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Study Objective To assess the safety of mechanical ventilation and effectiveness of extrinsic positive end-expiratory pressure (PEEP) (PEEPe) in improving peripheral oxygen saturation (SpO2) during direct microlaryngeal laser surgery; to assess the incidence, amount, and nature (dynamic hyperinflation or airflow obstruction) of ensuing intrinsic PEEP (PEEPi); and to find a surrogate PEEPi indicator. Design Quasiexperimental. Setting S. Raffaele Hospital (Milano), November 2009 to December 2010. Patients Fifty-two adults scheduled for direct microlaryngeal laser surgery. Exclusion criterion is pregnancy. Interventions Twenty-one percent O2 mechanical ventilation through 4.5- to 5.5-mm internal diameter endotracheal tubes; in 29 patients, after measurement of PEEPi, an identical amount of PEEPe was added; and PEEPi. Measurements SpO2, peak (Pawpeak) and plateau (Pawplateau) airway pressure, and end-expiratory carbon dioxide were measured every 5 minutes. Respiratory compliance (Crs) was computed. PEEPi was measured (end-expiratory occlusion method). Main Results PEEPi ≥ 5 cm H2O occurred in 14 patients (27%) after intubation, in 16 (30%) at the beginning, and in 14 (27.3%) at the end of surgery. Thirty-one patients (59.4%) exhibited PEEPi ≥ 5 cm H2O on at least 1 time point. PEEPi at the beginning of surgery was positively correlated with Pawplateau, Crs, tidal volume, and body mass index. Body mass index was the only predictor for the occurrence of PEEPi ≥ 5 cm H2O. At the beginning of surgery, the Pawplateau receiver operating characteristic curve predicting PEEPi ≥ 5 cm H2O had area under the receiver operating characteristic curve of 0.85; best cutoff value of 15.5 cm H2O (sensitivity, 88.9%; specificity, 75%; correctly classified cases, 86.1%). When PEEPe was applied, in 23 cases (82.1%), total PEEP equaled PEEPe+ PEEPi; in 3 (10.7%), it was lower; and in 2 (7.1%), it was higher. Application of PEEPe increased SpO2 (P<.05) and Crs (P<.05). Conclusions During vent

Rationale: We developed an innovative, minimally invasive, highly efficient extracorporeal CO2 removal (ECCO2R) technique called respiratory electrodialysis (R-ED). Objectives: To evaluate the efficacy of R-ED in controlling ventilation compared with conventional ECCO2R technology. Methods: Five mechanically ventilated swine were connected to a custom-made circuit optimized for R-ED, consisting of a hemofilter, a membrane lung, and an electrodialysis cell. Electrodialysis regionally modulates blood electrolyte concentration to convert bicarbonate to CO2 before entering the membrane lung, enhancing membrane lung CO2 extraction. All animals underwent three repeated experimental sequences, consisting of four steps: baseline (1 h), conventionalECCO2R(2 h), R-ED (2 h), and finalNOECCO2R (1 h). Blood and gas flow were 250 ml/min and 10 L/min, respectively. Tidal volume was set at 8 ml/kg, and respiratory rate was adjusted to maintain arterial PCO2 at 50 mm Hg. Measurements and Main Results: During R-ED, chloride andH1 concentration increased in blood entering the membrane lung, almost doubling CO2 extraction compared with ECCO2R (11266 vs. 6465 ml/min, P,0.001). Compared with baseline, R-ED and ECCO2R reduced minute ventilation by 50% and 27%, respectively. Systemic arterial gas analyses remained stable during the experimental phases. No major complication occurred, but there was an increase in creatinine level. Conclusions: In this first in vivo application, we proved electrodialysis feasible and effective in increasingmembrane lung CO2 extraction. R-ED was more effective than conventional ECCO2R technology in controlling ventilation. Further studies are warranted to assess the safety profile of R-ED, especially regarding kidney function.

Background: Auto-positive end-expiratory pressure (auto-PEEP) may substantially increase the inspiratory effort during assisted mechanical ventilation. Purpose of this study was to assess whether the electrical activity of the diaphragm (EAdi) signal can be reliably used to estimate auto-PEEP in patients undergoing pressure support ventilation and neurally adjusted ventilatory assist (NAVA) and whether NAVA was beneficial in comparison with pressure support ventilation in patients affected by auto-PEEP. Methods: In 10 patients with a clinical suspicion of auto-PEEP, the authors simultaneously recorded EAdi, airway, esophageal pressure, and flow during pressure support and NAVA, whereas external PEEP was increased from 2 to 14 cm H2O. Tracings were analyzed to measure apparent "dynamic" auto-PEEP (decrease in esophageal pressure to generate inspiratory flow), auto-EAdi (EAdi value at the onset of inspiratory flow), and IDEAdi (inspiratory delay between the onset of EAdi and the inspiratory flow). Results: The pressure necessary to overcome auto-PEEP, auto-EAdi, and IDEAdi was significantly lower in NAVA as compared with pressure support ventilation, decreased with increase in external PEEP, although the effect of external PEEP was less pronounced in NAVA. Both auto-EAdi and IDEAdi were tightly correlated with auto-PEEP (r2 = 0.94 and r2 = 0.75, respectively). In the presence of auto-PEEP at lower external PEEP levels, NAVA was characterized by a characteristic shape of the airway pressure. Conclusions: In patients with auto-PEEP, NAVA, compared with pressure support ventilation, led to a decrease in the pressure necessary to overcome auto-PEEP, which could be reliably monitored by the electrical activity of the diaphragm before inspiratory flow onset (auto-EAdi)

Objective: It is commonly assumed that lung volume at zero end-expiratory pressure (functional residual capacity) is not affected by positive end-expiratory pressure (PEEP) even in presence of alveolar recruitment, and it is often ignored when measuring lung recruitment by pressure-volume curves. Aim of the study was to investigate the effect of PEEP on functional residual capacity, and quantify the error of considering equal functional residual capacity in measuring alveolar recruitment. Design: Interventional human study. Setting: A 10-bed general intensive care unit in a university hospital. PATIENTS: Ten sedated, curarized, mechanically ventilated acute respiratory distress syndrome patients. Interventions: Three levels of PEEP (5, 10, and 15 cm H2O), were randomly applied, for 1 hr each. Measurements and Main results: At each PEEP we obtained a pressure-volume curve, the volume expired from PEEP to zero pressure (PEEP related lung volume) and functional residual capacity by helium dilution method. Functional residual capacity increased at increasing PEEP levels. Functional residual capacity was 507 ± 292, 607 ± 311, and 681 ± 312 ml (p <.05), respectively, at PEEP 5, 10, and 15 cm H2O. Pressure-volume curves were aligned starting from PEEP related lung volume (relative volume method) or from end-expiratory lung volume at PEEP (absolute volume method). Recruitment was measured as vertical distance of pressure-volume curves at 20 cm H2O airway pressure. The relative volume method led to underestimation of recruitment (43 ± 28% and 35 ± 18 %, respectively, at PEEP 10 and 15). Conclusions: Functional residual capacity is affected by PEEP. Ignoring this effect leads to relevant underestimation of alveolar recruitment as measure by pressure-volume curve displacement.

OBJECTIVE: Pentraxin 3 is a fluid phase receptor involved in innate immunity. It belongs to the Pentraxins family, as C-reactive protein does. Pentraxin 3 is produced by a variety of tissue cells, whereas only the liver produces C-reactive protein. Pentraxin 3 plays a unique role in the regulation of inflammation. Acute lung injury and acute respiratory distress syndrome are characterized by an important inflammatory reaction. We investigated the role of pentraxin 3 as a marker of severity and outcome predictor of acute lung injury and acute respiratory distress syndrome. DESIGN: We measured circulating pentraxin 3 and C-reactive protein levels within 24 hrs from intubation (day 1), after 24 hrs from the first sample, then every 3 days for the first month and then once a week, until discharge from the intensive care unit. Pentraxin 3 was also measured in bronchoalveolar lavages, performed when clinically indicated. SETTING: One university medical center general intensive care unit. PATIENTS: The study included 21 patients affected by acute lung injury and acute respiratory distress syndrome (1994 Consensus Conference criteria). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Pentraxin 3 plasma levels were high with a peak on the first day (median 71.05 ng/mL, interquartile range 52.37-117.38 ng/mL, normal values <2 ng/mL), declining thereafter. C-reactive protein peaked later and remained at relatively high values. Out of several day 1 parameters, pentraxin 3 was the only significant difference between survivors and nonsurvivors. Pentraxin 3 levels were positively correlated with lung injury score values (p < 0.001) and number of organ failures (p < 0.001). Pentraxin 3 was present in bronchoalveolar lavages fluids (5.03 ng/mL, interquartile range 1.52-8.48 ng/mL) and bronchoalveolar lavages positive to bacterial culture were associated with significantly higher pentraxin 3 values (p < 0.05). CONCLUSIONS: The results presented here show that pentraxin 3 is elevat

Objective: We measured pulmonary edema by thermal indocyanine green-dye double-dilution technique and quantitative computed tomography (CT) in patients with acute respiratory distress syndrome and compared the two techniques. Design and Setting: Prospective human study in a university hospital. Patients: Fourteen mechanically ventilated patients with acute respiratory distress syndrome (nine primary; nine with intubation <7 days). Interventions: All patients underwent a spiral CT of the thorax. We measured pulmonary thermal volume (PTV) and its components, extravascular lung water and pulmonary blood volume, with an integrated fiberoptic monitoring system (COLD Z-021). Measurements and Results: PTV was tightly correlated with lung weight (LW) measured by CT (PTV = 0.6875 * LWCT + 292.77; correlation coefficient = 0.91; p < .0001; bias -11 ± 8 %). Neither etiology of acute respiratory distress syndrome (primary vs. secondary) nor days of intubation affected the accuracy of thermal dye dilution in comparison with CT. There was no correlation between the extravascular lung water (12.3 ± 3.4 mL/kg) and CT distribution of lung tissue compartments. Extravascular lung water and pulmonary blood volume showed good reproducibility in 32 pairs of thermal dye dilution measurements. Conclusions: Measurements of lung edema by thermal indocyanine green-dye double-dilution method show good correlation with those by quantitative computed tomography and good reproducibility in patients with acute respiratory distress syndrome. Copyright © 2005 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins