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Byline: Armand Mekontso Dessap (1,2,3,5), Cyril Charron (4), Jerome Devaquet (1), Jerome Aboab (1), Francois Jardin (4), Laurent Brochard (1,2,3), Antoine Vieillard-Baron (4) Keywords: Lung injury; Acidosis; Right heart; Alveolar recruitment; Alveolar dead space Abstract: Purpose To evaluate the effects of acute hypercapnia induced by positive end-expiratory pressure (PEEP) variations at constant plateau pressure (P .sub.plat) in patients with severe acute respiratory distress syndrome (ARDS) on right ventricular (RV) function. Methods Prospective observational study in two academic intensive care units enrolling 11 adults with severe ARDS (PaO.sub.2/FiO.sub.2 5 cm[H.sub.2]O). We compared three ventilatory strategies, each used for 1 h, with P .sub.plat at 22 (20--25) cm[H.sub.2]O: low PEEP (5.4 cm[H.sub.2]O) or high PEEP (11.0 cm[H.sub.2]O) with compensation of the tidal volume reduction by either a high respiratory rate (high PEEP/high rate) or instrumental dead space decrease (high PEEP/low rate). We assessed RV function (transesophageal echocardiography), alveolar dead space (expired CO.sub.2), and alveolar recruitment (pressure--volume curves). Results Compared to low PEEP, PaO.sub.2/FiO.sub.2 ratio and alveolar recruitment were increased with high PEEP. Alveolar dead space remained unchanged. Both high-PEEP strategies induced higher PaCO.sub.2 levels [71 (60--94) and 75 (53--84), vs. 52 (43--68) mmHg] and lower pH values [7.17 (7.12--7.23) and 7.20 (7.16--7.25) vs. 7.30 (7.24--7.35)], as well as RV dilatation, LV deformation and a significant decrease in cardiac index. The decrease in stroke index tended to be negatively correlated to the increase in alveolar recruitment with high PEEP. Conclusions Acidosis and hypercapnia induced by tidal volume reduction and increase in PEEP at constant P .sub.plat were associated with impaired RV function and hemodynamics despite positive effects on oxygenation and alveolar recruitment ( ClinicalTrials.gov NCT00236262). Author Affiliation: (1) Medical Intensive Care Unit, Assistance Publique-Hopitaux de Paris, Henri Mondor--Albert Chenevier Teaching Hospital, Creteil, France (2) INSERM Unite 955, IMRB, Equipe 8, Creteil, France (3) Paris XII University, Creteil, France (4) Medical Intensive Care Unit, Assistance Publique-Hopitaux de Paris, Ambroise Pare Teaching Hospital, Boulogne-Billancourt, France (5) Service de Reanimation Medicale, CHU Henri Mondor, 51 avenue du Mal de Lattre de Tassigny, 94010, Creteil Cedex, France Article History: Registration Date: 19/06/2009 Received Date: 20/10/2008 Accepted Date: 23/05/2009 Online Date: 04/08/2009 Article note: C. Charron and J. Devaquet contributed equally to this work. This article is discussed in the editorial available at: doi: 10.1007/s00134-009-1571-8.

Byline: Ido G. Bikker (1), Thierry V. Scohy (2), Ad J. J. C. Bogers (3), Jan Bakker (1), Diederik Gommers (1,2) Keywords: Functional residual capacity; Pediatric; Positive-pressure respiration; Lung volume measurements; Anesthesiology Abstract: Purpose Monitoring end-expiratory lung volume (EELV) is a valuable tool to optimize respiratory settings that could be of particular importance in mechanically ventilated pediatric patients. We evaluated the feasibility and precision of an intensive care unit (ICU) ventilator with an in-built nitrogen washout/washin technique in mechanically ventilated pediatric patients. Methods Duplicate EELV measurements were performed in 30 patients between 5 kg and 43 kg after cardiac surgery (age, median + range: 26, 3--141 months). All measurements were taken during pressure-controlled ventilation at 0 cm [H.sub.2]O of positive end-expiratory pressure (PEEP). Results Linear regression between duplicate measurements was excellent (R .sup.2 = 0.99). Also, there was good agreement between duplicate measurements, bias +- SD: -0.3% (-1.5 mL) +- 5.9% (19.2 mL). Mean EELV +- SD was 19.6 +- 5.1 mL/kg at 0 cm [H.sub.2]O PEEP. EELV correlated with age (p < 0.001, r = 0.92, R .sup.2 = 0.78), body weight (p < 0.001, r = 0.91, R .sup.2 = 0.82) and height (p < 0.001, r = 0.94, R .sup.2 = 0.75). Conclusion This ICU ventilator with an in-built nitrogen washout/washin EELV technique can measure EELV with precision, and can easily be used for mechanically ventilated pediatric patients. Author Affiliation: (1) Department of Intensive Care Medicine, Erasmus MC, Room H602, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands (2) Department of Anesthesiology, Erasmus MC, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands (3) Department of Cardiothoracic Surgery, Erasmus MC, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands Article History: Registration Date: 08/07/2009 Received Date: 15/12/2008 Accepted Date: 20/06/2009 Online Date: 23/07/2009

Byline: Arnaud W. Thille (1), Belen Cabello (1), Fabrice Galia (1), Aissam Lyazidi (1), Laurent Brochard (1) Keywords: Patient-ventilator asynchrony; Patient-ventilator interaction; Assisted mechanical ventilation; Pressure-support ventilation; Work of breathing Abstract: Objective To identify ventilatory setting adjustments that improve patient-ventilator synchrony during pressure-support ventilation in ventilator-dependent patients by reducing ineffective triggering events without decreasing tolerance. Design and setting Prospective physiological study in a 13-bed medical intensive care unit in a university hospital. Patients and participants Twelve intubated patients with more than 10% of ineffective breaths while receiving pressure-support ventilation. Interventions Flow, airway-pressure, esophageal-pressure, and gastric-pressure signals were used to measure patient inspiratory effort. To decrease ineffective triggering the following ventilator setting adjustments were randomly adjusted: pressure support reduction, insufflation time reduction, and change in end-expiratory pressure. Measurements and results Reducing pressure support from 20.0a-cm [H.sub.2]O (IQR 19.5--20) to 13.0 (12.0--14.0) reduced tidal volume [10.2a-ml/kg predicted body weight (7.2--11.5) to 5.9 (4.9--6.7)] and minimized ineffective triggering events [45% of respiratory efforts (36--52) to 0% (0--7)], completely abolishing ineffective triggering in two-thirds of patients. The ventilator respiratory rate increased due to unmasked wasted efforts, with no changes in patient respiratory rate [26.5a-breaths/min (23.1--31.9) vs. 29.4 (24.6--34.5)], patient effort, or arterial PCO.sub.2. Shortening the insufflation time reduced ineffective triggering events and patient effort, while applying positive end-expiratory pressure had no influence on asynchrony. Conclusions Markedly reducing pressure support or inspiratory duration to reach a tidal volume of about 6a-ml/kg predicted body weight eliminated ineffective triggering in two-thirds of patients with weaning difficulties and a high percentage of ineffective efforts without inducing excessive work of breathing or modifying patient respiratory rate. Author Affiliation: (1) Medical Intensive Care Unit, Henri Mondor Teaching Hospital, AP-HP, INSERM U841, Paris XII University, 51 avenue du Marechal de Lattre de Tassigny, 94010, Creteil, France Article History: Registration Date: 31/03/2008 Received Date: 15/11/2007 Accepted Date: 27/03/2008 Online Date: 24/04/2008

Byline: Fabrizio Racca (1), Lorenzo Appendini (2), Cesare Gregoretti (3), Ilaria Varese (1), Giacomo Berta (1), Ferdinando Vittone (1), Gabriela Ferreyra (1), Elisa Stra (1), V. Marco Ranieri (1) Keywords: Noninvasive ventilation; Pressure support ventilation; Continuous positive airway pressure; Carbon dioxide rebreathing; Helmet; Air leaks Abstract: Objective We examined whether additional helmet flow obtained by a single-circuit and a modified plateau valve applied at the helmet expiratory port (open-circuit ventilators) improves CO.sub.2 wash-out by increasing helmet airflow. Design and setting Randomized physiological study in a university research laboratory. Participants Ten healthy volunteers. Interventions Helmet continuous positive airway pressure and pressure support ventilation delivered by an ICU ventilator (closed-circuit ventilator) and two open-circuit ventilators equipped with a plateau valve placed either at the inspiratory or at the helmet expiratory port. Measurements and results We measured helmet air leaks, breathing pattern, helmet minute ventilation ( .sub.Eh), minute ventilation washing the helmet ( .sub.Ewh), CO.sub.2 wash-out, and ventilator inspiratory assistance. Air leaks were small and similar in all conditions. Breathing pattern was similar among the different ventilators. Inspiratory and end-tidal CO.sub.2 were lower, while .sub.Eh and .sub.Ewh were higher only using open-circuit ventilators with the plateau valve placed at the helmet expiratory port. This occurred notwithstanding these ventilators delivered a lower inspiratory assistance. Conclusions Additional helmet flow provided by open-circuit ventilators can lower helmet CO.sub.2 rebreathing. However, inspiratory pressure assistance significantly decreases using open-circuit ventilators, still casting doubts on the choice of the optimal helmet ventilation setup. Author Affiliation: (1) Dipartimento di Anestesia e Rianimazione, Universita di Torino, Ospedale S. Giovanni Battista-Molinette, Turin, Italy (2) Divisione di Pneumologia, Fondazione Salvatore Maugeri, IRCCS, Istituto Scientifico di Veruno, Via Revislate, n. 13, 28010, Veruno, Italy (3) Servizio di Anestesia e Rianimazione, Azienda Ospedaliera CTO-CRF-Maria Adelaide, Turin, Italy Article History: Registration Date: 27/03/2008 Received Date: 25/09/2007 Accepted Date: 24/03/2008 Online Date: 06/05/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1120-x) contains supplementary material, which is available to authorized users.

Low tidal volume (Vt) ventilation is protective against ventilator-induced lung injury but can promote development of atelectasis. Periodic deep inflation (DI) can open the lung, but if delivered too frequently may cause damage via repeated overdistention. We therefore examined the effects of varying DI frequency on lung mechanics, gas exchange, and biomarkers of injury in mice. C57BL/6 males were mechanically ventilated with positive end-expiratory pressure (PEEP) of 2 cm[H.sub.2]O for 2 h. One high Vt group received a DI with each breath (HV). Low Vt groups received 2 DIs after each hour of ventilation (LV) or 2 Dis every minute (LVDI). Control groups included a nonventilated surgical sham and a group receiving high Vt with zero PEEP (HVZP). Respiratory impedance was measured every 4 min, from which tissue elastance (H) and damping (G) were derived. G and H rose progressively during LV and HVZP, but returned to baseline after hourly DI during LV. During LVDI and HV, G and H remained low and gas exchange was superior to that of LV. Bronchoalveolar lavage fluid protein was elevated in HV and HVZP but was not different between LV and LVDI. Lung tissue IL-6 and IL-1[beta] levels were elevated in HVZP and lower in LVDI compared with LV. We conclude that frequent DI can safely improve gas exchange and lung mechanics and may confer protection from biotrauma. Differences between LVDI and HV suggest that an optimal frequency range of DI exists, within which the benefits of maintaining an open lung outweigh injury incurred from overdistention. recruitment; lung mechanics; respiratory impedance

Byline: Pierre Emmanuel Charles (1), Laurent Martin (2), Manuel Etienne (1), Delphine Croisier (1), Lionel Piroth (1), Catherine Lequeu (1), Jerome Pugin (3), Henri Portier (1), Pascal Chavanet (1) Keywords: Ventilator-associated pneumonia; Animal model; Ventilation-induced lung injury; Positive end-expiratory pressure Abstract: Objective Ventilatory strategies combining low tidal volume (V.sub.T) with positive end-expiratory pressure (PEEP) are considered to be lung protective. The influence of the PEEP level was investigated on bacteriology and histology in a model of ventilator-associated pneumonia. Subjects Nineteen New Zealand rabbits. Interventions The animals were mechanically ventilated with a positive inspiratory pressure of 15 cm[H.sub.2]O and received either a zero end-expiratory pressure (ZEEP, n=6), a 5 cm[H.sub.2]O PEEP (n=5) or a 10 cm[H.sub.2]O PEEP (n=4). An inoculum of Enterobacter aerogenes was then instilled intrabronchially. The non-ventilated pneumonia group (n=4) was composed of spontaneously breathing animals which received the same inoculum. Pneumonia was assessed 24 h later. Main results The lung bacterial burden was higher in mechanically ventilated animals compared with spontaneously breathing animals. All animals from the latter group had negative spleen cultures. The spleen bacterial concentration was found to be lower in the 5 cm[H.sub.2]O PEEP group when compared to the ZEEP and 10 cm[H.sub.2]O PEEP groups (3.1+-1.5 vs 4.9+-1.1 and 5.0+-1.3 log.sub.10 cfu/g, respectively p Conclusions Mechanical ventilation substantially increased the lung bacterial burden and worsened the histological aspects of pneumonia in this rabbit model. Variations in terms of lung injury and systemic spreading of infection were noted with respect to the ventilatory strategy. Author Affiliation: (1) Laboratoire des Maladies Infectieuses, EA562, Dijon University Hospital, Boulevard Mal de Lattre de Tassigny, 21033, Dijon, France (2) Laboratoire d'Anatomo-Pathologie, Faculty of Medicine, Dijon, France (3) Soins Intensifs de Medecine, University Hospital of Geneva, Geneva, Switzerland Article History: Registration Date: 26/08/2004 Received Date: 27/02/2004 Accepted Date: 24/08/2004 Online Date: 04/11/2004 Article note: Presented in January 2004 at the Congress of the French Society of Critical Care Medicine.

Byline: Raffaele Scala (1), Sandra Bartolucci (2), Mario Naldi (1), Marcello Rossi (3), Mark W. Elliott (4) Keywords: Co-morbidities; Chronic obstructive pulmonary disease; Acute hypercapnic respiratory failure; Non-invasive positive pressure ventilation; Charlson index Abstract: Objective To assess the prevalence and the impact of chronic and/or acute non-respiratory co-morbidity on short and longer-term outcome of non-invasive positive pressure ventilation (NIPPV) in acute decompensations of chronic obstructive pulmonary disease (COPD) with acute hypercapnic respiratory failure (AHRF). Design and setting An observational study in a three-bed respiratory monitoring unit in a respiratory ward of a non-university hospital. Patients We grouped 120 consecutive COPD patients requiring NIPPV for AHRF (pH 7.28+-0.05, PaO.sub.2/FIO.sub.2 ratio 192+-63, PaCO.sub.2 78.3+-12.3 mmHg) according to whether NIPPV succeeded (n=98) or failed (n=22) in avoiding the need for endotracheal intubation and whether alive (n=77) or dead (n=42) at 6 months. Measurements and results The prevalence of chronic and acute co-morbidity was, respectively, 20% and 41.7% most of the cases were cardiovascular. In-hospital NIPPV failure was greater in patients with than in those without chronic (33.3% vs. 14.6%) or acute co-morbidity (32% vs. 8.6%). Six-month mortality was worse in patients with than in those without chronic (54.2% vs. 30.5%) or more than one acute co-morbidity (66.7% vs. 30.8%). Multiple regression analysis predicted in-hospital NIPPV failure by acute co-morbidity and forced expiratory volume in 1 s, while death at 6 months was predicted by having more than one acute co-morbidity, non-cardiovascular chronic co-morbidity and Activities of Daily Living score. Conclusions Chronic and acute co-morbidities are common in COPD patients with AHRF needing NIPPV and their presence influences short and longer-term outcome. Author Affiliation: (1) U.O. Pneumologia, USL8, Ospedale S. Donato, Via Nenni 20, 52100, Arezzo, Italy (2) U.O. Sistema Informativo, Via Fonte Veneziana 16, 52100, Arezzo, Italy (3) U.O. Fisiopatologia e Riabilitazione Respiratoria, Azienda Ospedaliera Senese, Siena, Italy (4) Department of Respiratory Medicine, St. James's University Hospital, Beckett Street, Leeds, LS9 7TF, UK Article History: Registration Date: 11/06/2004 Received Date: 13/02/2004 Accepted Date: 01/06/2004 Online Date: 17/07/2004

Byline: Enzo Squadrone (1), Pamela Frigerio (2), Claudio Fogliati (1), Cesare Gregoretti (3), Giorgio Conti (4), Massimo Antonelli (4), Roberta Costa (4), Paola Baiardi (5), Paolo Navalesi (6) Keywords: Noninvasive positive pressure ventilation; Respiratory failure; Chronic obstructive lung disease; Intensive care; Endotracheal intubation Abstract: Objective To determine whether non-invasive ventilation (NIV) may be an effective and safe alternative to invasive mechanical ventilation in chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF) meeting criteria for mechanical ventilation. Design and setting Matched case-control study conducted in ICU. Patients and intervention NIV was prospectively applied to 64 COPD patients with advanced ARF. Their outcomes were compared with those of a control group of 64 COPD patients matched on age, FEV.sub.1, Simplified Acute Physiology Score II, and pH at ICU admission, previously treated in the same ICU with conventional invasive mechanical ventilation. Methods and results NIV failed in 40 patients who required intubation. Mortality rate, duration of mechanical ventilation, and lengths of ICU and post-ICU stay were not different between the two groups. The NIV group had fewer complications (P = 0.01) and showed a trend toward a lower proportion of patients remaining on mechanical ventilation after 30 days (P = 0.056). Compared to the control group, the outcomes of the patients who failed NIV were no different. Compared to the patients who received intubation, those who succeeded NIV had reduced mortality rate and lengths of ICU and post-ICU stay. Conclusions In COPD patients with advanced hypercapnic acute respiratory failure, NIV had a high rate of failure, but, nevertheless, provided some advantages, compared to conventional invasive ventilation. Subgroup analysis suggested that the delay in intubation was not deleterious in the patients who failed NIV, whereas a better outcome was confirmed for the patients who avoided intubation. Author Affiliation: (1) ICU, Azienda Ospedaliera S.Luigi Gonzaga, Orbassano, Italy (2) Dipartimento di Emergenza-Urgenza, Azienda Ospedaliera Ca' Granda Niguarda, Milan, Italy (3) ICU, Azienda Ospedaliera CTO-CRF-Maria Adelaide, Turin, Italy (4) Istituto di Anestesia e Rianimazione, Universita Cattolica del Sacro Cuore, Rome, Italy (5) Servizio di Biostatistica, Fondazione S. Maugeri, Pavia, Italy (6) Pneumologia e Terapia Intensiva Respiratoria, Fondazione S. Maugeri, Via Ferrata 8, 27100 , Pavia, Italy Article History: Registration Date: 02/04/2004 Received Date: 23/12/2003 Accepted Date: 02/04/2004 Online Date: 12/06/2004

The effect of noninvasive positive-pressure ventilation on mortality is evaluated by conducting a multicenter, randomized trial. The findings reveal that noninvasive positive-pressure ventilation does not prevent the need for reintubation or reduce mortality in unselected patients who have respiratory failure after extubation.

Byline: Stephanie Delaere (1), Jean Roeseler (1), William D'hoore (1), Pascal Matte (1), Marc Reynaert (1), Philippe Jolliet (2), Thierry Sottiaux (3), Giuseppe Liistro (4) Keywords: Proportional assist ventilation Pressure support ventilation Work of breathing Abstract: Objective. To compare the respiratory muscle workload associated with pressure support ventilation (PSV) and proportional assist ventilation (PAV) in intubated and spontaneously breathing patients without COPD. Design and setting. Prospective study, intensive care unit university hospital. Interventions. Twenty intubated patients, during early weaning, PSV settings made by clinician in charge of the patient, and two levels of PAV, set to counterbalance 80% (PAV 80) and 50% (PAV 50) of both elastic and resistive loads, respectively. The patients were ventilated in the following order: 1) PSV 2) PAV 50 or PAV 80 3) PSV 4) PAV 80 or PAV 50 5) PSV. PSV settings were kept constant. Measurements. Arterial blood gases, breathing pattern and respiratory effort parameters at the end of each of the five steps. Main results. PSV and PAV 80 had the same effects on work of breathing (WOB). The pressure-time product (PTP) was significantly higher during PAV 80 than during PSV (90+-76 and 61+-56 cm[H.sub.2]O*s*min.sup.-1, respectively, P Conclusion. In a group of intubated spontaneously breathing non-COPD patients, PAV 80 and PSV were associated with comparable levels WOB, whereas PTP was higher during PAV 80. PAV 50 provided insufficient respiratory assistance. Author Affiliation: (1) Intensive Care Department, Cliniques Universitaires St Luc, Universite Catholique de Louvain, Brussels, Belgium (2) Intensive Care Unit, Medical ICU Division, University Hospital, Geneva, Switzerland (3) , Clinique Notre-Dame de Grace, Gosselies, Belgium (4) Pneumology Unit, Cliniques Universitaires St Luc (UCL), Universite Catholique de Louvain, 10 Avenue Hippocrate, 1200, Brussels, Belgium Article History: Received Date: 22/01/2002 Accepted Date: 14/02/2003 Article note: Electronic Publication

Byline: Wolfram Windisch (1), Klaus Freidel (2), Bernd Schucher (3), Hansjorg Baumann (4), Matthias Wiebel (5), Heinrich Matthys (1), Franz Petermann (6) Keywords: Chronic obstructive pulmonary disease Chronic respiratory failure Health-related quality of life Home mechanical ventilation Kyphoscoliosis Noninvasive positive pressure ventilation Abstract: Objective. To collect benchmark data on the MOS 36-Item Short-Form Health Status Survey (SF-36) in patients receiving noninvasive positive pressure ventilation and to examine whether health-related quality of life is influenced by the underlying disease or by physical parameters. Design and setting. Multicentric clinical cross-sectional trial in four general wards specialized in noninvasive positive pressure ventilation. Patients and participants. 226 patients (78 chronic obstructive pulmonary disease, 57 kyphoscoliosis, 20 posttuberculosis sequelae, 17 Duchenne muscular dystrophy, 13 polyneuropathy, 13 myopathy, 6 amyotrophic lateral sclerosis, 12 obesity-hypoventilation syndrome, 4 poliomyelitis sequelae, 3 phrenic nerve lesion, 3 central hypoventilation syndrome) who used noninvasive positive pressure ventilation for home mechanical ventilation. Measurements and results. Health-related quality of life as assessed by the SF-36 was lower than in the general population. Overall the Physical Component Summary (PCS) was significantly lower than the general population norm the Mental Component Summary (MCS) was also reduced but less markedly. Patients with chronic obstructive pulmonary disease were more impaired in MCS than those with kyphoscoliosis. PCS was significantly associated with age. Gender, lung function, and arterial blood gas values were not significant predictors of health-related quality of life. Conclusions. Benchmark SF-36 data in patients receiving noninvasive positive pressure ventilation are given. Although physical health is significantly impaired in these patients, this does not necessarily lead to mental limitation, and mental health is influenced by the underlying disease, but not by physical parameters. Author Affiliation: (1) Department of Pneumology, University Hospital Freiburg, Killianstrasse 5, 79106, Freiburg, Germany (2) , St. Josefs Hospital, Wiesbaden, Germany (3) Abteilungen Pneumologie, Beatmungsmedizin und Schlaflabor, Evangelisches. Krankenhaus Gottingen-Weende, Bovenden-Lenglern, Germany (4) Zentrum fur Pneumologie und Thoraxchirurgie, Krankenhaus Grosshansdorf, Grosshansdorf, Germany (5) , Thoraxklinik-Heidelberg, Heidelberg, Germany (6) Rehabilitation Research Center, University of Bremen, Bremen, Germany Article History: Received Date: 11/04/2002 Accepted Date: 10/12/2002 Article note: Electronic Publication

Byline: Franco Cavaliere (1), Simonetta Masieri (2), Giorgio Conti (1), Massimo Antonelli (1), Mariano Alberto Pennisi (1), Roberto Filipo (2), Rodolfo Proietti (1) Keywords: Non-invasive ventilation Helmet Facial mask Impedenzometry Tympanometry Acoustic reflex Abstract: Objectives.. To evaluate the effects of non-invasive ventilation (NIV) with facial mask or helmet on middle ear (ME). Design.. Prospective, randomised study. Setting.. University hospital. Participants.. Ten healthy subjects randomly allocated in two groups of five subjects each. Interventions.. NIV for 1 h, with helmet (group H) or facial mask (group M). Flow-triggered pressure support was 10 cm[H.sub.2]O, PEEP 5 cm[H.sub.2]O, FiO.sub.2 0.21. Measurements and results.. Impedenzometry was performed before NIV and 5 min after NIV ended it was repeated 60 min later. In group H the acoustic compliance increased after NIV from 2.0+-.6 ml to 2.3+-.6 ml (P Conclusions.. The tympanic membrane is tighten by the tensor tympani and a reversible loosening suggests muscle fatigue in response to the application of intermittent positive pressure applied to the external ear during NIV with helmet. The loss of tensor tympani protective action could theoretically predispose the middle and inner ear to mechanical damage during NIV with helmet, suggesting the use of protective devices (ear plugs) in selective cases requiring long-term, high-pressure treatment. Author Affiliation: (1) Institute of Anaesthesia and Intensive Care, Catholic University of the Sacred Heart, Largo Francesco Vito 1, 00168, Rome, Italy (2) ENT Department, University 'La Sapienza', Rome, Italy Article History: Received Date: 27/08/2002 Accepted Date: 16/01/2003 Article note: Electronic Publication

Byline: Stephan A. Loer (1), Lothar A. Schwarte (1), Michael A. Pakulla (1), Olaf Picker (1), Thomas W. L. Scheeren (1) Keywords: Partial liquid ventilation Positive pressure respiration Perfluorocarbons Evaporation Dogs Abstract: Objective. Perfluorocarbons are eliminated during partial liquid ventilation mainly by evaporation via the airways. We examined whether this is affected by the level of end-expiratory airway pressure. Design and setting. Observational cohort animal study in the animal laboratory of a university hospital. Subjects. Five foxhound dogs. Interventions. The anesthetized dogs underwent partial liquid ventilation (5 ml/kg perfluorocarbon) at constant respiratory rate (17+-1 breaths/min) and tidal volume (10 ml/kg). The level of end-expiratory airway pressure was varied repeatedly between 0, 5, and 10 cm[H.sub.2]O every 25 min. Measurements and results. Expired gas was collected in reservoirs to determine evaporative perfluorocarbon loss gravimetrically. Any increase in end-expiratory airway pressure increased while any decrease in end-expiratory airway pressure reduced evaporative perfluorocarbon loss. Mean initial elimination at an end-expiratory airway pressure of 5 cm[H.sub.2]O was 19.6+-3.8 ul/kg per minute this decreased by 28% at an end-expiratory airway pressure of 0 cm[H.sub.2]O and increased by 46% at an end-expiratory airway pressure of 10 cm[H.sub.2]O. At equal levels of end-expiratory airway pressure evaporation decreased linearly over time. Conclusions. Our results suggest that the level of end-expiratory airway pressure is a determinant of evaporative perfluorocarbon loss and may have relevance for maintenance dosing and instillation intervals during partial liquid ventilation. Author Affiliation: (1) Department of Anaesthesiology, University Hospital Dusseldorf, Heinrich Heine University, Moorenstrasse 5, 40225, Dusseldorf, Germany Article History: Received Date: 25/07/2002 Accepted Date: 10/12/2002 Article note: Electronic Publication

The requirements to maintain a positive pressure with respiratory protection during heavy exercise and the effects on ventilation and feelings of discomfort were investigated. Eight male subjects participated, using the respirator system during rest and exercise at about 80% of their individual maximum power. A blower was used at maximum and medium capacity and at two pressure levels (3 and 15 mbar). Additionally, the mouth pressure was used as a feedback for the blower. The blower decreased the fraction of the breathing cycle with negative pressures from 50% (SD 4%) to 15% (SD 10%) during exercise. Negative pressures occurred at all settings of the blower during exercise. Thus, the currently available commercial blower systems do not supply a sufficient airflow to maintain a positive pressure during heavy exercise. Positive pressure breathing did not affect the ventilation and the circulation. But the oxygen consumption was higher with the blower and respirator than without. Keywords: Positive pressure breathing; Exercise; Performance

Byline: Peter Neumann (1), Wolfgang Golisch (1), Antje Strohmeyer (1), Hergen Buscher (1), Hilmar Burchardi (1), Michael Sydow (1) Keywords: Airway pressure release ventilation Unrestricted spontaneous breathing Partial mechanical ventilation Different time intervals Breathing pattern Gas exchange Abstract: Abstract Objective. Airway pressure release ventilation (APRV) is a ventilatory mode with a time cycled change between an upper (P.sub.high) and lower (P.sub.low) airway pressure level. APRV is unique because it allows unrestricted spontaneous breathing throughout the ventilatory cycle. We studied the influence of different release times (time of P.sub.low) on breathing pattern and gas exchange in patients during partial mechanical ventilation. Setting. Mixed intensive care unit in a university hospital. Patients. Twenty-eight patients were included in the study. Nine patients suffering from acute lung injury (ALI), 7 patients with a history of chronic obstructive pulmonary disease (COPD) and 12 patients with nearly normal lung function, ventilated for non-respiratory reasons (postoperatively), were studied prior to extubation. Interventions. At constant pressure levels and a pre-set airway pressure release rate of 12/min, P.sub.low was diminished and P.sub.high was prolonged in four steps of 0.5 s. Each respiratory setting was studied for 20 min after a steady state period had been achieved. Measurements and main results. We measured gas exchange and respiratory mechanics. The different time intervals of P.sub.high and P.sub.low had only minor effects on the actual spontaneous inspiration and expiration times, but the proportion of spontaneous breathing on total ventilation increased when the duration of P.sub.low was decreased. Gas exchange was almost unaffected by the interventions despite a significant increase in mean airway pressure. However, when P.sub.low was set to only 0.5 s an increase in PaCO.sub.2 occurred in patients with COPD and ALI, probably due to a decrease in mechanical ventilatory support. Conclusions. Airway pressure release ventilation is an open system which allows patients to maintain the 'time control' over the respiratory cycle independent of the chosen duration for P.sub.high and P.sub.low. Author Affiliation: (1) Department of Anaesthesiology, Emergency and Intensive Care Medicine, Georg-August-Universitat Gottingen, Robert Koch Strasse 40, 37075 Gottingen, Germany Article History: Received Date: 26/06/2001 Accepted Date: 10/09/2002 Article note: Electronic Publication

Byline: Miquel Ferrer (1), Raquel Iglesia (1), Josep Roca (1), Felip Burgos (1), Antoni Torres (1), Robert Rodriguez-Roisin (1) Keywords: Chronic obstructive pulmonary disease Gas exchange Mechanical ventilation Respiratory failure Ventilation-perfusion mismatch Weaning Abstract: Abstract Objective. To assess if pressure-support ventilation (PSV) can improve ventilation-perfusion (V.sub.A/Q) imbalance observed during the transition from positive-pressure ventilation to spontaneous breathing in intubated chronic obstructive pulmonary disease (COPD) patients during weaning. Design. Prospective study. Setting. Respiratory intensive care unit of a tertiary university hospital. Patients. Seven mechanically ventilated COPD male patients (age 68+-6 (SD) years FEV.sub.1 26+-6% predicted) during weaning. Interventions. Patients were studied during three ventilatory modalities: (1) assist-control ventilation (ACV), tidal volume (V.sub.T), 8--10 ml . kg.sup.--1 (2) PSV aimed to match [V.sub.T ]in ACV, 15+-1 cm[H.sub.2]O and (3) spontaneous breathing. Measurements and results. Arterial and mixed venous respiratory blood gases, V.sub.A/Q distributions, hemodynamics and breathing pattern were measured. Compared with both ACV and PSV, during spontaneous breathing patients exhibited decreases in V.sub.T (of 43%, p Conclusion. In COPD patients during weaning, PSV avoided V.sub.A/Q worsening during the transition from positive-pressure ventilation to spontaneous breathing. Hemodynamics, blood gases or V.sub.A/Q mismatch were no different between ACV and PSV when both modalities provided similar levels of ventilatory assistance. Author Affiliation: (1) Servei de Pneumologia i Al.lergia RespiratA2ria, Institut Clinic de Pneumologia i Cirurgia Toracica, Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036, Barcelona, Spain Article History: Received Date: 15/05/2002 Accepted Date: 06/08/2002 Article note: Electronic Publication

Byline: L. Beydon (1), L. Uttman (2), R. Rawal (1), B. Jonson (2) Keywords: Artificial respiration Pulmonary gas exchange Respiratory dead space Respiratory mechanics Acute lung injury Abstract: Abstract 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[H.sub.2]O. 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. Author Affiliation: (1) Department of Anaesthesia, University Hospital, 49033 Angers Cedex 01, France (2) Department of Clinical Physiology, University Hospital, 22185 Lund, Sweden Article History: Received Date: 27/11/2001 Accepted Date: 17/06/2002 Article note: Electronic Publication

Byline: Jack J. Haitsma (1), Stefan Uhlig (2), Ulrike Lachmann (1), Serge J. Verbrugge (1), Davey L. Poelma (1), Burkhard Lachmann (1) Keywords: Compartmentalization Exogenous surfactant Lung injury Cytokines Positive end-expiratory pressure Multiple-organ failure Abstract: Abstract Objective. To determine the effect of pretreatment with exogenous surfactant on ventilator-induced decompartmentalization of TNF-[alpha]. Design and setting. Prospective, randomized, animal study in the experimental laboratory of a university. Subjects and interventions. Male Sprague-Dawley rats (n=102) received lipopolysaccharide either intratracheally or intraperitoneally to stimulate TNF-[alpha] production one-half of the animals were pretreated with surfactant. Animals were ventilated for 20 min with a peak inspiratory pressure/positive end-expiratory pressure (PEEP) ratio of either 45/0 or 45/10 (frequency 30 bpm, I/E ratio 1:2, FIO.sub.2=1). Measurements and results. Blood gas tension and arterial pressures were recorded 1, 10, and 20 min after the start of mechanical ventilation. After the animals were killed pressure-volume curves were recorded, and bronchoalveolar lavage was performed for assessment of protein content and the small/large surfactant aggregate ratio. TNF-[alpha] was determined in serum and bronchoalveolar lavage. Pretreatment with surfactant decreased decompartmentalization of TNF-[alpha] during 45/0 ventilation. Addition of a PEEP level of 10 cm [H.sub.2]O reduced decompartmentalization even further. In addition, surfactant prevented deterioration in oxygenation and decreased accumulation of protein in the bronchoalveolar lavage in the zero-PEEP group. Conclusions. An excess of active surfactant decreases transfer of cytokines across the alveolar-capillary membrane similar to PEEP. The combination of PEEP and surfactant reduces decompartmentalization of TNF-[alpha] even further. Author Affiliation: (1) Department of Anesthesiology, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands (2) Division of Pulmonary Pharmacology, Research Center Borstel, Borstel, Germany Article History: Received Date: 19/10/2001 Accepted Date: 22/05/2002 Article note: Electronic Publication

Byline: Jean-Christophe Richard (1), Laurent Brochard (2), Lucie Breton (1), Jerome Aboab (1), Philippe Vandelet (1), Fabienne Tamion (1), Salvatore M. Maggiore (3), Alain Mercat (4), Guy Bonmarchand (1) Keywords: Acute lung injury Mechanical ventilation Positive end-expiratory pressure Dynamic hyperinflation Abstract: Abstract Objective. Reduction in tidal volume (Vt) associated with increase in respiratory rate to limit hypercapnia is now proposed in patients with acute lung injury (ALI). The aim of this study was to test whether a high respiratory rate induces significant intrinsic positive end-expiratory pressure (PEEPi) in these patients. Design. Prospective crossover study. Setting. A medical intensive care unit. Interventions and measurements. Ten consecutive patients fulfilling criteria for severe ALI were ventilated with a 6 ml/kg Vt, a total PEEP level at 13+-3 cm[H.sub.2]O and a plateau pressure kept at 23+-4 cm[H.sub.2]O. The respiratory rate was randomly set below 20 breaths/min (17+-3 breaths/min) and increased to 30 breaths/min (30+-3 breaths/min) to compensate for hypercapnia. External PEEP was adjusted to keep the total PEEP and the plateau pressure constant. PEEPi was computed as the difference between total PEEP and external PEEP. The lung volume retained by PEEPi was then measured. Results. Increase in respiratory rate resulted in significantly higher PEEPi (1.3+-0.4 versus 3.9+-1.1 cm[H.sub.2]O, p Conclusions. An increase in respiratory rate used to avoid Vt reduction-induced hypercapnia may induce substantial gas trapping and PEEPi in patients with ALI. Author Affiliation: (1) Medical Intensive Care Unit, University Hospital-Charles Nicolle, 1 rue de Germont, 76031 Rouen, France (2) Medical Intensive Care Unit, INSERM U 492, University Paris 12, Hospital Henri Mondor, AP-HP, 51 avenue de Mal de Lattre de Tassigny, Creteil, France (3) Department of Intensive Care and Anesthesiology, Universita Cattolica-Policlinico A. Gemelli, Rome, Italy (4) Medical Intensive Care Unit, University Hospital, 4 rue Larrey, 49033 Angers, France Article History: Received Date: 13/11/2001 Accepted Date: 30/04/2002 Article note: Electronic Publication

Byline: S. Lethvall (1), S. Sondergaard (1), S. Karason (1), S. Lundin (1), O. Stenqvist (1) Keywords: Dead-space Tracheal pressure Carbon dioxide Hypercapnia Acute respiratory distress syndrome Double lumen tube Abstract: Abstract Objective. To evaluate the effects on CO.sub.2 washout of the coaxial double lumen tube (DLT) as compared to a standard endotracheal tube (ETT) and tracheal gas insufflation (TGI). Precision of tracheal pressure monitoring through the DLT and safety issues, including intrinsic PEEP (PEEPi) formation during DLT ventilation, were also evaluated. Design. Lung model study. Setting. University research laboratory. Measurements and results. CO.sub.2 washout was analysed in a lung model by measuring single alveolar CO.sub.2 concentration during DLT ventilation as compared to standard ETT ventilation, at different minute ventilation (6--14 l/min) and different CO.sub.2-output levels (180 ml/min, 240 ml/min, and 300 ml/min). At a CO.sub.2 output level of 240 ml/min the CO.sub.2 washout was also compared to tidal volume-adjusted continuous TGI and expiratory synchronised TGI. Precision of tracheal pressure monitoring and PEEPi formation during DLT ventilation was evaluated by comparing pressure in each limb above the tube to reference tracheal pressure, varying I:E ratios (1:2, 1:1, and 2:1), tidal volumes (300--700 ml), breathing frequencies (15--25), and compliance (20--50 ml/cm[H.sub.2]O). DLT ventilation had the same efficacy in removing CO.sub.2 as continuous and expiratory synchronised TGI, reducing single alveolar CO.sub.2 concentration by 9--21% compared to normal ventilation. Tracheal pressure could be measured through the DLT with high precision. There was only marginal formation of PEEPi at tidal volumes a$?600 ml, I:E ratio a$?1:1, and compliance a$?35 ml/cm[H.sub.2]O. Conclusions. The double lumen tube is as effective as tracheal gas insufflation in reducing CO.sub.2 tension. Tracheal pressure and formation of PEEPi can be monitored with high precision without interrupting ventilation. Author Affiliation: (1) Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, 413 45 Goteborg, Sweden Article History: Received Date: 13/06/2001 Accepted Date: 14/04/2002 Article note: Electronic Publication

Byline: F. Stuber (1), H. Wrigge (1), S. Schroeder (1), S. Wetegrove (1), J. Zinserling (1), A. Hoeft (1), C. Putensen (1) Keywords: Acute respiratory distress syndrome Acute lung injury Positive pressure ventilation Protective mechanical ventilation Inflammatory cytokines Abstract: Abstract Objective. To investigate the kinetic and reversibility of mechanical ventilation-associated pulmonary and systemic inflammatory response in patients with acute lung injury (ALI). Design. Prospective observational cross-over study. Setting. Intensive care unit of a university hospital. Patients. Twelve mechanically ventilated patients with ALI. Interventions. Mechanical ventilation was transiently changed from a lung protective setting with PEEP of 15 cm[H.sub.2]O and a V.sub.T of 5 ml/kg predicted body weight to a more conventional ventilatory setting with PEEP of 5 cm[H.sub.2]O and V.sub.T of 12 ml/kg predicted body weight for a period of 6 h. Measurements and results. We examined the profile of interleukin (IL)-1[beta], IL-1 receptor antagonist, IL-6, IL-10, and tumor necrosis factor in the plasma of all patients, and in the bronchoalveolar lavage (mini-BAL) fluid of six of these patients. Measurements were performed at baseline, 1 h, and 6 h after each change of the ventilatory setting. Switching to conventional mechanical ventilation was associated with a higher PaO.sub.2 (P Conclusions. In patients with ALI, initiation of low PEEP and high V.sub.T mechanical ventilation is associated with cytokine release into circulation which occurred within 1 h. It is independent from BAL procedures and can be reversed by reinstitution of lung protective mechanical ventilation. Author Affiliation: (1) Department of Anesthesiology and Intensive Care Medicine, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany Article History: Received Date: 25/09/2001 Accepted Date: 23/01/2002 Article note: Electronic Publication

Byline: Ali Al-Khafaji (1), Harold L. Manning (2) Keywords: Mechanical ventilators Positive end-expiratory pressure Suction Triggering Air leak Abstract: Objective: To examine the phenomenon of inappropriate triggering caused by an in-line suction catheter. Design: We used a test lung to assess inappropriate triggering in four ventilators with both pressure and flow triggering. Results: With pressure triggering, inappropriate triggering occurred only in the presence of PEEP. However, with flow triggering, inappropriate triggering occurred both with and without PEEP. Inappropriate triggering did not occur in a model of severe airflow obstruction. Conclusion: In-line suction catheters may lead to inappropriate triggering and potentially dangerous increases in delivered ventilation. Author Affiliation: (1) Department of Medicine, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756-0001, USA (2) Department of Medicine and Physiology, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756-0001, USA Article History: Received Date: 16/08/2001 Accepted Date: 07/01/2002 Article note: Electronic Publication

Byline: Carlo A. Volta (1), Elisabetta Marangoni (1), Valentina Alvisi (1), Maurizia Capuzzo (1), Riccardo Ragazzi (1), Lina Pavanelli (1), Raffaele Alvisi (1) Keywords: Expiratory flow limitation chronic obstructive pulmonary disease Least squares fitting method Compliance Resistance Positive end-expiratory pressure Abstract: Objective: Although computerized methods of analyzing respiratory system mechanics such as the least squares fitting method have been used in various patient populations, no conclusive data are available in patients with chronic obstructive pulmonary disease (COPD), probably because they may develop expiratory flow limitation (EFL). This suggests that respiratory mechanics be determined only during inspiration. Setting: Eight-bed multidisciplinary ICU of a teaching hospital. Patients: Eight non-flow-limited postvascular surgery patients and eight flow-limited COPD patients. Intervention: Patients were sedated, paralyzed for diagnostic purposes, and ventilated in volume control ventilation with constant inspiratory flow rate. Measurements: Data on resistance, compliance, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) obtained by applying the least squares fitting method during inspiration, expiration, and the overall breathing cycle were compared with those obtained by the traditional method (constant flow, end-inspiratory occlusion method). Results and conclusion: Our results indicate that (a) the presence of EFL markedly decreases the precision of resistance and compliance values measured by the LSF method, (b) the determination of respiratory variables during inspiration allows the calculation of respiratory mechanics in flow limited COPD patients, and (c) the LSF method is able to detect the presence of PEEPi,dyn if only inspiratory data are used. Author Affiliation: (1) Department of Surgical, Anesthesiological and Radiological Sciences, Section of Anesthesia and Intensive Care, Ospedale S. Anna, University of Ferrara, Corso Giovecca n. 203, 44100 Ferrara, Italy Article History: Received Date: 30/01/2001 Accepted Date: 28/09/2001 Article note: Electronic Publication

Byline: A. Elgellab (1), Y. Riou (2), A. Abbazine (1), P. Truffert (1), R. Matran (2), P. Lequien (1), L. Storme (1) Keywords: Nasal continuous positive airway pressure End-expiratory lung volume level Respiratory inductive plethysmography Premature infants Abstract: Objective: The aim of the study was to assess the influence of nasal continuous positive airway pressure (NCPAP) on breathing pattern in preterm newborns. Design: Prospective study. Setting: Neonatal intensive care unit. Patients: Ten premature newborn infants on NCPAP (gestational age range from 27 to 32 weeks, mean birth weight 1300+-460 g) admitted in our neonatal intensive care unit (NICU) for respiratory distress syndrome. Methods: Breathing patterns and changes in lung volumes level were obtained using respiratory inductive plethysmography (RIP), at random CPAP levels (0, 2, 4, 6 and 8 cmH.sub.20). Raw data were analysed for end-expiratory lung volume level (EELV-level), tidal volume (Vt), respiratory rate, phase angle and labour breathing index (LBI). Results: CPAP increased EELV-level by 2.1+-0.3xVt from 0 to 8 cmH.sub.20 (p Author Affiliation: (1) Department of Neonatology, Centre Hospitalier et Universitaire, 59037, Lille cedex, France (2) Department of Physiology, Centre Hospitalier et Universitaire, 59037, Lille cedex, France Article History: Received Date: 16/08/2001 Accepted Date: 23/08/2001 Article note: Final revision received: 1 June 2001 Electronic Publication

Byline: J. Meliones (1), K. Kocis (2), A. R. Bengur (3), A. R. Snider (3) Keywords: Key words Cardiopulmonary interactions; Congenital heart disease; D-transposition of the great arteries; Diastolic function; Doppler ultrasonography; Inspiratory time Abstract: Author Affiliation: (1) Department of Anesthesia, Duke Children's Hospital, P. O. Box 3046, Duke University Medical Center, Durham, NC 27710--0001, USA e-mail: melio001@mc.duke.edu Tel.: + 1-9 19-6 81 64 03 Fax: + 1-9 19-6 18 83 57, US (2) Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, Mich., USA, US (3) Department of Pediatrics, Duke Children's Hospital, Duke University Medical Center, Durham, NC 27710--0001, USA, US Article note: Received: 27 July 1999/Final revision received: 21 January 2000/Accepted: 26 January 2000

Byline: A. Vianello (1) Keywords: Key words Neuromuscular disorder; Acute respiratory failure; Non-invasive positive pressure ventilation Abstract: Objective: Prospectively to investigate the efficacy of non-invasive positive pressure ventilation (NPPV) combined with cricothyroid 'mini-tracheostomy' (CM) as a first-line intervention in patients with acute respiratory failure (ARF) of neuromuscular origin, in comparison with positive pressure ventilation (PPV) via endotracheal intubation (ETI).APDesign: Prospective analysis of the short-term outcomes of 14 non-consecutive patients suffering from ARF of neuromuscular origin who were administered NPPV and comparison with the outcomes of 14 matched historical control patients receiving conventional mechanical ventilation (MV) via ETI.APSetting: Adult five-bedded respiratory intensive care unit in a university hospital.APPatients and interventions: Fourteen neuromyopathic patients who developed hypercapnic ARF and were submitted to NPPV (group A) and fourteen matched historical control patients, who were administered PPV via ETI (group B). Seven subjects receiving NPPV also underwent CM.APOutcome measures: Mortality during ICU stay and treatment failure were evaluated treatment failure was defined as death or the need for ETI for the NPPV group and as death or the inability to wean from MV for the control group. Length of stay in the ICU and time to improvement, defined as the time required for a significant relief of dyspnea and neurologic impairment and for correction of arterial blood gases, were also compared.APResults: Intra-hospital mortality and treatment failure were lower in the NPPV group than in the conventional PPV via ETI group (2 vs 8 cases and 4 vs 11 cases, respectively). In addition, the duration of ICU stay for subjects who underwent NPPV was shorter than for patients who were intubated (13.6 +- 9.7 vs 47.1 +- 51.9 days). 'Mini-tracheostomy' was well tolerated and no significant side effects were encountered. Two patient were excluded from the study because they showed a severe inability to swallow and needed to be intubated to protect the upper airway from the risk of aspiration.APConclusions: Non-invasive positive pressure ventilation in combination with CM may be considered as a safer and more effective alternative to ETI in the treatment of patients with neuromuscular disorders (NMD) who develop ARF and require MV nevertheless, patient selection remains important, since a significant proportion of neuromyopathic patients might have to be excluded from NPPV because of severe risk of aspiration. Author Affiliation: (1) Respiratory Pathophysiology Department, City Hospital of Padova, Stabilimento 'F. Busonera', via Gattamelata 64, I-35100 Padova, Italy, Tel.: + 39-0 49-8 21 56 23 Fax: + 39-0 49-8 21 56 22, IT Article note: Received: 16 February 1999/Final revision received: 4 January 2000/Accepted: 18 January 2000

Byline: P. Kiefer (1), S. Nunes (1), P. Kosonen (1), J. Takala (1) Keywords: Key words Acute lung injury; Pressure gradients; PEEP; Splanchnic perfusion Abstract: Objective: To evaluate the acute effects of an increased positive end-expiratory pressure (PEEP) on splanchnic tissue perfusion.APDesign: Clinical prospective study.APSetting: Intensive care unit in a university clinic.APPatients: Six patients with severe acute lung injury (ALI) requiring mechanical ventilation. All patients had bilateral infiltrates in chest X-ray, PaO.sub.2/FiO.sub.2 < 200 mmHg and stable hemodynamics without vasoactive drugs.APInterventions: PEEP was increased by 5 cm[H.sub.2]O from a clinically selected PEEP level (8/6--11 cm[H.sub.2]O) up to (13/10--14 cm[H.sub.2]O) followed by a return to baseline.APMeasurements and main results: Splanchnic blood flow was measured using primed continuous infusion of indocyanine green dye with hepatic venous sampling and systemic hemodynamics by routine monitoring. In addition, we estimated gastric mucosal-arterial PCO.sub.2 difference and splanchnic lactate/pyruvate exchange. After a baseline measurement, PEEP was increased. After 60 min all measurements were repeated. PEEP was returned to the baseline level and a third measurement followed. PEEP had no effect on cardiac index (baseline I: 3.2/6.1--2.5 l/min/m.sup.2 PEEP: 3.3/5.7--AP2.3 l/min/m.sup.2 baseline II: 3.4/6.0--2.5 l/min/m.sup.2) neither did PEEP have any effect on splanchnic blood flow (baseline I: 0.91/1.39--0.62 l/min/m.sup.2 PEEP: 1.04/1.75--0.54 l/min/m.sup.2 baseline II:1.07/1.42--0.68 l/min/m.sup.2, respectively) or perfusion (gastric mucosal-arterial PCO.sub.2 difference baseline I: 2.1/12.8--0.6 kPa PEEP: 1.7/14.5--0.7 kPa baseline II: 1.7/8.8--0.1 kPa lactate uptake baseline I: 0.5/1.1--0.3 mmol/min/m.sup.2 PEEP: 0.4/1.0--0.3 mmol/min/m.sup.2 baseline II: 0.5/0.9--0.3 mmol/min/m.sup.2 hepatic venous lactate/pyruvate baseline I: 9.7/10.6--5.7 PEEP: 9.7/14.2--6.4 baseline II: 8.4/12.4--7.3 respectively).APConclusion: PEEP by itself does not have a consistent effect on splanchnic blood flow and metabolism when cardiac index is stable and patients are ventilated within the linear part of the pv curve. Author Affiliation: (1) Critical Care Research Program, Division of Intensive Care, Department of Anesthesiology and Intensive Care, Kuopio University Hospital, 70 210 Kuopio, Finland, e-mail: jukka.takala@insel.ch, Tel.: + 31-41-6 32 44 00 Fax: + 31-41-6 32 41 00, FI (2) Department of Intensive Care Medicine, University Hospital of Bern (Inselspital), 3010 Bern, Switzerland, CH Article note: Received: 29 April 1999/Final revision received: 17 November 1999/Accepted: 2 February 2000

Byline: Jesus Villar (1), L. Perez-Mendez (2), R. M. Kacmarek (3) Keywords: Key words ARDS; Acute lung injury; Sepsis; Outcome; Risk factor; Positive end-expiratory pressure; Oxygenation index; Definition Abstract: Background: Despite intensive research, there are no universally accepted clinical definitions for acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS). A recent joint American-European Consensus Conference on ARDS formally defined the difference between ALI and ARDS based on the degree of oxygenation impairment. However, this definition may not reflect the true prevalence, severity and prognosis of these syndromes. Methods: During a 22-month period, 56 consecutive mechanically ventilated patients who met the American-European Consensus definition for ARDS [arterial oxygen tension/fractional inspired oxygen (PaO.sub.2/FI[O.sub.2]a$? 200 mmHg regardless of the level of positive end-expiratory pressure (PEEP), bilateral pulmonary infiltrates, and no evidence of left heart failure] were admitted into the intensive care units (ICU) of the Hospital del Pino, Las Palmas, Spain, and prospectively studied. The diagnosis of ALI and ARDS was made by a PEEP-FIO.sub.2 trial, 24 h after patients met the Consensus inclusion criteria. Patients were classified as having ALI.sub.--24 h if the PaO.sub.2/FIO.sub.2 was > 150 mmHg with PEEP = 5 cm[H.sub.2]O, and ARDS.sub.--24 h if the PaO.sub.2 /FIO.sub.2 was a$? 150 mmHg with PEEP aY= 5 cm[H.sub.2]O. Results: Overall mortality was 43 % (24 of 56). However, 24 h after inclusion, PaO.sub.2 response to PEEP 5 cm[H.sub.2]O allowed the separation of our patients into two different groups: 31 patients met our ALI.sub.--24 h criteria (PaO.sub.2/FIO.sub.2 > 150 mmHg) and their mortality was 22.6 % 25 patients met our ARDS.sub.--24 h criteria (PaO.sub.2/FI[O.sub.2]a$? 150 mmHg) and their mortality was 68 % (p = 0.0016). The differences in the respiratory severity index during the first 24 h of inclusion, PaO.sub.2/FIO.sub.2 ratio at baseline and at 24 h, maximum plateau airway pressure, maximum level of PEEP, and number of organ system failures during the ICU stay were statistically significant. Conclusions: Since the use of PEEP in the American-European Consensus criteria for ARDS is not mandatory, that definition does not reflect the true severity of lung damage and outcome. Our data support the need for guidelines based on a specific method of evaluating oxygenation status before the American-European Consensus definition is adopted. Author Affiliation: (1) Research Institute, Hospital de la Candelaria, Tenerife, Canary Islands, Spain Samuel Lunenfeld Research Institute, Toronto, Canada Critical Care Medicine, Mercer University, Macon, Ga., USA (e-mail: jvillar@cistia.es Tel. + 34(9 22)60 23 89 Fax + 34(9 22)6 00 5 62), CA (2) Department of Epidemiology, Research Institute, Hospital de la Candelaria, Tenerife, Canary Islands, Spain, ES (3) Department of Respiratory Care, Massachussetts General Hospital, Boston Department of Anesthesia, Harvard University, Boston, Ma., USA, US Article note: Received: 18 April 1999 Final revision received: 30 June 1999 Accepted: 9 July 1999

Byline: D. A. Kontoyannis (1), J. N. Nanas (1), S. A. Kontoyannis (1), S. F. Stamatelopoulos (1), S. D. Moulopoulos (1) Keywords: Key words Cardiogenic shock; Mechanical ventilation; Mechanical assistance Abstract: Objective: To examine the effects of mechanical ventilation with positive end-expiratory pressure (PEEP), in conjunction with the intra-aortic balloon pump (IABP), on the outcome of patients in profound cardiogenic shock. Patients: Twenty-eight consecutive patients presenting with myocardial infarction complicated by cardiogenic shock refractory to medical therapy, including dobutamine, dopamine and fluid administration. Eighteen patients were assisted by the IABP alone (IABP group), and ten patients by the IABP plus controlled mechanical ventilation with PEEP set at 10 cm[H.sub.2]O (IABP + CMV group). Results: Weaning from mechanical assistance was accomplished in 8 out of 18 patients in the IABP group versus 9 out of 10 patients in the IABP + CMV group (p = 0.04). Ultimately, 5 of 18 patients in the IABP group were discharged from the hospital versus 8 of 10 patients in the IABP + CMV group (p = 0.01). Conclusion: Mechanical ventilation with PEEP at 10 cm[H.sub.2]O supplements the IABP and may improve the survival rates of patients suffering from cardiogenic shock. Author Affiliation: (1) University of Athens School of Medicine, Department of Clinical Therapeutics, 'Alexandra' Hospital, Vas. Sophias and K. Lourou 2, GR-115 28 Athens, Greece, GR Article note: Received: 12 November 1998 Final revision received: 28 March 1999 Accepted: 4 May 1999

Byline: E. Calderini (1), M. Confalonieri (2), P. G. Puccio (1), N. Francavilla (1), L. Stella (1), C. Gregoretti (3) Keywords: Key words Noninvasive positive pressure ventilation; Hypoxemia; Acute respiratory failure; Acquired immunodeficiency syndrome Abstract: Objective: Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure. Study population: Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol. Intervention: Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20 conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm [H.sub.2]O, PEEP of 5 cm [H.sub.2]O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (IPes) were measured to evaluate the patient's respiratory effort. A subjective 'comfort score' and the difference between patient and machine respiratory rate [IRR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction. Results: Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H.sub.20) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, IPes, and IRR(p-v) when compared to NIPSVfc [230 +- 41 (SE) vs 376 +- 72 cm [H.sub.2]O * s * min.sup.--1 8 +- 2 vs 13 +- 2 cm [H.sub.2]O 1 +- 1 vs 9 +- 2 br * min.sup.--1 respectively] with a concomitant significant improvement of the 'comfort score'. Conclusions: In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV. Author Affiliation: (1) Terapia Intensiva Malattie Infettive CSL, IRCCS H San Raffaele, I-20 127 Milano, Italy, IT (2) U.O. di Pneumologia, Ospedale Civile, via Crotti, 24, I-29 100 Piacenza, Italy e-mail: mconfalonieri@qubisoft.it Tel. + 39 05 23 30 25 33 Fax + 39 05 23 38 59 00, IT (3) Servizio di Anestesia e Rianimazione, Centro Traumatologico Ortopedico, Torino, Italy, IT Article note: Received: 5 June 1998 Accepted: 24 February 1999