Spontaneous breathing trial and post-extubation work of breathing in morbidly obese critically ill patients.

BACKGROUND: Predicting whether an obese critically ill patient can be successfully extubated may be specially challenging. Several weaning tests have been described but no physiological study has evaluated the weaning test that would best reflect the post-extubation inspiratory effort. METHODS: This was a physiological randomized crossover study in a medical and surgical single-center Intensive Care Unit, in patients with body mass index (BMI) >35 kg/m2 who were mechanically ventilated for more than 24 h and underwent a weaning test. After randomization, 17 patients were explored using five settings : pressure support ventilation (PSV) 7 and positive end-expiratory pressure (PEEP) 7 cmH2O; PSV 0 and PEEP 7cmH2O; PSV 7 and PEEP 0 cmH2O; PSV 0 and PEEP 0 cmH2O; and a T piece, and after extubation. To further minimize interaction between each setting, a period of baseline ventilation was performed between each step of the study. We hypothesized that the post-extubation work of breathing (WOB) would be similar to the T-tube WOB. RESULTS: Respiratory variables and esophageal and gastric pressure were recorded. Inspiratory muscle effort was calculated as the esophageal and trans-diaphragmatic pressure time products and WOB. Sixteen obese patients (BMI 44 kg/m2\u2009\ub1\u20098) were included and successfully extubated. Post-extubation inspiratory effort, calculated by WOB, was 1.56 J/L\u2009\ub1\u20090.50, not statistically different from the T piece (1.57 J/L\u2009\ub1\u20090.56) or PSV 0 and PEEP 0 cmH2O (1.58 J/L\u2009\ub1\u20090.57), whatever the index of inspiratory effort. The three tests that maintained pressure support statistically underestimated post-extubation inspiratory effort (WOB 0.69 J/L\u2009\ub1\u20090.31, 1.15 J/L\u2009\ub1\u20090.39 and 1.09 J/L\u2009\ub1\u20090.49, respectively, p\u2009<\u20090.001). Respiratory mechanics and arterial blood gases did not differ between the five tests and the post-extubation condition. CONCLUSIONS: In obese patients, inspiratory effort measured during weaning tests with either a T-piece or a PSV 0 and PEEP 0 was not different to post-extubation inspiratory effort. In contrast, weaning tests with positive pressure overestimated post-extubation inspiratory effort. TRIAL REGISTRATION: Clinical trial.gov (reference NCT01616901 ), 2012, June 4th.Background: Predicting whether an obese critically ill patient can be successfully extubated may be specially challenging. Several weaning tests have been described but no physiological study has evaluated the weaning test that would best reflect the post-extubation inspiratory effort. Methods: This was a physiological randomized crossover study in a medical and surgical single-center Intensive Care Unit, in patients with body mass index (BMI) >35 kg/m2 who were mechanically ventilated for more than 24 h and underwent a weaning test. After randomization, 17 patients were explored using five settings : pressure support ventilation (PSV) 7 and positive end-expiratory pressure (PEEP) 7 cmH2O; PSV 0 and PEEP 7cmH2O; PSV 7 and PEEP 0 cmH2O; PSV 0 and PEEP 0 cmH2O; and a T piece, and after extubation. To further minimize interaction between each setting, a period of baseline ventilation was performed between each step of the study. We hypothesized that the post-extubation work of breathing (WOB) would be similar to the T-tube WOB. Results: Respiratory variables and esophageal and gastric pressure were recorded. Inspiratory muscle effort was calculated as the esophageal and trans-diaphragmatic pressure time products and WOB. Sixteen obese patients (BMI 44 kg/m2 \ub1 8) were included and successfully extubated. Post-extubation inspiratory effort, calculated by WOB, was 1.56 J/L \ub1 0.50, not statistically different from the T piece (1.57 J/L \ub1 0.56) or PSV 0 and PEEP 0 cmH2O (1.58 J/L \ub1 0.57), whatever the index of inspiratory effort. The three tests that maintained pressure support statistically underestimated post-extubation inspiratory effort (WOB 0.69 J/L \ub1 0.31, 1.15 J/L \ub1 0.39 and 1.09 J/L \ub1 0.49, respectively, p < 0.001). Respiratory mechanics and arterial blood gases did not differ between the five tests and the post-extubation condition. Conclusions: In obese patients, inspiratory effort measured during weaning tests with either a T-piece or a PSV 0 and PEEP 0 was not different to post-extubation inspiratory effort. In contrast, weaning tests with positive pressure overestimated post-extubation inspiratory effort. Trial registration: Clinical trial.gov (reference NCT01616901), 2012, June 4th Keywords: Weaning, Mechanical ventilation, Obese, Work of breathing, Acute

Breaking anonymity of some recent lightweight RFID authentication protocols

Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of quick and accurate authentication or identification. In many cases, it has been shown that if such systems are not properly designed, an adversary can cause security and privacy concerns for end-users. In order to deal with these concerns, impressive endeavors have been made which have resulted in various RFID authentications being proposed. In this study, we analyze three lightweight RFID authentication protocols proposed in Wireless Personal Communications (2014), Computers & Security (2015) and Wireless Networks (2016). We show that none of the studied protocols provides the desired security and privacy required by the end-users. We present various security and privacy attacks such as secret parameter reveal, impersonation, DoS, traceability, and forward traceability against the studied protocols. Our attacks are mounted in the Ouafi–Phan RFID formal privacy model which is a modified version of the well-known Juels–Weis privacy model

Cytomegalovirus reactivation in ICU patients

International audienceApproximately 20 years have passed since we reported our results of histologically proven cytomegalovirus (CMV) pneumonia in non-immunocompromised ICU patients. Even if there are more recent reports suggesting that CMV may worsen the outcomes for ICU patients, there is no definite answer to this question: is CMV a potential pathogen for ICU patients or is it simply a bystander? We will describe the pathophysiology of active CMV infection and the most recent insights concerning the epidemiological aspects of these reactivations. Cytomegalovirus can be pathogenic by a direct organ insult (such as for the lung), by decreasing host defences against other microorganisms and/or by enhancing the body's inflammatory response (as in acute respiratory distress syndrome). The incidence of active CMV infection is dependent on the diagnostic method used. Using the most sophisticated available biological tools, the incidence can reach 15-20 % of ICU patients (20-40 % in ICU patients with positive CMV serology). In adequately powered cohorts of patients, active CMV infection appears to be associated with worse outcomes for mechanically ventilated ICU patients. There is no absolute direct proof of a negative impact of active CMV infection on the health outcomes of mechanically ventilated patients. Prospective randomized trials are lacking. Future trials should examine the potential benefits for health outcomes of using antiviral treatments. Such treatments could be prophylactic, pre-emptive or used only when there is an end-organ disease. Cytomegalovirus infection may affect health outcomes for ICU patients. Additional prospective trials are necessary to confirm this hypothesis