lung strategy with staircase recruitment, titrated PEEP and targeted low airway pressures in patients with acute respiratory distress syndrome

INTRODUCTION

Tidal volume and plateau pressure minimisation are the standard components of a protective lung ventilation strategy for patients with acute respiratory distress syndrome (ARDS). Open lung strategies, including higher positive end-expiratory pressure (PEEP) and recruitment manoeuvres to date have not proven efficacious. This study examines the effectiveness and safety of a novel open lung strategy, which includes permissive hypercapnia, staircase recruitment manoeuvres (SRM) and low airway pressure with PEEP titration.

METHOD

Twenty ARDS patients were randomised to treatment or ARDSnet control ventilation strategies. The treatment group received SRM with decremental PEEP titration and targeted plateau pressure < 30 cm H2O. Gas exchange and lung compliance were measured daily for 7 days and plasma cytokines in the first 24 hours and on days 1, 3, 5 and 7 (mean ± SE). Duration of ventilation, ICU stay and hospital stay (median and interquartile range) and hospital survival were determined.

RESULTS

There were significant overall differences between groups when considering plasma IL-8 and TNF-α. For plasma IL-8, the control group was 41% higher than the treatment group over the seven-day period (ratio 1.41 (1.11 to 1.79), P = 0.01), while for TNF-α the control group was 20% higher over the seven-day period (ratio 1.20 (1.01 to 1.42) P = 0.05). PaO2/FIO2 (204 ± 9 versus 165 ± 9 mmHg, P = 0.005) and static lung compliance (49.1 ± 2.9 versus 33.7 ± 2.7 mls/cm H2O, P < 0.001) were higher in the treatment group than the control group over seven days. There was no difference in duration of ventilation (180 (87 to 298) versus 341 (131 to 351) hrs, P = 0.13), duration of ICU stay (9.9 (5.6 to 14.8) versus 16.0 (8.1 to 19.3) days, P = 0.19) and duration of hospital stay (17.9 (13.7 to 34.5) versus 24.7 (20.5 to 39.8) days, P = 0.16) between the treatment and control groups.

CONCLUSIONS

This open lung strategy was associated with greater amelioration in some systemic cytokines, improved oxygenation and lung compliance over seven days. A larger trial powered to examine clinically-meaningful outcomes is warranted.

TRIAL REGISTRATION

ACTRN12607000465459.

The physical basis of ventilator-induced lung injury

Although mechanical ventilation (MV) is a life-saving intervention for patients with acute respiratory distress syndrome (ARDS), it can aggravate or cause lung injury, known as ventilator-induced lung injury (VILI). The biophysical characteristics of heterogeneously injured ARDS lungs increase the parenchymal stress associated with breathing, which is further aggravated by MV. Cells, in particular those lining the capillaries, airways and alveoli, transform this strain into chemical signals (mechanotransduction). The interaction of reparative and injurious mechanotransductive pathways leads to VILI. Several attempts have been made to identify clinical surrogate measures of lung stress/strain (e.g., density changes in chest computed tomography, lower and upper inflection points of the pressure-volume curve, plateau pressure and inflammatory cytokine levels) that could be used to titrate MV. However, uncertainty about the topographical distribution of stress relative to that of the susceptibility of the cells and tissues to injury makes the existence of a single 'global' stress/strain injury threshold doubtful.

Microcirculatory abnormalities in patients with severe influenza A (H1N1) infection

Purpose

This study was designed to evaluate the degree of microcirculatory abnormalities in patients with severe influenza A (H1N1) infection.

Methods

We assessed the sublingual microcirculation in seven consecutive patients with acute lung injury related to influenza A (H1N1) infection. The evaluation was carried out using sidestream dark field (SDF) imaging within the first 96 hr after the patients were admitted to the intensive care unit. Thenar oxygen saturation (StO₂) was also measured with near-infrared spectroscopy (NIRS) during a vascular occlusion test. In addition, the Lung Injury Score (LIS) and the APACHE II and SOFA scores were recorded.

Results

All patients received invasive mechanical ventilation and at least one of the following adjuvant therapies: inhaled nitric oxide (n = 4), extracorporeal membrane oxygenation (n = 1), prone position (n = 4), recruitment maneuver (n = 3), and hydrocortisone 50 mg·hr⁻⁶ (n = 6). The median time from admission to microcirculatory assessment was 21 hr. Three patients had bacterial superinfection. The median LIS and PaO₂/F_iO₂ were 2.5 (2.25-3.25) and 178 (158-212), respectively. Three subjects were treated with norepinephrine. During a vascular occlusion test, the microcirculation was moderately to severely compromised with a NIRS ascending slope of 2.39%·sec⁻¹ (1.75-2.67%·sec⁻¹), 66% (60-86%) of perfused small vessels in the sublingual microcirculation, and a microvascular flow index of 1.9 (1.3-2.6). The degree of microcirculatory abnormalities detected by the NIRS and SDF imaging techniques was correlated with the severity of the disease, as reflected by the SOFA and APACHE II scores.

Conclusions

The microcirculation as assessed by SDF imaging and NIRS techniques was compromised in patients with acute respiratory distress syndrome (ARDS) and influenza A (H1N1) infection.

Methylene blue for the treatment of septic shock

Septic shock is a major cause of morbidity and mortality in the intensive care unit, and effective therapies are limited. Methylene blue is a selective inhibitor of guanylate cyclase, a second messenger involved in nitric oxide-mediated vasodilation. The use of methylene blue in the treatment of septic shock has been repeatedly evaluated over the past 20 years, but data remain scarce. To evaluate the safety and efficacy of methylene blue for the treatment of septic shock, we conducted a literature search of the EMBASE (1974-June 2009), MEDLINE (1966-June 2009), and International Pharmaceutical Abstracts (1970-June 2009) databases. All available studies published in English were reviewed. Observational studies with methylene blue have demonstrated beneficial effects on hemodynamic parameters and oxygen delivery, but use of methylene blue may be limited by adverse pulmonary effects. Methylene blue administration is associated with increases in mean arterial pressure while reducing catecholamine requirements in patients experiencing septic shock; however, its effects on morbidity and mortality remain unknown. Well-designed, prospective evaluations are needed to define the role of methylene blue as treatment of septic shock.

Role of nitric oxide in management of acute respiratory distress syndrome

The current mortality rate of patients suffering from acute respiratory distress syndrome (ARDS) is between 45% and 92%, with most dying within the first two weeks of the illness. In an effort to combat such an alarmingly high mortality rate, various treatment therapies such as low tidal volume ventilation strategies, corticosteroid therapy, and use of nitric oxide (NO) have been attempted in the management of patients with ARDS. Three cases which were admitted to the ICU and confirmed to have ARDS were unable to be weaned from ventilatory support, and nitric oxide therapy was initiated. It improved patients' oxygenation for short periods of time but did not affect the mortality. The patients could not be weaned from the ventilator and expired.

The physical basis of ventilator-induced lung injury

Although mechanical ventilation (MV) is a life-saving intervention for patients with acute respiratory distress syndrome (ARDS), it can aggravate or cause lung injury, known as ventilator-induced lung injury (VILI). The biophysical characteristics of heterogeneously injured ARDS lungs increase the parenchymal stress associated with breathing, which is further aggravated by MV. Cells, in particular those lining the capillaries, airways and alveoli, transform this strain into chemical signals (mechanotransduction). The interaction of reparative and injurious mechanotransductive pathways leads to VILI. Several attempts have been made to identify clinical surrogate measures of lung stress/strain (e.g., density changes in chest computed tomography, lower and upper inflection points of the pressure-volume curve, plateau pressure and inflammatory cytokine levels) that could be used to titrate MV. However, uncertainty about the topographical distribution of stress relative to that of the susceptibility of the cells and tissues to injury makes the existence of a single 'global' stress/strain injury threshold doubtful.

Differential regulation of inducible and endothelial nitric oxide synthase by kinin B1 and B2 receptors

Kinins are vasoactive peptides that play important roles in cardiovascular homeostasis, pain and inflammation. After release from their precursor kininogens, kinins or their C-terminal des-Arg metabolites activate two distinct G protein-coupled receptors (GPCR), called B2 (B2R) or B1 (B1R). The B2R is expressed constitutively with a wide tissue distribution. In contrast, the B1R is not expressed under normal conditions but is upregulated by tissue insult or inflammatory mediators. The B2R is considered to mediate many of the acute effects of kinins while the B1R is more responsible for chronic responses in inflammation. Both receptors can couple to Galphai and Galphaq families of G proteins to release mediators such as nitric oxide (NO), arachidonic acid, prostaglandins, leukotrienes and endothelium-derived hyperpolarizing factor and can induce the release of other inflammatory agents. The focus of this review is on the different transduction events that take place upon B2R and B1R activation in human endothelial cells that leads to generation of NO via activation of different NOS isoforms. Importantly, B2R-mediated eNOS activation leads to a transient ( approximately 5min) output of NO in control endothelial cells whereas in cytokine-treated endothelial cells, B1R activation leads to very high and prolonged ( approximately 90min) NO production that is mediated by a novel signal transduction pathway leading to post-translational activation of iNOS.

A critical appraisal of the quality of critical care pharmacotherapy clinical practice guidelines and their strength of recommendations

OBJECTIVE

Clinical practice guideline (CPG) quality assessment is important before applying their recommendations. Determining whether recommendation strength is consistent with supporting quality of evidence is also essential. We aimed to determine quality of critical care pharmacotherapy CPGs and to assess whether high quality evidence supports strong pharmacotherapy recommendations.

METHODS

MEDLINE (1966-February 2008), EMBASE (1980-February 2008), National Guideline Clearinghouse (February 2008) and personal files were searched to identify CPGs. Four appraisers evaluated each guideline using the appraisal of guidelines, research and evaluation (AGREE) instrument. AGREE assesses 23 items in six domains that include scope/purpose, stakeholder involvement, rigor of development, clarity, applicability and editorial independence. Standardized domain scores (0-100%) were determined to decide whether to recommend a guideline for use. One appraiser extracted strong pharmacotherapy recommendations and supporting evidence quality.

RESULTS

Twenty-four CPGs were included. Standardized domain scores were clarity [69% (95% confidence interval (CI) 62-76%)], scope/purpose [62% (95% CI 55-68%)], rigor of development [51% (95% CI 42-60%)], editorial independence [39% (95% CI 26-52%)], stakeholder involvement [32% (95% CI 26-37%)] and applicability [19% (95% CI 12-26%)]. The proportion of guidelines that could be strongly recommended, recommended with alterations and not recommended was 25, 37.5 and 37.5%, respectively. High quality evidence supported 36% of strong pharmacotherapy recommendations.

CONCLUSION

Variation in AGREE domain scores explain why one-third of critical care pharmacotherapy CPGs cannot be recommended. Only one-third of strong pharmacotherapy recommendations were supported by high quality evidence. We recommend appraisal of guideline quality and the caliber of supporting evidence prior to applying recommendations.

Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis

BACKGROUND

Prone position ventilation for acute hypoxemic respiratory failure (AHRF) improves oxygenation but not survival, except possibly when AHRF is severe.

OBJECTIVE

To determine effects of prone versus supine ventilation in AHRF and severe hypoxemia [partial pressure of arterial oxygen (PaO(2))/inspired fraction of oxygen (FiO(2)) <100 mmHg] compared with moderate hypoxemia (100 mmHg < or = PaO(2)/FiO(2) < or = 300 mmHg).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases (to November 2009) and conference proceedings.

METHODS

Two authors independently selected and extracted data from parallel-group randomized controlled trials comparing prone with supine ventilation in mechanically ventilated adults or children with AHRF. Trialists provided subgroup data. The primary outcome was hospital mortality in patients with AHRF and PaO(2)/FiO(2) <100 mmHg. Meta-analyses used study-level random-effects models.

RESULTS

Ten trials (N = 1,867 patients) met inclusion criteria; most patients had acute lung injury. Methodological quality was relatively high. Prone ventilation reduced mortality in patients with PaO(2)/FiO(2) <100 mmHg [risk ratio (RR) 0.84, 95% confidence interval (CI) 0.74-0.96; p = 0.01; seven trials, N = 555] but not in patients with PaO(2)/FiO(2) > or =100 mmHg (RR 1.07, 95% CI 0.93-1.22; p = 0.36; seven trials, N = 1,169). Risk ratios differed significantly between subgroups (interaction p = 0.012). Post hoc analysis demonstrated statistically significant improved mortality in the more hypoxemic subgroup and significant differences between subgroups using a range of PaO(2)/FiO(2) thresholds up to approximately 140 mmHg. Prone ventilation improved oxygenation by 27-39% over the first 3 days of therapy but increased the risks of pressure ulcers (RR 1.29, 95% CI 1.16-1.44), endotracheal tube obstruction (RR 1.58, 95% CI 1.24-2.01), and chest tube dislodgement (RR 3.14, 95% CI 1.02-9.69). There was no statistical between-trial heterogeneity for most clinical outcomes.

CONCLUSIONS

Prone ventilation reduces mortality in patients with severe hypoxemia. Given associated risks, this approach should not be routine in all patients with AHRF, but may be considered for severely hypoxemic patients.

Comparison of forehead Max-Fast pulse oximetry sensor with finger sensor at high positive end-expiratory pressure in adult patients with acute respiratory distress syndrome

In the critical care setting it may be difficult to determine an accurate reading of oxygen saturation from digital sensors as a result of poor peripheral perfusion. Limited evidence suggests that forehead sensors may be more accurate in these patients. We prospectively compared the accuracy of a forehead reflectance sensor (Max-Fast) with a conventional digital sensor in patients with acute respiratory distress syndrome during a high positive end-expiratory pressure (PEEP) recruitment manoeuvre (stepwise recruitment manoeuvre). Sixteen patients with early acute respiratory distress syndrome were enrolled to evaluate the blood oxygen saturation during a stepwise recruitment manoeuvre. PEEP was increased from baseline (range 10 to 18) to 40 cmH2O, then decreased to an optimal level determined by individual titration. Forehead and digital oxygen saturation and arterial blood gases were measured simultaneously before, during and after the stepwise recruitment manoeuvre at five time points. Seventy-three samples were included for analysis from 16 patients. The SaO2 values ranged from 73 to 99.6%. The forehead sensor provided measurements that deviated more from arterial measures than the finger sensor (mean absolute deviations 3.4%, 1.1% respectively, P=0.02). The greater variability in forehead measures taken at maximum PEEP was reflected in the unusually large precision estimates of 4.24% associated with these measures. No absolute differences from arterial measures taken at any other time points were significantly different. The finger sensor is as accurate as the forehead sensor in detecting changes in arterial oxygen saturation in adults with acute respiratory distress syndrome and it may be better at levels of high PEEP such as during recruitment manoeuvres.

Pathological findings and pulmonary dysfunction after acute respiratory distress syndrome for 5 years

We report the pathological findings of the lung after acute respiratory distress syndrome (ARDS), and pulmonary function tests during five years of follow-up. A 39-year-old woman, treated for acute myelogenous leukemia, developed ARDS. She recovered from ARDS but suffered from pulmonary aspergillosis. Her aspergilloma was removed surgically. Her lung function tests and diffusing capacity of the lung for carbon monoxide (DL(CO)) improved but diffusion impairment remained five years after recovery. Pathological examination of the resected material showed sclerosis in lobular septa and scattered fibrosis in alveolar ducts except for the aspergillosis. These fibrotic changes may be causally associated with her loss of DL(CO).

Role of cholesterol in the biophysical dysfunction of surfactant in ventilator-induced lung injury

Mechanical ventilation may lead to an impairment of the endogenous surfactant system, which is one of the mechanisms by which this intervention contributes to the progression of acute lung injury. The most extensively studied mechanism of surfactant dysfunction is serum protein inhibition. However, recent studies indicate that hydrophobic components of surfactant may also contribute. It was hypothesized that elevated levels of cholesterol significantly contribute to surfactant dysfunction in ventilation-induced lung injury. Sprague-Dawley rats ( n = 30) were randomized to either high-tidal volume or low-tidal volume ventilation and monitored for 2 h. Subsequently, the lungs were lavaged, surfactant was isolated, and the biophysical properties of this isolated surfactant were analyzed on a captive bubble surfactometer with and without the removal of cholesterol using methyl-β-cyclodextrin. The results showed lower oxygenation values in the high-tidal volume group during the last 30 min of ventilation compared with the low-tidal volume group. Surfactant obtained from the high-tidal volume animals had a significant impairment in function compared with material from the low-tidal volume group. Removal of cholesterol from the high-tidal volume group improved the ability of the surfactant to reduce the surface tension to low values. Subsequent reconstitution of high-cholesterol values led to an impairment in surface activity. It is concluded that increased levels of cholesterol associated with endogenous surfactant represent a major contributor to the inhibition of surfactant function in ventilation-induced lung injury.

A pumpless lung assist device reduces mechanical ventilation-induced lung injury in juvenile piglets

Respiratory failure is a major contributor to mortality and morbidity in newborn infants. The lung assist device (LAD) is a novel gas exchange device that supplements mechanical ventilation. The objective is to test the effect of the LAD on pulmonary histopathology in juvenile piglets with acute lung injury caused by saline lung lavage (SLL) followed by intermittent mandatory ventilation (IMV). Three- to 4-wk-old piglets were randomized to no intervention (control group), SLL alone (SLL group), SLL + IMV (IMV group), or SLL + IMV + LAD (LAD group) (n = 6 per group). The carotid artery and jugular vein were cannulated and an arteriovenous circuit completed, and the LAD was inserted into this circuit. Gas exchange via the LAD was initiated by passage of 100% oxygen over the blood-carrying hollow fibers of the LAD. Hemodynamic variables were recorded. Mechanical ventilation was systematically weaned. Lung histology was scored by two observers masked to treatment group. There were no differences in hemodynamic variables between the study groups. There was a significant increase in the total lung injury score in the IMV group compared with the LAD group. The novel pumpless low-resistance LAD has shown feasibility and potential to decrease ventilator-induced lung injury in a juvenile animal model.

Milk fat globule epidermal growth factor 8 attenuates acute lung injury in mice after intestinal ischemia and reperfusion

RATIONALE

Milk fat globule epidermal growth factor 8 (MFG-E8) is a potent opsonin for the clearance of apoptotic cells and is produced by mononuclear cells of immune competent organs including the spleen and lungs. It attenuates chronic and acute inflammation such as autoimmune glomerulonephritis and bacterial sepsis by enhancing apoptotic cell clearance. Ischemia-reperfusion (I/R) injury of the gut results in severe inflammation, apoptosis, and remote organ damage, including acute lung injury (ALI).

OBJECTIVES

To determine whether MFG-E8 attenuates intestinal and pulmonary inflammation after gut I/R.

METHODS

Wild-type (WT) and MFG-E8(-/-) mice underwent superior mesenteric artery occlusion for 90 minutes, followed by reperfusion for 4 hours. A group of WT mice was treated with 0.4 microg/20 g recombinant murine MFG-E8 (rmMFG-E8) at the beginning of reperfusion. Four hours after reperfusion, MFG-E8, cytokines, myeloperoxidase activity, apoptosis, and histopathology were assessed. A 24-hour survival study was conducted in rmMFG-E8- and vehicle-treated WT mice.

MEASUREMENTS AND MAIN RESULTS

Mesenteric I/R caused severe widespread injury and inflammation of the small intestines and remote organs, including the lungs. MFG-E8 levels decreased in the spleen and lungs by 50 to 60%, suggesting impaired apoptotic cell clearance. Treatment with rmMFG-E8 significantly suppressed inflammation (TNF-alpha, IL-6, IL-1beta, and myeloperoxidase) and injury of the lungs, liver, and kidneys. MFG-E8-deficient mice suffered from greatly increased inflammation and potentiated ALI, whereas treatment with rmMFG-E8 significantly improved the survival in WT mice.

CONCLUSIONS

MFG-E8 attenuates inflammation and ALI after gut I/R and may represent a novel therapeutic agent.

Differential expression of platelet-activating factor acetylhydrolase in lung macrophages

Platelet-activating factor (PAF) acetylhydrolase plays a crucial role inactivating the potent inflammatory mediator, PAF. PAF is implicated in the initiation and propagation of acute lung injury. Although PAF acetylhydrolase is a constitutively active plasma protein, increased PAF production during inflammatory events may necessitate an increase in PAF acetylhydrolase activity in the local environment. A series of experiments were conducted to determine whether the systemic administration of LPS to Sprague-Dawley rats resulted in enhanced expression of PAF acetylhydrolase in lung tissue. Ribonuclease protection assays revealed a dramatic increase in PAF acetylhydrolase mRNA, which peaked at 24 h following in vivo LPS administration. The increase in PAF acetylhydrolase mRNA was dose dependent and was detected when as little as 10 microg/kg of LPS was administered. Western blot analyses of lung tissue homogenates confirmed an increased production of PAF acetylhydrolase protein in response to LPS. In addition, Western blot analyses revealed the rat PAF acetylhydrolase protein exhibited heterogeneous molecular weights with predominant species migrating at 63 and 67 kDa. Some of the molecular weight heterogeneity likely resulted from extensive glycosylation of the secreted protein. Immunohistochemical analyses of lung tissue sections and colocalization experiments revealed a heterogenous population of cells that express the plasma-type PAF acetylhydrolase. Lung interstitial macrophages were PAF acetylhydrolase positive, but surprisingly, alveolar macrophages did not increase expression of PAF acetylhydrolase in response to systemic LPS administration. In addition, rat granulocytes consisting primarily of neutrophils were strongly positive for PAF acetylhydrolase in the LPS-exposed lung tissue. The absence of immunoreactive PAF acetylhydrolase in alveolar macrophages obtained from bronchial alveolar lavage confirmed that systemic LPS administration resulted in enhanced PAF acetylhydrolase expression only in a subset of lung macrophages.

CD4+CD25+Foxp3+ Tregs resolve experimental lung injury in mice and are present in humans with acute lung injury

Acute lung injury (ALI) is characterized by rapid alveolar injury, inflammation, cytokine induction, and neutrophil accumulation. Although early events in the pathogenesis of ALI have been defined, the mechanisms underlying resolution are unknown. As a model of ALI, we administered intratracheal (i.t.) LPS to mice and observed peak lung injury 4 days after the challenge, with resolution by day 10. Numbers of alveolar lymphocytes increased as injury resolved. To examine the role of lymphocytes in this response, lymphocyte-deficient Rag-1-/- and C57BL/6 WT mice were exposed to i.t. LPS. The extent of injury was similar between the groups of mice through day 4, but recovery was markedly impaired in the Rag-1-/- mice. Adoptive transfer studies revealed that infusion of CD4+CD25+Foxp3+ Tregs as late as 24 hours after i.t. LPS normalized resolution in Rag-1-/- mice. Similarly, Treg depletion in WT mice delayed recovery. Treg transfer into i.t. LPS-exposed Rag-1-/- mice also corrected the elevated levels of alveolar proinflammatory cytokines and increased the diminished levels of alveolar TGF-beta and neutrophil apoptosis. Mechanistically, Treg-mediated resolution of lung injury was abrogated by TGF-beta inhibition. Moreover, BAL of patients with ALI revealed dynamic changes in CD3+CD4+CD25hiCD127loFoxp3+ cells. These results indicate that Tregs modify innate immune responses during resolution of lung injury and suggest potential targets for treating ALI, for which there are no specific therapies currently available.

Late-onset ventilator-associated pneumonia in nontrauma intensive care unit patients

BACKGROUND

Most studies designed to determine the factors associated with the acquisition of late-onset ventilator-associated pneumonia (VAP) were performed in critically ill trauma patients. The impact of enteral nutrition (EN) on the risk of acquiring VAP has been discussed. In this study, we assessed factors associated with late-onset VAP in nontrauma patients and determined whether nutrition provided early was associated with development of late-onset VAP in this population.

METHODS

We performed a prospective observational cohort study in a 21-bed polyvalent intensive care unit in a university hospital.

RESULTS

Three hundred sixty-one intubated adult patients with a duration of mechanical ventilation (MV) of 6 days or more were admitted over a 28-mo period. Late-onset VAP was confirmed in 76 patients (21%) by the presence of at least one microorganism at a concentration >or=10(4) colony-forming units/mL on the bronchoalveolar lavage. Gram-negative bacilli represented 75% and Staphylococcus aureus 21% of recovered organisms. Factors independently associated with late-onset VAP by multivariate analysis included a high simplified acute physiology score II score (odds ratio: 1.021; 95% confidence interval [CI]: 1.005-1.038; P = 0.01), development of acute respiratory distress syndrome during the first 5 days of MV (odds ratio: 1.98; 95% CI: 1.05-3.67; P = 0.04), and size of the endotracheal tube >or=7.5 (odds ratio: 2.06; 95% CI: 1.88-3.90; P = 0.03). EN started within 48 h of MV onset was not associated with a higher risk for late-onset VAP.

CONCLUSION

In our nontrauma patient population, early EN was not associated with development of late-onset VAP. In this population, severity of the disease during the first 5 days of MV seemed to be associated with late-onset VAP. In addition, our results suggest that the risk of late-onset VAP is higher in patients with a tube size >or=7.5 than in patients with a tube size <7.5.