Noninvasive ventilation for acute respiratory failure: a prospective randomised placebo-controlled trial.

The aim of the present study was to clarify whether the known effects of noninvasive positive-pressure ventilation (NPPV) in patients with respiratory failure are real or due to placebo effects and whether early application of NPPV in the emergency department leads to rapid improvement of the patients condition and outcome. A prospective randomised placebo-controlled study was conducted in 20 patients with severe acute respiratory failure (ARF) secondary to an acute exacerbation of chronic obstructive pulmonary disease (COPD) or acute pulmonary oedema, not improving under conventional medical therapy and on the edge of intubation. Patients received either conventional medical therapy plus two-level NPPV (hi-level NPPV) or conventional medical therapy plus "placebo" NPPV. The main outcome measures involved the need for endotracheal intubation in the bi-level NPPV arm and in the placebo arm after crossing over to active NPPV. Morbidity, length of stay, mortality and the effect of the ventilatory mode on clinical, arterial-blood gas parameters, and the sternocleidomastoid muscles electromyogram (EMG) activity were also measured. The 10 patients in the active NPPV group rapidly improved and none needed intubation. Placebo NPPV resulted in no change in the clinical condition of patients that continued to worsen and the 10 patients were crossed over to active NPPV. Three patients were intubated. No differences in terms of morbidity, length of stay or mortality between the two groups were observed. Active NPPV (but not placebo NPPV) led to a rapid and significant improvement in the clinical parameters, pH and the carbon dioxide tension in arterial blood and to a decrease in respiratory frequency and sternocleidomastoid EMG activity. Early application of bi-level noninvasive positive-pressure ventilation in patients with severe acute respiratory failure, due to chronic obstructive pulmonary disease and acute pulmonary oedema, leads to a rapid improvement in clinical status and blood gases. Noninvasive positive-pressure ventilation had no placebo effect.

PaCO(2)/ETCO(2) gradient: early indicator of thrombolysis efficacy in a massive pulmonary embolism.

End tidal CO(2) measurement may be helpful in detecting the efficacy of thrombolysis after a massive pulmonary embolism. We report the case of a 76-year-old man with a massive pulmonary embolism, who required early intubation and mechanical ventilation. Thrombolysis with rtpA (total dosage: 60 mg) was initiated. During this procedure, clinical data, arterial blood gases and end-tidal CO(2) with a capnograph were recorded. Before thrombolysis the P(a-ET)CO(2) gradient was raised to 25 mmHg. During thrombolysis, the clinical data improved and the P(a-ET) gradient fell to 14 mmHg. We postulate that the P(a-ET)CO(2) gradient seems to be a reasonable indicator of efficacy of thrombolysis in this setting. However, the gradient did not return to normal values (4-5 mmHg). The possible reasons for this may be that during mechanical ventilation there was a large ventilation-perfusion ratio and the cardiac output may have still reduced. With these limitations, we conclude that the P(a-ET)CO(2) gradient should be evaluated as an indicator of pulmonary reperfusion in massive pulmonary embolism.

Effects of helium-oxygen on intrinsic positive end-expiratory pressure in intubated and mechanically ventilated patients with severe chronic obstructive pulmonary disease.

OBJECTIVE: To test the hypothesis that replacing 70:30 nitrogen: oxygen (Air-O2) with 70:30 helium:oxygen (He-O2) can decrease dynamic hyperinflation ("intrinsic" positive end-expiratory pressure) in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD), and to document the consequences of such an effect on arterial blood gases and hemodynamics. DESIGN: Prospective, interventional study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Twenty-three intubated, sedated, paralyzed, and mechanically ventilated patients with COPD enrolled within 36 hrs after intubation. INTERVENTIONS: Measurements were taken at the following time points, all with the same ventilator settings: a) baseline; b) after 45 mins with He-O2; c) 45 mins after return to Air-O2. The results were then compared to those obtained in a test lung model using the same ventilator settings. MAIN RESULTS (MEAN + SD): Trapped lung volume and intrinsic positive end-expiratory pressure decreased during He-O2 ventilation (215+/-125 mL vs. 99+/-15 mL and 9+/-2.5 cm H2O vs. 5+/-2.7 cm H2O, respectively; p < .05). Likewise, peak and mean airway pressures declined with He-O2 (30+/-5 cm H2O vs. 25+/-6 cm H2O and 8+/-2 cm H2O vs. 7+/-2 cm H2O, respectively; p < .05). These parameters all rose to their baseline values on return to Air-O2 (p < .05 vs. values during He-O2). These results were in accordance with those obtained in the test lung model. There was no modification of arterial blood gases, heart rate, or mean systemic arterial blood pressure. In 12/23 patients, a pulmonary artery catheter was in place, allowing hemodynamic measurements and venous admixture calculations. Switching to He-O2 and back to Air-O2 had no effect on pulmonary artery pressures, right and left ventricular filling pressures, cardiac output, pulmonary and systemic vascular resistance, or venous admixture. CONCLUSION: In mechanically ventilated COPD patients with intrinsic positive end-expiratory pressure, the use of He-O2 can markedly reduce trapped lung volume, intrinsic positive end-expiratory pressure, and peak and mean airway pressures. No effect was noted on hemodynamics or arterial blood gases. He-O2 might prove beneficial in this setting to reduce the risk of barotrauma, as well as to improve hemodynamics and gas exchange in patients with very high levels of intrinsic positive end-expiratory pressure.

Adult liver transplantation: UCL experience.

OBJECTIVE: To evaluate the impact of standardized operative and peri-operative care on the outcome of liver transplantation in a single center series of 395 adult patients. METHOD AND MATERIAL: Between February 1984 and December 31, 1998, 451 orthotopic liver transplantations were performed in 395 adult patients (> or = 15 years) at the University Hospitals St-Luc in Brussels. Morbidity and mortality of the periods 1984-1990 (Gr I--174 pat.) and 1991-1998 were compared (Gr II--221 pat.). During the second period anti-infectious chemotherapy and perioperative care were standardized and surgical technique changed from classical orthotopic liver transplantation with recipients' vena cava resection (and use of veno-venous bypass) towards liver implantation with preservation of the vena cava (without use of bypass). Immunosuppression was cyclosporine based from 1984 up to 1996 and tacrolimus based during the years 1997 and 1998. Immunosuppression was alleviated during the second period due to change from quadruple to triple and even double therapy and due to the introduction of low steroid dosing and of steroid withdrawal, once stable graft function was obtained. Indications for liver grafting were chronic liver disease (284 pat--71.9%), hepatobiliary tumor (52 pat--13.2%), acute liver failure (40 pat--10.1%) and metabolic disease (19 pat--4.8%). Regrafting was necessary because of graft dysfunction (21 pat), technical failure (12 pat), immunological failure (18 pat) and recurrent viral allograft disease (5 pat); three of these patients were regrafted at another institution. Follow-up was complete for all patients with a minimum of 9 months. RESULTS: Actuarial 1, 5 and 10 years survival rates for the whole group were 77.9%, 65.7% and 58.3%. These survival rates were respectively 77.3%, 69.7%, 62.5% and 73.2%, 59.6% 51.4% for benign chronic liver disease and acute liver failure; those for malignant liver disease were 80.6%, 44.3% and 36.7%. Early (< 3 months) and late (> 3 months) posttransplant mortalities were. 14.4% (57 pat) and 21.2% (84 pat). Early mortality lowered from 20% in Gr I to 9.4% in Gr II (p < 0.02); this was due to a significant reduction during the second period of bacterial (99/174 pat.--56.9% vs 82/221 pat.--37.1%), fungal (14 pat.--8% vs 7 pat.--3.2%) and viral (87 pat.--50% vs 49 pat.--22.2%) infections (p < 0.05) as well as of perioperative bleeding (92 pat.--52.9% vs 39 pat.--17.6%--p < 0.001). Late mortality remained almost identical throughout the two periods as lethal outcome was mainly caused by recurrent allograft diseases, cardiovascular and tumor problems. Morbidity in these series was important considering that almost, half of the patients had a technical complication, mostly related to bleeding (131 pat--33.2%) and biliary problems (66 pat--16.7%). Retransplantation index was 1.1 (54 pat.--14%). Early retransplantation mortality was 24%; it lowered, although not yet significantly, during the second period (8/25 pat.--32% vs. 5/29 pat.--17.2%). CONCLUSION: Despite a marked improvement of results, liver transplantation remains a major medical and surgical undertaking. Standardization of operative and perioperative care, less haemorraghic surgery and less aggressive immunosuppression are the keys for further improvement.

Calibration of seven ICU ventilators for mechanical ventilation with helium-oxygen mixtures.

The study evaluated seven intensive care unit (ICU) ventilators (Veolar FT, Galileo, Evita 2, Evita 4, Servo 900C, Servo 300, Nellcor Puritan Bennett 7200 Series) with helium-oxygen (HeO2), using a lung model, to develop correction factors for the safe use of HeO2. A 70:28 helium-O2 mixture (heliox) replaced air and combined with O2 (HeO2). Theoretical impact of HeO2 on inspiratory valves and gas mixing was computed. True fraction of inspired oxygen (FIO2del) was compared with fraction of inspired oxygen (FIO2) set on the ventilator (FIO2set). True tidal volume (VTdel) was compared with VT set on the ventilator (VTset) in volume control and with control VTdel at FIO2 1.0 in pressure control. FIO2del minimally exceeded FIO2set ( FIO2set by 125%). In volume control, with the Veolar FT, Galileo, Evita 2, and Servo 900C, VTdel > VTset, with the 7200 Series VTdel < VTset (linear relationship, magnitude of discrepancy inversely related to FIO2set). With the Evita 4, VTdel > VTset (nonlinear relationship), whereas with the Servo 300 VTdel = VTset. In pressure control, VTdel was identical to control measurements, except with the 7200 Series (ventilator malfunction). Correction factors were developed that can be applied to most ventilators.

Two-level non-invasive positive pressure ventilation in the initial treatment of acute respiratory failure in an emergency department.

There are few data on the use of two-level non-invasive positive pressure ventilation (two-level nIPPV) in the initial treatment of severe acute respiratory failure in emergency departments (ED). In a prospective, non-randomized, pilot study, we assessed (1) the feasability of this method in an ED, (2) its effect on clinical and laboratory data, and (3) its effect on the need of intubation and the final outcome of patients. During a 1-year period all eligible patients admitted for acute respiratory failure, with absence of improvement after periods of specific classic treatments, were included in the study. Each patient received a specific classic treatment and two-level nIPPV with a two-level positive pressure ventilator through a face mask. We recorded parameters on admission, after 15 and 45 minutes of nIPPV and at the end of nIPPV. Sixty-two patients were included: 29 with acute pulmonary oedema (APO), 16 with acute exacerbation of chronic obstructive pulmonary disease (COPD), four with asthma, and 13 with various diseases. In the APO-group, we observed a statistically significant improvement of respiratory and pulse rates, diastolic blood pressure, pH, PaCO2 and SaO2. In acute exacerbation of COPD, we observed only a statistical improvement of respiratory and pulse rates without any significant change of PaCO2 and pH. In the two other groups, there was a clinical, gasometric and haemodynamic improvement in all patients. Four patients were intubated and 10 died, but none in the ED or in the first 24 hours after hospital admission. We were able to institute two-level nIPPV for severe acute respiratory failure in an ED without complications. Its addition to the rest of classic specific treatment seems to bring about a rapid improvement of various clinical and laboratory parameters in most patients. We found no deleterious effect of nIPPV when implemented for short periods of time in the emergency department setting.

Significance of pathologic oxygen supply dependency in critically ill patients: comparison between measured and calculated methods.

OBJECTIVE: oxygen supply dependency at normal or high oxygen delivery rate has been increasingly proposed as a hallmark and a risk factor in critical illnesses. We hypothesized that as far as an adequate oxygen delivery is provided, oxygen consumption, when determined by indirect calorimetry, is not dependent on oxygen delivery in critically ill patients whereas calculated oxygen consumption is associated with artefactual correlation of oxygen consumption and delivery. DESIGN: oxygen delivery, oxygen consumption and their relationship were analyzed prospectively. Metabolic data gained from both measured and calculated methods were obtained simultaneously before and after volume loading. SETTING: the study was completed in the intensive care unit as part of the management protocol of the patients. PATIENTS: 32 consecutive patients entered the study and were divided into 3 groups according to a clinical condition known to favour oxygen supply dependency: sepsis syndrome, adult respiratory distress syndrome and acute primary liver failure. INTERVENTION: the rise in oxygen delivery was obtained by colloid infusion (oxygen flux test) performed in hemodynamically and metabolically stable patients. All were mechanically ventilated. No change in therapy was allowed during the test. MEASUREMENTS AND RESULTS: oxygen consumption was simultaneously evaluated by calculation (Fick Principle) and direct measurement using indirect calorimetry. Oxygen delivery was derived from the cardiac output (thermodilution) and arterial content of oxygen. Oxygen supply dependency was considered while observing an increase in oxygen delivery greater than 45 ml/min.m2. Irrespective of patient's clinical diagnosis and outcome, measured oxygen uptake remained unaltered by volume infusion whereas both oxygen delivery and calculated oxygen consumption increased significantly. Arterial lactate level > 2 mmol/l and measured oxygen extraction ratio > 25% failed to identify oxygen supply dependency when measured data were considered. CONCLUSION: analysis of oxygen uptake, when measured by indirect calorimetry, failed to substantiate oxygen supply dependency in the vast majority of the critically ill patients irrespective of diagnosis and outcome. Mathematical coupling of shared variables accounted for the correlation between oxygen delivery and calculated oxygen consumption.

Evaluation of oxygen uptake and delivery in critically ill patients: a statistical reappraisal.

OBJECTIVE: The evaluation of oxygen consumption (VO2) and oxygen delivery (DO2) has gained increasing importance in the monitoring of critically ill patients. They can be obtained from either direct measurements or by indirect calculations based on the Fick principle. However the choice between these two approaches remains controversial. The aim of the study was to investigate whether these 2 methods provide similar results, and if not, to define the best one in terms of reproducibility. DESIGN: Oxygen delivery and oxygen consumption were prospectively analyzed in 171 consecutive critically ill patients. Metabolic data were obtained simultaneously. SETTING: The study was completed in the intensive care unit as part of the management of the patients studied. PATIENTS: A first "group" of 279 evaluations was carried out in 73 consecutive critically ill patients. The results were subsequently validated by 423 observations performed in the 98 following patients. INTERVENTIONS: Before and during each evaluation, the patients were kept in stable hemodynamic and metabolic conditions. All were mechanically ventilated. MEASUREMENTS AND RESULTS: VO2 was evaluated by calculation (Fick principle) and direct measurement using indirect calorimetry. Cardiac output was both measured by the thermodilution technique and calculated (Fick principle) and the data were used for the evaluation of the directly measured and indirectly calculated DO2. For both VO2 and DO2 the agreement between direct and indirect evaluations was not satisfactory. Differences as great as 55 ml/min.m2 and 267 ml/min.m2 between simultaneously measured and calculated VO2 and DO2 respectively may be expected. Finally, the indirect calculated methods were less reproducible than the measured ones. These observations resulted mainly from the cumulative effects of the random errors in the metabolic data entering into the calculation of VO2 and DO2. CONCLUSIONS: Our data suggested that the indirect calculation (Fick equation) and the direct measurement (indirect calorimetry, thermodilution) of both VO2 and DO2 did not provide similar results. Direct measurements are more reproducible methods and must be preferred.

[Respiratory complications in severe acute pancreatitis]. / Les complications respiratoires de la pancréatite aiguë sévère.

The two basic mechanisms underlying most of the pleuropulmonary complications of severe acute pancreatitis include pulmonary atelectasis and alveolar flooding. Like in any abdominal catastrophe, pleural effusion and limited diaphragmatic excursion due to pain and intestinal atony are the main factors responsible for alveolar collapse and secondary infection. Physical therapy and needle pleural evacuation are the cornerstones of management. Owing to its pathophysiologic mechanisms adult respiratory distress syndrome is peculiar to acute pancreatitis. Alveolar capillary membrane injury is related to pancreatic necrosis, to its regional extent and to the subsequent over-amplification of the inflammatory reaction. Diversion of those potential mediators of the syndrome either surgically or by thoracic duct drainage is essential in order to improve survival in these patients.

[Complications and adverse effects of respiratory physiotherapy]. / Complications et effets néfastes de la kinésithérapie respiratoire de pratique courante.

Physiotherapy of the chest is used to mobilize manually respiratory secretions and to increase the amount of tracheobronchial mucus cleared from the respiratory tract. Today, the term chest physiotherapy has expanded to include a wide variety of manual techniques. Complications of chest physiotherapy have seldom been reported, but when they occurred they were mild or moderately severe. Adverse effects associated with this type of treatment were present in a small proportion of the patients studied and generally of modest clinical significance. Recognizing the nature of the potential for complications and adverse effects of chest physiotherapy enables therapeutists to modify the treatment so that it can be administered safely to critically and chronically ill patients.

Prospective evaluation of thoracic-duct drainage in the treatment of respiratory failure complicating severe acute pancreatitis.

Thoracic duct drainage (TDD) may be of value for removing toxic substances released by the inflamed pancreas and which are responsible for lung damage. We have prospectively assessed the efficacy of TDD in improving pulmonary gas exchange in 12 patients with severe acute pancreatitis (SAP) complicated by persistent respiratory failure despite standard conservative treatment including peritoneal dialysis in 8 patients. In group A were 6 patients (mean Ranson score = 7.3) with adult respiratory distress syndrome (ARDS) and in group B were 6 hypoxemic patients (mean Ranson score = 6.6) judged to be at risk of developing ARDS. The duration of TDD ranged from 3 to 10 days and the total amount of drained lymph (L) varied from 770 to 15,600 ml. Immunoreactive trypsin levels were significantly higher in L when compared to blood in both groups. Leukocyte myeloperoxidases in L (normal value less than than 332 +/- 82 ng/ml in plasma) were increased in 5 of 5 group A patients (830 +/- 317 ng/ml) and in 3 of 6 patients in group B (671 +/- 467 ng/ml). After TDD pulmonary gas exchange as measured by median PaO2/FiO2 (mmHg) improved from 148 +/- 60 to 285 +/- 42 in group A and from 192 +/- 37 to 330 +/- 42 in group B (p less than 0.05). All patients were weaned after ventilation for a mean of 8 days in group A and 4 days in group B. All patients survived apart from 1 group B patient who died of sepsis on day 34.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hepatic protein synthesis of the kallikrein-kininogen-kinin system]. / Synthèse protéique hépatique du système kallikréine-kininogènes-kinines.

Plasma prekallikrein and kininogens were assayed by specific enzymatic and immunological methods in cirrhotic patients with terminal liver failure and during oestrogenic impregnation. In cirrhotic patients plasma levels of these substances were significantly lowered and they correlated negatively with necrosis enzymes. A highly significant positive correlation was found between coagulation factor values and the levels of prekallikrein and kininogens. During oestrogenic impregnation the levels of the constituents of the kallikrein-kinin system were significantly increased when compared with reference values. These findings indicate that plasma concentrations of prekallikrein and kininogens are dependent upon liver synthesis capacity.

Design of an automated system for assessing metabolic function in mechanically ventilated patients.

This paper describes the design of a fully automated self calibrated measurement system which can be connected to any commercial ventilator. The machine measures the oxygen consumption and carbon dioxide production. The instrument is based on commercially available analysers. An inexpensive microprocessor performs the computations, displays the results and leads the calibration's and measure's procedures. The apparatus is presently tested in clinical practice.

The importance of the balloon reservoir volume of a CPAP system in reducing the work of breathing.

We have previously reported, that the work of breathing in spontaneously breathing patients on CPAP could be significantly reduced by increasing the volume of the balloon reservoir in the circuit of a CPAP system from 3 to 23 l. We now report a study designed to determine the optimum balloon reservoir volume for the minimization of the work of breathing. Twenty intubated, spontaneously breathing patients were connected to a CPAP system with interchangeable balloon reservoirs. In each patient the work of breathing was measured for reservoir volumes of 3, 6, 12, 18, and 24 l attached in random order, while the positive airway pressure was held constant at 10 cm H2O. The balloons were constructed of the same material and had similar compliance. Rebreathing was prevented with use of one-way valves. Significant (p less than 0.001) decreases in the work of breathing were found on increasing reservoir volumes from 3 to 6, 6 to 12, and 12 to 18 l. A less significant (p less than 0.01) decrease in the work of breathing was found between reservoirs of 18 and 24 l. Rebreathing did not occur with significantly (p less than 0.001) lower flow rates when large reservoirs were used. We conclude that a balloon reservoir of 18 l represents the best compromise between reduction in the work of breathing, utilization of low source flow, and convenience of clinical use.

[Effect of positive end expiratory pressure on the intrapulmonary shunt and the oxygen alveolo-arterial difference in adult acute respiratory distress]. / Effet de la pression positive en fin d'expiration (P.P.F.E.) sur le shunt intra-pulmonaire et sur la différence alvéolo-artérielle en oxygène [P(A-a)O2] dans la détresse respiratoire aiguë de l'adulte (D.R.A.A.).

The aim of this study was to analyse two groups of 10 patients with hypoxaemia. One group of patients had acute respiratory distress (A.R.D.A.) and the other group was hypoxaemic without acute adult respiratory distress. Both group of patients were ventilated artificially. The authors studied the effect of positive end expiratory pressure (PEEP) of 10 cm H2O on the intra-pulmonary shunt (Qs/Qt) and on the alveolar-arterial oxygen difference [P(A-a)O2]. The values for the shunt and for P(A-a)O2 are calculated at FiO2 of 0.4 and at a FiO2 of 1. The two groups are best distinguished by the difference between the shunt calculated at a FiO2 of 0.4 and at a FiO2 of 1, as the P(A-a)O2 is similar in both groups of patients and is not influenced by the PEEP, either in the A.R.D.A. or in the non-A.R.D.A. group. Without PEEP, A positive value is obtained for Qs-Qt in the A.R.D.A. group and a negative value is obtained in the non A.R.D.A. group. With PEEP of 10 cm, the shunt in patients with A.R.D.A. is greatly reduced and tends towards 0. In the non A.R.D.A. group of patients, the shunt does not vary with the PEEP and the difference remains negative.