Feasibility and safety of ultra-low tidal volume ventilation without extracorporeal circulation in moderately severe and severe ARDS patients.

PURPOSE: Mechanical ventilation with ultra-low tidal volume (VT) during ARDS may reduce alveolar strain, driving pressure and hence ventilator-induced lung injury, with the main drawback of worsening respiratory acidosis. We hypothesized that VT could be reduced down to 4 ml/kg, with clinically significant decrease in driving pressure, without the need for extracorporeal CO2 removal, while maintaining pH > 7.20. METHODS: We conducted a non-experimental before-and-after multicenter study on 35 ARDS patients with PaO2/FiO2 ≤ 150 mmHg, within 24 h of ARDS diagnosis. After inclusion, VT was reduced to 4 ml/kg and further adjusted to maintain pH ≥ 7.20, respiratory rate was increased up to 40 min-1 and PEEP was set using a PEEP-FiO2 table. The primary judgment criterion was driving pressure on day 2 of the study, as compared to inclusion. RESULTS: From inclusion to day 2, driving pressure decreased significantly from 12 [9-15]  to 8 [6-11] cmH2O, while VT decreased from 6.0 [5.9-6.1] to 4.1 [4.0-4.7] ml/kg. On day 2, VT was below 4.2 ml/kg in 65% [CI95% 48%-79%], and below 5.25 ml/kg in 88% [CI95% 74%-95%] of the patients. 2 patients (6%) developed acute cor pulmonale after inclusion. Eleven patients (32%) developed transient severe acidosis with pH < 7.15. Fourteen patients (41%) died before day 90. CONCLUSION: Ultra-low tidal volume ventilation may be applied in approximately 2/3 of moderately severe-to-severe ARDS patients, with a 4 cmH2O median reduction in driving pressure, at the price of transient episodes of severe acidosis in approximately 1/3 of the patients.

[Medico-economic assessment of the Pontoise Hospital stroke unit]. / Évaluation médico-économique de l'unité neurovasculaire du centre hospitalier de Pontoise.

INTRODUCTION: Annually, approximately 120,000 people in France have a stroke. Various controlled studies have pointed out the benefits of treatment in a stroke unit (SU). The objective of this study was to evaluate, from a medical point of view, the economic impact of the Pontoise Hospital SU. PATIENTS AND METHODS: Based on the national cost study (NCS [étude nationale des coûts: ENC]) we analyzed data of five diagnosis related groups (DRG) which have a principle diagnosis in relation with stroke. This work was limited to strokes and transient ischemic events in adults and excluded sub-arachnoid hemorrhage. Medical and economic parameters were collected over the period from January to October 2006 and compared with those of the same period in 2005, that is to say before the opening of the SU. RESULTS: Three hundred and twenty-three hospital stays occurred between January 1st and October 31st, 2006 and 216 during the same time period before the opening of the SU, an increase of approximately 50% of all stroke-related admissions in our hospital. The number of stays carried out in the neurology unit increased by 29%. There was no significant difference between the two periods regarding age (median 69 versus 70 years) and sex- ratio. Average length of stay (ALS) was the same (9 days). There were no significant differences concerning the death rate (5.6% versus 6.2%) and that of discharge to home (44.6% versus 44.4%). The cost by stay in 2006 was 3534 euros [median; min 664-max 57,542] versus 3541 euros in 2005 [681-35,149] (p=0.57). Analysis by DRG highlighted an increase in the cost for serious strokes, cerebral infarctions and hemorrhages. For transitory ischemic events, the cost and the ALS decreased. CONCLUSION: After the opening of the SU, there was an increase in the activity without an increase in the total cost. This could be related in part to the limited means allocated to the stroke unit at its opening (in particular medical staff). The NCS can be used to evaluate the activity of a stroke unit. This work could be completed on a larger number of units or in several units of different size.

[Serial determination of crimidine by HPLC/SE/SM in a patient ingesting a "mouse trap"]. / Détermination sérique de la crimidine par CLHP/ES/SM chez un patient ayant ingere un "souricide foudroyant".

Crimidine (2 chloro, 4 methyl, 6 dimethyl amidopyrine) is a synthetic rodenticide which causes acute poisonings after oral ingestion in human. Major toxic effects are consciousness disorders, hypertonic coma and convulsions. Toxic level in human is about 5 mg/Kg. An intoxication case is reported. Five serums collected at different times were analyzed with HPLC/ES/MS. Crimidine was extracted with ethylacetate with recovery over 80%. Linearity was up to 800 micrograms/L. LOQ and LOD were 0.5 and 0.3 microgram/L respectively. The coefficients of variation were less than 10% for repeatability and reproductibility. Serum levels varied from 368 micrograms/L for H0 to 64 micrograms/L for H10 and elimination of crimidine was linear in time.

1H NMR spectroscopic investigation of serum and urine in a case of acute tetrahydrofuran poisoning.

This article reports the investigation by 1H nuclear magnetic resonance (1H NMR) spectroscopy of biological fluids in a case of intentional poisoning with tetrahydrofuran (THF). Occupational exposures to this solvent are well documented, but acute poisoning cases are extremely rare, and the one presented here is the second known case of this kind. Urine and serum samples were collected. Without any pretreatment, the presence of THF was confirmed by characteristic resonances at 1.90 and 3.76 ppm; high lactate levels were also observed. The presence of gamma-hydroxybutyric acid (GHB) was noted. Quantitative analysis was performed by relative integration of peak areas. THF concentrations were 813 and 850 mg/L (11.3 and 11.8 mmol/L), and GHB concentrations 239 and 2,977 mg/L (2.3 and 28.6 mmol/L) in serum and urine, respectively. A gas chromatographic-mass spectrometric method confirmed 1H NMR observations. The origin of GHB detected in serum and urine is also discussed.

Regional distribution of gas and tissue in acute respiratory distress syndrome. II. Physiological correlations and definition of an ARDS Severity Score. CT Scan ARDS Study Group.

OBJECTIVES: (a) To assess whether differences in lung morphology observed in patients with adult respiratory distress syndrome (ARDS) are associated with differences in cardiorespiratory parameters, lung mechanics, and outcome. (b) To propose a new ARDS Severity Score to identify patients with a high mortality risk. DESIGN: Prospective study over a 53-month period. SETTING: Fourteen-bed surgical intensive care unit of a university hospital. PATIENTS AND PARTICIPANTS: Seventy-one consecutive patients with early ARDS. MEASUREMENTS AND RESULTS: Cardiorespiratory parameters were measured using a Swan-Ganz catheter, the pressure-volume (PV) curve was measured using the gross syringe method, and fast spiral computed tomography (CT) was performed. Patients with diffuse attenuations (n = 16) differed from patients with lobar attenuations (n = 26) regarding: (a) mortality rate (75% vs. 42%, p = 0.05), (b) incidence of primary ARDS (82% vs. 50%, p = 0.03), (c) respiratory compliance (47 +/- 12 vs. 64 +/- 16 ml per cmH2O(-1) p = 0.04), and (d) lower inflexion point (8.4 +/- 2.0 vs. 4.6 +/- 2.0 cmH2O, p = 0.001). A third group of patients with patchy attenuations (n = 29) had a mortality rate of 41 %, a respiratory compliance of 56 +/- 18 ml per cmH2O(-1) and a lower inflexion point of 6.3 +/- 2.7 cmH2O. The bedside chest radiograph accurately assessed lung morphology in only 42% of the patients. In contrast to the scores based on the bedside chest radiograph, a new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters identified a subgroup of patients with a high mortality rate (> or = 60%). CONCLUSIONS: In patients with ARDS, differences in lung morphology are associated with differences in outcome and lung mechanics. A new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters accurately identified patients with the most severe forms of ARDS and a mortality rate above 60%.

Expiratory washout versus optimization of mechanical ventilation during permissive hypercapnia in patients with severe acute respiratory distress syndrome.

The aim of this study was to compare three ventilatory techniques for reducing PaCO2 in patients with severe acute respiratory distress syndrome treated with permissive hypercapnia: (1) expiratory washout alone at a flow of 15 L/min, (2) optimized mechanical ventilation defined as an increase in the respiratory frequency to the maximal rate possible without development of intrinsic positive end- expiratory pressure (PEEP) combined with a reduction of the instrumental dead space, and (3) the combination of both methods. Tidal volume was set according to the pressure-volume curve in order to obtain an inspiratory plateau airway pressure equal to the upper inflection point minus 2 cm H2O after setting the PEEP at 2 cm H2O above the lower inflection point and was kept constant throughout the study. The three modalities were compared at the same inspiratory plateau airway pressure through an adjustment of the extrinsic PEEP. During conventional mechanical ventilation using a respiratory frequency of 18 breaths/min, respiratory acidosis (PaCO2 = 84 +/- 24 mm Hg and pH = 7.21 +/- 0.12) was observed. Expiratory washout and optimized mechanical ventilation (respiratory frequency of 30 +/- 4 breaths/min) had similar effects on CO2 elimination (DeltaPaCO2 = -28 +/- 11% versus -27 +/- 12%). A further decrease in PaCO2 was observed when both methods were combined (DeltaPaCO2 = -46 +/- 7%). Extrinsic PEEP had to be reduced by 5.3 +/- 2.1 cm H2O during expiratory washout and by 7.3 +/- 1.3 cm H2O during the combination of the two modes, whereas it remained unchanged during optimized mechanical ventilation alone. In conclusion, increasing respiratory rate and reducing instrumental dead space during conventional mechanical ventilation is as efficient as expiratory washout to reduce PaCO2 in patients with severe ARDS and permissive hypercapnia. When used in combination, both techniques have additive effects and result in PaCO2 levels close to normal values.

A scanographic assessment of pulmonary morphology in acute lung injury. Significance of the lower inflection point detected on the lung pressure-volume curve.

The goal of this study was to assess lung morphology in patients with acute lung injury according to the presence or the absence of a lower inflection point (LIP) on the lung pressure-volume (P-V) curve and to compare the effects of positive end-expiratory pressure (PEEP). Eight patients with and six without an LIP underwent a spiral thoracic CT scan performed at zero end-expiratory pressure (ZEEP) and at two levels of PEEP: PEEP1 = LIP + 2 cm H2O and PEEP2 = LIP + 7 cm H2O, or PEEP1 = 10 cm H2O and PEEP2 = 15 cm H2O in the absence of an LIP. The volumes of air and tissue within the lungs were measured from the gas-tissue ratio and the volumes of overdistended and normally, poorly, and nonaerated lung areas were determined by the analysis of the frequency histogram distribution. In the ZEEP condition, although total lung volume, volume of gas, and volume of tissue were similar in both groups, the percentage of normally aerated lung was lower (24 +/- 22% versus 55 +/- 12%, p < 0.05) and the percentage of poorly aerated lung was greater (40 +/- 12% versus 23 +/- 8%, p < 0.05) in patients with an LIP than in patients without an LIP. Lung density histograms of patients with an LIP showed a unimodal distribution with a peak at 7 Hounsfield units (HU). Lung density histograms of patients without an LIP had a bimodal distribution, with a first peak at -727 HU and a second peak at 27 HU. Total respiratory system and lung compliances were lower in patients with an LIP whereas all other cardiorespiratory parameters were similar in the two groups. In both groups, PEEP induced an alveolar recruitment that was associated with lung overdistension only in patients without an LIP. The amount of lung overdistension was related to the volume of lung parenchyma, characterized by a CT number less than -800 HU before PEEP implementation (y = 0.52x + 4, R = 0.87, and p < 0.0001). This study shows that the presence or the absence of an LIP on the lung P-V curve is associated with differences in lung morphology. In patients without an LIP on the lung P-V curve, normally aerated lung areas coexist with nonaerated lung areas and increasing levels of PEEP result in lung overdistension rather than in additional alveolar recruitment. In patients with an LIP, air and tissue are more homogeneously distributed within the lungs and increasing levels of PEEP result in additional alveolar recruitment without lung overdistention.

A simple automated method for measuring pressure-volume curves during mechanical ventilation.

Measurement of respiratory compliance is advocated for assessing the severity of acute respiratory failure (ARF). Recently, the administration of an automated constant flow of 15 L/min was proposed as a method easier to implement at the bedside than supersyringe or inspiratory occlusions methods. However, pressure-volume (P-V) curves were shifted to the right because of the resistive properties of the respiratory system. The aim of this study was to compare the P-V curves obtained using two constant flows-3 and 9 L/min-during volume-controlled mechanical ventilation with those obtained with the supersyringe and the inspiratory occlusions methods. Fourteen paralyzed patients with ARF were studied. The supersyringe and the inspiratory occlusions methods were performed according to usual recommendations. The new automated method was performed during volume-controlled mechanical ventilation by setting the inspiratory:expiratory ratio at 80%, the respiratory frequency at 5 breaths/min, and the tidal volume at 500 or 1,500 ml. These peculiar ventilatory settings were equivalent to administering a constant flow of 3 or 9 L/min during a 9.6-s inspiration. Esophageal and airway pressures were recorded. P-V curves obtained by the 3-L/min constant-flow method were identical to those obtained by the reference methods, whereas the P-V curve obtained by the 9-L/min constant flow was slightly shifted to the right. The slopes of the P-V curves and the lower inflection points were not different between all methods, indicating that the resistive component induced by administering a constant flow equal to or less than 9 L/min is not of clinical relevance. Because the 3-L/min constant-flow method is not artifacted by the resistive properties of the respiratory system and does not require any other equipment than a ventilator, it is an easy-to-implement, inexpensive, safe, and reliable method for measuring the thoracopulmonary P-V curve at the bedside.

A lung computed tomographic assessment of positive end-expiratory pressure-induced lung overdistension.

The aim of this study was to assess positive end-expiratory pressure (PEEP)-induced lung overdistension and alveolar recruitment in six patients with acute lung injury (ALI) using a computed tomographic (CT) scan method. Lung overdistension was first determined in six healthy volunteers in whom CT sections were obtained at FRC and at TLC with a positive airway pressure of 30 cm H2O. In patients, lung volumes were quantified by the analysis of the frequency distribution of CT numbers on the entire lung at zero end-expiratory pressure (ZEEP) and PEEP. In healthy volunteers at FRC, the distribution of the density histograms was monophasic with a peak at -791 +/- 12 Hounsfield units (HU). The lowest CT number observed was -912 HU. At TLC, lung volume increased by 79 +/- 35% and the peak CT number decreased to -886 +/- 26 HU. More than 70% of the increase in lung volume was located below -900 HU, suggesting that this value can be considered as the threshold separating normal aeration from overdistension. In patients with ALI, at ZEEP the distribution of density histograms was either monophasic (n = 3) or biphasic (n = 3). The mean CT number was -319 +/- 34 HU. At PEEP 13 +/- 3 cm H2O, lung volume increased by 47 +/- 19% whereas mean CT number decreased to -538 +/- 171 HU. PEEP induced a mean alveolar recruitment of 320 +/- 160 ml and a mean lung overdistension of 238 +/- 320 ml. In conclusion, overdistended lung parenchyma of healthy volunteers is characterized by a CT number below -900 HU. This threshold can be used in patients with ALI for differentiating PEEP-induced alveolar recruitment from lung overdistension.

[Unstable angina and infarction without Q wave treated with verapamil: value of the early exercise test]. / Angor instable et infarctus sans Q traités par vérapamil: intérêt de l'épreuve d'effort précoce.

Twenty patients aged 56.8 +/- 10 years, hospitalised for unstable angina (12 cases) or infarct without Q wave (8 cases) were treated with IV heparin, aspirin and oral verapamil. The clinical syndrome was controlled by verapamil in 16 cases out of 20 (80% of cases) at the dosage of 360 mg/d in 14 patients and of 480 mg/d in two. An exercise ECG, limited by symptoms, was obtained in 18 patients (90%) between the 8th and 12th day. Coronary arteriography was considered to be indicated in three sets of circumstances: recurrence of angina resistant to nitroglycerin, positive exercise ECG with verapamil, persisting despite triple therapy or strongly positive exercise ECG (total duration less than or equal to 6 minutes). An infarct complicated the early course in 4 patients (20%): twice following angioplasty, once following exercise ECG (spastic angina) and once during triple therapy (refractory angina). Hospital and mid-term (18 +/- 6 months) mortality was nil. With verapamil, the absence of recurrence of angina together with a negative exercise ECG enabled the identification of a large group of patients (40%) with a low risk of a subsequent major accident and in whom early and routine coronary arteriography is probably not indispensable.