Increasing mean arterial pressure during cardiac surgery does not reduce the rate of postoperative acute kidney injury.

INTRODUCTION: We hypothesized that the optimization of renal haemodynamics by maintaining a high level of mean arterial blood pressure (MAP) during cardiopulmonary bypass (CPB) could reduce the rate of acute kidney injury (AKI) in high-risk patients. METHODS: In this randomized, controlled study, we enrolled 300 patients scheduled for elective cardiac surgery under cardiopulmonary bypass. All had known risk factors of AKI: serum creatinine clearance between 30 and 60 ml/min for 1.73 m(2) or two factors among the following: age >60 years, diabetes mellitus, diffuse atherosclerosis. After a standardized fluid loading, the MAP was maintained between 75-85 mmHg during CPB with norepinephrine (High Pressure, n=147) versus 50-60 mmHg in the Control (n=145). AKI was defined by a 30% increased of serum creatinine (sCr). We further tested others definitions for AKI: RIFLE classification, 50% rise of sCr and the need for haemodialysis. RESULTS: The pressure endpoints were achieved in both the High Pressure (79 ± 6 mmHg) and the Control groups (60 ± 6 mmHg; p<0.001). The rate of AKI did not differ by group (17% vs. 17%; p=1), whatever the criteria used for AKI. The length of stay in hospital (9.5 days [7.9-11.2] vs. 8.2 [7.1-9.4]) and the rate of death at day 28 (2.1% vs. 3.4%) and at six months (3.4% vs. 4.8%) did not differ between the groups. CONCLUSION: Maintaining a high level of MAP (on average) during normothermic CPB does not reduce the risk of postoperative AKI. It does not alter the length of hospital stay or the mortality rate.

Early detection of postoperative acute kidney injury by Doppler renal resistive index in cardiac surgery with cardiopulmonary bypass.

BACKGROUND: Acute kidney injury (AKI) is common after cardiac surgery, affecting outcome. Early detection of an AKI marker is likely to speed diagnosis and implementation of measures to preserve renal function. In septic shock and unselected ventilated subjects, an increased Doppler renal resistive index (RRI) is a predictor of AKI. This study aims to determine whether RRI would act similarly in the postoperative setting of cardiac surgery. METHODS: This study included 65 subjects aged more than 60 yr undergoing elective heart surgery with cardiopulmonary bypass (CPB) and at risk of AKI. All presented at least one AKI risk factor [arteritis, diabetes, or serum creatinine (sCr) clearance of 30-60 ml min(-1)] and were haemodynamically stable without arrhythmia. Doppler RRI was measured in the immediate postoperative period (POP) while subjects were ventilated and sedated. AKI was assessed when sCr increased 30% above the preoperative baseline. RESULTS: Eighteen subjects developed AKI between days 1 and 4, with six requiring dialysis. RRI in the POP was increased in AKI [RRI: 0.79 (0.08) with AKI vs 0.68 (0.06) without AKI, P<0.001], correlating to AKI severity [0.68 (0.06) without AKI, 0.77 (0.08) with AKI but no dialysis, and 0.84 (0.03) with AKI and dialysis, P<0.001]. RRI was similar in subjects receiving catecholamines. RRI >0.74 in the POP predicted delayed AKI with high sensitivity and specificity (0.85 and 0.94, respectively). Multivariate analysis showed that AKI was associated with increased RRI and transfusion. CONCLUSIONS: RRI used in the immediate POP after cardiac surgery with CPB enabled prediction of delayed AKI and anticipation of its severity.

Continuous care and empathic anaesthesiologist attitude in the preoperative period: impact on patient anxiety and satisfaction.

BACKGROUND: Continuous care (one anaesthesiologist per patient) and anaesthesiologist empathy at the preoperative visit could affect patient anxiety and satisfaction. We tested both unproven issues in a population at increased risk of anxiety and dissatisfaction. METHODS: In this single-blinded single-centre study, 136 women undergoing gynaecologic day-care surgery were sequentially randomized into four groups: (i) preoperative visit by an anaesthesiologist with either an empathic or a neutral attitude, and (ii) receiving either continuous or divided care (preoperative visit and anaesthesia performed by two different anaesthesiologists). Preoperative anxiety and wish for information were rated before and after the preoperative visit. Patient appraisal of the anaesthesiologist's attitude and the quality of care provided was obtained in the operating theatre. RESULTS: An empathic attitude at the preoperative visit significantly improved the perception of both the anaesthesiologist attitude (P<0.001) and the quality of information delivered (P<0.001), compared with a neutral anaesthesiologist attitude. Empathic attitude tended to decrease patient anxiety. In the operating theatre, patients who had the same anaesthesiologist (continuous care) exhibited greater satisfaction levels regarding anaesthesiologist behaviour and quality of care (P<0.001). Principal component analysis confirmed these findings, revealing that an empathic preoperative visit was linked to a reduction in preoperative patient anxiety. CONCLUSIONS: The 'one patient, one anaesthesiologist' model, in addition to ensuring sufficient time for open discussion and questions at the preoperative visit, improved patient satisfaction.

[National survey in France about continuing medical education among anaesthesiologists]. / Enquête nationale sur la formation médicale continue des anesthésistes-réanimateurs.

STUDY DESIGN: The aim of this study was to assess how French anaesthesiologists perform continuing medical education (CME). METHODS: A 73 items survey was mailed to 1,000 anaesthesiologists (11% of anaesthesiologists population) of geographic, gender and institution representative of national anaesthesiologist demography. A second mail was sent to non-responders, 6 weeks later. RESULTS: The answer rate was 40.8% and the sample of responders appeared to match the French anaesthesiologist population. Seventy-two percent of surveyed anaesthesiologists were affiliated to the French society of anaesthesia-intensive care and 24% to other medical societies. Attendance to French congresses was 81% and miscellaneous congresses were equally appreciated in terms of quality. Only 17% of surveyed anaesthesiologists attended international congresses. Multi-thematic congresses were preferred by 67%. The annual time devoted to congresses was 6 days (median) with additional 4 days (median) reserved for practical courses. French medical journals and international journals had a reading rate of 89 and 37%, respectively. For 61% of responders CME was funded by institutional grants. Internet CME use was found in 73% of anaesthesiologists. Time and money were the two most frequent reasons invoked for CME restriction. CONCLUSION: CME is a broadly shared activity, which still remains focussed on national resources.

[Conventional and diffusion magnetic resonance imaging in the acute phase of severe traumatic brain injury]. / Apports de l'IRM conventionnelle et de l'IRM de diffusion à la phase aiguë du traumatisme crânien grave.

Neuro-imaging is essential for the initial evaluation and subsequent control in the acute stage of severe head injury. In these indications tomodensitometry (TDM) has a pivotal role. Despite the well recognized contribution of magnetic resonance imaging (MRI) to the investigation of most of acute neurological pathologies, MRI is not still a routine procedure for the initial investigation of patients with acute head injury. The superiority of morphological and functional MRI on TDM in this indication is discussed.

Transesophageal echocardiographic assessment of left ventricular function during apnea testing for brain death.

The effects of apnea testing-induced respiratory acidosis on left ventricular function (LVF) are still controversial. The aim of the study was to assess LVF during apnea testing using transesophageal echocardiography (TEE). Twenty consecutive patients suspected of brain death, hemodynamically stable, and considered as potential organ donors were prospectively studied. A 20-min apnea test was performed after obtaining a PaCO2 > 35 mmHg and 20 min of FIO2 1 ventilation. LVF was assessed using TEE with a CFM 750 (Diasonic) connected to a 5 MHz probe. Heart rate (HR), mean arterial pressure (MAP), left ventricle end-diastolic and systolic area (LVEDA, LVESA), and LVF assessed by fractional area changes (FAC), systolic wall motion (SWM) scores, and blood gases were recorded at baseline, and after 5, 10, 15, and 20 min of apnea testing. In 19 patients, no spontaneous respiratory movement occurred during the standard 20-min period. In one patient (No. 15), the apnea test had to be stopped after 10 min because of hypoxia. HR, LVEDA, LVESA, and SWM were not significantly modified during the study. There was a progressive statistically significant decrease in MAP during apnea (from 77 +/- 10 to 63 +/- 11 mmHg), associated with a statistically significant increase in FAC at 20 min (from 48 +/- 13 to 56 +/- 8%). PaCO2 progressively rose (from 40 +/- 3 to 95 +/- 11 mmHg), associated with a decrease in pH (from 7.42 +/- 0.06 to 7.09 +/- 0.08). At the same time, PaO2 decreased slightly in all patients, but values remained well above hypoxic levels, except for one patient. Despite severe respiratory acidosis the increase in FAC suggests that apnea testing is well tolerated for brain death assessment.

Correlation between simple clinical parameters and the in vitro humidification characteristics of filter heat and moisture exchangers. Groupe de Travail sur les Respirateurs.

STUDY OBJECTIVE: This study on ventilated patients in ICUs examined a large sample of heat and moisture exchanger filters (HMEFs) to determine whether simple clinical parameters are correlated with exchanger humidity output. DESIGN: A total of 594 HMEFs (18 types of HMEF) were tested in nine university hospital ICUs. PATIENTS: Each HMEF was tested on one different unselected and consecutive patient for 24 h. INTERVENTIONS: The following parameters were rated at each tracheal aspiration on a scale of 0 to 3: secretion abundance, viscosity (Visc), suction catheter adherence (Adh) to the endotracheal tube, and the amount of water condensed in the flex tube (Cond). Individual values for each type of HMEF and each variable were averaged and correlated with the humidity output (HO) of the HMEFs, values which were supplied by the manufacturers. RESULTS: There were significant correlations between HO and Cond (r=0.82, p<10(-3)), Visc (r=-0.67, p=0.002), and Adh (r=-0.56, p=0.01). A second study recorded the same variables, for three consecutive 24-h periods, using first a high-humidifying HMEF (DAR Hygrobac), followed by a low-humidifying one (Pall BB22-15), and again DAR Hygrobac. Visc and Adh were higher (p<0.05) and Cond was lower (p<0.05) with the Pall than with the DAR. CONCLUSIONS: Simple clinical parameters correlate well with the efficiency of HMEFs. The apparent water condensed in the flex tubing seems to be the best indicator of the humidifying efficiency of HMEFs.

Can portable chest x-ray examination accurately diagnose lung consolidation after major abdominal surgery? A comparison with computed tomography scan.

PURPOSE: To prospectively quantify the degree of accuracy of portable chest x-ray film examination in the detection of postoperative lung consolidations. STUDY: Nineteen patients had a chest x-ray film and computed tomography (CT) scan the day before and 48 h following elective abdominal aortic replacement. RESULTS: The diagnosis of lung consolidations by x-ray film examination showed sensitivity of between 0.33 and 1.00, depending on the lung zone considered (lower at the lung bases). Specificity always was greater than 0.79. Radiologic lung volume decreased 16 percent postoperatively (p < 0.01) on average and noninflated parenchyma increased by a factor of 3 (p < 0.0001). Postoperatively, PaO2 correlated with the amount of condensed lung by CT scan (p < 0.002). CONCLUSION: In postoperative conditions, x-ray film examination is a method which presents good specificity but poor sensitivity in the diagnosis of lung consolidations.

Effects of positive end-expiratory pressure increments can be predicted by computer simulation based on a physiological profile in acute respiratory failure.

OBJECTIVE: We examined whether computer simulation predicts airway pressures after increments of positive end-expiratory pressure (PEEP) in acute respiratory failure. DESIGN AND SETTING: Prospective, nonrandomized comparative trial in an intensive care unit of a university hospital. PATIENTS: Twelve consecutive acute respiratory failure patients. INTERVENTIONS. PEEP increments from 0 to 2.5, 5, 7.5, 10, and 15 cm H(2)O. MEASUREMENTS AND RESULTS: A physiological profile comprising values for compliance, respiratory resistance and CO(2 )elimination as a function of tidal volume was established from a recording of ordinary breaths prior to increments of PEEP. Airway pressures and CO(2 )elimination were measured 30 s after resetting, pressures also after 10 min. Values from simulation of the resetting, based on the profile, were compared to measured values. The profiles indicated vast differences in physiology between the 12 subjects. Errors of simulation of airway pressures were nonsignificant or trivial up to PEEP levels of 10 cm H(2)O (95% of errors <3 cm H(2)O). After 10 min plateau pressure averaged 1.5 cm H(2)O lower than 30 s after resetting. At increments to PEEP 7.5, 10, and 15, CO(2 )elimination fell by on average 4%, 8%, and 11%, respectively. As tidal volume and respiratory rate was unchanged this was not predicted. CONCLUSIONS: On the basis of a simple lung model, simulation predicted effects of moderate increments of PEEP on airway pressures in patients with complex physiology.

Effects of positive end-expiratory pressure on dead space and its partitions in acute lung injury.

OBJECTIVE: A large tidal volume (VT) and lung collapse and re-expansion may cause ventilator-induced lung injury (VILI) in acute lung injury (ALI). A low VT and a positive end-expiratory pressure (PEEP) can prevent VILI, but the more VT is reduced, the more dead space (VD) compromises gas exchange. We investigated how physiological, airway and alveolar VD varied with PEEP and analysed possible links to respiratory mechanics. SETTING: Medical and surgical intensive care unit (ICU) in a university hospital. DESIGN: Prospective, non-randomised comparative trial. PATIENTS. Ten consecutive ALI patients. INTERVENTION: Stepwise increases in PEEP from zero to 15 cm H2O. MEASUREMENTS AND RESULTS: Lung mechanics and VD were measured at each PEEP level. Physiological VD was 41-64% of VT at zero PEEP and increased slightly with PEEP due to a rise in airway VD. Alveolar VD was 11-38% of VT and did not vary systematically with PEEP. However, in individual patients a decrease and increase of alveolar VD paralleled a positive or negative response to PEEP with respect to oxygenation (shunt), respectively. VD fractions were independent of respiratory resistance and compliance. CONCLUSIONS: Alveolar VD is large and does not vary systematically with PEEP in patients with various degrees of ALI. Individual measurements show a diverse response to PEEP. Respiratory mechanics were of no help in optimising PEEP with regard to gas exchange.

Test of 20 similar intensive care ventilators in daily use conditions--evaluation of accuracy and performances.

Infrequent control, aging of components, may compromise the accuracy of ICU ventilators. In order to assess the reliability of ventilators during their clinical use, we bench tested a group of 20 CPU1 ventilators (Ohmeda) sampled at random in several ICU units. We found major leaks in 5 ventilators, attributable to the disposable tubings used in these systems. Mean error in expired tidal volume and corresponding standard deviation (precision) were greater than 100 ml in two. Positive end expiratory pressure measurement comprised a mean error higher than 2 cm H2O in 40% of the ventilators tested. The valve opening pressure threshold was correlated to the inspiratory flow (r = 0.81) contrary to the valve opening delay (average 138 +/- 40 ms). These two parameters did not correlate with the age of the ventilator. Our study addresses the need for periodic control of ventilator performance in order to minimize the risks of errors and malfunctions.

Topical upper airway anaesthesia with lidocaine increases airway resistance by impairing glottic function.

OBJECTIVE: To assess if two different forms of upper airway topical anaesthesia induce similar changes in airway flow resistance (Rrs). DESIGN: Serial measurements of Rrs before and after topical anaesthesia with acqueous or paste lidocaine. SETTING: Lung function test laboratory. PARTICIPANTS: 9 normal men with documented normal lung function tests. INTERVENTIONS: 2 different session of topical upper airway anaesthesia with 100 mg of liquid 5% lidocaine and 100 mg of 2% lidocaine paste, respectively. MEASUREMENTS AND RESULTS: Rrs was measured by the random noise forced oscillation technique. Fiberoptic upper airway examination was performed in two subjects. Rrs increased on average by 81% after lidocaine spray and by 68% after lidocaine paste (p < 0.005, respectively) with no difference in the magnitude of Rrs increase between the two modes of anaesthesia studied. This increase lasted 13 +/- 3 min (spray) and 12 +/- 3 min (paste), respectively (p = ns). Fiberoptic examination of the two most responders showed inspiratory laryngeal collapse. CONCLUSIONS: Topical upper airway anaesthesia transiently increases Rrs with no specific effects regarding the drug presentation. Laryngeal dysfunction may be one mechanisms involved in Rrs increase following upper airway topical anaesthesia. Such findings may explain some poor respiratory tolerance reported during endoscopy.

Contribution of bronchoalveolar lavage to the diagnosis of posttraumatic pulmonary fat embolism.

OBJECTIVE: To verify whether the determination of the percentage of cells recovered by bronchoalveolar lavage and containing fat inclusions is a useful diagnostic tool of posttraumatic pulmonary fat embolism. DESIGN: Prospective study. SETTING: Surgical Intensive Care Units in two university hospitals. PATIENTS: 56 successive trauma patients needing prolonged postinjury mechanical ventilation, including 4 with clinical definite fat embolism syndrome, 5 in whom the diagnosis had been clinically suspected but was impossible to confirm or exclude before bronchoscopy, and 47 with no clinical evidence of the syndrome. Control groups included 8 patients without previous trauma who developed ARDS and 6 healthy surgical patients. METHODS: Bronchoalveolar lavage was performed within the first post-traumatic 3 days in trauma patients, at the beginning of the pulmonary disease in non trauma ARDS patients and just after anesthesic induction in healthy ortopedic patients. The magnitude of lipid content in alveolar cells was compared with the clinical pattern of the pulmonary fat embolism syndrome retrospectively evaluated at the seventh day postinjury in trauma patients. RESULTS: All the patients with definite fat embolism syndrome had more than 70% of lavage cells containing fat droplets. The group of patients in whom the diagnosis of the fat embolism syndrome was suspected had percentages of fat cells above 30% in 4 out of 5 patients. A percentage of fat cells above 30% was only observed in 7 out of the 47 patients without clinical evidence of the syndrome. The percentage varied between 0% to 35% in the group of non trauma ARDS patients and between 0 to 5% in healthy surgical patients. CONCLUSION: Lipid inclusions in alveolar cells are common during traumatic and non-traumatic respiratory failure. Determination of the percentage of cells recovered by bronchoalveolar lavage and containing fat droplets may contribute to the diagnosis of the fat embolism syndrome in mechanically-ventilated trauma patients with respiratory failure provided that the significant threshold would be 30%.

Respiratory resistance by end-inspiratory occlusion and forced oscillations in intubated patients.

Measurement of respiratory impedance by the forced oscillation technique (FOT) in intubated patients requires corrections for the flow-dependent resistance, inertance, and air compression inside the endotracheal tube (ETT). Recently, we published a method to correct respiratory impedance for the mechanical contribution of the ETT. To validate this correction, we compared the respiratory resistance obtained with this method (Rfo) to the intrinsic (Rmin) and total resistances (RT) measured by the airway-occlusion technique (OCT) in 16 intubated sedated paralyzed ventilated patients. The FOT was applied at functional residual capacity in the 4- to 32-Hz frequency range, whereas the OCT was performed at the end of a normal constant-flow inspiration. Rmin corrected with Rfo measured at 16 and 32 Hz [Rfo(16) = 1.10 x Rmin + 0.10 cmH2O.s.l-1, r = 0.96, P < 0.001; Rfo(32) = 0.93 x Rmin + 0.72 cmH2O.s.l-1, r = 0.97, P < 0.001]. RT corrected with Rfo at 4 Hz [Rfo(4) = 1.11 x RT - 1.48 cmH2O.s.l-1; = 0.92; P < 0.001]. We conclude that the FOT improved by correction for the behavior of the ETT is in good agreement with the OCT in intubated patients.

Mechanics of respiratory system in healthy anesthetized humans with emphasis on viscoelastic properties.

The classic model of the respiratory system (RS) is comprised of a Newtonian resistor in series with a capacitor and a viscoelastic unit including a resistor and a capacitor. The flow interruption technique has often been used to study the viscoelastic behavior under constant inspiratory flow rate. To study the viscoelastic behavior of the RS during complete respiratory cycles and to quantify viscoelastic resistance (Rve) and compliance (Cve) under unrestrained conditions, we developed an iterative technique based on a differential equation. We, as others, assumed Rve and Cve to be constant, which concords with volume and flow dependency of model behavior. During inspiration Newtonian resistance (R) was independent of flow and volume. During expiration R increased. Static elastic recoil showed no significant hysteresis. The viscoelastic behavior of the RS was in accordance with the model. The magnitude of Rve was 3.7 +/- 0.7 cmH2O.l-1 x s, i.e., two times R. Cve was 0.23 +/- 0.051 l/cmH2O, i.e., four times static compliance. The viscoelastic time constant, i.e., Cve.Rve, was 0.82 +/- 0.11s. The work dissipated against the viscoelastic system was 0.62 +/- 0.13 cmH2O x 1 for a breath of 0.56 liter, corresponding to 32% of the total energy loss within the RS. Viscoelastic recoil contributed as a driving force during the initial part of expiration.

Changes in cerebral blood flow during PaCO2 variations in patients with severe closed head injury: comparison between the Fick and transcranial Doppler methods.

OBJECT: The aim of this study was to reassess whether middle cerebral artery blood flow velocity (MCAv) variations measured by transcranial Doppler ultrasonography during acute PaCO2 manipulation adequately reflect cerebral blood flow (CBF) changes in patients with severe closed head injury. METHODS: The study was performed by comparing MCAv variations to changes in CBF as assessed by measurements of the difference in the arteriovenous content in oxygen (AVDO2). The authors initiated 35 CO2 challenges in 12 patients with severe closed head injury during the acute stage. By simultaneous recording of systemic and cerebral hemodynamic parameters, 105 AVDO2 measurements were obtained. Patients were stratified into two groups, "high" and "low," with respect to whether their resting values of MCAv were greater than 100 cm/second during moderate hyperventilation. Four patients displayed an elevated MCAv, which was related to vasospasm in three cases and to hyperemia in one case. The PaCO2 and intracranial pressure levels were not different between the two groups. The slope of the regression line between 1 divided by the change in (delta)AVDO2 and deltaMCAv was not different from identity in the low group (1/deltaAVDO2 = 1.08 x deltaMCAv - 0.07, r = 0.93, p < 0.001) and significantly differed (p < 0.05) from the slope of the high group (1/deltaAVDO2 = 1.46 x deltaMCAv - 0.4, r = 0.83, p < 0.001). CONCLUSIONS: In patients with severe closed head injury, MCAv variations adequately reflect CBF changes as assessed by AVDO2 measurements in the absence of a baseline increase in MCAv. These observations indicate that both moderate variations in PaCO2 and variations in cerebral perfusion pressure do not act noticeably on the diameter of the MCA. The divergence from the expected relationship in the high group seems to be due to the heterogeneity of CO2-induced changes in cerebrovascular resistance between differing arterial territories.

[Hemiplegia during carbon monoxide poisoning revealing multiple cerebral artery abnormalities including the hypoglossal artery]. / Hémiplégie au cours d'une intoxication oxycarbonée révélant des anomalies artérielles cérébrales multiples dont une artère hypoglosse.

Hemiplegia after carbon monoxide (CO) poisoning is rare since only 9 such lesions have been reported from among 1480 cases of poisoning. The patient reported was a 43 year-old man with a left hemiplegia with coma following CO poisoning. Right carotid angiography demonstrated a hypoglossal artery supplying both posterior cerebral arteries. Left carotid angiography showed a dolichocarotid artery supplying the territories of the anterior and middle cerebral arteries on both sides. Complete regression of the hemiplegia occurred after 2 months following rapid administration of hyperbaric oxygen. Normal CT scan images and cerebral blood flow rates on follow-up examination suggest that the left hemiplegia was due to the combined effects of arterial anomalies and CO poisoning.

[A study of pneumatic performances of 2 new anesthesia ventilators: a trial]. / Etude des performances pneumatiques de deux nouveaux ventilateurs d'anesthésie: banc d'essai.

OBJECTIVE: To assess the pneumatic performance of two new anaesthesia ventilators. STUDY DESIGN: Test bench study. MATERIAL: ADU (Datex), Excel 7900 (Ohmeda) ventilators both included in "bellows-in-box" class, with rising bellows at expiration. METHODS: The accuracy of spirometry and pressure measurements was tested in various conditions of downstream charge and ventilation. The bench comprized a passive lung model with adjustable compliance and resistances, and flow and pressure gauges. RESULTS: Pneumatic performance and accuracy were good in normal as well as in severe ventilatory conditions. This is made possible by the compensation algorithm included in these machines, which automatically corrected the delivered volume for errors related to tubing and gas compressibility. CONCLUSION: These two new machines with pneumatic compensation overcome the main drawback seen with conventional "bellows-in-box" ventilators.

[A study of 3 new ventilators for anesthesia: a series of tests]. / Etude de trois nouveaux ventilateurs d'anesthésie: banc d'essai.

We report the bench testing of three new anaesthesia ventilators: Flexima (Datex), SA2/RA2 and Cato (Dräger). The test circuit included a two compartment lung model, a pneumotachograph and a pressure gauge. Volume was integrated from flow signal. The tidal volume delivered by the Flexima and SA2/RA2 ventilators decreased with increasing mechanical work load contrarily to the Cato. Moreover, the tidal volume of the Flexima increased with the fresh gas flow. In spontaneous ventilation inspiratory resistance were low.