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Purpose: Some patients presenting with acute respiratory failure and meeting the Berlin criteria for acute respiratory distress syndrome (ARDS) lack exposure to common risk factors (CRF). These so-called ARDS mimickers often lack histological diffuse alveolar damage. We aimed to describe such ARDS mimickers lacking CRF (ARDS CRF-) in comparison with others (ARDS CRF+).Methods: Retrospective study including all patients receiving invasive mechanical ventilation for ARDS admitted to the intensive care units (ICUs) of two tertiary care centers from January 2003 to December 2012.Results: The prevalence of ARDS CRF- was 7.5 % (95 % CI [5.5-9.5]; n = 50/665). On the basis of medical history, bronchoalveolar lavage fluid cytology, and chest CT scan patterns, four etiological categories were identified: immune (n = 18; 36 %), drug-induced (n = 13; 26 %), malignant (n = 7; 14 %), and idiopathic (n = 12; 24 %). Although the ARDS CRF- patients had a lower logistic organ dysfunction score (4 [3-8] vs. 10 [6-13]; p < 0.0001) and less often shock upon ICU admission (44 vs. 80 %; p < 0.0001) than their counterparts, their overall ICU mortality rate was very high (66 % [46-74]), and the absence of CRF remained associated with ICU mortality by multivariable logistic regression analysis (adjusted OR = 2.06; 95 % CI [1.02-4.18]; p = 0.044). Among ARDS CRF- patients, the presence of potentially reversible lung lesions with corticosteroids (aOR = 0.14; 95 % CI [0.03-0.62]) was associated with ICU survival.Conclusions: The absence of CRF among patients with ARDS is common and associated with a higher risk of mortality. For such atypical ARDS, a complete diagnostic workup, including bronchoalveolar lavage fluid cytology and chest CT scan patterns, should be performed to identify those patients who might benefit from specific therapies, including corticosteroids. [ABSTRACT FROM AUTHOR]

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/FiO 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. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the efficiency, safety and outcome of high flow nasal cannula oxygen (HFNC) in ICU patients with acute respiratory failure. Methods: Pilot prospective monocentric study. Thirty-eight patients were included. Baseline demographic and clinical data, as well as respiratory variables at baseline and various times after HFNC initiation during 48 h, were recorded. Arterial blood gases were measured before and after the use of HFNC. Noise and discomfort were monitored along with outcome and need for invasive mechanical ventilation. Results: HFNC significantly reduced the respiratory rate, heart rate, dyspnea score, supraclavicular retraction and thoracoabdominal asynchrony, and increased pulse oxymetry. These improvements were observed as early as 15 min after the beginning of HFNC for respiratory rate and pulse oxymetry. PaO and PaO/FiO increased significantly after 1 h HFNC in comparison with baseline (141 ± 106 vs. 95 ± 40 mmHg, p = 0.009 and 169 ± 108 vs. 102 ± 23, p = 0.036; respectively). These improvements lasted throughout the study period. HFNC was used for a mean duration of 2.8 days and a maximum of 7 days. It was never interrupted for intolerance. No nosocomial pneumonia occurred during HFNC. Nine patients required secondary invasive mechanical ventilation. Absence of a significant decrease in the respiratory rate, lower oxygenation and persistence of thoracoabdominal asynchrony after HFNC initiation were early indicators of HFNC failure. Conclusions: HFNC has a beneficial effect on clinical signs and oxygenation in ICU patients with acute respiratory failure. These favorable results constitute a prerequisite to launching a randomized controlled study to investigate whether HFNC reduces intubation in these patients. [ABSTRACT FROM AUTHOR]

Objective: The aims of the present study were 1) to evaluate a method for identification of "slowly" distensible compartments of the respiratory system (rs), which are characterized by long mechanical time constants (RC) and 2) to identify "slowly" distensible rs-compartments in mechanically ventilated patients.Design: Prospective study on a physical lung model.Setting: Intensive Care Unit, University Hospital, Tübingen.Patients and Participants: 19 patients with severe lung injury (acute respiratory distress syndrome, ARDS) and on 10 patients with mild lung injury.Measurements and Results: Positive end-expiratory pressure (PEEP)-increasing and -decreasing steps of about 5 cmH2O were applied and the breath-by-breath differences of inspiratory and expiratory volumes (delta V) were measured. The sequence of delta Vs were analyzed in terms of volume change in the "fast" compartment (Vfast), the "slow" compartment (Vslow), total change in lung volume (delta VL) and mechanical time constant of the slow compartment (RCslow). Thirty-eight measurements in a lung model revealed a good correlation between the preset Vslow/delta VL and Vslow/delta VL measured: r2 = 0.91. The Vslow/delta VL measured amounted to 0.94 +/- 0.15 of Vslow/delta VL in the lung model. RCslow measured was 0.92 +/- 0.43 of the RCslow reference. Starting from a PEEP level of 11 cmH2O PEEP-increasing and PEEP-decreasing steps were applied to the mechanically ventilated patients. Three out of ten patients with mild lung injury (30%) and 7/19 patients with ARDS (36.8%) revealed "slowly" distensible rs-compartments in a PEEP-increasing step, whereas 15/19 ARDS patients and 1/10 patients with mild lung injury showed "slowly" distensible rs-compartments in a PEEP-decreasing step (78.9% vs 10%, P < 0.002, chi-square test).Conclusions: The gas distribution properties of the respiratory system can be easily studied by a PEEP-step maneuver. The relative contribution of the "slow" units to the total increase of lung volume following a PEEP step could be adequately assessed. "Slowly" distensible rs-compartments could be detected in patients with severe and mild lung injury, however significantly more ARDS patients revealed "slow" rs-compartments in PEEP-decreasing steps. The influence of "slowly" distensible rs-compartments on pulmonary gas exchange is unknown and has yet to be studied. [ABSTRACT FROM AUTHOR]