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The development of extracorporeal membrane oxygenation (ECMO) technology allows a new approach for the intensive care management of acute cardiac and/or respiratory failure in adult patients who are not responsive to conventional treatment. Current ECMO therapies provide a variety of options for the multidisciplinary teams who are involved in the management of these critically ill patients. In this regard, veno-venous ECMO (VV-ECMO) can provide quite complete respiratory support, even if this highly complex technique presents substantial risks, such as bleeding, thromboembolic events and infection. While VV-ECMO circuits usually include the cannulation of two vessels (double cannulation) in its classic configuration, the use of a single cannula is now possible for VV-ECMO support. Recently, experienced centers have employed more advanced approaches by cannulating three vessels (triple cannulation) which follows veno-arterio-venous (VAV) or veno-arterio-pulmonary-arterial cannulation (VAPa). However, 'triple' cannulation expands the field of application but increases the complexity of ECMO systems. In the present review, the authors focus on the indications for VV-ECMO, patient assessment prior to cannulation, the role of ultrasound-guided vessel puncture, double lumen single bicaval cannulations, and finally triple cannulation in VV-ECMO.

Objective: Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. Design and setting: Bench model study in an intensive care research laboratory of auniversity hospital. Methods: Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to alung model featuring aplastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. Results: On most ventilators leaks led to an increase in trigger delay and workload, adecrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. Conclusions: The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilator

Objective: To evaluate the impact of helium-oxygen (He/O2) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support. Design and setting: Prospective crossover interventional study in the medical ICU of a university hospital. Patients and participants: Ten patients. Interventions: Sequential inhalation (30min each) of three gas mixtures: (a) air/O2, (b) He/O2 (c) air/O2, at constant FIO2 and level of pressure support. Measurements and results: Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO2 were 14±3cmH2O and 0.33±0.07 respectively. Compared to Air/O2, He/O2 reduced the number of ineffective breaths (4±5 vs. 9±5 breaths/min), intrinsic PEEP (3.1±2 vs. 4.8±2cmH2O), the magnitude of negative esophageal pressure swings (6.7±2 vs. 9.1±4.9cmH2O), pressure-time product (42±37 vs. 67±65cmH2Os−1min−1), and total WOB (11±3 vs. 18±10J/min). Elastic (6±1 vs. 10±6J/min) and resistive (5±1 vs. 9±4J/min) components of the WOB were decreased by He/O2. Conclusions: In intubated COPD patients ventilated with pressure support He/O2 reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O2 could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weaning

To compare the effects of He/O(2) and external PEEP (PEEPe) on intrinsic PEEP (PEEPi), respiratory mechanics, gas exchange, and ventilation/perfusion (V(A)/Q) in mechanically ventilated COPD patients.Prospective, interventional study in the intensive care unit of a university hospital.Ten intubated, sedated, paralyzed, mechanically ventilated COPD patients studied in the following conditions: (a) baseline settings made by clinician in charge, air/O(2), ZEEP; (b) He/O(2), ZEEP; (c) air/O(2), ZEEP; (d) air/O(2), PEEPe 80% of PEEPi. Measurements at each condition included V(A)/Q by the multiple inert gas elimination technique (MIGET).PEEPi and trapped gas volume were comparably reduced by He/O(2) (4.2+/-4 vs. 7.7+/-4 cmH(2)O and 98+/-82 vs. 217+/-124 ml, respectively) and PEEPe (4.4+/-1.3 vs. 7.8+/-3.6 cmH(2)O and 120+/-107 vs. 216+/-115 ml, respectively). He/O(2) reduced inspiratory and expiratory respiratory system resistance (15.5+/-4.4 vs. 20.7+/-6.9 and 19+/-9 vs. 28.8+/-15 cmH(2)O l(-1)s(-1), respectively) and plateau pressure (13+/-4 vs. 17+/-6 cmH(2)O). PEEPe increased airway pressures, including total PEEP, and elastance. PaO(2)/FIO(2) was slightly reduced by He/O(2) (225+/-83 vs. 245+/-82) without significant V(A)/Q change.He/O(2) and PEEPe comparably reduced PEEPi and trapped gas volume. However, He/O(2) decreased airway resistance and intrathoracic pressures, at a small cost in arterial oxygenation. He/O(2) could offer an attractive option in COPD patients with PEEPi/dynamic hyperinflation.

Purpose: To determine if, compared to pressure support (PS), neurally adjusted ventilatory assist (NAVA) reduces patient-ventilator asynchrony in intensive care patients undergoing noninvasive ventilation with an oronasal face mask. Methods: In this prospective interventional study we compared patient-ventilator synchrony between PS (with ventilator settings determined by the clinician) and NAVA (with the level set so as to obtain the same maximal airway pressure as in PS). Two 20-min recordings of airway pressure, flow and electrical activity of the diaphragm during PS and NAVA were acquired in a randomized order. Trigger delay (T d), the patient's neural inspiratory time (T in), ventilator pressurization duration (T iv), inspiratory time in excess (T iex), number of asynchrony events per minute and asynchrony index (AI) were determined. Results: The study included 13 patients, six with COPD, and two with mixed pulmonary disease. T d was reduced with NAVA: median 35ms (IQR 31-53ms) versus 181ms (122-208ms); p=0.0002. NAVA reduced both premature and delayed cyclings in the majority of patients, but not the median T iex value. The total number of asynchrony events tended to be reduced with NAVA: 1.0events/min (0.5-3.1events/min) versus 4.4events/min (0.9-12.1events/min); p=0.08. AI was lower with NAVA: 4.9 % (2.5-10.5 %) versus 15.8 % (5.5-49.6 %); p=0.03. During NAVA, there were no ineffective efforts, or late or premature cyclings. PaO2 and PaCO2 were not different between ventilatory modes. Conclusion: Compared to PS, NAVA improved patient ventilator synchrony during noninvasive ventilation by reducing T d and AI. Moreover, with NAVA, ineffective efforts, and late and premature cyclings were absent

Pulmonary embolism remains an important clinical problem with a high mortality rate. The potential for sudden and fatal hemodynamic deterioration highlights the need for a prompt diagnosis and appropriate intervention. The purpose of the present case report is to describe a successful peri-operative veno-arterial extra corporeal membrane oxygenation (VA-ECMO) implantation for assumed massive pulmonary embolism associated with high hemodynamic instability and severe hypoxemia. A 52-year-old female victim of a motorcycle accident had been operated on for unstable fractures that required optimal repair. Despite subcutaneous administration of 40 mg enoxaparin on day 0 and day 1, the patient developed a massive pulmonary embolism leading to peri-operative pulseless activity. As intravenous thrombolysis was strictly contraindicated, a VA-ECMO was successfully implanted and permitted to stabilize the patient's hemodynamics. The hemodynamic and respiratory status improved by day 3, and the ECMO was removed. A vena cava filter was implanted before successful and definitive stabilization of the femoral fracture and the L2 fracture on days 4 and 5. The patient was able to be mobilized 2 days after the surgery and was transferred to a rehabilitation ward on day 15. At that time, her cognitive functions had fully recovered. ECMO can provide lifesaving hemodynamic and respiratory support in patients with massive pulmonary embolism who are too unstable to tolerate other interventions, who have failed other therapies or for whom other therapies are contraindicated.

Neurally adjusted ventilatory assist (NAVA) is a ventilation assist mode that delivers pressure in proportionality to electrical activity of the diaphragm (Eadi). Compared to pressure support ventilation (PS), it improves patient-ventilator synchrony and should allow a better expression of patient's intrinsic respiratory variability. We hypothesize that NAVA provides better matching in ventilator tidal volume (Vt) to patients inspiratory demand. 22 patients with acute respiratory failure, ventilated with PS were included in the study. A comparative study was carried out between PS and NAVA, with NAVA gain ensuring the same peak airway pressure as PS. Robust coefficients of variation (CVR) for Eadi and Vt were compared for each mode. The integral of Eadi (ʃEadi) was used to represent patient's inspiratory demand. To evaluate tidal volume and patient's demand matching, Range90 = 5-95 % range of the Vt/ʃEadi ratio was calculated, to normalize and compare differences in demand within and between patients and modes. In this study, peak Eadi and ʃEadi are correlated with median correlation of coefficients, R > 0.95. Median ʃEadi, Vt, neural inspiratory time (Ti_ ( Neural )), inspiratory time (Ti) and peak inspiratory pressure (PIP) were similar in PS and NAVA. However, it was found that individual patients have higher or smaller ʃEadi, Vt, Ti_ ( Neural ), Ti and PIP. CVR analysis showed greater Vt variability for NAVA (p < 0.005). Range90 was lower for NAVA than PS for 21 of 22 patients. NAVA provided better matching of Vt to ʃEadi for 21 of 22 patients, and provided greater variability Vt. These results were achieved regardless of differences in ventilatory demand (Eadi) between patients and modes.

This article reviews selected contributions published in 2010 regarding epidemiology, clinical use, and consequences of invasive and noninvasive mechanical ventilation (MV). This includes the use of protective ventilation and of different modes, some specific risks of MV, such as ventilator-induced diaphragm dysfunction, and the importance of spontaneous breathing activity under MV, with or without sedation.

Objective: To explore the user-friendliness and ergonomics of seven new generation intensive care ventilators. Design: Prospective task-performing study. Setting: Intensive care research laboratory, university hospital. Methods: Ten physicians experienced in mechanical ventilation, but without prior knowledge of the ventilators, were asked to perform eight specific tasks [turning the ventilator on; recognizing mode and parameters; recognizing and setting alarms; mode change; finding and activating the pre-oxygenation function; pressure support setting; stand-by; finding and activating non-invasive ventilation (NIV) mode]. The time needed for each task was compared to a reference time (by trained physiotherapist familiar with the devices). A time >180s was considered a task failure. Results: For each of the tests on the ventilators, all physicians' times were significantly higher than the reference time (P

Resume La ventilation non invasive (VNI) est actuellement le traitement de premiere intention des insuffisances respiratoires aigues, notamment hypercapniques (IRA). La VNI reduit le recours a une ventilation invasive et donc permet de diminuer les complications qui lui sont associees. Cette technique presente cependant un taux d’echec de 40 %. Ceux-ci sont en partie lies a la tolerance de la technique qui dans un certain nombre de cas est liee aux performances du ventilateur. Le choix de celui-ci, de par ses caracteristiques mecaniques, sa convivialite ou la possibilite de compenser l’effet des fuites, pourrait donc etre un element essentiel de la reussite de la VNI. Les ventilateurs a disposition sont de trois types : les ventilateurs de type « domicile », les ventilateurs lourds de « reanimation » et les ventilateurs dits « intermediaires ». Les caracteristiques techniques et les performances des trois groupes de ventilateurs sont inegales entre les groupes et a l’interieur de chaque groupe. La superiorite d’un type de ventilateur sur un autre n’a jamais ete demontree et il n’existe donc pas de recommandations publiees a ce sujet. Neanmoins, compte tenu des differences de performances globales, il semble logique d’utiliser des ventilateurs de type domicile et intermediaire pour les decompensations moderees. Alors que pour les situations de detresse respiratoire avec une demande inspiratoire elevee un ventilateur de reanimation semble plus adapte notamment en raison de reglage possible de FiO2 elevees. Le choix d’un ventilateur doit aussi tenir compte du type et des habitudes du service et de son cout.

Objective: To test the feasibility of applying noninvasive ventilation (NIV) using aprototype algorithm implemented in abilevel ventilation device designed to adjust pressure support (PS) to maintain aclinician-set alveolar ventilation in patients with acute respiratory failure after initial stabilization. Design and setting: Prospective crossover interventional study in an intensive care unit, university hospital. Patients: 19 patients receiving NIV for acute hypercapnic respiratory failure (13 men, 6 women; mean age 70 ± 11 years). Methods: The same bilevel ventilator was used with manually adjusted PS and with the automated algorithm (autoPS), set to maintain the same alveolar ventilation as in PS. Sequence (measurements at end of each period): (a) prior to initiating NIV (baseline 1); (b) 45 min with manually set PS; (c) 60 min without NIV; (d) 45 min with autoPS; (e) 60 min without NIV; (f) 45 min with manually set PS. Results: The magnitude of decrease in PaCO2 and increase in pH with autoPS was comparable to that of conventional PS, with the same alveolar ventilation and level of PS. No technical problem occurred in autoPS mode, and no NIV trial had to be discontinued because of patient discomfort. Conclusions: These results suggest that the alveolar ventilation based automatic control of PS during NIV with abilevel device is feasible and leads to beneficial effects in patients with acute respiratory failure comparable to those of manually set PS. Further studies should now explore the potential of this system over longer periods in patients with acute and chronic respiratory failure

Background During the past few years, many manufacturers have introduced new modes of ventilation in anesthesia ventilators, especially partial-pressure modalities. The current bench test study was designed to compare triggering and pressurization of five new anesthesia ventilators with four intensive care unit ventilators. Methods Ventilators were connected to a two-compartment lung model. One compartment was driven by an intensive care unit ventilator to mimic "patient" inspiratory effort, whereas the other was connected to the tested ventilator. The settings of ventilators were positive end-expiratory pressures of 0 and 5 cm H2O, and pressure-support ventilation levels of 10, 15, and 20 cm H2O with normal and high "patient" inspiratory effort. For the anesthesia ventilators, all the measurements were obtained for a low (1 l/min) and a high (10 l/min) fresh gas flow. Triggering delay, triggering workload, and pressurization at 300 and 500 ms were analyzed. Results For the five tested anesthesia ventilators, the pressure-support ventilation modality functioned correctly. For inspiratory triggering, the three most recent anesthesia machines (Fabius, Drägerwerk AG, Lübeck, Germany; Primus, Drägerwerk AG; and Avance, GE-Datex-Ohemda, Munchen, Germany) had a triggering delay of less than 100 ms, which is considered clinically satisfactory and is comparable to intensive care unit machines. The use of positive end-expiratory pressure modified the quality of delivered pressure support for two anesthesia ventilators (Kion, Siemens AG, Munich, Germany; and Felix, Taema, Antony, France). Three of the five anesthesia ventilators exhibited pressure-support ventilation performance characteristics comparable to those of the intensive care unit machines. Increasing fresh gas flow (1 to 10 l/min) in the internal circuit did not influence the pressure-support ventilation performance of the anesthesia ventilators. Conclusion Regarding trigger sensitivity and the system's ability to meet inspiratory flow during pressure-supported breaths, the most recent anesthesia ventilators have comparable performances of recent-generation intensive care unit ventilators.

Objective: To evaluate the feasibility of using aknowledge-based system designed to automatically titrate pressure support (PS) to maintain the patient in a"respiratory comfort zone” during noninvasive ventilation (NIV) in patients with acute respiratory failure. Design and setting: Prospective crossover interventional study in an intensive care unit of auniversity hospital. Patients: Twenty patients. Interventions: After initial NIV setting and startup in conventional PS by the chest physiotherapist NIV was continued for 45 min with the automated PS activated. Measurements and results: During automated PS minute-volume was maintained constant while respiratory rate decreased significantly from its pre-NIV value (20 ± 3 vs. 25 ± 3 bpm). There was atrend towards aprogressive lowering of dyspnea. In hypercapnic patients PaCO2 decreased significantly from 61 ± 9 to 51 ± 2 mmHg, and pH increased significantly from 7.31 ± 0.05 to 7.35 ± 0.03. Automated PS was well tolerated. Two system malfunctions occurred prompting physiotherapist intervention. Conclusions: The results of this feasibility study suggest that the system can be used during NIV in patients with acute respiratory failure. Further studies should now determine whether it can improve patient-ventilator interaction and reduce caregiver workload

During pressure-support ventilation, the ventilator cycles into expiration when inspiratory flow decreases to a given percentage of peak inspiratory flow ("expiratory trigger"). In obstructive disease, the slower rise and decrease of inspiratory flow entails delayed cycling, an increase in intrinsic positive end-expiratory pressure, and nontriggering breaths.We hypothesized that setting expiratory trigger at a higher than usual percentage of peak inspiratory flow would attenuate the adverse effects of delayed cycling.Ten intubated patients with obstructive disease undergoing pressure support were studied at expiratory trigger settings of 10, 25, 50, and 70% of peak inspiratory flow.Continuous recording of diaphragmatic EMG activity with surface electrodes, and esophageal and gastric pressures with a dual-balloon nasogastric tube.Compared with expiratory trigger 10, expiratory trigger 70 reduced the magnitude of delayed cycling (0.25 +/- 0.18 vs. 1.26 +/- 0.72 s, p0.05), intrinsic positive end-expiratory pressure (4.8 +/- 1.9 vs. 6.5 +/- 2.2 cm H(2)O, p0.05), nontriggering breaths (2 +/- 3 vs. 9 +/- 5 breaths/min, p0.05), and triggering pressure-time product (0.9 +/- 0.8 vs. 2.1 +/- 0.7 cm H2O . s, p0.05).Setting expiratory trigger at a higher percentage of peak inspiratory flow in patients with obstructive disease during pressure support improves patient-ventilator synchrony and reduces inspiratory muscle effort. Further studies should explore whether these effects can influence patient outcome.

Objective Inspiratory pressure (Pi) support delivered by a bilevel device has become the technique of choice for noninvasive home ventilation. Considerable progress has been made in the performance and functionality of these devices. The present bench study was designed to compare the various characteristics of 10 recently developed bilevel Pi devices under different conditions of respiratory mechanics. Design Bench model study. Setting Research laboratory, university hospital. Measurements Ventilators were connected to a lung model, the mechanics of which were set to normal, restrictive, and obstructive, that was driven by an ICU ventilator to mimic patient effort. Pressure support levels of 10 and 15 cm H 2 O, and maximum were tested, with “patient” inspiratory efforts of 5, 10, 15, 20, and 25 cm H 2 O. Tests were conducted in the absence and presence of leaks in the system. Trigger delay, trigger-associated inspiratory workload, pressurization capabilities, and cycling were analyzed. Results All devices had very short trigger delays and triggering workload. Pressurization capability varied widely among the machines, with some bilevel devices lagging behind when faced with a high inspiratory demand. Cycling was usually not synchronous with patient inspiratory time when the default settings were used, but was considerably improved by modifying cycling settings, when that option was available. Conclusions A better knowledge of the technical performance of bilevel devices ( ie , pressurization capabilities and cycling profile) may prove to be useful in choosing the machine that is best suited for a patient's respiratory mechanics and inspiratory demand. Clinical algorithms to help set cycling criteria for improving patient-ventilator synchrony and patient comfort should now be developed.

To evaluate the feasibility of relying on a mathematical model to adjust the optimal level of expiratory trigger, materialized by the ratio of inspiratory flow at the end of inspiratory effort (V'ti) and peak inspiratory flow (V'peak), or V'ti/V'peak, during pressure support, by comparing its predicted values with those measured in intubated patients.Prospective observational study.Medical intensive care unit, university hospital.There were 28 intubated patients undergoing pressure support.Pressure support as set by the clinician in charge.A significant correlation was found between predicted and measured V'ti/V'peak ratios (r =.70; p.001; mean +/- sd difference, -0.025 +/- 0.07; 95% confidence interval, -0.161 to 0.111). Overall, delayed cycling occurred in obstructive conditions, the delay increasing as obstructive disease was more severe.A significant correlation was observed between predicted values of V'ti/V'peak and those values measured in patients undergoing pressure support. These findings should stimulate further research into the possible applications of this mathematical model to optimize expiratory trigger setting. Furthermore, our findings suggest that expiratory trigger should be adjustable and provide a wider range of cutoff levels than that which is currently available.

To the editor:H1N1 influenza infection is associated with severe forms of acuterespiratory distress syndrome (ARDS) with high mortality ratesamong younger subjects [1]. Evidence suggests improved outcomeswith the use of veno-venous extracorporeal membrane oxygenation(VV-ECMO) in the treatment of refractory hypoxemia associated withsevere cases of ARDS [2–5]. However, despite correct positioning ofthe cannulas and maximal ECMO blood flow, refractory hypoxemiamay persist. We describe how we improved arterial oxygenation of ayoungpatientwithsevereARDSbyreducingthepatient'snativecardiacoutput (CO) with beta-blockers.A 34-year old male, obese (BMI: 34), presented to the emergencydepartment with a history of fever, dyspnoea, cough and productivesputumworseningovertwoweeks.Atarrivalhewastachypneic,hemo-dynamicallystableandhemoglobinoxygensaturationwas89%inroomair. Chest radiography revealed right pulmonary infiltrates and bloodtestsweresignificantforleucopoenia,elevatedCRPandhighcreatinine.After 24 h of empiric treatment including oseltamivir, clarithromycineand ceftriaxone, the patient was admittedto intensive care with severeARDS. He was then sedated; intubated, paralyzed and low tidal volumeprotective lung ventilation with optimal PEEP was initiated. Corticoste-roids and inhaled nitric oxidewere alsostarted. Nasopharyngeal swabsrevealed influenza A infection.Despite recruitment maneuvers, PEEP 18–20 cm H

Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.

To compare the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation plus pressure support (SIMV-PS) on patient-ventilator interactions in patients undergoing partial ventilatory support.Prospective, crossover interventional study.Medical intensive care unit, university tertiary care center.Ten patients, intubated and mechanically ventilated for acute respiratory failure of diverse causes, in the early weaning period, ventilated with SIMV-PS and clinically detectable sternocleidomastoid activity suggesting increased inspiratory load and patient-ventilator dyssynchrony.Measurement of respiratory mechanics, P0.1, sternocleidomastoid electromyographic activity, arterial blood gases, and systemic hemodynamics in three conditions: 1) after 45 mins with SIMV-PS (SIMV-PS 1); 2) after 45 mins with ASV, set to deliver the same minute-ventilation as during SIMV-PS; 3) 45 mins after return to SIMV-PS (SIMV-PS 2), with settings identical to those of the first SIMV-PS period.The same minute ventilation was observed during ASV (11.4 +/- 3.1 l/min [mean +/- sd]) as during SIMV-PS 1 (11.6 +/- 3.5 L/min) and SIMV-PS 2 (10.8 +/- 3.4 L/min). No parameter was significantly different between SIMV-PS 1 and 2, hence subsequent results refer to ASV vs. SIMV-PS 1. During ASV, tidal volume increased (538 +/- 91 vs. 671 +/- 100 mL, p.05) and total respiratory rate decreased (22 +/- 7 vs. 17 +/- 3 breaths/min, p.05) vs. SIMV-PS. However, spontaneous respiratory rate increased in six patients, decreased in four, and remained unchanged in one. P0.1 decreased during ASV in all patients except three in whom no change was noted (1.8 +/- 0.9 vs. 1.1 +/- 1 cm H2O, p.05). During ASV, sternocleidomastoid electromyogram activity was markedly reduced (electromyogram index, where SIMV-PS 1 = 100, ASV 34 +/- 41, SIMV-PS 2 89 +/- 36, p.02) as was palpable muscle activity. No changes were noted in arterial blood gases, pH, or mean systemic pressure during the trial.In patients undergoing partial ventilatory support, with clinical and electromyographic signs of increased respiratory muscle loading, ASV provided levels of minute ventilation comparable to those of SIMV-PS. However, with ASV, central respiratory drive and sternocleidomastoid activity were markedly reduced, suggesting decreased inspiratory load and improved patient-ventilator interactions. These preliminary results warrant further testing of ASV for partial ventilatory support.

Objective: To test the hypothesis that replacing 70:30 nitrogen: oxygen (Air-O-2) with 70:30 helium:oxygen (He-O-2) can decrease dynamic hyperinflation ("Intrinsic" positive end-expiratory pressure) in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD), and to document the consequences of such an effect on arterial blood gases and hemodynamics. Design: Prospective, interventional study. Setting: Medical intensive care unit, university tertiary care center. Patients: Twenty-three intubated, sedated, paralyzed, and mechanically ventilated patients with COPD enrolled within 36 hrs after intubation. Interventions: Measurements were taken at the following time points, all with the same ventilator settings: a) baseline; b) after 45 mins with He-O-2; c) 45 mins after return to Air-O-2. The results were then compared to those obtained in a test lung model using the same ventilator settings. Main Results (mean +/- so):Trapped lung volume and intrinsic positive end-expiratory pressure decreased during He-O-2 ventilation (215 +/- 125 mL vs. 99 +/- 15 mL and 9 +/- 2.5 cm H2O vs. 5 +/- 2.7 cm H2O, respectively; p < .05). Likewise, peak and mean airway pressures declined with He-O-2 (30 +/- 5 cm H2O vs. 25 +/- 6 cm H2O and 8 +/- 2 cm H2O vs. 7 +/- 2 cm H2O, respectively; p < .05). These parameters all rose to their baseline values on return to Air-O-2 (p < .05 vs, values during He-O-2). These results were in accordance with those obtained in the test lung model. There was no modification of arterial blood gases, heart rate, or mean systemic arterial blood pressure. In 12/23 patients, a pulmonary artery catheter was in place, allowing hemodynamic measurements and venous admixture calculations. Switching to He-O-2 and back to Air-O-2 had no effect on pulmonary artery pressures, right and left ventricular filling pressures, cardiac output, pulmonary and systemic vascular resistance, or venous admixture. Conclusion: In mechanically ventilated COPD patients with intrinsic positive end-expiratory pressure, the use of He-O-2 can markedly reduce trapped lung volume, intrinsic positive end-expiratory pressure, and peak and mean airway pressures. No effect was noted on hemodynamics or arterial blood gases. He-O-2 might prove beneficial in this setting to reduce the risk of barotrauma, as well as to improve hemodynamics and gas exchange in patients with very high levels of intrinsic positive end-expiratory pressure. (Crit Care Med 2000; 28:2721-2728).

1. -Theoretical foundations 1. ⊎Physical properties of helium 2. ⊎Airway gas flow 3. ⊎Consequences for medical technology 4. -Clinical applications 1. ⊎Upper airway obstruction 2. ⊎Asthma 3. ⊎Chronic obstructive pulmonary disease 4. ⊎Others: 4.1. -bronchiolitis of the newborn 4.2. -aerosol therapy 4.3. -tracheal gas insufflation 4.4. -bronchoscopy 4.5. -high-frequency jet ventilation 5. -Logistical and technical aspects 5.1. ⊎Administration in spontaneous breathing 5.2. ⊎Administration in mechanical ventilation 5.3. ⊎Aerosols 6. -Cost

To test the hypothesis that, in decompensated chronic obstructive pulmonary disease (COPD), noninvasive pressure support ventilation using 70:30 helium:oxygen instead of 70:30 air:oxygen could reduce dyspnea and improve ventilatory variables, gas exchange, and hemodynamic tolerance.Prospective, randomized, crossover study.Medical intensive care unit, university tertiary care center.Nineteen patients with severe COPD (forced 1-sec expiratory volume of 0.83+/-0.3 l) hospitalized in the intensive care unit for noninvasive pressure support ventilation after initial stabilization with noninvasive pressure support for no more than 24 hrs after intensive care unit admission.Noninvasive pressure support ventilation was administered in the following randomized crossover design: a) 45 min with air:oxygen or helium:oxygen; b) no ventilation for 45 min; and c) 45 min with air:oxygen or helium:oxygen.Air:oxygen and helium:oxygen decreased respiratory rate and increased tidal volume and minute ventilation. Helium:oxygen decreased inspiratory time. Both gases increased total respiratory cycle time and decreased the inspiratory/total time ratio, the reduction in the latter being significantly greater with helium:oxygen. Peak inspiratory flow rate increased more with helium:oxygen. PaO2 increased with both gases, whereas PaCO2 decreased more with helium:oxygen (values shown are mean+/-SD) (52+/-6 torr [6.9+/-0.8 kPa] vs. 55+/-8 torr [7.3+/-1.1 kPa] and 48+/-6 torr [6.4+/-0.8 kPa] vs. 54+/-7 torr [7.2+/-0.9 kPa] for air:oxygen and helium:oxygen, respectively; p.05). When hypercapnia was severe (PaCO256 torr [7.5 kPa]), PaCO2 decreased byor =7.5 torr (1 kPa) in six of seven patients with helium:oxygen and in four of seven patients with air:oxygen (p.01). Dyspnea score (Borg scale) decreased more with helium:oxygen than with air:oxygen (3.7+/-1.6 vs. 4.5+/-1.4 and 2.8+/-1.6 vs. 4.6+/-1.5 for air:oxygen and helium:oxygen, respectively; p.05). Mean arterial blood pressure decreased with air:oxygen (76+/-12 vs. 82+/-14 mm Hg; p.05) but remained unchanged with helium:oxygen.In decompensated COPD patients, noninvasive pressure support ventilation with helium:oxygen reduced dyspnea and PaCO2 more than air:oxygen, modified respiratory cycle times, and did not modify systemic blood pressure. These effects could prove beneficial in COPD patients with severe acute respiratory failure and might reduce the need for endotracheal intubation.

Positive-pressure mechanical ventilation supports gas exchange in patients with respiratory failure but is also responsible for significant lung injury. In this study, we have developed an in vitro model in which isolated lung cells can be submitted to a prolonged cyclic pressure-stretching strain resembling that of conventional mechanical ventilation. In this model, cells cultured on a Silastic membrane were elongated up to 7% of their initial diameter, corresponding to a 12% increase in cell surface. The lung macrophage was identified as the main cellular source for critical inflammatory mediators such as tumor necrosis factor-α, the chemokines interleukin (IL)-8 and -6, and matrix metalloproteinase-9 in this model system of mechanical ventilation. These mediators were measured in supernatants from ventilated alveolar macrophages, monocyte-derived macrophages, and promonocytic THP-1 cells. Nuclear factor-κB was found to be activated in ventilated macrophages. Synergistic proinflammatory effects of mechanical stress and molecules such as bacterial endotoxin were observed, suggesting that mechanical ventilation might be particularly deleterious in preinjured or infected lungs. Dexamethasone prevented IL-8 and tumor necrosis factor-α secretion in ventilated macrophages. Mechanical ventilation induced low levels of IL-8 secretion by alveolar type II-like cells. Other lung cell types such as endothelial cells, bronchial cells, and fibroblasts failed to produce IL-8 in response to a prolonged cyclic pressure-stretching load. This model is of particular value for exploring physical stress-induced signaling pathways, as well as for testing the effects of novel ventilatory strategies or adjunctive substances aimed at modulating cell activation induced by mechanical ventilation.

Increased respiratory pattern variability is associated with improved oxygenation. Pressure support (PS) is a widely used partial-assist mechanical ventilation (MV) mode, in which each breathing cycle is initiated by flow or pressure variation at the airway due to patient inspiratory effort. Neurally adjusted ventilatory assist (NAVA) is relatively new and uses the electrical activity of the diaphragm (Eadi) to deliver ventilatory support proportional to the patient's inspiratory demand. We hypothesize that respiratory variability should be greater with NAVA compared with PS.

Neurally adjusted ventilatory assist or NAVA is a new assisted ventilatory mode which, in comparison with pressure support, leads to improved patient-ventilator synchrony and a more variable ventilatory pattern. It also improves arterial oxygenation. With NAVA, the electrical activity of the diaphragm is recorded through a nasogastric tube equipped with electrodes. This electrical activity is then used to pilot the ventilator. With NAVA, the patient's respiratory pattern controls the ventilator's timing of triggering and cycling as well as the magnitude of pressurization, which is proportional to inspiratory demand. The effect of NAVA on patient outcome remains to be determined through well-designed prospective studies.

An online algorithm for determining respiratory mechanics in patients using non-invasive ventilation (NIV) in pressure support mode was developed and embedded in a ventilator system. Based on multiple linear regression (MLR) of respiratory data, the algorithm was tested on a patient bench model under conditions with and without leak and simulating a variety of mechanics. Bland-Altman analysis indicates reliable measures of compliance across the clinical range of interest (± 11-18% limits of agreement). Resistance measures showed large quantitative errors (30-50%), however, it was still possible to qualitatively distinguish between normal and obstructive resistances. This outcome provides clinically significant information for ventilator titration and patient management.

Halogenated gases have sometimes been used for treating acute severe asthma when this disorder is refractory to any drug. Presently, we only can rely on some sparsed observations, or to small retrospective series. Isoflurane seems to be the most studied gas: it has clearly a bronchodilating action, and its side-effects seem to be minor. However, to administer such medications, precise knowledge and technical skills are mandatory. In addition, the intensive care personnel must be protected from an accidental exposure. Therefore, intensive care physicians should be helped by an experienced anesthesiologist when using these gases.

An automated classification algorithm for the detection of expiratory ineffective efforts in patient-ventilator interaction is developed and validated. Using this algorithm, 5624 breaths from 23 patients in a pulmonary ward were examined. The participants (N = 3D23) underwent both conventional and non-invasive ventilation. Tracings of patient flow, pressure at the airway, and transdiaphragmatic pressure were manually labeled by an expert. Overall accuracy of 94.5% was achieved with sensitivity 58.7% and specificity 98.7%. The results demonstrate the viability of using pattern classification techniques to automatically detect the presence of asynchrony between a patient and their ventilator.

To determine the prevalence of patient-ventilator asynchrony in patients receiving non-invasive ventilation (NIV) for acute respiratory failure. Prospective multicenter observation study. Intensive care units in three university hospitals. Patients consecutively admitted to ICU were included. NIV, performed with an ICU ventilator, was set by the clinician. Airway pressure, flow, and surface diaphragmatic electromyography were recorded continuously for 30 min. Asynchrony events and the asynchrony index (AI) were determined from visual inspection of the recordings and clinical observation. A total of 60 patients were included, 55% of whom were hypercapnic. Auto-triggering was present in 8 (13%) patients, double triggering in 9 (15%), ineffective breaths in 8 (13%), premature cycling 7 (12%) and late cycling in 14 (23%). An AI > 10%, indicating severe asynchrony, was present in 26 patients (43%), whose median (25-75 IQR) AI was 26 (15-54%). A significant correlation was found between the magnitude of leaks and the number of ineffective breaths and severity of delayed cycling. Multivariate analysis indicated that the level of pressure support and the magnitude of leaks were weakly, albeit significantly, associated with an AI > 10%. Patient comfort scale was higher in pts with an AI < 10%. Patient-ventilator asynchrony is common in patients receiving NIV for acute respiratory failure. Our results suggest that leaks play a major role in generating patient-ventilator asynchrony and discomfort, and point the way to further research to determine if ventilator functions designed to cope with leaks can reduce asynchrony in the clinical setting.

In acute severe asthma, the use of heliox can reduce dyspnea, when the patient is spontaneously breathing as well as in mechanical ventilation. This effect is due to a decrease in airway resistance. A better penetration of aerosolized bronchodilators has also been observed. However, the clinical benefit of these physiological measurable effects remains undetermined. Heliox could nevertheless be interesting in emergency situations in order to avoid endotracheal intubation, and in very difficult cases when mechanical ventilation is almost impossible to perform. This gas mixture could also be used with non-invasive mechanical ventilation, but this indication is presently investigated.

Mechanically ventilated patients with chronic obstructive pulmonary disease often prove challenging to the clinician due to the complex pathophysiology of the disease and the high risk of patient-ventilator asynchrony. These problems are encountered in both intubated patients and those ventilated with noninvasive ventilation. Much knowledge has been gained over the years in our understanding of the mechanisms underlying the difficult interaction between these patients and the machines used to provide them with the ventilatory support they often require for prolonged periods. This paper attempts to summarize the various key issues of patient-ventilator interaction during pressure support ventilation, the most often used partial ventilatory support mode, and to draw clinicians' attention to the need for sufficient knowledge when setting the ventilator at the bedside, given the often conflicting goals that must be met.

Inspiratory pressure (Pi) support delivered by a bilevel device has become the technique of choice for noninvasive home ventilation. Considerable progress has been made in the performance and functionality of these devices. The present bench study was designed to compare the various characteristics of 10 recently developed bilevel Pi devices under different conditions of respiratory mechanics.Bench model study.Research laboratory, university hospital.Ventilators were connected to a lung model, the mechanics of which were set to normal, restrictive, and obstructive, that was driven by an ICU ventilator to mimic patient effort. Pressure support levels of 10 and 15 cm H(2)O, and maximum were tested, with "patient" inspiratory efforts of 5, 10, 15, 20, and 25 cm H(2)O. Tests were conducted in the absence and presence of leaks in the system. Trigger delay, trigger-associated inspiratory workload, pressurization capabilities, and cycling were analyzed.All devices had very short trigger delays and triggering workload. Pressurization capability varied widely among the machines, with some bilevel devices lagging behind when faced with a high inspiratory demand. Cycling was usually not synchronous with patient inspiratory time when the default settings were used, but was considerably improved by modifying cycling settings, when that option was available.A better knowledge of the technical performance of bilevel devices (ie, pressurization capabilities and cycling profile) may prove to be useful in choosing the machine that is best suited for a patient's respiratory mechanics and inspiratory demand. Clinical algorithms to help set cycling criteria for improving patient-ventilator synchrony and patient comfort should now be developed.

Using multiplane transoesophageal echocardiography (TOE), we investigated the haemodynamic response to acute normovolaemic haemodilution (ANH) in anaesthetised patients with critical aortic stenosis. Twenty-eight patients were randomly assigned to ANH or control groups. In the control group, haemodynamic data remained unchanged over a 20-min period. In the ANH group, haemoglobin levels decreased from a mean (SD) of 134 (7) to 91 (9) g x l(-1) (p < 0.001) whereas stroke volume, central venous pressure and left ventricular (LV) end-diastolic area all increased significantly (mean (SD) +15 (6) ml; +2.0 (1.1) mmHg; +2.1 (0.8) cm2, respectively). During ANH, the accelerated blood flow through the stenotic valve caused an increased loss (SD) in LV stroke work: from 24 (8)% to 30 (10)%), (p < 0.01). Hence, lowering viscosity with ANH resulted in improved venous return, higher cardiac preload and increased stroke volume. However, this adaptive haemodynamic response was limited by less efficient LV stroke work due to dissipation of fluid kinetic energy.

Transoesophageal Doppler monitoring allows non-invasive assessment of stroke volume. We studied haemodynamic changes during acute normovolemic haemodilution (ANH) in anaesthetised patients with coronary artery disease. Twenty patients were randomly assigned to either ANH or a control group. During ANH, a mean (SD) blood volume of 15.3 (3.4) ml.kg(-1) was withdrawn decreasing systemic oxygen delivery from 12.7 (3.3) to 9.3 (1.8) ml.kg(-1).min(-1) (p < 0.001). In the control group, haemodynamic data remained unchanged, whereas in the ANH group, stroke volume and central venous pressure increased significantly (mean = +21 ml [95% CI: 18-25 ml.min(-1)]; mean = +2.5 mmHg [95% CI: 2.2-2.8 mmHg], respectively) and heart rate decreased (mean = -6 beat.min(-1)[95% CI: 6-8 beat.min(-1)], p < 0.05). According to the Frank-Starling relationship, individual changes in stroke volume compared with central venous pressure fitted a quadratic regression model (R2 > 0.91). A reduced viscosity associated with ANH resulted in improved venous return, higher cardiac preload and increased cardiac output. In summary, this study demonstrated that ANH to a haemoglobin value of 8.6 g.dl(-1) was well tolerated in patients with coronary artery disease.

The density of helium is markedly lower than that of air or any of its components, leading to a substantial decrease in airway resistance to flow when it is inhaled. In mechanically ventilated patients with obstructive airway disease, replacing the usual air-oxygen mixture with helium-oxygen has been shown to reduce dynamic hyperinflation and intrinsic positive end-expiratory pressure; to decrease lung inflation pressures, respiratory acidosis, and work of breathing; and to improve arterial blood gases. Aerosol delivery to distal airways is enhanced with helium-oxygen. Preliminary data also suggest that the use of helium-oxygen could be a valuable approach to decrease postextubation respiratory distress. However, interference with ventilator function and added costs are two major disadvantages of helium-oxygen. Hence, before its widespread use in mechanically ventilated patients can be recommended, studies are needed to determine whether these favorable short-term effects can influence patient outcome.

We analyzed a local database including 468 consecutive patients who underwent elective aortic abdominal surgery over an 8-yr period in a single institution. A new cardioprotective perioperative protocol was introduced in January 1997, and we questioned whether perioperative cardiac outcome could be favorably influenced by the application of a stepwise cardiovascular evaluation based on the American College of Cardiology/American Heart Association guidelines and by the use of antiadrenergic drugs. Clonidine was administered during surgery, and beta-blockers were titrated after surgery to achieve heart rates less than 80 bpm. We compared data of two consecutive 4-yr periods (1993-1996 [control period] versus 1997-2000 [intervention period]). Implementation of American College of Cardiology/American Heart Association guidelines was associated with increased preoperative myocardial scanning (44.3% vs 20.6%; P0.05) and coronary revascularization (7.7% vs 0.8%; P0.05). During the intervention period, there was a significant decrease in the incidence of cardiac complications (from 11.3% to 4.5%) and an increase in event-free survival at 1 yr after surgery (from 91.3% to 98.2%). Multivariate regression analysis showed that the combined administration of clonidine and beta-blockers was associated with a decreased risk of cardiovascular events (odds ratio, 0.3; 95% confidence interval, 0.1-0.8), whereas major bleeding, renal insufficiency, and chronic obstructive pulmonary disease were predictive of cardiac complications. In conclusion, cardiac testing was helpful to identify a small subset of high-risk patients who might benefit from coronary revascularization. Sequential and selective antiadrenergic treatments were associated with improved postoperative cardiac outcome.Implementation of American College of Cardiology/American Heart Association guidelines and use of antiadrenergic drugs were associated with better cardiac outcomes after major vascular surgery.

Ex utero intrapartum treatment (EXIT) of a fetus with severe bilateral hydrothorax is described. EXIT allows therapeutic interventions on the neonate while maintaining fetoplacental circulation. Thus it may be useful for fetuses presenting with severe pleural effusion towards the end of gestation and in whom in utero drainage is technically not possible or available and drainage post partum would result in profound and prolonged hypoxia until sufficient drainage of pleural fluid allowed lung expansion.

To compare triggering, pressurization, and cycling of the home ventilator VPAP II with those of three ICU ventilators (Evita 4, Galileo, and Servo 300).Two-compartment lung model study in a research laboratory, university hospital.One compartment was driven by an ICU ventilator to mimic "patient" inspiratory effort, while the other was connected to the tested ventilator. Pressure support of 10, 15, 20, and 25 cmH2O, and inspiratory efforts of 5, 10, 15, 20, and 25 cmH2O (inspiratory time 1 s) were used in normal, obstructive, and restrictive conditions. Triggering delay (Td), triggering workload, pressurization at 300 and 500 ms, and difference between the "patient's" inspiratory time and that of the ventilator were analyzed.No difference was noted in triggering workload between VPAP II, Evita 4, and Galileo while Servo 300 had a lower value. Pressurization at 300 ms on Evita 4 and Servo 300 reached 75% of the ideal value, on Galileo 35%, and on VPAP II 45%. Pressurization at 500 ms on Evita 4 and Servo 300 reached 85% of the ideal value, on Galileo 50%, and on VPAP II 55%. Cycling was delayed in obstructive conditions and premature in restrictive conditions with each of the devices.The VPAP II performed as well as one ICU ventilator and less well than two. Home devices for noninvasive ventilation in acute respiratory failure outside the ICU could prove attractive as they are smaller, less costly, and easier to use than ICU machines.