Demet Sulemanji

The acute respiratory distress syndrome: incidence and mortality, has it changed?

Purpose of reviewThe purpose of this review is to examine and discuss the incidence and outcome of patients with the acute respiratory distress syndrome (ARDS). This is a challenging task, as there is no specific clinical sign or diagnostic test that accurately identifies and adequately defines this syndrome. Recent findingsThis review will focus on published epidemiological studies reporting population-based incidence of ARDS, as defined by the American-European Consensus Conference criteria. In addition, the current outcome figures for ARDS patients reported in observational and randomized controlled trials will be reviewed. The focus will be on studies published since 2000, when the ARDSnet study on protective mechanical ventilation was published, although particular emphasis will be on those articles published in the last 24 months. SummaryOn the basis of current evidence, and despite the order of magnitude of reported European and USA incidence figures, it seems that the incidence and overall mortality of ARDS has not changed substantially since the original ARDSnet study. The current mortality of adult ARDS is still greater than 40%.

Open Lung Approach for the Acute Respiratory Distress Syndrome: A Pilot, Randomized Controlled Trial*

Objective:The open lung approach is a mechanical ventilation strategy involving lung recruitment and a decremental positive end-expiratory pressure trial. We compared the Acute Respiratory Distress Syndrome network protocol using low levels of positive end-expiratory pressure with open lung approach resulting in moderate to high levels of positive end-expiratory pressure for the management of established moderate/severe acute respiratory distress syndrome. Design:A prospective, multicenter, pilot, randomized controlled trial. Setting:A network of 20 multidisciplinary ICUs. Patients:Patients meeting the American-European Consensus Conference definition for acute respiratory distress syndrome were considered for the study. Interventions:At 12-36 hours after acute respiratory distress syndrome onset, patients were assessed under standardized ventilator settings (FIO2≥0.5, positive end-expiratory pressure ≥10 cm H2O). If Pao2/FIO2 ratio remained less than or equal to 200 mm Hg, patients were randomized to open lung approach or Acute Respiratory Distress Syndrome network protocol. All patients were ventilated with a tidal volume of 4 to 8 ml/kg predicted body weight. Measurements and Main Results:From 1,874 screened patients with acute respiratory distress syndrome, 200 were randomized: 99 to open lung approach and 101 to Acute Respiratory Distress Syndrome network protocol. Main outcome measures were 60-day and ICU mortalities, and ventilator-free days. Mortality at day-60 (29% open lung approach vs. 33% Acute Respiratory Distress Syndrome Network protocol, p = 0.18, log rank test), ICU mortality (25% open lung approach vs. 30% Acute Respiratory Distress Syndrome network protocol, p = 0.53 Fisher’s exact test), and ventilator-free days (8 [0-20] open lung approach vs. 7 [0-20] d Acute Respiratory Distress Syndrome network protocol, p = 0.53 Wilcoxon rank test) were not significantly different. Airway driving pressure (plateau pressure - positive end-expiratory pressure) and PaO2/FIO2 improved significantly at 24, 48 and 72 hours in patients in open lung approach compared with patients in Acute Respiratory Distress Syndrome network protocol. Barotrauma rate was similar in both groups. Conclusions:In patients with established acute respiratory distress syndrome, open lung approach improved oxygenation and driving pressure, without detrimental effects on mortality, ventilator-free days, or barotrauma. This pilot study supports the need for a large, multicenter trial using recruitment maneuvers and a decremental positive end-expiratory pressure trial in persistent acute respiratory distress syndrome.

Adaptive support ventilation: an appropriate mechanical ventilation strategy for acute respiratory distress syndrome?

Background:Adaptive support ventilation (ASV) allows the clinician to set a maximum plateau pressure (PP) and automatically adjusts tidal volume to keep PP below the set maximum. Methods:ASV was compared to a fixed tidal volume of 6 ml/kg. ASV determined the respiratory rate and tidal volume based on its algorithms. Maximum airway pressure limit was 28 cm H2O in ASV. Six sets of lung mechanics were simulated for two ideal body weights: 60 kg, Group I; 80 kg, Group II. Positive end expiratory pressure was 8, 12, and 16 cm H2O, and target minute volume 120%, 150%, and 200% of predicted minute volume. Results:ASV “sacrificed” tidal volume and minute ventilation to maintain PP in 9 (17%) of 54 scenarios in Group I and 20 (37%) of 54 scenarios in Group II. In Group I, the number of scenarios with PP of 28 cm H2O or more was 14 for ASV (26%) and 19 for 6 ml/kg (35%). In these scenarios, mean PP were ASV 28.8 ± 0.86 cm H2O (min 28, max 30.3) and 6 ml/kg 33.01 ± 3.48 cm H2O (min 28, max 37.8) (P = 0.000). In group II, the number of scenarios PP of 28 cm H2O or more was 10 for ASV (19%) and 21 for 6 ml/kg (39%). In these cases, mean PP values were ASV 28.78 ± 0.54 cm H2O (min 28, max 29.6) and 6 ml/kg 32.66 ± 3.37 cm H2O (min 28.2, max 38.2) (P = 0.000). Conclusion:In a lung model with varying mechanics, ASV is better able to prevent the potential damaging effects of excessive PP (greater than 28 cm H2O) than a fixed tidal volume of 6 ml/kg by automatically adjusting airway pressure, resulting in a decreased tidal volume.

Evaluation of an Automated Endotracheal Tube Cuff Controller During Simulated Mechanical Ventilation

BACKGROUND: Maintaining endotracheal tube cuff pressure within a narrow range is an important factor in patient care. The goal of this study was to evaluate the IntelliCuff against the manual technique for maintaining cuff pressure during simulated mechanical ventilation with and without movement. METHODS: The IntelliCuff was compared to the manual technique of a manometer and syringe. Two independent studies were performed during mechanical ventilation: part 1, a 2-h trial incorporating continuous mannikin head movement; and part 2, an 8-h trial using a stationary trachea model. We set cuff pressure to 25 cm H2O, PEEP to 10 cm H2O, and peak inspiratory pressures to 20, 30, and 40 cm H2O. Clinical importance was defined as both statistically significant (P < .05) and clinically significant (pressure change [Δ] > 10%). RESULTS: In part 1, the change in cuff pressure from before to after ventilation was clinically important for the manual technique (P < .001, Δ = −39.6%) but not for the IntelliCuff (P = .02, Δ = 3.5%). In part 2, the change in cuff pressure from before to after ventilation was clinically important for the manual technique (P = .004, Δ = −14.39%) but not for the IntelliCuff (P = .20, Δ = 5.65%). CONCLUSIONS: There was a clinically important drop in manually set cuff pressure during simulated mechanical ventilation in a stationary model and an even larger drop with movement, but this was significantly reduced by the IntelliCuff in both scenarios. Additionally, we observed that cuff pressure varied directly with inspiratory airway pressure for both techniques, leading to elevated average cuff pressures.

Kinetics of plasma biomarkers of inflammation and lung injury in surgical patients with or without postoperative pulmonary complications.

BACKGROUND Postoperative pulmonary complications (PPCs) are common after major abdominal surgery. The kinetics of plasma biomarkers could improve identification of patients developing PPCs, but the kinetics may depend on intraoperative ventilator settings. OBJECTIVE To test whether the kinetics of plasma biomarkers are capable of identifying patients who will develop PPCs, and whether the kinetics depend on the intraoperative level of positive end-expiratory pressure (PEEP). DESIGN A preplanned substudy of a randomised controlled trial. SETTING Operation room of five centres. PATIENTS Two hundred and forty-two adult patients scheduled for abdominal surgery at risk of developing PPCs. INTERVENTIONS High (12 cmH2O) versus low (⩽2 cmH2O) levels of PEEP. MAIN OUTCOME MEASURES Individual PPCs were combined as a composite endpoint. Plasma samples were collected before surgery, directly after surgery and on the fifth postoperative day. The levels of the following were measured: tumour necrosis factor (TNF)-&agr;, interleukin (IL)-6 and IL-8, the soluble form of the Receptor for Advanced Glycation End–products (sRAGE), Surfactant Protein (SP)-D, Clara Cell protein (CC)-16 and Krebs von den Lungen 6 (KL6). RESULTS Blood sampling was complete in 242 patients: 120 patients in the high PEEP group and 122 patients in the low PEEP group. Increases in plasma levels of TNF- IL-6, IL-8 and CC-16, and a decrease in plasma levels of SP-D were greater in patients who developed PPCs; however, the area under the receiver operating characteristic curve was low for all biomarkers. CC-16 was the only biomarker whose level increased more in patients who had received high levels of PEEP. CONCLUSION In patients undergoing abdominal surgery and at risk of developing PPCs, plasma levels of biomarkers for inflammation or lung injury showed distinct kinetics with development of PPCs, but none of the biomarkers showed sufficient prognostic value. The use of high levels of PEEP was associated with increased levels of CC-16, suggesting lung overdistension. TRIAL REGISTRATION The PROVHILO trial, including this substudy, was registered at clinicaltrials.gov (NCT01441791).

Effects of anesthesia on linguistic skills: can anesthesia cause language switches?

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New insights into the effect of rapid transfusion of fresh frozen plasma on ionized calcium

STUDY OBJECTIVES 1) To develop an in vitro system to simulate the kinetics of ionized calcium in mixed venous blood during rapid transfusion of fresh frozen plasma (FFP) and 2) to use the in vitro data to estimate the effect of the transfusion rate relative to cardiac output (CO) on ionized calcium. DESIGN Experimental study. SETTING Research laboratory of an academic hospital. MEASUREMENTS Citrated FFP was mixed with compatible heparinized whole blood at various volume ratios in vitro to simulate the mixed venous blood obtained at various flow ratios of FFP transfusion to the recipients venous system in vivo. Ionized calcium was measured after each mixture. MAIN RESULTS Mixing FFP and whole blood at volume ratios of 0:100, 5:95, 10:90, and 15:85 yielded ionized calcium levels (mean ± SD, mmol/L) of 1.23, 0.81 ± 0.02, 0.54 ± 0.08, and 0.34 ± 0.02, respectively. The 50% reduction in ionized calcium occurred at a volume ratio of 7:93. CONCLUSIONS An instantaneous 50% reduction in ionized calcium occurs in vitro at a proportion equivalent to a transfusion rate of FFP representing 7% of CO.

Respiratory System Mechanics During Low Versus High Positive End-Expiratory Pressure in Open Abdominal Surgery: A Substudy of PROVHILO Randomized Controlled Trial.

BACKGROUND: In the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications when compared to low PEEP (0–2 cm H2O) approach without recruitment breaths. However, effects of intraoperative PEEP on lung compliance remain poorly understood. We hypothesized that higher PEEP leads to a dominance of intratidal overdistension, whereas lower PEEP results in intratidal recruitment/derecruitment (R/D). To test our hypothesis, we used the volume-dependent elastance index %E2, a respiratory parameter that allows for noninvasive and radiation-free assessment of dominant overdistension and intratidal R/D. We compared the incidence of intratidal R/D, linear expansion, and overdistension by means of %E2 in a subset of the PROVHILO cohort. METHODS: In 36 patients from 2 participating centers of the PROVHILO trial, we calculated respiratory system elastance (E), resistance (R), and %E2, a surrogate parameter for intratidal overdistension (%E2 > 30%) and R/D (%E2 < 0%). To test the main hypothesis, we compared the incidence of intratidal overdistension (primary end point) and R/D in higher and lower PEEP groups, as measured by %E2. RESULTS: E was increased in the lower compared to higher PEEP group (18.6 [16…22] vs 13.4 [11.0…17.0] cm H2O·L−1; P < .01). %E2 was reduced in the lower PEEP group compared to higher PEEP (−15.4 [−28.0…6.5] vs 6.2 [−0.8…14.0] %; P < .05). Intratidal R/D was increased in the lower PEEP group (61% vs 22%; P = .037). The incidence of intratidal overdistension did not differ significantly between groups (6%). CONCLUSIONS: During mechanical ventilation with protective tidal volumes in patients undergoing open abdominal surgery, lung recruitment followed by PEEP of 12 cm H2O decreased the incidence of intratidal R/D and did not worsen overdistension, when compared to PEEP ⩽2 cm H2O.

A Unidirectional Breathing Pattern Improves Breathing Efficiency in Subjects With Severe COPD

BACKGROUND: Unidirectional breathing (UB), nose-in mouth-out (NMB) or vice versa, is thought to create PEEP, stabilize small airways, and increase expiratory flow and exhaled tidal volume (VT) in patients with expiratory obstructive disorders. However, the exact mechanism providing the benefits of UB remains unknown. Our hypothesis was that the benefits of UB are achieved mainly through reduction of upper airway dead space. METHODS: Sixteen stable COPD patients requiring oxygen use at home were enrolled in this prospective study at a tertiary health care center. A nasal mask and a mouthpiece were used, each having a removable one-way valve to direct the breathing pattern. Four experimentally defined patterns of spontaneous breathing, NMB, mouth-in nose-out (MNB), nose-in nose-out (NNB), and mouth-in mouth-out (MMB), were compared. Each breathing pattern lasted 5 min followed by a 5-min rest period. A NICO device continuously monitored respiratory parameters. The functional anatomical dead space volume (VD) and expired VT values were determined. Breathing efficiency (BE) was calculated as alveolar VT divided by expired volume. RESULTS: Functional anatomical VD was higher in bidirectional breathing (BB) (overall: 207.4 ± 7.9 mL; MMB: 232.5 ± 72.7 mL; NNB: 182.2 ± 75 mL) compared to UB (overall: 178.1 ± 87.2 mL; NMB: 176.9 ± 91.3 mL; MNB: 179.3 ± 83.2 mL) (P < .001). BE achieved with UB (overall: 76.2 ± 6.5%; NMB: 76.8 ± 6.8%; MNB: 75.6 ± 6.3%) was higher than that with BB (overall: 66.2 ± 0.09%; MMB: 64.3 ± 0.10%; NNB: 68.1 ± 0.08%) (P < .001). The difference in BE between UB and BB was more pronounced with small VT values (UB: 73.8 ± 0.08; BB: 49.4 ± 0.09) than with large VT values (UB: 77.3 ± 0.06; BB: 63.0 ± 0.07) (P < .001). CONCLUSIONS: Our data suggest that a reduction in functional anatomic VD may be the underlying mechanism for the benefits associated with UB in COPD patients. (ClinicalTrials.gov registration NCT00784004.)