Objective
To identify ventilatory setting adjustments that improve patient-ventilator synchrony during pressure-support ventilation in ventilator-dependent patients by reducing ineffective triggering ...events without decreasing tolerance.
Design and setting
Prospective physiological study in a 13-bed medical intensive care unit in a university hospital.
Patients and participants
Twelve intubated patients with more than 10% of ineffective breaths while receiving pressure-support ventilation.
Interventions
Flow, airway-pressure, esophageal-pressure, and gastric-pressure signals were used to measure patient inspiratory effort. To decrease ineffective triggering the following ventilator setting adjustments were randomly adjusted: pressure support reduction, insufflation time reduction, and change in end-expiratory pressure.
Measurements and results
Reducing pressure support from 20.0 cm H
2
O (IQR 19.5–20) to 13.0 (12.0–14.0) reduced tidal volume 10.2 ml/kg predicted body weight (7.2–11.5) to 5.9 (4.9–6.7) and minimized ineffective triggering events 45% of respiratory efforts (36–52) to 0% (0–7), completely abolishing ineffective triggering in two-thirds of patients. The ventilator respiratory rate increased due to unmasked wasted efforts, with no changes in patient respiratory rate 26.5 breaths/min (23.1–31.9) vs. 29.4 (24.6–34.5), patient effort, or arterial PCO
2
. Shortening the insufflation time reduced ineffective triggering events and patient effort, while applying positive end-expiratory pressure had no influence on asynchrony.
Conclusions
Markedly reducing pressure support or inspiratory duration to reach a tidal volume of about 6 ml/kg predicted body weight eliminated ineffective triggering in two-thirds of patients with weaning difficulties and a high percentage of ineffective efforts without inducing excessive work of breathing or modifying patient respiratory rate.
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.
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/m
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.
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/m
± 8) were included and successfully extubated. Post-extubation inspiratory effort, calculated by WOB, was 1.56 J/L ± 0.50, not statistically different from the T piece (1.57 J/L ± 0.56) or PSV 0 and PEEP 0 cmH
O (1.58 J/L ± 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 ± 0.31, 1.15 J/L ± 0.39 and 1.09 J/L ± 0.49, respectively, p < 0.001). Respiratory mechanics and arterial blood gases did not differ between the five tests and the post-extubation condition.
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.
Clinical trial.gov (reference NCT01616901 ), 2012, June 4th.
Objective
To compare 13 commercially available, new-generation, intensive-care-unit (ICU) ventilators in terms of trigger function, pressurization capacity during pressure-support ventilation (PSV), ...accuracy of pressure measurements, and expiratory resistance.
Design and setting
Bench study at a research laboratory in a university hospital.
Methods
Four turbine-based ventilators and nine conventional servo-valve compressed-gas ventilators were tested using a two-compartment lung model. Three levels of effort were simulated. Each ventilator was evaluated at four PSV levels (5, 10, 15, and 20 cm H
2
O), with and without positive end-expiratory pressure (5 cm H
2
O). Trigger function was assessed as the time from effort onset to detectable pressurization. Pressurization capacity was evaluated using the airway pressure–time product computed as the net area under the pressure–time curve over the first 0.3 s after inspiratory effort onset. Expiratory resistance was evaluated by measuring trapped volume in controlled ventilation.
Results
Significant differences were found across the ventilators, with a range of triggering delays from 42 to 88 ms for all conditions averaged (
P
< 0.001). Under difficult conditions, the triggering delay was longer than 100 ms and the pressurization was poor for five ventilators at PSV5 and three at PSV10, suggesting an inability to unload patient’s effort. On average, turbine-based ventilators performed better than conventional ventilators, which showed no improvement compared to a bench comparison in 2000.
Conclusion
Technical performance of trigger function, pressurization capacity, and expiratory resistance differs considerably across new-generation ICU ventilators. ICU ventilators seem to have reached a technical ceiling in recent years, and some ventilators still perform inadequately.
Abstract Background Patients in intensive care units (ICUs) experience severe sleep alterations and conventional sleep scoring rules are difficult to use in these patients. In a previous study, we ...showed that abnormal sleep EEG and wake EEG patterns could predict the outcome of noninvasive ventilation in a group of patients treated for acute respiratory failure. Our aims were to assess the prevalence of these abnormal sleep/wake EEG patterns in a larger group and search for objective parameters to help their identification. Methods We reviewed sleep studies previously performed with full polysomnography during 17-h in conscious nonsedated ICU patients receiving invasive ventilation during weaning or noninvasive ventilation for acute respiratory failure. Results We included 57 patients. Sleep scoring using conventional rules was not feasible in 16 (28%) patients due to the absence of stage-2 markers. Wake EEG in these 16 patients, although recognizable, showed abnormal features, including decreased reactivity to eye opening and slower peak EEG frequency compared to patients with normal sleep–wake EEGs. Conclusion In almost one third of awake mechanically ventilated ICU patients, sleep cannot be classified with standard criteria. Two new states, atypical sleep and pathologic wakefulness, need to be added. We suggest rules for scoring these states. The origin and links with outcomes of these abnormal EEG patterns deserve investigation.
OBJECTIVES:To compare the influence of three ventilatory modes on sleep.
DESIGN:Prospective, comparative, crossover study.
SETTING:Medical intensive care unit in a university hospital.
...PATIENTS:Fifteen conscious, nonsedated, mechanically ventilated patients.
INTERVENTIONS:Patients were successively ventilated with assist-control ventilation, clinically adjusted pressure support ventilation (cPSV), and automatically adjusted pressure support ventilation (aPSV). Sleep polysomnography was performed during three consecutive 6-hr periods, one with each mode in random order. Airway pressure and thorax and abdomen plethysmography were used to diagnose central apneas and ineffective efforts.
MEASUREMENTS AND MAIN RESULTS:The main abnormalities were a low percentage of rapid eye movement (REM) sleep counting, for a median (25th–75th percentiles) of 10% (3.5–12.5) of total sleep, and a highly fragmented sleep with 29 arousals and awakenings per hour of sleep. REM sleep duration was similar in the three ventilatory modes, 7% in assist-control, 4% in aPSV, and 1% during cPSV (p = .54), as well as in the fragmentation index, 31 arousals and awakenings per hour in assist-control, 32 in aPSV, and 34 during cPSV (p = .62). Ineffective efforts occurred similarly with the three modes (seven per hour of sleep in assist-control, 16 in aPSV, and 12 during cPSV) or central apneas during PSV (five in aPSV, seven during cPSV). Minute ventilation was similar with the three modes.
CONCLUSIONS:In conscious, mechanically ventilated patients, sleep architecture was highly abnormal, with a short REM stage and a high degree of fragmentation. The ventilatory mode did not influence sleep pattern, arousals, awakenings, and ineffective efforts.
•The robustness of prior studies relating inbound open innovation and innovation performance is assessed for model uncertainty using Bayesian Model Averaging.•Prior research is shown to have a high ...degree of robustness.•The findings suggest that the results for new-to-the-world innovation are less robust than those related to new-to-the-firm innovation.•Potential applications for Bayesian Model Averaging in innovation studies are suggested.
In studies of firm's innovation performance, regression analysis can involve a significant level of model uncertainty because the ‘true’ model, and therefore the appropriate set of explanatory variables are unknown. Drawing on innovation survey data for France, Germany, and the United Kingdom, we assess the robustness of the literature on inbound open innovation to variable selection choices, using Bayesian model averaging (BMA). We investigate a wide range of innovation determinants proposed in the literature and establish a robust set of findings for the variables related to the introduction of new-to-the-firm and new-to-the-world innovation with the aim of gauging the overall healthiness of the literature. Overall, we find greater robustness for explanations for new-to-the-firm rather than new-to-the-world innovation. We explore how this approach might help to improve our understanding of innovation.
•Complementarities-in-performance between product, process and organizational innovation.•We use two rich samples of French and UK manufacturing firms using CIS4 (2002–2004).•Unconditional tests are ...inconclusive, we suggest conditional pairwise relations.•Complementarities between product and process innovations in French and UK firms.•Complementarities depends on national context, firm size and firm capabilities (R&D).
This paper explores the relationships among product, process and organizational innovation, examining the complementarities-in-performance between these forms of innovation, within a supermodularity framework. Drawing upon two large samples of French and UK manufacturing firms using CIS4 (2002–2004), we explore whether firms can find a beneficial interplay between different forms of innovation. Since unconditional tests are often inconclusive about these complementarities, we implement a new procedure testing pairwise relations conditional on the presence/absence of a third form. Using this approach, we find conditional complementarities between product and process innovations in French and UK firms and between organizational and product innovations in French firms, but no complementarities between all three forms of innovation. Using different sub-samples, we show that the presence of complementarities depends on the national context as well as on firm size and firm capabilities, which gives support to the contingency perspective.
Purpose
Diaphragm function is rarely studied in intensive care patients with unit-acquired weakness (ICUAW) in whom weaning from mechanical ventilation is challenging. The aim of the present study ...was to evaluate the diaphragm function and the outcome using a multimodal approach in ICUAW patients.
Methods
Patients were eligible if they were diagnosed for ICUAW Medical Research Council (MRC) Score <48, mechanically ventilated for at least 48 h and were undergoing a spontaneous breathing trial. Diaphragm function was assessed using magnetic stimulation of the phrenic nerves (change in endotracheal tube pressure), maximal inspiratory pressure and ultrasonographically (thickening fraction). Diaphragmatic dysfunction was defined by a change in endotracheal tube pressure below 11 cmH
2
O. The endpoints were to describe the correlation between diaphragm function and ICUAW and its impact on extubation.
Results
Among 185 consecutive patients ventilated for more than 48 h, 40 (22 %) with a MRC score of 31
20
–
36
were included. Diaphragm dysfunction was observed with ICUAW in 32 patients (80 %). Change in endotracheal tube pressure and MRC score were not correlated. Maximal inspiratory pressure was correlated with change in endotracheal tube pressure after magnetic stimulation of the phrenic nerves (
r
= 0.43;
p
= 0.005) and MRC score (
r
= 0.34;
p
= 0.02). Thickening fraction was less than 20 % in 70 % of the patients and was statistically correlated with change in endotracheal tube pressure (
r
= 0.4;
p
= 0.02) but not with MRC score. Half of the patients could be extubated without needing reintubation within 72 h.
Conclusion
Diaphragm dysfunction is frequent in patients with ICU-acquired weakness (80 %) but poorly correlated with the ICU-acquired weakness MRC score. Half of the patients with ICU-acquired weakness were successfully extubated. Half of the patients who failed the weaning process died during the ICU stay.
This paper investigates obstacles to innovation faced by French manufacturing firms. Using CIS2 data, we distinguish between obstacles in postponed projects and obstacles in abandoned projects. ...First, we highlight the most important barriers to innovation faced by firms, and find that lack of skilled personnel is one of these. Second, based on descriptive analysis, correspondence analysis and multivariate probit models, we explore factors explaining the perception of obstacles, and study complementarities between those obstacles. We show that while adopting a package of policies increases the pace of innovation, a more targeted choice among policies is needed to encourage firms to persevere in their innovative efforts.
In this article we investigate the impact of quality systems on innovation performance using the method of propensity matching. We use two French microeconomic surveys, the “Organizational Changes ...and Computerization” (COI 1997) and the “Community Innovation Survey” (CIS3 1998–2000). The first hypothesis indicating that quality (ISO 9000 certification) impacts positively on innovation is supported for certain areas of innovation performance. Furthermore, the second hypothesis states that different levels of quality differentially improve innovation performance. Results indicate that the innovation performance of firms with Top Quality Level is higher than that of firms with Medium Quality Level which is also higher than that of firms with Low Quality Level for certain areas of innovation. However, we found that the difference in innovation performance between firms with Medium and Low Quality Levels is not of a great magnitude. This study implies that in order to achieve a significant innovation performance improvement via quality systems, a very well-established quality system is needed within a firm.
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