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

Salicylate intoxication: a clinical review

Salicylates are widely used and are easily available as over-the-counter medications; thus, they can be readily abused. Although acute toxicity can be readily diagnosed if an ingestion history is provided, both acute and chronic salicylate toxicity often goes unrecognized, with high mortality when the patient is not treated properly. Salicylates should be considered in the differential diagnosis of an adult patient with acid-base abnormalities of uncertain cause, especially when there are concurrent neurologic symptoms. Patients with salicylate toxicity are treated with alkaline diuresis and sometimes dialysis. The prognosis depends on prompt recognition and treatment. Delayed diagnosis results in increased morbidity and mortality, particularly in the elderly.

Lung recruitment--a guide for clinicians

Recruitment manoeuvres play an important role in minimising ventilator associated lung injury (VALI) particularly when lung protective ventilation strategies are employed and as such clinicians should consider their application. This paper provides evidence-based recommendations for clinical practice with regard to alveolar recruitment. It includes recommendations for timing of recruitment, strategies of recruitment and methods of measuring the efficacy of recruitment manoeuvres and contributes to knowledge about the risks associated with recruitment manoeuvres. There are a range of methods for recruiting alveoli, most notably by manipulating positive end expiratory pressure (PEEP) and peak inspiratory pressure (PIP) with consensus as to the most effective not yet determined. A number of studies have demonstrated that improvement in oxygenation is rarely sustained following a recruitment manoeuvre and it is questionable whether improved oxygenation should be the clinician's goal. Transient haemodynamic compromise has been noted in a number of studies with a few studies reporting persistent, harmful sequelae to recruitment manoeuvres. No studies have been located that assess the impact of recruitment manoeuvres on length of ventilation, length of stay, morbidity or mortality. Recruitment manoeuvres restore end expiratory lung volume by overcoming threshold opening pressures and are most effective when applied after circuit disconnection and airway suction. Whether this ultimately improves outcomes in adult or paediatric populations is unknown.

A Scandinavian survey of drug administration through inhalation, suctioning and recruitment maneuvers in mechanically ventilated patients

BACKGROUND

The aim was to describe current practices for drug administration through inhalation, endotracheal suctioning and lung recruitment maneuvers in mechanically ventilated patients in Scandinavian intensive care units (ICUs).

METHODS

We invited 161 ICUs to participate in a web-based survey regarding (1) their routine standards and (2) current treatment of ventilated patients during the past 24 h. In order to characterize the patients, the lowest PaO(2) with the corresponding highest FiO(2), and the highest PaO(2) with the corresponding lowest FiO(2) during the 24-h study period were recorded.

RESULTS

Eighty-seven ICUs answered and reported 186 patients. Positive end-expiratory pressure (PEEP) levels (cmH(2)O) were 5-9 in 65% and >10 in 31% of the patients. Forty percent of the patients had heated humidification and 50% received inhalation of drugs. Endotracheal suctioning was performed >7 times during the study period in 40% of the patients, of which 23% had closed suction systems. Twenty percent of the patients underwent recruitment maneuvers. The most common recruitment maneuver was to increase PEEP and gradually increase the inspiratory pressure. Twenty-six percent of the calculated PaO(2)/FiO(2) ratios varied >13 kPa for the same patient.

CONCLUSION

Frequent use of drug administration through inhalation and endotracheal suctioning predispose to derecruitment of the lungs, possibly resulting in the large variations in PaO(2)/FiO(2) ratios observed during the 24-h study period. Recruitment maneuvers were performed only in one-fifth of the patients during the day of the survey.

Characterization, lung targeting profile and therapeutic efficiency of dipyridamole liposomes

The acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury (ALI). Its pathogenesis is closely linked with reactive oxygen species (ROS). Antioxidation has been considered as an efficient treatment. Besides, liposomes are widely investigated as potential drug carriers due to their ability to protect and carry drug molecules to the target organ such as the lung. The present study was undertaken to investigate whether dipyridamole (DIP), delivered as a liposomal preparation, can ameliorate the lipopolysaccharides (LPS)-induced ALI due to the changes of its biodistribution. First, the liposomes entrapping DIP were prepared by film hydration for treating ARDS. Subsequently, the characterizations including entrapment efficiency, size, span and micrograph of DIP liposomes were measured. The concentration change of DIP in tissues and plasma of mice after intravenous administration of DIP injection and DIP liposomes was determined by RP-HPLC and calculated to lung targeting parameters. To prove the therapeutic efficiency, the effects of DIP liposomes on LPS-induced ALI were studied compared with DIP injection. The results showed DIP liposomes have the relative high entrapment efficiency and satisfying particle size. Compared with DIP injection, the liposomes increased the accumulation of DIP in the lung on a vast scale. Furthermore, DIP liposomes alleviated the ALI induced by LPS significantly. All of the results suggested that DIP liposomes have the potential efficacy in treating ALI/ARDS due to their obvious lung targeting.

Inter-observer variability in chest radiograph reading for diagnosing acute lung injury in children

Acute lung injury (ALI), including its most serious form called acute respiratory distress syndrome (ARDS), is a devastating disease that can occur at any age. ALI/ARDS accounts for only 5-8% of admissions to pediatric intensive care units (PICUs) but is fatal in 30-60% of cases. International multicenter prospective studies are needed to better understand pediatric ALI/ARDS. However, a reproducible definition of ALI/ARDS is crucial to ensure that study populations are homogeneous. We designed a retrospective review to test the inter-observer variability of chest radiograph interpretation for presence of the American-European Consensus Conference (AECC) radiographic criterion for ALI/ARDS. The medical files of 24 children ventilated for ALI/ARDS in our PICU between January 1993 and December 2002 were reviewed. Five pediatric radiologists and five pediatric intensivists interpreted one frontal chest radiograph (FCR) per patient taken on the day of ALI/ARDS diagnosis. Each reader indicated whether the radiograph showed the AECC radiographic criterion for ALI/ARDS. Data analysis involved comparing each reader to all the others based on the raw agreement and Kappa coefficient (kappa). Features in the 24 patients were consistent with earlier studies. Global inter-observer agreement beyond chance was fair (kappa = 0.29 +/- 0.02) among the five radiologists (kappa = 0.26 +/- 0.05) and among the five intensivists (kappa = 0.29 +/- 0.05). Thus, considerable inter-observer variability occurred in assessing the radiographic criterion for ALI/ARDS, as previously shown in adults. Given the low incidence of ALI/ARDS in children, this variability may have a large impact in studies of pediatric ALI/ARDS.

[Management of the sedated patient]

A sedation strategy aimed at minimizing alteration of consciousness once comfort, analgesia and adaptation to the ventilator have been ensured is feasible in critically-ill patients requiring mechanical ventilation, even if, in patients with severe ARDS or ICH, the high dosages of sedatives and analgesics transiently required to provide perfect adaptation to the ventilator often preclude preservation of consciousness. The main components of a sedation algorithm include a clear objective of sedation-analgesia, regular assessments of patient status using validated clinical tools and a precise yet simple dosage adaptation schedule. Development and implementation of a sedation algorithm requires a multidisciplinary approach and an important input from both physicians and nurses. However, several methodologically-correct interventional studies have shown that using an algorithm to administrate sedatives and analgesics results in a significant reduction of MV duration, reaching 50% in some studies. This might translate into a real benefit for the patient point of view provided that preserving patient's comfort remains a constant concern for the caregivers. There is no reliable evidence to date to use propofol rather than midazolam as a sedative agent. Indeed, the way the sedative drug is used, as part of a sedation algorithm, is very likely more important than the selection of the drug itself. Analgesia-based sedation, promoting the use of morphinics alone before the adjunction of hypnotics, represents a new alternative to the traditional combined administration of hypnotics and morphinics. However data on the impact of analgesia-based sedation on patients' outcomes remain sparse to date.

The clinical efficacy of GOCA scoring system in patients with acute respiratory distress syndrome

To explore the following hypotheses: 1) Gas exchange, Organ failure, Cause, Associated disease (GOCA) score, which reflects both general health and the severity of lung injury, would be a better mortality predictor of acute respiratory distress syndrome (ARDS) than acute physiology and chronic health evaluation (APACHE II) or simplified acute physiology score (SAPS II), which are not specific to lung injury, and lung injury score (LIS) that focuses on the lung injury; 2) the performance of APACHE II and SAPS II will be improved when reinforced by LIS, we retrospectively analyzed ARDS patients (N=158) admitted to a medical intensive care unit for five years. The overall mortality of the ARDS patients was 53.2%. Calibrations for all models were good. The area under the curve of (AUC) of LIS (0.622) was significantly less than those of APACHE II (0.743) and SAPS II (0.753). The AUC of GOCA (0.703) was not better than those of APACHE II and SAPS II. The AUCs of APACHE II and SAPS II tended to further increase when reinforced by LIS. In conclusion, GOCA was not superior to APACHE II or SAPS II. The performance of the APACHE II or SAPS II tended to improve when combining a general scoring system with a scoring system that focused on the severity of lung injury.

[Hemodynamic variability caused by pressure-volume plotting and alveolar recruitment maneuvers in patients with adult respiratory distress syndrome]

OBJECTIVES

The plotting of pressure-volume curves and the performance of alveolar recruitment maneuvers are common practices in the care of patients with adult respiratory distress syndrome (ARDS), even though potentially harmful hemodynamic effects are associated with sustaining a high intrathoracic pressure. Our aim was to analyze hemodynamic and ventilatory changes related to these 2 maneuvers and to assess the short-term effectiveness of recruitment.

PATIENTS AND METHODS

The patients had ARDS and were being monitored with a catheter connected to a PiCCO system. All measurements were taken in sinus rhythm and with adequate vascular filling. Values recorded during plotting of the quasistatic pressure-volume curve and the recruitment maneuver (sustained airway pressure of 40 cm H2O) were the cardiac index, mean arterial pressure, heart rate, systolic volume index, and oxygen saturation (SpO2). Blood gas measurements were recorded before the maneuvers and 15 minutes afterwards.

RESULTS

All parameters decreased significantly in the 14 patients studied. The mean (SD) maximum decreases, from which all patients recovered within 2 minutes, were as follows: cardiac index, 26% (16%); mean arterial pressure, 6% (6%); heart rate, 4% (5%), systolic volume index, 21% (15%); and SpO2, 3% (3%). Significant increases in PaO2 (7% [6%]) and the ratio of PaO2 to the fraction of inspired oxygen were recorded after the recruitment maneuver (P=.016 and P=.014, respectively), but the changes were not clinically significant.

CONCLUSIONS

The hemodynamic disturbances associated with the alveolar recruitment maneuver based on sustaining a high end-expiratory pressure and the minor improvement in oxygenation achieved as a result suggest that the routine use of that maneuver in ARDS patients is of questionable value.

[Refractory infectious ARDS: place of extracorporeal membrane oxygenation]

Acute respiratory distress syndrome (ARDS) is a frequent cause of admission in intensive care unit. The treatment is well codified. Unfortunately some patients die because of hypoxemia despite a well-conducted medical treatment. Extracorporeal oxygenation could be the ultimate treatment for these refractory hypoxemia patients. We report two cases of patients suffering from severe ARDS who beneficiated from extracorporeal oxygenation, pointing out the interest of this technique during severe ARDS as well as the accessibility and the feasibility of the technique even apart from a specialized center.

Bronchoscopic suctioning may cause lung collapse: a lung model and clinical evaluation

OBJECTIVE

To assess lung volume changes during and after bronchoscopic suctioning during volume or pressure-controlled ventilation (VCV or PCV).

DESIGN

Bench test and patient study.

PARTICIPANTS

Ventilator-treated acute lung injury (ALI) patients.

SETTING

University research laboratory and general adult intensive care unit of a university hospital.

INTERVENTIONS

Bronchoscopic suctioning with a 12 or 16 Fr bronchoscope during VCV or PCV.

MEASUREMENTS AND RESULTS

Suction flow at vacuum levels of -20 to -80 kPa was measured with a Timeter(trade mark) instrument. In a water-filled lung model, airway pressure, functional residual capacity (FRC) and tidal volume were measured during bronchoscopic suctioning. In 13 ICU patients, a 16 Fr bronchoscope was inserted into the left or the right main bronchus during VCV or PCV and suctioning was performed. Ventilation was monitored with electric impedance tomography (EIT) and FRC with a modified N(2) washout/in technique. Airway pressure was measured via a pressure line in the endotracheal tube. Suction flow through the 16 Fr bronchoscope was 5 l/min at a vacuum level of -20 kPa and 17 l/min at -80 kPa. Derecruitment was pronounced during suctioning and FRC decreased with -479+/-472 ml, P<0.001.

CONCLUSIONS

Suction flow through the bronchoscope at the vacuum levels commonly used is well above minute ventilation in most ALI patients. The ventilator was unable to deliver enough volume in either VCV or PCV to maintain FRC and tracheal pressure decreased below atmospheric pressure.

Dynamic surface activity of a fully synthetic phospholipase-resistant lipid/peptide lung surfactant

Background

This study examines the surface activity and resistance to phospholipase degradation of a fully-synthetic lung surfactant containing a novel diether phosphonolipid (DEPN-8) plus a 34 amino acid peptide (Mini-B) related to native surfactant protein (SP)-B. Activity studies used adsorption, pulsating bubble, and captive bubble methods to assess a range of surface behaviors, supplemented by molecular studies using Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD), and plasmon resonance. Calf lung surfactant extract (CLSE) was used as a positive control.

Results

DEPN-8+1.5% (by wt.) Mini-B was fully resistant to degradation by phospholipase A₂ (PLA₂) in vitro, while CLSE was severely degraded by this enzyme. Mini-B interacted with DEPN-8 at the molecular level based on FTIR spectroscopy, and had significant plasmon resonance binding affinity for DEPN-8. DEPN-8+1.5% Mini-B had greatly increased adsorption compared to DEPN-8 alone, but did not fully equal the very high adsorption of CLSE. In pulsating bubble studies at a low phospholipid concentration of 0.5 mg/ml, DEPN-8+1.5% Mini-B and CLSE both reached minimum surface tensions <1 mN/m after 10 min of cycling. DEPN-8 (2.5 mg/ml)+1.5% Mini-B and CLSE (2.5 mg/ml) also reached minimum surface tensions <1 mN/m at 10 min of pulsation in the presence of serum albumin (3 mg/ml) on the pulsating bubble. In captive bubble studies, DEPN-8+1.5% Mini-B and CLSE both generated minimum surface tensions <1 mN/m on 10 successive cycles of compression/expansion at quasi-static and dynamic rates.

Conclusions

These results show that DEPN-8 and 1.5% Mini-B form an interactive binary molecular mixture with very high surface activity and the ability to resist degradation by phospholipases in inflammatory lung injury. These characteristics are promising for the development of related fully-synthetic lipid/peptide exogenous surfactants for treating diseases of surfactant deficiency or dysfunction.

Breath condensate nitrite correlates with hyperinflation in chronic obstructive pulmonary disease

Estimating the degree of pulmonary hyperinflation in chronic obstructive pulmonary disease (COPD) is not always straight forward. Standard pulmonary function tests provide only a crude estimate of this important aspect of COPD. In addition, good patient cooperation cannot always be achieved and therefore adds to the uncertainties with regard to the extent of hyperinflation of the lung. The aim of this investigation was to characterize exhaled breath condensate nitrite in volunteers, healthy smokers, and stable COPD (GOLD-stages 0-4) and to compare this parameter with inflammatory markers in exhaled breath condensate and with lung function in order to test the hypothesis that elevated exhaled breath condensate nitrite reflects hyperinflation in COPD. We found a logarithmic correlation of exhaled breath condensate nitrite to residual volume (r=0.75, p<0.0001), total lung capacity (r=0.51, p<0.0001), and thoracic gas volume (r=0.71, p<0.0001) but no correlation of exhaled breath condensate nitrite concentrations with levels of inflammatory cytokines in exhaled breath condensate (interleukin (IL)-8, IL-1beta, IL-6, IL-10, IL-12, and tumor necrosis factor-alpha). Analysis of COPD subgroups revealed a logarithmic correlation of EBC nitrite to residual volume, total lung capacity, and intrathoracic gas volume exclusively for patients characterized by GOLD classes 2, and higher. Our results confirm a relation of exhaled breath condensate nitrite levels and hyperinflation measured by conventional pulmonary function tests. Investigations using isolated lung models and cells stretched in culture also provide insight into this relation. Exhaled breath condensate nitrite may be a biochemical indicator of pulmonary overdistension.

Lung protective ventilation strategy for the acute respiratory distress syndrome

BACKGROUND

Patients with acute respiratory distress syndrome and acute lung injury require mechanical ventilatory support. Acute respiratory distress syndrome and acute lung injury are further complicated by ventilator-induced lung injury. Lung-protective ventilation strategies may lead to improved survival.

OBJECTIVES

To assess the effects of ventilation with lower tidal volume on morbidity and mortality in patients aged 16 years or older affected by acute respiratory distress syndrome and acute lung injury. A secondary objective was to determine whether the comparison between low and conventional tidal volume was different if a plateau airway pressure of greater than 30 to 35 cm H20 was used.

SEARCH STRATEGY

In our original review, we searched databases from inception until 2003. In this updated review, we searched The Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library 2006, Issue 3). We updated our search of MEDLINE, EMBASE, CINAHL and the Web of Science from 2003 to 2006. We also updated our search of intensive care journals and conference proceedings; databases of ongoing research, reference lists and 'grey literature' from 2003 to 2006.

SELECTION CRITERIA

We included randomized controlled trials comparing ventilation using either lower tidal volume (Vt) or low airway driving pressure (plateau pressure 30 cm H2O or less), resulting in tidal volume of 7 ml/kg or less versus ventilation that uses Vt in the range of 10 to 15 ml/kg, in adults (16 years old or older).

DATA COLLECTION AND ANALYSIS

We independently assessed trial quality and extracted data. Wherever appropriate, results were pooled. We applied fixed- and random-effects models.

MAIN RESULTS

We found one new study in this update for a total of six trials, involving 1297 patients, which were eligible for inclusion. Mortality at day 28 was significantly reduced by lung-protective ventilation: relative risk (RR) 0.74 (95% confidence interval (CI) 0.61 to 0.88); hospital mortality was reduced: RR 0.80 (95% CI 0.69 to 0.92); overall mortality was not significantly different if a plateau pressure less than or equal to 31 cm H2O in control group was used: RR 1.13 (95% CI 0.88 to 1.45). There was insufficient evidence about morbidity and long term outcomes.

AUTHORS' CONCLUSIONS

Clinical heterogeneity, such as different lengths of follow up and higher plateau pressure in control arms in two trials, make the interpretation of the combined results difficult. Mortality is significantly reduced at day 28 and at the end of hospital stay. The effects on long-term mortality are unknown, although the possibility of a clinically relevant benefit cannot be excluded.

Early institution of extracorporeal membrane oxygenation for primary graft dysfunction after lung transplantation improves outcome

BACKGROUND

Primary graft dysfunction (PGD) after lung transplantation (LTx) carries a significant mortality and clinical management is controversial. Extracorporeal membrane oxygenation (ECMO) has been used infrequently for recovery from acute lung injury (ALI) in this setting. We reviewed our experience with ECMO after primary LTx.

METHODS

The present study is a retrospective analysis of all LTx patients between 1991 and 2004. Twenty-two patients sustained severe PGD with subsequent placement on ECMO. We analyzed indications and 30-day, 1-year and 3-year mortality. Complications and incidence of multiple-organ failure (MOF) were determined. Critical appraisal of the evidence available to date was performed.

RESULTS

A total of 297 LTxs were performed during the study period, with 97.5%, 88.6% and 73.8% survival at 30 days, 1 year and 3 years, respectively. Twenty-two patients (7.9%) had severe allograft dysfunction leading to ECMO support. Twelve patients received single-lung (SLTx), 8 double-lung (BLTx), 1 single-lung/kidney (SLKTx) and 1 heart/lung (HLTx) transplantation. Thirty-day, 1-year and 3-year survival of LTx recipients with ECMO support post-operatively were 74.6%, 54% and 36%, respectively. MOF was the predominant cause of death (58.3%) in patients on ECMO support for PGD.

CONCLUSIONS

Our data suggest that, in addition to prolonged ventilation and pharmacologic support, ECMO should be considered as a bridge to recovery from PGD in lung transplantation. Early institution of ECMO may lead to diminished mortality in the setting of ALI despite the high incidence of MOF. Late institution of ECMO was associated with 100% mortality in this investigation.

Effect of positive end-expiratory pressure and tidal volume on lung injury induced by alveolar instability

INTRODUCTION

One potential mechanism of ventilator-induced lung injury (VILI) is due to shear stresses associated with alveolar instability (recruitment/derecruitment). It has been postulated that the optimal combination of tidal volume (Vt) and positive end-expiratory pressure (PEEP) stabilizes alveoli, thus diminishing recruitment/derecruitment and reducing VILI. In this study we directly visualized the effect of Vt and PEEP on alveolar mechanics and correlated alveolar stability with lung injury.

METHODS

In vivo microscopy was utilized in a surfactant deactivation porcine ARDS model to observe the effects of Vt and PEEP on alveolar mechanics. In phase I (n = 3), nine combinations of Vt and PEEP were evaluated to determine which combination resulted in the most and least alveolar instability. In phase II (n = 6), data from phase I were utilized to separate animals into two groups based on the combination of Vt and PEEP that caused the most alveolar stability (high Vt [15 cc/kg] plus low PEEP [5 cmH2O]) and least alveolar stability (low Vt [6 cc/kg] and plus PEEP [20 cmH2O]). The animals were ventilated for three hours following lung injury, with in vivo alveolar stability measured and VILI assessed by lung function, blood gases, morphometrically, and by changes in inflammatory mediators.

RESULTS

High Vt/low PEEP resulted in the most alveolar instability and lung injury, as indicated by lung function and morphometric analysis of lung tissue. Low Vt/high PEEP stabilized alveoli, improved oxygenation, and reduced lung injury. There were no significant differences between groups in plasma or bronchoalveolar lavage cytokines or proteases.

CONCLUSION

A ventilatory strategy employing high Vt and low PEEP causes alveolar instability, and to our knowledge this is the first study to confirm this finding by direct visualization. These studies demonstrate that low Vt and high PEEP work synergistically to stabilize alveoli, although increased PEEP is more effective at stabilizing alveoli than reduced Vt. In this animal model of ARDS, alveolar instability results in lung injury (VILI) with minimal changes in plasma and bronchoalveolar lavage cytokines and proteases. This suggests that the mechanism of lung injury in the high Vt/low PEEP group was mechanical, not inflammatory in nature.

Neuromuscular blocking agents decrease inflammatory response in patients presenting with acute respiratory distress syndrome*

OBJECTIVE

To evaluate the effects of neuromuscular blocking agents (NMBAs) on pulmonary and systemic inflammation in patients with acute respiratory distress syndrome ventilated with a lung-protective strategy.

DESIGN

Multiple-center, prospective, controlled, and randomized trial.

SETTING

One medical and two medical-surgical intensive care units.

PATIENTS

A total of 36 patients with acute respiratory distress syndrome (Pao2/Fio2 ratio of < or =200 at a positive end-expiratory pressure of > or =5 cm H2O) were included within 48 hrs of acute respiratory distress syndrome onset.

INTERVENTIONS

Patients were randomized to receive conventional therapy plus placebo (n = 18) or conventional therapy plus NMBAs (n = 18) for 48 hrs. Both groups were ventilated with a lung-protective strategy (tidal volume between 4 and 8 mL/kg ideal body weight, plateau pressure of < or =30 cm H2O).

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavages and blood samples were performed, before randomization and at 48 hrs, to determine the concentrations of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-8. Pao2/Fio2 ratio was evaluated before randomization and at 24, 48, 72, 96, and 120 hrs. A decrease over time in IL-8 concentrations (p = .034) was observed in the pulmonary compartment of the NMBA group. At 48 hrs after randomization, pulmonary concentrations of IL-1beta (p = .005), IL-6 (p = .038), and IL-8 (p = .017) were lower in the NMBA group as compared with the control group. A decrease over time in IL-6 (p = .05) and IL-8 (p = .003) serum concentrations was observed in the NMBA group. At 48 hrs after randomization, serum concentrations of IL-1beta (p = .037) and IL-6 (p = .041) were lower in the NMBA group as compared with the control group. A sustained improvement in Pao2/Fio2 ratio was observed and was reinforced in the NMBA group (p < .001).

CONCLUSION

Early use of NMBAs decrease the proinflammatory response associated with acute respiratory distress syndrome and mechanical ventilation.

Severe respiratory failure: advanced treatment options

BACKGROUND

Severe respiratory failure (including acute lung injury and acute respiratory distress syndrome) continues to be associated with significant mortality and morbidity in patients of all ages.

OBJECTIVE

To review the laboratory and clinical data in support of and future directions for the advanced treatment of severe respiratory failure.

DATA SOURCES

MEDLINE/PubMed search of all relevant primary and review articles.

DATA SYNTHESIS

Our understanding of lung pathophysiology and the role of ventilator-induced lung injury through basic science investigation has led to advances in lung protective strategies for the mechanical ventilation support of patients with severe respiratory failure. Specific modalities reviewed include low-tidal volume ventilation, permissive hypercapnia, the open lung approach, recruitment maneuvers, airway pressure release ventilation, high-frequency oscillatory ventilation, prone positioning, and extracorporeal life support. The pharmacologic strategies (including corticosteroids, surfactant, and nitric oxide) investigated for the treatment of severe respiratory failure are also reviewed.

CONCLUSION

In patients with severe respiratory failure, an incremental approach to the management of severe hypoxemia requires implementation of the strategies reviewed, with knowledge of the evidence base to support these strategies.

Dynamic versus static respiratory mechanics in acute lung injury and acute respiratory distress syndrome

OBJECTIVES

It is not clear whether the mechanical properties of the respiratory system assessed under the dynamic condition of mechanical ventilation are equivalent to those assessed under static conditions. We hypothesized that the analyses of dynamic and static respiratory mechanics provide different information in acute respiratory failure.

DESIGN

Prospective multiple-center study.

SETTING

Intensive care units of eight German university hospitals.

PATIENTS

A total of 28 patients with acute lung injury and acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS

Dynamic respiratory mechanics were determined during ongoing mechanical ventilation with an incremental positive end-expiratory pressure (PEEP) protocol with PEEP steps of 2 cm H2O every ten breaths. Static respiratory mechanics were determined using a low-flow inflation.

MAIN RESULTS

The dynamic compliance was lower than the static compliance. The difference between dynamic and static compliance was dependent on alveolar pressure. At an alveolar pressure of 25 cm H2O, dynamic compliance was 29.8 (17.1) mL/cm H2O and static compliance was 59.6 (39.8) mL/cm H2O (median [interquartile range], p < .05). End-inspiratory volumes during the incremental PEEP trial coincided with the static pressure-volume curve, whereas end-expiratory volumes significantly exceeded the static pressure-volume curve. The differences could be attributed to PEEP-related recruitment, accounting for 40.8% (10.3%) of the total volume gain of 1964 (1449) mL during the incremental PEEP trial. Recruited volume per PEEP step increased from 6.4 (46) mL at zero end-expiratory pressure to 145 (91) mL at a PEEP of 20 cm H2O (p < .001). Dynamic compliance decreased at low alveolar pressure while recruitment simultaneously increased. Static mechanics did not allow this differentiation. The decrease in static compliance occurred at higher alveolar pressures compared with the dynamic analysis.

CONCLUSIONS

Exploiting dynamic respiratory mechanics during incremental PEEP, both compliance and recruitment can be assessed simultaneously. Based on these findings, application of dynamic respiratory mechanics as a diagnostic tool in ventilated patients should be more appropriate than using static pressure-volume curves.

Corticosteroids combined with continuous veno-venous hemodiafiltration for treatment of hantavirus pulmonary syndrome caused by Puumala virus infection

Reported here are two cases of hantavirus pulmonary syndrome caused by Puumala virus infection, which rapidly resolved after initiation of corticosteroid treatment combined with continuous veno-venous hemodiafiltration. These cases emphasize the role of the inflammatory response in the pathogenesis of hantavirus pulmonary syndrome.

Open lung ventilation in neurosurgery: an update on brain tissue oxygenation

Recently, we showed the feasibility of ventilating neurosurgical patients with acute intracranial pathology and concomitant acute respiratory distress syndrome (ARDS) according the so-called Open Lung approach. This technique consists of low tidal volume, elevated positive expiratory pressure (PEEP) level and initial recruitment maneuvers to open up collapsed alveoli. In this report, we focus on our experience to guide recruitment with brain tissue oxygenation (pbrO2) probes. We studied recruitment maneuvers in thirteen patients with ARDS and acute brain injury such as subarachnoid hemorrhage and traumatic brain injury. A pbrO2 probe was implanted in brain tissue at risk for hypoxia. Recruitment maneuvers were performed at an inspired oxygen frcation (FiO2) of 1.0 and a PEEP level of 30 40 cmH2O for 40 seconds. The mean FiO2 necessary for normoxemia could be decreased from 0.85 +/- 0.17 before recruitment to 0.55 +/- 0.12 after 24 hours, while mean PbrO2 (24.6 mmHg before recruitment) did not change. At a mean of 17 minutes after the first recruitment maneuver, PbrO2 showed peak a value of 35.6 +/- 16.6 mmHg, reflecting improvement in arterial oxygenation at an FiO2 of 1.0. Brain tissue oxygenation monitoring provides a useful adjunct to estimate the effects of recruitment maneuvers and ventilator settings in neurosurgical patients with acute lung injury.

Regional pulmonary pressure volume curves in mechanically ventilated patients with acute respiratory failure measured by electrical impedance tomography

BACKGROUND

We hypothesized, that in mechanically ventilated patients with acute respiratory failure, regional pressure volume curves differ markedly from conventional global pressure volume curves of the whole lung.

METHODS

In nine mechanically ventilated patients with acute respiratory failure during an inspiratory low-flow manoeuvre, conventional global pressure volume curves were registered by spirometry and regional pressure volume curves in up to 912 regions were assessed simultaneously using electrical impedance tomography. We compared the lower (LIP) and upper (UIP) inflection points obtained from the conventional global pressure volume curve and regional pressure volume curves.

RESULTS

We identified from the conventional global pressure volume curves LIP [3-11 (8) cmH2O] in eight patients and UIP [31-39 (33) cmH2O] in three patients. Using electrical impedance tomography (EIT), LIP [3-18 (8) cmH2O] in 54-264 (180) regions and UIP [23-42 (36) cmH2O] in 149-324 (193) regions (range and median) were identified. Lung mechanics measured by conventional global pressure volume curves are similar to the median of regional pressure volume curves obtained by EIT within the tomographic plane. However, single regional pressure volume curves differ markedly with a broad heterogeneity of lower and upper inflection points.

CONCLUSION

Lower and upper inflection points obtained from conventional global pressure volume curves are not representative of all regions of the lungs.

Rekrutierungsmanöver bei Patienten mit Lungenversagen

Recruitment maneuvers have been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung regions. Although, in most patients recruitment maneuvers improve gas exchange a controversial discussion on recruitment maneuvers remains. This article reviews the physiological and patho-physiological backgrounds of recruitment maneuvers. The different recruitment maneuvers and possible monitoring are discussed as well as the influence of recruitment on other organs. Furthermore, we discuss whether recruitment maneuvers are useful if patients with acute lung injury or acute respiratory distress syndrome are ventilated with a lung-protective strategy.

Predictive value of thyroid hormones on the first day in adult respiratory distress syndrome patients admitted to ICU: comparison with SOFA and APACHE II scores

BACKGROUND

Thyroid hormone dysfunction could affect outcome and increase mortality in critical illness. Therefore, in a prospective, observational study we analyzed and compared the prognostic accuracy of free tri-iodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), along with the APACHE II and SOFA scoring systems in predicting intensive care unit (ICU) mortality in critically ill patients.

PATIENTS AND METHODS

Physiology scores were calculated for the first 24 hours after ICU admission in 206 patients with acute respiratory distress syndrome. APACHE II and SOFA scores were employed to determine the initial severity of illness. Thyroid hormones were measured within the first 24 hours. Logistic regression models were created for APACHE II scores, SOFA scores, and thyroid hormone levels. The models predicted high- and low-risk subgroups. Models that showed a good fit were stratified by Kaplan-Meier survival curves.

RESULTS

There were 98 (47.6%) survivors and 108 (52.4%) non-survivors. The survivors had a lower APACHE II score (11.50 vs 15.82, P < 0.0005), a lower SOFA score (6.06 vs 9.42, P < 0.0005), a younger age (57 vs 70 years, P = 0.008), a shorter ICU stay (13 vs 16 days, P = 0.012), and a higher fT3 level (2.18 vs 1.72 pg/mL, P = 0.002) than non-survivors. ICU survival was most closely predicted by a model that included age and fT3 and a model that included APACHE II and APACHE II*sex.

CONCLUSION

In critically ill patients, serum fT3 concentrations markedly decreased after ICU admission among non-survivors. According to our findings, fT3 levels might have additive discriminatory power to age, SOFA and APACHE II scores in predicting short-term mortality in ARDS patients admitted to ICU.

Response of acoustic transmission to positive airway pressure therapy in experimental lung injury

OBJECTIVE

To evaluate the effect of positive end-expiratory pressure on the sound filtering characteristics of injured lungs.

DESIGN AND SETTING

Prospective experimental study in the animal laboratory in an academic medical center.

PATIENTS AND PARTICIPANTS

Six 35- to 45-kg anesthetized, intubated pigs.

INTERVENTIONS

Acute lung injury with intravenous oleic acid.

MEASUREMENTS AND RESULTS

We injected a multifrequency broad-band sound signal into the airway while recording transmitted sound at three locations bilaterally on the chest wall. Oleic acid injections effected a severe pulmonary edema predominantly in the dependent lung regions, with an average increase in venous admixture from 16+/-14% to 57+/-13% and a reduction in static respiratory system compliance from 31+/-6 to 16+/-3 ml/cm H(2)O. A significant concomitant increase in sound transfer function amplitude was seen in the dependent and lateral lung regions; little change occurred in the nondependent areas. The application of PEEP resulted in a decrease in venous admixture, increase in respiratory system compliance, and return of the sound transmission to preinjury levels.

CONCLUSIONS

Acute lung injury causes regional acoustic transmission abnormalities that are reversed during alveolar recruitment with PEEP.

[Management of acute pulmonary failure: diagnostics-ventilation-withdrawal]

Acute pulmonary failure by definition excludes cardiac insufficiency as the pathogenetic mechanism involved in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The systemic inflammatory reaction underlying acute pulmonary failure has many etiological causes. One of the most important trigger mechanisms is sepsis. In the realm of cardiac intensive care medicine, the systemic inflammatory reaction is observed in conjunction with assist systems, during extracorporeal circulation, or in the course of cardiogenic shock. In the end, even mechanical ventilation itself can elicit an inflammatory reaction and result in pulmonary failure through ventilator-associated lung injury. Knowledge of the mechanisms has led to the concept of protective ventilation, which exerts both prophylactic and therapeutic effects. Protective ventilation is an integral part of a bundle of therapeutic intensive care measures. Both constitute the essence of management of acute pulmonary failure.

Pressure-volume curve variations after a recruitment manoeuvre in acute lung injury/ARDS patients: implications for the understanding of the inflection points of the curve

BACKGROUND AND OBJECTIVE

Although the pressure-volume (P-V) curve has been proposed in the management of mechanically ventilated patients, its interpretation remains unclear. Our aim has been to study the variations of the P-V curve after a recruitment manoeuvre (RM). Our hypothesis was that the lower inflection point (LIP) represents the presence of compressive atelectases, so it should not change after lung recruitment, while the upper inflection point (UIP) reflects reabsorptive atelectases, and an effective recruitment should result in changes at this level.

METHODS

Two P-V curves (quasi-static method) separated by an RM (40 cmH2O, two consecutive manoeuvres) were plotted in 35 postoperative patients with criteria of acute lung injury/acute respiratory distress syndrome (ARDS). LIP, UIP and expiratory inflection point (EIP) were defined as the first point where the curve consistently starts to separate from the line.

RESULTS

One to six measurements were obtained per patient (73 procedures). Neither the lower nor the EIPs varied significantly after the RM (P = 0.11 and 0.35, respectively). An UIP was observed in 18 curves (25%) before the RM and disappeared on nine occasions after the recruitment. Similar results were obtained when first measurements only were analysed, and when the cause (pulmonary vs. extrapulmonary), severity of lung injury or duration of mechanical ventilation at first measurement were studied.

CONCLUSIONS

An RM does not modify the LIP significantly, but induces the disappearance of the UIP in 50% of the cases in which this point is found.

Regulation of vascular endothelial growth factor bioactivity in patients with acute lung injury

BACKGROUND

Reduced bioactive vascular endothelial growth factor (VEGF) has been demonstrated in several inflammatory lung conditions including the acute respiratory distress syndrome (ARDS). sVEGFR-1, a soluble form of VEGF-1 receptor, is a potent natural inhibitor of VEGF. We hypothesised that sVEGFR-1 plays an important role in the regulation of the bioactivity of VEGF within the lung in patients with ARDS.

METHODS

Forty one patients with ARDS, 12 at risk of developing ARDS, and 16 normal controls were studied. Bioactive VEGF, total VEGF, and sVEGFR-1 were measured by ELISA in plasma and bronchoalveolar lavage (BAL) fluid. Reverse transcriptase polymerase chain reaction for sVEGFR-1 was performed on BAL cells.

RESULTS

sVEGFR-1 was detectable in the BAL fluid of 48% (20/41) of patients with early ARDS (1.4-54.8 ng/ml epithelial lining fluid (ELF)) compared with 8% (1/12) at risk patients (p = 0.017) and none of the normal controls (p = 0.002). By day 4 sVEGFR-1 was detectable in only 2/18 ARDS patients (p = 0.008). Patients with detectable sVEGFR-1 had lower ELF median (IQR) levels of bioactive VEGF than those without detectable sVEGFR-1 (1415.2 (474.9-3192) pg/ml v 4761 (1349-7596.6) pg/ml, median difference 3346 pg/ml (95% CI 305.1 to 14711.9), p = 0.016), but there was no difference in total VEGF levels. BAL cells expressed mRNA for sVEGFR-1 and produced sVEGFR-1 protein which increased following incubation with tumour necrosis factor alpha.

CONCLUSION

This study shows for the first time the presence of sVEGFR-1 in the BAL fluid of patients with ARDS. This may explain the presence of reduced bioactive VEGF in patients early in the course of ARDS.

Recruitment maneuvers during prone positioning in patients with acute respiratory distress syndrome

OBJECTIVE

To evaluate the interaction of recruitment maneuvers and prone positioning on gas exchange and venous admixture in patients with early extrapulmonary acute respiratory distress syndrome ventilated with high levels of positive end-expiratory pressure. We hypothesized that a sustained inflation performed after 6 hrs of prone positioning would induce sustained improvement in oxygenation (Pao2/Fio2) and venous admixture.

DESIGN

Prospective, interventional study.

SETTING

Tertiary care, postoperative intensive care unit.

PATIENTS

Fifteen patients with early extrapulmonary acute respiratory distress syndrome.

INTERVENTIONS

After 6 hrs of prone positioning, a sustained inflation was performed with 50 cm H2O maintained for 30 secs. Data were recorded in supine position, after 6 hrs of prone positioning, at 3, 30, and 180 mins following the sustained inflation.

MEASUREMENTS AND MAIN RESULTS

A response to prone positioning was observed in nine of 15 patients leading to an improvement of Pao2/Fio2 (147 +/- 37 torr vs. 225 +/- 77 torr, p = .005) and venous admixture (35.4 +/- 8.3% vs. 28.9 +/- 9.8%, p = .001). Six patients did not respond to prone positioning. Following the sustained inflation, the responders to prone positioning showed a further increase of Pao2/Fio2 and decrease of venous admixture at 3 mins (Pao2/Fio2, 225 +/- 77 torr vs. 368 +/- 90 torr, p = .018; venous admixture, 28.9 +/- 9.8% vs. 18.9 +/- 6.7%, p = .05). In all six nonresponders to prone positioning, an improvement of Pao2/Fio2 and venous admixture occurred at 3 mins following the sustained inflation (128 +/- 18 torr vs. 277 +/- 59 torr, p = .03; venous admixture, 34.2 +/- 6.0% vs. 23.8 +/- 6.3%, p = .05). The beneficial effects of the sustained inflation remained significantly elevated over 3 hrs in responders and nonresponders to prone positioning.

CONCLUSION

In patients with early extrapulmonary acute respiratory distress syndrome, a sustained inflation performed after 6 hrs of prone positioning induced further and sustained improvement of oxygenation and venous admixture in both responders and nonresponders to prone positioning.

Acute respiratory distress syndrome criteria in trauma patients: why the definitions do not work

BACKGROUND

The international consensus definitions for acute respiratory distress syndrome (ARDS) have formed the basis for recruitment into randomized, controlled trials and, more recently, standardized the protocols for ventilatory treatment of acute lung injury. Although possibly appropriate for sepsis-induced ARDS, these criteria may not be appropriate for posttraumatic ARDS if the disease patterns are widely divergent. This study tests the hypothesis that standard ARDS criteria applied to the trauma population will capture widely disparate forms of acute lung injury and are too nonspecific to identify a population at risk for prolonged respiratory failure and associated complications.

METHODS

Patients with and Injury Severity Score > or = 16 ventilated for > 12 hours were prospectively enrolled. Clinical data, including elements of cardiovascular, renal, hepatic, hematologic, neurologic, and pulmonary function, were collected daily. Two hundred fifty-four patients were enrolled over a 36-month period, of whom 70 met the consensus definitions of ARDS. Patients from whom support was withdrawn within 48 hours were excluded. The remaining 61 patients were stratified into two groups on the basis of intubation (n = 12) days.

RESULTS

There was considerable disparity in severity and clinical course. A mild, limited form of ARDS was characterized by earlier onset (group 1, 2 days; group 2, 4 days; p = 0.002), fewer intubation days (7 days vs. 28 days; p < 0.001), and less severe derangements in lung mechanics. A significant difference between the two groups was also seen in systemic inflammatory response syndrome score, incidence of sepsis, and incidence of multiple organ failure.

CONCLUSION

The criteria for ARDS, when applied to the trauma population, capture a widely disparate group and has poor specificity for identifying patients at risk. Recruitment of trauma patients for ARDS studies or preemptive ventilatory management based solely on these criteria may be ill-advised.

Keratinocyte growth factor induces Akt kinase activity and inhibits Fas-mediated apoptosis in A549 lung epithelial cells

Acute respiratory distress syndrome (ARDS) is a syndrome characterized by the rapid influx of protein-rich edema fluid into the air spaces. The magnitude of alveolar epithelial cell injury is a key determinant of disease severity and an important predictor of patient outcome. The alveolar epithelium is positioned at the interface of the host response in the initiation, progression, and recovery phase of the disease. Keratinocyte growth factor (KGF) is a potent survival factor unique to the epithelium that promotes lung epithelial cell survival, accelerates wound closure, and reduces fibrosis. We therefore hypothesized that KGF preserves lung function by inhibiting apoptosis through activation of a signal transduction pathway responsible for cell survival. To test this hypothesis we determined that KGF inhibits death following Fas activation, a relevant apoptosis pathway, and then determined that cell survival is mediated through activation of the phosphatidylinositol 3'-kinase (PI3K)/Akt kinase signal transduction pathway. We found that KGF induces a dose- and time-dependent increase in Akt kinase activity and that, as expected, activation of Akt via KGF is PI3K dependent. KGF inhibited Fas-induced apoptosis as measured by a reduction in apoptotic cells and caspase-3 activity. This investigation supports our original hypothesis that KGF protects the lung epithelium by inhibiting apoptosis and that protection occurs through activation of PI3K/Akt-mediated cell survival pathway. Our results are in agreement with other reports that identify the PI3K/Akt axis as a key intracellular pathway in the lung epithelium that may serve as a therapeutic target to preserve epithelial integrity during inflammation.

Respiratory failure in interstitial lung disease

PURPOSE OF REVIEW

Respiratory failure associated with interstitial lung disease (ILD) occurs commonly, often as a terminal event after a prolonged course of illness. Diagnosis and management of the underlying ILD and respiratory failure pose great challenges.

RECENT FINDINGS

Respiratory failure in the absence of a clearly identifiable cause has a high mortality and frequent complications. Patients with idiopathic pulmonary fibrosis who are admitted with respiratory failure have a grim prognosis and may not benefit from prolonged aggressive therapy including mechanical ventilation. Presence of diffuse alveolar damage or usual interstitial pneumonia on lung biopsy specimens from patients with respiratory failure may be a marker of poor prognosis. Recently, the importance of the clinical-radiologic-pathologic diagnosis has been emphasized.

SUMMARY

The prognosis and treatment may vary according to the type of ILD and the cause of the respiratory failure, which must therefore be established before treatment is initiated. Prevention of iatrogenesis and timely application of palliation are as important as specific treatment of underlying ILD.

Ventilation with Smaller Tidal Volumes: A Quantitative Systematic Review of Randomized Controlled Trials

In this quantitative systematic review we assessed the effects of ventilation with smaller tidal volume (VT) on morbidity and mortality in patients aged 16 yr or older affected by acute lung injury and acute respiratory distress syndrome. Five randomized trials (1202 patients) comparing ventilation using smaller VT and/or low airway driving pressure (plateau pressure 30 cm H2O or less), resulting in VT of 7 mL/kg or less versus ventilation that uses VT in the range of 10 to 15 mL/kg, were identified after a systematic search of The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, databases of current research, reference lists, and "gray literature." Mortality at day 28 was significantly reduced by lung-protective ventilation (relative risk [RR], 0.74; confidence interval [CI], 0.61-0.88), whereas beneficial effect on long-term mortality was uncertain (RR, 0.84; CI, 0.68-1.05). The comparison between small and conventional VT was not significantly different if a plateau pressure less than or equal to 31 cm H2O in the control group was used (RR, 1.13; CI, 0.88-1.45). Clinical heterogeneity, such as different lengths of follow-up and higher plateau pressures in control arms in two trials, make the interpretation of the combined results difficult.

Infectious and inflammatory dissemination are affected by ventilation strategy in rats with unilateral pneumonia

OBJECTIVE

To evaluate the effect of V(T) reduction and alveolar recruitment on systemic and contralateral dissemination of bacteria and inflammation during right-side pneumonia.

DESIGN

Interventional animal study. SETTING. University hospital research laboratory.

SUBJECTS

A total of 54 male Wistar rats.

INTERVENTIONS

One day after right lung instillation of 1.4x10(7) Pseudomonas aeruginosa, rats were left unventilated or ventilated for 2 h at low V(T) (6 ml/kg) with different strategies of alveolar recruitment: no PEEP, 8 cm H(2)O PEEP, 8 cm H(2)O PEEP in a left lateral position, 3 cm H(2)O PEEP with partial liquid ventilation, or high V(T) (set such as end-inspiratory pressure was 30 cm H(2)O) without PEEP (ZEEP). After ventilation the lungs, spleen and liver were cultivated for bacterial counts. Global bacterial dissemination was scored considering the percentage of positive spleen, liver and left lung cultures. TNF-alpha was assayed in plasma before and after mechanical ventilation.

MEASUREMENTS AND RESULTS

All rats had right-side pneumonia with similar bacterial counts. All mechanical ventilation strategies, with the exception of low V(T)-PEEP 8, promoted contralateral lung dissemination. Overall bacterial dissemination was less in non-ventilated controls (22%) and low V(T)-PEEP 8 (22%) than in high V(T)-ZEEP (67%), low V(T)-PEEP 8 in left lateral position (59%) and low V(T)-ZEEP (56%) ( p<0.05). Partial liquid ventilation prevented systemic bacterial translocation, but at the expense of contralateral bacterial seeding. Plasma TNF-alpha concentration increased significantly after mechanical ventilation with no PEEP at both high and low V(T).

CONCLUSIONS

Our results suggest that PEEP might reduce the risk of ventilation-induced bacterial and inflammatory mediator dissemination during pneumonia.

Ventilation with lower tidal volumes versus traditional tidal volumes in adults for acute lung injury and acute respiratory distress syndrome

BACKGROUND

Patients with acute respiratory distress syndrome and acute lung injury require mechanical ventilatory support. Acute respiratory distress syndrome and acute lung injury are further complicated by ventilator-induced lung injury. Lung-protective ventilation strategies may lead to improved survival.

OBJECTIVES

To assess the effects of ventilation with lower tidal volume on morbidity and mortality in patients aged 16 years or older affected by acute respiratory distress syndrome and acute lung injury. A secondary objective was to determine whether the comparison between low and conventional tidal volume was different if a plateau airway pressure of greater than 30 to 35 cm H20 was used.

SEARCH STRATEGY

We searched The Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library issue 4, 2003; MEDLINE (1966 to October 2003); EMBASE and CINAHL (1982 to October 2003); intensive care journals and conference proceedings; databases of ongoing research, reference lists and 'grey literature'.

SELECTION CRITERIA

Randomized trials comparing ventilation using either lower tidal volume or low airway driving pressure (plateau pressure 30 cm H(2)O or less), resulting in tidal volume of 7 ml/kg or less versus ventilation that uses Vt in the range of 10 to 15 ml/kg, in adults (aged 16 years or older).

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. Wherever appropriate, results were pooled. Fixed and random effects models were applied.

MAIN RESULTS

Five trials, involving 1202 patients, were eligible. Mortality at day 28 was significantly reduced by lung-protective ventilation: relative risk 0.74 (confidence interval 0.61 to 0.88), whereas beneficial effect on long-term mortality was uncertain: relative risk 0.84 (confidence interval 0.68 to 1.05). The comparison between low and conventional tidal volume was not significantly different if a plateau pressure less than or equal to 31 cm H2O in control group was used: relative risk 1.13 (confidence interval 0.88 to 1.45). There was insufficient evidence about morbidity and long term outcomes.

REVIEWERS' CONCLUSIONS

Clinical heterogeneity, such as different lengths of follow up and higher plateau pressure in control arms in two trials make the interpretation of the combined results difficult. Mortality is significantly reduced at day 28 and the effects on long term mortality are uncertain, although the possibility of a clinically relevant benefit cannot be excluded.

Five-Year results of 219 consecutive patients treated with extracorporeal membrane oxygenation for refractory postoperative cardiogenic shock

BACKGROUND

Postcardiotomy cardiogenic shock occurs in approximately 1% of patients. We prospectively evaluated the early and long-term outcome as well as predictors of survival when using temporary extracorporeal membrane oxygenation (ECMO) support.

METHODS

During 5 years 219 of 18150 patients (1.2%) undergoing cardiac surgery (coronary artery bypass grafting, n = 119; aortic valve replacement, n = 24; coronary artery bypass grafting and aortic valve replacement, n = 21; coronary artery bypass grafting and mitral valve replacement, n = 11; other procedures, n = 44) required temporary postoperative ECMO support. The ECMO implantation was performed through the femoral vessels or through the right atrium and ascending aorta. Additional intraaortic balloon counterpulsation was employed in 144 patients to improve coronary blood flow.

RESULTS

Mean duration of ECMO support was 2.8 +/- 2.2 days. One hundred thirty-four patients (60%) were successfully weaned from ECMO. Of these, 52 patients (24%) were discharged from the hospital after 29.9 +/- 24 days. The main cause of death was myocardial failure. Five-year follow-up is 96% complete; 37 patients (74%) were alive with reasonable exercise capacity.

CONCLUSIONS

Extracorporeal membrane oxygenation is an acceptable technique for short-term treatment of refractory postoperative low cardiac output. It can save the lives of a group of very high risk patients.

Differences in the deflation limb of the pressure-volume curves in acute respiratory distress syndrome from pulmonary and extrapulmonary origin

OBJECTIVE

To assess the differences in the deflation pressure-volume (PV) curves between acute respiratory distress syndrome from pulmonary (ARDSp) and extrapulmonary (ARDSe) origin.

DESIGN

. Prospective study.

SETTING

Twenty-bed intensive care unit in an university hospital.

PATIENTS

Ten patients within the first 24 h from meeting ARDS criteria, classified as ARDSp or ARDSe in a clinical basis.

INTERVENTIONS

A deflation PV curve was recorded by means of decreasing steps of continuous positive airway pressure (CPAP) from 35 to 0 cmH(2)O.

RESULTS

The simultaneous recording of pressure at the airway opening (Pao), esophageal pressure (Pes) and volumes (V) allows us to trace the Pao-V, Pes-V and transpulmonary pressure (Ptp)-V curves. These data were fitted to a sigmoid model and ARDSp and ARDSe groups were compared. ARDSp has lower lung compliance and higher chest wall compliance than ARDSe (35.9+/-11.3 vs. 77.2+/-50.6 and 199.6+/-44.4 vs. 125.5+/-16.5 ml/cmH(2)O, respectively, P<0.05). The Pao-V curve in ARDSp is shifted down and right with respect to ARDSe. The Ptp-V curve shows a similar displacement. The Pes-V curve in the ARDSp group is, however, shifted to the left. When relative values (percentage to the maximum volume achieved at 35 cmH(2)O) are considered, these differences persist, but, in the Ptp-V curves, are only significant in the low-pressure range.

CONCLUSIONS

Differences between ARDSp and ARDSe PV curves are present all along the pressure axis and are related to differences not only in the Pes-V curve, but also in the Ptp-V curve.

Epidemiology and outcome of acute lung injury in European intensive care units. Results from the ALIVE study

OBJECTIVES

To re-examine the epidemiology of acute lung injury (ALI) in European intensive care units (ICUs).

DESIGN AND SETTING

A 2-month inception cohort study in 78 ICUs of 10 European countries.

PATIENTS

All patients admitted for more than 4 h were screened for ALI and followed up to 2 months.

MEASUREMENTS AND MAIN RESULTS

Acute lung injury occurred in 463 (7.1%) of 6,522 admissions and 16.1% of all mechanically ventilated patients; 65.4% cases occurred on ICU admission. Among 136 patients initially presenting with "mild ALI" (200< PaO2/FiO2 < or =300), 74 (55%) evolved to acute respiratory distress syndrome (ARDS) within 3 days. Sixty-two patients (13.4%) remained with mild ALI and 401 had ARDS. The crude ICU and hospital mortalities were 22.6% and 32.7% (p<0.001), and 49.4% and 57.9% (p=0.0005), respectively, for mild ALI and ARDS. ARDS patients initially received a mean tidal volume of 8.3+/-1.9 ml/kg and a mean PEEP of 7.7+/-3.6 cmH2O; air leaks occurred in 15.9%. After multivariate analysis, mortality was associated with age (odds ratio (OR) =1.2 per 10 years; 95% confidence interval (CI): 1.05-1.36), immuno-incompetence (OR: 2.88; Cl: 1.57-5.28), the severity scores SAPS II (OR: 1.16 per 10% expected mortality; Cl: 1.02-1.31) and logistic organ dysfunction (OR: 1.25 per point; Cl: 1.13-1.37), a pH less than 7.30 (OR: 1.88; Cl: 1.11-3.18) and early air leak (OR: 3.16; Cl: 1.59-6.28).

CONCLUSIONS

Acute lung injury was frequent in our sample of European ICUs (7.1%); one third of patients presented with mild ALI, but more than half rapidly evolved to ARDS. While the mortality of ARDS remains high, that of mild ALI is twice as low, confirming the grading of severity between the two forms of the syndrome.

Inhaled nitric oxide for acute hypoxic respiratory failure in children and adults: a meta-analysis

We systematically reviewed randomized controlled trials examining inhaled nitric oxide (INO) for the treatment of acute respiratory distress syndrome or acute lung injury in children and adults. Qualitative assessments of identified trials were made, and metaanalyses were performed according to Cochrane methodology. Five randomized controlled trials (n = 535) met entry criteria. One study demonstrated significant improvement in oxygenation in the first 4 days of treatment, with no difference after this. There was no difference in ventilator-free days between treatment and placebo groups, and no specific dose of INO was more advantageous than any other. INO had no effect on mortality in trials without crossover of treatment failures to open-label INO (relative risk, 0.98; 95% confidence interval, 0.66-1.44). Other clinical indicators of effectiveness, such as duration of hospital and intensive care stay, were inconsistently reported. Lack of data prevented assessment of all outcomes. If further trials assessing INO in acute respiratory distress syndrome or acute lung injury are to proceed, they should be stratified for primary etiology, incorporate other modalities that may affect outcome, and evaluate clinically relevant outcomes before any benefit of INO can be excluded.

Measurements of Alveolar pO2 Using 19F-MRI in Partial Liquid Ventilation

RATIONALE AND OBJECTIVES

Partial liquid ventilation using Perfluorcarbon (PFC) is an innovative treatment of acute respiratory distress syndrome. However, the underlying mechanisms are not totally clear. The aim was to investigate the distribution of oxygen partial pressure within the PFC-filled lung (ppO2).

METHODS

Nine pigs underwent partial liquid ventilation, receiving 20 mL PFC/kg bodyweight (bw). Measurements were obtained by a chemical shift selective TurboFLASH sequence at different axial lung levels. ppO2 was calculated from 19F-MRI by nonlinear curve T1-fitting technique after noise correction.

RESULTS

Quantification and distribution of ppO2 was performed successfully. A narrow relationship of the inspiratory O2 fraction and ppO2, as well as a significant ventral-to-dorsal gradient of ppO2 (ventral:dependent lung = 1.9:1) were detected in all subjects and slice positions.

CONCLUSIONS

In vivo measurement of local ppO2 gains new and clinical important insights into the physiology of PLV. The previously unknown ppO2 gradient within PFC fits to distribution of perfusion. Dependent lung regions appear to have limited access to O2 from central airways.

Clinical review: the implications of experimental and clinical studies of recruitment maneuvers in acute lung injury

Mechanical ventilation can cause and perpetuate lung injury if alveolar overdistension, cyclic collapse, and reopening of alveolar units occur. The use of low tidal volume and limited airway pressure has improved survival in patients with acute lung injury or acute respiratory distress syndrome. The use of recruitment maneuvers has been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung tissue. Many investigators have studied the benefits of recruitment maneuvers in healthy anesthetized patients and in patients ventilated with low positive end-expiratory pressure. However, it is unclear whether recruitment maneuvers are useful when patients with acute lung injury or acute respiratory distress syndrome are ventilated with high positive end-expiratory pressure, and in the presence of lung fibrosis or a stiff chest wall. Moreover, it is unclear whether the use of high airway pressures during recruitment maneuvers can cause bacterial translocation. This article reviews the intrinsic mechanisms of mechanical stress, the controversy regarding clinical use of recruitment maneuvers, and the interactions between lung infection and application of high intrathoracic pressures.

Exhaled breath condensate nitrite and its relation to tidal volume in acute lung injury

STUDY OBJECTIVE

Mechanical ventilation may damage the lung. Low tidal volume (VT) is protective, but VT is scaled to body weight (BW) and may be high in functionally small ARDS lungs. We hypothesized that exhaled breath condensate (EBC) nitrite (NO(2)(-)) concentration may increase with lung distension.

DESIGN

Prospective, noncontrolled study.

SETTING

University hospital and medical ICU.

PATIENTS

Thirty-five ICU patients requiring mechanical ventilation (severe pneumonia, n = 31; exacerbated COPD, n = 4). Patients were scored according to American and European Consensus Conference on ARDS criteria (AECC) [no lung injury, n = 7; acute lung injury, n = 13; ARDS, n = 15], as well as the Murray lung injury severity score (LISS) [score 0, n = 3; score 0.1 to 2.5, n = 19; score > 2.5, n = 13].

INTERVENTIONS

EBC was collected and analyzed for NO(2)(-), interleukin (IL)-6, and IL-8. Serum was analyzed for IL-6, IL-8, and procalcitonin.

RESULTS

and measurements: EBC NO(2)(-) correlated well with VT (milliliters per kilogram of BW; r = 0.79, p < 0.0001) and expiratory minute volume (r = 0.60, p < 0.0001) but not with other ventilatory parameters or parameters of pulmonary (EBC IL-6, EBC IL-8) or systemic (serum IL-6, IL-8, and procalcitonin) inflammation. The ratio of EBC NO(2)(-) and the size of the VT correlated directly with lung injury (AECC, r = 0.66, p < 0.0001; LISS, r = 0.84, p < 0.0001).

CONCLUSION

EBC NO(2)(-) increased linearly with VT. The ratio of EBC NO(2)(-) to VT is assumed to reflect NO(2)(-) release at a given VT. An increase in this ratio indicates an inappropriate increase of NO(2)(-) production most likely due to mechanical stress of the remaining open lung units in injured lungs. We conclude that the EBC NO(2)(-)/VT ratio may help to identify situations of critical mechanical stress.

Is the implementation of research findings in the critically ill hampered by the lack of universal definitions of illness?

In the design of clinical trials, a clear definition of disease is essential for enrollment of a homogeneous study population with a higher likelihood of demonstrating a benefit of an intervention. A definition that is applicable to standard clinical practice enhances the ability of clinicians to apply results of the clinical trial to patient care. Use of a universally accepted definition allows valid comparisons across multiple studies. Sepsis, the acute respiratory distress syndrome, and ventilator-associated pneumonia are examples of conditions for which universal definitions developed by panels of experts have facilitated the design of successful clinical trials. However, implementation of the results of some of these studies has been complicated by a lack of understanding or acceptance of disease definitions or by their overly inclusive nature. For example, the presence of Systemic Inflammatory Response Syndrome (SIRS) will identify most patients with sepsis, however, a significant number of patients with those clinical findings will have other underlying processes. Approved definitions for VAP are cumbersome, and adherence to those definitions in the design of clinical trials is poor. This has led to confusion regarding the accuracy of diagnostic tests and poor acceptance of evidence based guidelines by clinicians. When investigators and clinicians do not adhere to common definitions of disease, results of clinical trials may be applied inappropriately or ignored altogether. More specific identifiers of critical illnesses using specific biochemical or genetic markers are being explored. This approach may also be useful for staging disease.

Occult herpes family viral infections are endemic in critically ill surgical patients

OBJECTIVE

Herpes family viruses have been recognized as pathogens for many years in immunosuppressed transplant or human immunodeficiency virus patients, but they have garnered little attention as potential pathogens in the nonimmunosuppressed critically ill. The objective of this study was to define the prevalence of and risk factors for development of herpes family virus infection in chronic critically ill surgical patients.

DESIGN

Prospective epidemiologic study.

SETTING

A 38-bed surgical intensive care unit in a major university hospital.

PATIENTS

Nonimmunosuppressed intensive care unit patients in intensive care unit for >/=5 days.

INTERVENTIONS

None; patients received no antiviral treatment during the study.

MEASUREMENTS AND MAIN RESULTS

Weekly cultures for cytomegalovirus (CMV) and herpes simplex virus, viral serologies, and T-cell counts were performed. The prevalence (95% confidence interval) of positive respiratory cultures for herpes simplex or CMV was 35% (22-49%); 15% (5-25%) cultured positive for CMV, 23% (11-35%) cultured positive for herpes simplex virus, and one patient's respiratory secretions culturing positive for both CMV and herpes simplex virus. The prevalence of CMV viremia was only 5.8% (1-10%). CMV+ patients had longer hospital admissions, intensive care unit admissions, and periods of ventilator dependence than CMV- patients, despite having comparable severity of illness scores. CMV+ patients also had significantly higher numbers of blood transfusions, prevalence of steroid exposure, and prevalence of hepatic dysfunction, and all were immunoglobulin G positive at the beginning of the study. In contrast, herpes simplex virus-positive patients had lengths of hospital admissions, lengths of intensive care unit admissions, and periods of ventilator dependence comparable with patients without viral infections (p >.05).

CONCLUSIONS

There is a significant prevalence (22-49%) of occult active herpes family viruses in chronic critically ill surgical patients. The clinical significance of these viral infections is unknown, although CMV+ patients have significantly higher morbidity rates than CMV- patients. Several factors suggest pathogenicity, but further study is needed to define causality.

Prediction of prolonged ventilatory support in blunt thoracic trauma patients

OBJECTIVE

To identify predictors of prolonged (>7 days) mechanical ventilation (MV) in patients with blunt thoracic trauma.

DESIGN

Prospective analysis of consecutive patients.

SETTING

Adult intensive care unit (ICU) in a teaching, tertiary-care hospital.

PATIENTS AND PARTICIPANTS

Sixty-nine patients (53 men, 16 women) with thoracic trauma having a median age of 35 (range 17-85) years and a median injury severity score (ISS) of 29 (range 14-41) were enrolled in the present study. Associated injuries included head-neck (77%), extremities (72%), external (67%), abdomen-pelvis (67%), and face (55%).

INTERVENTIONS

Patient surveillance and data collection.

MEASUREMENTS AND RESULTS

Thirty-three (48%) of the 69 patients required prolonged ventilatory support, ranging in duration from 8 to 38 (median 18) days. Logistic regression analysis revealed that advancing age (odds ratio=1.04, p=0.04), severity of head injury (odds ratio=1.92, p=0.008), and bilateral thoracic injuries (odds ratio=12.80, p<0.0001) were significant and independent predictors of long-lasting MV. In contrast, gender, injuries affecting the other body regions (face, abdomen-pelvis, extremities, and external), laparotomy in patients with abdominal injury, or PaO(2)/FIO(2) on admission in the ICU, were unrelated to prolonged MV.

CONCLUSIONS

In thoracic trauma patients admitted in the ICU, prolonged mechanical ventilation was primarily determined by presence of bilateral chest injuries, age, and degree of neurotrauma. This information may help in planning the long-term care of such patients.