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Byline: Sandrine Essouri (1,3), Philippe Durand (1), Laurent Chevret (1), Vincent Haas (1), Claire Perot (1), Annick Clement (2), Denis Devictor (1), Brigitte Fauroux (2) Keywords: Noninvasive positive pressure ventilation; Acute respiratory insufficiency; Work of breathing; Children Abstract: Introduction A prospective physiological study was performed in 12 paediatric patients with acute moderate hypercapnic respiratory insufficiency to assess the ability of noninvasive positive pressure ventilation (NPPV) to unload the respiratory muscles and improve gas exchange. Materials and methods Breathing pattern, gas exchange, and inspiratory muscle effort were measured during spontaneous breathing and NPPV. Results NPPV was associated with a significant improvement in breathing pattern, gas exchange and respiratory muscle output. Tidal volume and minute ventilation increased by 33 and 17%, and oesophageal and diaphragmatic pressure time product decreased by 49 and 56%, respectively. This improvement in alveolar ventilation translated into a reduction in mean partial pressure in carbon dioxide from 48 to 40 mmHg (P = 0.01) and in respiratory rate from 48 to 41 breaths/min (P = 0.01). No difference between a clinical setting and a physiological setting of NPPV was observed. In conclusion, this study shows that NPPV is able to unload the respiratory muscles and improve clinical outcome in young patients admitted to the paediatric intensive care unit for acute moderate hypercapnic respiratory insufficiency. Author Affiliation: (1) AP-HP, Pediatric Intensive Care Unit, Kremlin-Bicetre Hospital, Kremlin-Bicetre, France (2) AP-HP, Pediatric Pulmonary Department, Armand Trousseau Hospital, Universite Pierre et Marie Curie-Paris6, INSERM UMR S-893 Equipe 12, Paris, France (3) Service de reanimation pediatrique, Hopital du Kremlin-Bicetre, 78 rue du General Leclerc, 94270, Kremlin-Bicetre, France Article History: Registration Date: 24/06/2008 Received Date: 12/02/2008 Accepted Date: 09/06/2008 Online Date: 19/08/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1202-9) contains supplementary material, which is available to authorized users.

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: Antoine Vieillard-Baron (1), Sebastien Prin (1), Karim Chergui (1), Bernard Page (1), Alain Beauchet (2), Francois Jardin (1) Keywords: ARDS; Pressure--volume loop; PEEP; Recruitment Abstract: Objective Evaluation of low-flow pressure--volume loop at the bedside in ARDS, as an aid to assess recruitment produced by PEEP. Materials and methods Low-flow pressure--volume loop at the bedside were obtained on the first day of respiratory support in 54 successive pulmonary ARDS patients (49 of whom had pneumonia) treated between April 1999 and June 2002. From the loop obtained at ZEEP, we determined manually the lower inflexion point (LIP). By superimposing the pressure--volume loop at ZEEP and at PEEP, we evaluated recruitment obtained at a constant elastic pressure of 20 cm [H.sub.2]O. Results We observed two different types of loops, according to the pattern of the inflation limb. In type 1 (38 cases) the inflation limb was characterized by an inflexion zone, resulting from a progressive or a sudden improvement in compliance. In type 2 (16 patients) the inflation limb was virtually linear, without significant improvement in compliance during inflation, which remained particularly low (26+-9 cm [H.sub.2]O). Use of a low PEEP (6+-2 cm [H.sub.2]O) produced a substantial recruitment in type-1 patients (74+-53 ml), which was marginally improved by a higher PEEP (89+-54 ml). In type 2, recruitment produced by PEEP was significantly lower (48+-26 ml, p=0.006). Conclusion Pressure--volume loop at bedside confirmed that a low PEEP was sufficient to obtain recruitment in ARDS. This study also individualized a group of pulmonary ARDS patients exhibiting a markedly reduced compliance, in whom recruitment obtained by PEEP was limited. Author Affiliation: (1) Medical Intensive Care Unit, University Hospital Ambroise Pare, Assistance Publique Hopitaux de Paris, 9 avenue Charles de Gaulle, 92104, Boulogne Cedex, France (2) Department of Biostatistics, University Hospital Ambroise Pare, Assistance Publique Hopitaux de Paris, 9 avenue Charles de Gaulle, 92104, Boulogne Cedex, France Article History: Received Date: 31/03/2003 Accepted Date: 10/07/2003 Online Date: 16/08/2003

Byline: Brigitte Fauroux (1,2,3), Nicholas Hart (1,2,3), Yuan M. Luo (1,2,3), Stephanie MacNeill (1,2,3), John Moxham (1,2,3), Frederic Lofaso (1,2,3), Michael I. Polkey (1,2,3) Keywords: Diaphragm; Pressure time product; Oesophageal electromyography; Pressure-support ventilation; Inspiratory pressure support ventilation; Diaphragmatic electromyography Abstract: Objective The diaphragmatic pressure-time product (PTPdi) has been used to quantify the loading and unloading of the diaphragm. The validity of the relationship between PTPdi and diaphragm electrical activity (EMGdi) during pressure-support ventilation (PSV) is unclear. We examined this relationship. Design and setting Physiological study in a physiology laboratory. Subjects Six healthy adults. Interventions Spontaneous breathing (SB) and two levels of PSV (6 and 12 cm[H.sub.2]O), breathing room air and incremental concentrations of carbon dioxide, sufficient to achieve an EMGdi signal of approximately 200% of baseline value. Measurements and results We measured the electrical (EMGdi) and mechanical (PTPdi) activity of the diaphragm using oesophageal electrode and oesophageal and gastric balloon catheters. The relationship between EMGdi and PTPdi during SB was linear in five subjects and curvilinear in one. However, with PSV 12 cm[H.sub.2]O we observed that the relationship between EMGdi and PTPdi was 'left shifted' specifically, for any given level of EMGdi the PTPdi was smaller with PSV 12 cm[H.sub.2]O than during SB. However, when PTPdi was converted to power (the product of pressure and flow) the tendency to left shift was largely reversed. Conclusions We conclude that when assessing of diaphragm unloading during PSV flow measurements are required. Where flow is constant, PTPdi is a valid measure of diaphragm unloading, but if not these data may be used to make an appropriate correction. Author Affiliation: (1) Respiratory Muscle Laboratory, Royal Brompton Hospital, Fulham Road, London, SW3 6NP, UK (2) Paediatric Pulmonary Department and Research Unit INSERM E 213, Armand Trousseau Hospital, Assistance Publique Hopitaux de Paris, Paris, France (3) Physiology Department, Raymond Poincare Hospital, Assistance Publique Hopitaux de Paris, Garches, France Article History: Received Date: 14/04/2003 Accepted Date: 17/07/2003 Online Date: 11/10/2003 Article note: Brigitte Fauroux was supported by a grant from the Societe de Pneumologie de Langue Francaise.

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: Martin Beiderlinden (1), Harald Groeben (1), Jurgen Peters (1) Keywords: Acute respiratory distress syndrome Complications PIF index Bronchoscopy Derecruitment Abstract: Objective. To assess the impact of bronchoscopically guided percutaneous dilational tracheostomy (PDT) on oxygenation in patients with severe respiratory failure ventilated with high positive end-expiratory pressure (PEEP). Design. Prospective clinical study. Setting. Anaesthesiological ICU, referral centre for acute respiratory distress syndrome (ARDS) therapy, university hospital. Patients. Mechanically ventilated patients with indication for PDT. . Two hundred three consecutive PDTs were performed in 198 patients on either high (>10 mbar, n=88) or low (a$?10 mbar, n=115) PEEP under bronchoscopic guidance. Arterial blood gas tensions were measured immediately before and 1 and 24 h after PDT. Results. Positive end-expiratory pressure averaged 16.6+-4 mbar in the high PEEP and 7.6+-2.2 mbar in the low PEEP group. In the high PEEP group the PaO.sub.2/FI[O.sub.2 ]ratio was lower (243+-90 vs 285+-78 mmHg) and PaCO.sub.2 higher (45+-9.4 vs 39+-7.1 mmHg) when compared to the low PEEP group. Nevertheless, PDT did not significantly decrease oxygenation in either group 1 and 24 h after PDT (PaO.sub.2/FIO.sub.2: 223+-83 and 260+-86 mmHg in the high PEEP group and 280+-88 and 302+-82 mmHg in the low PEEP group, respectively). Furthermore, oxygenation did not deteriorate with PDT even in patients with gravely impaired gas exchange (lowest quartile) with a PaO.sub.2/FIO.sub.2 averaging 130+-42 mmHg (range 45--192 mmHg) at a PEEP of 17+-4 mbar. Conclusions. Bronchoscopically guided PDT in our patients on high PEEP did not jeopardise oxygenation 1 h and 24 h following PDT. Accordingly, high PEEP and hypoxic respiratory failure should not be considered a general contraindication for PDT. Author Affiliation: (1) Klinik fur Anasthesiologie und Intensivmedizin, Universitatsklinikum Essen, Hufelandstrasse 55, 45122, Essen, Germany Article History: Received Date: 14/05/2002 Accepted Date: 16/12/2002 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

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: 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: G.-L. Chelucci (1), J. Dall'Ava-Santucci (2), J.-F. Dhainaut (2), A. Chelucci (1), A. Allegra (1), A. Lockhart (2), W. A. Zin (3), J. Milic-Emili (4) Keywords: Key words Passive lung deflation; Respiratory time constants; Airway resistance; Alveolar recruitment; PEEP; ARDS Abstract: Objective: To assess the effects of the association of positive end-expiratory pressure (PEEP) with different inflation volumes (V.sub.T's) on passive lung deflation and alveolar recruitment in ARDS patients.APDesign: Clinical study using PEEP with two different V.sub.T's and analyzing whether passive lung deflation and alveolar recruitment (Vrec) depend on end-inspired (EILV) or end-expired (EELV) lung volume in mechanically ventilated ARDS patients.APSetting: Medical intensive care unit in a university hospital.APPatients and participants: Six mechanically ventilated consecutive supine patients with ARDS.APInterventions: Time-course of thoracic volume decay during passive expiration and Vrec were investigated in six ARDS patients ventilated on PEEP with baseline V.sub.T (V.sub.T,b) and 0.5V.sub.T (0.5V.sub.T,b), and on zero PEEP (ZEEP) with V.sub.T,b. Time constants of the fast (I .sub.1) and slow (I .sub.2) emptying compartments, as well as resistances and elastances were also determined.APMeasurements and results: (a) the bi-exponential model best fitted the volume decay in all instances. The fast compartment was responsible for 84 +- 7 (0.5V.sub.T,b) and 86 +- 5 % (V.sub.T,b) on PEEP vs 81 +- 6 % (V.sub.T,b) on ZEEP (P:ns) of the exhaled V.sub.T, with I .sub.1 of 0.50 +- 0.13 and 0.58 +- 0.17 s vs 0.35 +- 0.11 s, respectively (b) only I .sub.1 for V.sub.T,b on PEEP differed significantly (P < 0.02) from the one on ZEEP, suggesting a slower initial emptying (c) for the same PEEP, Vrec was higher with a higher volume (V.sub.T,b) than at a lesser one (0.5V.sub.T,b), reflecting the higher V.sub.T.APConclusions: In mechanically ventilated ARDS patients: (a) the behavior of airway resistance seems to depend on the degree of the prevailing lung distension (b) alveolar recruitment appears to be more important when higher tidal volumes are used during mechanical ventilation on PEEP (c) PEEP changes the mechanical properties of the respiratory system fast-emptying compartment. Author Affiliation: (1) Department of Critical Care Medicine, Section of Respiratory Pathophysiology, University of Florence, v.le Morgagni 85, 50 134 Florence, Italy e-mail: g.chelucci@dfc.unifi.it Tel.: + 39-0 55-41 31 83 Fax: + 39-0 55-4 22 32 02/4 22 24 09, IT (2) Departments of Physiology and Intensive Care, Hopital Cochin, Paris, France, FR (3) Institute of Biophysics, Federal University of Rio de Janeiro, Brazil, BR (4) Meakins-Christie Laboratories, McGill University, Montreal, Canada, CA Article note: Received: 16 June 1999 Final revision received: 31 March 2000 Accepted: 7 April 2000

Byline: P. C. Rimensberger (1), J.-C. Pache (2), C. McKerlie (3), H. Frndova (4), P. N. Cox (4) Keywords: Key words Intermittent positive pressure ventilation; Positive end-expiratory pressure; High-frequency oscillation; Volume recruitment maneuvers; Pulmonary mechanics; Lung volume Abstract: Objective: To determine whether using a small tidal volume (5 ml/kg) ventilation following sustained inflation with positive end-expiratory pressure (PEEP) set above the critical closing pressure (CCP) allows oxygenation equally well and induces as little lung damage as high-frequency oscillation following sustained inflation with a continuous distending pressure (CDP) slightly above the CCP of the lung.APMaterial and methods: Twelve surfactant-depleted adult New Zealand rabbits were ventilated for 4 h after being randomly assigned to one of two groups: group 1, conventional mechanical ventilation, tidal volume 5 ml/kg, sustained inflation followed by PEEP > CCP group 2, high-frequency oscillation, sustained inflation followed by CDP > CCP.APResults: In both groups oxygenation improved substantially after sustained inflation (P < 0.05) and remained stable over 4 h of ventilation without any differences between the groups. Histologically, both groups showed only little airway injury to bronchioles, alveolar ducts, and alveolar airspace, with no difference between the two groups. Myleoperoxidase content in homogenized lung tissue, as a marker of leukocyte infiltration, was equivalent in the two groups.APConclusions: We conclude that a volume recruitment strategy during small tidal volume ventilation and maintaining lung volumes above lung closing is as protective as that of high-frequency oscillation at similar lung volumes in this model of lung injury Author Affiliation: (1) Department of Pediatric Intensive Care, Hopital des Enfants, University Hospital of Geneva, 6 Rue Willy-Donze, 1211 Geneva 14, Switzerland e-mail: Peter.Rimensberger@hcuge.ch Tel.: + 41-22-3 82 46 23 Fax: + 41-22-3 82 46 75, CH (2) Department of Pathology, Hopital des Enfants, University Hospital of Geneva, 6 Rue Willy-Donze, 1211 Geneva 14, Switzerland, CH (3) Research Services, Health Science Center Sunnybrook, University of Toronto, Canada, CA (4) Department of Critical Care, Hospital for Sick Children, University of Toronto, Canada, CA Article note: Received: 5 July 1999/Final revision received: 10 February 2000/Accepted: 25 February 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

The hypothesis that prolonged exposure to high intermittent positive-pressure ventilation (HIPPV) promotes the development of airway hyperresponsiveness and remodeling was tested in young rats ventilated under halothane anesthesia with HIPPV. Results revealed that repetitive exposure to HPPV in the absence of hyperoxia for a short period of six days produces hyperresponsiveness and histological changes in the trachea that resemble those seen in bronchopulmonary dysplasia.

Acute episodes of chronic obstructive pulmonary disease (COPD) often require endotracheal intubation (a tube inserted into the trachea, or windpipe, through an incision in the neck) and mechanical ventilation, or both. Among the complications arising from this procedure are hospital-acquired pneumonia, injury from the increased air pressure, and injury to the trachea. Previous attempts at noninvasive methods of ventilatory assistance are difficult for routine use and require cooperation from the patient. They are not sensitive to the patient's breathing, do not maintain even pressure, resist the patient's expiratory pressure, and are expensive. The new method described in this article, known as inspiratory pressure support, does not require intubation and was designed to be inexpensive. It provides partial ventilatory assistance through a face mask, applying constant positive pressure during the patient's spontaneous inspiration. This method improves blood gas exchange and, in intubated patients, reduces the work of the respiratory muscles during weaning from mechanical ventilation. To determine short-term physiologic effects, this method was tested on 11 patients with COPD, and 13 patients (6 from the previous group) with COPD and acute respiratory distress. These patients were matched with 13 patients whose COPD was treated conventionally. The results suggest that an external inspiratory-assistance device can improve blood gas exchange efficiency and decrease the work of the respiratory muscles. In most patients, endotracheal intubation was avoided, leading to shorter stays in the intensive care unit. During acute respiratory distress, a mouthpiece is necessary when patients breathe through their mouths; this requires the patient's cooperation and limits the usefulness of the device. The inspiratory-assistance face mask was well tolerated and there were no side effects. (Consumer Summary produced by Reliance Medical Information, Inc.)

ABBREVIATIONS. NCPAP, nasal continuous positive airway pressure; [V.sub.L], lung volume; WOB, work of breathing; RIP, respiratory inductance plethysmography; Pes, esophageal pressure; [V.sub.T], tidal ventilation; Δ[V.sub.L], change in lung volume; [C.sub.L], [...], Background. Constant-flow nasal continuous positive airway pressure (NCPAP) often is used in preterm neonates to recruit and maintain lung volume. Physical model studies indicate that a variable-flow NCPAP device provides more stable volume recruitment with less imposed work of breathing (WOB). Although superior lung recruitment with variable-flow NCPAP has been demonstrated in preterm neonates, corroborating WOB data are lacking. Objective. To measure and compare WOB associated with the use of variable-flow versus constant-flow NCPAP in preterm neonates. Methods. Twenty-four preterm infants who were receiving constant-flow NCPAP (means, SD) and had birth weight of 1024 ± 253 g, gestational age of 28 ± 1.7 weeks, age of 14 ± 13 days, and [FIO.sub.2] of 0.3 ± 0.1 were studied. Variable-flow and constant-flow NCPAP were applied in random order. We measured changes in lung volume and tidal ventilation ([V.sub.T]) by DC-coupled/calibrated respiratory inductance plethysmography as well as esophageal pressures at NCPAP of 8, 6, 4, and 0 cm [H.sub.2]O. Inspiratory WOB ([WOB.sub.I]) and lung compliance were calculated from the esophageal pressure and [V.sub.T] data using standard methods. WOB was divided by [V.sub.T] to standardize the results. Results. [WOB.sub.I] decreased at all CPAP levels with variable-flow NCPAP, with a maximal decrease at 4 cm [H.sub.2]O. [WOB.sub.I] increased at all CPAP levels with constant-flow CPAP. Lung compliance increased at all NCPAP levels with variable-flow, with a relative decrease at 8 cm [H.sub.2]O, whereas it increased only at 8 cm [H.sub.2]O with constant-flow NCPAP. Compared with constant-flow NCPAP, [WOB.sub.I] was 13% to 29% lower with variable-flow NCPAP. Conclusion. [WOB.sub.I] is decreased with variable-flow NCPAP compared with constant-flow NCPAP. The increase in [WOB.sub.I] with constant-flow NCPAP indicates the presence of appreciable imposed WOB with this device. Our study, performed in neonates with little lung disease, indicates the possibility of lung overdistention at CPAP of 6 to 8 cm [H.sub.2]O with the variable-flow device. Further study is necessary to determine the efficacy of variable-flow NCPAP in neonates with significant lung disease and its use over extended periods of time. Pediatrics 2001;108:682-685; continuous-flow and variable-flow NCPAP, work of breathing, premature neonates, lung compliance.

Objective. To determine whether lung volume changes and breathing pattern parameters differ among 3 devices for delivery of nasal continuous positive airway pressure (CPAP) in premature infants. Methods. Thirty-two premature infants receiving nasal CPAP for apnea or mild respiratory distress were enrolled. Birth weight was (mean [+ or -] standard deviation) 1081 [+ or -] 316 g, gestational age 29 [+ or -] 2 weeks, age at study 13 [+ or -] 12 days, and fraction of inspired oxygen ([FIO.sub.2]) at study .29 [+ or -] .1. Three devices, applied in random order, were studied in each infant: continuous flow nasal CPAP via CPAP prongs, continuous flow nasal CPAP via modified nasal cannula, and variable flow nasal CPAP. After lung recruitment to standardize volume history, changes in lung volume ([Delta][V.sub.L]) were assessed at nasal CPAP of 8, 6, 4, and 0 cm [H.sub.2]O using calibrated direct current-coupled respiratory inductance plethysmography. Results. [Delta][V.sub.L] was significantly greater overall with the variable flow device compared with both the nasal cannula and CPAP prongs. However, [Delta][V.sub.L] was not different between the cannula and the prongs. Respiratory rate, tidal volume, thoraco-abdominal asynchrony, and [FIO.sub.2] were greater with the modified cannula than for either of the other 2 devices. Conclusion. Compared with 2 continuous flow devices, the variable flow nasal CPAP device leads to greater lung recruitment. Although a nasal cannula is able to recruit lung volume, it does so at the cost of increased respiratory effort and [FIO.sub.2]. Pediatrics 2001;107: 304-308; nasal CPAP, lung volume changes, preterm infants, respiratory inductance plethysmography., ABBREVIATIONS. CPAP, continuous positive airway pressure; [Delta][V.sub.L], change in lung volume; RIP, respiratory inductance plethysmography; DC, direct current; [FIO.sub.2], fraction of inspired oxygen; [V.sub.T], tidal volume; AC, alternating current; RR, [...]