[Efficacy of a multidisciplinary team for preventing hospital-acquired invasive aspergillosis: five years' experience]. / Efficacité des mesures environnementales dans la prévention de l'aspergillose invasive nosocomiale liée aux travaux: bilan de cinq années d'expérience.

Invasive hospital-acquired aspergillosis (IA) is responsible for lethal outbreaks. In 2002, an interdisciplinary team was created in the teaching hospital of Rouen in order to organize the surveillance of construction sites by the implementation of environmental measures of prevention. The aim of our study was to estimate the efficiency of these measures using an indirect indicator, reflecting the incidence of the cases of invasive nosocomial aspergillosis (AI): the consumption of antifungals. From the nominative prescriptions established, we studied the medical files about 210 patients to track down the number of IA cases in intensive care unit (ICUI) and in pediatric hematology-oncology units between 2002 and 2006. The incidence of the cases was put in parallel with the various periods of level 5-risk works during these five years. The relative risk of appearance of the disease was calculated. In pediatric haematology-oncology unit, 35 cases were diagnosed on 99 medical files which have been studied and in ICU 19 cases were classified on 93 studied files. The follow-up of the incidence in both units stake in parallel with the periods of level 5-risk works does not show increase of the number of cases. The calculated relative risk indicates the same result: the level 5-risk works are not a factor facilitating the appearance of invasive aspergillosis cases. This study shows the importance of the environmental measures of prevention during the periods of works within services for risk. The coordination of the actors within an interdisciplinary cell seems thus essential for the prevention of AIN.

Changes in severity and organ failure scores as prognostic factors in onco-hematological malignancy patients admitted to the ICU.

OBJECTIVE: To determine whether severity and organ failure scores over the first 3 days in an ICU predict in-hospital mortality in onco-hematological malignancy patients. DESIGN AND SETTING: Retrospective study in a 22-bed medical ICU. PATIENTS: 92 consecutive patients with onco-hematological malignancies including 20 hematopoietic stem cell transplantation (HSCT) patients (11 with allogenic HSCT). MEASUREMENTS: Simplified Acute Physiology Score (SAPS) II, Organ Dysfunction and/or Infection (ODIN) score, Logistic Organ Dysfunction System (LODS), and Sequential Organ Failure Assessment (SOFA) score were recorded on admission. The change in each score (Delta score) during the first 3 days in the ICU was calculated as follows: severity or organ failure score on day 3 minus severity or organ failure score on day 1, divided by severity or organ failure score on day 1. RESULTS: In-hospital mortality was 58%. Using multivariate analysis in-hospital mortality was predicted by all scores on day 1 and all Delta scores. Areas under the receiver operating characteristics curves were similar for SAPS II (0.78), ODIN (0.78), LODS (0.83), and SOFA (0.78) scores at day 1. They were also similar for DeltaSAPS II, DeltaODIN, DeltaLODS, and DeltaSOFA. Similar results were observed when excluding patients with allogenic HSCT. CONCLUSION: Severity and three organ failure scores on day 1 and Delta scores perform similarly in predicting in-hospital mortality in ICU onco-hematological malignancy patients but do not predict individual outcome. Decision to admit such patients to the ICU or to forgo life-sustaining therapies should not be based on these scores.

Serum erythropoietin levels in septic shock.

Erythropoietin is a glycoprotein hormone mainly released by the kidney, which stimulates red blood cell production. However, in sepsis, the mechanisms responsible for the final increase in circulating erythropoietin remain unclear Seventeen critically ill patients with Simplified Acute Physiologic Score average 66 (range 43 to 103) were included in this study. Ten patients survived and seven died within 28 days. Blood samples obtained at different times were assayed for erythropoietin, cytokine levels and lactate measurements. PCO2 gap was assessed to detect the presence of gastric mucosal acidosis. Erythropoietin decreased in the patients who survived while it remained high or increased in non-survivors (37+/-6.5 vs 147+/-6. 7 UI/l respectively, P<0.05). Erythropoietin plasma levels were correlated with IL-6 levels (r=0.84, P<0.05) and TNFalpha levels (r=0.84, P<0.05). We observed a significant positive relationship between erythropoietin plasma levels and lactate concentrations (r= 0.89, P< 0. 05) and with PCO2 gap (r=0.9, P < 0.05). No correlation was found between erythropoietin concentration and the other parameters. High serum erythropoietin levels in non-survivors were observed with septic shock despite an increase in the levels of proinflammatory cytokines. We found a relationship between erythropoietin concentration and biological markers of tissue hypoperfusion i.e. lactate levels or PCO2 gap. This relationship could suggest tissue hypoperfusion as the stimulating factor for erythropoietin production in septic shock.

Rapid and beneficial hemodynamic effects of activated protein C in septic shock patients.

OBJECTIVE: Because recombinant human activated protein C (rhAPC) reduces NO production during sepsis, it could improve the vascular tone. We tested whether rhAPC reduces the dose of norepinephrine required to maintain mean arterial pressure (MAP) in septic shock patients. DESIGN AND SETTING: Retrospective study in intensive care unit of two university hospitals. PATIENTS: Twenty-two septic shock patients with at least two organ failures were retrospectively investigated for MAP and the required dose of norepinephrine before and 24 h after rhAPC administration. A control group of 22 septic shock patients with at least two organ failures who did not receive rhAPC was matched on age, SAPS II, MAP, and norepinephrine dose at the time of the theoretical start of rhAPC. MEASUREMENTS AND RESULTS: The MAP remained stable and similar in the two groups (86+/-16 vs. 89+/-9 mmHg at 24 h). The required dose of norepinephrine increased in the control group (+38%, from -41% to +38%) but decreased in the treated group (-33%, from -74% to +11%). CONCLUSIONS: rhAPC rapidly improved the vascular tone in septic shock patients as assessed by a decrease in the norepinephrine dose required to maintain arterial pressure.

[Bickerstaff's brainstem encephalitis]. / La rhombencéphalite postinfectieuse: le syndrome de Bickerstaff.

INTRODUCTION: Bickerstaff's brainstem encephalitis represents a differential diagnostic that must be discuss with meningoencephalitis with ophtalmoplegia, ataxia and confusion. EXEGESE: A 26 year-old woman presented a Bickerstaff syndrome. A severe disturbance of consciousness had lead to admission in intensive care unit with mechanical ventilation. Electrophysiological tests and the brain magnetic resonance were normal. We have not observed systemic anti-G1Qb antibody in our patient. Nevertheless, 66% of patients with Bickerstaff syndrome have anti-GQ1b antibody during the acute phase period. We observed a beneficial effect of IV Ig treatment although no significant improvement was observed with corticosteroids. CONCLUSION: Controlled clinical trials are needed to established the efficacy of IV Ig or plasmapheresis as a specific therapy for this pathology.

[Complications during the intrahospital transport in critically ill patients]. / Complications durant le transport intrahospitalier de malades critiques de réanimation.

INTRODUCTION: Intrahospital transport (IHT) of mechanically ventilated critically ill patients is associated with an important risk of complications. OBJECTIVES: The purpose of this study was to assess the incidence of complications occurring during the IHT and to analyse the causes and the consequences of such complications. PATIENTS AND METHODS: All the IHT performed in mechanically ventilated patients, hospitalised in medical and surgical intensive care units of a university hospital were prospectively included during a three-month period. Complications were defined as follows: patient related problems (desaturation, restlessness, haemodynamic instability, extubation) and ventilator related problems (breakdown or defect of the material). RESULTS: 123 IHT concerning 64 patients were analysed, with 64 IHT were realised for diagnostic procedure (computed tomography) and 59 for therapeutic procedure (surgical procedure or interventional radiology). At least one patient related problem occurred during 41 IHT (33%) (desaturation n = 11, agitation n = 21, haemodynamic alterations n = 19, extubation n = 0). In two patients, these complications led to cardiac arrest. Patient related problems were observed more frequently in sedated patient (66 %, p = 0.0001) as well as during IHT for diagnostic procedure (p = 0.03). A ventilator problem occurred in 26 transports (21 %) and was more frequently reported when a turbine ventilator was used (p = 0.0056). CONCLUSION: This study supports the fact that IHT of mechanically ventilated critically ill patients, is a high-risk procedure associated with potentially severe complications. This finding emphasises the need of standardised procedures and medical surveillance during IHT.

[VENISE: Non-invasive ventilation during mechanical ventilation weaning in chronic respiratory failure patients. A prospective randomised controlled and multicenter trial]. / VENISE: VEntilation Non Invasive au cours du SEvrage de la ventilation mécanique des patients insuffisants respiratoires chroniques. Une étude prospective contrôlée randomisée multicentrique.

INTRODUCTION: The clinical efficacy of non-invasive ventilation (NIV) has now been demonstrated in the management of acute-on-chronic respiratory failure (ACRF) in various etiologies. Endotracheal mechanical ventilation (ETMV) can lead to numerous complications and weaning difficulties increasing the risk of prolonged ETMV, morbidity and mortality as well as excess cost of intensive care. Therefore, it could be useful to consider NIV for delivering effective ventilatory support to reduce the length of ETMV in ACRF patients who are still not capable of maintaining spontaneous breathing. From the interesting but discordant results of two recent randomised controlled trials, a working group from the Société de Réanimation de Langue Française (SRLF) decided to perform a new prospective randomised controlled multicenter trial. The aim of the study will be to assess the usefulness of NIV as an extubation and weaning technique in ventilated ACRF patients. METHODS: The methodology used will compare three parallel weaning strategies in ACRF patients considered difficult to wean: invasive conventional weaning (group A), extubation relayed by nasal oxygentherapy (group B), and extubation relayed by NIV (group C). Based on the main end-point defined as the weaning success rate, 208 patients from 17 investigator centers are planned to be included. Results of the study will also allow to assess the respective impact of the three weaning strategies on the length of ETMV and weaning, the mechanical ventilation-related morbidity, the patients lengths of stay and mortality. EXPECTED RESULTS: Results of the VENISE trial should permit to improve the management of the difficult to wean ACRF patients and thus contribute to more precisely define the place of NIV in the weaning and prevention of re-intubation strategies in these patients.

Induction of heme-oxygenase-1 prevents the systemic responses to hemorrhagic shock.

Oxidant-mediated reperfusion injury of the gut is a major contributor of the systemic inflammatory response in hemorrhagic shock. Recent studies have suggested that heme-oxygenase-1 (HO-1) represents an endogenous protective mechanism against oxidant stress. We assessed whether HO-1 induction modulates the synthesis of tumor necrosis factor-alpha (TNF-alpha) in hemorrhagic shock. In rats submitted to hemorrhagic shock, pretreatment with hemoglobin (Hb) increased HO-1 mRNA expression in macrophages. This increased expression was associated with a decreased expression of TNF-alpha mRNA, as well as decreased plasma concentrations of TNF-alpha. These effects of Hb were reduced by the HO-1 inhibitor tin-protoporphyrin (Sn-PP 20 micromol/kg), while Sn-PP had no effect in the absence of Hb. In parallel, Hb pretreatment reduced pulmonary edema, vascular injury, and increased mesenteric blood flow, and these effects were reduced by Sn-PP. Thus, induction of HO-1 is protective in hemorrhagic shock, possibly through its antioxidant properties. Interventions that induce HO-1 may be beneficial in the treatment of shock states, leading to a reduced systemic inflammatory response.

[Acute respiratory failure in patients with chronic respiratory insufficiency]. / Défaillance aiguë des insuffisances respiratoires chroniques.

In the absence of severe clinical signs requiring endotracheal intubation, non-invasive mechanical ventilation is the first-line treatment in patients with chronic respiratory insufficiency. For a patient with non-invasive support, the probability to avoid intubation is 2 or 3 times higher than for a patient initially treated by oxygen therapy alone. Oxygen therapy will remain the recommended approach for staff unfamiliar with non-invasive support. In chronic obstructive pulmonary disease (COPD) ventilated patients, keeping the intrinsic positive end-expiratory pressure to a minimum level decreases the risk of barotrauma. During exacerbation, in these patients, the 3 most often prescribed medications are inhaled bonchodilators, corticosteroids, and antibiotics. In addition to long term home oxygen therapy, the preventive measures include education of patients, pulmonary rehabilitation programs, and eventually routine use of ventilatory support in a home ventilatory setting.

Two cases of foodborne botulism type E and review of epidemiology in France.

In 1999, two new cases of type E botulism were observed in French hospitals. Since this type of botulism is uncommon in France, the cases prompted a national epidemiological study. Sixteen cases of type E botulism, including the two cases reported here, occurred between 1952 and 1999. The clinical and treatment characteristics of all cases were evaluated, and the results suggest that, despite its rarity, type E botulism should be considered by clinicians in France. Changes in the eating habits of people in France, as in the rest of Europe, with the increased consumption of vacuum-packed fish from endemic areas and decreased consumption of local foodstuffs, could explain the occurrence of the most recent cases.

Reduced synthesis of inflammatory cytokines by a free radical scavenger after hemorrhagic shock in rats.

OBJECTIVES: Intestinal ischemia/reperfusion during hemorrhage and resuscitation may be a major trigger for cytokine expression. To assess whether free radicals produced on tissue reperfusion may play a role in the inflammatory response after hemorrhage, we tested the effect of a free radical scavenger on the production of inflammatory cytokines in a rat model of hemorrhagic shock. DESIGN: A prospective, controlled animal study. SETTING: A university research laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Hemorrhage was induced in anesthetized rats. by bleeding the animal to achieve a mean arterial blood pressure of 40 mm Hg for 60 mins. Resuscitation was then induced by reinjecting shed blood followed by NaCl 0.9% to maintain arterial blood pressure within control values. Treated rats received the free radical scavenger N-2-mercaptopropionyl glycine (MPG; 20mg/kg iv bolus 30 mins before resuscitation followed by 20 mg/kg/hr). MEASUREMENTS AND MAIN RESULTS: MPG reduced the volume of saline necessary to restore blood pressure during resuscitation (untreated 85+/-6; MPG 35+/-5 mL/kg; p < .05). As compared with untreated rats, MPG markedly reduced the systemic and mesenteric plasma concentrations of tumor necrosis factor (TNF)-alpha (as measured by ELISA) and interleukin (IL)-6 (as measured by bioassay), assessed at the end of resuscitation. MPG also reduced TNF-alpha and IL-6 mRNA expression (as measured by reverse transcriptase-polymerase chain reaction) assessed in peritoneal macrophages isolated from shock rats. Finally, in vitro experiments showed that MPG also markedly reduced the mRNA expression and release of TNF-alpha and IL-6 in peritoneal macrophages isolated from normal rats and subjected to hypoxia and reoxygenation. CONCLUSION: Reactive oxygen species contribute to the production of proinflammatory cytokines during posthemorrhage resuscitation. Free radicals scavengers may be a useful treatment in the prevention of the systemic inflammatory response that occurs in shock states.

Fomepizole (4-methylpyrazole) in fatal methanol poisoning with early CT scan cerebral lesions.

BACKGROUND: Methanol poisoning, potentially fatal, is generally treated with the combination of ethanol as antidote, and hemodialysis. Fomepizole, a competitive inhibitor of alcohol dehydrogenase, has more recently been used, and is capable of blocking the toxic metabolism of methanol. To our knowledge, its use has never been reported as an antidote in severe methanol poisoning requiring hemodialysis. CASE REPORT: We report a case of fatal methanol poisoning (1.9 g/L on admission) suspected due to the combined presence of coma and severe metabolic acidosis with normokalaemia. CONCLUSION: The fomepizole treatment protocol (10 mg/kg by i.v. infusion over 1 hour before dialysis, repeated 12 hours later in combination with 1.5 mg/kg/h during dialysis) was simple to use and appeared effective in eliminating methanol in combination with hemodialysis. The case is also unusual in terms of severity and the early onset of cerebral lesions demonstrated by computed tomography (CT) scan.

Noninvasive ventilation as a systematic extubation and weaning technique in acute-on-chronic respiratory failure: a prospective, randomized controlled study.

Prolonged duration of endotracheal mechanical ventilation (ETMV) is associated with an increased morbidity and mortality in intensive care unit (ICU) patients. The aim of this study was to assess the usefulness of noninvasive ventilation (NIV) as a systematic extubation and weaning technique to reduce the duration of ETMV in acute-on-chronic respiratory failure (ACRF). Among 53 consecutively intubated patients admitted for ACRF, we conducted a prospective, randomized controlled trial of weaning in 33 patients who failed a 2-h T-piece weaning trial (2 h-WT) although they met simple criteria for weaning. Conventional invasive pressure support ventilation (IPSV) was used as the control weaning technique in 16 patients (IPSV group), and NIV was applied immediately after extubation in 17 patients (NIV group). The two weaning groups were similar for type of chronic respiratory failure (CRF), pulmonary function data, age, Simplified Acute Physiology Score (SAPS II), and severity of ACRF on admission. The characteristics of the two groups were also similar at randomization. In the IPSV group, 12 of 16 patients (75%) were successfully weaned and extubated, versus 13 of 17 (76.5%) in the NIV group (p = NS). NIV like IPSV significantly and similarly improved gas exchange in relation to that achieved during 2 h-WT (p < 0.05). The duration of ETMV was significantly shorter in the NIV (4.56 +/- 1.85 d) than in the IPSV group (7.69 +/- 3.79 d) (p = 0. 004). NIV also reduced the mean period of daily ventilatory support, but increased the total duration of ventilatory support related to weaning (3.46 +/- 1.42 d, versus 11.54 +/- 5.24 d with NIV; p = 0. 0001). Most patients in the IPSV group developed complications related to ETMV and/or the weaning process, but the difference was not significant (nine of 16 versus six of 17). The durations of ICU and hospital stays and the 3-mo survival were similar in the two groups. In conclusion, NIV permits earlier removal of the endotracheal tube than with conventional IPSV, and reduces the duration of daily ventilatory support without increasing the risk of weaning failures. NIV should be considered as a new and useful systematic approach to weaning in patients with ACRF who are difficult to wean.

Effects of pressure ramp slope values on the work of breathing during pressure support ventilation in restrictive patients.

OBJECTIVE: To investigate, in restrictive patients, the influence of pressure ramp slope values on the efficacy of pressure support ventilation. DESIGN: Prospective study. SETTING: A university hospital medical intensive care unit. PATIENTS: Twelve intubated restrictive patients. INTERVENTIONS: Patients were randomly assigned to four sequences in which the values of the slope of the pressure ramp increase were modulated so that the plateau pressure was reached within a predetermined time: 0.1, 0.50, 1, or 1.50 secs. The more rapidly the pressure plateau was achieved, the higher was the initial flow rate. For convenience, these four different ventilatory settings were termed T 0.1, T 0.5, T 1, and T 1.5. MEASUREMENTS AND MAIN RESULTS: We measured the following parameters 10 mins after application of each pressure ramp slope: inspiratory work of breathing, breathing pattern, and intrinsic PEEP (PEEPi). Work of breathing was evaluated using Campbell's diagram, and expressed as a percentage of the values observed under spontaneous ventilation. A marked interindividual variation of the values for work of breathing was observed under spontaneous ventilation; the mean value for work of breathing was 1.97 +/- 0.82 joule/L, with a range of 1.22 to 4.10 joule/L. Comparison between the means for each sequence and each variable measured was performed by two-way analysis of variance with internal comparisons between sequences by Duncan's test. Between the first (T 0.1) and the last (T 1.5) sequence, the reduction of values of the pressure ramp slope induced a progressive increase in the values for work of breathing, regardless of the mode of expression (in joule, joule/L, or joule/min). The values for work of breathing (joule/ L), expressed as a percentage of the values observed under spontaneous ventilation, increased from 44.2 +/- 14.4% to 78.3 +/- 17.8% (p < .001). In contrast, the reduction of the pressure ramp slope values and initial flow rate did not induce any significant change in tidal volume, respiratory frequency, and PEEPi. CONCLUSION: Among the four tested slope values, the steepest was that which induced the lowest possible work of breathing in restrictive patients ventilated by pressure support ventilation. In this type of patient, we therefore suggest that the programmed pressure value should be reached by using a steep pressure ramp slope.

Induction of haem oxygenase contributes to the synthesis of pro-inflammatory cytokines in re-oxygenated rat macrophages: role of cGMP.

Macrophage activation and the resulting inflammatory response may be a major component of tissue injury upon hypoxia and re-oxygenation. Activation of the haem oxygenase (HO)/carbon monoxide (CO) pathway may be an important regulator of the inflammatory response, through production of cyclic 3', 5'-monophosphate (cGMP). We have assessed whether HO contributes to the increased production of the pro-inflammatory cytokines TNF-alpha and IL-6 in re-oxygenated rat peritoneal macrophages.Hypoxia/re-oxygenation markedly increased levels of HO-1 mRNA and cGMP. The increase in cGMP was reduced by the HO-1 inhibitor tin-protoporphyrin (SnPP-9) given during re-oxygenation. Hypoxia and re-oxygenation also increased IL-6 and TNF-alpha mRNA expression, as well as IL-6 and TNF-alpha concentrations in the cell supernatant. These increases were nullified by SnPP-9 and by Methylene Blue, an inhibitor of guanylate cyclase, but were not affected by L-NNA, an inhibitor of NO synthesis. The inhibitory effect of SnPP on the synthesis of cytokines was reversed by co-administration of the stable analogue of cGMP, 8-Br-cGMP. Our results indicate that activation of haem oxygenase and of the CO/cGMP pathway is a major stimulus for the synthesis and release of pro-inflammatory cytokines in re-oxygenated macrophages. This pathway may play a central role in pathological situations in which local tissue hypoxia/re-oxygenation triggers a systemic inflammatory response, for example in patients with shock.

Unplanned extubation: risk factors of development and predictive criteria for reintubation.

OBJECTIVES: To define patients at risk for unplanned extubation; to assess the influence of nursing workload on the incidence of unplanned extubation; and to determine predictive criteria for patients requiring reintubation. DESIGN: A prospective, case-control study, with 10 and 15 mos of data collection. SETTING: University medical intensive care department. PATIENTS: In the first study, which lasted 10 mos, unplanned extubation occurred in 40 (14%) of 281 ventilated and intubated patients; 36 cases were sufficiently documented to be compared with 74 intubated and ventilated controls. In the second study, which lasted 15 mos, the reintubated patients (n=23) of a series of 62 unplanned extubation patients were compared with those who were not reintubated (n=39). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The following parameters were recorded: gender, age, main reason for admission, Simplified Acute Physiology Score II, route of intubation (oral or nasotracheal), tube diameter, ventilatory mode, FiO2, frequency and tidal volume delivered by the ventilator immediately before unplanned extubation, arterial blood gases performed 24 hrs before unplanned extubation, the presence of any sedation with, in this case, the last Ramsay score, the presence of hand restraints, the presence of weaning of ventilation, the accidental or deliberate nature of unplanned extubation, the Glasgow Coma Score at the time of unplanned extubation, the duration of ventilation before unplanned extubation, total duration of ventilation and stay in the intensive care unit, and the patient's survival or death. The nursing workload was evaluated using a score derived from the Projet de Recherche en Nursing and adapted to intensive care. Unplanned extubation patients were more frequently intubated orally than controls (33.3% vs. 14.9%, respectively; p< .05). In the population of sedated patients, unplanned extubation patients were more frequently agitated than controls (60% vs. 19%, respectively; p < .05). The nursing workload did not differ between days with and days without unplanned extubation. Twenty-three (37%) of the 62 cases of documented unplanned extubation were reintubated. Predictive factors of reintubation are, in decreasing order of importance: Glasgow Coma Score of <11, accidental nature of unplanned extubation, and a PaO2/FiO2 ratio <200 torr (<26.7 kPa). CONCLUSIONS: Patients at risk for unplanned extubation are characterized by oral intubation and insufficient sedation. In the department studied, and with the specific score used, we did not observe a relationship between the nursing workload and the incidence of unplanned extubation. A Glasgow Coma Score of <11, the accidental nature of unplanned extubation, and a PaO2/FiO2 ratio <200 torr (<26.7 kPa) are factors associated with a risk of reintubation.

Lactobacillus species as emerging pathogens in neutropenic patients.

The intensive use of broad-spectrum antibiotics in the context of prolonged and severe neutropenia has contributed to the emergence of unusual pathogens. Four new cases of severe Lactobacillus infections-three of septicemia and one of pneumonia-are reported. They occurred in patients with acute leukemia who had chemotherapy-induced neutropenia. All patients were treated in the same intensive care unit and received the same antimicrobial prophylaxis which included a total bowel decontamination containing vancomycin. The four patients were treated with a combination of intravenous ceftazidime and vancomycin prior to the development of Lactobacillus infection. Improvement in the condition of all patients was obtained with a treatment including penicillin and concurrent recovery of granulopoiesis.

Physiological effects and optimisation of nasal assist-control ventilation for patients with chronic obstructive pulmonary disease in respiratory failure.

BACKGROUND: A study was undertaken to investigate the effects of non-invasive assist-control ventilation (ACV) by nasal mask on respiratory physiological parameters and comfort in acute on chronic respiratory failure (ACRF). METHODS: Fifteen patients with chronic obstructive pulmonary disease (COPD) were prospectively and randomly assigned to two non-invasive ventilation (NIV) sequences in spontaneous breathing (SB) and ACV mode. ACV settings were always optimised and therefore subsequently adjusted according to patient's tolerance and air leaks. RESULTS: ACV significantly decreased all the total inspiratory work of breathing (WOBinsp) parameters, pressure time product, and oesophageal pressure variation in comparison with SB mode. The ACV mode also resulted in a significant reduction in surface diaphragmatic electromyographic activity to 36% of the control values and significantly improved the breathing pattern. SB did not change the arterial blood gas tensions from baseline values whereas ACV significantly improved both the PaO2 from a mean (SD) of 8.45 (2.95) kPa to 13.31 (2.15) kPa, PaCO2 from 9.52 (1.61) kPa to 7.39 (1.39) kPa, and the pH from 7.32 (0.03) to 7.40 (0.07). The respiratory comfort was significantly lower with ACV than with SB. CONCLUSIONS: This study shows that the clinical benefit of non-invasive ACV in the management of ACRF in patients with COPD results in a reduced inspiratory muscle activity providing an improvement in breathing pattern and gas exchange. Despite respiratory discomfort, the muscle rest provided appears sufficient when ACV settings are optimised.