The efficacy of venovenous extracorporeal membrane oxygenation (ECMO) in patients with severe acute respiratory distress syndrome (ARDS) remains controversial.
In an international clinical trial, we ...randomly assigned patients with very severe ARDS, as indicated by one of three criteria - a ratio of partial pressure of arterial oxygen (Pao
) to the fraction of inspired oxygen (Fio
) of less than 50 mm Hg for more than 3 hours; a Pao
:Fio
of less than 80 mm Hg for more than 6 hours; or an arterial blood pH of less than 7.25 with a partial pressure of arterial carbon dioxide of at least 60 mm Hg for more than 6 hours - to receive immediate venovenous ECMO (ECMO group) or continued conventional treatment (control group). Crossover to ECMO was possible for patients in the control group who had refractory hypoxemia. The primary end point was mortality at 60 days.
At 60 days, 44 of 124 patients (35%) in the ECMO group and 57 of 125 (46%) in the control group had died (relative risk, 0.76; 95% confidence interval CI, 0.55 to 1.04; P=0.09). Crossover to ECMO occurred a mean (±SD) of 6.5±9.7 days after randomization in 35 patients (28%) in the control group, with 20 of these patients (57%) dying. The frequency of complications did not differ significantly between groups, except that there were more bleeding events leading to transfusion in the ECMO group than in the control group (in 46% vs. 28% of patients; absolute risk difference, 18 percentage points; 95% CI, 6 to 30) as well as more cases of severe thrombocytopenia (in 27% vs. 16%; absolute risk difference, 11 percentage points; 95% CI, 0 to 21) and fewer cases of ischemic stroke (in no patients vs. 5%; absolute risk difference, -5 percentage points; 95% CI, -10 to -2).
Among patients with very severe ARDS, 60-day mortality was not significantly lower with ECMO than with a strategy of conventional mechanical ventilation that included ECMO as rescue therapy. (Funded by the Direction de la Recherche Clinique et du Développement and the French Ministry of Health; EOLIA ClinicalTrials.gov number, NCT01470703 .).
Background
This systematic review and meta-analysis summarizes the safety and efficacy of high flow nasal cannula (HFNC) in patients with acute hypoxemic respiratory failure.
Methods
We performed a ...comprehensive search of MEDLINE, EMBASE, and Web of Science. We identified randomized controlled trials that compared HFNC to conventional oxygen therapy. We pooled data and report summary estimates of effect using relative risk for dichotomous outcomes and mean difference or standardized mean difference for continuous outcomes, with 95% confidence intervals. We assessed risk of bias of included studies using the Cochrane tool and certainty in pooled effect estimates using GRADE methods.
Results
We included 9 RCTs (
n
= 2093 patients). We found no difference in mortality in patients treated with HFNC (relative risk RR 0.94, 95% confidence interval CI 0.67–1.31, moderate certainty) compared to conventional oxygen therapy. We found a decreased risk of requiring intubation (RR 0.85, 95% CI 0.74–0.99) or escalation of oxygen therapy (defined as crossover to HFNC in the control group, or initiation of non-invasive ventilation or invasive mechanical ventilation in either group) favouring HFNC-treated patients (RR 0.71, 95% CI 0.51–0.98), although certainty in both outcomes was low due to imprecision and issues related to risk of bias. HFNC had no effect on intensive care unit length of stay (mean difference MD 1.38 days more, 95% CI 0.90 days fewer to 3.66 days more, low certainty), hospital length of stay (MD 0.85 days fewer, 95% CI 2.07 days fewer to 0.37 days more, moderate certainty), patient reported comfort (SMD 0.12 lower, 95% CI 0.61 lower to 0.37 higher, very low certainty) or patient reported dyspnea (standardized mean difference SMD 0.16 lower, 95% CI 1.10 lower to 1.42 higher, low certainty). Complications of treatment were variably reported amongst included studies, but little harm was associated with HFNC use.
Conclusion
In patients with acute hypoxemic respiratory failure, HFNC may decrease the need for tracheal intubation without impacting mortality.
Enhanced coal bed methane recovery (ECBM) consists in injecting carbon dioxide in coal bed methane reservoirs in order to facilitate the recovery of the methane. The injected carbon dioxide gets ...adsorbed at the surface of the coal pores, which causes the coal to swell. This swelling in confined conditions leads to a closure of the coal reservoir cleat system, which hinders further injection. In this work we provide a comprehensive framework to calculate the macroscopic strains induced by adsorption in a porous medium from the molecular level. Using a thermodynamic approach we extend the realm of poromechanics to surface energy and surface stress. We then focus on how the surface stress is modified by adsorption and on how to estimate adsorption behavior with molecular simulations. The developed framework is here applied to the specific case of the swelling of CO2-injected coal, although it is relevant to any problem in which adsorption in a porous medium causes strains.
Summary
Background Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are acute mucocutaneous reactions associated with poor prognosis. The treatment is mainly symptomatic, based on ...supportive care. Until now, several curative treatments have been proposed without evidence of effectiveness.
Objectives To evaluate the effect of ciclosporin on SJS and TEN after a short series had suggested a benefit.
Methods We conducted an open, phase II trial to determine the safety and possible benefit of ciclosporin. Among the 45 consecutive patients admitted for SJS/TEN from March 2005 to September 2007, 29 fulfilled inclusion criteria. Ciclosporin was administered orally (3 mg kg−1 daily for 10 days) and tapered over a month. Clinical and biological evaluations were performed sequentially. Predicted death rate was estimated with a validated prognostic score (SCORTEN).
Results Twenty‐nine patients were included at a mean ± SD of 2·8 ± 1·8 days after onset. The final diagnosis was SJS (n = 10), SJS/TEN overlap (n = 12) and TEN (n = 7). One month of treatment was completed in 26. Ciclosporin was stopped after more than 10 days in three cases for side‐effects including posterior leucoencephalopathy (n = 1), neutropenia (n = 1) and nosocomial pneumopathy (n = 1). Ciclosporin dosage was tapered earlier than scheduled in two cases for alteration in renal function. The prognostic score predicted 2·75 deaths; none occurred (P = 0·1). Mean epidermal detachment remained stable in 18 of 29 cases (62%). The mean ± SD hospital stay was 16·2 ± 9·1 days.
Conclusions Both the death rate and the progression of detachment seemed lower than expected, suggesting a possible usefulness of ciclosporin in SJS and TEN that needs to be confirmed.
Poromechanics of microporous media Brochard, L.; Vandamme, M.; Pellenq, R.J.-M.
Journal of the mechanics and physics of solids,
April 2012, 2012-04-00, 20120401, 2012-04, Volume:
60, Issue:
4
Journal Article
Peer reviewed
Open access
Microporous media, i.e., porous media made of pores with a nanometer size, are important for a variety of applications, for instance for sequestration of carbon dioxide in coal, or for storage of ...hydrogen in metal-organic frameworks. In a pore of nanometer size, fluid molecules are not in their bulk state anymore since they interact with the atoms of the solid: they are said to be in an adsorbed state. For such microporous media, conventional poromechanics breaks down.
In this work we derive poroelastic constitutive equations which are valid for a generic porous medium, i.e., even for a porous medium with pores of nanometer size. The complete determination of the poromechanical behavior of a microporous medium requires knowing how the amount of fluid adsorbed depends on both the fluid bulk pressure and the strain of the medium. The derived constitutive equations are validated with the help of molecular simulations on one-dimensional microporous media. Even when a microporous medium behaves linearly in the absence of any fluid (i.e., its bulk modulus does not depend on strain), we show that fluid adsorption can induce non-linear behavior (i.e., its drained bulk modulus can then depend significantly on strain). We also show that adsorption can lead to an apparent Biot coefficient of the microporous medium greater than unity or smaller than zero.
The poromechanical response of a microporous medium to adsorption significantly depends on the pore size distribution. Indeed, the commensurability (i.e., the ratio of the size of the pores to that of the fluid molecules) proves to play a major role. For a one-dimensional model of micropores with a variety of pore sizes, molecular simulations show that the amount of adsorbed fluid depends linearly on the strain of the medium. We derive linearized constitutive equations which are valid when such a linear dependence of the adsorbed amount of fluid on the strain is observed.
As an application, the case of methane and coal is considered. Molecular simulations of an adsorption of methane on a microporous realistic model for coal are performed with a flexible solid skeleton. The applicability of the set of linearized constitutive equations to this case is discussed and the results are shown to be consistent with swelling data measured during a classical adsorption experiment.
► We derive poromechanical equations that are valid even for microporous media. ► Adsorption and strain in microporous media can be coupled. ► Adsorption of fluid can induce non-linear behavior of the medium. ► The poromechanical response of a microporous medium to adsorption significantly depends on the pore size distribution. ► The derived equations are relevant for adsorption of methane in coal.
Pathophysiological changes due to obesity may complicate mechanical ventilation during general anaesthesia. The ideal ventilation strategy is expected to optimize gas exchange and pulmonary mechanics ...and to reduce the risk of respiratory complications.
Systematic search (databases, bibliographies, to March 2012, all languages) was performed for randomized trials testing intraoperative ventilation strategies in obese patients (BMI ≥30 kg m−2), and reporting on gas exchange, pulmonary mechanics, or pulmonary complications. Meta-analyses were performed when data from at least three studies or 100 patients could be combined.
Thirteen studies (505 obese surgical patients) reported on a variety of ventilation strategies: pressure- or volume-controlled ventilation (PCV, VCV), various tidal volumes, and different PEEP or recruitment manoeuvres (RM), and combinations thereof. Definitions and reporting of endpoints were inconsistent. In five trials (182 patients), RM added to PEEP compared with PEEP alone improved intraoperative PaO2/FIO2 ratio weighted mean difference (WMD), 16.2 kPa; 95% confidence interval (CI), 8.0–24.4 and increased respiratory system compliance (WMD, 14 ml cm H2O−1; 95% CI, 8–20). Arterial pressure remained unchanged. In four trials (100 patients) comparing PCV with VCV, there was no difference in PaO2/FIO2 ratio, tidal volume, or arterial pressure. Comparison of further ventilation strategies or combination of other outcomes was not feasible. Data on postoperative complications were seldom reported.
The ideal intraoperative ventilation strategy in obese patients remains obscure. There is some evidence that RM added to PEEP compared with PEEP alone improves intraoperative oxygenation and compliance without adverse effects. There is no evidence of any difference between PCV and VCV.
Purpose
Neurally adjusted ventilatory assist (NAVA) is a ventilatory mode that tailors the level of assistance delivered by the ventilator to the electromyographic activity of the diaphragm. The ...objective of this study was to compare NAVA and pressure support ventilation (PSV) in the early phase of weaning from mechanical ventilation.
Methods
A multicentre randomized controlled trial of 128 intubated adults recovering from acute respiratory failure was conducted in 11 intensive care units. Patients were randomly assigned to NAVA or PSV. The primary outcome was the probability of remaining in a partial ventilatory mode (either NAVA or PSV) throughout the first 48 h without any return to assist-control ventilation. Secondary outcomes included asynchrony index, ventilator-free days and mortality.
Results
In the NAVA and PSV groups respectively, the proportion of patients remaining in partial ventilatory mode throughout the first 48 h was 67.2 vs. 63.3 % (
P
= 0.66), the asynchrony index was 14.7 vs. 26.7 % (
P
< 0.001), the ventilator-free days at day 7 were 1.0 day 1.0–4.0 vs. 0.0 days 0.0–1.0 (
P
< 0.01), the ventilator-free days at day 28 were 21 days 4–25 vs. 17 days 0–23 (
P
= 0.12), the day-28 mortality rate was 15.0 vs. 22.7 % (
P
= 0.21) and the rate of use of post-extubation noninvasive mechanical ventilation was 43.5 vs. 66.6 % (
P
< 0.01).
Conclusions
NAVA is safe and feasible over a prolonged period of time but does not increase the probability of remaining in a partial ventilatory mode. However, NAVA decreases patient–ventilator asynchrony and is associated with less frequent application of post-extubation noninvasive mechanical ventilation.
Trial Registration.
clinicaltrials.gov Identifier: NCT02018666.
Mechanical ventilation is the most widely used supportive technique in intensive care units. Several forms of external support for respiration have long been described to assist the failing ...ventilatory pump, and access to lower airways through tracheostomy or endotracheal tubes had constituted a major advance in the management of patients with respiratory distress. More recently, however, new "noninvasive" ventilation (NIV) techniques, using patient/ventilator interfaces in the form of facial masks, have been designed. The reasons for promoting NIV include a better understanding of the role of ventilatory pump failure in the indications for mechanical ventilation, the development of ventilatory modalities able to work in synchrony with the patient, and the extensive recognition of complications associated with endotracheal intubation and standard mechanical ventilation. NIV has been used primarily for patients with acute hypercapnic ventilatory failure, and especially for acute exacerbation of chronic obstructive pulmonary disease. In this population, the use of NIV is associated with a marked reduction in the need for endotracheal intubation, a decrease in complication rate, a reduced duration of hospital stay and a substantial reduction in hospital mortality. Similar benefits have also been demonstrated in patients with asphyxic forms of acute cardiogenic pulmonary oedema. In patients with primarily hypoxemic forms of respiratory failure, the level of success of NIV is more variable, but major benefits have also been demonstrated in selected populations with no contraindications such as multiple organ failure, loss of consciousness or haemodynamic instability. One important factor in success seems to be the early delivery of noninvasive ventilation during the course of respiratory failure. Noninvasive ventilation allows many of the complications associated with mechanical ventilation to be avoided, especially the occurrence of nosocomial infections. The current use of noninvasive ventilation is growing up, and is becoming a major therapeutic tool in the intensive care unit.
Purpose
Lung volumes, especially functional residual capacity (FRC), are decreased in acute respiratory distress syndrome (ARDS). Positive end-expiratory pressure (PEEP) contributes to increased ...end-expiratory lung volume (EELV) and to improved oxygenation, but differentiating recruitment of previously nonaerated lung units from distension of previously open lung units remains difficult. This study evaluated simple methods derived from bedside EELV measurements to assess PEEP-induced lung recruitment while monitoring strain.
Methods
Prospective multicenter study in 30 mechanically ventilated patients with ARDS in five university hospital ICUs. Two PEEP levels were studied, each for 45 min, and EELV (nitrogen washout/washin technique) was measured at both levels, with the difference (Δ) reflecting PEEP-induced lung volume changes. Alveolar recruitment was measured using pressure-volume (PV) curves. High and low recruiters were separated based on median recruitment at high PEEP. Minimum predicted increase in lung volume computed as the product of ΔPEEP by static compliance was subtracted from ΔEELV as an independent estimate of recruitment. Estimated and measured recruitments were compared. Strain induced by PEEP was also calculated from the same measurements.
Results
FRC was 31 ± 11% of predicted. Median 25th–75th percentiles PEEP-induced recruitment was 272 187–355 mL. Estimated recruitment correlated with recruited volume measured on PV curves (ρ = 0.68), with a slope close to identity. The ΔEELV/FRC ratio differentiated high from low recruiters (110 76–135 vs. 55 23–70%,
p
= 0.001). Strain increase due to PEEP was larger in high recruiters (
p
= 0.002).
Conclusion
PEEP-induced recruitment and strain can be assessed at the bedside using EELV measurement. We describe two bedside methods for predicting low or high alveolar recruitment during ARDS.
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