mercredi 5 février 2020 

14h10 - 15h10


 
Forum 5

Ventilation mécanique : nouveautés en physiologie

MODÉRATEUR(S) :  Laurent BROCHARD (Toronto, CANADA ), Arnaud THILLE (Poitiers)  
  

Comparison of pleural and esophageal pressure in supine and prone position in a porcine model of acute respiratory distress syndrome

Orateur(s) :   Nicolas TERZI (Grenoble) 

Auteur(s) :  Sam BAYAT (Grenoble)   Norbert NOURY (Lyon)   Jean-pierre GILIBERTO (Genève)   Sylvie ROULET (Genève)   Emanuele TURBIL (Sassarie, ITALIE)   Walide HABRE (Genève)   Claude GUÉRIN (Lyon)  

14h10 - 14h18
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
Comparison of pleural and esophageal pressure in supine and prone position in a porcine model of acute respiratory distress syndrome

Introduction / Rationale :
Measurement of esophageal pressure (Pes) is the single method currently available to estimate pleural pressure (Ppl) in ICU patients (1). It allows the computation of trans-pulmonary pressure (2) and can be used to set positive end-expiratory pressure (PEEP) (3,4). Prone position (PP) can reduce mortality in patients with acute respiratory distress syndrome (ARDS), but PEEP selection in PP is controversial. In human ARDS end-expiratory Pes at zero flow (PEEPt,es) was not different between supine (SP) and PP at same PEEP (5). As no study measured Ppl in SP and PP in ARDS we aimed at comparing PEEPt,es and end-expiratory Ppl at zero flow (PEEPt,Ppl) in this condition. Our hypothesis was that PEEPt,es was close to dorsal PEEPt,Ppl (PEEPt,Ppldorsal) in SP and to ventral PEEPt,Ppl (PEEPt,Pplventral) in PP.

Méthodes / Patients and Methods :
In 8 female pigs of 40 kgs intubated, sedated, paralyzed and mechanically ventilated, ARDS was induced by repeated saline lavage until PaO2/FIO2<100 mmHg under FIO2 1 and PEEP 5cmH2O. Pes was measured by Nutrivent catheter. Ppl was measured by custom-made pouch sensors inserted surgically into the right anterior and posterior sixth intercostal space. Ppl sensors were filled with air. After ARDS induction animals were randomly assigned to SP or PP. In each position, a recruitment manoeuver was performed and PEEP decreased from 20 to 5 cmH2O by steps of 5cmH2O lasting 10 minutes each, then the animals were crossed over into the alternate position where the same procedure was done. At the end of each step nonstressed volume and correct position (Baydur maneuver) were determined for Pes and Ppl sensors, then a 3-sec end-expiratory occlusion was performed and Pes and Ppl recorded. Linear mixed model was used to compare the value of Pes and Ppl at each PEEP and position.

Résultats / Results :
Box-and-whisker plots of Pes and Ppl in SP and PP are shown in Figure 1. There is marked dorsal-to-ventral gradient in Ppl at each PEEP in SP, which is reverted in PP at PEEP 10 and 15 only. There was no interaction between pressures and PEEP or position. With increasing PEEP Pes increased significantly from PEEP 5 in SP and PP. PEEPt,PplVentral was significantly lower than PEEPt,es in SP but not in PP.

Discussion / Discussion :


Conclusion / Conclusion :
PEEPt,es follows PEEPt,Ppldorsal in SP and PEEPt,Pplventral in PP in this ARDS porcine model.


References: 1.Akioumaniaki et al AJRCCM 2014; 2.Yoshida et al AJRCCM 2018; 3.Talmor et al NEJM 2008; 4.Beitler et al JAMA 2019; 5.Mezidi et al AOIC 2018
 

A systematic bench assessment of automatic tube compensation provided by intensive care unit ventilators

Orateur(s) :   Nicolas TERZI (Grenoble) 

Auteur(s) :  Louis-Marie GALERNEAU (Grenoble)   Zakaria RIAD (Lyon)   Emanuele TURBIL (Sassari, ITALIE)   Carole SCHWEBEL (Grenoble)   Claude GUÉRIN (Lyon)   Bruno LOUIS (Créteil)  

14h18 - 14h26
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
A systematic bench assessment of automatic tube compensation provided by intensive care unit ventilators

Introduction / Rationale :
Automatic tube compensation (ATC) is an option available in intensive care unit (ICU) ventilators to compensate for endotracheal tube (ETT) resistance. To achieve this ICU ventilator delivers a certain amount of pressure/flow that compensates for the resistive pressure drop across ETT. It requires notifying size of ETT and percent of compensation. We reasoned that if ATC works properly tidal volume (VT) should be the same without ATC and no ETT as with ATC and ETT. We tested the performance of ICU ventilators on a bench, expecting furthermore differences between them.

Méthodes / Patients and Methods :
Seven ICU ventilators (Evita XL and V500 infinity (Draeger), C6 and S1 (Nihon-Khoden), Elisa 800 (Lowenstein), 980 (Medtronic), Carescape 860 (GE)) were set in pressure support 0 cmH2O, PEEP 4 cmH2O, FIO2 21% and equipped with the same double limb ventilator circuit (Intersurgical) without any humidification device. ASL 5000 bench model was set with 3 inspiratory/expiratory resistance (R) and compliance (C) combinations: R13/12-C54, R12/14-C39 and R22/18-C59 mimicking normal, ARDS and COPD conditions, respectively (1). Inspiratory effort generated by ASL 5000 consisted of 30 consecutive breaths obtained from the esophageal pressure in a real patient at the time of a spontaneous breathing trial. For each ICU ventilator and RC combination, two steps were performed: in the first, ATC was not activated and ventilator attached to ASL 5000 without ETT (ATC-ETT-); in the second, ATC was set on at 100% compensation for an ETT 8 mm ID and such an ETT (Shiley Hi contour, Covidien) joined ICU ventilator to ASL 5000 (ATC+ETT+). The null hypothesis is that VTATC+ETT+ minus VTATC-ETT- is 0. Primary end point was the breath by breath paired difference betwen ATC+ETT+ and ATC-ETT-. It was tested to zero for each ventilator in each RC condition.

Résultats / Results :
Median VT was 213 ml. Table 1 displays mean (±SD) difference in VT (ml) between ATC+ETT+ and ATC-ETT-: a negative value means that ATC under delivers and a positive value that ATC over delivers VT for a given patient’s inspiratory effort and RC. In four ventilators (C6, S1, Elisa 800 and 980) ATC almost systematically under delivered VT. In several instances under compensation was greater than 10% median VT. By contrast ATC performed better with the other three ventilators (Evita XL, V500 and Carescape 860).

Discussion / Discussion :


Conclusion / Conclusion :
ATC tended to under deliver VT. Furthermore, there were marked differences between ICU ventilators the clinician should be aware of when using the ATC option.
 

Impact of the mechanical power and its components on mortality in patients with ARDS: a post hoc analysis of a controlled randomized study

Orateur(s) :   Radj CALLY (Marseille) 

Auteur(s) :  Claude GUÉRIN (Lyon)   Arnaud GACOUIN (Rennes)   Gilles PERRIN (Marseille)   Anderson LOUNDOU (Marseille)   Samir JABER (Montpellier)   Jean-Michel ARNAL (Toulon)   Dider PEREZ (Lons-Le-Saunier)   Jean-marie SEGHBOYAN (Marseille)   Jean-Michel CONSTANTIN (Clermont-Ferrand)   Jean-yves LEFRANT (Nimes)   Gwenael PRAT (Brest)   Antoine ROCH (Marseille)   Laurent PAPAZIAN (Marseille)   Jean-marie FOREL (Marseille)  

14h26 - 14h34
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
Impact of the mechanical power and its components on mortality in patients with ARDS: a post hoc analysis of a controlled randomized study

Introduction / Rationale :
During the last decades, identification of factors associated with ventilation-induced lung injury has led to improved survival in patients with ARDS. The mechanical power of ventilation is the total energy transmitted from the ventilator to the respiratory system per unit of time and comprises three different components: elastic related to PEEP, elastic related to tidal volume and resistive. This integrative variable has been recently proposed as an useful predictor of ventilation-induced lung injury and death among ventilated patients. Our goal was to determine the respective impact of the total mechanical power and its three components on the outcome of patients with ARDS.

Méthodes / Patients and Methods :
We performed a post hoc analysis of a randomized, controlled study of patients with ARDS with a PaO2/FiO2 ratio < 150. The mechanical power at inclusion and averaged on the first two days after inclusion (total and its three different components) was computed according to the following equation: PowerRS (J/min) = 0.098.Respiratory Rate.Tidal Volume.[PEEP(1) + ½.Driving Pressure(2) + (Peak Pressure – Plateau Pressure)(3)], where the (1), (2) and (3) parts correspond respectively to the elastic related to PEEP, elastic related to tidal volume and resistive components. The association between each of these four types of mechanical power evaluated during the first two days after inclusion and mortality at D90 was assessed one after the other through multiple logistic regression, allowing control for potential confounding variables at inclusion (age, IGS score without age, group of randomization, PaO2/FiO2, arterial pH).

Résultats / Results :
Data from 339 patients were analyzed, among which 115 (33.9 %) died before D90. There was no difference concerning the mechanical power at inclusion between survivors and non survivors (either total or its three components). Among the four different types of mechanical power tested during the first two days after inclusion, the elastic component related to tidal volume was the only one that was independently associated with mortality at D90 (OR 1.030; 95% CI 1.003-1.058; p=0.03) (Figure).

Discussion / Discussion :


Conclusion / Conclusion :
Our study shows that only the elastic component of the mechanical power related to tidal volume independently predicted mortality at D90 among patients with ARDS, whereas the total mechanical power, its elastic component related to PEEP and its resistive component did not. Further studies are needed to better define how the mechanical power of ventilation could be useful to synthetize the risk of ventilation-induced lung injury.
 

A physiological systematic review and meta-analysis on positive end expiratory pressure-induced lung recruitment in patients with acute respiratory distress syndrome

Orateur(s) :   Emanuele TURBIL (Sassari, ITALIE) 

Auteur(s) :  Louis-Marie GALERNEAU (La Tronche)   Antonia KOUTSOUKOU (Athens)   Jean jacques ROUBY (Paris)   Jean DELLAMONICA (Nice,)   Carole SCHWEBEL (La Tronche)   Nicolas TERZI (La Tronche)   Claude GUÉRIN (Lyon)  

14h34 - 14h42
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
A physiological systematic review and meta-analysis on positive end expiratory pressure-induced lung recruitment in patients with acute respiratory distress syndrome

Introduction / Rationale :
Recruited lung volume (Vrec) elicited by positive end-expiratory pressure (PEEP) can be measured using pressure-volume (P-V) curve.
Our purpose was to perform a meta-analysis of Vrec measured by P-V curve in patients with Acute Respiratory Distress Syndrome (ARDS). Primary aim was determination of the prevalence of recruiters (R). Secondary aim was comparison of physiologic data and mortality in R and non-recruiters (NR).

Méthodes / Patients and Methods :
We conducted a PubMed search using the key words: lung recruitment, alveolar recruitment, P-V curve, ARDS, PEEP, humans and adult. All articles were screened by two reviewers. Articles concerning animals, children, case reports and reviews were excluded. Disagreements were resolved by discussion. The same reviewers extracted data in a case record form, which included mortality at ICU discharge, baseline value of anthropometric variables, ARDS cause, physiologic characteristics of patients, ventilator settings, and respiratory mechanics. Vrec ≥ 150 ml was used as the threshold to define R. We first performed a meta-analysis on grouped data, which were pooled applying a random effects model. Then, authors were contacted to obtain individual data. We performed an individual-databased meta-analysis and compared R and NR and survivors and nonsurvivors.Logistic regression (LR) analysis was done to assess the role of Vrec on mortality after adjustment for confounders. These latter were identified by univariate LR analysis between survivors and nonsurvivors. Results were reported as mean, percentage or relative risk (RR), with 95% confidence intervals (CI).

Résultats / Results :
From a total of 817 studies, we retrieved 18 articles that included 361 patients on whom the grouped-data meta-analysis. From data on 283 patients, in part coming from original papers’ authors, the individual-data meta-analysis was performed.
The prevalence of R was 74% (95%CI 64-84%) in grouped-data and 66% (60-71%) in individual-data analyses. In both grouped- and individual-data analyses there were no significant differences between R and NR for baseline age, male proportion, PEEP, PaO2/FIO2, ARDS cause, and days in ARDS before the start of the investigation. In grouped-data analysis compliance was significantly higher (mean difference 13.80 (0.14-27.52) ml/cmH2O) in R, but this result was not confirmed in individual-data analysis. Finally, RR of mortality in grouped-data was 1.20 (0.88-1.63), which was in accordance with individual-data analysis (p-value=1).
After adjusting for confounding variables (PEEP, PaO2/FIO2 and Plateau pressure) Vrec was not an independent risk factor of ICU mortality.

Discussion / Discussion :


Conclusion / Conclusion :
Most ARDS patients exhibited lung recruitment after increase in PEEP with no correlation with ICU mortality.
 

Early effects of mechanical ventilation on diaphragm function and its influence on weaning

Orateur(s) :   Ahlem TRIFI (Tunis, TUNISIE) 

Auteur(s) :  Farah BEN LAMINE (Tunis, TUNISIE)   Cyrine ABDENNEBI (Tunis, TUNISIE)   Foued DALY (Tunis)   Yosr TOUIL (Tunis)   Sami ABDELLATIF (Tunis, TUNISIE)   Salah BEN LAKHAL (Tunis)  

14h42 - 14h50
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
Early effects of mechanical ventilation on diaphragm function and its influence on weaning

Introduction / Rationale :
to examine the effect of early-stage mechanical ventilation (MV) on diaphragmatic contractility. In the 2nd step, if a diaphragmatic dysfunction was detected, we assessed its influence on the weaning from ventilator.

Méthodes / Patients and Methods :
we measured prospectively the ultrasound-diaphragmatic thickening fraction (DTF) between 2 groups: a study group versus a control group (n=30 for each). The study group included all adult patients receiving MV. In whom, the DTF was measured within a minimum of 48 hours and a maximum of 5 days of MV. For the control group, were enrolled after their approval for participation, adult volunteers in spontaneous ventilation (SV). Patients with factors affecting the diaphragmatic contractility (neuromuscular disease, severe obesity, and neuromuscular blockers...) were excluded. The ultrasound measurements were obtained at the zone of apposition of the right hemithorax. Teleinspiratory and telexpiratory diameters (tid/ted) were taken on the 3 medio-axillary lines: posterior, median and anterior. The DTF was calculated as following: DTF = (tid-ted /ted) x 100.
At the 1st step, the DTFs were compared and at the 2nd step: the relationship between DTF and weaning was analysed.

Résultats / Results :
our 2 groups were comparable in corpulence and co morbidities. The SV group was younger (35 vs. 47 years, p <0.05) with a predominant female composition. The diaphragmatic exploration concluded that in the MV group: the mean tid tended to be higher but without significant difference (29.1 + 7 versus 26.1 + 5 mm, p = 0.09), the mean ted was significantly higher (20.9 + 6 versus 17.6 + 3.2 mm, p = 0.01) and DTF was significantly lower (39.9 + 12.5% versus 49 + 20.5%, p = 0.043). The ventilation mode had no effect on DTF (40.2 + 13% for control volume vs. 38.6 + 9% for PSV mode, p=0.8). Fourteen among 30 ventilated patients had a successful weaning with a mean duration of 6 days. A negative correlation was found close to significance between DTF and weaning duration (Rho = - 0.464 and p=0.08). A DTF value > 33% was associated with weaning success (OR = 2, 95% CI = [1.07-3.7] and p=0.058) with sensitivity=85.7%, Specificity=50%, PPV=60% and NPV= 80%.

Discussion / Discussion :


Conclusion / Conclusion :
the diaphragmatic contractile function was altered from the first days of MV. Weaning duration seemed to be negatively correlated with DTF, and a DTF at the first 5 days of MV greater than 33% was predictive of weaning success.
 

Shear wave elastography for assessing diaphragm activity in mechanically ventilated patients

Orateur(s) :   Quentin FOSSÉ (Paris) 

Auteur(s) :  Thomas POULARD (Paris)   Jean yves HOGREL (Paris)   Jean luc GENNISSON (Orsay)   Thomas SIMILOWSKI (Paris)   Alexandre DEMOULE (Paris)   Marie cécile NIÉRAT (Paris)   Damien BACHASSON (Paris)   Martin DRES (Paris)  

14h50 - 14h58
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
Shear wave elastography for assessing diaphragm activity in mechanically ventilated patients

Introduction / Rationale :
Mechanical ventilation is a life-saving treatment that is however associated with lung injury and/or diaphragm dysfunction. The optimal ventilator settings to provide lung protective ventilation while maintaining safe diaphragm activity are difficult to determine. A noninvasive and bedside evaluation of the diaphragm activity could be helpful in this context. The present study investigated whether changes in diaphragm shear modulus (i.e. stiffness, ΔSMdi) assessed by ultrasound shear wave elastography (SWE) may be used as a surrogate of changes in transdiaphragmatic pressure (ΔPdi) in mechanically ventilated patients.

Méthodes / Patients and Methods :
Patients had to be ventilated for at least 24 hours without contraindications for the placement of an œso-gastric catheter. Pdi was monitored continuously and SMdi was measured at the zone of apposition of the right hemi-diaphragm, at 2 Hz sampling rate. Measurements were performed twice under initial ventilator settings and at the end of a weaning trial. Pearson correlation coefficients (r) were computed to determine within-individual correlations between Pdi and SMdi and changes in Pdi and in SMdi occurring between initial ventilator settings and the end of the SBT were compared by a paired test.

Résultats / Results :
Twenty-five patients were enrolled and 8 displayed a significant correlation between ΔSMdi and ΔPdi (mean r=0.73, range= 0.62-0.88, all p<0.05) (Figure 1A). Compared to their counterparts, patients with significant within correlations had a lower respiratory rate (16.8±4.7 vs 23.9±6.2breath/min, respectively; p<0.01) and a significant increase in ΔSMdi (7,3±5,5 kPa vs 13,4±9,0 kPa, p < 0,01) between initial ventilator settings and the SBT. Patients without ΔSMdi-ΔPdi correlation only displayed an increase in ΔPdi (7,9±5,9 vs 14,9±7,9 cmH2O, p<0,01) at the end of the SBT with no concomitant significant increase in ΔSMdi (7,6±3,8 kPa vs 7,9±5,3 kPa, p > 0,05 ). (Figure 1B).

Discussion / Discussion :


Conclusion / Conclusion :
SMdi obtained by SWE appears as a promising technique to assess diaphragm activity in mechanically ventilated patients but technological improvements are necessary to increase SWE sampling rate before enabling its generalization in the ICU.
 

Inspiratory effort can be measured during spontaneous breathing at the bedside : illustration of feasibility

Orateur(s) :   Davy CABRIO (Lausanne, SUISSE) 

Auteur(s) :  Filippo BONGIOVANNI (Lausanne)   Philippe ECKERT (Lausanne)   Lise PIQUILLOUD (Lausanne, SUISSE)  

14h58 - 15h06
Durée de la présentation : 5 min
Durée de la discussion : 3 min


Abstract : 
Inspiratory effort can be measured during spontaneous breathing at the bedside : illustration of feasibility

Introduction / Rationale :
End-inspiratory (EIP) and end-expiratory (EEP) pauses are commonly used during volume assist control ventilation to assess plateau pressure and total positive end-expiratory pressure (PEEPtot). They can also be used during assisted ventilation (AV) for muscle pressure assessment. It requires ventilators able to perform EIP during AV. Plateau pressure (Pplat) usually increases in AV during EIP due to “hidden” inspiratory effort. Pressure muscular index (PMI) is equal to Pplat minus the sum of PEEPtot (measured during an EEP) and set pressure support (PS); it theoretically reflects patient’s effort without esophageal pressure (Pes) monitoring. Pes is the gold standard method to assess inspiratory muscle pressure (Pmus, difference of Pes drop at neural end-inspiration and correction factor for chest wall elastance and tidal volume). We aimed to illustrate the feasibility of measuring PMI using a standard ICU ventilator at the bedside and study the correlation between Pmus and PMI.

Méthodes / Patients and Methods :
Measurements were recorded in 4 ICU patients. Pes was measured using an nasogastric probe (equipped with an esophageal balloon) inserted for advanced monitoring (severe acute respiratory distress syndrome – ARDS) or for a study protocol (difficult weaning after COPD exacerbation). Recorded EIP, EEP and Pes were used for post-hoc analyses. Results reported as ranges and median [IQR]. Correlation between Pmus and PMI tested with Spearman correlation test.

Résultats / Results :
25 out of 28 EIP and EEP duos could be analyzed (2 - esophageal spasm / 1- calibration error). Ventilator mode was pressure support ventilation (PS 0-12 cmH2O). Pplat = 17.9 [15.1 - 21.4] cmH2O, PEEPtot = 5.5 [5 – 8.3] cmH2O, Pmus = 3.5 [1.7 – 9.5] cmH2O, PMI = 4.5 [2.4 – 7.8]. For all recordings, Spearman r coefficient between Pmus and PMI was 0.438 (p = 0.028).

Discussion / Discussion :


Conclusion / Conclusion :
Muscular effort can be assessed in AV using EIP and EEP using ICU ventilators. However, recordings can be influenced by expiratory muscles contraction. Patient's ability to follow directions during the maneuvers is an important factor to obtain reliable values. There seem to be a correlation in our small sample between muscular pressure assessed without and with Pes.